Life Cycle Analysis of Electrofuels: Fischer–Tropsch Fuel Production from Hydrogen and Corn Ethanol Byproduct CO₂

Abstract

Electrofuels from renewable H₂ and waste CO₂ streams are of increasing interest because of their CO₂ emissions reduction potentials compared to fossil counterparts. This study evaluated the well-to-wheel (WTW) greenhouse gas (GHG) emissions of Fischer-Tropsch (FT) fuels from various electrolytic H₂ pathways and CO₂ sources, using various process designs (i.e., with and without H₂ recycle) and system boundaries. Two systems with different boundaries were considered: a stand-alone plant (with CO₂ from any source) and an integrated plant with corn ethanol production (supplying CO₂). The FT fuel synthesis process was modeled using Aspen Plus, which showed that 45% of the carbon in CO₂ can be fixed in the FT fuel, with a fuel production energy efficiency of 58%. Using nuclear or solar/wind electricity, the stand-alone FT fuel production from various plant designs can reduce WTW GHG emissions by 90-108%, relative to petroleum fuels. When integrating the FT fuel production process with corn ethanol production, the WTW GHG emissions of FT fuels are 57-65% lower compared to petroleum counterparts. This study highlights the sensitivity of the carbon intensity of FT fuels to the system boundary selection (i.e., stand-alone vs integrated), which has different implications under various GHG emission credit frameworks.