Sustainable aviation fuel from Kraft lignin – Technical, economic and ecological process analysis

Molten salt supported catalytic depolymerisation of lignin is an attractive option for the production of sustainable aviation fuel, exploring lignin’s high content of aromatic hydrocarbons. The European project ‘ABC-Salt’ developed a concept involving in-situ hydropyrolysis in salts and catalytic hydrodeoxygenation to obtain middle distillates from Kraft pulp mill lignin. This study evaluates the technical, economic and ecological viability of the proposed power-and-biomass-to-liquid process and its integration into the lignin providing pulp mill via a comprehensive techno-economic assessment (TEA) and life cycle assessment (LCA). The process analysis indicates a very high carbon efficiency of 78 % and an energy efficiency of 52.5 %LHV. The net production cost amounts to 1.66 €2020/lFuel with lignin as the highest cost contributor. Lignin is also the biggest contributor to a majority of environmental impacts, which increases the importance of the selected allocation method for lignin extraction at the pulp mill. In dependence of the allocation method, global warming potential savings range between 72 and 89 %, while major impact increases compared to fossil jet fuel occur in categories like water use, land use, minerals and metals resource depletion or freshwater eutrophication. Since hydrogen is essential for deoxygenation of the fuel, recovery of unused hydrogen is a key parameter for TEA and LCA results. The lowest cost and environmental impacts can be found for hydrogen recovery rates between 95 and 98 %. Finally, based on both TEA and LCA, currently a CO2 price of around 500 €/tCO₂-eq. would be necessary in order to produce cost competitive jet fuel.