Mixing Approach to Waste Composition and its Lower Heating Value Impact on Waste-to-Energy Plant

Abstract

Recent research on waste management has primarily focused on the circular economy. This concept leads to increased sustainability by putting emphasis mainly on the reduction of waste production, recycling, and restriction of landfilling. It has already been incorporated in many national directives and legislations, while its effective implementation can be aided by mathematical programming. For the optimal operation of Waste-to-Energy plants, it is necessary to take into consideration the varying compositions and lower heating values (LHV) of the utilized wastes (or other commodities suitable for energy recovery). Because the LHV significantly influences the plant operating mode, waste heterogeneity can result in serious operating problems if bad strategic decisions had been made. The approach discussed represents a mixing task which considers the heterogeneity of wastes originating from different sources, the corresponding LHVs, and their impact on the final energy recovery. The implementation includes plant locations and network flows, operating costs (together with the return on investment), waste transport, and corrections of LHVs because all these factors are closely linked to the resulting profits from energy sales. The constraints consist of the necessary balances, such as capacities or heating limits. The developed optimization model is verified using a small waste transport network. The result of the model is a proposal for the redistribution of the mixed municipal waste, bulky waste and other combustible waste into specific technology sinks (Waste-to-Energy plant, landfill, cement plant). This article focuses on energy recovery from waste, which is also a crucial part of the transition to the circular economy. Future research is also outlined concerning the extension of the model’s environmental component and the large size of typical, real world optimization tasks of the respective type.