Bioelectrogenic valorization of sugarcane bagasse: role of sewage addition and substrate pretreatment on power generation and substrate utilization
Naik S.P., Sarkar O., Undodi S.B., Hungund B.S., Mohanakrishna G.
Article, Cleaner Chemical Engineering, 2026, DOI Link
View abstract ⏷
Sugarcane bagasse (SCB), a recalcitrant lignocellulosic biomass, necessitates pretreatment to enhance the release of soluble organics for effective utilization. This study evaluated three pretreatment methods including alkaline (ALK), acid (AC) and hydrothermal (HTL), to extract sugars from SCB, subsequently evaluating these hydrolysates as substrates for bioelectricity generation in dual-chamber microbial fuel cells (MFCs). The study was conducted in two phases. Phase I utilized tap water to dilute the SCB hydrolysate, while Phase II replaced tap water with sewage. Results from Phase I indicated that ALK hydrolysate yielded the highest current density (414.00 mA/m²), followed by AC (339.00 mA/m²) and HTL (316.13 mA/m²). The corresponding chemical oxygen demand (COD) degradation rates were 57.60% for ALK, 46.67% for AC, and 37.30% for HTL hydrolysates. Phase II introduced sewage as a diluent, enhanced HTL hydrolysate performance (415.05 mA/m²; 53.50% COD removal) due to improved ionic conductivity and nutrient availability, which fostered better biofilm formation and electron transfer. The blending of AC and ALK hydrolysates facilitated in-situ pH neutralization, optimizing substrate complexity and buffering stability, culminating in a peak specific power yield of 1011 W/kgCOD. Cyclic voltammetry (CV) confirmed the development of an electroactive biofilm, indicating effective electron mediation. The study demonstrated that integrating optimized pretreatment with cost-effective methodologies, such as sewage repurposing can amplify energy recovery from SCB. This approach not only improves green energy production but also aligns with circular bioeconomy principles by valorizing agricultural residues and wastewater, presenting a scalable model for sustainable bioenergy systems.
Assessment of maize biomass digestibility: Roles of plant age and ensilage duration in biogas generation
Yadav N., Mohanakrishna G., Yadav J., Gandu R., Cahan R., Kumar S.S., Gandu B.
Article, Journal of Environmental Chemical Engineering, 2026, DOI Link
View abstract ⏷
Maize residue is considered a significant feedstock for biogas production, especially in regions where it is abundantly cultivated. Maize ensilage undergoes chemical changes during the silage period, which positively impact biogas yield. This study investigates the impact of maize plant age, ensilage period, digestion temperature, substrate characteristics, biogas production, and substrate degradation rate on anaerobic digestion efficiency. Two samples of maize, differing in age by 20 days (Maize silage90 days) and (Maize silage110 days), were ensiled for 100 days, in a batch mode under mesophilic (35°C) and thermophilic (55°C) conditions for 60 days for anaerobic digestion. The results revealed that under thermophilic conditions, biogas production from Maize silage90 was 8.86% higher than from Maize silage110, while under mesophilic conditions, Maize silage90 produced 22.86% more biogas than Maize silage110. The rate of COD degradation reached 95.99% (Maize silage90) and 93.75% (Maize silage110) under thermophilic conditions, while 93.75% (Maize silage90) and 88.94% (Maize silage110) under mesophilic conditions. These results indicate that the younger maize plant, combined with appropriate silage and temperature, can substantially enhance biogas yield and substrate degradation, providing a basis for optimizing AD performance.
Opportunities and challenges in utilizing carbon dioxide for value-added product generation via microbial electrosynthesis
Sivagami K., Gundlapalli M., Ganesan S., Gupta A.S., Lodha R., Bose S., Modestra J.A., Naik S.P., Kamble S.S., Basha S., Mohanakrishna G.
Article, Journal of Environmental Chemical Engineering, 2026, DOI Link
View abstract ⏷
As atmospheric CO₂ levels steadily rise, more effective carbon mitigation methods are needed to capture and convert CO₂. Microbial electrosynthesis (MES) is a hybrid electrochemical system in which electro-autotrophic microorganisms utilize electrons from a cathode to convert CO₂ into multi-carbon compounds. This review provides a mechanistic overview of current advancements in MES, emphasizing electron transfer pathways, biocathode architecture, CO₂ mass transfer limitations, and essential techno-economic factors. The inherently poor solubility of CO₂ in water is a primary rate-limiting factor, inhibiting carbon transfer to the Wood-Ljungdahl pathway. Strategies such as gas diffusion electrodes (GDE), biofilm-enhancing surfactants, and pH gradient operation have demonstrated significant improvement in CO2 availability and electron uptake. Advances in 3D nanostructure cathodes, including carbon nanotube-modified carbon felt and metal oxide composites, have achieved good production rates. Techno-economic analysis of acetate production via MES remain constrained by high capital expenditure (CAPEX ≈ 5059 €/tonne product) and the energy burden associated with multi-electron products such as ethanol. Integration of MES with CO₂-rich industrial exhaust streams, renewable power inputs, and metabolic engineering of an electrotrophic framework is expected to reduce operational cost and to improve product selectivity. The review highlights future priorities including advanced kinetic modeling, improved electrode-microbe coupling, and reactor designs that decouple mass transfer from bio-catalytic limitations to accelerate MES towards scalable, carbon-negative bio-manufacturing. Overall, this review delineates the scientific, engineering, and economic levels that must be optimized to transition MES from laboratory systems to commercially viable CO₂ valorization technologies.
Plant microbial fuel cells: A self-sustaining bioelectrochemical technology addressing sustainable development goals (SDGs) through bioelectricity production
Mohanakrishna G., Kudarimoti V.I., Kamble S.S., Naik S.P., Manisha S.
Review, Bioresource Technology, 2026, DOI Link
View abstract ⏷
Microbial fuel cells (MFCs) are regarded as an eco-friendly processes for bioelectricity generation and simultaneously treating wastewater. Nonetheless, MFCs have a significant limitation, constant supply of organics needed for microbial oxidation. In this context, plant microbial fuel cells (PMFCs) play an essential role in addressing this problem. Root exudates containing organic acids and sugars act as continuous electron donors that are metabolized by electrogenic microbes such as Geobacter to drive extracellular electron transfer, while nitrogen-transforming taxa such as Nitrosomonas link substrate oxidation with nitrogen cycling. The present review explores the multiple functions of PMFCs in the concurrent production of energy along with environmental restoration. It outlines the fundamental principles of PMFCs, emphasizing plant selection, microbial diversity, and electrode design as key factors affecting performance. The review also discussed about plant–microbe-electrode interactions in bioelectrogenesis, highlighting their potential in wastewater treatment, soil restoration, and precision agriculture. Furthermore, the review evaluates scalability challenges, including electrochemical limitations, design constraints, and field-level performance in pilot studies. By integrating renewable energy generation with ecosystem services, PMFCs align strongly with multiple United Nations Sustainable Development Goals (UN SDGs), particularly in clean energy, water purification, sustainable agriculture, and climate action. Future advancements in materials science, modular designs, and plant–microbe interactions are essential for translating PMFCs from laboratory prototypes into scalable, multifunctional systems for sustainable development.
Reduction of ammonia accumulation in anaerobic digestion of chicken manure by co-digestion and biogas-stripping
Naik S.P., Ponnusamy V.K., Kumar G., Yang C.-H., Tsai P.-C., Lin C.-Y., Mohanakrishna G., Lay C.-H.
Article, Bioresource Technology Reports, 2026, DOI Link
View abstract ⏷
Anaerobic digestion of chicken manure (CM) with high-solid content is typically constrained by ammonia nitrogen accumulation, which influences the microbial activity and methane yield (MY). A strategy of recycling stripped biogas and co-digestion was developed to reduce ammonia nitrogen accumulation and increase MY in a semi-continuously-stirred tank reactor (semi-CSTR) using CM as feedstock (total solid, 10%). The experimental results demonstrate that the stripping strategy can improve hydrolysis efficiency and reduce total ammonia nitrogen, free ammonia nitrogen, and total volatile fatty acids concentrations by 11%, 14%, and 20%, respectively. The soluble chemical oxygen demand (SCOD) removal efficiency and MY were improved by 23% and 37%, respectively compared to the no-stripping operation. In the integrated in-situ ammonia stripping with co-digestion study, with the addition of co-substrate (glucose, sunflower oil, and peptone), which was optimized by a central composite design (CCD) model, resulted in increased biogas yield and MY yield by 39% and 21% over the no-stripping method. The process also evidenced a lower TVFA concentration than the control, inferring the efficient conversion of metabolites towards methane production. This technology could be utilised in high-ammonia waste/wastewater digestion.
Editorial overview: Solar photocatalytic and photoelectrochemical hydrogen evolution using novel and effective materials
Clarizia L., Aminabhavi T.M., Mohanakrishna G., Keller N., Toe C.Y.
Editorial, Current Opinion in Chemical Engineering, 2025, DOI Link
Role of cathode materials and their advancement for sustainable hydrogen evolution reaction in microbial electrolysis cells
Naik S.P., Sarkar O., Gokuladoss V., Matsakas L., Mohanakrishna G.
Review, Current Opinion in Chemical Engineering, 2025, DOI Link
View abstract ⏷
Microbial electrolysis cells (MECs) offers a sustainable route for hydrogen production by decarbonizing global energy demands via transformation of biogenic waste/wastewater. Leveraging microbial metabolism, MECs contribute to the waste-to-energy nexus. The efficiency of MECs is significantly influenced by selection of electrode materials such as platinum, nickel, and stainless steel, which enhance the performance through their high surface area, chemical resilience, and effective hydrogen evolution reaction. MECs have been shown to generate 853 H2/m³/d using graphite brush (anode) and Pt-loaded carbon cloth (cathode). MECs were upgraded to 1000 l, having 24 modules with 144 electrode pairs. Key features of cathode materials and its advancements used in MECs are discussed in this review.
Advances in Microbial and Plant-Based Biopolymers: Synthesis and Applications in Next-Generation Materials
Drishya P.K., Reddy M.V., Mohanakrishna G., Sarkar O., Isha, Rohit M.V., Patel A., Chang Y.-C.
Review, Macromol, 2025, DOI Link
View abstract ⏷
Biopolymers are revolutionizing the materials landscape, driven by a growing demand for sustainable alternatives to traditional petroleum-based materials. Sourced from biological origins, these polymers are not only environment friendly but also present exciting solutions in healthcare, packaging, biosensors, high performance, and durable materials as alternatives to crude oil-based products. Recently, biopolymers derived from plants, such as lignin and cellulose, alongside those produced by bacteria, like polyhydroxyalkanoates (PHAs), have captured the spotlight, drawing significant interest for their industrial and eco-friendly applications. The growing interest in biopolymers stems from their potential as sustainable, renewable materials across diverse applications. This review provides an in-depth analysis of the current advancements in plant-based and bacterial biopolymers, covering aspects of bioproduction, downstream processing, and their integration into high-performance next-generation materials. Additionally, we delve into the technical challenges of cost-effectiveness, processing, and scalability, which are critical barriers to widespread adoption. By highlighting these issues, this review aims to equip researchers in the bio-based domain with a comprehensive understanding of how plant-based and bacterial biopolymers can serve as viable alternatives to petroleum-derived materials. Ultimately, we envision a transformative shift from a linear, fossil fuel-based economy to a circular, bio-based economy, fostering more sustainable and environmentally conscious material solutions using novel biopolymers aligning with the framework of the United Nations Sustainable Development Goals (SDGs), including clean water and sanitation (SDG 6), industry, innovation, and infrastructure (SDG 9), affordable and clean energy (SDG 7), sustainable cities and communities (SDG 11), responsible production and consumption (SDG 12), and climate action (SDG 13).
An insight on energy production using microbial fuel cell: A microbiological perspective and electron transfer improvement
Palanivel P.D., Naina Mohamed S., Mohanakrishna G., Ravinuthala S., Saravanan S.
Review, Journal of Chemical Technology and Biotechnology, 2025, DOI Link
View abstract ⏷
Microbial fuel cells (MFCs) are sustainable energy technologies that could resolve pollution challenges brought by various activities. It can meet energy demand by producing bioelectricity through catabolizing organic matter. Over the past two decades, research on many microbes have been used in MFCs, which intrigued researchers to explore the underlying electron transfer mechanism between microbe and anode. Electron transfer between electrode and microorganism occurs via different pathways: direct, indirect electron transfer and interspecies electron transfer. Shewanella and Geobacter are well-known for microbe–electrode and microbe–microbe electron transfer. This review provides an overview of the significant varieties of microbes utilized in MFCs for simultaneous bioelectricity generation and wastewater treatment. Mechanisms of different modes of electron transfer involved during the oxidation of organic wastes in the anode section of MFCs are highlighted. Furthermore, this review also details some of the techniques to promote extracellular electron transfer efficiency which is important for the enhanced performance of MFC in terms of power, current generation and wastewater remediation. A perspective of challenges to be addressed for the effective functioning of these technologies, opportunities for MFC systems to be scaled up and associated techno-economic analysis are discussed. © 2024 Society of Chemical Industry (SCI).
Microbial Electrosynthesis Systems for CO2 Sequestration and Biochemical Production
Naik S.P., Pengadeth D., Mohanakrishna G., Bodhe I., Reshma C., Velvizhi G.
Book chapter, Electro-Fermentation for Synthesis of Chemicals, Biochemicals and Biofuels, 2025, DOI Link
View abstract ⏷
Microbial electrosynthesis (MES) technology couples electrochemical reactions with microbial metabolism to generate organic molecules. MES technology offers a sustainable alternative to biochemical production by converting organic compounds and CO[[inf]]2[[/inf]] into value-added products such as organic acids, biogas, bioplastics, short-chain fatty acids (SCFAs), and alcohols. MES is a bioelectrochemical approach that enables the electron equivalents generating from the waste and wastewater for decarbonization and for valorization. Several factors such as the cathode, microorganisms, electrode materials, design, and membrane influence the productivity of the MES. At present, MES technology is at nascent stage, and the overall output from the process needs several folds of improvement for commercialization. This chapter discusses several aspects of MES technology along with valuable biochemical generation. The fundamental aspects of MES and the factors influencing the reactor performance are also discussed.
A comprehensive review of microbial electrolysis cells: Integrated for wastewater treatment and hydrogen generation
Swaminathan P., Ghosh A., Sunantha G., Sivagami K., Mohanakrishna G., Aishwarya S., Shah S., Sethumadhavan A., Ranjan P., Prajapat R.
Review, Process Safety and Environmental Protection, 2024, DOI Link
View abstract ⏷
The growing demand for sustainable energy sources has propelled research into innovative technologies that simultaneously address environmental challenges. Integrating microbial electrolysis cells (MECs) with wastewater management presents a promising avenue for sustainable hydrogen production. This innovative approach and synergistic capabilities of MECs, harness microbial activity to drive electrolysis and generate hydrogen gas. Wastewater, rich in organic matter, serves as a renewable and abundant substrate for microbial metabolism within the MEC, leading to efficient electron transfer and subsequent hydrogen production. Key factors influencing the performance of MECs in this context include electrode material, reactor configuration, and microbial community composition. This study highlights the significance of this integration in addressing the dual environmental challenges of wastewater treatment and clean energy production utilizing MECs allows for the efficient removal of organic contaminants from wastewater while also generating hydrogen, a clean, renewable energy source. Furthermore, the hydrogen produced can be utilized in various applications such as fuel cells, transportation, and industrial processes, contributing to decarbonization efforts and mitigating greenhouse gas emissions. This review explores the promising synergy between MECs and wastewater management for efficient hydrogen production. MECs harness the metabolic activities of microorganisms to facilitate the electrochemical conversion of organic matter in wastewater into hydrogen gas, presenting a dual benefit of clean energy generation and wastewater treatment.
Mixed culture biotechnology and its versatility in dark fermentative hydrogen production
Review, Bioresource Technology, 2024, DOI Link
View abstract ⏷
Over the years, extensive research has gone into fermentative hydrogen production using pure and mixed cultures from waste biomass with promising results. However, for up-scaling of hydrogen production mixed cultures are more appropriate to overcome the operational difficulties such as a metabolic shift in response to environmental stress, and the need for a sterile environment. Mixed culture biotechnology (MCB) is a robust and stable alternative with efficient waste and wastewater treatment capacity along with co-generation of biohydrogen and platform chemicals. Mixed culture being a diverse group of bacteria with complex metabolic functions would offer a better response to the environmental variations encountered during biohydrogen production. The development of defined mixed cultures with desired functions would help to understand the microbial community dynamics and the keystone species for improved hydrogen production. This review aims to offer an overview of the application of MCB for biohydrogen production.
Emerging technologies for the removal of pesticides from contaminated soils and their reuse in agriculture
Ambaye T.G., Hassani A., Vaccari M., Franzetti A., Prasad S., Formicola F., Rosatelli A., Rehman M.Z.U., Mohanakrishna G., Ganachari S.V., Aminabhavi T.M., Rtimi S.
Review, Chemosphere, 2024, DOI Link
View abstract ⏷
Pesticides are becoming more prevalent in agriculture to protect crops and increase crop yields. However, nearly all pesticides used for this purpose reach non-target crops and remain as residues for extended periods. Contamination of soil by widespread pesticide use, as well as its toxicity to humans and other living organisms, is a global concern. This has prompted us to find solutions and develop alternative remediation technologies for sustainable management. This article reviews recent technological developments for remediating pesticides from contaminated soil, focusing on the following major points: (1) The application of various pesticide types and their properties, the sources of pesticides related to soil pollution, their transport and distribution, their fate, the impact on soil and human health, and the extrinsic and intrinsic factors that affect the remediation process are the main points of focus. (2) Sustainable pesticide degradation mechanisms and various emerging nano- and bioelectrochemical soil remediation technologies. (3) The feasible and long-term sustainable research and development approaches that are required for on-site pesticide removal from soils, as well as prospects for applying them directly in agricultural fields. In this critical analysis, we found that bioremediation technology has the potential for up to 90% pesticide removal from the soil. The complete removal of pesticides through a single biological treatment approach is still a challenging task; however, the combination of electrochemical oxidation and bioelectrochemical system approaches can achieve the complete removal of pesticides from soil. Further research is required to remove pesticides directly from soils in agricultural fields on a large-scale.
Revisiting the role of algal biocathodes in microbial fuel cells for bioremediation and value-addition
Pengadeth D., Prakash Naik S., Sasi A., Mohanakrishna G.
Article, Chemical Engineering Journal, 2024, DOI Link
View abstract ⏷
Algal-microbial fuel cells (A-MFC) offers a sustainable solution for wastewater treatment and energy recovery. The performance of a typical MFC is affected by the oxidative-reductive reactions occurring in it. The cathodic reduction is facilitated by electron acceptors such as oxygen and ferricyanide. However, higher operational cost is incurred from their application. Algae owing to its phototrophic metabolism, oxygenates the cathode photosynthetically and acts as a mediator for cathodic electron transfer. Mixotrophic metabolism of algae enable their adaptation and growth in pollutant-rich toxic environments, making them suitable for wastewater treatment and remediation. A-MFCs enable the generation of algal biomass, a rich source of carbohydrates, lipids, proteins, pigments, and many more for commercial applications. Algal-based CO2 sequestration, nutrient and heavy metal removal via assimilation and carbon capture pathways make A-MFC systems a promising approach for bioenergy generation and wastewater remediation. Hence, this review offers an overview on the principles and applications of A-MFC and their relevance in developing a waste-centered-circular economy.
Sustainable duckweed biomass valorization for dark fermentative hydrogen production: Process evaluation under meso- and thermophilic operations
Article, Process Safety and Environmental Protection, 2024, DOI Link
View abstract ⏷
Aquatic plants are rich in biomass and contain good amounts of carbohydrates and proteins which are amenable for valorization to generate bioenergy. Duckweed is rich in proteins and carbohydrates that grow abundantly in contaminated waterbodies, which is now tested for as a substrate for biohydrogen production. Dark-fermentative hydrogen production was done by hydrothermal pretreatment of duckweed biomass under 15 lbs pressure, evaluated under three different operating temperatures that cover mesophilic (35 °C) and thermophilic conditions (50 and 55°C). The study resulted in the maximum hydrogen production rate of 0.97 mmol/day in batch culture (160 mL) from 55 °C that was found superior to 50 °C (0.84 mmol/day) and 35 °C (0.38 mmol/day) operations. From the 7 days of operation, under uncontrolled pH conditions, substrate (chemical oxygen demand, COD) utilization was 57.27 %, which is higher than in mesophilic conditions (50.67 %). Efficient hydrolysate conversion was noticed with thermophilic conditions, especially under operation at 55 °C (416 mL H2/g of biomass) than mesophilic conditions (144 mL H2/g of biomass) suggesting that duckweed can be dependable biomass for hydrogen production, and the dark-fermentation can be an appropriate solution of aquatic weed biomass management in a sustainable approach.
Enhancing anaerobic digestion of food waste for biogas production: Impact of graphene nanoparticles and multiwalled nanotubes on direct interspecies electron transfer mechanism
Yadav N., Mohanakrishna G., Gandu R., Cahan R., Gandu B.
Article, Process Safety and Environmental Protection, 2024, DOI Link
View abstract ⏷
The present research investigated the effect of two carbonaceous materials, multiwalled carbon nanotubes (MWCNTs), and graphene nanoparticles (GNPs), on biogas yield from food waste (FW) in an anaerobic digestion system for 30 days. Lab scale investigations were conducted in batch mode in 250 mL glass reactor bottles and the findings were compared to the control reactor. The performance of the experimental procedure was assessed in terms of biogas output and organic matter reduction. The addition of 100 mg/L multiwalled carbon nanotubes and 100 mg/L GNPs increased the cumulative biogas production (33.55 % and 81.16 %, respectively) while decreasing the total solid content (about 25.95 % and 24.95 %, respectively). However, increasing the concentration of both carbon nanomaterials from 100 mg/L to 500 mg/L reduced the total biogas production compared to the control, which can be attributed to cytotoxic effects. A microbial diversity study was performed using 16S amplicon sequencing to understand the changes occurring in the microbial ecology. The predominant phyla found during diversity analysis were Firmicutes, Proteobacteria, Actinobacteriota, and Bacteroidota. Finally, addition of carbonaceous nanomaterials to the anaerobic reactors favours organic matter degradation through the DIET mechanism. It improves the biogas production kinetics and productivity during the anaerobic digestion of FW up to a certain dose.
Biobased heterogeneous renewable catalysts: Production technologies, innovations, biodiesel applications and circular bioeconomy
Sarangi P.K., Singh A.K., Ganachari S.V., Pengadeth D., Mohanakrishna G., Aminabhavi T.M.
Review, Environmental Research, 2024, DOI Link
View abstract ⏷
The growing population and waste biomass accumulation are leading to increased environmental pollution and climate change. Waste biomass comprising of nutrient rich components has promising potential to produce value-added products for sustainable environmental solutions. This review explores the critical role of bio-based heterogeneous catalysts in enabling sustainable waste biomass utilization. In industrial chemical transformations, over 95% involve catalysts, with more than 90% being heterogeneous systems, prized for their robustness, ease of product separation, and reusability. Bio-based heterogeneous catalysts address the pressing need for sustainable waste biomass management, allowing the conversion of diverse waste biomasses into biodiesel as valuable products. Research on these catalysts, particularly for biodiesel production, has shown yields exceeding 90% with enhanced catalyst reusability. This surge in research is evident from the increasing number of published articles, notably in 2022 and 2023, highlighting growing interest and importance in the scientific community. The synthesis of these catalysts is examined, including novel approaches and techniques to enhance their efficiency, selectivity, and stability. The challenges with their feasible solutions of heterogeneous catalysts in catalyst-based processes are addressed. Altogether, this review underscores the immense potential of bio-based heterogeneous catalysts in sustainable waste biomass utilization, aligning with resource efficiency and environmental conservation goals while offering distinct insights and perspectives on the latest innovations in the field.
Value addition through biohydrogen production and integrated processes from hydrothermal pretreatment of lignocellulosic biomass
Article, Bioresource Technology, 2023, DOI Link
View abstract ⏷
Bioenergy production is the most sought-after topics at the crunch of energy demand, climate change and waste generation. In view of this, lignocellulosic biomass (LCB) rich in complex organic content has the potential to produce bioenergy in several forms following the pretreatment. Hydrothermal pretreatment that employs high temperatures and pressures is gaining momentum for organics recovery from LCB which can attain value-addition. Diverse bioprocesses such as dark fermentation, anaerobic digestion etc. can be utilized following the pretreatment of LCB which can result in biohydrogen and biomethane production. Besides, integration approaches for LCB utilization that enhance process efficiency and additional products such as biohythane production as well as application of solid residue obtained after LCB pretreatment were discussed. Importance of hydrothermal pretreatment as one of the suitable strategies for LCB utilization is emphasized suggesting its future potential in large scale energy recovery.
Sustainable bioelectrochemical systems for bioenergy generation via waste treatment from petroleum industries
Kondaveeti S., Govindarajan D., Mohanakrishna G., Thatikayala D., Abu-Reesh I.M., Min B., Nambi I.M., Al-Raoush R.I., Aminabhavi T.M.
Review, Fuel, 2023, DOI Link
View abstract ⏷
Petroleum industries are large water consumers and generate a lot of wastewater at various stages of industrial operations. Wastewater from the petroleum industries contain recalcitrant pollutants such as hydrocarbons that are present in high concentrations, dissolved solids and sulfur compounds that can pose potential environmental threat. Bioelectrochemical systems (BESs) are known to be sustainable processes to treat the various kinds of wastewaters such as petroleum wastewater, while simultaneously generating the bioelectricity and value-added chemicals. This review focuses on various applications of BESs such as microbial fuel cells (MFC), microbial electrolysis cells (MEC), and microbial desalination cells (MDC) using diverse types of wastewaters (petroleum sludge, produced water, formation water, and petroleum refinery wastewater) from the petroleum industries. Overall, a hybrid type BES with hydrocarbon wastewater achieved a 98% of columbic efficiency, 96.5% of chemical oxygen demand (COD), 99% of phenanthrene, 94% of pyrene and 80% of TDS removal which are superior to single and dual chamber BES performances. The review also compares the existing biological processes with BESs in terms of the treatment of hydrocarbons and process sustainability. Treatment efficiency of petroleum wastes via the BES can be further improved by integrating the biological and electrochemical processes to develop a sustainable approach to bio-refinery route.
Sustainable production of biosurfactants via valorisation of industrial wastes as alternate feedstocks
Carolin C F., Senthil Kumar P., Mohanakrishna G., Hemavathy R.V., Rangasamy G., M Aminabhavi T.
Article, Chemosphere, 2023, DOI Link
View abstract ⏷
Globally, the rapid increase in the human population has given rise to a variety of industries, which have produced a variety of wastes. Due to their detrimental effects on both human and environmental health, pollutants from industry have taken centre stage among the various types of waste produced. The amount of waste produced has therefore increased the demand for effective waste management. In order to create valuable chemicals for sustainable waste management, trash must be viewed as valuable addition. One of the most environmentally beneficial and sustainable choices is to use garbage to make biosurfactants. The utilization of waste in the production of biosurfactant provides lower processing costs, higher availability of feedstock and environmental friendly product along with its characteristics. The current review focuses on the use of industrial wastes in the creation of sustainable biosurfactants and discusses how biosurfactants are categorized. Waste generation in the fruit industry, agro-based industries, as well as sugar-industry and dairy-based industries is documented. Each waste and wastewater are listed along with its benefits and drawbacks. This review places a strong emphasis on waste management, which has important implications for the bioeconomy. It also offers the most recent scientific literature on industrial waste, including information on the role of renewable feedstock for the production of biosurfactants, as well as the difficulties and unmet research needs in this area.
Valorization of micro-algae biomass for the development of green biorefinery: Perspectives on techno-economic analysis and the way towards sustainability
Saravanan A., Senthil Kumar P., Badawi M., Mohanakrishna G., Aminabhavi T.M.
Article, Chemical Engineering Journal, 2023, DOI Link
View abstract ⏷
The consumption of fossil fuel sources and in particular, the emerging lethal issues connected with global warming triggered by consumption of petroleum products have set off dynamic research in finding alternate and eco-friendly energy sources. In this regard, algae are viewed as the most versatile feedstock materials for the development of sustainable power sources and producing green biorefinery. Algae have a high obsession pace of atmospheric carbon dioxide which supports to rapid development rate with high efficiency per unit area as sustainable algal biomass. This review presents an extensive details of the sustainable process of microalgae biomass in biorefinery applications. The pre-treatment strategies and bioconversion of algae biomass into biofuel are also highlighted in this review. A detailed survey was encompassed on different microalgae harvesting techniques, transesterification process and biofuel production. This review further focuses on metabolic engineering methodologies accessible for altering the pathway in algal species for expanding biomass and biofuel production. The present article put forth the modern biotechnology tool to produce biofuel from microalgae biomass. At last, techno-economic analysis, manageability, difficulties and future points of view in algal development and pretreatment process were examined exhaustively for making an environmentally viable algal biofuel.
Electrochemical-based approaches for the treatment of forever chemicals: Removal of perfluoroalkyl and polyfluoroalkyl substances (PFAS) from wastewater
Sivagami K., Sharma P., Karim A.V., Mohanakrishna G., Karthika S., Divyapriya G., Saravanathamizhan R., Kumar A.N.
Review, Science of the Total Environment, 2023, DOI Link
View abstract ⏷
Electrochemical based approaches for the treatment of recalcitrant water borne pollutants are known to exhibit superior function in terms of efficiency and rate of treatment. Considering the stability of Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are designated as forever chemicals, which generating from various industrial activities. PFAS are contaminating the environment in small concentrations, yet exhibit severe environmental and health impacts. Electro-oxidation (EO) is a recent development that treats PFAS, in which different reactive species generates at anode due to oxidative reaction and reductive reactions at the cathode. Compared to water and wastewater treatment methods those being implemented, electrochemical approaches demonstrate superior function against PFAS. EO completely mineralizes (almost 100 %) non-biodegradable organic matter and eliminate some of the inorganic species, which proven as a robust and versatile technology. Electrode materials, electrolyte concentration pH and the current density applying for electrochemical processes determine the treatment efficiency. EO along with electrocoagulation (EC) treats PFAS along with other pollutants from variety of industries showed highest degradation of 7.69 mmol/g of PFAS. Integrated approach with other processes was found to exhibit improved efficiency in treating PFAS using several electrodes boron-doped diamond (BDD), zinc, titanium and lead based with efficiency the range of 64 to 97 %.
Photocatalytic degradation of four emerging antibiotic contaminants and toxicity assessment in wastewater: A comprehensive study
Sharma M., Rajput D., Kumar V., Jatain I., Aminabhavi T.M., Mohanakrishna G., Kumar R., Dubey K.K.
Article, Environmental Research, 2023, DOI Link
View abstract ⏷
Excessive usage and unrestricted discharge of antibiotics in the environment lead to their accumulation in the ecosystem due to their highly stable and non-biodegradation nature. Photodegradation of four most consumed antibiotics such as amoxicillin, azithromycin, cefixime, and ciprofloxacin were studied using Cu2O–TiO2 nanotubes. Cytotoxicity evaluation of the native and transformed products was conducted on the RAW 264.7 cell lines. Photocatalyst loading (0.1–2.0 g/L), pH (5, 7 and 9), initial antibiotic load (50–1000 μg/mL) and cuprous oxide percentage (5, 10 and 20) were optimized for efficient photodegradation of antibiotics. Quenching experiments to evaluate the mechanism of photodegradation with hydroxyl and superoxide radicals were found the most reactive species of the selected antibiotics. Complete degradation of selected antibiotics was achieved in 90 min with 1.5 g/L of 10% Cu2O–TiO2 nanotubes with initial antibiotic concentration (100 μg/mL) at neutral pH of water matrix. The photocatalyst showed high chemical stability and reusability up to five consecutive cycles. Zeta potential studies confirms the high stability and activity of 10% C-TAC (Cuprous oxide doped Titanium dioxide nanotubes for Applied Catalysis) in the tested pH conditions. Photoluminescence and Electrochemical Impedance Spectroscopy data speculates that 10% C-TAC photocatalyst have efficient photoexcitation in the visible light for photodegradation of antibiotics samples. Inhibitory concentration (IC50) interpretation from the toxicity analysis of native antibiotics concluded that ciprofloxacin was the most toxic antibiotic among the selected antibiotics. Cytotoxicity percentage of transformed products showed r: −0.985, p: 0.01 (negative correlation) with the degradation percentage revealing the efficient degradation of selected antibiotics with no toxic by-products.
Dark fermentative hydrogen production: Potential of food waste as future energy needs
Mohanakrishna G., Sneha N.P., Rafi S.M., Sarkar O.
Article, Science of the Total Environment, 2023, DOI Link
View abstract ⏷
Globally, food waste (FW) is found to be one of the major constituents creating several hurdles in waste management. On the other hand, the energy crisis is increasing and the limited fossil fuel resources available are not sufficient for energy needed for emerging population. In this context, biohydrogen production approach through valorization of FW is emerging as one of the sustainable and eco-friendly options. The present review explores FW sources, characteristics, and dark fermentative production of hydrogen along with its efficiency. FW are highly biodegradable and rich in carbohydrates which can be efficiently utilized by anaerobic bacteria. Based on the composition of FW, several pretreatment methods can be adapted to improve the bioavailability of the organics. By-products of dark fermentation are organic acids that can be integrated with several secondary bioprocesses. The versatility of secondary products is ranging from energy generation to biochemicals production. Integrated approaches facilitate in enhanced energy harvesting along with extended wastewater treatment. The review also discusses various parameters like pH, temperature, hydraulic retention time and nutrient supplementation to enhance the process efficiency of biohydrogen production. The application of solid-state fermentation (SSF) in dark fermentation improves the process efficiency. Dark fermentation as the key process for valorization and additional energy generating process can make FW the most suitable substrate for circular economy and waste based biorefinery.
Applications of autotrophic ammonia oxidizers in bio-geochemical cycles
Rajput D., Baldia A., Kumar A., Kumar V., Mohanakrishna G., Kumar Dubey K.
Article, Chemical Engineering Journal, 2023, DOI Link
View abstract ⏷
Nitrogen is essential for life and to produce food. Still, nitrogen loss of the unused nitrogen in wastewater, air, freshwater, and oceans has caused nitrogen pollution, which impacts the environment and leads to eutrophication, climate change, biodiversity loss, and ozone depletion. It also causing cardio respiratory issues in humans. Anthropogenic activities such as food processing, fertilizer production, mining, and other impacting the global biogeochemical nitrogen cycle. Autotrophic ammonia-oxidizing microbial moieties such as ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and anaerobic ammonia-oxidizing bacteria (AnAOB) are being extensively used to remove nitrogen (present in the ammonia and ammonium forms). The conventional nitrogen removal process, “nitrification and denitrification,” has been highly used in wastewater treatment plants by employing a various bacterial communities. Since it required high organic compounds and an energy-intensive process, new strategies were being developed to reduce carbon footprint. “Anammox,” “Feammox,” and “Comammox” are a few processes that utilize specific bacterial moieties and do not require organic carbon. Among these, Anammox has become the most potential nitrogen removal system. In various studies, the combined Anammox and partial nitrification (PN/A) have shown the maximum nitrogen removal rate (NRR). This review discusses the applications of autotrophic ammonia oxidizers in agriculture, wastewater treatment plants, and engineered ecosystems. We have also addressed various stress impacts on ammonia oxidizers.
Electrochemical-based approaches for the treatment of pharmaceuticals and personal care products in wastewater
Mosur Nagarajan A., Subramanian A., Prasad Gobinathan K., Mohanakrishna G., Sivagami K.
Article, Journal of Environmental Management, 2023, DOI Link
View abstract ⏷
In recent times, emerging contaminants (ECs) like pharmaceuticals and personal care products (PPCPs) in water and wastewater have become a major concern in the environment. Electrochemical treatment technologies proved to be more efficient to degrade or remove PPCPs present in the wastewater. Electrochemical treatment technologies have been the subject of intense research for the past few years. Attention has been given to electro-oxidation and electro-coagulation by industries and researchers, indicating their potential to remediate PPCPs and mineralization of organic and inorganic contaminants present in wastewater. However, difficulties arise in the successful operation of scaled-up systems. Hence, researchers have identified the need to integrate electrochemical technology with other treatment technologies, particularly advanced oxidation processes (AOPs). Integration of technologies addresses the limitation of indiviual technologies. The major drawbacks like formation of undesired or toxic intermediates, s, energy expenses, and process efficacy influenced by the type of wastewater etc., can be reduced in the combined processes. The review discusses the integration of electrochemical technology with various AOPs, like photo-Fenton, ozonation, UV/H2O2, O3/UV/H2O2, etc., as an efficient way to generate powerful radicals and augment the degradation of organic and inorganic pollutants. The processes are targeted for PPCPs such as ibuprofen, paracetamol, polyparaben and carbamezapine. The discussion concerns itself with the various advantages/disadvantages, reaction mechanisms, factors involved, and cost estimation of the individual and integrated technologies. The synergistic effect of the integrated technology is discussed in detail and remarks concerning the prospects subject to the investigation are also stated.
Lignocellulosic biomass-based glycoconjugates for diverse biotechnological applications
Rodrigues Reis C.E., Milessi T.S., Ramos M.D.N., Singh A.K., Mohanakrishna G., Aminabhavi T.M., Kumar P.S., Chandel A.K.
Review, Biotechnology Advances, 2023, DOI Link
View abstract ⏷
Glycoconjugates are the ubiquitous components of mammalian cells, mainly synthesized by covalent bonds of carbohydrates to other biomolecules such as proteins and lipids, with a wide range of potential applications in novel vaccines, therapeutic peptides and antibodies (Ab). Considering the emerging developments in glycoscience, renewable production of glycoconjugates is of importance and lignocellulosic biomass (LCB) is a potential source of carbohydrates to produce synthetic glycoconjugates in a sustainable pathway. In this review, recent advances in glycobiology aiming on glycoconjugates production is presented together with the recent and cutting-edge advances in the therapeutic properties and application of glycoconjugates, including therapeutic glycoproteins, glycosaminoglycans (GAGs), and nutraceuticals, emphasizing the integral role of glycosylation in their function and efficacy. Special emphasis is given towards the potential exploration of carbon neutral feedstocks, in which LCB has an emerging role. Techniques for extraction and recovery of mono- and oligosaccharides from LCB are critically discussed and influence of the heterogeneous nature of the feedstocks and different methods for recovery of these sugars in the development of the customized glycoconjugates is explored. Although reports on the use of LCB for the production of glycoconjugates are scarce, this review sets clear that the potential of LCB as a source for the production of valuable glycoconjugates cannot be underestimated and encourages that future research should focus on refining the existing methodologies and exploring new approaches to fully realize the potential of LCB in glycoconjugate production.
Emerging trends and advances in valorization of lignocellulosic biomass to biofuels
Velvizhi G., Jacqueline P.J., Shetti N.P., K L., Mohanakrishna G., Aminabhavi T.M.
Review, Journal of Environmental Management, 2023, DOI Link
View abstract ⏷
Sustainable technologies pave the way to address future energy demand by converting lignocellulosic biomass into fuels, carbon-neutral materials, and chemicals which might replace fossil fuels. Thermochemical and biochemical technologies are conventional methods that convert biomass into value-added products. To enhance biofuel production, the existing technologies should be upgraded using advanced processes. In this regard, the present review explores the advanced technologies of thermochemical processes such as plasma technology, hydrothermal treatment, microwave-based processing, microbial-catalyzed electrochemical systems, etc. Advanced biochemical technologies such as synthetic metabolic engineering and genomic engineering have led to the development of an effective strategy to produce biofuels. The microwave-plasma-based technique increases the biofuel conversion efficiency by 97% and the genetic engineering strains increase the sugar production by 40%, inferring that the advanced technologies enhances the efficiency. So understanding these processes leads to low-carbon technologies which can solve the global issues on energy security, the greenhouse gases emission, and global warming.
Production of bioactive phenolic compounds from agricultural by-products towards bioeconomic perspectives
Sarangi P.K., Vivekanand V., Mohanakrishna G., Pattnaik B., Muddapur U.M., Aminabhavi T.M.
Review, Journal of Cleaner Production, 2023, DOI Link
View abstract ⏷
The massive utilization of fossil resources to produce synthetic chemicals/products is resulting in several environmental issues. A circular sustainable bioeconomy model can ameliorate such environmental problems through the valorization of renewable resources such as agricultural waste biomass. Waste biomass from agricultural sources presents a promising potential to manufacture sustainable chemicals and fuels. Contemporary agro-industrial processes generate a huge quantity of diverse by-products, which are gathered sometimes at landfill sites or open farming fields that result in environmental distress including air, soil, and water pollution. Organic content present in the waste residues is the profuse source of bioactive greener phenolics compounds that can exhibit anti-inflammatory, antioxidant, cardio-protective, anticancer potential and several other important applications. The production of useful phenolics can be realized through recycling into growing economy as fresh resources. In this perspective, by-products and wastes generated from agricultural and food sectors can be considered as promising resources for circular bioeconomy. The review covers consolidated aspects pertaining to reclamation of phenolics from agricultural residues and it emphasizes sustainable and benign extraction technologies.
Application of bioelectrochemical systems to regulate and accelerate the anaerobic digestion processes
Nagendranatha Reddy C., Kondaveeti S., Mohanakrishna G., Min B.
Article, Chemosphere, 2022, DOI Link
View abstract ⏷
Anaerobic digestion (AD) serves as a potential bioconversion process to treat various organic wastes/wastewaters, including sewage sludge, and generate renewable green energy. Despite its efficiency, AD has several limitations that need to be overcome to achieve maximum energy recovery from organic materials while regulating inhibitory substances. Hence, bioelectrochemical systems (BESs) have been widely investigated to treat inhibitory compounds including ammonia in AD processes and improve the AD operational efficiency, stability, and economic viability with various integrations. The BES operations as a pretreatment process, inside AD or after the AD process aids in the upgradation of biogas (CO2 to methane) and residual volatile fatty acids (VFAs) to valuable chemicals and fuels (alcohols) and even directly to electricity generation. This review presents a comprehensive summary of BES technologies and operations for overcoming the limitations of AD in lab-scale applications and suggests upscaling and future opportunities for BES-AD systems.
Impact of electric potential and magnetic fields on power generation in microbial fuel cells treating food waste leachate
Gunda M., Kondaveeti S., Krishna Bharat L., Modigunta J.K.R., Abu-Reesh I.M., Al-Raoush R.I.
Article, Journal of Water Process Engineering, 2021, DOI Link
View abstract ⏷
Sustainable bioelectrogenesis was evaluated by oxidizing the organics of food waste leachate (FWL) under the influence of magnetic field (MF) and short term applied voltage (electric potential, EP). Adaptation of MF (20–220 m T) and EP (100−500 mV) had enhanced the performance of MFC in terms of power generation and reduction of organic in FWL. The best performance of MFC was noted with a MF at 220 m T and EP at 500 mV. MFC under the influence of applied EP (100−500 mV), the power generation was increased from 493 mW/m2 to 832 mW/m2. During this operation, the chemical oxygen demand removal (CODr) was also increased from 51.3 % to 80.4 %. Whereas the control MFC (MFC-C) had exhibited a maximum power generation and CODr of 224 mW/m2 and 36.3 %, respectively. MFC with MF has showed an increase in power density from 480 mW/m2 to 811 mW/m2. MFCs at 220 m T and 500 mV has exhibited, 262 % and 271 % increase in power density over control, respectively. Adaptation of MFC under the EP and MF were found to be beneficial in treating FWL which has high strength organic content.
Integrating electrochemical and bioelectrochemical systems for energetically sustainable treatment of produced water
Article, Fuel, 2021, DOI Link
View abstract ⏷
Pollutants present in produced water (PW) are recalcitrant in nature and difficult to treat with simple processes. Energetically sustainable and novel approach was developed by integrating electrochemical cell (EC, Primary process) and microbial fuel cell (MFC, secondary process) to treat PW. Five different current densities (26, 36, 48, 59 and 71 mA/cm2) were applied in independent EC experiments (4 h). The effluents from each EC operation was further treated by MFC (10 h), to harness bioelectricity. Operational variations were maintained only in EC phase and kept MFC phase similar. This integration revealed that the extent of bioelectricity generation depends on the electrochemical oxidation of EC process. Overall, maximum power generation of 2.74 mW was registered with EC-effluent from 48 mA/cm2. The integration also showed highest TPH removal efficiency of 89% (EC, 305 mg/L; MFC, 317 mg/L) and COD removal efficiency of 89.6% (EC, 2160 mg/L; MFC, 1960 mg/L) at 71 mA/cm2. Other pollutants of PW, such as sulfates and TDS also removed efficiently (sulfates, 42.6%; TDS, 34.3%). Cyclic voltammetric (CV) and derivative analysis of the anodic biofilm were correlated well with MFC performance during different EC-effluents as substrate, indicating NADH involvement in bioanodic electron transfer. The balance between energy utilization in EC and bioelectricity generation by MFC was depicted that the integration of EC and MFC results in net positive energy. Maximum net power generation of 565 mWh (350 mL of anode volume) was resulted by integration. This integration depicts its potential to generate 1615 Whm−3 from the treatment of 1KL PW.
Review on the production of medium and small chain fatty acids through waste valorization and CO2 fixation
Venkateswar Reddy M., Kumar G., Mohanakrishna G., Shobana S., Al-Raoush R.I.
Article, Bioresource Technology, 2020, DOI Link
View abstract ⏷
The developing approaches in the recovery of resources from biowastes for the production of renewable value-added products and fuels, using microbial cultures as bio-catalyst have now became promising aspect. In the path of anaerobic digestion, the microorganisms are assisting transformation of a complex organic feedstock/waste to biomass and biogas. This potentiality consequently leads to the production of intermediate precursors of renewable value-added products. Particularly, a set of anaerobic pathways in the fermentation process, yields small-chain fatty acids (SCFA), and medium-chain fatty acids (MCFA) via chain elongation pathways from waste valorization and CO2 fixation. This review focuses on the production of SCFA and MCFA from CO2, synthetic substrates and waste materials. Moreover, the review introduces the metabolic engineering of Escherichia coli and Saccharomyces cerevisiae for SCFAs/MCFAs production. Furtherly, it concludes that future critical research might target progress of this promising approach as a valorization of complex organic wastes.
Microbial electrosynthesis feasibility evaluation at high bicarbonate concentrations with enriched homoacetogenic biocathode
Mohanakrishna G., Abu Reesh I.M., Vanbroekhoven K., Pant D.
Article, Science of the Total Environment, 2020, DOI Link
View abstract ⏷
An enrichment methodology was developed for a homoacetogenic biocathode that is able to function at high concentrations of bicarbonates for the microbial electrosynthesis (MES) of acetate from carbon dioxide. The study was performed in two stages; enrichment of consortia in serum bottles and the development of a biocathode in MES. A homoacetogenic consortium was sequentially grown under increasing concentrations of bicarbonate, in serum bottles, at room temperature. The acetate production rate was found to increase with the increase in the bicarbonate concentration and evidenced a maximum production rate of 260 mg/L d−1 (15 g HCO3 −/L). On the contrary, carbon conversion efficiency decreased with the increase in the bicarbonate concentration, which evidenced a maximum at 2.5 g HCO3 −/L (90.16%). Following a further increase in the bicarbonate concentration up to 20 g HCO3 −/L, a visible inhibition was registered with respect to the acetate production rate and the carbon conversion efficiency. Well adapted biomass from 15 g HCO3 −/L was used to develop biocathodic catalyst for MES. An effective biocathode was developed after 4 cycles of operation, during which acetate production was improved gradually, evidencing a maximum production rate of 24.53 mg acetate L−1 d−1 (carbon conversion efficiency, 47.72%). Compared to the enrichment stage, the carbon conversion efficiency and the rate of acetate production in MES were found to be low. The production of acetate induced a change in the catholyte pH, from neutral conditions towards acidic conditions.
Advanced Routes of Biological and Bio-electrocatalytic Carbon Dioxide (CO2) Mitigation Toward Carbon Neutrality
Kondaveeti S., Abu-Reesh I.M., Mohanakrishna G., Bulut M., Pant D.
Review, Frontiers in Energy Research, 2020, DOI Link
View abstract ⏷
Changes in the environment due to multiple factors, such as combustion of fossil fuels, heating, transportation, deforestation, etc., have led to more greenhouse gases in the atmosphere, which eventually led to a rise in global temperatures. Carbon dioxide (CO2) is the major factor for the rapid rise in global temperature. One of the most encouraging technological advances to address global warming is to transform CO2 into value-added commodities that offer a win–win strategy. In this regard, intensive research has been pursued around the world for development of feasible systems in product recovery or product synthesis from CO2-rich industrial emissions. We envision that the biological CO2 reduction or conversion process can be beneficial for developing carbon-neutral technologies. The integration of CO2-emitting industrial technologies with CO2-converting biological systems can be helpful in achieving sustainable value-added products with no or minimal loss of energy and materials that are assuring for improved economics. The CO2-converting bioprocesses can be directly integrated with the processes emitting a high amount of CO2. This symbiotic integration can make the whole process carbon neutral. Herein, this review highlights an insight on research activities of biological CO2 mitigation using photo catalysts (algae and photo bacteria), an anaerobic biocatalyst (bacteria), gas fermentation, and an enzymatic catalyst. Perspectives and challenges of these technologies are discussed.
Sewage enhanced bioelectrochemical degradation of petroleum hydrocarbons in soil environment through bioelectro-stimulation
Article, Biotechnology Reports, 2020, DOI Link
View abstract ⏷
The impact of readily biodegradable substrates (sewage and acetate) in bioelectroremediation of hydrocarbons (PW) was evaluated in a bench-scale soil-based hybrid bioelectrochemical system. Addition of bioelectro-stimulants evidenced efficient degradation than control operation. Acetate and sewage were exhibited power density of 1126 mW/m2 and 1145 mW/m2, respectively, which is almost 15 % higher than control (without stimulant, 974 mW/m2). Increased electrochemical activity was correlated well with total petroleum hydrocarbons (TPH) degradation through addition of acetate (TPHR, 525 mg/L, 67.4 %) and sewage (TPHR, 560 mg/L,71.8 %) compared to the control operation (TPHR, 503 mg/L, 64.5 %). Similarly, chemical oxygen demand (COD) reduction was also enhanced from 69.0 % (control) to 72.1 % and 74.6 % with acetate and sewage, respectively. Sewage and acetate also showed a positive role in sulfates removal, which enhanced from 56.0 % (control) to 62.9 % (acetate) and 72.6 % (sewage). This study signifies the superior function of sewage as biostimulant compared to acetate for the bioelectroremediation of hydrocarbons in contaminated soils.
Biorefinery perspectives of microbial electrolysis cells (MECs) for hydrogen and valuable chemicals production through wastewater treatment
Kadier A., Jain P., Lai B., Kalil M.S., Kondaveeti S., Alabbosh K.F.S., Abu-Reesh I.M., Mohanakrishna G.
Review, Biofuel Research Journal, 2020, DOI Link
View abstract ⏷
The degradation of waste organics through microbial electrolysis cell (MEC) generates hydrogen (H2) gas in an economically efficient way. MEC is known as the advanced concept of the microbial fuel cell (MFC) but requires a minor amount of supplementary electrical energy to produce H2 in the cathode microenvironment. Different bio/processes could be integrated to generate additional energy from the substrate used in MECs, which would make the whole process more sustainable. On the other hand, the energy required to drive the MEC mechanism could be harvested from renewable energy sources. These integrations could advance the efficiency and economic feasibility of the whole process. The present review critically discusses all the integrations investigated to date with MECs such as MFCs, anaerobic digestion, microbial desalination cells, membrane bioreactors, solar energy harvesting systems, etc. Energy generating non-biological and eco-friendly processes (such as dye-sensitized solar cells and thermoelectric microconverters) which could also be integrated with MECs, are also presented and reviewed. Achieving a comprehensive understanding about MEC integration could help with developing advanced biorefineries towards more sustainable energy management. Finally, the challenges related to the scaling up of these processes are also scrutinized with the aim to identify the practical hurdles faced in the MEC processes.
Enhanced bioelectrochemical treatment of petroleum refinery wastewater with Labaneh whey as co-substrate
Article, Scientific Reports, 2020, DOI Link
View abstract ⏷
Petroleum refinery wastewater (PRW) that contains recalcitrant components as the major portion of constituents is difficult to treat by conventional biological processes. Microbial fuel cells (MFCs) which also produce renewable energy were found to be promising for the treatment of PRW. However, due to the high total dissolved solids and low organic matter content, the efficiency of the process is limited. Labaneh whey (LW) wastewater, having higher biodegradability and high organic matter was evaluated as co-substrate along with PRW in standard dual chambered MFC to achieve improved power generation and treatment efficiency. Among several concentrations of LW as co-substrate in the range of 5–30% (v/v) with PRW, 85:15 (PRW:LW) showed to have the highest power generation (power density (PD), 832 mW/m2), which is two times higher than the control with PRW as sole substrate (PD, 420 mW/m2). On the contrary, a maximum substrate degradation rate of 0.420 kg COD/m3-day (ξCOD, 63.10%), was registered with 80:20 feed. Higher LW ratios in PRW lead to the production of VFA which in turn gradually decreased the anolyte pH to below 4.5 (70:30 feed). This resulted in a drop in the performance of MFC with respect to power generation (274 mW/m2, 70:30 feed) and substrate degradation (ξCOD, 17.84%).
Exploitation of Citrus Peel Extract as a Feedstock for Power Generation in Microbial Fuel Cell (MFC)
Kondaveeti S., Mohanakrishna G., Kumar A., Lai C., Lee J.-K., Kalia V.C.
Article, Indian Journal of Microbiology, 2019, DOI Link
View abstract ⏷
Microbial fuel cells (MFCs) are envisioned as an evolving cost-effective process for treating organic wastes to simultaneously generate bioelectricity. Therefore, in present study a single chambered mediator- less air cathode MFC was operated for bioelectricity generation using citrus waste (CW) as a feedstock. The MFC was operated at four organic loading conditions (OLs; 3, 6, 9 and 12 kg/m3). The voltage generation and organic content reduction demonstrated the possibility of utilizing CW as a substrate in MFC. The polarization analysis revealed a high-power generation of 71.1 mW/m2 with low OL of 3 kg/m3. The decrease in pH and high volatile fatty acids (VFAs) generation was noted at high OL. Our current findings suggest better performance of MFC, in terms of energy generation and organic reduction at high OL.
Utilization of residual organics of Labaneh whey for renewable energy generation through bioelectrochemical processes: Strategies for enhanced substrate conversion and energy generation
Kondaveeti S., Abu-Reesh I.M., Mohanakrishna G., Pant D., He Z.
Article, Bioresource Technology, 2019, DOI Link
View abstract ⏷
Labaneh whey (LW)that is rich in residual organics was evaluated for bioelectricity generation using microbial fuel cell (MFC)in two different configurations namely single chamber (MFC-SC)and dual chamber (MFC-DC)MFCs. The whole study was executed in three stages: The first stage evidenced promising amount of bioelectricity generation (DC, 643 mV; SC, 545 mV)along with chemical oxygen demand removal (CODr: DC, 60.63%; SC, CODr: 55.25%). In the second phase, activity of anodic electrogenic microbes was improved with short time poising at potentials of 400, 600 and 800 mV, among which 800 mV evidenced 2.24 (DC)and 1.60 (SC)fold enhancement in power generation along with significant improvement in substrate degradation. The third phase was solely focused on bioelectrochemical treatment of LW through applied potentials for extended period. This phase achieved 89 and 94% chemical oxygen demand (COD)degradation using SC and DC configurations, respectively at 800 mV.
Removal of petroleum hydrocarbons and sulfates from produced water using different bioelectrochemical reactor configurations
Mohanakrishna G., Al-Raoush R.I., Abu-Reesh I.M., Aljaml K.
Article, Science of the Total Environment, 2019, DOI Link
View abstract ⏷
Produced water (PW) is a wastewater generated in large quantities from the extraction of oil and gas. PW found to have high amounts of dissolved solids (TDS) and residual petroleum hydrocarbons causing considerable damage to the environment. PW also contains sulfates in significant amounts, due to which treating this wastewater is essential prior to discharge. The present study was aimed for bioelectrochemical treatment of PW and simultaneous bioelectrogenesis in the two most studied configurations viz., single and dual chamber microbial fuel cells (MFCs). The study evidenced treatment of recalcitrant pollutants of PW. Both MFCs were operated by keeping similar operating conditions such as anode chamber volume, hydraulic retention time (HRT) for batch mode of operation, electrode materials, inlet characteristics of PW and ambient temperature. Among both configurations, dual chamber MFC showed higher efficiency with respect to bioelectrogenesis (single chamber - 789 mW/m 2 ; dual chamber – 1089 mW/m 2 ), sulfates removal (single chamber – 79.6%; dual chamber – 93.9%), total petroleum hydrocarbons removal (TPH, single chamber – 47.6%; dual chamber – 53.1%) and chemical oxygen demand degradation (COD, single chamber – 0.30 kg COD/m 3 -day (COD removal efficiency, 54.7%); dual chamber – 0.33 kg COD/m 3 -day (COD removal efficiency, 60.2%)). Evaluated polarization behavior of both MFCs were also evidenced the effective response of the electroactive anodic biofilm.
Methane as a Substrate for Energy Generation Using Microbial Fuel Cells
Kondaveeti S., Mohanakrishna G., Lee J.-K., Kalia V.C.
Review, Indian Journal of Microbiology, 2019, DOI Link
View abstract ⏷
Methane (CH 4 ) is a well-known and abundant feedstock for natural gas, and is readily available from various sources. In thermal plants, the CH 4 generated from anthropogenic sources is converted into electrical energy via combustion. Microbial fuel cell (MFC) technology has proven to be an efficient strategy for the biological conversion of a many substrates, including biogas (CH 4 ), to electricity. MFC technology uses gaseous substrate along with an enriched and selective microbial consortium. Predominantly, methanotrophs and electrochemically active Geobacter were utilized in a syntrophic association on the anode of an MFC. This review focuses on the exploitation of CH 4 as a substrate for bioelectrogenesis via MFCs.
Bioelectrogenesis from Raw Algal Biomass Through Microbial Fuel Cells: Effect of Acetate as Co-substrate
Kondaveeti S., Mohanakrishna G., Pagolu R., Kim I.-W., Kalia V.C., Lee J.-K.
Article, Indian Journal of Microbiology, 2019, DOI Link
View abstract ⏷
Algae are autotrophic organisms that are widespread in water bodies. Increased pollution in water bodies leads to eutrophication. However, algae growing in lakes undergoing eutrophication could be utilized towards the generation of added-value bio-electricity using microbial fuel cells (MFCs). In the present study, two methods of electricity generation using raw algae (RA) and RA + acetate (AC) as co-substrate were analyzed in single chamber air cathode MFCs. MFCs supplemented with RA and RA + AC clearly showed higher power density, greater current generation, and improved COD (chemical oxygen demand) removal, which demonstrated the feasibility of using AC as substrate for MFC. The MFC–RA + AC (0.48 mA) generated 28% higher current relative to that generated by MFC with RA alone. Notably, the maximum power densities generated by MFC–RA and MFC–RA + AC were 230 and 410 mW/m 2 , respectively. MFC–RA and MFC–RA + AC exhibited TCOD (total chemical oxygen reduction) removal values of 77% and 86.6%, respectively. Despite the high influent TCOD (758 mg/l) concentration, the MFC–RA + AC exhibited an 8.5% higher COD removal relative to that of MFC–RA (525 mg/l). Our current findings demonstrated effective energy generation using algae biomass with a co-substrate.
A microbial fuel cell configured for the remediation of recalcitrant pollutants in soil environment
Mohanakrishna G., Al-Raoush R.I., Abu-Reesh I.M., Pant D.
Article, RSC Advances, 2019, DOI Link
View abstract ⏷
A pristine soil environment supports a healthy soil biodiversity, which is often polluted with recalcitrant compounds. The bioelectrochemical remediation of the contaminated soils using bioelectrochemical systems (BESs) is gaining significant attention with respect to the restoration of the soil ecosystem. In this direction, a microbial fuel cell (MFC, an application of BES), was employed for the treatment of total petroleum hydrocarbons (TPHs) in a soil microenvironment at three ranges of pollution (loading conditions-320, 590 and 840 mg TPH per L). TPHs degraded effectively in the soil-electrode vicinity in the range of 158 mg TPHR per L (320 mg TPH per L) and 356 mg TPHR per L (840 mg TPH per L). The study also demosntrated a maximum bioelectrogenesis of 286.7 mW m-2 (448 mV at 100 Ω) at the highest TPH loading concentration studied (840 mg TPH per L). The conditions prevailing in the soil MFC also facilitated the removal of sulfates (114 mg SO42- per L; 62.64%) and the removal of total dissolved solids (910 mg TDS per L, 12.08%) at an 840 mg TPH per L loading condition. The pH of the outlet wastewater prevailing in the mild alkaline range of 7.6 and 8.4, along with improved sulfate and TPH removal in the respective conditions suggested suitable conditions for sulfate-reducing bacteria (SRB). This study also signified the sustainability of the process for the effective treatment of hydrocarbon contaminated soil that also generates green energy.
Resource recovery from wastes and wastewaters using bioelectrochemical systems
Seelam J.S., Maesara S.A., Mohanakrishna G., Patil S.A., Ter Heijne A., Pant D.
Book chapter, Waste Biorefinery: Potential and Perspectives, 2018, DOI Link
View abstract ⏷
Recent scientific and technological advancements in bioelectrochemical system (BES) research have opened up several avenues for realizing the concept of bio-based economy. Current research within this area has been directed toward exploring their applicability to generate a wastewater biorefinery. Valorization of resources in the form of energy, nutrients, metals, and chemicals has been actively exhibited using this technology. This chapter highlights the fundamentals and technological aspects of bioelectrochemical resource recovery from wastes and wastewaters with detailed emphasis on the latest trends of bioelectrorecovery systems (BERSs). Several wastes and wastewater feedstocks are enlisted and classified based on their prospects for resource and energy recovery. Two representative case studies, existing challenges, and a brief overview of the relative advantages and disadvantages of BERSs over alternative resource recovery options are also included. Further, an outlook is given for realizing resource recovery using BESs as a sustainable technology in the domain of energy and resource management.
Integrated bioelectrochemical platforms
El Mekawy A., Hegab H.M., Mohanakrishna G., Pant D., Wang H.
Book chapter, Biomass, Biofuels, Biochemicals: Microbial Electrochemical Technology: Sustainable Platform for Fuels, Chemicals and Remediation, 2018, DOI Link
View abstract ⏷
Energy and water are intrinsically linked, as all energy sources need water for their production processes, and at the same time, water resources require energy to be available for human consumption. One of the promising technologies that is concerned with dealing with water/energy challenges is bioelectrochemical systems (BESs), which use microbial cells to transform the chemical energy stowed in biodegradable organic materials to direct electric energy and chemicals. The generated current is utilized to develop several applications, e.g., power production (microbial fuel cells), water desalination (microbial desalination cells), hydrogen (microbial electrolysis cells) or chemicals synthesis (microbial electrosynthesis cells). However, these technologies are still in their early-stage of development and are confronted with several challenges. Integration with other technologies, e.g., capacitive deionization and membrane bioreactor, was proposed to overcome these challenges. This chapter provides a broad evaluation of all the recently developed BES integrated systems, with focus on their constructions and performances.
Enzymatic electrosynthesis toward value addition
Mohanakrishna G., Kondaveeti S., Desale P., El Mekawy A., Abu-Reesh I.M.
Book chapter, Biomass, Biofuels, Biochemicals: Microbial Electrochemical Technology: Sustainable Platform for Fuels, Chemicals and Remediation, 2018, DOI Link
View abstract ⏷
Utilization of enzymes as biocatalyst found to have specific advantages over whole-cell bacterial biocatalyst in electrochemical systems. The process of enzymatic catalysis in association with electrodes was found to have several advantages for the specific product synthesis, and these systems were termed as enzyme-catalyzed electrosynthesis systems (EESs). Conversion of carbon dioxide (CO2) to produce biofuels and chemicals through EES is found deliver bioprocesses future generations. The present chapter is focused on the fundamental science of EESs to produce biofuel and biochemicals. The chapter also presents the detailed discussion on anodic and cathodic reactions and the electrode materials involved in the electroenzymatic catalysis. It was found to have influence of enzyme electrode compatibility, application of nanomaterials for the improved enzymatic electrocatalysis, and types of electron transfer mechanism involved in the enzymatic electrochemical systems. This chapter provides a detailed evaluation of all the recently developed enzymatic electrosynthesis systems with prime focus on the factors influencing overall performance and its applications in sustainable development.
Cylindrical graphite based microbial fuel cell for the treatment of industrial wastewaters and bioenergy generation
Mohanakrishna G., Abu-Reesh I.M., Al-Raoush R.I., He Z.
Article, Bioresource Technology, 2018, DOI Link
View abstract ⏷
Cylindrical graphite microbial fuel cell (MFC) configuration designed by eliminating distinct casing and membrane was evaluated for bioelectrogenesis and treatment of real-field wastewaters. Both petroleum refinery wastewater (PRW) and Labanah whey wastewater (LW) were used as substrates, and investigated for electricity generation and organic removal under batch mode operation. PRW showed higher bioelectricity generation (current and power generation of 3.35 mA and 1.12 mW at 100 Ω) compared to LW (3.2 mA and 1.02 mW). On the contrary, higher substrate degradation efficiency was achieved using LW (72.76%) compared to PRW (45.06%). Superior function of MFC operation in terms of volumetric power density (PRW, 28.27 W/m3; LW, 23.23 W/m3) suggesting the feasibility of using these wastewaters for bioelectricity generation. Large sources of wastewater that generating in the Middle-East countries have potential to produce renewable energy from the treatment, which helps for the sustainable wastewater management and simultaneous renewable energy production.
Enhanced treatment of petroleum refinery wastewater by short-term applied voltage in single chamber microbial fuel cell
Mohanakrishna G., Abu-Reesh I.M., Kondaveeti S., Al-Raoush R.I., He Z.
Article, Bioresource Technology, 2018, DOI Link
View abstract ⏷
Electrochemically active anodic biofilm that has adapted under mild applied potentials in the range 100–500 mV was evaluated for its improved bioelectrogenesis and bioelectrochemical treatment of petroleum refinery wastewater (PRW) in a single chamber air cathode microbial fuel cell (MFC). MFC operation with 500 mV as supplemental voltage has exhibited a maximum power density of 132 mW/m2, which was three times higher than control MFC (45 mW/m2). Similarly, highest substrate removal efficiency (48%) was also obtained with the MFC of 500 mV, followed by 300 mV (37%), 100 mV (32%) and control (27%). Adaptation under applied potential conditions also exhibited enhanced degradation efficiency of diesel range organics (DROs)/straight chain-alkanes. The strategy efficiently reduced DROs with the maximum efficiency of 89% (500 mV), which is almost 50% higher than that of the control system (59%), demonstrating the effectiveness of using supplemented voltage in treating PRW.
Impact of dissolved carbon dioxide concentration on the process parameters during its conversion to acetate through microbial electrosynthesis
Article, Reaction Chemistry and Engineering, 2018, DOI Link
View abstract ⏷
The reduction of carbon dioxide (CO2) released from industry can help to reduce the emissions of greenhouse gases (GHGs) to the atmosphere while at the same time producing value-added chemicals and contributing to carbon fixation. Microbial electrosynthesis (MES) is a recently developed process which accomplishes this idea by using cathodic bacteria at the expense of only minimum energy. In this study, enriched mixed homoacetogenic bacteria as cathodic biocatalysts for the reduction of CO2 with five different concentrations were evaluated to produce acetate at a constant potential. Increasing the carbon concentration showed an improved acetate production rate and carbon conversion efficiency. A maximum acetate production rate of 142.2 mg L per day and a maximum carbon conversion efficiency of 84% were achieved, respectively, at 4.0 and 2.5 g HCO3- L-1. The changes in pH due to interactive reactions between the bicarbonate (substrate) and acetate (products) were able to create a buffering nature in the catholyte controlling the operating parameters of the MES process, such as pH and substrate specificity. A higher acetate production shifted the catholyte pH toward acidic conditions, which further triggered favorable conditions for the bioelectrochemical reduction of acetate to ethanol.
Induced bioelectrochemical metabolism for bioremediation of petroleum refinery wastewater: Optimization of applied potential and flow of wastewater
Article, Bioresource Technology, 2018, DOI Link
View abstract ⏷
Hybrid based bioelectrochemical system (BES) configured with embedded anode and cathode electrodes in soil was tested for the bioelectrochemical degradation of petroleum refinery wastewater (PRW). Four applied potentials were studied to optimize under batch mode operation, among which 2 V resulted in higher COD degradation (69.2%) and power density (725 mW/m2) during 7 days of operation. Further studies with continuous mode of operation at optimized potential (2 V) showed that hydraulic retention time (HRT) of 19 h achieved the highest COD removal (37%) and highest power density (561 mW/m2). BES function with respect to treatment efficiencies of other pollutants of PRW was also identified with respect to oil and grease (batch mode, 91%; continuous mode, 34%), total dissolved salts (batch mode, 53%; continuous mode, 24%) and sulfates (batch mode, 59%; continuous mode, 42%). Soil microenvironment in association with BES forms complex processes, providing suitable conditions for efficient treatment of PRW.
Biological anodic oxidation and cathodic reduction reactions for improved bioelectrochemical treatment of petroleum refinery wastewater
Article, Journal of Cleaner Production, 2018, DOI Link
View abstract ⏷
Bioelectrochemical systems (BESs) were evaluated for the bioelectrochemical treatment (BET) of petroleum refinery wastewater (PRW) by applying mild electrochemical potential in the range of 400–1000 mV on a single chamber membrane-less BES configured with anodic and cathodic biofilms. After four days of cycle operation in batch mode, BES achieved a maximum current density of 278 mA/m2 and a power density of 222 mW/m2 using applied potential of 800 mV. This system also achieved COD degradation rate of 0.364 kg COD/m3-day. Diesel range organics (DROs) exhibited more than 90% degradation, which is 15 times higher than the abiotic control. Electrochemically active bioanode and biocathode contributed to the degradation of PRW through both oxidation and reduction reactions with mild applied potentials. This also resulted in a 30% improvement in COD removal compared to MFC with biocatalyst only on the anode. The function of improved bioelectrochemical treatment was also exhibited by redox current values of cyclic voltammograms.
Surpassing the current limitations of high purity H2 production in microbial electrolysis cell (MECs): Strategies for inhibiting growth of methanogens
Kadier A., Kalil M.S., Chandrasekhar K., Mohanakrishna G., Saratale G.D., Saratale R.G., Kumar G., Pugazhendhi A., Sivagurunathan P.
Review, Bioelectrochemistry, 2018, DOI Link
View abstract ⏷
Microbial electrolysis cells (MECs) are perceived as a potential and promising innovative biotechnological tool that can convert carbon-rich waste biomass or wastewater into hydrogen (H2) or other value-added chemicals. Undesired methane (CH4) producing H2 sinks, including methanogens, is a serious challenge faced by MECs to achieve high-rate H2 production. Methanogens can consume H2 to produce CH4 in MECs, which has led to a drop of H2 production efficiency, H2 production rate (HPR) and also a low percentage of H2 in the produced biogas. Organized inference related to the interactions of microbes and potential processes has assisted in understanding approaches and concepts for inhibiting the growth of methanogens and profitable scale up design. Thus, here in we review the current developments and also the improvements constituted for the reduction of microbial H2 losses to methanogens. Firstly, the greatest challenge in achieving practical applications of MECs; undesirable microorganisms (methanogens) growth and various studied techniques for eliminating and reducing methanogens activities in MECs were discussed. Additionally, this extensive review also considers prospects for stimulating future research that could help to achieve more information and would provide the focus and path towards MECs as well as their possibilities for simultaneously generating H2 and waste remediation.
Anodic electron transfer mechanism in bioelectrochemical systems
Book chapter, Microbial Fuel Cell: A Bioelectrochemical System that Converts Waste to Watts, 2017, DOI Link
Reactor design for bioelectrochemical systems
Book chapter, Microbial Fuel Cell: A Bioelectrochemical System that Converts Waste to Watts, 2017, DOI Link
Scaling up of MFCs: Challenges and case studies
Seelam J.S., Rundel C.T., Boghani H.C., Mohanakrishna G.
Book chapter, Microbial Fuel Cell: A Bioelectrochemical System that Converts Waste to Watts, 2017, DOI Link
Spatiometabolic stratification of anoxic biofilm in prototype bioelectrogenic system
Mohanakrishna G., Butti S.K., Kannaiah Goud R., Venkata Mohan S.
Article, Bioelectrochemistry, 2017, DOI Link
View abstract ⏷
A prototype bio-catalyzed electrogenic system integrated with a biological treatment process (SBR-BET) was evaluated to study specific function of anoxic condition on the electrogenic activity. A multiphasic approach was employed, where the influence of DO on bio-electrogenic activity was optimized initially, later optimal anode to cathode inter-electrode distance was enumerated. Amongst the four electrode distances evaluated, 2 cm showed higher power output. Bioelectrokinetics analysis was used to validate the system performance with the experimental variation studied. The redox behavior showed an increase in cathodic catalytic activity with an increase in the inter-electrode distance. Spatiometabolic distribution depicted the microbial stratification on the anode. Electrochemically active bacteria present on the anode surface (inner and outer layers of biofilms) showed relatively uniform diversity compared with the suspension culture.
Biotransformation of carbon dioxide in bioelectrochemical systems: State of the art and future prospects
Bajracharya S., Srikanth S., Mohanakrishna G., Zacharia R., Strik D.P., Pant D.
Article, Journal of Power Sources, 2017, DOI Link
View abstract ⏷
Carbon dioxide (CO2) utilization/recycling for the production of chemicals and gaseous/liquid energy-carriers is a way to moderate the rising CO2 in the atmosphere. One of the possible solutions for the CO2 sequestration is the electrochemical reduction of this stable molecule to useful fuel/products. Nevertheless, the surface chemistry of CO2 reduction is a challenge due to the presence of large energy barriers, requiring noticeable catalysis. The recent approach of microbial electrocatalysis of CO2 reduction has promising prospects to reduce the carbon level sustainably, taking full advantage of CO2-derived chemical commodities. We review the currently investigated bioelectrochemical approaches that could possibly be implemented to enable the handling of CO2 emissions. This review covers the most recent advances in the bioelectrochemical approaches of CO2 transformations in terms of biocatalysts development and process design. Furthermore, the extensive research on carbon fixation and conversion to different value added chemicals is reviewed. The review concludes by detailing the key challenges and future prospects that could enable economically feasible microbial electrosynthesis technology.
Bioprocesses for waste and wastewater remediation for sustainable energy
Book chapter, Bioremediation and Bioeconomy, 2016, DOI Link
View abstract ⏷
Microbial metabolism of pollutants is the key process involved in energy generation along with remediation. This process led by the different electron acceptors operates under diverse operations. Engineering these for renewable energy products is of prime importance for sustainable development. This chapter describes the bioremediation process in generating the various types of bioenergies that help sustainable development. Anaerobic process of organic matter degradation is the major process that contributes to energy generation. The operating conditions and process control help in the generation of different energy vectors like methane, hydrogen, and electricity. Another approach gaining prominence in wastewater treatment is phytoremediation, led by microalgae. The heterotrophic growth of microalgae aids in the organic contaminants' removal from wastewater as well as carbon dioxide sequestration from the atmosphere to generate lipids for biodiesel and carbohydrates.
The Role of Bioreactors in Industrial Wastewater Treatment
ElMekawy A., Mohanakrishna G., Srikanth S., Pant D.
Book chapter, Environmental Waste Management, 2016, DOI Link
View abstract ⏷
Industrialization across the globe has resulted in the contamination of soils, groundwater, sediments, surface water, and air with hazardous and toxic chemicals, which is one of the major problems to be resolved by the research presently being carried out globally. Providing clean and affordable water to meet human needs is another grand challenge of the twenty-rst century. The more the world industrializes, the more are the waste generation and contamination problems. In general, groundwater represents about 98% of the available fresh water on the planet and thus, protecting and restoring groundwater quality is of high importance. Water supply across the globe struggles to keep up with the fast growing demand, which is exacerbated by population growth, global climate change, and water quality deterioration. This widespread problem represents a signicant technical and economic challenge. Globally, a huge amount of capital and resources is being spent for treating trillions of litres of wastewater annually, consuming signicant amounts of energy (ElMekawy et al., 2013, 2014a, b). Therefore, there is a need for developing a wider application of cost-effective, in situ remediation approaches that take advantage of natural phenomena, such as bioremediation. Biological treatment is an important and integral part of any wastewater treatment plant that treats wastewater that has soluble organic impurities or a mix of the two sources from either municipality or industry (Pant and Adholeya, 2007). The economic advantage of biological treatment over other treatment processes such as chemical oxidation, thermal oxidation, etc., in terms of capital investment and operating costs has established its place in any integrated wastewater treatment plant (Mittal, 2011). The current chapter describes the major existing challenges of industrial wastewater treatment and how advanced biological processes are dealing with them. The role of different bioreactors in treating industrial efuents has also been discussed in detail including recent advances.
Product Specificity Influenced by Catholyte Conditions during the Microbial Electrosynthesis Process CO2to Acetate
Bajracharya S., Mohanakrishna G., Vanbroekhoven K., De Wever H., Pant D., Buisman C.J.N., Strik D.
Article, Chemie-Ingenieur-Technik, 2016, DOI Link
Technological advances in CO2 conversion electro-biorefinery: A step toward commercialization
ElMekawy A., Hegab H.M., Mohanakrishna G., Elbaz A.F., Bulut M., Pant D.
Review, Bioresource Technology, 2016, DOI Link
View abstract ⏷
The global atmospheric warming due to increased emissions of carbon dioxide (CO2) has attracted great attention in the last two decades. Although different CO2 capture and storage platforms have been proposed, the utilization of captured CO2 from industrial plants is progressively prevalent strategy due to concerns about the safety of terrestrial and aquatic CO2 storage. Two utilization forms were proposed, direct utilization of CO2 and conversion of CO2 to chemicals and energy products. The latter strategy includes the bioelectrochemical techniques in which electricity can be used as an energy source for the microbial catalytic production of fuels and other organic products from CO2. This approach is a potential technique in which CO2 emissions are not only reduced, but it also produce more value-added products. This review article highlights the different methodologies for the bioelectrochemical utilization of CO2, with distinctive focus on the potential opportunities for the commercialization of these techniques.
Imperative role of applied potential and inorganic carbon source on acetate production through microbial electrosynthesis
Article, Journal of CO2 Utilization, 2016, DOI Link
View abstract ⏷
Graphical abstract: Microbial electrosynthesis (MES) is a novel technology that produces organic molecules from the reduction of carbon dioxide (CO2) at biocathode. MES system is a hybrid device that combines components of biological and fuel cells in a single system for chemicals/energy generation from inexpensive substrates. Present study evaluates the influence of cathodic potentials (−800mV and −600mV) on reduction of CO2 to acetate using enriched acetogenic bacteria as the biocatalyst at 30°C using graphite and VITO carbon electrodes as cathode and anode respectively. The first stage of evaluation of bicarbonate as carbon source was continued to second stage where gaseous CO2 used as C source. In both the stages −800mV showed higher acetate production efficiency. MES reactor with cathodic potential of −800mV showed 4.05 and 5.45gacetate/L respectively during first and second stage. Changing the carbon source of the systems from bicarbonate to CO2 positively influence the performance. Moreover, change in operation mode from continuous to batch resulted in improved acetate production rate, which also proved that the performance was reproducible and stable. Continuous CO2 supply maintained the pH near neutral which might explain the traces of ethanol produced in the system. Higher coulombic efficiency was also registered with −800mV operation than −600mV.
An overview on emerging bioelectrochemical systems (BESs): Technology for sustainable electricity, waste remediation, resource recovery, chemical production and beyond
Bajracharya S., Sharma M., Mohanakrishna G., Dominguez Benneton X., Strik D.P.B.T.B., Sarma P.M., Pant D.
Article, Renewable Energy, 2016, DOI Link
View abstract ⏷
Bioelectrochemical systems (BESs) are unique systems capable of converting chemical energy into electrical energy (and vice-versa) while employing microbes as catalysts. Such organic wastes including low-strength wastewaters and lignocellulosic biomass were converted into electricity with microbial fuel cells (MFCs). Likewise, electrical energy was used to produce hydrogen in microbial electrolysis cells (MECs) or other products including caustic and peroxide. BES were also designed to recover nutrients, metals or removal of recalcitrant compounds. Moreover, photosynthetic micro-organisms as well as higher plants were implemented to use solar energy for electricity generation. The diversity on microbial and enzymatic catalysts offered by nature allows a plurality of potential applications. As compared to conventional fuel cells, BESs operate under relatively mild conditions and do not use expensive precious metals as catalysts. The recently discovered microbial electrosynthesis (MES) of high-value chemicals has greatly expanded the horizon for BES. Newer concepts in application as well as development of alternative materials for electrodes, separators, catalysts along with innovative designs have made BES very promising technology. This article discusses the recent developments that have been made in BESs so far, with the emphasis on their various applications beyond electricity generation and resulting performances as well as existing limitations.
Bioelectrochemical systems (Bes) for microbial electroremediation: An advanced wastewater treatment technology
Book chapter, Applied Environmental Biotechnology: Present Scenario and Future Trends, 2015, DOI Link
View abstract ⏷
Bioelectrochemical systems (BES) have been employed for various applications in recent years including energy production, wastewater treatment, electrosynthesis and desalination. The present chapter emphasizes the advantages and potential applications of BES for the remediation of recalcitrant pollutants present in various types of wastewaters. Bioelectricity generated from the treatment of these wastewaters is an additional energy output from the process along with the possible environmental solution. Since, the treatment mechanism of BES is combination of both microbial and electrochemical reactions, the process can be termed as microbial electroremediation. The current chapter depicts the principles of bioelectrochemical remediation, possible mechanisms at anode and cathode. Further, a comprehensive overview on different types of wastewater as well as nutrients, pollutants and toxic substances, utilized as electron donors or acceptors for their treatment, is discussed in detail under different categories. Microbial electroremediation is still an emerging field of science aimed at harnessing energy from wastewater treatment and it has a potential to boon the waste remediation with net positive energy gain.
An enriched electroactive homoacetogenic biocathode for the microbial electrosynthesis of acetate through carbon dioxide reduction
Mohanakrishna G., Seelam J.S., Vanbroekhoven K., Pant D.
Article, Faraday Discussions, 2015, DOI Link
View abstract ⏷
In the direction of generating value added chemicals from carbon dioxide (CO2) reduction through microbial electrosynthesis (MES), considering the crucial impact of the electrode material for the biofilm development and electron delivery, an attempt was made in this study to evaluate the efficiency of two different materials as biocathodes and their respective output in terms of electrosynthesis. The electrode material is a key component in the MES process. Several electrodes such as platinum, graphite foil, dimentionally stable anode (DSA) and graphite rod, and VITO-CoRE™ derived electrodes were tested for their suitability for ideal electrode combination in a three electrode cell setup. Bicarbonates (the dissolved form of CO2) was reduced to acetate by a selectively developed biocathode under a mild applied cathodic potential of -400 mV (vs. SHE) in 500 mL of single chamber MES cells operating for more than four months. Among the two electrode combinations evaluated, VITO-CoRE™-PL (VC-IS, plastic inert support) as the cathode and VITO-CoRE™-SS (VC-SS, stainless steel metal support) as the counter electrode showed higher production (4127 mg L-1) with a volumetric production rate of 0.569 kg per m3 per d than the graphite rod (1523 mg L-1) with a volumetric production rate of 0.206 kg per m3 per d. Contrary to the production efficiencies, the coulombic efficiency was higher with the second electrode combination (40.43%) than the first electrode combination (29.91%). Carbon conversion efficiency to acetate was higher for VC-IS (90.6%) than the graphite rod (82.0%).
Multiple process integrations for broad perspective analysis of fermentative H2 production from wastewater treatment: Technical and environmental considerations
Article, Applied Energy, 2013, DOI Link
View abstract ⏷
The functional certainty associated with secondary or tertiary process integration towards enhancing the viability of fermentative biohydrogen (H2) production from wastewater stabilization was investigated with eleven diverse combinations of dark-fermentation (acidogenic, HA), photo-fermentation (HP for H2) and methanogenic (for CH4) processes. Based on the specificity of individual process, the biocatalyst and the feeding pH were selected and operated at uniform hydraulic retention time (48h). Individually, HP operation showed higher H2 production (4.10mmol H2) and yield (16.02mol H2/kg CODR) than of HA (3.38mmol H2, 11.33mol H2/kg CODR) which was found contrary to the observed substrate degradation. Two-stage process integration showed marked improvement in both H2 production and substrate degradation. Integration of HP with HA showed maximum H2 production while HA with HP evidenced maximum H2 yield. Integration of methanogenic process with HP documented both higher biogas production and yield. Maximum substrate degradation was evidenced with three stage sequential integration of dark-fermentation, methanogenic and photo-fermentation processes. Three-stage integration contributed for higher substrate degradation rather than energy generation, especially with HP as the terminal process. Organic flux, energy efficiency and carbon footprint analyses were used to comprehensively delineate the practical consideration of the integrated processes. © 2013 Elsevier Ltd.
Rhizosphere mediated electrogenesis with the function of anode placement for harnessing bioenergy through CO2 sequestration
Chiranjeevi P., Mohanakrishna G., Venkata Mohan S.
Article, Bioresource Technology, 2012, DOI Link
View abstract ⏷
The feasibility of power generation by non-destructive usage of rhizodeposits of Pennisetum setaceum plant formed mainly due to photosynthesis-carbon sequestration mechanism was studied in rhizosphere based microbial fuel-cell (R-MFC). Four fuel-cell assemblies (non-catalyzed graphite-plates; membrane-less operation; air-cathode) were evaluated for their electrogenic activity by varying anode distances from root in rhizosphere [A1 - 0; A2 - 8; A3 - 12 and A4 - 16. cm] at 2. cm depth from soil-layer and analyzed their electrogenic potential. The fuel-cell assembly near to the root zone showed maximum electrogenic-activity (R1, 1007. mV/4.52. mA) followed by R2 (780. mV/4.11. mA), R3 (720. mV/3.4. mA) and R4 (220. mV/1.2. mA). The observed maximum electrogenesis with R1 and minimum with R4 electrode-assemblies enumerated the critical role of root-exudates as substrates. All fuel-cell assemblies showed 10% higher electrogenic activity during day-time operation which can be directly attributed to plant's photosynthetic activity. The study enumerated the potential of plant to harness power in a sustainable way by optimum placement of fuel-cell setup in their rhizosphere. © 2012 Elsevier Ltd.
Predominance of Bacilli and Clostridia in microbial community of biohydrogen producing biofilm sustained under diverse acidogenic operating conditions
Goud R.K., Raghavulu S.V., Mohanakrishna G., Naresh K., Mohan S.V.
Article, International Journal of Hydrogen Energy, 2012, DOI Link
View abstract ⏷
Microbial community structure of acidogenic biofilm from long-term operated sequencing batch bioreactor producing biohydrogen was analyzed through culture independent technique. Bioreactor was operated under variable operation and substrate conditions for a period of 1435 days. Phylogenetic distribution showed a significant diversity and illustrated the presence of four dominant operational taxonomic units (OTUs) viz., Bacteroidia, Bacilli, Clostridia, Flavobacteria and Aquificae. Dominance of Clostridia and Bacilli classes were observed each with four OTUs. Majority of OTUs were found to produce fermentative H2. Even at higher load and under diverse operating conditions bioreactor functioned without any process inhibition which indicates the robustness of sustained microbial community. Community structure of bioreactor was comparatively evaluated with other bioreactor producing H 2, operated with same parent culture and conditions but with different substrates, established the dynamics and shift of microbial diversity which corresponded to diverse substrates used for the bioreactor operation. Copyright © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Evaluation of voltage sag-regain phases to understand the stability of bioelectrochemical system: Electro-kinetic analysis
Velvizhi G., Babu P.S., Mohanakrishna G., Srikanth S., Mohan S.V.
Article, RSC Advances, 2012, DOI Link
View abstract ⏷
Voltage sag, regain and their stabilization phases were evaluated with time across load (closed circuit) and absence of load (short circuit) to understand the stability of the bio-electrochemical system (BES) under varying organic loads (OL). Closed circuit operation showed good stability along with the electrogenic activity over short circuit operation during both the sag and regain phases due to the regulated electron flow in the closed circuit. Relative change in voltage with time (dV/dt) was observed to be decreasing with increasing OL in the zone of sag, while it was observed to be increasing with increase in OL during the zone of regain. However, the change in dV/dt was not proportional with increasing OL during both the sag and regain phases indicating the influence of OL on the biocatalytic activity. Bio-electrocatalytic evaluation through Tafel analysis showed a gradually decreasing reductive slope from OL1 (0.62 V/dec) to OL4 (0.516 V/dec) indicating higher electrocatalytic activity towards reduction. While, the oxidative slope increased from OL1 (0.085 V/dec) to OL2 and was almost similar with further increment in the OL (0.099 ± 0.002 V/dec) which indicates marginal change in the electrocatalytic activity during oxidation even with increasing OL. Exchange current density from Tafel analysis was also observed to increase with increase in OL (OL1, 7.86 mA m -2; OL2, 8.33 mA m -2; OL3, 9.59 mA m -2; OL4, 11.77 mA m -2). Polarization resistance showed a decreasing trend with increasing OL (OL1, 12.23 Ω to OL4, 9.8 Ω) resulting in higher electron transfer. © 2012 The Royal Society of Chemistry.
A rapid and simple protocol for evaluating biohydrogen production potential (BHP) of wastewater with simultaneous process optimization
Article, International Journal of Hydrogen Energy, 2012, DOI Link
View abstract ⏷
Biohydrogen production utilizing negative valued waste through dark-fermentation process is one of the emerging areas. Reported conditions for H2 production are significantly variable and comparative analysis of data is major problem for unified understanding. A simple, rapid and generalized two phase methodology/protocol was developed to evaluate the biohydrogen production potential (BHP) of negative valued wastewater as substrate/feed-stock for renewable biohydrogen production using mixed consortia. Critical factors that can influence the overall process viz., redox condition, organic load and biocatalyst were considered in the designing the methodology. Feasibility of protocol was initially evaluated with synthetic wastewater and further validated with real field composite food and slaughter house wastewaters. The selected operational factors showed marked influence on both H2 production and wastewater treatment. The reported methodology/protocol not only provides the ability of selected wastewater to generate H2 but also facilitates process understanding based on selected factors and finally acquiesce optimum conditions. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Carbon based nanotubes and nanopowder as impregnated electrode structures for enhanced power generation: Evaluation with real field wastewater
Mohanakrishna G., Krishna Mohan S., Venkata Mohan S.
Article, Applied Energy, 2012, DOI Link
View abstract ⏷
Carbon based multiwalled nanotubes (MWCNT) and nanopowder (CNP) impregnated using conductive epoxy resin on anodic surface were evaluated for bioelectricity generation in single chambered microbial fuel cells in comparison with plain graphite anode (MFCP). The study demonstrated the positive function of carbon nano structures impregnated anode with respect to power generation. MFCMWCNT exhibited higher electrogenic activity (267.77mW/m2) followed by MFCCNP (168.45mW/m2) and MFCP (107.51mW/m2). MFCMWCNT and MFCCNP showed 148% and 57% enhancement in the power generation respectively compared to MFCP. Microbial mediators were also found to be more effective with modified anodes operation. Impregnation with nano material facilitates higher surface area that enables higher charge transfer from anolyte to electrodes. Impregnated anodes showed marginal influence on substrate degradation. Further, feasibility of MWCNT impregnated anode was evaluated with real field distillery wastewater which depicted good electrogenic activity (245.34mW/m2) and yield (3.43W/m3). © 2012 Elsevier Ltd.
Natural attenuation of endocrine-disrupting estrogens in an ecologically engineered treatment system (eets) designed with floating, submerged and emergent macrophytes
Kumar A.K., Chiranjeevi P., Mohanakrishna G., Mohan S.V.
Article, Ecological Engineering, 2011, DOI Link
View abstract ⏷
Natural attenuation of estrogenic endocrine disrupting compounds (EDCs) such as estriol (E3, natural) and 17α-ethinylestradiol (EE2, synthetic) were evaluated in a designed ecologically engineered treatment system (EETS) along with domestic sewage. These two estrogens are the major contaminants of sewage and found to cause adverse effects on the endocrine system of humans and animals when exposed even in nanogram concentrations. The EETS consisted of three tanks containing diverse biota, viz., aquatic macrophytes, submerged plants, emergent plants, algae and bacteria present in the system mimic the natural cleansing functions of wetlands and help in the treatment of pollutants present in wastewater. During operation, 22 μg/l of E3 and EE2 were separately fed for 10 days each and operated in continuous mode (20. l/day). The floating macrophytes system (Tank 1) was more effective in removing estrogens [E3 - 61.77% (13.59 μg/l); EE2 - 69.09% (15.20 μg/l)] compared to the submerged-emergent macrophytes-based integrated system (Tank 2) [E3 - 16.58% (3.65 μg/l); EE2 - 18.52% (4.08 μg/l)] and submerged-rooted microphytes system (Tank 3) [E3 - 15.20%, (3.35 μg/l); EE2 - 7.72%, (1.70 μg/l)]. On the whole, EETS can effectively treat EDCs [E3 93.56% (20.59 μg/l); EE2 95.34% (20.97 μg/l)]. Removal of COD (68.06%), nitrates (60.02%) and turbidity (83.43%) was also observed simultaneously during EETS operation. The designed EETS is ecologically complex and mechanically simple and has very low energy consumption and function based on a natural cleansing mechanism (attenuation) with esthetic value. © 2011 Elsevier B.V.
Potential of mixed microalgae to harness biodiesel from ecological water-bodies with simultaneous treatment
Venkata Mohan S., Prathima Devi M., Mohanakrishna G., Amarnath N., Lenin Babu M., Sarma P.N.
Article, Bioresource Technology, 2011, DOI Link
View abstract ⏷
Biodiesel as an eco-friendly fuel is gaining much acceptance in recent years. This communication provides an overview on the possibility of using mixed microalgae existing in ecological water-bodies for harnessing biodiesel. Microalgal cultures from five water-bodies are cultivated in domestic wastewater in open-ponds and the harvested algal-biomass was processed through acid-catalyzed transesterification. Experiments evidenced the potential of using mixed microalgae for harnessing biodiesel. Presence of palmitic acid (C16:0) in higher fraction and physical properties of algal oil correlated well with the biodiesel properties. Functional characteristics of water-bodies showed to influence both species diversity and lipid accumulation. Microalgae from stagnant water-bodies receiving domestic discharges documented higher lipid accumulation. Algal-oil showed to consist 33 types of saturated and unsaturated fatty acids having wide food and fuel characteristics. Simultaneous wastewater treatment was also noticed due to the syntrophic association in the water-body microenvironment. Diversity studies visualized the composition of algae species known to accumulate higher lipids. © 2010 Elsevier Ltd.
Firmicutes with iron dependent hydrogenase drive hydrogen production in anaerobic bioreactor using distillery wastewater
Venkata Mohan S., Agarwal L., Mohanakrishna G., Srikanth S., Kapley A., Purohit H.J., Sarma P.N.
Article, International Journal of Hydrogen Energy, 2011, DOI Link
View abstract ⏷
Distillery wastewater rich in organics is an inexpensive renewable resource for making first generation biofuel. Distillery wastewaters are mostly treated via the biomethanation route; however, in this study the conditions in sequential batch reactor (SBR) are being set to develop and analyze the microbial community that opted for hydrogen production. An optimum performance condition for a bioreactor was achieved after 40 days of operation, which gave substrate degradation rate of 0.72 kg/m3-day with volumetric hydrogen production of 0.32 mol H2/m3-day. Study proposes that the dominant Delftia sp., a hydrogen oxidizing bacterium has been replaced during hydrogen production mode with dominant Anaerofilum sp., an anaerobic Firmicute and the iron dependent hydrogenases dominated as functional gene for hydrogen production. Future studies are required where process-engineering interventions could be applied to improve the hydrogen driving biochemical process. © 2011 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Sustainable power generation from floating macrophytes based ecological microenvironment through embedded fuel cells along with simultaneous wastewater treatment
Venkata Mohan S., Mohanakrishna G., Chiranjeevi P.
Article, Bioresource Technology, 2011, DOI Link
View abstract ⏷
Miniatured floating macrophyte based ecosystem (FME) designed with Eichornia as the major biota was evaluated for bioelectricity generation and wastewater treatment. Three fuel cell assemblies (non-catalyzed electrodes) embedded in FME were evaluated with domestic sewage and fermented distillery wastewater in continuous mode for 210 days. Fermented distillery effluents from biohydrogen production (dark-fermentation) process exhibited effective power generation with simultaneous waste remediation. Two fuel cell assemblies (A1 and A2) showed effective bioelectricity generation. Increasing the organic load of wastewater showed good correlation with both power generation (A1, 211.14mA/m2; A2, 224.93mA/m2) and wastewater treatment (COD removal, 86.67% and VFA removal 72.32%). Combining A1 and A2 assemblies depicted stabilized performance with respect to current and voltage along with significant decrease in ohmic and activation losses. FME also exhibited effective removal of nitrates, colour and turbidity from wastewater. The studied miniatured ecological system facilitates both energy generation and wastewater treatment with a sustainable perspective. © 2011 Elsevier Ltd.
Biohydrogen Production from Industrial Effluents
Book chapter, Biofuels: Alternative Feedstocks and Conversion Processes, 2011, DOI Link
View abstract ⏷
Hydrogen (H2) has been considered as a sustainable energy carrier as it is clean (does not emit any toxic by-product or greenhouse gases), efficient, and renewable. Currently, H2 is being produced mainly from fossil fuels, biomass, and water. H2 production through biological routes is considered as one of the opportunistic and sustainable ways to meet the future energy demand and to prevent fossil fuel-based environmental impacts. Biological approaches for producing H2 also facilitate the conversion of negative-value organic waste. Broadly, biological H2 can be produced through two main mechanisms: photosynthesis and dark fermentation. Photosynthesis is a light-dependent process, while dark fermentation (anaerobic) is a light-independent catabolic process. Most of the biological H2 production processes are operated at ambient temperatures and pressures regarded as less energy intensive and therefore considered as a potential alternative to the conventional physical/chemical methods usually opted for H2 production. Biohydrogen can also be viewed as energy source and an intermediate towards the production of VFA (volatile fatty acids). VFA present in these effluents generated from H2 producing reactor can be further transformed to PHAs or can be used for biohydrogenation of fatty acids into alcohols.
Biohydrogen production from industrial effluents
Book chapter, Biofuels, 2011, DOI Link
View abstract ⏷
Hydrogen (H2) has been considered as a sustainable energy carrier as it is clean (does not emit any toxic by-product or greenhouse gases), efficient, and renewable. Currently, H2 is being produced mainly from fossil fuels, biomass, and water. H2 production through biological routes is considered as one of the opportunistic and sustainable ways to meet the future energy demand and to prevent fossil fuel-based environmental impacts. Biological approaches for producing H2 also facilitate the conversion of negative-value organic waste. Broadly, biological H2 can be produced through two main mechanisms: photosynthesis and dark fermentation. Photosynthesis is a light-dependent process, while dark fermentation (anaerobic) is a light-independent catabolic process. Most of the biological H2 production processes are operated at ambient temperatures and pressures regarded as less energy intensive and therefore considered as a potential alternative to the conventional physical/chemical methods usually opted for H2 production. Biohydrogen can also be viewed as energy source and an intermediate towards the production of VFA (volatile fatty acids). VFA present in these effluents generated from H2 producing reactor can be further transformed to PHAs or can be used for biohydrogenation of fatty acids into alcohols. © 2011 Elsevier Inc. All rights reserved.
Adaptation of biohydrogen producing reactor to higher substrate load: Redox controlled process integration strategy to overcome limitations
Mohanakrishna G., Venkata Subhash G., Venkata Mohan S.
Article, International Journal of Hydrogen Energy, 2011, DOI Link
View abstract ⏷
Adaptation of acidogenic sequencing batch biofilm reactor (AcSBBR) to higher loading conditions of vegetable waste extract was studied during biohydrogen production at pH 6.0 under ambient conditions. H2 production rate (HPR) and cumulative H2 production (CHP) were found to improve with increase in organic load from 4.50 to 26.44 kg COD/m3 and later at 35.25 kg COD/m3 stabilization was observed. Acid metabolic intermediates production tends to lower the system pH which limits the substrate degradation and H2 production at higher loading conditions. To overcome these limitations, redox controlled strategy (pH 7.0) was applied by integrating another AcSBBR. Upon redox controlled integration, CHP and substrate degradation were found to improve by 42.81% and 36.82% respectively. This approach helped to maintain the favorable redox microenvironment for fermentation at higher VFA concentrations. This process integration methodology will help to overcome some persistent limitation observed during biohydrogen production and make the process sustainable especially with high strength waste/wastewaters. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Regulatory influence of CO2 supplementation on fermentative hydrogen production process
Devi M.P., Mohan S.V., Mohanakrishna G., Sarma P.N.
Article, International Journal of Hydrogen Energy, 2010, DOI Link
View abstract ⏷
This study presents an approach to enhance fermentative biohydrogen (H 2) production by improving the system buffering capacity through utilization of CO2 generated from syngas. The experimental data substantiates the positive impact of CO2 sparging on H2 production process. Various CO2 sparging times viz., 30, 60 and 120 s were evaluated on H2 production and substrate degradation. Based on the optimum sparging time (60 s), experiments were further performed to study the influence of pH microenvironment (5, 6 and 7) on the process efficiency. Further the influence of periodic CO2 sparging was also evaluated. Experimental data visualized a marked improvement on the overall process performance based on H2 production and substrate degradation after sparging CO2. Carbonic acid upon association/dissociation forms bicarbonates in the system. Alkaline condition helps to build up buffering nature, which resist fluctuations in pH even at higher VFA concentrations. Substrate degradation was effective during intermittent sparging at neutral conditions. CO2 sparging directly effecting the bulk liquid environment of the system improves buffering nature which indirectly helps to maintain favorable microenvironment for biohydrogen production process. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
Bio-catalyzed electrochemical treatment of real field dairy wastewater with simultaneous power generation
Venkata Mohan S., Mohanakrishna G., Velvizhi G., Babu V.L., Sarma P.N.
Article, Biochemical Engineering Journal, 2010, DOI Link
View abstract ⏷
Biologically catalyzed electrochemical treatment of real field dairy wastewater in association with power generation was studied in single chamber non-catalyzed microbial fuel cell (MFC, open-air cathode). The performance was evaluated at four organic loads employing anaerobic mixed consortia as anodic biocatalyst. Experimental data illustrated the integrated function of MFC to harness bioelectricity from the treatment of dairy wastewater. Along with good substrate degradation (chemical oxygen demand (COD), 95.49%), MFC also documented good removal of proteins (78.07%), carbohydrates (91.98%) and turbidity (99.02%). A steady increase in MFC performance was observed with increase in substrate load. Maximum volumetric power production (1.10W/m3; 308mV; 1.78mA) was observed at 4.44kgCOD/m3. MFC performance as power generator was characterized based on polarization behavior, cell potentials, cyclic voltammetric analysis and sustainable power estimation. In view of inherent advantages of the process, if optimized and understood well, this integrated approach can be a good replacement for the conventional biological and electrochemical wastewater treatment processes. © 2010 Elsevier B.V.
Bio-electrochemical treatment of distillery wastewater in microbial fuel cell facilitating decolorization and desalination along with power generation
Article, Journal of Hazardous Materials, 2010, DOI Link
View abstract ⏷
Microbial fuel cell (MFC; open-air cathode) was evaluated as bio-electrochemical treatment system for distillery wastewater during bioelectricity generation. MFC was operated at three substrate loading conditions in fed-batch mode under acidophilic (pH 6) condition using anaerobic consortia as anodic-biocatalyst. Current visualized marked improvement with increase in substrate load without any process inhibition (2.12-2.48. mA). Apart from electricity generation, MFC documented efficient treatment of distillery wastewater and illustrated its function as an integrated wastewater treatment system by simultaneously removing multiple pollutants. Fuel cell operation yielded enhanced substrate degradation (COD, 72.84%) compared to the fermentation process (∼29.5% improvement). Interestingly due to treatment in MFC, considerable reduction in color (31.67%) of distillery wastewater was also observed as against color intensification normally observed due to re-polymerization in corresponding anaerobic process. Good reduction in total dissolved solids (TDS, 23.96%) was also noticed due to fuel cell operation, which is generally not amenable in biological treatment. The simultaneous removal of multiple pollutants observed in distillery wastewater might be attributed to the biologically catalyzed electrochemical reactions occurring in the anodic chamber of MFC mediated by anaerobic substrate metabolism. © 2009 Elsevier B.V.
Ecologically engineered system (EES) designed to integrate floating, emergent and submerged macrophytes for the treatment of domestic sewage and acid rich fermented-distillery wastewater: Evaluation of long term performance
Venkata Mohan S., Mohanakrishna G., Chiranjeevi P., Peri D., Sarma P.N.
Article, Bioresource Technology, 2010, DOI Link
View abstract ⏷
An ecologically engineered system (EES) was designed to mimic the natural cleansing functions of wetlands to bring about wastewater treatment. EES consisted of three tanks containing diverse biota viz., aquatic macrophytes, submerged plants, emergent plants and filter feeders connected in series. The designed system was evaluated for 216 days by operating in continuous mode (20 l/day) to treat both sewage (DS) and fermented-distillery wastewater (FDW, from hydrogen producing bioreactor). Floating macrophyte system (Tank 1) was more effective in removing COD and nitrates. Submerged and emergent integrated macrophyte system (Tank 2) showed an effective removal of volatile fatty acids (VFAs) along with COD. Filter-feeding system (Tank 3) visualized the removal of COD, VFA, turbidity and color. On the whole the system can treat effectively DS (COD, 68.06%; nitrate, 22.41%; turbidity, 59.81%) and FDW (COD, 72.92%; nitrate, 23.15%; color, 46.0%). The designed EES can be considered as an economical approach for the treatment of both sewage and fermented wastewaters. © 2009 Elsevier Ltd. All rights reserved.
Utilizing acid-rich effluents of fermentative hydrogen production process as substrate for harnessing bioelectricity: An integrative approach
Article, International Journal of Hydrogen Energy, 2010, DOI Link
View abstract ⏷
Lower substrate degradation is one of the limiting factors associated with fermentative hydrogen production process. To overcome this, an attempt was made to integrate microbial fuel cell (MFC) as a secondary energy generating process with the fermentative hydrogen (H2) production. The acid-rich effluents generated from the acidogenic sequential batch biofilm reactor (AcSBBR) producing H2 by fermenting vegetable waste was subsequently used as substrate for bioelectricity generation in single chambered MFC (air cathode; non-catalyzed electrodes). AcSBBR was operated at 70.4 kg COD/m3-day and the outlet was fed to the MFC at three variable organic loading rates. The final outlet from AcSBBR was composed of fermentative soluble acid intermediates along with residual carbon source. Experimental data illustrated the feasibility of utilizing acid-rich effluents by MFC for both additional energy generation and wastewater treatment. Higher power output (111.76 mW/m2) was observed at lower substrate loading condition. MFC also illustrated its function as wastewater treatment unit by removing COD (80%), volatile fatty acids (79%), carbohydrates (78%) and turbidity (65.38%) effectively. Fermented form of vegetable wastewater exhibited higher improvement (94%) in power compared to unfermented wastewater. The performance of MFC was characterized with respect to polarization behavior, cell potentials, cyclic voltammetry and sustainable power. This integration approach enhanced wastewater treatment efficiency (COD removal, 84.6%) along with additional energy generation demonstrating both environmental and economic sustainability of the process. © 2010 Professor T. Nejat Veziroglu.
Composite vegetable waste as renewable resource for bioelectricity generation through non-catalyzed open-air cathode microbial fuel cell
Article, Bioresource Technology, 2010, DOI Link
View abstract ⏷
Single chambered mediatorless microbial fuel cell (MFC; non-catalyzed electrodes) was operated to evaluate the potential of bioelectricity generation from the treatment of composite waste vegetables (EWV) extract under anaerobic microenvironment using mixed consortia as anodic biocatalyst. The system was operated with designed synthetic wastewater (DSW; 0.98 kg COD/m3-day) during adaptation phase and later shifted to EWV and operated at three substrate load conditions (2.08, 1.39 and 0.70 kg COD/m3-day). Experimental data illustrated the feasibility of bioelectricity generation through the utilization of EWV as substrate in MFC. Higher power output (57.38 mW/m2) was observed especially at lower substrate load. The performance of MFC was characterized based on the polarization behavior, cell potentials, cyclic voltammetric analysis and sustainable resistance. MFC operation also documented to stabilize the waste by effective removal of COD (62.86%), carbohydrates (79.84%) and turbidity (55.12%). © 2009 Elsevier Ltd. All rights reserved.
Enhancing biohydrogen production through sewage supplementation of composite vegetable based market waste
Mohanakrishna G., Kannaiah Goud R., Venkata Mohan S., Sarma P.N.
Article, International Journal of Hydrogen Energy, 2010, DOI Link
View abstract ⏷
The function of domestic sewage supplementation as co-substrate with composite vegetable based market waste was studied during the process of fermentative hydrogen (H2) production. Significant improvement in H2 production and substrate degradation were noticed upon supplementing the waste with domestic sewage. Maximum H2 production (cummulative) was observed at 5.2 kg COD/m3 with pulp operation and 4.8 kg COD/m3 with non-pulp operation accounting for improvement of 51 and 55% respectively after sewage upplementation. Substrate degradation was also found to improve with respect to both carbohydrates [8% (with pulp); 5% (non-pulp)] and chemical oxygen demand [COD, 12% (with pulp); 13% (non-pulp)] after adding domestic sewage. Specific H2 yield improved especially at lower concentrations. Supplementation of waste with co-substrate helps to maintain good buffering microenvironment supports fermentation process and in addition provides micro-nutrients, organic matter and microbial biomass. Variation in the outlet pH was less in supplementation experiments compared to normal operation. © 2009 Professor T. Nejat Veziroglu.
Harnessing of biohydrogen by acidogenic fermentation of Citrus limetta peelings: Effect of extraction procedure and pretreatment of biocatalyst
Venkata Mohan S., Lenin Babu M., Venkateswar Reddy M., Mohanakrishna G., Sarma P.N.
Article, International Journal of Hydrogen Energy, 2009, DOI Link
View abstract ⏷
The extracts of Citrus limetta (sweet lime) peelings were evaluated as a fermentable substrate for hydrogen (H2) production by dark-fermentation (acidogenic) using both anaerobic mixed consortia and selectively enriched acidogenic mixed consortia. Extraction was carried by pretreating sweet lime peelings at 121 °C (1 bar pressure) at variable pH (6 and 7) and digestion time (20 and 40 min). Maximum organic matter extraction was observed at pH 7.0 (40 min). Fermentation was performed at different organic loading conditions [OL1, 1.17 kg COD/m3; OL2, 2.35 kg COD/m3; OL3, 4.69 kg COD/m3] under acidophilic microenvironment. H2 production was found to depend on the concentration of the substrate and composition. Increase in organic load showed consistent improvement in H2 production. Operation at OL3 employing selectively enriched inoculum documented higher cumulative H2 production (10.07 mmol) and H2 production rate (0.345 mmol/h) (pH 7; 40 min). Substrate degradation was also found to increase with increase in organic loading. Maximum substrate degradation (SD) was registered at pH 6 (40 min) with anaerobic culture (2.80 kg CODR/m3; ξCOD 31.82%) and at pH 7 (40 min) with selectively enriched acidogenic culture (3.20 kg CODR/m3; ξCOD 36.36%). Concentration of volatile fatty acids (VFAs) also improved with increase in organic load. Maximum VFA concentration (1098 mg/l) was observed with OL3 (pH 7; 40 min) by using selectively enriched culture. © 2009 International Association for Hydrogen Energy.
Optimization and evaluation of fermentative hydrogen production and wastewater treatment processes using data enveloping analysis (DEA) and Taguchi design of experimental (DOE) methodology
Mohan S.V., Raghavulu S.V., Mohanakrishna G., Srikanth S., Sarma P.N.
Article, International Journal of Hydrogen Energy, 2009, DOI Link
View abstract ⏷
The combined process efficiency with respect to fermentative hydrogen (H2) production and wastewater treatment was evaluated in a series of batch experiments to enumerate the role of selected factors viz., origin of inoculum, pre-treatment, inlet pH and feed composition under anaerobic microenvironment using mixed culture. H2 production and substrate degradation were found to depend significantly on the selected factors with individual conditions to achieve effective process performance. Significantly diverse operational conditions were observed for both H2 production and substrate degradation with respect to process efficiency. However, while dealing with H2 production in association with wastewater treatment, both the parameters are important and balancing the conditions for combined effective performance is critical. Data enveloping analysis (DEA) was applied to evaluate the combined system performance with respect to the two output parameters (H2 production and substrate degradation) based on relative efficiency. Among various experimental combinations studied, those with untreated anaerobic mixed inoculum under acidophilic conditions (inlet pH 5.5) using simple wastewater as fermentative substrate illustrated combined process efficiency with respect to H2 production (1.919 m mol H2/day; 0.52 mol H2/kg CODR-day) and substrate degradation (substrate degradation rate, 4.56 kg COD/m3-day). DEA methodology provide the relative efficiency of the system by integrating two output parameters. Further, design of experimental methodology (DOE) by Taguchi approach was applied to enumerate the role of selected factors on the H2 production and substrate degradation with the final aim of optimizing the process. By adapting the derived optimum conditions, the performance with respect to H2 production and substrate degradation could be enhanced by three fold. © 2008 International Association for Hydrogen Energy.
Evaluation of the potential of various aquatic eco-systems in harnessing bioelectricity through benthic fuel cell: Effect of electrode assembly and water characteristics
Venkata Mohan S., Srikanth S., Veer Raghuvulu S., Mohanakrishna G., Kiran Kumar A., Sarma P.N.
Article, Bioresource Technology, 2009, DOI Link
View abstract ⏷
Six different types of ecological water bodies were evaluated to assess their potential to generate bioelectricity using benthic type fuel cell assemblies. Experiments were designed with various combinations of electrode assemblies, surface area of anode and anodic materials. Among the 32 experiments conducted, nine combinations evidenced stable electron-discharge/current. Nature, flow conditions and characteristics of water bodies showed significant influence on the power generation apart from electrode assemblies, surface area of anode and anodic material. Stagnant water bodies showed comparatively higher power output than the running water bodies. Placement of cathode on algal mat (as bio-cathode) documented several folds increment in power output. Electron-discharge started at 1000 Ω resistance in polluted water bodies (Nacaharam cheruvu, Hussain Sagar lake Musi river), whereas, in relatively less polluted water bodies (Uppal pond/stream, Godavari river) electron-discharge was observed at low resistances (500/750 Ω). © 2008 Elsevier Ltd. All rights reserved.
Acidogenic fermentation of vegetable based market waste to harness biohydrogen with simultaneous stabilization
Mohan S.V., Mohanakrishna G., Goud R.K., Sarma P.N.
Article, Bioresource Technology, 2009, DOI Link
View abstract ⏷
Vegetable based market waste was evaluated as a fermentable substrate for hydrogen (H2) production with simultaneous stabilization by dark-fermentation process using selectively enriched acidogenic mixed consortia under acidophilic microenvironment. Experiments were performed at different substrate/organic loading conditions in concurrence with two types of feed compositions (with and without pulp). Study depicted the feasibility of H2 production from vegetable waste stabilization process. H2 production was found to be dependent on the concentration of the substrate and composition. Higher H2 production and substrate degradation were observed in experiments performed without pulp (23.96 mmol/day (30.0 kg COD/m3); 13.96 mol/kg CODR (4.8 kg COD/m3)) than with pulp (22.46 mmol/day (32.0 kg COD/m3); 12.24 mol/kg CODR (4.4 kg COD/m3)). Generation of higher concentrations of acetic acid and butyric acid was observed in experiments performed without pulp. Data enveloping analysis (DEA) was employed to study the combined process efficiency of system by integrating H2 production and substrate degradation. © 2009 Elsevier Ltd. All rights reserved.
Behavior of single chambered mediatorless microbial fuel cell (MFC) at acidophilic, neutral and alkaline microenvironments during chemical wastewater treatment
Veer Raghavulu S., Venkata Mohan S., Venkateswar Reddy M., Mohanakrishna G., Sarma P.N.
Article, International Journal of Hydrogen Energy, 2009, DOI Link
View abstract ⏷
Single chamber mediatorless microbial fuel cell (MFC; non-catalyzed graphite electrodes; open air cathode) behaviour was evaluated under different pH microenvironments [acidophilic (pH 6), neutral (pH 7) and alkaline (pH 8)] during chemical wastewater treatment employing anaerobic mixed consortia as anodic biocatalyst at room temperature (29 ± 2 °C). The performance was found to depend on the feed pH used. Higher current density was observed at acidophilic conditions [pH 6; 186.34 mA/m2; 100 Ω] compared to neutral [pH 7; 146.00 mA/m2; 100 Ω] and alkaline [pH 8; 135.23 mA/m2; 100 Ω]. On the contrary, substrate degradation was found to be effective at neutral pH conditions (ξCOD - 58.98%; SDR - 0.67 kg COD/m3-day) followed by alkaline (ξCOD - 55.76%; SDR - 0.62 kg COD/m3-day) and acidophilic (ξCOD of 47.80%; SDR 0.58 kg COD/m3-day) conditions studied. However, relatively higher specific power yield was observed at acidophilic microenvironment (46 mW/kg CODR) compared to neutral (35 mW/kg CODR) and alkaline (34 mW/kg CODR) conditions. The behaviour of the MFC was also evaluated employing electron discharge, cyclic voltammetry, cell potentials, Coulombic efficiency and sustainable power analysis. Acidophilic operation showed higher Coulombic efficiency and effective electron discharge at relatively higher resistance compared to neutral and alkaline conditions studied. © 2009 International Association for Hydrogen Energy.
Effect of anodic metabolic function on bioelectricity generation and substrate degradation in single chambered microbial fuel cell
Article, Environmental Science and Technology, 2008, DOI Link
View abstract ⏷
Influence of anodic metabolic function viz., aerobic, anoxic and anaerobic on bioelectricity generation was evaluated in single chamber mediatorless microbial fuel cells (non-catalyzed graphite electrodes; open-air cathode) during wastewater treatment under similar operating conditions (pH 7; ambient temperature/pressure). Despite the fluctuations observed, aerobic metabolic function (379 mV; 538 mA/m2) documented higher power generation compared to anoxic (251 mV; 348 mA/m2) and anaerobic (265 mV; 211 mA/m2) operations. Relatively higher treatment efficiency was also evidenced in aerobic operation (COD removal efficiency; 77.68% (aerobic), 56.84% (anoxic), 48.68% (anaerobic)). Polarization behavior, bioelectrochemical analysis, sustainable resistance and cell potentials also supported the aerobic operation. Aerobic metabolic function showed potential to generate higher power and substrate degradation over the corresponding anoxic and anaerobic metabolic functions. The relative efficiency of power generation observed in aerobic microenvironment might be attributed to effective substrate oxidation and good biofilm growth observed on the anodic surface. Presence of lower dissolved oxygen concentration in anodic chamber due to the establishment of equilibrium between substrate oxidation and oxygen scavenging might also contributes positively to power generation in aerobic operation. © 2008 American Chemical Society.
Harnessing of bioelectricity in microbial fuel cell (MFC) employing aerated cathode through anaerobic treatment of chemical wastewater using selectively enriched hydrogen producing mixed consortia
Venkata Mohan S., Mohanakrishna G., Srikanth S., Sarma P.N.
Article, Fuel, 2008, DOI Link
View abstract ⏷
The possibility of bioelectricity generation from anaerobic chemical wastewater treatment was evaluated in a microbial fuel cell (MFC) [dual-chambered; mediator less anode; aerated cathode; plain graphite electrodes] employing selectively enriched hydrogen producing (acidogenic) mixed culture. Performance of MFC was evaluated at two organic/substrate loading rates (OLR) (1.165 Kg COD/m3-day and 1.404 Kg COD/m3-day) in terms of bioelectricity production and wastewater treatment at ambient pressure and temperature under acidophilic microenvironment (pH 5.5) using non-coated plain graphite electrodes (mediatorless anode; air cathode). Experimental data demonstrated the feasibility of in situ bioelectricity generation along with wastewater treatment. The performance of MFC with respect to power generation and wastewater treatment was found to depend on the applied OLR. Maximum voltage of 716 mV (2.84 mA; OLR -1.165 kg COD/m3-day) and 731 mV (2.97 mA; OLR-1.404 kg COD/m3-day) was observed at stable operating conditions. Substrate degradation rate (SDR) of 0.519 Kg COD/m3-day and 0.858 Kg COD/m3-day was observed at two OLRs studied. Maximum power yield (0.73 W/Kg CODR and 0.49 W Kg/CODR) and current density (339.87 mA/m2 and 355.43 mA/m2) was observed at applied 50 Ω resistance. Fuel cell performance was evaluated employing polarization curve (100 Ω-30 KΩ), Coulombic efficiency (€cb) and cell potentials along with sustainable power yield at stable phase of fuel cell operation. Designed MFC configuration, adopted operating conditions and used parent inoculum showed positive response. © 2008 Elsevier Ltd. All rights reserved.
Integration of acidogenic and methanogenic processes for simultaneous production of biohydrogen and methane from wastewater treatment
Article, International Journal of Hydrogen Energy, 2008, DOI Link
View abstract ⏷
Feasibility of integrating acidogenic and methanogenic processes for simultaneous production of biohydrogen (H2) and methane (CH4) was studied in two separate biofilm reactors from wastewater treatment. Acidogenic bioreactor (acidogenic sequencing batch biofilm reactor, AcSBBR) was operated with designed synthetic wastewater [organic loading rate (OLR) 4.75 kg COD/m3-day] under acidophilic conditions (pH 6.0) using selectively enriched acidogenic mixed consortia. The resultant outlet from AcSBBR composed of fermentative soluble intermediates (with residual carbon source), was used as feed for subsequent methanogenic bioreactor (methanogenic/anaerobic sequencing batch biofilm reactor, AnSBBR, pH 7.0) to generate additional biogas (CH4) utilizing residual organic composition employing anaerobic mixed consortia. During the stabilized phase of operation (after 60 days) AcSBBR showed H2 production of 16.91 mmol/day in association with COD removal efficiency of 36.56% (SDRA-1.736 kg COD/m3-day). AnSBBR showed additional COD removal efficiency of 54.44% (SDRM-1.071 kg COD/m3-day) along with CH4 generation. Integration of the acidogenic and methanogenic processes enhanced substrate degradation efficiency (SDRT-4.01 kg COD/m3-day) along with generation of both H2 and CH4 indicating sustainability of the process. © 2008 International Association for Hydrogen Energy.
Bioelectricity generation from chemical wastewater treatment in mediatorless (anode) microbial fuel cell (MFC) using selectively enriched hydrogen producing mixed culture under acidophilic microenvironment
Venkata Mohan S., Mohanakrishna G., Reddy B.P., Saravanan R., Sarma P.N.
Article, Biochemical Engineering Journal, 2008, DOI Link
View abstract ⏷
Bioelectricity generation from composite chemical wastewater treatment was evaluated in a dual chambered microbial fuel cell (MFC) [anode chamber (mediatorless; perforated plain graphite electrode); cathode chamber (50 mM potassium ferricyanide [K3Fe(CN)6] in phosphate buffer; pH 7.5; plain graphite electrode)] inoculated with selectively enriched hydrogen (H2) producing mixed culture under acidophilic microenvironment (pH 5.5). Anode chamber, which resembles anaerobic suspended contact reactor was fed with wastewater and operated in absence of artificial mediator at acidic environment to proliferate H2 producing bacteria. Experimental data showed the feasibility of producing bioelectricity from wastewater treatment, though power production was found to be dependent on the substrate loading rate. Maximum voltage of 271.5 mV (5.43 mA) and 304 mV (6.08 mA) was recorded at operating organic loading rates (OLR) of 1.165 kg COD/(m3 day) and 1.404 kg COD/(m3 day), respectively when measured at 50 Ω external resistors at stable operating conditions. COD removal efficiency of 35.4% (substrate degradation rate (SDR) of 0.412 kg COD/(m3 day)) and 62.9% (SDR, 0.88 kg COD/(m3 day)) was observed at OLRs 1.165 kg COD/(m3 day) and 1.404 kg COD/(m3 day), respectively. Maximum specific power production of 0.163 W/kg CODR (1.165 kg COD/(m3 day); 50 Ω) and 0.198 W/kg CODR (1.404 kg COD/(m3 day); 100 Ω) was observed during stable phase of fuel cell operation. Current density of 747.96 mA/m2 (1.165 kg COD/(m3 day)) and 862.85 mA/m2 (1.404 kg COD/(m3 day)) was documented at 10 Ω. Utilizing chemical wastewater for the production of renewable energy (bioelectricity) from anaerobic treatment is considered as a feasible, economical and sustainable process. © 2007 Elsevier B.V. All rights reserved.
Bioelectricity production from wastewater treatment in dual chambered microbial fuel cell (MFC) using selectively enriched mixed microflora: Effect of catholyte
Venkata Mohan S., Saravanan R., Raghavulu S.V., Mohanakrishna G., Sarma P.N.
Article, Bioresource Technology, 2008, DOI Link
View abstract ⏷
The performance of aerated and ferricyanide catholytes on the bioelectricity production was evaluated in dual chambered microbial fuel cell (MFC) (mediatroless anode; graphite electrodes) employing selectively enriched H2 producing mixed consortia as anodic inoculum. Two MFCs with aerated catholyte (MFCAC) and ferricyanide catholyte (MFCFC) were operated separately to elucidate the difference in power generation potential and carbon removal efficiency under similar operating conditions [ambient pressure; room temperature (28 ± 2 °C); acidophilic microenvironment (pH 6)]. The experimental data demonstrated the feasibility of in situ bioelectricity generation along with wastewater treatment. Effective power generation and substrate removal efficiency was documented in the fuel cell operated with ferricyanide catholyte (586 mV; 2.37 mA; 0.559 kg COD/m3 day) than aerated catholyte (572 mV; 1.68 mA; 0.464 kg COD/m3 day). Maximum power yield (0.635 W/kg CODR and 0.440 W/kg CODR) and current density (222.59 mA/m2 and 190.28 mA/m2) was observed at 100 Ω resistor with ferricyanide and aerated catholytes, respectively. The study documented both wastewater treatment and electricity production through direct conversion of H2 in a single system. © 2007 Elsevier Ltd. All rights reserved.
Simultaneous biohydrogen production and wastewater treatment in biofilm configured anaerobic periodic discontinuous batch reactor using distillery wastewater
Venkata Mohan S., Mohanakrishna G., Ramanaiah S.V., Sarma P.N.
Article, International Journal of Hydrogen Energy, 2008, DOI Link
View abstract ⏷
Biohydrogen (H2) production with simultaneous wastewater treatment was studied in anaerobic sequencing batch biofilm reactor (AnSBBR) using distillery wastewater as substrate at two operating pH values. Selectively enriched anaerobic mixed consortia sequentially pretreated with repeated heat-shock (100 °C; 2 h) and acid (pH - 3.0; 24 h) methods, was used as parent inoculum to startup the bioreactor. The reactor was operated at ambient temperature (28 ± 2 {ring operator} C) with detention time of 24 h in periodic discontinuous batch mode. Experimental data showed the feasibility of hydrogen production along with substrate degradation with distillery wastewater as substrate. The performance of the reactor was found to be dependent on the operating pH. Adopted acidophilic microenvironment (pH 6.0) favored H2 production (H2 production rate-26 mmol H2/day; specific H2 production-6.98 mol H2/kg CODR-day) over neutral microenvironment (H2 production rate-7 mmol H2/day; specific H2 production-1.63 mol H2/kg CODR-day). However, COD removal efficiency was found to be effective in operated neutral microenvironment (pH 7-69.68%; pH 6.0-56.25%). The described process documented the dual benefit of renewable energy generation in the form of H2 with simultaneous wastewater treatment utilizing it as substrate. © 2007 International Association for Hydrogen Energy.
Self-immobilization of acidogenic mixed consortia on mesoporous material (SBA-15) and activated carbon to enhance fermentative hydrogen production
Mohan S.V., Mohanakrishna G., Reddy S.S., Raju B.D., Rao K.S.R., Sarma P.N.
Article, International Journal of Hydrogen Energy, 2008, DOI Link
View abstract ⏷
The influence of self-immobilization of enriched acidogenic mixed consortia on fermentative hydrogen (H2) production was studied on different supporting materials [SBA-15 (mesoporous) and activated carbon (granular; GAC and powder; PAC)] using chemical wastewater as substrate. Batch fermentation experiments were performed with same substrate at different organic loading rates (OLRs) under acidophilic microenvironment (pH 5.5) and room temperature (28 ±2°C). Experimental data evidenced the effectiveness of attached growth on both the H2 yields and substrate degradation efficiency, particularly at higher loading rates. Among the three materials evaluated, immobilization on SBA-15 material showed comparatively effective performance in enhancing both H2 yield and substrate degradation. Suspended growth (SG-control) culture showed inhibition in terms of both H2 production and substrate degradation especially at applied higher loading rates. Immobilization on SBA-15 resulted in nine times higher H2 production (7.29 mol/kg COD R-day at OLR of 0.83kg COD/m3-day) than the lowest yield observed (suspended growth at OLE of 2.55 kg COD/m3-day). Maximum substrate degradation rate (SDR) of 0.96 kg COD/m3-day (OLR 2.55 kg COD/m3-day) was also observed with SBA-15 immobilization, which is 1.62 times higher than the lowest substrate degradation observed with SG-control experiments with the same OLR. Attached growth on GAC and PAG also showed remarkable improvement in the process performance at higher OLRs compared to SG-control. © 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
Enhancing biohydrogen production from chemical wastewater treatment in anaerobic sequencing batch biofilm reactor (AnSBBR) by bioaugmenting with selectively enriched kanamycin resistant anaerobic mixed consortia
Mohan S.V., Mohanakrishna G., Veer Raghavulu S., Sarma P.N.
Article, International Journal of Hydrogen Energy, 2007, DOI Link
View abstract ⏷
The basic aim of this study was to investigate the feasibility of bioaugmentation strategy in the process of enhancing biohydrogen (H2) production from chemical wastewater treatment (organic loading rate (OLR)-6.3 kg COD/m3-day) in anaerobic sequencing batch biofilm reactor (AnSBBR) operated at room temperature (28 ± 2 °C) under acidophilic microenvironment (pH 6) with a total cycle period of 24 h. Parent augmented inoculum (kanamycin resistant) was acquired from an operating upflow anaerobic sludge blanket (UASB) reactor treating chemical wastewater and subjected to selective enrichment by applying repetitive/cyclic pre-treatment methods [altering between heat-shock treatment (100 °C; 2 h) and acid treatment (pH 3; 24 h)] to eliminate non-spore forming bacteria and to inhibit the growth of methanogenic bacteria (MB). Experimental data revealed the positive influence of bioaugmentation strategy on the overall H2 production. Specific H2 production almost doubled after augmentation from 0.297 to 0.483 mol H2/kg CODR-day. Chemical wastewater acted as primary carbon source in the metabolic reactions involving molecular H2 generation leading to substrate degradation. The augmented culture persisted in the system till the termination of the experiments. The survival and retention of the augmented inoculum and its positive effect on process enhancement may be attributed to the adopted reactor configuration and operating conditions. Scanning electron microscope (SEM) images documented the selective enrichment of morphologically similar group of bacteria capable of producing H2 under acidophilic conditions in anaerobic microenvironment. This depicted work corroborated successful application of bioaugmentation strategy to improve H2 production rate from anaerobic chemical wastewater treatment. © 2007 International Association for Hydrogen Energy.
