Small changes in municipal waste composition could push energy from waste above landfill in generating climate change emissions, a Scottish Government funded report has found.
The study also reasons that energy from waste can no longer be considered a “low carbon technology” in the UK, largely because electricity generation is becoming more decarbonised.
The technical study, for Zero Waste Scotland, reports that burning residual municipal waste in Energy from Waste plants in Scotland in 2018 had an average carbon intensity of 509 gCO2/kWh.
“This is nearly twice as high as the carbon intensity of the UK marginal electricity grid average, which was 270 gCO2/kWh in 2018,” says the study.
The report, “The climate change impact of burning municipal waste in Scotland” was complied by Kimberley Pratt and Michael Lengahan and was peer reviewed. It was funded by the Scottish Government and the European Union and published on 3 October 2020.
(above) Average carbon intensity of EfW plant types in Scotland in 2018 (source: Zero Waste Scotland)
Zero Waste Scotland said that the study measures climate change impacts in two ways: carbon intensity and greenhouse gas emissions.
“Carbon intensity is a standard approach for comparing the climate change impacts of different energy generation technologies. In this study, the carbon intensity of EfW plants are compared to the UK national grid average. The results show that the carbon intensity of EfW plants is twice as high as the grid average. EfW carbon intensities would remain above the grid average even the plants were converted to Combined Heat and Power systems, demonstrating that EfW can no longer be considered a low carbon technology in the UK.”
Of potentially more significance is the comparison that the report makes between landfill and energy from waste as the UK continues to drive towards the construction of energy from waste plants in an ongoing move away from landfill.
Greenhouse gases from landfill have been the driver for construction of EfW plants. On greenhouse gases, Zero Waste Scotland explains that the study compared the carbon impacts of sending one tonne of residual municipal waste to either EfW or landfill. “Average EfW impacts were 15% lower than landfill in 2018. However, changes in waste composition mean that EfW impacts are expected to rise. Small changes in composition could push EfW impacts above landfill, leading to unnecessary climate change emissions.”
The report has been reviewed by members of the Scottish Waste Data Strategy Board, and includes discussion about where improvements in publicly available data could support accurate and ongoing monitoring of the carbon impacts of burning waste in Scotland.
In terms of composition, the study says that if the proportion of plastic in residual municipal waste increases from 15% to 17%, greenhouse emissions per tonne for incinerators rises to the same level as landfill. “Converting to CHP systems reduces the carbon intensity of EfW plants significantly but not below the UK average for marginal grid electricity.”
Conclusions in the study are that it has implications for how long-term infrastructure and policy decisions are made. “Whilst EfW plants have been successful, to date, in reducing greenhouse gas emissions from residual municipal waste, there is a risk that these savings will be lost if current trends and policies continue. This is due to the changing nature of waste composition and because of the successful decarbonisation of the UK and Scottish energy grids. Decarbonisation of the grid has been so successful that EfW technologies can no longer be considered low carbon solutions.”
The report emphasises: “Decisions on future management must be based on the most current and accurate data possible to ensure climate change impacts are minimised. Waste policy should be adapted to take advantage of significant opportunities to reduce the climate change impacts of waste further.”
The six plants studied in the report are: Dunbar energy recovery facility, East Lothians (Viridor); MVV’s Baldovie facility, Dundee; FCC’s Millerhill energy recovery centre, Edinburgh; Viridor’s Glasgow recycling and renewable energy centre, Glasgow; Levenseat’s thermal waste treatment plant, West Lothian; and the Lerwick energy recovery plant, Shetland Islands (Shetland Council).