The role of direct air carbon capture in decarbonising aviation

Aviation is the most energy and carbon intensive mode of transport and the most difficult to decarbonise. Greenhouse gas emissions from aviation comprise around 2 % of global totals. The low energy density of current battery technologies presents significant technical challenges for use in the aviation sector. This study compares two use cases of direct air carbon capture to decarbonise aviation, from an economic and environmental perspective. The first is where continued use of fossil jet fuel is offset by capturing and sequestering CO2 from the atmosphere. The second is where CO2 captured from the atmosphere is used as a feedstock, in conjunction with hydrogen from electrolysis, to produce a synthetic jet fuel. Depending on input parameters such as electricity cost and plant capacity factor, the levelised cost of carbon capture and storage falls between €160/tCO2 to over €1300/tCO2, while the cost of synthetic fuel production falls between €2/kg of fuel and €12/kg of fuel. Due to the high electricity inputs for hydrogen production, the use of direct air capture to produce a synthetic jet fuel results in 9.8 times more greenhouse gas emissions than sequestering it for a given electricity emissions intensity. The results presented in this study indicate that offsetting continued fossil jet fuel use using direct air capture has the lowest cost of abatement but there are overall sustainability concerns surrounding this pathway. Furthermore, the estimated cost increases associated with decarbonisation may indicate that the age of low-cost flying will not persist in a net-zero future.