Thermochemical conversion processes remained largely unexplored until relatively recent despite their important involvement in catalysis.14,15 Catalytic cracking and/or pyrolysis of vegetable oils and biomass were, until very recently, the most common thermochemical processes for the production of fuels and high — added-value chemicals. Lately, other key thermochemical processes have joined these promising technologies, in particular for the production of biofuels. These mostly include a variety of technologies such as biomass gasification to bio­syngas and other biofuels via hydrothermal upgrading (HTU), reforming and/or synthetic pathways (Fischer-Tropsch synthesis [FTS]), production of bioalcohols from biomass gasification, and so on.7

Several feedstocks can be employed in these processes, from virgin vegetable oils (e. g. palm, canola, soybean, etc.) for catalytic cracking to waste oils and fats as well as all different types of biomass, including residual oils, sewage sludge, organic and/or agricultural waste, black liquor and many others.7 The use of the feedstock is highly dependent on the process and the biofuel to be obtained (e. g. steam reforming and HTU biofuels can be prepared from either dry or wet biomass, irrespectively).

Thermochemical conversion processes and technologies are largely complex and varied. They will be fully described in Part IV of the book (Chapters 12-20), so we refer the readers to these chapters for more information.