Biofuels for Aviation

Paraffinic Kerosene fuels are the backbone of commercial air travel. Kerosene fuels are primarily derived from petroleum processing and contribute significantly to carbon emissions globally. A variety of processes have been proposed to create renewable or semi-renewable sources of kerosene fuel suitable for aviation. One such process outlined in a 2019 white paper published by Gevo proposes the use of bio-based alcohol feed stocks to produce isobutanol which may be converted to kerosene mixtures through well-established dehydration and oligomerizations processes. The proposed Alcohol to Jet Fuel Pathway (ATJ-SPK) is a potentially net carbon neutral process which can greatly reduce the emissions generated by commercial air travel. The pathway would also allow airlines to integrate green Synthetic Paraffinic Fuel technology without expensive overhaul of existing fleets to accommodate new fuel sources, or research currently infeasible electric air travel (Gevo, 2019). A plant was designed around the use of a Nickel-FM catalyst to convert feedstocks of ethanol and methanol to isobutanol via the Guerbet chemistry pathway (Olson et al., 2004). Due to the presence of side reactions and excess methanol feed, distillation and liquid-liquid separation were proposed as methods of delivering an isobutanol-water mixture to the downstream dehydration and oligomerization steps. The economics of the downstream processes are estimated and included in the profitability analysis along with a detailed estimation of the isobutanol production step. Selling the fuel product at market price was not found to be profitable; however, if a green premium of 4.55x is applied to the product fuel price the plant is 2 both technically and economically feasible. With the green premium levied on the price of the product fuel the Internal Rate of Return (IRR) is 15%, with a Net Present Value (NPV) of $51.7 MM, and a third year Return on Investment (ROI) of 13.58%. Significant market research is needed to assess the viability of the green premium that must be levied on the fuel price to yield a reasonable return. It may be the case that it is currently inadvisable to invest in the proposed plant but may become advisable in the coming years as consumer and regulatory awareness begins to grow over the environmental impacts of air travel