Research and analysis

Drone flyover surveys for identifying methane emission sources at landfills: summary

Published 7 August 2026

Applies to England

1. Waste and Resources research report summary

This project investigated the potential use of unmanned aerial vehicles (UAVs, also known as drones) for identifying sources of methane emissions at landfills. The methane concentrations from a conventional ground-based walkover survey were compared to measurements from a drone using an open path laser remote sensing technique.

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.

Modern landfills in England capture landfill gas and either use the methane as a fuel or burn it in a flare. However, a proportion of the landfill gas escapes into the atmosphere through a variety of pathways, such as breaches of the surface cap or leaks from the gas recovery infrastructure. The current approach to identifying the location of any significant fugitive emissions of methane is to conduct periodic walkover surveys of the landfill surface using handheld methane detection instruments. Conducting a walkover survey is a relatively slow and labour-intensive exercise, that can expose operators to the potential hazards associated with monitoring across the surface of the landfill. Therefore, there is an interest in understanding whether new technologies could enhance or replace this current approach.

1.2 Approach

The aim of this project was to understand if a UAV based method using downward pointing Open-Path Tuneable Diode Absorption Spectroscopy (OP-TDLAS) for detecting methane emissions from landfill surfaces could be a satisfactory replacement for a walkover survey undertaken following the Environment Agency guidance on monitoring landfill gas surface emissions.

A literature review was undertaken to determine the state of knowledge in this area and to inform the design of the fieldwork. To evaluate the performance of the UAV based method using the walkover method as the reference baseline, a sampling plan was developed such that nominally identical transect lines were sampled by both the walkover team and the UAV with just a small time interval. This approach allowed the project team to distinguish between areas emitting landfill gas and those surfaces producing potential false positives (a reading showing methane when there is no emission) or instrumental errors from the OP-TDLAS. The response of the UAV mounted OP-TDLAS is highly dependent on intrinsic instrument noise, weather conditions and surface albedo (reflectively of a surface) and these all have an impact on the level of background noise, which can create false positives.

Three sites were surveyed, two active landfills and one closed (labelled as A1, A2 and C1). A landfill walkover survey and UAV survey were completed in parallel to compare the two techniques at each site. The field work was conducted between mid-November and early December 2025. Whilst the three surveys did not cover the entire surface of each landfill, areas were selected to cover as much gas recovery infrastructure as possible. The walkover and UAV surveys were planned around approximately 100 metre parallel transects with approximately 20 metre spacing with the walkover survey matching the path of the UAV as closely as possible given the ground conditions and topography of the sites. For the walkover survey, an operator held the sampling probe, less than 5 cm from the ground surface, taking a spot measurement of methane concentration every 5 metres. Gas recovery infrastructure was also surveyed in the same area. The UAV was flown between 10 and 30 metres above ground level with the OP-TDLAS taking around ten measurements every second. Local weather conditions, including wind speed and direction, were recorded.

1.3 Results

For the closed site C1, the walkover survey method found no potential fugitive emissions across the entire survey. A false positive was found for the UAV survey (the walkover survey confirmed that this was a false positive), which was likely due to ground vegetation causing an increase in background noise.

For site A2, there were also some false positives from the UAV survey which were attributed to changes in surface albedo and vegetation density. There was one transect where potential fugitive emissions were identified by both methods, although the location of these did not completely agree. The walkover survey slightly deviated from the path of the UAV during this transect so it is likely the UAV did not fly directly over the emission source.

The UAV survey at site A1 was able to detect several points of potential emissions. However, it did not identify an emission from a ground fissure found by the walkover survey. The following day, the UAV was able to detect more methane activity with peaks close to emissions sources located in the walkover survey. The UAV detected concentrations of note in one area that the walkover did not identify as an emission source. The ground surface was covered in debris and had significant craters, so it was difficult to get the probe close to the ground. It is possible that an emission source did exist but that the walkover survey was unable to adequately access the area to confirm this.

1.4 Conclusion

The walkover survey was able to precisely identify potential emissions sources to a greater extent than the UAV survey. However, the UAV survey was often able to identify those same areas of elevated concentration which could be highlighted for further investigation by a ground-based team. The UAV completed transects in half the time compared to the walkover team of two operators. Importantly, the UAV can fly at speeds of 15 metres per second between transects which would significantly reduce transit time between transects compared with a walkover survey, covering a larger area in a shorter time.

A UAV OP-TDLAS survey was found to be a potentially good tool for identifying areas of emission. The technique would allow for areas of concern to be identified which could then be further investigated with a portable gas detector. With TDLAS technology rapidly evolving, future sensors are expected to have improved sensitivity and detection capabilities which may reduce the number of false positives and remove the reliance on operator experience for identifying those false positives, helping to create a more reliable and quantitative method for detecting methane emissions from landfill.

Further tandem walkover and UAV OP-TDLAS surveys could be undertaken to assess the performance of the UAV at identifying emissions by flying to gas recovery infrastructure and performing compact sampling transects. Campaigns with the UAV as the primary method of localisation which inform a secondary targeted walkover survey of specific areas could be tested and compared with a standard walkover survey to assess the advantages of implementing this combined approach in real world scenarios. There may also be a role for controlled release experiments to test the approach on a wider range of emission rates than may be found on the studied landfills.

1.5 Publication details

This summary relates to information from project RDE 851, reported in detail in the following output:

• Report: RDE 851

• Title: Drone flyover surveys for identifying methane emission sources at landfills
• 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: NPL

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

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

© Environment Agency