Chapter 2 - Development of Second-Generation Biorefineries

Abstract

A wide range of nonfood biomass and conversion technologies can be used for the production of bioenergy and biobased products. The fermentation of lignocellulosic-derived sugars and the thermochemical conversion of biomass (eg, fast pyrolysis) are examples of relevant conversion technologies. The main product of fast pyrolysis is bio-oil, which can be used directly in stationary boilers or after upgrading as a drop-in blend component in existing refineries. Bio-oil requires chemical upgrading, before it is suitable as fuel. The commercial use of bio-oil for material/chemical purposes is currently limited to minor food uses (ie, smoke aroma and flavor enhancers). Different pretreatment technologies can be used in the initial conversion of biomass to sugars for fermentation. Technical obstacles in those pretreatment processes differ among the various approaches, but can include insufficient separation of cellulose and lignin, formation of byproducts that inhibit downstream fermentation, high use of chemicals and/or energy, as well as high costs for cellulase enzymes, although the latter has decreased substantially in recent years. There is currently no consensus on a preferred pretreatment method or combination of methods. A wide range of biofuels and biobased chemicals can be produced from sugars via fermentation and/or chemical conversion, including advanced biofuels and chemical intermediates. The integration of different pretreatment and conversion technologies in biorefineries can maximize the use of biomass components and improve the efficiency of the entire value chain. In the mid- to long term, thermochemical and biochemical conversion of lignocellulosic biomass are promising technologies for the production of biofuels and biobased chemicals.