Food waste biorefinery: Stability of an acidogenic fermentation system with carbon dioxide sequestration and electricity generation

The present study focused on the integration of the non-sterile conversion of food waste (FW) into hydrogen (H-2) through dark fermentation with the subsequent electricity generation in a proton-exchange membrane fuel cell (PEMFC), and the assessment of the global warming potential (GWP) of the process. The acidogenic conversion of FW performed in continuous operation for 16 days produced 45.6 +/- 0.1 L H-2 at an average H-2 productivity of 6.1 +/- 1.3 L L-1 d(-1). Butyric and acetic acid were simultaneously produced at average concentrations of 3.6 +/- 0.5 and 1.6 +/- 0.3 g L-1, respectively. The carbon dioxide (CO2) from biogas product was sequestered by reaction with sodium hydroxide and the resulting H-2-rich stream was fed to a PEMFC, producing 1.7 Wh L-1 H-2. The process scale-up was simulated based on the bench-scale conversion yields and was used to assess the GWP. Two of the developed scenarios, which considered the reuse of the fermentation sludge as nitrogen source in the acidogenic fermentation, diminished the GWP emissions by 63.8% and 64.3% when compared to the default condition. In the best-case scenario, an annual average of 0.18 t of CO2 per t of FW separately collected was generated. (C) 2020 Elsevier Ltd. All rights reserved.