Contribution to a low-carbon society from improving exergy of waste-to-energy system by upgrading utilization of waste

Efficient energy recovery from burnable solid waste is considered an important component in a low-carbon society. Herein, we discuss the optimization of energy recovery from waste and how to reduce the environmental load of waste. First, we introduce the concept of upgrading waste-to-energy (WtE) processes to improve the exergy efficiency of society as a whole and provide guidance for selecting and combining the most appropriate technology for transforming waste-to-energy. We then propose a methodology called resource life-cycle assessment (LCA) that can be used to properly evaluate the effect of upgrading WtE processes and to optimize waste utilization not only within a given factory or municipality but also within society as a whole. Finally, we present two case studies with which we examine the direct and indirect upgrading of WtE processes and use resource LCA to quantitatively analyze the CO₂ reduction achieved by upgrading WtE processes compared with that achieved by conventional WtE processes. The analysis of these case studies shows that upgrading WtE processes would result in approximately 50%–100% greater reduction in fossil fuel input compared with conventional waste power generation, which means that we expect a 50% to 100% greater reduction in CO₂ emissions and the concomitant savings in fuel cost. The concept of upgrading WtE processes and resource LCA is useful for selecting a cost-effective option to improve the exergy efficiency both in developed countries and in developing countries, many of which need to contribute to their Nationally Determined Contribution under the Paris Agreement.