Evaluation of the cross‐media effects of new emission limit values for waste‐to‐energy plants via a combination of process modelling and life cycle assessment

Conference Dates

June 5 – 10, 2022


The recent release of the new European reference document on the Best Available Techniques for waste incineration (2019 BREF WI) has set ambitious targets for the control of waste combustion pollutants, such as acid gases (HCl and SO2). Within 2024 existing waste-to-energy (WtE) plants will have to reduce their acid gas emissions at stack at least at the levels indicated by BREF WI. To comply with reduced emission limit values (ELVs), WtE plants will need to increase the performance of their flue gas treatment (FGT) systems, at the cost of increased cross-media effects, i.e., additional indirect environmental impacts related to the increased consumption of reactant and the increased generation of process residues/wastewater. The present study aims at proposing a methodology to estimate the cross-media effects associated to more stringent ELVs in the WtE sector, in order to assess the full environmental balance of new emission regulations, taking into account not only the emissions at stack but also the indirect impacts arising along the life cycle of FGT. The methodology, outlined in Fig. 1a, allows to derive quantitative estimates on cross-media effects starting from publicly available emission data through a combination of process modelling and life cycle assessment (LCA). The higher pollutant conversion required by lower ELVs is translated into associated increased mass flows of reactants and process waste by means of a portfolio of models defined for all the main FGT technologies available. These flows are the inputs for a life cycle model that describes all the upstream and downstream stages involved in the process (production of reactants, disposal of process waste, transportation phases). Eventually, the impacts of the process are quantified by means of a set of LCA indicators. The study shows an application of the methodology to Italy (see Fig. 1b). The results identify the full environmental and economic consequences of the imposition of stricter ELVs for acid gases to all the 36 existing WtE plants in the country. As an example, the assessment on the acidification indicator (Fig. 1c) evidences how the reduction of ELVs at stack significantly diminishes the direct acidification impact caused by HCl and SO2 emissions at the WtE plants, but 30% of this benefit is compensated by an increase of the indirect impacts in the other life cycle stages. A breakdown of the results by plant and by FGT technology allows pinpointing the environmental hotspots of the system and identifying which are the key elements determining the tradeoffs between lower emissions at stack and higher transmedial impacts. Therefore, the study provides a more complete picture on the implications of a change in emission policy and can support the identification of optimal ELVs by local environmental agencies. Figure

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