Abstract

Municipal solid waste (MSW) incinerators require effective flue gas treatment (FGT) to meet stringent environmental regulations. However, this in turn generates additional environmental costs through the impacts of materials and energy used in the treatment – these impacts are currently scarcely known. Therefore, this study uses life cycle assessment to estimate the impacts of different FGT systems typically found in modern MSW incinerators. A total of 12 scenarios are modelled to consider different combinations of the following eight technologies: electrostatic precipitators and fabric filters for removal of particulate matter; dry, semi-dry and wet scrubbers for acid gases; selective non-catalytic and catalytic reduction of nitrogen oxides (NOx); and activated carbon for removal of dioxins and heavy metals. The data are sourced from 90 full-scale incinerators operating in France. The results reveal that a dry system using sodium bicarbonate and selective non-catalytic reduction (SNCR) is the best option for seven out of 18 impacts, including climate change (37.1 kg CO2 eq./t MSW). By contrast, a dry system with calcium hydroxide and selective catalytic reduction (SCR) has the highest impacts in six categories, including climate change (102 kg CO2 eq./t MSW). The wet systems have higher impacts than the dry alternatives, with the semi-dry options being in between. Compared to SNCR, the use of SCR decreases the NOx-related impacts (fine particulate matter formation, terrestrial acidification and photochemical ozone formation) but increases other impacts. For example, the SCR systems have 49–284% greater climate change and 43–150% higher depletion of fossil resources than their SNCR counterparts. Overall, all FGT systems reduce significantly fine particulate matter formation (by 81–88%), photochemical ozone formation (76–90%) and terrestrial acidification (83–90%). However, they also cause 14 other impacts which would not be generated if the flue gas was left untreated, thus creating additional environmental costs. These include climate change, resource depletion and human and ecotoxicities. Therefore, these trade-offs should be considered carefully to minimise the unintended environmental consequences of flue gas treatment from incineration of MSW.

Highlights

  • In recent times, the role of municipal solid waste (MSW) incinerators has shifted from diverting waste streams from landfills to be used for energy provision [1,2]

  • A typical dry acid gases removal based on sodium bicarbonate (NaHCO3) was considered and the results showed that the production of the reagent and treatment of solid residues were the key environmental hotspots

  • This section is structured as follows: first, the environmental impacts of selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) scenarios are presented in Sections 4.1 and 4.2, respectively

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Summary

Introduction

The role of municipal solid waste (MSW) incinerators has shifted from diverting waste streams from landfills to be used for energy provision [1,2]. In the EU, 28% of the MSW is incinerated [3]. In France, for instance, this figure is even higher (32%), with 114 incineration plants treating 14.4 Mt/yr of MSW [4]. MSW incineration still faces public opposition in some countries and regions. The major issue around this debate is mainly associated with the generation of toxic pollutants [5]. To minimise the environmental and human health impacts associated with MSW incineration, the EU Directive 2000/76/EC [6] set stringent operational conditions and technical requirements for MSW incineration plants, and was subsequently integrated into the Directive 2010/75/EU [7] for different types of industrial plants. Meeting the requirements of the Directive requires a range of flue gas treatment (FGT) technologies to remove target pollutants, including [8,9]:

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