(164e) CELF Pretreatment of Cellulosic Biomass Achieves High Yields of Reactive Intermediates for Biological or Catalytic Conversion to Fuels and Chemicals

Although petroleum price spikes and shortages and air pollution have historically motivated biofuels research and development, it is more important than ever to capitalize on the low carbon footprint of cellulosic fuels to reduce carbon dioxide emissions that cause climate change. However, although cellulosic biomass such as agricultural and forestry residues and herbaceous and woody energy crops can be competitive in price with oil at about $20/barrel, the natural recalcitrance of biomass to breakdown into intermediates for fuels production presents a significant cost barrier, particularly at currently low petroleum prices. Our UCR team recently invented a novel pretreatment that employs renewable tetrahydrofuran (THF) as a co-solvent in aqueous solution with dilute sulfuric acid to effectively overcome biomass recalcitrance. This Co-solvent Enhanced Lignocellulosic Fractionation (CELF) technology can be tuned to achieve high yields of separate streams of most of the hemicellulose sugars and lignin, and solids highly enriched in cellulose. Recovering highly volatile THF for recycle from the CELF liquid precipitates nearly pure low molecular weight lignin with promise to be highly suitable for upgrading into fuels, chemicals, and materials. The cellulose fraction is amenable to breakdown into glucose with high yields at very low enzyme loadings and supports ethanol production at high titers, while consolidated bioprocessing (CBP) with the bacterium Clostridium thermocellum solubilizes virtually all of the cellulose in less than 2 days without adding enzyme. Furthermore, recombinant yeast has proved highly effective in fermenting the pentose and hexose sugars left in the liquid from CELF pretreatment after lignin recovery into ethanol. Alternatively, application of more severe CELF reaction conditions can realize high yields of the fuel precursors furfural, 5-hydroxymethylfurfural, and levulinic acid for catalytic conversion into fuels and chemicals.