A guide to monitoring and quantifying methane emissions from the waste sector

Methane is a greenhouse gas and climate pollutant that is responsible for roughly half a degree Celsius of the warming we are currently experiencing, making its emissions a critical target for mitigation in global efforts to stop climate change. The launching of the Global Methane Pledge by the United States and European Union in 2021 propelled methane mitigation efforts into the spotlight, with signatory countries committing to reduce their collective methane emissions. Since COP26, 155 countries have signed onto the pledge and committed to reducing global methane emissions by 30% by 2030.  

The vast majority of human-driven methane emissions stem from three sectors: agriculture, fossil fuels, and waste. Within each sector, numerous low-cost abatement measures have been identified and some of the biggest opportunities are in the waste sector. Indeed, the waste sector is responsible for roughly 20% of anthropogenic methane emissions, which are released when organic wastes – food and yard waste, paper, cardboard, wood, and bodily wastes – break down in the oxygen free environment found in landfills, dumpsites, and wastewater facilities around the world. 

Until a few years ago, methane pollution spilling from landfills and dumpsites was not a high priority for most governments. Fortunately, this is changing through the momentum of the Global Methane Pledge, as well as with advances in remote sensing technologies that are allowing us to see this invisible pollutant and more easily target sources of emissions. Building on these advances and examples from the oil and gas sector, we believe that these tools can inform policies that will help us efficiently eliminate methane pollution.  

How monitoring and quantifying waste methane emissions works 

Landfill emissions have traditionally been estimated using first order decay (FOD) models, which are increasingly criticized for being based on old field studies and faulty assumptions. Studies show that the accuracy of FOD models increase as site-specific data is used, but lack of up-to-date facility level information is an open secret in the waste sector where modeling is often based on defaults, assumptions, and decades old data.  

Fortunately, recent advances in methane emissions monitoring facilitate the detection and quantification of emissions at these sites. From handheld instruments that identify leaks to space-borne technologies that can provide an aerial view of distributed sources, these tools are changing our understanding of methane emissions and expanding the available approaches towards target setting, monitoring, and verification of emissions reductions.  

These technologies achieve three essential tasks: 

• Improving modeled methane estimates: By comparing measurements to modeled estimates of methane emissions from disposal sites we can better understand emissions from these facilities and refine the underlying assumptions currently used in models to improve their estimates. 
• Quantifying emissions and prioritizing sites for mitigation efforts: Emissions measurement can help improve inventories at the local, regional, and national level, which is critical for setting methane reduction goals and tracking progress. Improved facility level estimates can also help to decide how and where to allocate limited financial and capacity resources for mitigation efforts.  
• Screening final disposal sites to pinpoint emissions sources and leaks: Understanding the exact location of methane pollution sources at disposal sites can help operators determine the appropriate practices to reduce emissions. For example, a leak from a gas capture system would require a different approach than emissions stemming from operations at the working face of the facility. 

Measurements at or near the landfill    

One would expect that the most straightforward way to understand landfill emissions is to measure them onsite. Over the years, landfill operators, local authorities, and scientists have used several techniques to understand emissions near the landfill’s surface. Such methods are frequently used to estimate landfill emissions, evaluate the effectiveness of emission models, and detect unexpectedly large emissions (e.g., from faulty landfill covers or malfunctioning equipment). The most basic screening technique is walkover surveys using handheld gas analyzers, which provides only a semi-quantitative view of emissions. In such surveys, an operator carries a portable methane measuring instrument as they walk across the landfill surface (where it is safe to do so) to screen for elevated methane concentrations that would indicate a possible methane leak. These surveys can now also be performed using drones, which can more efficiently monitor the large landfill area, resulting in more methane measurements and, thus, better identification of emissions hotspots. Such measurements are important as they can inform the operators about emissions hotspots and help them diagnose and fix any identified issues. 

To get quantitative emission estimates, a typical strategy is to measure how much methane slips through the landfill surface at a few selected locations. This is typically achieved by using what is called “surface flux chambers.” In essence, these are boxes with an open bottom side which are placed on the landfill surface; a methane measuring instrument monitors how fast the box fills with gas, quantifying the methane emission rate. However, methane emissions within a landfill will vary widely both from place to place and with time, so estimating total emissions using this technique can be time-consuming and inaccurate. Several other techniques, such as combining fast measurements of methane concentration on the landfill with local wind data, can monitor larger landfill areas for emissions. Still, the landfill’s large size, limited accessibility, and typically complex topography make such techniques tricky to use in practice.  

Another way to quantify methane emissions is to try to measure methane away from the landfill, as it is carried away by the wind. This can be done by mounting methane measuring instruments on cars, aircraft, or, lately, even on drones. Such measurements are combined with wind information to calculate total emission rates from the landfill. These methods can give an estimate of total methane emissions, but provide almost no information about the exact source of the emissions. In this way, they can be used to improve emissions inventories, evaluate models, or monitor the performance of a gas-capturing system but not to guide specific mitigation actions at specific locations in the landfill.   

Measurements using remote sensing instruments 

A new generation of instruments, similar to advanced cameras, installed on aircraft and satellites promises to give us a bird-eye view of landfill emissions. These remote sensing instruments, as the cameras are formally called, observe the landfill’s sunlit surface and look for minute changes in radiation intensity that could bear the signature of large methane concentrations above the landfill. These data are combined with wind information and advanced algorithms to both detect emissions and quantify their magnitude. Such techniques were well-known to scientists for a long time but have recently made great strides in terms of practical applications due to improved technology, low-cost access to space, and global interest in methane monitoring, especially in the oil and gas industry. 

The distance between landfills and these instruments still matters, though. Operated from a plane, a typical remote sensing instrument can resolve methane emissions just a few meters apart, giving the operators information about the possible location of methane leaks. Launched on a satellite, instruments lose part of their resolving power. But not all satellite instruments are created equal: some instruments are designed to characterize methane concentrations in the atmosphere over large swaths of areas, such as metropolitan areas and tropical wetlands, while other instruments are designed to detect active but small-size emissions sources, from facilities around the world. The former can be used to estimate total city emissions, while the latter can be used to monitor emissions from specific landfills.  

Remote sensing instruments are already providing new insights for landfill emissions. For example, in 2022, scientists used a combination of satellite instruments to monitor emissions from landfills in Buenos Aires, Delhi, Lahore, and Mumbai; they detected emissions reaching a staggering 29 tonnes of methane per hour and up to 2.6 times the officially reported values. Moreover, they found that landfill emissions can reach up to 50% of the emissions in these cities.  

In separate studies, scientists used remote sensing measurements from aircraft to detect large emissions from landfills in California and Pennsylvania. Using high-resolution methane imaging, they guided the landfill operators to take action to reduce the emissions, while they used new measurements to validate their effectiveness. In Pennsylvania, landfill operators were able to reduce observed emissions by 37%. In California, they also managed to reduce negative odors and complaints from nearby communities that were stemming from the landfill. 

Based on these promising results, we expect that remote sensing from aircraft and satellites will be a game-changer in methane landfill management. In places where regulations are in place, remote sensing can help monitor compliance and drive quick mitigation action in case of malfunctions. In parts of the world that are less well studied and/or less regulated, remote sensing instruments can quickly locate large methane emissions, inform local operators and policy makers, and help prioritize methane mitigation actions. Spaceborne instruments in particular can give us – for the first time – an accurate global view of landfill methane emissions and be the cornerstone of rapid mitigation programs.  

However, remote sensing instruments are not a silver bullet that will solve the waste sector data problem. In most cases, they are better at detecting point sources (i.e., methane emissions coming from a small area of the landfill, such as a leak at a landfill gas wellhead), but could fail to detect distributed sources like methane being emitted from a larger area.  Secondly, their effectiveness could change based on the location and time of the year as their performance depends, among other factors, on cloud cover, snow cover, and prevailing wind conditions. For these reasons, we will be able to make full use of these instruments only as components of a multi-tier monitoring system that will also include ground-based monitoring and modeling with improved facility-specific data to provide accurate methane emission information adapted to the needs of various stakeholders involved in tackling the methane emission problem.    

After methane detection, comes mitigation  

Studies have shown that that up 80% of waste methane emissions could be eliminated with technological solutions that exist today. In fact, up to 60% of mitigation measures have low or negative costs according to the United Nations Environment Programme and Climate and Clean Air Coalition. 

Governments at all levels are already beginning to put solutions in place. Ljubljana, the capital of Slovenia, adopted a zero waste approach in 2014 and has reduced the amount of total waste sent to final disposal sites by 95%. Indore, India’s “Cleanest City” with a population of over 3 million, implemented mandatory source separation, while deploying daily door-to-door collection with over 600 GPS-enabled vehicles; 90% of households in Indore currently separate their waste. For more information on waste mitigation actions and examples from around the world, see our previous blog post on waste methane.  

At Clean Air Task Force, with our partners RMI, we launched the Waste Methane Assessment Platform (Waste MAP) to improve availability and robustness of global waste sector data, enable methane emissions transparency, and share best practices to reduce emissions. We are also working to compile guidance on national-level policies that work to reduce waste methane to highlight “best in class” policies and regulations from source separation mandates to landfill gas capture standards, and identify major gaps.  

Many other resources are available. For example, the Global Methane Initiative has a variety of resources on reducing methane emissions from municipal solid waste and furthering biogas development. Other key resources include RMI, Carbon Mapper, and IG3IS’s report on Key Strategies for Mitigating Methane Emissions from Municipal Solid Waste, and the Global Alliance for Incinerator Alternative’s Methane Matters Report.  

Politik weltweit vorantreiben 

Momentum for increased action is building; countries are recognizing the need to set targets for waste methane and develop roadmaps for their implementation. In August of 2023, Chile’s Minister of Environment, along with a number of mayors, introduced a bill that gradually prohibits the disposal of organic wastes in landfills.  During the North American Leaders Summit in early 2023, the United States, Mexico, and Canada committed to reduce methane emissions from solid waste and wastewater by 15% by 2030 from 2020 levels.  In the EU, the Commission is currently considering data on food waste to determine the feasibility of establishing a Union-wide food waste reduction target for 2030. The EU is also on track to update its Landfill Directive in 2024.   

At the same time as targets are set and regulatory approaches are developed, others are working to overcome significant barriers to the financing of waste methane solutions. At COP28, the Inter-American Development Bank announced 372.5 million USD in dedicated financing for recently approved waste management projects in the region. At the International Solid Waste Association Congress in Oman, the Catalytic Finance Foundation hosted a workshop to identify barriers and enablers to finance waste infrastructure for methane reduction, with the ultimate aim of creating a blended finance investment fund for sustainable waste management infrastructure.

Concurrently, CATF has been working with the U.S. State Department, SCALE Initiative, and a consortium of other partners to support the design of the Lowering Organic Waste Methane (LOW-Methane) Initiative to dramatically accelerate progress on the Global Methane Pledge by highlighting ambitious commitments to cut waste sector methane and mobilizing resources to support them. The LOW-Methane Initiative aims to deliver at least 1 million metric tons of annual waste sector methane reductions well before 2030, working with 40 subnational jurisdictions and their national government counterparts, and to unlock over $10 billion in public and private investment.  

The waste sector’s contribution to methane emissions and climate change has never been a secret, but the Global Methane Pledge brought new attention to this issue in recent years. The momentum generated from the Pledge, as well as improvements in remote sensing technologies, have continued to raise awareness of the importance of this sector as a critical climate solution. To continue increasing transparency and understanding of waste methane emissions estimates and priority interventions, it is critical that countries around the world utilize these recent advances in methane detection to identify emissions, develop policies, and mitigate methane emissions in the waste sector.