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Substitution of fossil kerosene with sustainable aviation fuels (SAFs) is a key instrument for reducing greenhouse gas (GHG) emissions in the aviation industry and achieving the sector’s climate targets. Today, purely biomass- or electricity-based SAF production pathways are discussed. However, combining both approaches offers potential advantages, especially in terms of carbon utilization and product maximization. Thus, the goal of this paper is to carry out a techno-economic analysis of two hybrid processes that combine both biomass- and electricity-based production processes and can thus directly utilize the CO2off-gas that inevitably occurs in the biomass-based process. The investigated process pathways are characterized by the biogenic intermediates being ethanol and biogas. The respective pathways are analyzed and compared in terms of technical (carbon and energy efficiency) and economic (kerosene production costs) indicators based on steady-state process simulation. These investigations show that although the process using ethanol is more efficient in terms of carbon utilization, it has a higher specific energy requirement for the target product kerosene than the biogas-based process. In both processes, the carbon and energy efficiency are below 30%, partly due to the unused carbon and energy of the solid residue, which cannot be biochemically converted. Despite the differences in process technology, both processes can achieve approximately the same kerosene production costs of 2775 €2022/tKero. The addition of the electricity-based process results in significantly increasing production costs resulting from the investments in electrolyzers and the cost of renewable electricity. However, carbon efficiency and product generation can be increased by 13% points in terms of total hydrocarbon production compared to those of a purely biomass-based production.

In order to achieve the goal of limiting global warming to 1.5 °C, also the growing aviation industry needs to take measures to reduce their greenhouse gas emissions. Various renewably sourced aviation fuels can significantly reduce greenhouse gas emissions and most of them, except for example liquid hydrogen or LNG, can be used in the existing infrastructure without airport or aircraft modifications. As most of these renewably sourced fuel types are not (yet) produced at commercial scale, many technological assessment parameter (e.g. carbon or energy efficiency) are uncertain. Thus, the goal of this study is to compare two different process routes, both being based on biochemical and thermochemical conversion steps. The processes evaluated against conversion efficiency of the available raw feedstock and process energy requirements. The evaluation uses theoretical and biochemical carbon efficiency as well as energy efficiency as indicators. A steady-state flowsheet simulation for two biogenic process paths via biogas and bioethanol as intermediate products is carried out on the basis of literature data. In addition, the optional use of solid residue from the biotechnological process step by combustion for direct heat supply cases are studied. In the ethanol-based route, about 23% of the carbon in the feed can be recovered as kerosene, whereas this is only about 19% in the biogas route. Simultaneously, the ethanol-based route without the combustion of the residue has an energy efficiency of 28%, while the biogas route has an efficiency of 24%.