A trigger. An empty Chick-fil-A sandwich bag. A mattress. Sneakers, navy blue, white soles. A small orange bouncy ball.

Garbage is scattered in the thigh-high dirt and is used to bury dirty, well-tested items at the Orange County Landfill in Florida, and to prevent the invasion of insects, rats, and pigs. Bulldozers level the soil into place, while tractor trailers transport more garbage. Vultures and seagulls hover above. A bald eagle landed nearby.

"Anything you see in the real world will be seen here," said David Gregory, manager of the solid waste department of the Orange County Public Utilities Department. "Because it comes when people throw things away. "

According to the Environmental Protection Agency, landfills like Orlando Edge are one of the largest sources of methane in the United States. Methane is a greenhouse gas that is more effective than carbon dioxide and a major contributor to global warming. A groundbreaking report published by the United Nations in May found that immediately reducing methane emissions is the planet’s best and fastest opportunity to mitigate climate change. When organic waste such as food residues, wood and paper are decomposed, landfills emit methane.

But the challenge of controlling methane is huge. The first step is to quantify how many leaves are buried. Industry operators insist that the EPA has overestimated emissions. However, an independent study of California landfill emissions and a top methane expert from the EPA stated that the agency severely underestimated methane from landfills.

Susan Thorneloe, EPA's senior chemical engineer, has been working on the agency's methane estimation method since the 1980s. He said that the EPA has been "underestimating methane emissions from landfills by a factor of two."

Thorneloe said that part of the problem may be that EPA's method of estimating methane emissions from landfills is outdated and flawed.

Ryan Maher, an attorney for the regulatory agency's Environmental Integrity Project, said that methane emissions from landfills are "an overlooked issue."

"Our emission estimates are based on models rather than direct measurements," said Maher, who recently wrote a study that found that Maryland’s landfill methane emissions are four times the state’s estimate. "We do have the ability to directly measure these emissions. But we have not yet."

The risk of obtaining accurate methane emissions is high. Reducing methane can curb climate change almost immediately, because it stays in the atmosphere for a short time, while carbon dioxide stays in the atmosphere for a century or more. Landfills are one of the three main sources of human methane pollution, in addition to livestock and the oil and gas industry. The United States is the third largest methane emitter in the world.

The Biden government has begun to implement the 2016 regulations on methane from landfills, but it will only reduce emissions by a small amount. However, according to United Nations assessments, by the 2040s, a significant reduction in global methane emissions will avoid additional warming of nearly 0.3 degrees Celsius. Compared with the pre-industrial period, this may help prevent the global average temperature from rising more than 1.5 degrees Celsius and avoid the worst effects of climate change, which is the goal of the Paris climate agreement.

"By reducing methane emissions, we can quickly reduce the effect of atmospheric warming," said Jeff Chanton, a climate scientist who studies methane at Florida State University. "Targeting a landfill is a good starting point, because by adjusting the gas collection system and making it work at an optimal level, you will get a lot. You collect more methane and don’t release it into the atmosphere. middle."

Standing on top of the 140-foot-tall trash at the Orange County Landfill, you can almost see the entire contents of the Orlando Metro: the high-rise buildings in the downtown area, the control tower and runway of the Orlando International Airport, and the looming Stanton Energy Cylinder Type cooling tower center. It powers approximately 260,000 homes and businesses in Orange County and Osceola County, and up to 15,000 of them use methane from the landfill.

Gregory found value in what happened under his feet, the decay and decomposition of organic waste (such as kitchen waste, paper, or spoiled canned food), and the biological process of converting trash into methane. Buried in the trash is a crisscross network of more than 500 wells that collect methane gas from the decomposed trash. These wells can also prevent large amounts of methane from escaping.

"Some things have reached the end of their lives," he said of trash. "One of the things we do at landfill sites is to collect these gases and use them to create energy."

EPA has tracked more than 2,600 municipal solid waste landfills. Approximately 500 collected methane for energy production. The agency estimates that there are nearly 500 more that can cost-effectively convert methane into energy.

Projects such as these can play a key role in containing the worst effects of climate change.

Despite the efforts of landfill operators nationwide, a large amount of this invisible and odorless gas still escapes from landfills every year. For example, for all emissions captured by the Orange County landfill, the facility released 32,000 metric tons of methane into the air in 2019, making it the third largest source of methane emissions from landfills in the country. According to statistics, the company reported to EPA The latest public information reported. According to data from the U.S. Environmental Protection Agency, this is a huge and inexplicable increase compared to previous years. In the ten years before 2019, Orange County was not the top 10 emitter.

The Orange County site is not alone in central Florida. According to the U.S. Environmental Protection Agency, three of the top 10 methane emitters in the United States are located near Orlando. Their collective emissions cause as much damage to the climate in the short term as the 1.8 million cars and pickup trucks registered in the three counties where landfill sites are located.

Officials said that for Orange County, the top ranking was an accident — groundless. Community leaders here are proud of sustainable development initiatives. They believe that the methane energy system of the landfill is the key to reducing greenhouse gas emissions.

Gregory of Orange County said he is reassessing what the county reports to the Environmental Protection Agency.

"It's not like we have to measure" methane emissions, he said. "It's all based on models. This is where we need to make sure we don't overlook anything."

A spokesperson for the largest methane-emitting landfill in the United States also said that the US Environmental Protection Agency’s ranking is misleading. The landfill is located near Cincinnati and is operated by Rumpke Waste & Recycling.

In an email, spokeswoman Amanda Pratt dismissed the emission value reported by her company, which was calculated based on "using the data provided by the facility and the equation derived by the U.S. Environmental Protection Agency Theoretical methane generation rate".

The EPA's data may indeed be flawed.

Due to uncertainty and insufficient measurement, a 2018 report by the National Academy of Sciences of the United States of America had "low confidence" in the EPA's estimate of methane emissions from landfills. The report concluded that the agency’s method of estimating methane emissions from landfills is “outdated” and “never verified on-site”.

In addition, the EPA allows personal landfill operators to calculate the amount of methane they produce in three different ways, and two different ways to calculate the amount of methane emitted into the atmosphere. Depending on the method chosen by the operator, the estimated methane emissions may vary widely.

Thorneloe of the EPA helped develop the current estimation method, which she said was “developed more than 30 years ago using empirical data from about 40 landfills.”

Citing new research from California, she began to believe that the agency underestimated emissions.

The landfill operator agrees that the EPA model has shortcomings, but insists that these shortcomings will lead to overestimation of emissions from their site. David Bidman, CEO of the North American Solid Waste Association industry organization, said in a statement to NPR: "The model relies on many assumptions and has not been updated to reflect changes in the waste sector, such as reducing organic content. It may lead to high The waste stream that estimates the amount of landfill emissions."

Professor Emeritus of the University of Illinois at Chicago and co-author of the National Academy of Sciences report made Bogner called the EPA's approach "a mess." Bogner blamed the shortcomings in part on methods first developed by the Intergovernmental Panel on Climate Change, a United Nations agency.

"Methods should evolve with the development of science," Bogner said. "As we adopt more intensive climate change mitigation strategies to more accurately understand how much methane is released from specific landfills, this becomes more and more important. In the past, you might wave your hand and say,'This could be a Approximate numbers, but we now need better numbers to guide mitigation strategies in specific locations."

An EPA spokesperson said in an email that the National Academy of Sciences report made recommendations for improving methane measurement, and the EPA is working to resolve issues related to the agency.

More broadly, EPA officials stated that they will continue to update estimates. The spokesperson added that the agency is reviewing scientific research on landfill waste to better inform the agency’s methane emissions estimates.

Thorneloe said that better measurement techniques will help EPA staff make better estimates.

"If we are to choose specific sources to reduce emissions, we need to know what those emissions are," Thorneloe said. "What I'm trying to do is develop better testing methods, not the methods we relied on in the past."

Industry representative Biderman said, “Any proposed regulatory changes should be technically feasible and commercially available.”

Capturing methane in a landfill is complicated. According to Chanton, a climate scientist at Florida State University, there may be many problems with the landfill pipes. "It is easily disturbed," he said. "This requires a lot of attention."

Landfills are not like factories. Almost all emissions are discharged through a single chimney. Landfills can span hundreds of acres and leak at different rates from open areas or parts that are temporarily covered or permanently closed and covered.

Operators have up to five years to start capturing methane from the new part of the landfill (called cells). But Morton Barlaz, professor and chair of the Department of Civil, Architectural, and Environmental Engineering at North Carolina State University, said that methane pollution started much earlier.

The ability to collect methane in a landfill usually depends on the operating efficiency of the gas collection well and collection system. Landfill operators must cover the waste treatment area with a thin layer of soil or alternatives (such as mulch or even plastic) every night. Barlaz said some of these materials are more porous than others, leading to more methane emissions.

Weather can also play a role. Rainwater helps produce more methane and flood gas collection systems, thereby reducing their efficiency.

"When you encounter a situation where gas collection is blocked, the landfill will emit more methane than the EPA estimated," Chanton said. But he added that a well-functioning system can collect more methane in its wells, and it can also use the methane-digesting microorganisms in the landfill soil cover to help neutralize greenhouse gases.

One hope for better control of methane emissions involves NASA and monitoring landfills from airplanes or space.

Riley Duren is a former engineer at the California Space Agency's Jet Propulsion Laboratory and is now a research scientist at the University of Arizona. He is also the CEO of Carbon Mapper, a new non-profit organization. Carbon Mapper announced in April that it is launching "a constellation of methane sensing satellites" with partners including NASA, California, and various universities and organizations.

This is an extension of the California study praised by Thorneloe, which involved hundreds of California methane emitters between 2016 and 2018, such as oil and gas operators, animal manure facilities, and landfills. The study, published in the journal Nature in 2019, identified the small but numerous methane “super emitters” described by lead author Durham. As many as 40% are landfills.

Du Lun said: “Some of these landfills emit a lot of methane,” which far exceeds the amount reported by landfills. "I'm talking about tons of methane per hour."

Durham said that many landfill operators take methane control seriously. But when the gas capture system is offline or workers are installing a new system, large-scale leaks can occur. “In other cases, this is the result of flawed management practices in the management of daily coverings at the landfill,” he said.

Duren said that these satellites can help landfill operators find problems quickly so they can solve them. This work is essential if the United States is to fulfill the Biden administration’s commitment to reduce US greenhouse gas emissions by 50% by 2030.

Focusing on super launchers may be an effective step. Du Lun said: "The amount of infrastructure is small... If we can target, it may be significantly reduced in the next few years."

In May, EPA implemented the 2016 Obama-era rules to extend the existing methane collection system requirements to 93 additional landfills. It lowers the emission threshold of the gas collection system that must be installed in the landfill. Once implemented, the rule will reduce methane emissions from landfills nationwide by approximately 7%.

The regulatory agency also informed about 1,600 landfills in about 40 states that they lack an EPA-approved landfill gas capture plan and they need to develop one, otherwise the agency will enforce its own plan.

Biederman of the North American Solid Waste Association said that the EPA’s actions “should further reduce emissions and continue the trend that the industry has been investing in for decades.”

For many scientists and advocates, EPA's actions are far from the level required by the climate-and the level that existing technologies can achieve. Maher of the Environmental Integrity Project stated that the agency's plan has little impact on landfills that already require the collection of methane under the old rules, and the EPA should further lower the threshold for requiring collection systems to enable smaller landfills to reduce methane.

For example, in Maryland, state officials are enacting landfill methane regulations. However, if EPA rules are passed in Maryland, they will “only apply to four of the state’s 40 gas-producing landfills,” Maher said.

The recent United Nations methane assessment went one step further. It called for an end to the practice of sending organic waste such as food scraps to landfills. Such waste should enter composting facilities or specially designed digesters to better reduce or capture methane emissions.

For their part, some landfill operators are scrambling to explain why the EPA ranking is wrong and explain what measures they are taking to reduce emissions.

At the Rumpke landfill near Cincinnati, company spokesperson Molly Yeager explained its highest EPA ranking, noting that the company also used a second alternative emission model and obtained lower emission estimates through some direct measurements. . She said that by default, the EPA chose a higher number. An EPA spokesperson agreed that the reporting system uses the higher of the two equations by default, but she added that if landfill operators think that the result of the other equation is more representative of landfill conditions, they can choose the other The result of the equation.

Central Florida is one of the fastest growing regions in the United States. Thomas Mulligan, assistant director of the Brevard County Solid Waste Management Department, said that in Brevard County on the east coast of the state, keeping up with the ever-increasing population and volume of waste poses a challenge to control methane emissions.

"I know very well that we have been in the top 10 for a while," said Mulligan, who oversees the Brevard landfill 45 miles east of Orlando. "It's really tough."

Like other industry representatives, he said that he believes the EPA's reporting method overestimates emissions. But he also said that Brevard County can take more measures to reduce landfill emissions. For example, the county can speed up the installation of gas collection systems in landfill expansions, he said.

"This is a matter of capital improvement funds, and it is also a matter of time," he said.

The JED Landfill is located outside St. Cloud, about 54 miles south of Orlando, in the idyllic landscape. It is part of the National Landfill Group owned by a Texas company Waste Connection Corporation. JED officials declined an interview request, but Kurt Shaner, vice president of engineering and sustainability, stated in an email that the company has been tightening the landfill coverage system and expanding Gas collection area.

In Orange County, Gregory said he is recalculating landfill emissions and plans to use the agency's alternatives to submit an updated report to the EPA.

"We consider our powerful system," he said, "and the amount of coverage and the fact that we have closed many of these landfills...the numbers will drop sharply."

This story is a collaboration between Internal Climate News, the NPR member station WMFE in Orlando, Florida, and the NPR Survey Station.

Carbon dioxide is not the only greenhouse gas that warms the planet. In fact, methane is much more effective. The United States is the third largest methane emitter in the world. One of the largest sources of methane is landfills, but as reported by Amy Green of WMFE in Orlando, reducing these emissions will be a challenge.

AMY GREEN, BYLINE: I am at the top of a 140-foot mountain in the county landfill. From here, I can almost see the whole picture of Orlando-the high-rise buildings in the city center, the towers of the airport and the runway. Under my feet is rubbish-a flip-flop, an empty Chick-fil-A sandwich bag, a mattress, which looks like a small bouncy ball, a Gatorade bottle.

The bulldozer smoothed the top layer of dirt, while the tractor trailer transported more garbage. Vultures and seagulls hover above.

David Gregory: Anything you will see, if you want, in the real world, you will see it here, because this is people-when they throw things away, that's everything.

Green: That's David Gregory from the Orange County Public Utilities Department. Eventually, waste, such as kitchen waste and yard waste, will rot and decompose, producing landfill gas, which consists of most of the methane. The Environmental Protection Agency lists this landfill and two other landfills in central Florida as the country’s largest sources of methane from landfills. In short, their emissions are as damaging to the climate in the short term as nearly 2 million cars and pickup trucks registered in the same county. But Gregory said he thinks this number is too high, at least the number from Orange County is too high.

Gregory: Landfill-we don't have a tube to measure what comes out of the tube, right? You know, we have hundreds of acres of land here. So we rely on the EPA model and the EPA model.

Green: He is not the only one who thinks these models may be wrong. Measuring methane emissions from landfills is complicated.

JEAN BOGNER: Really, a bit messy.

Green: Jean Bogner of the University of Illinois at Chicago said that the US Environmental Protection Agency's method of estimating emissions is outdated.

BOGNER: In the past, you might wave your hand and say that this might be a rough number, but we now need better numbers to guide site-specific mitigation strategies.

Green: She blamed part of the problem on the method first developed by the United Nations. EPA allows multiple methods to calculate methane emissions from landfills, and these numbers can vary widely. For decades, Susan Thorneloe worked with the EPA to help develop these methods. She agrees that these numbers do not always add up to what is actually happening on the ground.

SUSAN THORNELOE: We recognize that it may be orders of magnitude different from those found in landfills, whether it is an overestimation or an underestimation of emissions.

GREEN: She said that recent data shows that EPA data can underestimate methane emissions from landfills by a factor of two. An EPA spokesperson said the agency will continue to update these numbers as better data becomes available.

In Orange County, one way landfill operators control methane emissions is to capture them and convert them into energy. Brian Moore of the Orlando Public Utilities Commission points to a pipe leading from the county landfill, which is buried in a huge crisscross network of more than 500 wells.

BRIAN MOORE: The pipes that extend from the ground here are where we use these blowers to vacuum up the mountains and suck out gas and methane.

Green: The wells collect the emissions and direct them to the facility, where they are processed before being sent to as many as 15,000 homes and businesses. The Biden administration wants more landfills to do this, but it can also be fraught with problems. Pipes and wells may malfunction, and rainwater may flood them, reducing their efficiency. Jeff Shanton, a climate scientist at Florida State University, said that targeting methane can have a rapid impact on climate change. That's because methane does not stay in the atmosphere as long as carbon dioxide.

JEFF CHANTON: The life span of methane is about 10% of carbon dioxide. Therefore, by reducing methane emissions, we can quickly reduce the atmospheric warming effect caused by greenhouse gases. So methane is the easiest place, and the target landfill is a good starting point.

Green: The risk of solving all these problems is high. A United Nations report in May found that immediately reducing methane emissions is the planet’s best opportunity to slow climate change as quickly as possible. For NPR News, my name is Amy Green from Orlando.

CHANG: This story was produced in collaboration with Inside Climate News. Transcript provided by NPR, copyright of NPR.