A sustainable aviation fuel pathway from biomass: life cycle environmental and cost evaluation for dimethylcyclooctane jet fuel

Abstract

Biomass is a promising renewable feedstock for conversion to sustainable aviation fuel (SAF) to mitigate near-term greenhouse gas (GHG) emissions. Through metabolic engineering, sugars derived from pretreated and hydrolyzed cellulose and hemicellulose can be directly fermented to isoprene and catalytically upgraded to 1-4-dimethylcyclooctane (DMCO), an environmentally beneficial and high performance alternative to petroleum-based jet fuel. Cellulosic sugars may allow for greater GHG emission reduction compared to first generation sugars and meet scaling needs to reduce dependence on petroleum-based kerosene. Here, we assess the environmental impact and economic feasibility of utilizing direct isoprene fermentation from residual biomass sugars as an intermediate step in the production of DMCO via life cycle assessment (LCA) and techno-economic analysis (TEA). We use chemical process modeling to simulate the conversion of sugars from biomass to isoprene, dimerization to dimethylcyclooctadiene (DMCOD) and catalytic hydrotreatment to DMCO. The bottom-up process model serves as the basis for constructing the life cycle inventory to assess environmental impacts and to predict economic feasibility. Results show a GHG intensity of 7.2 gCO₂e MJ⁻¹ that is significantly lower than that of current petroleum jet (89 gCO₂e MJ⁻¹) when using Zea mays L. residue (corn stover) as feedstock. The TEA indicated that the target costs have the potential to be competitive with a minimum fuel selling price of DMCO between $1.01 and $1.32 per L. Direct fermentation of isoprene could improve the overall process efficiency and reduce energy consumption, while also enhancing the environmental sustainability of the process.