Strategies for use of novel, low value, heterogeneous feedstocks for production of fuels and chemicals

So-called “feedstock agnostic” processes are often discussed, but little research has actually been done in this area. It is critical, however, that biorefineries be able to handle multiple feedstocks, often with undesirable characteristics, because they are cheap and plentiful near the biorefinery. The University of Washington is investigating economically important candidate feedstocks, heterogeneous in physical and chemical nature, to develop strategies for biorefineries to handle such materials. Three novel feedstocks were studied: (1) 2-year-old hybrid poplar trees; (2) mixed biomass composed of sugarcane straw and bagasse; (3) mixed biomass composed of hybrid poplar and wheat straw. Each was evaluated for sugar production via steam pretreatment and enzymatic hydrolysis.

Results of the project show that there can be substantial benefits in having mixed biomass feedstocks. Surprisingly, when compared to a single feedstock, mixed biomass exhibited greater sugar recovery after pretreatment. For example, on average 14% more sugars were recovered using mixed hybrid poplar and wheat straw than either single biomass. For all the novel biomass tested, due to the higher sugar recoveries after saccharification and lower cost compared to single feedstock, the mixed feedstocks present a great economic potential in the bioconversion process. For example, for the hybrid poplar and wheat straw mixtures, ethanol production cost was on average 17% less expensive than when using single biomass. Results of the processing research were used to develop life cycle assessments (LCA) for the candidate feedstocks. The LCA results and the challenges and opportunities of harvesting and processing novel biomass will be discussed.