Within BioSFerA, the technologies comprising the overall biomass-to-liquid (BtL) process chain, i.e. biomass gasification and gas cleaning, syngas conversion to microbial oil via two-step fermentation, and lipid hydroprocessing, were initially tested and optimized at a small scale (TRL 3) and subsequently developed and validated at pilot scale (TRL 5). Six different types of biogenic residues and wastes were gasified, and the resulting syngas streams were confirmed to be suitable for gas fermentation, as the bacterial strains used for acetate production demonstrated resistance to syngas contaminants. As a result, fewer gas cleaning steps are required compared to thermocatalytic pathways such as Fischer-Tropsch synthesis. The successful integration and piloting of the gasification and gas fermentation units were accomplished, achieving an acetate production rate of up to 0.77 g/L/h. Three different substrates (acetate, glucose, and glycerol) were tested for lipid production, with rates reaching up to 0.261 g/L/h. It was validated that no intermediate acetate purification is required prior to liquid fermentation, enabling the direct transfer of the first broth to the second reactor. Steam explosion was identified as an efficient method for lipid extraction, contributing to the energy and capital requirements at the downstream processing section. Hydroprocessing tests resulted in the production of 1 barrel of jet fuel and 1 barrel of marine diesel fuel. The diesel fraction can be considered a high-quality bunker fuel or used as an additive to enhance commercial marine diesel. Most of the measured properties of the jet fuel fraction comply with Jet A-1 specifications, except for the freezing point. Process simulations indicated an energy efficiency of 35.6% of the entire system at industrial scale and a total carbon utilization of 25.4% for advanced biofuels production. As part of the techno-economic analysis conducted within the project, the minimum selling price of jet fuel was estimated at 1.83 €/L, highlighting the cost-effectiveness and competitiveness of the BioSFerA concept. Additionally, a life cycle analysis demonstrated the lowest carbon footprint among all cases examined, at 15.5 g CO2eq/MJ, with estimated GHG emission savings ranging from 48% to 86% compared to conventional fossil fuels. Overall, the results achieved during the project were disseminated through 28 events, including conferences and exhibitions. Key outcomes have been detailed in 8 peer-reviewed scientific publications.
