Increasing Profits in Food Waste BiorefineryA Techno-Economic Analysis

The present manuscript highlights the economic profit increase when combining organic waste anaerobic digestion with other mixed culture anaerobic fermentation technologies, e.g., lactic acid fermentation and dark fermentation. Here we consider the conversion of 50 tonnes/day of food waste into methane, power generation (from CHP of biomethane), lactic acid, polylactic acid, hydrogen, acetic acid and butyric acid. The economic assessment shows that the basic alternative, i.e., anaerobic digestion with methane selling to the grid, generates 19 USD/t_VS (3 USD/t_foodwaste) of profit. The highest profit is obtained by dark fermentation with separation and purification of acetic and butyric acids, i.e., 296 USD/t_VS (47 USD/t_foodwaste). The only alternative that presented losses is the power generation alternative, needing tipping fees and/or subsidy of 176 USD/t_VS (29 USD/t_foodwaste). The rest of the alternatives generate profit. From the return on investment (ROI) and payback time, the best scenario is the production of polylactic acid, with 98% ROI, and 7.8 years payback time. Production of butyric acid ROI and payback time was 74% and 9.1 years.