A strategy for food waste-to-biofuels: Co-production of gasoline alternatives from volatile fatty acids

Abstract

Volatile fatty acids (VFA), byproducts of anaerobic digestion of organic waste, have emerged as a platform molecule for the production of liquid fuels and chemicals. This study reports a co-production process that allows the conversion of VFAs into promising gasoline alternatives: acetic acid to ethanol (EtOH) via methyl acetate and butyric acid to butanol (BuOH) via methyl butyrate. The effect of process integration combining acetic acid to EtOH with butyric acid to BuOH on a large-scale is investigated to improve energy efficiency and economics of the co-production process. The process model simulation results show an overall (EtOH + BuOH)/VFA mass yield of 46.2% and a high energy efficiency of 37.3%, in which most (79.6%) of heat requirements for the co-production process are satisfied internally by the heat exchanger network design using the burning of VFAs residues. Techno-economic feasibility of the co-production process was US$ 5.29 per gallon of gasoline equivalent as a blend fuel of E10 (i.e., 10% EtOH and 90% gasoline).