Assessment of cross-media effects deriving from the application of lower emission standards for acid pollutants in waste-to-energy plants

The recent release of the new European Commission reference document on the Best Available Techniques (BAT) for waste incineration has set ambitious targets for the control of the emission of pollutants. However, an improved performance of the existing flue gas treatment systems in waste-to-energy (WtE) facilities is usually associated to an increase of cross-media effects, i.e., additional indirect environmental impacts related to the increased consumption of reactants and to the increased generation of process residues/wastewater in flue gas treatment. The present study introduces an innovative approach to assess cross-media effects deriving from more stringent acid gas emission standards in the WtE sector. By coupling simplified process modelling and life cycle analysis, the proposed methodology links the higher removal efficiency required for flue gas treatment to the impacts related to the reactants supply and waste disposal chain. An application to the Italian WtE sector exemplifies the potential of the method. The results evidence that, in case of HCl emission setpoints lower than 1 mg/Nm3, the reduction of acidifying emissions at the WtE stacks can be offset by the increase of global warming and smog formation impacts in the supply chain of flue gas cleaning reactants. In case of setpoints lower than 0.5 mg/Nm3, even within the acidification category the increase of indirect impacts more than compensates the decrease of WtE emissions. The net environmental benefit is strongly affected by the type of acid gas removal technology adopted, with dry systems typically associated with a larger increase of cross-media burdens when required to perform at higher removal efficiencies.