Circular fuel supply for air transport via negative emission HTL conversion

Achieving climate neutrality in Europe requires large volumes of truly sustainable fuels to provide long-term solutions for transport sectors where direct electrification is not viable. CIRCULAIR addresses this challenge with an integrated biofuel pathway that produces cost-effective aviation fuels and generates negative emissions. Key innovations of CIRCULAIR involve a close thermal coupling of hydrothermal liquefaction (HTL) conversion, based on abundant and available agricultural residues and lignocellulosic crops, with exothermic wet oxidation of HTL process water. In this way, autothermal operation can be achieved, carbon is fully utilized, and the process water disposal problem of HTL is solved. In addition, CIRCULAIR develops innovative approaches to upgrade HTL biocrudes to jet fuel and accelerates the approval of HTL fuels for civil aviation. The biomass resource utilization is maximized by developing valorisation schemes for all relevant side streams along the process chain. In particular, acetic acid will be extracted from residual process waters and methanol will be synthesized from effluent gas streams and renewable hydrogen. Importantly, CIRCULAIR will close a knowledge gap regarding the utilization of fixed carbon in the HTL solids for carbon sequestration and soil amendment, i.e. for a negative contribution to the carbon balance. The targeted overall net-negative emission will be quantified based on life cycle analysis. Finally, techno- and socio-economic analyses will identify important benefits and trade-offs associated with the advanced biofuel process.

In summary: CIRCULAIR will investigate and develop an innovative process for resource-efficient production of sustainable aviation biofuels alongside further marketable renewable chemicals and fuel products. The utilization of biomass feedstock that is abundant in agricultural environments ensures cost-efficiency, relevant scale and the potential to create net-negative carbon emissions.