Hydrothermal Technologies for the Production of Fuels and Chemicals from Biomass

Biomass and non-food crop residues are seen as relatively low cost and abundant renewable sources capable of making a large contribution to the world's future energy and chemicals supply. Significant quantities of ethanol are currently produced from biomass via biochemical processes, but thermochemical conversion processes offer greater potential to utilize the entire biomass source to produce a range of products. This chapter will review thermochemical methods with a focus on hydrothermal liquefaction processes. Hydrothermal liquefaction is the most energetically advantageous thermochemical biomass conversion process. If the target is to produce sustainable liquid fuels and chemicals, and reduce the impact of global warming as a result of carbon dioxide, nitrous oxide, and methane emissions (i.e., protect the natural environment), the use of "green" solvents, bio catalysts and heterogeneous catalysts must be the main R&D initiatives. As the bio crude produced from hydrothermal liquefaction is a complex mixture which is relatively viscous, corrosive, and unstable to oxidation (due to the presence of water and oxygenated compounds), additional upgrading processes are required to produce suitable biofuels and chemicals.