Development and optimization of an innovative three-stage bioprocess for converting food wastes to hydrogen and methane

Abstract This paper sheds new light on biological hydrogen and methane technologies. An integrated process of dark fermentation, microbial electrolysis cell, and biomethanation producing both hydrogen and methane was investigated for the first time. For this purpose, operating condition optimization in terms of hydrogen and methane generated in this process from food waste was conducted. The optimization procedure correlates the substrate to inoculum ratio, applied voltage, and electrode distance to hydrogen and methane potentials using the full factorial statistical experimental design and the response surface methodology approach. Results show that the process was strongly affected by the three studied parameters. The most suitable substrate to inoculum ratio, applied voltage, and electrode distance resulting in the highest hydrogen gas yield (85.13 mL H2/gVSin) and methane gas yield (364.9 mL CH4/gVSin) were defined as 1.5, 0.5 V, and 3.5 cm. The overall integrated process reached a global energy yield of 13.91 kJ/gVSin. Yields achieved in this study attest that food waste constitute a good substrate for hydrogen and methane production, and the multiple stage combination shows advantageous process performance. Further research is necessary to evaluate its economic feasibility, and energetic and environmental benefit.