Assessing the negative carbon emissions potential from the Waste-to-Energy sector in Europe

Abstract

Addressing climate change and the sustainable management of municipal solid waste (MSW) are two important societal challenges, as recognized by the 2015 Paris Climate Agreement and by the EU Action Plan for a Circular Economy Package [1]. One possible solution to both of these challenges is to combine Waste-to-Energy (WtE) technologies with carbon capture and storage (CCS) to achieve a net environmental benefit. Under the scope of NEWEST-CCUS project , this work conducts a quantitative evaluation of the environmental performance and presents work to date on assessing the negative emissions potential of WtE with CCS across Europe.
Approximately 252 Mt of municipal waste was generated in the EU in 2019, of which 28% was treated in energy recovery facilities and 23.4% was disposed in landfill sites [2]. As landfilling is being phased out in Europe [3], the importance of recovering the energy content from the household and commercial waste remaining after prevention, recycling and composting is increasing. Waste-to-Energy (WtE) facilities using incineration are indeed gaining importance in Europe, with approximately 500 WtE plants in operation in 2019 treating approximately 100 Mt of municipal solid waste [4]. These plants can significantly reduce the volume and weight of MSW and prevent various pollutants from being emitted, while producing useful electricity and heat.
CCS is the main decarbonization option for the WtE sector in Europe. Further, combining WtE and CCS has the potential to create a carbon sink over the life cycle of waste by preventing emission of biogenic carbon, which has been ‘drawn down’ atmospheric CO2 via photosynthesis. The ratio of biogenic to fossil carbon content of MSW varies significantly but is generally between 50 and 70% [5], with a typical content of around 60% [4]. However, there is a need to develop a rigorous and robust methodology to account for the negative carbon emissions potential when capturing and permanently storing biogenic CO2 from waste incineration.
This article presents an attributional Life Cycle Assessment (LCA) to assess the environmental impact of combusting municipal waste in a conventional WtE facility with moving grate technology and equipped with an amine (solvent) based carbon capture plant. The capture plant operates with a capture level of 99.7% so that all CO2emissions arising from fuel combustion are avoided. This assessment considers real operation parameters obtained from rigorous process modelling of the integrated WtE and carbon capture systems to account for the avoided environmental impacts of producing combined heat and power (CHP) as well as the avoided impacts from metal recovery. In addition, this paper outlines a method and average waste composition for assessing the potential for negative emissions from WtE + CCS at the European scale.
Four WtE configurations were assessed: power-only WtE; WtE with integrated Combined Heat and Power (CHP); power-only WtE with CCS and WtE with CHP and CCS. The four cases were found to impart environmental benefits across the majority of the eighteen impact categories considered, reflecting results from [6]. In the context of greenhouse gas control, when CHP or CCS is configured with WtE, a benefit is also imparted in the Global Warming impact category. Within a 95% confidence interval the median values are: 151 kgCO2eq/tMSW (64 to 241); -97 kgCO2eq/tMSW (-227 to 33); -648 kgCO2eq/tMSW (-785 to -514) and -772 kgCO2eq/tMSW (-925 to -630) for the power-only WtE, CHP WtE, power-only WtE + CCS, CHP WtE + CCS cases respectively. In general, the contribution to climate change impact associated to the materials used in the physical infrastructure is relatively small, while the direct ‘stack’ GHG emissions dominate for the configurations without CCS. The avoided impacts due to electricity and heat generation are also significant, and always larger than the avoided impacts of IBA mineral and metal recovery.
An overview of the assessment of European potential for negative emissions from WtE and CCS is provided, with focus on developing an average European waste composition which could be used in process and LCA modelling to enable the European potential to be accurately assessed using a life cycle approach. Further, the effect of national power system emissions intensity on avoided (and thus negative) emissions shows that for countries with annual average emissions intensities above 460 kg even the power-only WtE plant could be climate neutral, although this is subject to realizing the avoided impacts, as well as the targeted trends of global decarbonization of electricity.

Keywords: Waste to Energy; Bio-energy with CCS; carbon negative emissions; circular economy, municipal solid waste.