This list shows the 25 sites in the waste sector with the largest detected and quantified emissions rates worldwide, as seen by key satellite instruments in 2025. (We published an initial list in November here.) 

These insights come from Carbon Mapper’s public methane emissions data leveraging two space-based instruments: Planet Labs’ Tanager-1 satellite and NASA’s EMIT instrument on the International Space Station. Data from these instruments are analyzed by Carbon Mapper and published on its data portal. We compiled this list of extreme emitters by identifying the landfills with the highest emissions rates seen from Jan. 1, 2025, to Dec. 31, 2025. 

The data show more than 2,994 plumes from 707 waste sites, including landfills and dumpsites, worldwide. These are sites in dozens of countries of all income levels and in all world regions. While many landfills emit only a few dozen kilograms of methane per hour, those on our “top 25” list emitted much more – ranging from 3.6 to about 7.5 tonnes (metric tons) of methane per hour.  

In this iteration of our top 25 list, we are including a column titled “potentially responsible operator.” This information was not obtained directly from Carbon Mapper. Instead, the information is the result of research conducted by our team at the Emmett Institute. Below, we explain the methodology for that research and welcome feedback.    

Dishonorable Mention

We also bring attention with this release to two “Dishonorable Mention” sites, which we define as sites with emissions rates that fall within our top 25 range if we extend the date range from January 2025 all the way up to April 7, 2026. Those two sites are in Silivri, Turkey and Abidjan, Ivory Coast, with emissions rates of 8.4 tons/hour and 4.6 tons/hour respectively, counting observations since the end of 2025. Notably, the landfill in Silivri, which serves the city of Istanbul, shows a larger emissions rate than any of our top 25 in 2025 sites. The data link for Silivri is here. The data link for Abidjan is here. 

How important are these sources of emissions in the global context?  To illustrate how important these sources are, and what big opportunities they present for near-term reductions, consider that over a year, a landfill emitting 5 tonnes of methane per hour (in the middle of the pack of our top 25 list) would contribute about as much to global warming as one million SUVs or one large (500 megawatt) coal-fired power plant. 

How did we calculate these emissions rates?  We didn’t do the calculations. We are reporting calculations done by Carbon Mapper and included on their public data portal, making some judgment calls about what to include or exclude from our list as we explain below. Carbon Mapper gives source emission rates by averaging the emission rates from each time an instrument observed a source (including times, if any, when no emissions were observed). Carbon Mapper’s methodology for calculating emissions rate is described in more detail here. We obtained source-level methane emission data from Carbon Mapper’s data portal for the year 2025, pulling the data as of April 7, 2026 and focusing on sites that were observed on at least two dates and that show more than one quantified emissions plume. Then we sorted and selected for the 25 largest emitters in the “Solid Waste” category . For those observations, we used an automated process to pull associated emission information and location data from Carbon Mapper. We then used that location data to manually attribute each observation to a specific potentially responsible operator, which we explain at greater length below. For more questions about our methodology, please reach out to Horowitz@law.ucla.edu.   

Why do our emissions rates look a little different than those reported on the Carbon Mapper site? We are reporting the same emission rates but are translating them into a different unit to make it simpler. One metric tonne equals 1,000 kilograms. Because the Carbon Mapper portal has to provide consistent formatting for hundreds of sources whose emissions rates vary from very small to very large, it uses the smaller unit (kg/hr) – for example, Carbon Mapper reports the top site's emission rate as 7.6K kg/hr. Since the top 25 sources all have emissions in the tonnes range, we stated them as tonnes, to make it simpler (e.g., 7.6 tonnes/hr for that top site). 

Is your list equivalent to a list of the biggest landfill methane sources in 2025?  Not entirely, but it’s pretty close. These are the landfills with the largest hourly emission rates that two instruments saw in 2025, but the instruments can’t see everywhere. In particular, they can’t see in the dark or see through heavy clouds. So, while the observations of these sources are solid, it’s possible that there were even more extreme emissions events in 2025 that the instruments couldn’t see (or that we excluded from this list because of too-few observations, as noted below). Moreover, landfill emission rates do vary somewhat over time, so capturing high hourly emission rates on a set of particular dates is not the same as knowing how much a landfill emitted, in total, across an entire year.  Nevertheless, in our judgment this is about as close as one can get, given current data, to a list of the largest landfill emitters in 2025. 

It’s also possible that over time, Carbon Mapper may update its own estimates of observed emissions rates from these sites, either because of new data or because of changes in the way Carbon Mapper interprets its data. Our list uses Carbon Mapper data and estimates as reported on April 7, 2026. 

Does the list include every big emissions event the satellites saw?  No. Because of differences in the satellites’ orbits, some of these landfills were seen dozens of times in 2025, others just a few times. To be careful, we only included landfills that were observed on at least two days and for which there are at least two quantified observations. So, there are a few landfills with extremely high emissions rates that appear on Carbon Mapper’s portal, but that we excluded from this list because they were only observed once. 

Where can I learn more about methane observation from satellites?  To learn more about remote observation of methane and the opportunities and limitations presented by the new satellite data, see the Emmett Institute’s “Remote Sensing of Atmospheric Methane: A Primer for Policymakers on the Science of Methane Satellites.”  

How did we determine potentially responsible operator information? In this iteration of our top 25 list, we are including a “potentially responsible operator” column. This information was not obtained directly from Carbon Mapper. Instead, the information is the result of research conducted by our team at the UCLA Emmett Institute. We drew our conclusions from a holistic review of the best publicly available evidence.  

Some landfills were straightforward to identify. The plumes detected in Hong Kong could be traced to a landfill clearly marked on public mapping sites, as well as on government sites. Once we obtained the name of the facility, we were able to find the potentially responsible operator using government sources, which specified exactly who was responsible for the construction and operation of the landfill. 

The top plume on our list is traced to a large landfill facility in Greater Buenos Aires that is marked on Google Maps as operated by CEAMSE. The site is also listed as the location of the North III Environmental Complex, which the CEAMSE website identifies as its biogas treatment plant that transforms biogas from the waste into clean energy.  

The process was similar for tracking the “Dishonorable Mention” plume detected in Silivri, Istanbul. Based on geodata and satellite imagery, we were able to confirm the potentially responsible operator as İSTAÇ, a subsidiary of Istanbul Metropolitan Municipality. The official webpage for İSTAÇ lists the names and descriptions of each of its facilities along with a map that contains GPS coordinates. The map provided for the Silivri-Seymen location matches the coordinates linked to the Carbon Mapper plume data. The webpage also details that the facility includes an energy production facility. As for the potentially responsible operator in Ivory Coast, Eco-Eburnie, a subsidiary of Mota-Engil group, provides waste services in North-Western Abidjan including the Abidjan landfill. 

In some instances, we used press reporting to help our determinations, such as the case of the plumes detected in İzmir, Türkiye. Geodata and satellite imagery show a large waste facility in the Harmandalı district without an operator listed. Due to resident complaints and court proceedings, many news outlets have written stories about the Harmandalı Solid Waste Facility and identified the operator as the Metropolitan Municipality of Izmir. That municipality has also issued press releases about how it plans to address problems at the facility.  

Something on the list doesn’t look right? Think we’ve got something wrong?  Do you know something about one of these landfills that suggests there’s an error in Carbon Mapper’s observation and calculation or our compilation and interpretation?  If so, please explain it to us here. 

Photo: Daniel Miksha via Unsplash