Environmental Impacts of Electricity from Incineration and Gasification: How the LCA Approach Can Affect the Results

Waste-to-energy (WtE) technologies can offer sustainable solutions for waste, which can no more be reused or recycled, such as the part of municipal solid waste (MSW) that is not suitable for recycling processes. This study focused on the environmental consequences of the production of electricity from incineration and gasification of MSW. To this aim, the standardised life cycle assessment (LCA) methodology was used. A life cycle inventory, mainly composed by primary data, is provided. Starting from these data, different highly shared LCA approaches were used to calculate the potential impacts of 1 kWh provided by the two analysed WtE technologies. The different approaches concern the method of accounting for the by-products (through an economic allocation and a system expansion) and the inclusion/exclusion of environmental benefits due to the avoided landfill for the MSW. For each approach, impact-assessment results were calculated with the ReCiPe midpoint (H) method. A comparison was carried out (i) between the results obtained for the same WtE technology but calculated with different approaches and (ii) between the impact results of electricity generated by the two WtE technologies calculated with the same approach. From the study, it emerged that, according to the accounting rules, the impact results can significantly change and, for some impact categories, even lead to opposite conclusions. In the absence of category rules that harmonise the environmental assessments of WtE processes, it is therefore recommended that the development/use/reproduction/comparison of studies focused on the valorisation of waste should be carried out with caution.