Research and analysis

Landfill methane: measurement and metrics: supplementary report: summary

Published 7 August 2026

Applies to England

1. Waste and Resources research report summary

This project continued the Environment Agency’s work on measuring methane emissions from landfills and investigating how those measurements could be used in regulating landfills. We undertook additional whole site methane emission surveys, using two measurement methods, to evaluate the effectiveness of landfill gas management systems.

1.1 Background 

Methane is an important greenhouse gas which is much more potent than carbon dioxide. Methane is one of the main gases that are produced in landfills as organic waste decomposes, and landfills are a major source of anthropogenic methane emissions. It is therefore important that releases of methane from landfill sites are effectively managed to reduce climate impacts. Measuring methane emissions from landfills is difficult because the emissions can come from different sources across a wide area, but if we do know the methane emission rate, this can help us in determining how effectively a landfill operator is collecting the landfill gas.

This project continued the work reported in Landfill methane: measurement and metrics (referred to here as, the “main report”) by providing additional whole site methane measurements that gave results across a whole calendar year.

1.2 Approach 

The project used the same two survey methods to measure the rate of methane emissions as described in the main report. These were the Tracer Dispersion Method (TDM) and an Unmanned Aerial Vehicle (UAV) mass balance method. TDM surveys were carried out at three of the four English landfill sites considered in the main report and Unmanned Aerial Vehicle mass balance surveys were undertaken at two of those landfills.  The surveys were carried out between August 2025 and January 2026 with the UAV mass balance surveys being carried out at around the same time as the TDM surveys to further compare the two approaches.

The most promising metric for landfill gas management performance identified in the main report was the Methane Collection Efficiency. The measurements from the additional surveys were used to calculate the Methane Collection Efficiency based on the measured emission rate and the rate at which the operator was collecting the landfill gas.

1.3 Results

The additional surveys supported the finding, set out in the main report, that both methods can effectively measure methane emissions from landfill sites. One of the issues identified was that the UAV mass balance method gave a lower methane emission rate than the TDM. This is believed to be, in part, because the UAV cannot fly close to the ground and so some of the emitted methane may be missed. An approach was developed to estimate the amount of methane missed, and this value was added to the error bars for the methane emission rate measurements. This new approach for estimating the methane close to the ground, added to the mass balance uncertainty, meant that the UAV mass balance method and the TDM results were closer to agreement, considering the uncertainty.

The additional surveys provided some good examples of the factors that can influence the results of the methane emission measurements. TDM surveys conducted over a period where there was a large change in atmospheric pressure gave substantially different results for the methane emission rate. A statistical analysis of the factors influencing emissions, using data from the main report and the additional surveys, found that changes in atmospheric pressure were correlated with emission rates, as was the change in temperature over 5 days, but the analysis showed differences in these relationships between sites. This suggests that the influence of different factors may be site specific.

When the wind was blowing in a particular direction, the results of a TDM survey were found to include a contribution from an adjacent closed landfill. This was demonstrated by the clear presence of other methane plumes alongside the targeted landfill plume when a survey was undertaken with a different wind direction. This illustrates the need to carefully identify other potential sources of methane emissions and to plan surveys when the wind direction will allow the landfill plume to be separately identified.

Another issue illustrated by the results was lower measured methane emission rates when the UAV flight path was restricted and was unable to fly through the whole methane plume. This highlights the need to plan UAV mass balance surveys for when the wind direction is suitable for capturing the full extent of the methane plume.

The calculated Methane Collection Efficiencies for the three sites were found to be consistent with those given in the main report with the landfills achieving between 70% to 94% methane collection in normal operating conditions. The Methane Collection Efficiency was again found to be able to reflect operational changes, and this was illustrated at a site that was undergoing closure where a higher Methane Collection Efficiency was found after the reconnection of the landfill gas system following capping work at the site.

1.4 Conclusion

The additional survey results supported the conclusion in the main report that the Methane Collection Efficiency could be a suitable metric for measuring the performance of landfill gas collection systems and that the results can reflect changes in gas management or other operational practices. The results show that a high rate of methane collection can be achieved using existing best practice for landfill gas management.

The results provided further evidence for the need for careful planning of surveys to ensure that the requirements of the methods can be met to make them suitable for regulatory use. For the TDM, this means isolating the landfill plume from other methane sources and, for the UAV mass balance approach, capturing the full extent of the landfill plume.

As well as undertaking methane measurement surveys under normal operating conditions to ensure that results are representative of typical site operations, the surveys should be done when the meteorological conditions are steady and not subject to rapid change. This would minimise the impact of the factors that may influence methane emission rates and would allow the results to provide a more meaningful demonstration of the effectiveness of the installed landfill gas collection system.

1.5 Publication details

This summary relates to information from project RDE 436/2, reported in detail in the following output:

• Report: RDE 436/2
• Title: Landfill methane: measurement and metrics a supplementary report
• Technical Leads: Dave Browell, Environment and Business Directorate, Landfill, Deposit for Recovery and Climate Change Team and Mark Bourn, Chief Scientist’s Group
• Research Contractor: Ricardo

This project was commissioned by the Environment Agency’s Environment and Business Directorate.

Enquiries: research@environment-agency.gov.uk.

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