Review of life-cycle environmental consequences of waste-to-energy solutions on the municipal solid waste management system

•Review of life-cycle assessment studies of municipal solid waste management systems.•Identification of waste-to-energy solutions and their environmental consequences.•Generally large consequences when implementing waste-to-energy solutions.•Suitability of waste-to-energy solutions usually affected by environmental trade-offs.•Departing from the waste hierarchy can be beneficial in specific contexts. The interest in implementing waste-to-energy (WtE) solutions for municipal solid waste (MSW) is increasing on a global scale motivated by the environmental concerns that arise from an inadequate disposal. The evaluation of the environmental impacts associated with WtE technologies has been widely addressed through the life-cycle assessment (LCA) methodology. However, a robust analysis of the environmental consequences of implementing WtE solutions requires the consideration of the entire MSW management system. In this review, we delve into published LCA studies on MSW management systems with the aim of identifying WtE solutions and their impact on the system's environmental performance. We found a consensus amongst the case studies reviewed on the favourable environmental consequences of both the diversion of organic waste from composting to anaerobic digestion and the implementation of a landfill gas collection system to produce electricity. There was also a consensus that the diversion of MSW from landfilling to incineration would generally reduce the global warming impact, but with uncertain human health consequences. Discrepancies were observed with respect to the environmental consequences of both the diversion of organic waste from incineration to anaerobic digestion and the diversion of waste from incineration to mechanical-biological treatment plants. Overall, this review can help decision-makers pre-identify environmentally sound WtE solutions. However, a subsequent LCA specific to the new context is imperative in order to identify the environmentally preferred option.