Bio-jet Fuel via Fischer Tropsch Synthesis for Decarbonizing Aviation in the United States: Process Simulation, Economics and Scale-Up Analysis

Abstract

Decarbonizing the aviation sector will be crucial to meeting greenhouse gas (GHG) emissions reduction goals. Electrification, which is promising for decarbonizing road transport, is challenging for aviation. Given this limitation, one of the best options for decreasing CO2 emissions from aviation is the use of biomass-derived jet fuels, or bio-jet fuels. While not yet commercialized, one of the most promising pathways for the production of bio-jet fuel is the gasification of biomass followed by Fischer-Tropsch conversion of the gas to hydrocarbon fuels similar to petroleum derived fuels. Process performance, economics, carbon footprint and potential for scale- up of this pathway are analyzed here. An integrated gasification plus Fischer- Tropsch synthesis plant was designed and its performance was simulated using the chemical engineering software Aspen Plus. The design uses a pressurized, oxygen-blown, fluidized bed gasifier to gasify forestry residues, a potentially sustainable biomass source. The synthetic gas (syngas) is cleaned-up and conditioned to reach the appropriate specifications for conversion to a mixture of liquid hydrocarbons via Fischer-Tropsch synthesis. The crude Fischer-Tropsch product is hydrocracked and fractionated to produce two final product streams: synthetic paraffinic kerosene (SPK, a petroleum jet fuel equivalent) and naphtha. The plant designed processes 1 million tonnes/year of biomass (dry basis) to produce 818 thousand barrels of SPK and 205 thousand barrels of naphtha with an energy conversion efficiency of 42.7%. By capturing and storing byproduct CO2 generated during the process, production and use of the bio-jet fuel results in negative lifecycle GHG emissions. This translates to a reduction of over 209% in GHG emissions, compared with the production and use of petroleum jet fuel. Informed by mass and energy balances from the Aspen Plus simulation, the total fixed capital cost of the plant is estimated to be $1.2 billion with operating and maintenance costs of $67 million, annually. The resulting SPK levelized cost of fuel (LCOF) is $311/barrel (or $7.4/gallon), which far exceeds the wholesale price of petroleum jet fuel today. Capital and operating costs can be expected to decrease as experience in construction and operation accrue, but significant capital subsidies, renewable fuel credits, and/or carbon mitigation policies (as detailed in this study) would be needed to make initial projects economically viable. A single plant at the scale of the one designed here could supply somewhat less than 1% of the 2018 U.S. domestic jet fuel demand. If 30% of the biomass feedstocks projected by the US Department of Energy to be available in 2040 were used to produce bio-jet fuel, 74% of current U.S. demand could be met.