Techno-Economic and Life Cycle Assessment of Jet Fuel Production through various Fischer Tropsch Pathways

The activity of the aviation sector accounts for at least 2% of the worldwide anthropogenic Green-House-Gas (GHG) emissions, while in the UK it represents 7%. Several practises have been proposed in order to diminish these emissions, among them, the use of sustainable aviation fuels (SAF) appears to be the most relevant global warming mitigation strategy for the aviation industry. However, the choice of feedstock and conversion technology have a direct impact on the economic, and environmental performance of the SAF. There is a great variety of processes for the production of SAF, from which the Fischer-Tropsch (FT) technology has achieved high maturity. Despite its level of development, the production and use of SAF will not be fully deployed until technical, economic and environmental constraints are properly addressed.
An extensive and critical literature review of techno-economic assessment (TEA) and/or life cycle assessment (LCA) studies for FT-derived SAF identified some important research gaps. Although some studies evaluated the production of SAF, there exists a lack of combined TEA and LCA approach. Furthermore, most of these studies did not include the synthetic crude oil processing steps within the boundaries of the system, which results in different economic and environmental estimates. Additionally, this is the first study to include CCS for the production of SAF. Consequently, to tackle the techno-economic and environmental uncertainties, this project aimed at evaluating the production of SAF through three scenarios based on the FT pathway, with different feedstocks and/or process configurations: i) Biomass to liquids, with and without carbon capture and storage (CCS); ii) Power to Liquids; iii) Power and Biomass to Liquids without and with CCS. For each scenario, detailed Aspen Plus process models and deterministic and probabilistic TEA and LCA estimated technical, economic and environmental indicators. Additionally, this study also included an evaluation of the effect of the “UK SAF mandate” on the SAF’s economic feasibility, making it the first study to apply this policy.
The results suggest that, regardless the scenario, the minimum jet fuel selling price (MJSP) of the SAF produced through the investigated processes cannot break even the gate price of the fossil jet fuel. Each pathway could achieve significant cost reductions through the reduction of CAPEX and/or lower feedstock and energy costs. The estimated global warming potential (GWP) demonstrated considerable emissions reductions for all scenarios when compared to fossil jet fuel, and even negative emissions were obtained for the scenarios with CCS. The water footprint, on the other hand, reflected larger water consumptions than those required for the production of conventional jet fuel. Given that policies such as the SAF mandate is a function of the GWP, the produced SAFs could benefit from economic incentives that could boost their economic feasibility and aid their MJSPs to break even on the fossil jet fuel gate price.