Integrating food waste sorting system with anaerobic digestion and gasification for hydrogen and methane co-production

Anaerobic digestion (AD) is a potential biotechnology to treat food waste for both energy and resource recovery. However, a high level of contamination in food waste limits their direct use as feedstocks. Therefore, a food waste sorting system followed by anaerobic digestion and gasification is proposed in this study to evaluate the potential of food waste for hydrogen and methane co-production through the thermal-equilibrium model and experimental study. To achieve the H-2-rich syngas and methane-rich biogas, the waste sorting system was used to separate the raw waste into pure food waste fraction for AD and discarded waste fraction for gasification. The thermal-equilibrium model is used to predict the content of H-2 at different moisture content and air equivalence ratio (ER). The results show that gasification generated the highest hydrogen content at 28.9% with a high moisture content of 55 wt% when the value of ER is 0.35. The highest calorific value of syngas is 5.59 MJ/m(3) at the conditions of 60 wt% of moisture content and 0.35 of ER. For the mesophilic AD system, the highest specific methane yield of FW is 557 mL/g VS. Thermophilic AD increased methane yield to 680 mL/g VS while AD of vegetable waste had a negligible production of methane gas. The overall energy performance of the integrated AD and gasification system was assessed in terms of the output of electricity and heat.