Techno-economic and greenhouse gas analyses of lignin valorization to eugenol and phenolic products in integrated ethanol biorefineries

This work presents techno-economic and greenhouse gas (GHG) analyses of an ethanol biorefinery integrating lignin conversion into eugenol and other phenolics. Catalytic hydrogenolysis assisted by isopropanol (IPA) is used to convert the lignin recovered after ionic liquid (IL) pretreatment, saccharification, and fermentation. This process was compared to a biorefinery using lignin for energy generation and simulated in SuperPro Designer. Spatial analysis was performed to determine biorefinery locations and capacities in a Mexican state with potential for lignocellulosic biomass, including corn stover, sorghum stubble, and Jatropha fruit shells. Relative to the base case, diverting 50% of lignin to phenolics decreased the ethanol cost of production significantly due to the high market value of the co-products. The minimum ethanol selling price (MESP) for this case was $2.02 gal(-1). The resulting cradle-to-gate GHG footprint of bioethanol was 21 g CO2-eq MJ(-1), a 78% reduction with respect to gasoline when system expansion is used for allocation. Using market value-based allocation resulted in 82% GHG reduction. Analysis of scenarios showed that a biorefinery processing 3000 t day(-1) biomass and diverting 80% of lignin to phenolics can potentially yield an MESP lower than $1.5 gal(-1). To achieve this, research should target a reduction in IL input by 30% and IPA input by 40%, together with more energy-efficient separation processes. The reduction in IL and IPA can be achieved by decreasing their loading rates and increasing recycling. Sensitivity analysis showed that, for biomass prices higher than $45 t(-1), biorefinery capacities must exceed 5000 t d(-1) biomass input. (c) 2019 Society of Chemical Industry and John Wiley & Sons, Ltd