Life cycle carbon, energy, and water impacts of isobutanol and sustainable aviation fuel from pea starch

The rapid expansion of plant-based food markets has increased the importance of pea protein production in the food industry, while generating large quantities of pea starch as a low-value co-product. Pea starch is currently used in applications such as animal feed, but these outlets may be insufficient to absorb increasing co-product volumes. Improving pea processing systems requires identifying higher-value and lower-impact applications for this starch, and converting it into isobutanol (IBA) and sustainable aviation fuel (SAF) offers such an outlet while serving aviation, a sector expected to continue relying on liquid fuels to meet increasing demand. This study presents a life cycle assessment of U.S. pea starch-derived IBA and SAF covering the full life cycle, including pea cultivation, protein-starch fractionation, and fuel production. Carbon intensity (CI), fossil energy consumption, and water consumption are quantified. To evaluate the influence of separation technology, IBA purification is modeled using conventional distillation and membrane solvent extraction, with the latter as an alternative designed to reduce process heat demand. Results show that agricultural impacts are primarily driven by nitrogen fertilizer production and N 2 O emissions from soil, while energy requirements dominate CI and fossil energy consumption in downstream stages. Replacing distillation with a membrane system reduces natural gas demand, resulting in a 43 % decrease in CI, and a 51 % reduction in fossil energy use for IBA relative to gasoline (52.1 vs 92.1 gCO 2 e/MJ and 0.59 vs 1.22 MJ/MJ, respectively). These improvements are associated with lower thermal energy requirements and credits from renewable natural gas generated from process waste streams. Compared with conventional jet fuel, starch-based SAF shows lower CI (75.0 vs 89.0 gCO 2 e/MJ) and fossil energy demand (0.96 vs 1.11 MJ/MJ), improving overall environmental performance. However, pea starch-derived fuels have higher life cycle water consumption than their fossil counterparts. Overall, pea starch shows potential as an additional feedstock for fuel production derived from a low-value co-product, particularly when process energy demand is minimized, although increased water consumption remains an important tradeoff.