Why landfill methane deserves attention

Walk across a closed landfill on a still, damp morning and you may notice nothing at all. Yet beneath the grass cap, bacteria are steadily breaking down decades of waste and releasing methane — a gas with roughly 80 times the warming effect of carbon dioxide over a 20-year window. Because that window matters so much for near-term climate targets, plugging methane leaks is one of the fastest ways the UK can slow warming.

Landfill gas is roughly half methane and half carbon dioxide, with traces of volatile organic compounds and hydrogen sulphide. Modern sites capture much of it through vertical wells and pipework, then burn it in flares or gas engines to generate electricity. But capture is never perfect. Leaks cluster around wellheads, pipe joints, cracked cap material, leachate wells and old tipping fronts. Finding them used to mean walking the perimeter with a handheld detector and hoping the wind cooperated. That is changing.

Drones and aerial surveys

Small unmanned aircraft fitted with lightweight methane sensors are now being trialled across UK landfill sites. The most common approach uses tunable diode laser absorption spectroscopy, which shines a laser through the air and measures how much light methane absorbs. Fly a grid pattern at 20 to 40 metres and you get a concentration map rather than a single reading.

• Optical gas imaging cameras show plumes in real time, making them ideal for confirming a suspected leak once a drone has flagged it.
• Drone surveys cover awkward terrain — steep flanks, capped cells, working tipping faces — in under an hour.
• Repeat flights build a picture over time, so you can see whether a repaired wellhead is actually holding.

The practical gains are real: fewer hours spent on uneven ground, better evidence for regulators, and a clearer link between a leak and the specific piece of infrastructure causing it.

Satellite data sharpens the picture

Satellites add a different scale of insight. Instruments such as the European Sentinel-5P mission and a new generation of commercial methane-sensing satellites can detect large plumes from space, sometimes attributing them to individual sites. The resolution is coarse compared with a drone, so satellites rarely catch a single leaking wellhead — but they are excellent at spotting the big, persistent sources that dominate total emissions.

Researchers increasingly combine satellite observations with wind data and atmospheric models to estimate emission rates in tonnes per hour. For site operators, that means an independent check on their own calculations. If a satellite flags your site and your internal figures say otherwise, it is worth investigating rather than dismissing. Regulators are paying attention to the same data.

Improving gas collection systems

Detection is only half the job. Capture infrastructure is where the emissions actually fall.

• Wellhead balancing — adjusting the suction on each well so the whole field draws evenly, rather than a few wells doing all the work.
• Suction pressure tuning — too much vacuum pulls in air, which cools the flare and can create a flammable mix; too little lets gas escape through the cap.
• Cap condition — clay, low-permeability soil and synthetic membranes all reduce fugitive emissions, especially where settlement has cracked the surface.
• Methane oxidation layers — a shallow biofilter of compost or engineered soil lets methane-eating bacteria mop up low-concentration gas near the surface.
• Flare and engine reliability — an offline flare is an open vent, so uptime monitoring and quick maintenance matter enormously.

On older, smaller sites without gas engines, a well-designed flare with proper monitoring is still a substantial improvement on passive venting.

Practical steps for operators and councils

You do not need a large budget to make progress. Start with a weekly walkover using a handheld detector, logging readings alongside wind direction and wellhead data. Check every wellhead for methane, oxygen and flow balance — a jump in oxygen usually means a cracked seal or a broken pipe underground. Survey after heavy rain and after sharp drops in atmospheric pressure, when gas tends to push out of the waste more forcefully.

Keep records that a regulator can follow: dates, locations, concentrations, repairs made and the readings afterwards. Councils managing closed sites can pool resources for shared drone surveys, and many find that a single well-targeted repair campaign pays for itself in improved gas yield for the engines.

What comes next

The direction of travel is clear. Scotland has moved to ban biodegradable municipal waste from landfill, England is tightening collection rules to keep food waste out of the residual stream, and the UK Emissions Trading Scheme is set to extend to the waste sector, which will put a price on every tonne of methane a site fails to capture. Add falling costs for sensors and satellite data, and the case for routine leak detection becomes straightforward. The sites that measure carefully, repair quickly and document clearly will be the ones best placed when the rules tighten.