(423a) Economic and Environmental Analyses of Hybrid Biochemical and Thermochemical Conversion of Lignocellulosic Feedstock to Synthetic Aviation Fuel

Herbaceous lignocellulosic feedstocks represent the largest individual category of potential biomass resources that are currently available but unutilized, totaling 143 MM dt/y. Hydrocarbon fuel production from lignocellulosic biomass hydrolysate via biochemical conversion has been widely explored but cost-effective valorization of the residual lignin fraction (beyond usage for heat and power) remains a technical challenge.

In this study, a hybrid biochemical and thermochemical conversion process is designed and evaluated to maximize the waste lignin utilization and minimize the production cost of synthetic aviation fuel (SAF). The process involves deacetylation and mechanical refining of corn stover feedstock followed by enzymatic hydrolysis, with clarified hydrolysate sent to aerobic sugars-to-lipids bioconversion via oleaginous yeast. Lipid-rich bioreactor effluent is sent to a relatively simple hydrothermal liquefaction (HTL) operation, avoiding downstream lipid separation while increasing biocrude yields in HTL and importantly, enabling concurrent processing of the residual black liquor and insoluble lignin streams in the combined HTL feed. Resultant biocrude undergoes hydroprocessing and fractionation to produce primarily jet-range hydrocarbon fuel. The increased feedstock carbon efficiency and corresponding >2x fuel production volume of this hybrid design compared to the biochemical-only approach addresses the growing demand for SAF while utilizing abundant domestic lignocellulosic resources. Process simulation, techno-economic and life cycle assessment are conducted to assess process viability for a site-specific design basis.