Landfill gas emissions are one of the most important indicators of how effectively a landfill is being managed. Methane escaping through a damaged cap, an inadequately controlled tipping area, leaking wellhead connections or an underperforming gas extraction system represents more than a greenhouse gas problem. It may indicate defects in the containment system, inadequate gas collection, avoidable environmental impacts or risks requiring engineering intervention.
For landfill operators, the practical questions are: Where is gas escaping? How much is being emitted? What is causing the emissions? And what measures will achieve a lasting reduction?
This guide explains how landfill gas emissions are assessed, monitored and controlled, with particular reference to UK Environment Agency guidance and developments in methane measurement research published in 2026.
Written by Steve Last, Chartered Civil and Environmental Engineer, Chartered Waste Manager and Chartered Environmentalist, IPPTS Associates. Updated October 2026.
Key Takeaways: Landfill Gas Emissions
- Gas generation and gas emissions are not the same thing. Landfill gas may be generated within a waste mass without all of it escaping into the atmosphere.
- Methane can escape through multiple pathways, including landfill surfaces, temporary caps, side slopes, defective seals and gas collection infrastructure.
- Surface monitoring normally begins with leak detection. Quantitative flux measurements then assess methane escaping through representative capped areas.
- The Environment Agency specifies different surface methane flux standards for permanently capped and temporarily capped zones at applicable permitted sites.
- Effective control requires more than installing extraction wells. Cap integrity, gas system availability, condensate removal and appropriate extraction balancing all matter.
- Newer whole-site measurement techniques are helping researchers assess landfill methane collection performance, although they do not automatically replace established permit monitoring requirements.
What Are Landfill Gas Emissions?
Landfill gas is generated principally by the decomposition of biodegradable waste under anaerobic conditions. It commonly contains substantial proportions of methane (CH4) and carbon dioxide (CO2), together with water vapour and smaller concentrations of other gases and volatile compounds.
The precise composition varies with waste type, age, moisture conditions, operational practices and the degree of air ingress. A commonly used approximate composition is 50% methane and 50% carbon dioxide, but this should never be assumed to represent the actual composition at an individual site without supporting measurements.
It is important to distinguish three quantities:
- Gas generation: the rate at which landfill gas is produced by decomposition within the waste mass.
- Gas collection: the quantity recovered through the landfill gas extraction system, commonly measured as gas flow and methane concentration.
- Gas emissions: the gas that escapes from the landfill system to the atmosphere, whether diffusely through the surface or through identifiable emission pathways.
These quantities are related, but they are not interchangeable. Some methane can also be oxidised by microorganisms in landfill cover materials before reaching the atmosphere. Gas storage and pressure changes within the waste mass can further complicate the relationship between instantaneous measurements.
Consequently, the methane generation rate predicted by a model should not simply be presented as the actual rate of uncontrolled atmospheric emissions.
For a discussion of the broader greenhouse gas implications, see our separate article on landfill methane emissions and the benefits of reducing them.
Where Do Landfill Gas Emissions Escape?
Landfill gas follows pathways governed by gas pressure, permeability, extraction-induced pressure gradients and the physical condition of the surrounding materials. Escaping gas may be distributed across large areas or concentrated at individual defects.
1. Temporary Caps and Active Landfill Areas
Operating landfills present particular challenges because waste placement, settlement, changing surface levels and progressive cell development can make it difficult to maintain continuous gas containment.
Temporary cover arrangements may not achieve the same degree of gas containment as a properly constructed permanent cap. Where waste continues to generate gas before a permanent system can be installed, suitably designed temporary extraction arrangements may be needed.
The Environment Agency’s guidance on landfill design and construction addresses temporary gas extraction and control during landfill development.
2. Permanent Capping Defects
Permanent capping systems provide an important barrier to uncontrolled gas escape. However, even a well-constructed cap can develop defects as a result of settlement, differential movement, erosion, damage during maintenance or deterioration around penetrations.
Typical potential emission locations include:
- Cracks in cover soils or engineered sealing layers.
- Areas of differential settlement.
- Interfaces between successive phases of capping.
- Gas well penetrations and seals.
- Leachate wellheads and other service penetrations.
- Perimeter interfaces and side slopes.
A defect occupying only a small area can produce a disproportionately large methane release. This is why surface emission surveys should distinguish individual high-emission features from measurements representative of the surrounding cap.
3. Gas Collection Pipework and Wellhead Leakage
Landfill gas collection systems normally operate under applied suction. Nevertheless, leaks and ineffective connections can reduce gas recovery or cause uncontrolled escape, depending on the local pressure conditions and system operating state.
Common engineering problems include displaced wellhead seals, damaged flexible connections, inadequately maintained valves, fractured pipework and condensate blockages.
These problems may become more pronounced as a landfill settles and changes shape over time.
For a more detailed explanation of network construction and maintenance, see our landfill gas extraction pipework guide.
4. Poorly Controlled Extraction Zones
Some parts of a landfill may receive insufficient gas extraction because of inadequate well coverage, poor network balancing, high liquid levels, loss of suction or low system availability.
Conversely, excessive local suction can encourage air ingress, particularly around defective wellheads or permeable areas. This may introduce oxygen and increase operational risks.
The objective is therefore not simply to apply the maximum possible vacuum. It is to achieve effective and stable gas recovery while maintaining appropriate operating conditions throughout the waste mass and extraction network.
Why Are Landfill Gas Emissions Hazardous?
Landfill gas emissions can cause environmental, operational and safety problems. The nature and severity of the risk depend on the gas composition, emission pathway, exposure conditions and proximity of sensitive receptors.
Methane and Greenhouse Gas Emissions
Methane is a powerful greenhouse gas. Uncontrolled methane emissions from biodegradable waste disposal therefore contribute to climate change.
Capturing landfill gas for energy use or destroying its methane content through appropriately operated combustion equipment can reduce direct methane emissions. However, energy recovery and combustion equipment also have their own environmental and operating requirements.
This article concentrates on assessment and engineering control rather than repeating the detailed climate discussion in our landfill methane emissions guide.
Flammability and Explosion Risks
Methane can form flammable mixtures with air. Where landfill gas migrates into a building, chamber, service duct or other confined space, an accumulation may create a fire or explosion hazard if a suitable ignition source is present.
The risk must be assessed in the context of the actual gas concentrations, ventilation, sources of ignition, ground conditions and migration pathways.
Gas migration into surrounding ground or buildings is a related but distinct issue from methane escaping vertically through a landfill cap. Each requires an appropriate investigation and monitoring strategy.
Asphyxiation and Exposure to Trace Gases
Landfill gas can displace oxygen in poorly ventilated spaces. The resulting oxygen-deficient atmosphere can present a life-threatening hazard.
Although methane itself is not generally considered toxic at ordinary exposure concentrations, landfill gas may contain hazardous constituents, including hydrogen sulphide and other trace compounds. Their presence and concentration depend on the waste and site conditions.
Confined-space entry, hazardous atmosphere assessment and occupational exposure controls should therefore be based on appropriate risk assessments and competent monitoring rather than assumptions about average landfill gas composition.
Odour and Local Environmental Effects
Many odorous components of landfill gas are detectable at very low concentrations, even where methane itself cannot be detected by smell.
Odour complaints may indicate gas management problems, although odour alone cannot establish methane emission rates.
Subsurface gas movement can also displace oxygen in soils and affect vegetation. Unusual vegetation stress can be a useful indication of a possible gas problem, but should not be treated as proof without appropriate investigation.
How Are Landfill Gas Emissions Measured?
There is no single monitoring technique that answers every landfill gas emissions question. The appropriate method depends on whether the objective is to locate leakage, quantify surface flux, assess perimeter migration, estimate whole-site emissions or verify the performance of the extraction system.
For permitted landfill sites in England, an important starting point is the Environment Agency’s LFTGN07 guidance on monitoring landfill gas surface emissions.
Stage 1: Surface Walkover and Leak Detection
A surface walkover survey is used to locate areas where methane concentrations indicate possible defects or elevated emissions.
Suitable gas detection equipment is used systematically across the relevant landfill areas, with attention to potentially vulnerable features such as cap joints, wells, pipe trenches, leachate infrastructure and areas of settlement.
The survey should be supported by consideration of site drawings, capping history, previous monitoring results, gas system operating conditions and weather.
Areas of elevated methane concentration require investigation and, where appropriate, remedial action. A concentration measured immediately above the ground is not itself a direct measurement of mass emission rate.
Stage 2: Quantitative Methane Flux Surveys
After identifiable defects have been investigated and remedied, representative measurements can be undertaken to quantify methane flux through the remaining capped surface.
One established technique uses a methane flux chamber, commonly called a flux box.
The chamber is placed over a defined surface area and methane measurements are used to calculate the rate of release from that area, according to the relevant survey procedure.
Flux is commonly expressed as a mass of methane emitted per square metre per second:
mg CH4/m²/s
Results from multiple representative measurement locations are then used to assess emissions from the relevant capped zones. Individual features with distinctly elevated emissions should be considered separately rather than allowed to disappear within a broad zone average.
For more information, see our detailed article on methane flux boxes for landfill gas cap monitoring.
Limitations of Surface Surveys
Monitoring results may be affected by atmospheric pressure, wind, rainfall, soil moisture, temperature, surface condition and the operation of the gas extraction system.
Consequently, a single survey represents conditions at the time of measurement. It should not automatically be interpreted as proving that emissions remain unchanged throughout the year.
The monitoring programme should be designed around the permit requirements, relevant guidance, site conditions and the management decisions that the results need to support.
UK Landfill Gas Surface Emission Standards
The Environment Agency’s published guidance specifies different average methane surface flux standards for different types of capped landfill zone.
| Landfill zone | Surface methane flux standard |
|---|---|
| Permanently capped zone | 0.001 mg/m²/s |
| Temporarily or interim capped zone | 0.1 mg/m²/s |
Source: Environment Agency, LFTGN07, Table 2.1, and Landfill operators: monitor and report your performance.
These are average flux standards for the relevant capped zones, not general atmospheric methane concentration limits or automatic compliance criteria for every part of every landfill.
Identifiable emission features must be considered separately, and the environmental permit and approved site-specific management arrangements remain important.
The quoted standards should not be applied without qualification to active uncapped tipping areas, unrelated installations or historic unpermitted sites.
Where surveys identify excessive emissions, operators may need to investigate defects, review the landfill gas management plan, carry out remedial works and verify whether the corrective measures have been successful.
Whole-Site Methane Measurement: Developments in 2026
Conventional surface monitoring is particularly valuable for locating defects and assessing emissions from capped landfill zones. However, it does not always provide a straightforward estimate of the total quantity of methane escaping from every part of a landfill site.
This distinction is becoming increasingly important as operators, regulators and researchers seek to understand the effectiveness of landfill gas capture at whole-site scale.
Environment Agency Research Published in February 2026
On 2 February 2026, the Environment Agency published its research report Landfill Methane: Measurement and Metrics.
The research investigated methods of quantifying landfill methane emissions and considered how the resulting measurements could help assess landfill gas management performance.
Two measurement approaches were investigated:
- Tracer Dispersion Method (TDM): a technique that uses a released tracer gas and downwind measurements to help estimate methane emissions from the site.
- Unmanned Aerial Vehicle (UAV) mass-balance measurement: an approach using airborne measurements and atmospheric information to estimate methane transported away from the landfill.
The research found that both methods could be effective, but their suitability and results depend on site conditions and survey circumstances. The methods are not necessarily usable at every site or in all weather conditions.
August 2026 Supplementary Research
The Environment Agency published a supplementary research report on 7 August 2026.
This continued the investigation using further whole-site surveys and provided additional evidence concerning the measurement methods and methane collection efficiency.
One of the important findings of the research programme concerns methane collection efficiency (MCE), a metric intended to relate the quantity of methane recovered by the extraction system to estimated methane production.
Conceptually, methane collection efficiency can be expressed as:
Methane collection efficiency = methane collected / estimated methane produced
For a simplified site methane balance, estimated production may be assessed from collected methane, atmospheric methane emissions and methane oxidised in cover material, subject to the assumptions and limitations of the method.
This is an important development because methane capture performance cannot reliably be assessed from extraction flow alone without considering how much methane is escaping.
However, the research does not mean that whole-site aerial or tracer surveys have automatically replaced conventional surface surveys or become mandatory for every landfill. Current permit requirements and applicable monitoring guidance must still be followed.
See the Environment Agency’s February 2026 research summary and August 2026 supplementary summary.
How Can Landfill Gas Emissions Be Reduced?
Successful emission control requires an integrated approach. Capping, gas extraction, monitoring and routine operation must work together.
Where excessive emissions are identified, a structured engineering investigation is preferable to making arbitrary adjustments to the extraction system.
1. Identify and Repair Capping Defects
Monitoring results should be used to identify specific defects or zones requiring attention.
Remedial works may involve repairing damaged capping, restoring soil cover, resealing infrastructure penetrations, addressing settlement defects or improving temporary containment arrangements.
Following repair, repeat monitoring may be necessary to verify that the problem has been corrected.
2. Improve Gas Extraction Performance
The gas extraction system should provide effective coverage of gas-generating waste while maintaining stable and appropriate operating conditions.
Potential corrective measures include:
- Checking wellhead vacuum, gas flow and gas composition.
- Reviewing the distribution of suction across the wellfield.
- Investigating wells with unexpectedly poor gas recovery.
- Checking for air ingress and excessively applied vacuum.
- Inspecting damaged wells and connections.
- Considering additional or replacement collection infrastructure where justified.
System modifications should follow an assessment of the underlying problem rather than relying solely on increased blower suction.
For an explanation of collection system principles, see our landfill gas collection systems article.
3. Prevent Condensate Accumulation and Network Restrictions
Landfill gas is commonly saturated with water vapour when generated. Cooling within extraction pipework can produce condensate, which must be managed appropriately.
Accumulated liquid can obstruct gas flow, reduce the effective suction available at wells and contribute to poorly performing extraction zones.
Routine inspection of condensate management equipment, pipe gradients, knock-out pots, pumps and drainage arrangements is therefore part of effective emission control.
See our technical guide to landfill gas extraction pipework.
4. Maintain Flares and Other Gas Treatment Equipment
Gas extraction cannot provide continuous methane control if the collected gas has no dependable route to suitable treatment or utilisation.
Loss of a gas engine, upgrading plant, blower or flare can compromise gas management unless suitable contingency arrangements are available.
Operators should therefore consider equipment availability, planned maintenance, standby arrangements, alarm response and procedures for gas treatment interruptions.
Reliability is particularly important where a landfill continues to generate substantial gas quantities but has declining or variable commercial energy recovery opportunities.
5. Monitor Changes as the Landfill Ages
Landfill gas management requirements change over time.
Gas generation generally declines as biodegradable material is depleted, but the decline may vary substantially between waste deposits and be affected by moisture and other conditions.
Extraction infrastructure that performed adequately during an earlier phase of site development may not remain optimally balanced indefinitely.
At older and closed landfills, it may be necessary to review equipment capacity, low-flow operating arrangements, wellfield coverage and the suitability of the gas treatment strategy.
A declining collected gas flow is not, by itself, evidence that uncontrolled emissions have fallen proportionately. Monitoring information is needed to distinguish reduced generation from deteriorating collection performance.
Diagnosing Excessive Landfill Gas Emissions: A Practical Engineering Approach
When surface monitoring identifies excessive methane emissions, a useful starting point is to establish whether the problem is localised, widespread or associated with a recent change in site operation.
| Monitoring observation | Possible causes to investigate |
|---|---|
| Elevated methane close to a wellhead | Damaged seals, poor connections, settlement or local extraction problems. |
| High readings along a cap joint | Cap damage, differential settlement or inadequate sealing. |
| Broad area of elevated surface emissions | Insufficient extraction coverage, poor cap performance or changes in gas pressure. |
| Reduced gas recovery accompanied by increased emissions | Blocked pipework, condensate accumulation, equipment faults or loss of system suction. |
| Elevated oxygen in extracted gas | Air ingress through wells, damaged infrastructure, cover defects or excessive suction. |
| Increased emissions during treatment equipment downtime | Loss or restriction of gas extraction or inadequate treatment contingency arrangements. |
These are diagnostic possibilities, not definitive diagnoses. Each observation must be interpreted using site records, gas monitoring data, system operating information and competent engineering judgement.
A practical investigation will often involve reviewing several sets of evidence together: the emissions survey, wellfield monitoring, blower performance, gas composition, condensate system condition, site development history and the timing of operational changes.
Where remedial work is undertaken, follow-up measurements should be used to confirm whether it achieved the intended result.
Landfill Gas Emissions Modelling: What Can LandGEM and Other Models Tell Us?
Landfill gas generation models can assist with long-term planning, extraction system design, equipment selection and estimates of future gas availability.
For example, the US Environmental Protection Agency provides the Landfill Gas Emissions Model (LandGEM), which uses waste information and model parameters to estimate gas and pollutant generation or emission rates.
Model outputs should be interpreted in relation to their assumptions, input data and treatment of gas recovery or other emission-control effects.
There is an important difference between estimating the quantity of gas that might be generated and measuring the methane actually being released to the atmosphere.
For an operating site, models can be valuable forecasting tools, but measured extraction flows, gas composition, surface surveys and any justified whole-site measurements provide necessary evidence about actual performance.
Where regulatory or investment decisions depend on gas generation estimates, model calibration and sensitivity analysis may be appropriate.
Frequently Asked Questions About Landfill Gas Emissions
How does landfill gas escape into the atmosphere?
Landfill gas can escape through permeable waste cover, defective or incomplete capping, side slopes, infrastructure penetrations and damaged collection system components. Emissions depend on gas generation, local pressure conditions, cover integrity and the effectiveness of the extraction system.
How are landfill gas emissions measured?
Surface surveys can locate elevated methane concentrations and quantify emissions through representative capped areas using flux chambers. Other techniques, including tracer dispersion and UAV-based methods, can be used in suitable circumstances to estimate whole-site methane emissions. The method should be selected for the intended measurement objective.
What is the difference between landfill gas concentration and methane flux?
Concentration indicates the amount of methane present in a gas sample, commonly expressed as a percentage or parts per million. Flux describes the mass of methane passing through a unit area in a given time. A concentration reading alone cannot establish an emission rate without an appropriate measurement method.
Is landfill gas toxic?
Methane itself is not normally classified as toxic, but it can displace oxygen and create dangerous atmospheres in confined spaces. Landfill gas may also contain hazardous trace constituents, including hydrogen sulphide. Risks must be assessed according to actual site conditions and gas composition.
Can landfill gas emissions be completely eliminated?
Landfill operators should aim to minimise uncontrolled emissions through effective containment, extraction, treatment and monitoring. In practice, complete elimination of all fugitive emissions may not be achievable, particularly at active landfills and during certain operational or meteorological conditions. Regulatory compliance and continuing performance improvement remain essential objectives.
Does a decline in collected landfill gas mean methane emissions are falling?
Not necessarily. A decline in collected gas may reflect reduced gas generation, but it may also result from extraction system deterioration, changes in moisture conditions, condensate blockages or other problems. Collection data should be assessed alongside field monitoring before conclusions are drawn.
Conclusion: Good Landfill Gas Control Starts with Reliable Evidence
Landfill gas emissions should be treated as a measurable engineering and environmental management issue, not simply as an unavoidable consequence of waste decomposition.
Surface monitoring can identify defects, gas collection data can help assess system performance, and well-planned remedial works can reduce unnecessary methane losses.
More recent whole-site measurement research also provides promising ways to improve understanding of methane capture performance, although these techniques must be used with an appreciation of their limitations.
The most effective approach combines sound containment engineering, appropriately designed gas extraction, reliable treatment equipment, competent monitoring and a willingness to investigate results that do not match expectations.
Landfill Gas Engineering Advice from IPPTS Associates
Need independent advice on landfill gas emissions, gas collection performance or site monitoring results?
IPPTS Associates provides specialist environmental engineering consultancy, drawing on more than 30 years of professional experience in landfill gas management, extraction systems, environmental protection and related infrastructure.
We can assist with reviewing monitoring findings, investigating poor gas recovery, assessing control options and developing proportionate engineering solutions for operational and closed landfill sites.
Contact IPPTS Associates about your landfill gas project to discuss your requirements.
Technical References and Further Reading
- Environment Agency. LFTGN07: Guidance on Monitoring Landfill Gas Surface Emissions. Guidance covering surface surveys, methane flux measurement, emission standards and interpretation.
- Environment Agency. Landfill Operators: Monitor and Report Your Performance. Current online permit guidance covering monitoring and reporting requirements.
- Environment Agency. Landfill Operators: Design and Build Your Landfill Site. Requirements and guidance for landfill engineering and gas control infrastructure.
- Environment Agency, February 2026. Landfill Methane: Measurement and Metrics. Research on methane emissions measurement and potential assessment metrics.
- Environment Agency, August 2026. Landfill Methane: Measurement and Metrics – Supplementary Report. Additional whole-site measurements and investigation of methane collection efficiency.
- United States Environmental Protection Agency. Landfill Gas Emissions Model (LandGEM). Landfill gas and emissions modelling guidance and software.
Technical note: This article provides general professional information, not site-specific permit or safety advice. Requirements vary according to the landfill’s permit, jurisdiction, operating status and environmental risk assessment. Always consult the applicable permit conditions, current regulatory guidance and suitably competent professionals.
[Published November 2012. Updated October 2026.]
Hi. I have checked your landfill-gas.com
and i see you’ve fallen for the lies of
big corporations once again. Warmer air =
quicker growth in nature = problem will
solve itself but big business must make money
out of their scare stories.