Theoretical analysis of energy recovery from food waste based on an integrated gasification and Stirling engine system

The high cost of food waste treatment by the traditional method and the hygiene problems caused by the accumulation make the reduction and energy regeneration of food waste locally necessary. In this paper, a combined gasification and CHP unit using Stirling engine system is modelled and evaluated. The process is aimed to treat the food waste from the canteen in the campus of Shanghai Jiao Tong University. After pre-treatment, the water content of food waste from the canteens at SJTU is less than 17%. By establishing a steady-state chemical reaction equilibrium model, the characteristics and yield of syngas from food waste through gasification process are analysed. When the equivalence ratio of gasification is 0.294, the results show that CO accounts for 18.4% and H2 accounts for 22.6% in syngas, and the higher heating value is 5.61 MJ/m3. The syngas is fed to a Stirling engine for power generation. The Stirling engine has low requirements of feedstock and is suitable for distributed waste to energy systems. By providing with 1175kg/d of food waste during peak days, the maximum energy output of the system is 131.7kW, and the overall efficiency of the system is ηall = 44.5%, with 21.6kW electricity and 110.1kW heat in hot water.