Landfill gas: the actual risks, explained calmly

Landfill gas is the reason "the estate was built on a tip" stories run in local papers, and it deserves a straight explanation rather than either panic or a shrug. The short version: decomposing organic waste produces methane and carbon dioxide for two to four decades after tipping stops; the gas is manageable and routinely managed; and because most of England's 19,851 recorded historic landfills closed generations ago, the majority have largely finished producing it. The cases that matter are specific and identifiable.

Where the gas comes from

Bacteria digesting organic matter — food, paper, garden waste — in the oxygen-starved depths of a tip produce roughly half methane, half carbon dioxide. Three consequences follow. Inert waste (rubble, subsoil, concrete) produces essentially none, which is why the waste categories on each site record matter so much. Production peaks in the years right after tipping and decays exponentially — the standard engineering assumption is that meaningful generation lasts 20–40 years, longer for very large, deep, wet sites. And the gas only matters if it can travel: through made ground, service trenches or cracks, into an enclosed space where it can accumulate.

The two genuine hazards

• Asphyxiation/explosion in confined spaces. Methane is explosive between roughly 5% and 15% concentration in air. The serious historical incidents (Loscoe, Derbyshire, 1986 is the textbook case — a bungalow destroyed 70m from a closed tip) involved gas migrating into unprotected buildings. These incidents are why modern rules exist; they are also vanishingly rare.
• Chronic seepage into buildings. Less dramatic: elevated CO2 in cellars and crawl spaces. Detectable, ventable, fixable.

What landfill gas is not: a contamination of your soil, a contaminant of home-grown vegetables, or something that affects you at 400m across open ground. Migration distances beyond ~250m through ordinary ground are exceptional; most guidance treats 250m as the outer screening radius.

How it's managed

Three layers, in rough order of appearance since the 1970s:

1. On-site controls at the tip — venting wells, flares, capping. The EA record notes where gas control is recorded for a site (shown on each site page here).
2. Building protection — since the 1990s, homes built on or near gassing ground get membranes and vented sub-floors as a planning condition. If your estate was built on a former tip after ~1995, this documentation exists.
3. Monitoring — councils and developers monitor boreholes around active-gassing sites; the results live in planning files, which are public.

How to assess a specific worry

1. Search the postcode. Note distance, waste types, and last-input date for anything close.
2. Inert only, or beyond 250m?Gas is not your issue. You're done.
3. Household/commercial waste within 250m? Check the closure age. Last input before ~1985 means the gassing peak is long past. Closed within ~30 years, or dates unrecorded: worth the formal check.
4. The formal check is an environmental search (during a purchase) or a question to your council's environmental health team (any time, free): ask what gas monitoring exists for the site and whether nearby buildings required protection measures.

The honest summary

Landfill gas killed the fear-headline test decades ago: the UK's serious incidents predate modern controls, and the housing stock built near old tips since carries protection by design. Treat a close, recently-closed, household-waste site as a question to answer with monitoring data — and treat everything else as history under the grass.