Thermochemical conversion technologies have recently played a significant role in converting energy from waste sources. Thermochemical technologies have promisingways of recycling energy from variouswastematerials while reducing the environmental impact. This chapter primarily provides the collective information on waste feedstocks used for the thermochemical conversion from the recent review literature. Second, the numerous thermochemical conversion methods are discussed, including direct combustion, pyrolysis, gasification, and hydrothermal liquefaction using various reactors for each technique. It assesses the conversion of multiple wastes to crude bio-oil and the likelihood of converting syngas to biooil. Hydrothermal conversions occur at moderate temperatures, but typically at high pressure and in the presence of water. The thermochemical conversion includes the accurate temperature, pressure, and heating rate, which can be accomplished using various reactors. For the large-scale industrialization of biofuels, a greater understanding of the mechanism of conversion, reactors, and feedstock composition is crucial.Moreover, this chapter discusses the various thermochemical conversions of wastes and its bio-oil yield.