Life cycle assessment of the biofuel production from lignocellulosic biomass in a hydrothermal liquefaction – aqueous phase reforming integrated biorefinery

The use of biofuels in the transport sector is one of the strategies for its decarbonization. Here, the LCA methodology was used for the first time to assess the environmental impacts of a biorefinery where hydrothermal liquefaction (HTL) and aqueous phase reforming (APR) were integrated. This novel coupling was proposed to valorize the carbon loss in the HTL-derived aqueous phase, while simultaneously reducing the external H2 demand during biocrude upgrading. Corn stover (residue) and lignin-rich stream (waste) were evaluated as possible lignocellulosic feedstocks. The global warming potential (GWP) was 56.1 and 58.4 g CO2 eq/MJbiofuel, respectively. Most of the GWP was attributable to the electrolysis step in the lignin-rich stream case and to the thermal duty and platinum use in the corn stover case. Other impact categories were investigated, and an uncertainty analysis was also carried out. A sensitivity analysis on biogenic carbon, electricity/thermal energy source and alternative hydrogen supply was conducted to estimate their influence on the GWP. Finally, the two scenarios were compared with the environmental impact of fossil- and other biomass-derived fuels, also considering fuel utilization. HTL-APR allowed a 37% reduction compared to fossil diesel, further reduced to 80% with the lignin-rich stream when green energy was used.