Assessment and optimization of a decentralized food-waste-to-energy system with anaerobic digestion and CHP for energy utilization

[Display omitted] •A decentralized system was set up to transfer food waste to electricity and heat.•30 kg food waste produced a methane yield of 0.55 L CH4/g VS in a current system.•A scale-up system was simulated to output 74.80kWh electricity at 500 kg feed per day.•Electrical and thermal energy outputs of optimized system increased by 135% and 87%. Biogas derived from the decentralized anaerobic digestion (AD) of food waste may be used to generate electrical and thermal energy for nearby residents through combined heat and power generation technology. A mobile food-waste-to-energy system in conjunction with an anaerobic digester and biogas engine was developed for food waste (FW) treatment and energy output. The scale-up was simulated to explore the methane yield and energy flow at different ambient temperatures of 0 °C, 10 °C, 20 °C, 30 °C and different feedstock of 200 kg, 500 kg FW. Accordingly, the results demonstrated that the installed system with a 1 m3 digester had a methane yield of 0.55L CH4 /g VS when the feedstock load was 30 kg FW/d and the Organic Load Rate (OLR) was 5.4 g VS /L, while the thermal and electrical efficiencies of this system were 31% and 16%, respectively. The corresponding exhaust gas of the thermal energy from the biogas combustion was recovered by a heat exchanger in order to keep the digester at mesophilic conditions. The simulations carried out on the scale-up systems under loads of 200 kg FW/d and 500 kg FW/d achieved a thermal energy balance at different ambient temperatures of 0 °C, 10 °C, 20 °C and 30 °C. Improvements were proposed in the optimized system by optimizing pre-treatment facilities as well as the AD reactor, biogas engine and heat exchanger. The net thermal and electrical energy output of the optimized system at 500 kg FW/d were 175.93kWh and 163.90kWh, respectively. The energy generated by the FW-to-energy system illustrated by the Sankey diagrams depicts that was enough for operation without the need of extra heat and a power supply, moreover, the surplus energy may be utilized for its neighboring communities. In addition, the optimized system under the same OLR were increased by 87% and 135%, regards the thermal and electrical energy outputs, respectively in comparison with the current system.