Process analysis and techno-economic comparison of aviation biofuel production via microbial oil and ethanol upgrading

• Advances in SAF production using TAGs and ethanol as intermediates. • Ethanol-to-jet most cost-effective: 63% SAF yield and 33% carbon utilization. • Jet fuel minimum selling price: 1.24€/l in best scenario (SUG-ATJ). • Syngas fermentation pathways: energy self-sufficient via H 2 and heat recovery. • Carbon losses occur primarily in off-gases and lignin residues. The transport sector is the largest source of greenhouse gases in the EU after the energy supply one, contributing approximately 27% of total emissions. Although decarbonization pathways for light-duty transport are relatively well established, heavy-duty transport, shipping and aviation emissions are difficult to eliminate through electrification. In particular, the aviation sector is strongly dependent on liquid hydrocarbons, making the development of sustainable aviation fuels (SAFs) a critical priority for achieving long-term climate targets. This study evaluates four biomass-to-liquid pathways for producing jet-like SAF from lignocellulosic biomass: (1) triacylglycerides (TAGs) production from syngas fermentation, (2) TAGs production from sugar fermentation, (3) ethanol production from syngas fermentation, and (4) ethanol production from sugar fermentation. These pathways are simulated using Aspen Plus™, and the mass and heat balances obtained are used to assess their technical performance (e.g., carbon utilization, energetic fuel efficiency) and techno-economic viability (e.g., production cost, capital investment). Pathway (4) demonstrated the highest jet fuel selectivity (63%) and total carbon utilization (32.5%), but at higher power demands. Pathway (1) was self-sufficient in energy due to internal syngas utilization but exhibited lower carbon efficiencies. Cost analysis revealed that microbial oil-based pathways were restrained by higher hydrogen demands and lower product selectivity compared to ethanol-based routes. However, with advancements in microbial oil production efficiency and reduced water usage, these pathways could become competitive.