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Energy recovery for residual waste – A carbon based modelling approach - WR1910

Energy from waste is generally considered superior to landfill both as a better use of resources and in terms of environmental impact. Provided sufficient energy is recovered it is placed above landfill in the waste hierarchy. While there are a wide range of factors that ultimately determine if energy from waste is the best solution for a given situation its potential carbon benefits are a key consideration. The drive to ensure overall environmental benefits has led the EU to adopt the R1 formula for municipal waste incinerators to ensure minimum efficiency requirements are met. However, the picture is not static and little work has been done to understand the impact on these benefits of changing waste composition (driven by for example increased recycling of certain waste streams) or the changing energy mix (driven by decarbonisation). These and other changes could have a critical impact on the carbon case for EfW. By understanding that impact we can identify the measures necessary to maintain the carbon benefits of EfW over landfill and the rationale for its place as recovery in the hierarchy.

This analysis set out to identify the critical factors that affect the carbon case for energy from waste (EfW) in comparison to landfill and the sensitivity of that case to those factors. In particular the aim was to examine the influences that the biogenic carbon content of the waste and the thermal efficiency of the EfW process have on the relative benefits of EfW and landfill.

The model calculates and compares the carbon impact (CO2 or CO2equivalents) of a tonne of mixed residual waste going to either EfW or landfill. The model determines the theoretical plant efficiency at which there would be a balance point where the carbon impact of the two treatment routes is the same and examines how this balance point varies in relation to a range of factors including composition, energy offset and landfill gas capture.

The model is applied to potential future scenarios and across the lifetime of a potential energy from waste facility. It is used to examine the implications of carbon sequestration and alternative energy outputs.

The model was developed ‘in house’ by Defra using existing resources and subject to outside assessment to ensure robustness at key stages. The initial model was sense checked by Frith Resource Management Limited after completion of objective 1 funded through the Defra SCPW panel. The final model and report were peer reviewed by ERM in line with objective 5 (costs outlined below) in both cases issues raised were addressed.

1. To develop a model that describes the carbon impact of EfW and landfill for the same theoretical tonne of mixed waste and allows variation of key parameters including composition, energy offset factors, landfill gas capture.
2. To identify the theoretical plant efficiency at which the carbon impacts of the two routes balance, examine the sensitivity of this to a range of assumptions and identify the most important parameters
3. To assess the impact of a number of future scenarios varying key parameters on the carbon case for EfW
4. To identify potential measures indicated by the modelling to ensure the long term carbon benefits over landfill
5. To peer review the model and conclusions to ensure robustness
Project Documents
• FRP - Final Report : WR1910 Energy recovery for residual waste - A carbon based modelling apporach   (1102k)
Time-Scale and Cost
From: 2013

To: 2013

Cost: £11,050
Contractor / Funded Organisations
Environmental Resources Management (ERM)
Environmental Impact