The Basics of Greenhouse Gas Emissions From Landfills

If you ask Americans where the country’s greenhouse gas emissions come from, almost everyone names cars and power plants. Those are the two biggest sources, and they get most of the public attention. What very few people name is landfills — but in 2022 the EPA’s Greenhouse Gas Inventory documented that municipal solid waste landfills generated about 14% of total US methane emissions, making them the third-largest human-caused methane source after enteric fermentation (cow burps) and natural gas systems.

The mechanism is unusual. Landfills don’t burn things — they don’t have combustion-related CO2 emissions in any meaningful way. They just sit there, accumulating trash, with topsoil and clay layers on top. Year by year, as the organic material buried inside decomposes, methane comes out the top. That methane is a 28-to-86-times more potent greenhouse gas than CO2 depending on the time horizon used. The slow, invisible release adds up to one of the biggest climate impacts of the American waste system — and it’s also one of the most preventable.

This post walks through the basics: how landfill methane forms, why food and yard waste are the biggest contributors, how the EPA measures the emissions, what landfill operators do about it, and why composting is the alternative that fundamentally changes the math.

Anaerobic decomposition: the chemistry

Decomposition of organic matter (food waste, paper, wood, yard trimmings) happens through one of two pathways depending on oxygen availability:

Aerobic decomposition (with oxygen): The bacteria and fungi that break down organic matter consume oxygen and produce CO2, water, and heat. This is what happens in a compost pile that’s properly aerated. The CO2 produced is biogenic carbon — it came from plants that recently pulled it from the atmosphere — so it’s effectively carbon-neutral in the climate accounting.

Anaerobic decomposition (without oxygen): When oxygen isn’t available, a different set of bacteria break down organic matter and produce methane (CH4), CO2, and trace gases like hydrogen sulfide. The methane is the problem. CH4 has a global warming potential (GWP) of approximately 28 over a 100-year timeframe compared to CO2, and roughly 84-86 over a 20-year timeframe. Per molecule, methane traps heat far more efficiently than CO2.

A landfill is, by design, an anaerobic environment. Trash gets compacted to maximize space utilization. Daily cover material (a layer of soil or alternative material) is added on top to suppress odors, control vermin, and reduce blowing debris. As the landfill grows vertically, the lower layers get buried under hundreds of feet of additional waste. Oxygen exposure is minimal to nonexistent.

Within weeks of burial, the organic material starts decomposing anaerobically. The active anaerobic decomposition phase typically continues for 30-50 years per layer of buried material. Some materials (wood, especially) decompose for 100+ years before stabilizing.

What’s in landfills that produces methane

Not all material in landfills produces methane. The methane comes from biodegradable organic matter — material that bacteria can break down. Specifically:

Food waste is the biggest methane producer per pound. Food waste contains 50-80% water and lots of easily-fermentable sugars, starches, fats, and proteins. Anaerobic bacteria can metabolize all of these quickly. Methane production from food waste typically peaks within 1-3 years of burial. A pound of food waste produces approximately 0.3-0.5 cubic meters of methane over its decomposition lifecycle.

Yard waste (grass clippings, leaves, branches) is the second-biggest producer. The fast-decomposing components (grass clippings, soft leaves) produce methane similarly to food waste. Woody material decomposes slower but produces methane over decades.

Paper and cardboard produce significant methane. The cellulose in paper is anaerobically degradable. Newsprint, office paper, food-contaminated paper packaging — all are major contributors. Glossy magazine paper and coated cardboard decompose slower because of the coatings.

Wood products decompose slowly but produce methane over a long time horizon. Construction debris, wooden pallets, furniture, etc.

Textiles (natural fibers — cotton, wool, linen) decompose anaerobically and produce methane. Synthetic textiles (polyester, nylon) do not.

What does NOT produce methane in landfills:
– Plastics (most varieties don’t decompose meaningfully)
– Metals
– Glass
– Inert construction materials (concrete, stone)
– Most synthetic textiles
– E-waste

The math is striking: even though plastics are 12% of typical MSW (municipal solid waste), they contribute essentially zero to landfill methane. Even though food and yard waste are typically 25-30% of MSW combined, they contribute about 60-70% of total landfill methane.

EPA’s measurements: how much methane and where

The EPA’s Greenhouse Gas Reporting Program requires US landfills above a size threshold to measure and report their methane emissions annually. The aggregate data tells a clear story:

Total US landfill methane emissions: Approximately 105-115 million metric tons of CO2-equivalent annually, based on 2020-2022 EPA estimates. This represents about 14-15% of total US methane emissions and about 2% of total US greenhouse gas emissions when measured on a CO2-equivalent basis at the 100-year GWP.

Largest individual landfill methane sources: The biggest US municipal landfills produce 50,000-150,000 metric tons of CO2-equivalent in methane emissions per year each. The largest emitter in 2022 was a Wisconsin landfill operated by Waste Management at about 130,000 metric tons CO2-eq.

Trend over time: US landfill methane emissions have been roughly flat or slightly declining since 2010, despite continued waste generation increases. This is largely because of methane capture systems (more on these below) and slow improvement in waste diversion programs (recycling and composting).

Regional variation: California, Texas, and the Northeast have the highest absolute landfill methane emissions because they have the largest populations and most landfills. The Pacific Northwest has lower per-capita emissions because of strong composting and methane-capture programs.

Methane capture: what landfills actually do

Most major US landfills now operate methane capture systems. The basic concept: drill vertical wells into the landfill, collect the gas that comes out, route it to either flaring (burning to convert methane to CO2 — better than releasing methane) or energy generation (burning to produce electricity or run a gas turbine).

Capture rates vary:
– A well-designed and well-maintained landfill methane capture system captures 60-80% of the methane the landfill produces.
– A poorly-maintained system captures 30-50%.
– The remaining methane escapes through cap leaks, side migration, or pre-collection emissions in newer areas of the landfill.

Best-in-class landfills approach 90% capture, but these are the exception.

The captured methane then either:

• Gets flared: Converted to CO2 by combustion. The CO2 emissions are 28x less impactful than the methane would have been. Better than venting, but not great.
• Gets used for energy: Powers landfill operations, generates electricity for the grid, or feeds into natural gas pipelines. About 350 US landfills run landfill-gas-to-energy (LFGTE) facilities. The energy use displaces fossil fuel combustion elsewhere, providing additional climate benefit beyond just methane destruction.

The economics of methane capture are improved by the Inflation Reduction Act’s methane fee starting in 2024-2025, which charges large emitters $900 per metric ton of methane above thresholds. This is creating capital investment incentive for better capture systems across the industry.

Why food waste in landfill is uniquely bad

A pound of food waste in landfill produces approximately 5-10x more methane per pound than a pound of paper, and 50-100x more than a pound of inert materials. The combination of high moisture, high sugar/starch/protein content, and rapid bacterial metabolism makes food waste the most efficient methane producer in the waste stream.

The other unique aspect: food waste decomposes fast (1-3 year peak methane production) while methane capture systems are typically installed years after a section of the landfill is buried. Most food waste methane is released before the capture system reaches that depth and pulls gas effectively.

The EPA estimates that food waste is responsible for approximately 58% of landfill methane emissions despite being only 24% of MSW by weight. The disproportionate impact is exactly the gap that diversion programs target.

What composting does to the math

Compostable foodware exists in the right system. So does composting of food and yard waste. When food and yard waste go to an aerobic composting facility instead of a landfill, the methane production is reduced by 80-95%.

The full lifecycle analysis:

Food waste to landfill: Produces 0.3-0.5 m³ methane per pound = approximately 4-7 kg CO2-equivalent per pound of food waste using 100-year GWP.

Food waste to commercial composting: Produces 0.01-0.05 kg methane per pound (some methane production happens even in aerobic systems when anaerobic pockets form temporarily) = approximately 0.1-0.5 kg CO2-equivalent per pound. Aerobic composting also produces N2O (nitrous oxide), which has its own GWP, but total emissions are dramatically lower than the anaerobic landfill pathway.

Net climate benefit of composting per pound of food waste diverted: Approximately 3.5-6.5 kg CO2-equivalent saved.

For perspective, a typical US household generates 219 pounds of food waste per year (USDA Economic Research Service data). Composting that entire stream instead of landfilling it saves approximately 770-1,420 kg CO2-equivalent per household per year — comparable to the carbon impact of driving 1,500-3,000 fewer miles annually.

Scale that up nationally: the 30+ million tons of food waste that goes to US landfills annually represents 100-200 million metric tons of CO2-equivalent emissions when methane is fully accounted for. Composting all of it would be one of the largest single-action climate interventions available — comparable in scale to the electricity sector’s coal-to-gas transition.

State and city programs

Several state and local programs target food waste diversion specifically to address landfill methane:

California (SB 1383): Requires 75% diversion of organic waste from landfills by 2025. Mandatory curbside organics pickup for residents and businesses across most of the state.

Washington state (HB 1799): Phases in commercial organic waste bans 2024-2027. Requires haulers to offer organics collection in most of the state.

Massachusetts: Bans commercial food waste over 1 ton per week from landfills.

Connecticut, Vermont, Rhode Island, New York City: All have commercial food waste bans with various thresholds and timelines.

Seattle, Portland, San Francisco, Berkeley, Oakland, Minneapolis: Have residential curbside organics pickup as part of standard waste service.

EU broadly: Most EU countries have stronger organics diversion programs than the US, ranging from country-wide bans to specific landfill diversion targets exceeding 90%.

The trend is clear: jurisdictions that are serious about climate emissions are pulling organic waste out of landfills as a priority. The methane math is too compelling for the policy not to move that direction.

The role of compostable foodware

Compostable cups, plates, utensils, and packaging don’t just reduce plastic waste — they’re also part of the food-waste-diversion story. A compostable cup with food residue in it can go to commercial composting with the food. A plastic cup with food residue in it can’t go to recycling (food contamination) or composting (plastic contamination) — it must go to landfill.

The systemic interaction is important. A foodservice operation that uses compostable foodware AND has commercial composting pickup can divert close to 100% of its post-consumer waste from landfill. The compostables go to compost with the food. The cleanly-empty packaging goes to recycling. Very little goes to landfill.

A foodservice operation that uses plastic foodware sends 70-90% of post-consumer waste to landfill, regardless of customer recycling effort, because plastic foodware contaminated with food cannot be reliably recycled.

For operators thinking about full waste-stream design, the compostable food containers and related categories enable the integrated approach that makes meaningful diversion possible.

Common misconceptions

“Landfills just need to be vented better.” No. Venting moves methane from underground to the atmosphere — which is what you don’t want. Flaring (combusting to CO2) is better than venting, but neither matches the climate performance of diverting the organic material in the first place.

“Methane capture solves the problem.” Capture is helpful but incomplete. Even best-in-class systems leak 10-20% of total methane. And the methane that’s captured-and-burned still emits CO2, just less potently than the methane would have. Diversion to composting eliminates the methane source entirely.

“Backyard composting doesn’t matter at scale.” True at the individual scale, but municipal organics pickup programs are essentially backyard composting at industrial scale. The same chemistry, the same diversion benefit, just at higher throughput.

“Landfills are the cheapest option overall.” When externalities (climate damage, methane fees, water table impact, neighbor disputes) are priced in, the cost gap shrinks significantly. The Inflation Reduction Act methane fee is one mechanism that’s pricing this externality more accurately starting in 2024-2025.

“This is too small to matter.” Landfills are 14% of US methane emissions. Methane is the second-most-impactful greenhouse gas after CO2. The math is not small.

What the typical household can do

For an individual or household wanting to reduce their share of landfill methane:

1. Compost food waste. Backyard pile, municipal pickup, drop-off site — any of these are dramatically better than trash.
2. Compost yard waste. Same options. Many cities have specific yard waste pickup separate from regular organics.
3. Use compostable foodware when buying single-use products. Especially for events, takeout, parties.
4. Support municipal organics programs. If your city doesn’t have curbside organics pickup, advocate for it.
5. Don’t over-buy food. Reducing food waste at the source is even better than composting it. The EPA’s food waste hierarchy puts “prevent” above “compost” because the carbon savings are larger.

The bigger picture

Landfill methane is a solvable problem. The chemistry is understood, the technology for capture is mature, the policy frameworks are being deployed in leading states and countries, and the consumer infrastructure (curbside organics, commercial composting) is expanding rapidly.

What’s missing in most of the US is the speed of deployment. The benefit-per-dollar of organic waste diversion is among the highest in the climate mitigation portfolio. The barriers are mostly political (zoning for composting facilities, hauler contract complexity, education) rather than technical.

For composting professionals, foodservice operators, and individual citizens, the message is clear: organic waste belongs in compost, not in landfills. The methane math is decisive. Building the infrastructure to make that diversion easy and cheap is one of the most concrete climate actions available.

The cup, the plate, the food waste — all of it can go to compost. The methane that those items would have produced in a landfill stays in the atmosphere instead. Across millions of households and operations, that’s how the third-largest US methane source gets dismantled.

For B2B sourcing, see our compostable supplies catalog or compostable bags catalog.

Verifying claims at the SKU level: ask suppliers for a current Biodegradable Products Institute (BPI) certificate or an OK Compost mark from TÜV Austria, and check that retail-facing copy meets the FTC Green Guides qualifier requirement on environmental claims.