Methane Gas Facts: Properties, Sources, Uses and Hazards (Landfill Gas Expert Guide)

Methane (CH₄) is the simplest hydrocarbon, the main component of natural gas, and typically around half of landfill gas. It is also the second-largest human-driven greenhouse gas after carbon dioxide. That makes methane gas facts relevant to anyone who manages waste, gas or energy. This guide explains what methane is, how it is produced (naturally and by people), where most of it comes from, what it is used for, how it is collected, and what it does to the atmosphere and to human health, with a practical focus on landfill gas.

Methane Gas Facts at a Glance

• Formula and form: CH₄, a colourless, odourless, flammable gas that boils at −161.5 °C.
• In natural gas: typically about 85–90% methane by volume (reported ranges run from roughly 77% to 92%, depending on the field and processing).
• In landfill gas: typically 45–55% methane, most of the rest being carbon dioxide.
• Climate impact: over 100 years methane warms roughly 27–30 times more than the same mass of CO₂, and about 80 times more over 20 years (IPCC AR6). Its atmospheric lifetime is about 12 years.
• In the atmosphere: the global average reached 1,948 parts per billion (ppb) in 2025, about 2.7 times the 1750 level.
• Where it comes from: roughly 60–67% of emissions are human-caused. Of the human share, about 40% is agriculture, 35% fossil fuels and 20% waste.
• Explosion range: flammable in air between about 5% and 15% by volume.
• Discovery: identified by Alessandro Volta in 1776 in the marshes of Lake Maggiore.

What Is Methane? Methane Gases Meaning and Definition

Methane is a chemical compound with one carbon atom bonded to four hydrogen atoms in a tetrahedral shape. It is the simplest member of the alkane family of hydrocarbons (general formula C_nH_2n+2). Chemically it is the most reduced form of organic carbon: the carbon is in its lowest oxidation state (−4), so once methane has been produced, microbes cannot break it down any further under anaerobic conditions. It is an end product of anaerobic metabolism.

Older texts call it marsh gas (it bubbles from stagnant, oxygen-poor mud), firedamp (in coal mining) or simply natural gas, although that last term really describes a mixture. If you are looking up the methane gases meaning, the plural usually refers to methane together with the methane-rich gas mixtures that contain it: natural gas, biogas, landfill gas and coal-seam gas.

Is Methane a Gas?

Yes. Methane is a gas at normal temperatures and pressures. It only becomes a liquid when refrigerated below −161.5 °C at atmospheric pressure, and it freezes at about −182.5 °C. Above its critical temperature of about −82.6 °C it cannot be liquefied by pressure alone, which is why liquefied natural gas (LNG) is made by deep refrigeration rather than compression. Liquefying shrinks the gas by a factor of roughly 600, the whole point of LNG shipping.

Methane is lighter than air (relative density about 0.55) and only sparingly soluble in water. Pure methane has no smell. The “gas smell” of domestic supplies comes from an odorant (a sulphur compound such as a mercaptan) deliberately added for safety.

Sources for these properties include the Air Liquide gas encyclopedia and the NOAA CAMEO Chemicals datasheet. The net calorific value above is calculated from the heat of combustion.

Who Discovered Methane? When Methane Gas Was First Identified

Methane was first identified in November 1776 by the Italian physicist Alessandro Volta. After reading Benjamin Franklin’s account of “flammable air”, Volta stirred the muddy bottom of the reed beds near Angera on Lake Maggiore and collected the bubbles that rose. He found the gas burned with a slow blue flame and called it “flammable air native to the marshes”. He reported his experiments in letters to Father Carlo Campi, published in 1777, and went on to ignite the gas with an electric spark inside a closed vessel and to build a pistol fired with it. He also correctly linked the gas to the decomposition of organic matter. See the Museo Galileo entry on methane and the Volta archive for details.

Is Methane Natural Gas? How Much Methane Is in Natural Gas?

Methane is the main component of natural gas, but the two are not the same thing. Natural gas is a mixture. Raw gas from the wellhead is typically about 85–90% methane (reported ranges of 77–92% appear in the literature), with ethane, propane, butane, nitrogen, carbon dioxide and sometimes hydrogen sulphide making up the balance. Processing removes the heavier hydrocarbons and impurities before it enters the grid.

The methane content of other methane-rich gases differs considerably, and so does their energy value, because calorific value scales almost directly with methane content:

Landfill gas is a complex mixture: the Environment Agency’s guidance notes that it has been found to contain as many as 557 trace components, including sulphur compounds and siloxanes. As a rule of thumb, net calorific value is about 14 MJ/m³ at 40% methane, 18 MJ/m³ at 50% and 21.5 MJ/m³ at 60%, so a landfill gas supply with falling methane quickly loses its ability to run an engine or even sustain a flare.

How Is Methane Produced?

To fully grasp the core methane gas facts regarding industrial emissions, it helps to examine the three primary routes to methane generation, which account for both natural atmospheric levels and anthropogenic sources.

There are three routes to methane, and most atmospheric methane comes from the first two.

• Biogenic (microbial) methane: made by methanogenic archaea in oxygen-free environments such as wetlands, flooded rice fields, the guts of ruminant animals, digesters and landfills.
• Thermogenic methane: formed when buried organic matter is heated over millions of years, creating natural gas, oil-associated gas and coal-seam gas. It reaches the atmosphere through leaks, venting and incomplete combustion at oil, gas and coal operations, and through natural seeps.
• Abiotic methane: produced by chemical reactions between water and certain rocks, a minor source on a global scale.

The Methane Reaction: How Microbes Make It

Methanogens produce methane by two main pathways. They reduce carbon dioxide using hydrogen, or they split acetic acid:

• CO₂ + 4H₂ → CH₄ + 2H₂O
• CH₃COOH → CH₄ + CO₂

The overall result for a simple sugar such as glucose is C₆H₁₂O₆ → 3CH₄ + 3CO₂, which is why landfill gas is often described as “50:50” methane and carbon dioxide. Measured UK landfill gas is closer to 57:43, partly because carbon dioxide dissolves more readily in leachate. These are the most important reactions in anaerobic processes, which is why methane production is used as a test of the anaerobic biodegradability of a substance.

How Is Methane Naturally Produced?

Natural sources account for roughly a third to 40% of global emissions. The largest by far are wetlands (swamps, bogs and tropical floodplains), where waterlogged soils starve microbes of oxygen. Other natural sources include lakes, rivers and reservoirs, termites, wild animals, the ocean, geological seeps and mud volcanoes, and wildfires. Methane hydrates (methane locked in ice-like cages under permafrost and in ocean sediments) are a large store, but there is no clear evidence of large-scale release at present. Uncertainty in the natural estimates remains high, and exceeds 100% for some inland water systems.

How Is Methane Produced by Humans?

Human activities (anthropogenic sources) make methane in four main ways:

• Agriculture: enteric fermentation in cattle and sheep, manure management and rice cultivation.
• Fossil fuels: leaks, venting and flaring at oil and gas facilities, and coal-mine methane.
• Waste: organic waste decomposing in landfills and wastewater treatment.
• Biomass and biofuel burning: incomplete combustion of wood, crop residues and similar materials.

The Basic Processes of Waste Decomposition

To understand landfill methane gas you need to understand the microbiology and chemistry that produce it, and the leachate that comes with it, during and long after the active life of a site.

The most widely reproduced graph in landfill science was proposed in 1973 by Farquhar and Rovers. It shows how the composition of landfill gas changes with time as waste moves through successive phases. For practical purposes, decomposition of domestic waste can be summarised in three major phases:

Phase 1: Aerobic Decomposition

Oxygen trapped in the waste is consumed rapidly, typically within days or weeks, producing carbon dioxide and heat. In shallow or poorly compacted waste, where air can keep entering, this phase can persist longer and yield significant carbon dioxide.

Phase 2: Acetogenic (Acid) Phase

Anaerobic and facultative bacteria hydrolyse and ferment cellulose and other putrescible materials into simpler, soluble compounds such as volatile fatty acids and ammonia. The leachate becomes strongly polluting: acidic (pH typically 5–6), with a very high biochemical oxygen demand (BOD) (often more than 10,000 mg/l), a high BOD:COD ratio (commonly 0.7 or more, showing most of the organic matter is readily degradable), ammonia typically 500–1,000 mg/l, and a strong, unpleasant smell. This aggressive leachate dissolves other waste components, so it can carry high levels of iron, manganese, zinc, calcium and magnesium. Gas is mainly carbon dioxide, with some hydrogen and only a little methane.

Phase 3: Methanogenic Phase

Slower-growing, oxygen-sensitive methanogens become established once the chemically bound oxygen is used up and conditions turn strictly anaerobic. They consume the acids and hydrogen from Phase 2 and produce a mixture of methane and carbon dioxide, plus trace constituents. Leachate pH rises towards neutral and its strength falls, while gas generation settles at roughly 50–60% methane and can continue for decades, declining gradually over time. Operators model this tail with first-order decay methods; for a simple estimate see our landfill gas production rate quick calculation method.

A correction to an old rule of thumb: methane itself has no odour. The characteristic “landfill smell” comes from trace sulphur compounds and other volatile compounds, so odour is an unreliable indicator of methane or of methanogenic conditions. Always rely on calibrated gas monitoring.

Where Does the Most Methane Gas Come From? Methane Sources

According to the UNEP and Climate and Clean Air Coalition Global Methane Assessment, about 60% of methane emissions are human-caused and about 40% are natural. The more recent Global Methane Budget puts the human share at around two-thirds. Both agree on the main human sectors:

The International Energy Agency’s Global Methane Tracker 2026 adds that energy-sector methane stayed near record highs in 2025, with fossil fuel operations estimated at about 124 million tonnes, and that methane from fossil fuels shows no sign of falling.

Methane in Geography: Where It Comes From, Country by Country

Methane geography matters because emissions are unevenly spread. In 2020 the five largest human-caused emitters were China (16%), India (9%), the USA (7%), Brazil (6%) and Russia (5%). China dominates coal-mine methane, Russia and North America lead in oil and gas, and agriculture and waste dominate in Africa and most of Asia. Natural emissions are concentrated in the tropical wetlands of the Amazon, central Africa and South-East Asia, and in high-latitude peatlands and permafrost. The European Union and Australasia have reduced their human-caused emissions over the past two decades.

In the UK, the waste sector produced around 6% of greenhouse gas emissions in 2024, and landfill was the largest part (55%) of that, according to DESNZ statistics. Methane made up 77% of waste-sector emissions. Waste sector emissions are 61% lower than in 1990. Defra estimates that 57% of UK landfill methane was captured in 2024, with 52% used to generate energy.

Methane meaning in geography: in geography and earth science, the word methane also shows up in terms such as coalbed methane (gas adsorbed in coal seams), gas hydrates, methane seeps and wetland methane. They all describe where methane is stored or released in the landscape.

Methane Greenhouse Gas: Climate Impact and Global Warming Potential

Yes, methane is a powerful greenhouse gas, and the second-largest contributor to human-caused warming after CO₂. Three numbers explain its importance.

• Short lifetime: methane is removed mainly by reaction with hydroxyl radicals in the atmosphere. The IPCC AR6 perturbation lifetime is 11.8 years; you will also see about 9 years quoted as the average residence time, depending on definition. Carbon dioxide persists for centuries.
• High potency: per tonne, methane traps far more heat than CO₂ while it lasts. This is expressed as global warming potential (GWP).
• Rising concentration: the WMO Greenhouse Gas Bulletin reports a 2025 global average of 1,948 ppb (up from 729 ppb in 1750). Copernicus notes this is the highest level in at least 800,000 years. NOAA recorded its largest annual rise (17 ppb) in 2021, and Copernicus reports the 2025 rise was below the average since 2020.

Older figures are still common: 21 (IPCC Second Assessment Report), 23 (Third), 25 (Fourth) and 28 (Fifth). The fossil and non-fossil values differ because the fossil value includes the extra CO₂ formed when methane eventually oxidises, whereas for biogenic methane that carbon is treated as part of the short-term carbon cycle. Methane from landfills is biogenic, but always check which value your reporting framework requires. See the IPCC AR6 Working Group I, Chapter 7 for the source tables.

Because methane is so short-lived, cutting emissions cools the climate quickly. The Global Methane Assessment found that a 45% cut in human-caused methane by 2030 could avoid nearly 0.3 °C of warming by the mid-2040s. The Global Methane Pledge, launched at COP26 in 2021, aims for a 30% cut from 2020 levels by 2030, but the IEA warns that current policies would deliver only around a 20% cut in oil and gas methane by 2030.

Worked Example: What 1,000 m³/h of Landfill Gas Means

Take a landfill gas flow of 1,000 normal m³/h at 50% methane, running all year (8,760 hours):

• Methane flow: 500 m³/h, or 4.38 million m³ a year.
• Mass at 0.717 kg/m³: about 3,140 tonnes of methane a year.
• If vented, that is about 84,800 t CO₂e (GWP-100 of 27.0), or 93,600 t CO₂e (29.8), or around 250,000 t CO₂e on a 20-year view (79.7).
• If burned, each tonne of methane becomes 2.75 tonnes of CO₂ (44/16), roughly 8,600 t of biogenic CO₂ a year. That is why capture and combustion cuts the warming impact so sharply.
• Energy content: 500 m³/h × 35.8 MJ/m³ is about 5 MW thermal, or roughly 2 MW electrical at about 40% engine efficiency.

For power generation economics see our guides to landfill gas project feasibility and landfill gas engines, and our article on carbon credits.

What Is Methane Gas Used For?

• Heating and cooking: as the main component of piped natural gas.
• Electricity generation: burned in gas turbines and reciprocating engines, including landfill power plants and combined heat and power (CHP) units on digesters.
• Biomethane: biogas or landfill gas upgraded to over 90% methane and injected into the gas grid or used as vehicle fuel.
• Transport fuel: compressed natural gas (CNG) and LNG for vehicles and ships.
• Hydrogen production: steam methane reforming is currently the dominant industrial route to hydrogen.
• Chemical feedstock: a raw material for methanol, ammonia (and so fertiliser) and many other chemicals.

How to Collect Methane Gas

How you collect methane depends on the scale and the source.

• In a laboratory: methane is collected by downward displacement of water (a water-filled inverted jar over a trough), because it is sparingly soluble in water. This is essentially what Volta did with marsh bubbles. It must be done away from any ignition source, and only under proper supervision.
• At a digester: biogas rises into a gas-tight membrane holder or dome, is cleaned (hydrogen sulphide, moisture, sometimes siloxanes) and sent to an engine, boiler or upgrading unit.
• At a landfill: methane is drawn out through a network of vertical wells and horizontal collectors installed in the waste. Wellheads feed header pipework and a blower or booster that applies a controlled vacuum, with condensate removed from the pipework, before the gas goes to an engine or a flare. The operator has to balance extraction against air ingress: pulling too hard draws oxygen into the waste, which dilutes the gas and risks fires.

For practical design advice see our guides to landfill gas extraction well design and extraction pipework. Collection is only half the job: surface emissions monitoring and flare monitoring prove the gas is actually being controlled. In England, the Environment Agency’s LFTGN03 sets the framework for landfill gas management, and LFTGN07 covers surface emissions monitoring. Where methane is too low to support an engine or flare, permit guidance expects biological methane oxidation.

Effects of Methane Gas on Humans: Health and Safety

When evaluating the safety protocols required on-site, critical methane gas facts remind us that methane is not toxic at the levels people normally meet, and low-level exposure is not considered harmful. Instead, the primary operational dangers are explosion and asphyxiation.

Methane is not toxic at the levels people normally meet, and low-level exposure is not considered harmful. The dangers are explosion and asphyxiation.

• Explosion: methane is flammable between about 5% and 15% in air. An ignition source such as a spark, a hot surface or static discharge in that range can cause a fire or explosion.
• Asphyxiation: methane is a “simple asphyxiant”. At very high concentrations it displaces oxygen and can cause headache, dizziness, nausea, slurred speech, confusion, loss of consciousness and death. Asphyxiation concentrations (around 50% by volume) are far above the explosive range, so explosion is almost always the first hazard. At 5% methane the oxygen level is still about 19.9%.
• Cold burns: contact with liquefied methane (LNG) can cause frostbite and eye damage.
• Exposure limits: many jurisdictions set no formal workplace exposure limit for methane. Some health guidance cites 1,000 ppm (0.1%) as an 8-hour workday benchmark (see the Pennsylvania Department of Health fact sheet), and in practice detectors are set to alarm at a small fraction of the lower explosive limit.

Landfill gas adds two operator-specific hazards. Because it contains a lot of carbon dioxide, its density is close to or above that of air (around 1.1 relative to air for typical landfill gas, versus about 0.6 for natural gas), so it can collect in low-lying areas, manholes, cellars and confined spaces and migrate sideways through soil and fissures into buildings. It can also contain hydrogen sulphide. The 1986 explosion at Loscoe in Derbyshire, which destroyed a bungalow, is a well-known UK example of migrating landfill gas and shaped later regulation. Never rely on smell: methane is odourless, so use calibrated detectors, follow permit-to-work and hot-work procedures, and see our guide to landfill gas monitoring procedures. More on this topic is in our health and environmental impact category.

Interesting Facts About Methane Gas

• Volta’s experiments with marsh gas included a pistol that fired when its “flammable air” was ignited by a spark.
• Natural gas has no smell as it comes out of the ground. The smell is added for safety.
• One cubic metre of liquefied methane expands to roughly 600 cubic metres of gas.
• Landfill gas can contain hundreds of trace compounds on top of its methane and carbon dioxide.
• Methane is the reason Uranus and Neptune look blue: it absorbs red light in their atmospheres.
• Saturn’s moon Titan has lakes and rivers of liquid methane and ethane.
• Atmospheric methane is now higher than at any time in at least 800,000 years.

Facts About Methane for Kids

• Methane is a gas you cannot see or smell. It is made of one carbon atom and four hydrogen atoms.
• Tiny microbes make methane when they break down plants and food waste in places with no air, such as swamps, the stomachs of cows, and rubbish tips.
• Cows and sheep make methane as they digest grass, and most of it comes out as burps.
• The gas on a kitchen stove is mostly methane. It burns easily, which is why it is useful, and also why it must be handled safely.
• Methane traps heat in the air, so it contributes to climate change, but it disappears from the air after about ten years, so cutting it helps quickly.
• People can catch methane from rubbish tips and farms and burn it to make electricity and heat instead of letting it escape.

Methane Gas Facts FAQ

Keeping these essential methane gas facts in mind ensures that operators, regulators, and engineers can maintain compliance, optimize gas capture efficiency, and mitigate environmental risks effectively.

Is methane heavier or lighter than air?

Pure methane is lighter than air and rises. Landfill gas, which also contains a lot of carbon dioxide, can be about the same density as air or heavier, so it can pool in low-lying spaces.

Is methane poisonous?

Not in the usual sense. It is non-toxic at low levels but can cause asphyxiation at very high concentrations and is explosive between about 5% and 15% in air.

What is the difference between methane and carbon dioxide?

Methane is a hydrocarbon fuel with a short atmospheric life (about 12 years) and a high warming potential per tonne. Carbon dioxide is the end product of burning methane and persists for centuries but is far less potent per tonne.

Why is methane more important in the short term?

Because it is short-lived and potent, cutting methane lowers warming within a decade or two, which is why national programmes focus on landfills, farming, and oil and gas leaks.

How much methane does landfill gas contain?

Typically about 45–55% by volume, with most of the rest carbon dioxide. Measured UK landfill gas averages closer to 57% methane in a 57:43 methane to carbon dioxide ratio.

Is methane the same as biogas?

No. Biogas, including landfill gas, is a mixture made mostly of methane and carbon dioxide. It can be upgraded into biomethane, which is almost pure methane.

Need Help With a Landfill Gas Problem?

If you need independent engineering advice on landfill gas collection, monitoring, flaring or energy recovery, use our contact form to ask for a free quotation from IPPTS Associates. You can also browse our landfill gas regulations and landfill gas recovery articles.

References and Further Reading

1. IPCC (2021). AR6 Working Group I, Chapter 7: The Earth’s energy budget, climate feedbacks and climate sensitivity (GWP and lifetime values).
2. WMO (October 2026). Greenhouse Gas Bulletin No. 22 (2025 global methane concentration).
3. Copernicus Climate Change Service. Greenhouse gas concentrations.
4. NOAA Global Monitoring Laboratory. Trends in atmospheric methane.
5. UNEP and Climate and Clean Air Coalition. Global Methane Assessment (2021), and the Global Methane Status Report 2025.
6. Global Carbon Project. Global Methane Budget 2024 (summary coverage).
7. International Energy Agency (2026). Global Methane Tracker 2026.
8. DESNZ statistics via LetsRecycle (February 2026). Waste sector greenhouse gas emissions fall by 4% in 2024.
9. Defra parliamentary answer (17 July 2026). Landfill methane capture in 2024.
10. Environment Agency. LFTGN03: Guidance on the management of landfill gas; LFTGN07: Monitoring landfill gas surface emissions; Manage landfill gas.
11. Air Liquide. Methane gas encyclopedia; NOAA. CAMEO Chemicals: Methane.
12. Museo Galileo. Methane; Alessandro Volta and methane.
13. Pennsylvania Department of Health. Methane fact sheet.
14. Wikipedia. Atmospheric methane.

Note: Links with a  line through them usually means that you will be required to prove you are human before gaining access.

Updated October 2026 (first published November 2012).