Energy from waste: carbon footprint of incineration and landfill biogas in the UK

The majority of waste in many countries is still landfilled. This represents waste of valuable resources and could lead to higher emissions of greenhouse gases (GHG) compared to energy recovered by incineration, even when the landfill gas is recovered. This paper aims to find out which option is more sustainable with respect to the carbon footprint (global warming potential) by comparing energy recovered from MSW incineration with that from biogas recovered from landfilled waste.

Life cycle assessment has been used as a tool, following the ISO 14040/44 and PAS 2050 methodologies. Data have been sourced from the operator of the incinerator, the Environment Agency for England and Wales, the CCaLC and Ecoinvent databases. CCaLC v2 and GaBi v4.3 have been used for the LCA modelling.

The carbon footprint of MSW incineration is −0.179 t CO₂ eq./t MSW while that from landfilling is 0.395 t CO₂ eq./t MSW, with both systems credited for energy recovery. The results are sensitive to the composition of waste, energy options chosen to credit the systems and the recovery rate of biogas. Increasing the amount of fossil carbon in the waste by increasing paper recycling between 40 and 80 % increases the carbon footprint of incineration by 9–20 %. If instead of the electricity from the UK grid, electricity from heavy fuel oil or coal is assumed to be displaced by incineration, its carbon footprint reduces to −0.51 and −0.35 t CO₂ eq./t MSW, respectively. Increasing the landfill gas recovery from 53 to 75 % and its utilisation for energy from 35 to 50 %, reduces the carbon footprint of landfilling by a half.

The results indicate that waste incineration offers significant savings of GHG compared to disposal by landfill. Based on the total amount of MSW of 225,000 t/year considered in this study, MSW incineration could save around 129 kt of CO₂ eq. per year compared to landfilling with biogas recovery, with both systems co-generating heat and electricity. At the UK level, diverting all MSW that is currently landfilled to incineration with energy recovery could save around 8.38 million tonnes of CO₂ eq. per year or 1.5 % of the total UK GHG emissions. These savings can be increased further by recycling of bottom ash and non-ferrous metals. Incineration remains a better option than landfilling under all the conditions considered in this study.