In April 2019, a pregnant sperm whale washed up dead on a beach in Porto Cervo, Sardinia, carrying 22 kilograms of plastic in her stomach — carrier bags, a laundry detergent packet, a corrugated tube with its barcode still legible. It's the kind of image most of us associate with plastic pollution: something washed up on a beach, tangled in a net, floating in the open ocean. But the plastic we bin at home every day tells a quieter story. Plastic in landfill doesn't just sit there for centuries — as it breaks down, it also produces methane emissions, a greenhouse gas far more potent than carbon dioxide, for as long as it remains buried.

What Happens to Plastic in Landfill?

So what actually happens to plastic in landfill? Buried or exposed to sunlight and air, plastic slowly degrades and releases methane and ethylene — two potent greenhouse gases — the entire time it sits there, a process confirmed by University of Hawaiʻi researchers in 2018 and reported on by the UN Environment Programme (UNEP).

That finding matters because it overturns a comfortable assumption: that plastic is chemically inert once it's thrown away. It isn't. Every piece of plastic sitting in a landfill or lying in a field is a small, ongoing source of greenhouse gas, not a sealed-off problem we can forget about once the bin lorry has been.

The Hidden Chemistry: How Plastic Produces Methane as It Degrades

The clearest evidence comes from a 2018 study by Sarah-Jeanne Royer and colleagues at the University of Hawaiʻi, published in PLOS ONE. The team tested the most common plastics — polyethylene, polypropylene, polystyrene, PVC and PET among them — and found that all of them released methane and ethylene when exposed to ambient sunlight, with emissions increasing the longer the plastic weathered. Polyethylene, the polymer used in shopping bags and much of our everyday packaging, was the most prolific emitter of the group.

UNEP picked up the story under the headline "Double Trouble", noting that methane traps roughly 86 times more heat than carbon dioxide over a 20-year period, according to the Intergovernmental Panel on Climate Change. That's a meaningful multiplier when you consider how much plastic waste sits in landfill, exposed to sun and air, for years or decades before it's ever fully broken down.

• Methane and ethylene are released by every common plastic type tested, including polyethylene, polypropylene and PET, when exposed to sunlight (Royer et al., PLOS ONE, 2018).
• Methane traps around 86 times more heat than CO2 over a 20-year timeframe, per IPCC figures cited by UNEP.
• Annual plastic flows into the ocean are projected to almost triple, from 11 million tonnes in 2016 to 29 million tonnes by 2040, if nothing changes (Pew Charitable Trusts & SYSTEMIQ, Breaking the Plastic Wave, 2020).

The UK's Landfill Methane Problem

This isn't an abstract, overseas issue. The UK government's own Methane Action Plan, published in October 2025, set a target to raise landfill gas capture rates to 85% by 2030 — a tacit admission that a meaningful share of landfill methane is still escaping into the atmosphere today, even at well-run modern sites. Campaign groups including the Clean Air Task Force welcomed the commitment but noted the plan lacks a single measurable overall target, making it hard to track real progress.

We've found that most people simply haven't connected "what I put in the bin" with "greenhouse gas emissions". Landfill methane doesn't make headlines the way an oil spill does — but it's part of the same chain that starts with how much plastic we buy, use once, and throw away.

When Plastic Escapes the System

Some of that plastic never reaches landfill in the first place. In May 2021, the container ship X-Press Pearl caught fire off the coast of Colombo, Sri Lanka, and sank after burning for nearly two weeks. It was carrying an estimated 1,680 tonnes of plastic pellets, or "nurdles" — roughly 75 billion of them — which spilled into the Indian Ocean and washed up along Sri Lanka's coastline within days. The UN later described it as the country's worst maritime disaster, and researchers are still studying its impact on marine plankton years on.

Wildlife bears a disproportionate share of the cost. Researchers at CSIRO estimate that around 90% of the world's seabirds have now ingested plastic of some kind, up from fewer than 5% in 1960 — and the same research team projects that figure will reach 99% of seabird species by 2050 if current trends continue. That's the same broad story as the Sardinia whale: plastic doesn't disappear when it leaves our hands. It ends up somewhere, in something.

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What You Can Actually Do About It

None of this is a reason to feel powerless. Every plastic item reused rather than replaced is one less thing degrading in landfill, or worse, in the ocean. A few genuinely useful places to start:

• Choose refillable over single-use wherever you reasonably can — deodorant, cleaning products, and toiletries are an easy place to begin, since they're replaced so often.
• Check what your council actually recycles — not all plastics are accepted everywhere, and contamination sends good material to landfill anyway.
• Buy less plastic packaging outright, not just "better" plastic packaging — reduction still beats recycling.
• Support brands that name their environmental partners and show their working, rather than using vague "eco-friendly" language with nothing behind it.
• Read up on what happens after the bin — understanding where plastic actually goes makes it easier to make different choices upstream. Our guide to how long plastic really takes to break down in landfill goes into the timelines in more detail.

Where Lifelong Fits In

This is precisely the problem we built Lifelong to chip away at. Every applicator sold funds the removal of 1kg of ocean plastic, through our partnership with Seven Clean Seas. Our Vibes applicators are made from 100% ocean-bound recycled plastic via our partnership with TIDE, rather than new virgin material. And because refills ship as a lightweight powder rather than a pre-mixed liquid, our supply chain cuts transport emissions by up to 94% compared with conventional deodorant formats.

We're not claiming to have solved landfill methane on our own — nobody's product does that. But a refillable applicator, bought once and topped up for years, is one fewer plastic container that ever needs to reach a landfill site to begin with. If you'd like to see how the refillable applicator system works, or explore the full range at lifelongdeo.com, we'd love to have you.

Frequently Asked Questions

Does plastic in landfill really produce methane emissions?

Yes. A 2018 University of Hawaiʻi study published in PLOS ONE found that common plastics, including polyethylene, release methane and ethylene as they degrade in sunlight, with emissions increasing the longer the plastic is exposed. This happens at landfill sites where plastic isn't fully buried and shielded from air and light.

How much methane comes from UK landfill sites?

The UK government's October 2025 Methane Action Plan set a target to raise landfill gas capture rates to 85% by 2030, which shows a meaningful share of landfill methane is still escaping capture today. Waste remains one of the largest sources of methane emissions the UK has left to tackle.

How long does plastic take to break down in landfill?

It varies by plastic type and conditions, but most everyday plastics take decades to centuries to fully break down in landfill. During that time, any plastic exposed to sunlight and air can keep releasing greenhouse gases.

Can recycling stop landfill methane emissions?

Recycling helps reduce the volume of new plastic sent to landfill, but it doesn't solve the problem alone — contamination and limited local capacity mean a lot of collected plastic still ends up buried. Reducing overall plastic use and choosing refillable products cuts the problem off further upstream.

What is the biggest source of plastic-related greenhouse gas emissions?

Plastic's climate impact isn't limited to landfill — manufacturing new plastic from fossil fuels is carbon-intensive at every stage. Landfill methane is one part of a longer chain, which is why reducing production and reuse matter as much as disposal.

Adam Webb is the founder of Lifelong Deo, a UK-based refillable deodorant brand working to remove ocean plastic through its partnership with Seven Clean Seas.