Denver and WM, one of the nation’s largest waste companies, will soon turn the city landfill into Colorado’s first garbage dump that converts methane into renewable natural gas — repurposing a greenhouse gas that contributes to global warming and harms human health.
The project was announced last week as Colorado’s air quality regulators are set to create new regulations aimed at reducing the amount of methane oozing from the state’s 51 landfills. Colorado’s landfills release millions of metric tons of greenhouse gases each year, and the state wants to reduce those emissions as part of its multipronged approach to eliminate 90% of the state’s greenhouse gas emissions by 2050.
The methane is created as organic matter like food, yard debris and paper decomposes.
“The catchphrase of methane is (that) it’s more potent as a greenhouse gas than carbon dioxide or other pollutants,” said Stefanie Shoup, the deputy director for regulatory affairs at the state’s Air Pollution Control Division. “From a climate action perspective, addressing methane is the fastest thing we can do to affect climate change right now.”
The Colorado Air Quality Control Commission, which establishes regulations to control air pollution, will consider the new methane emissions rules for landfills at its next multiday meeting, which starts on Dec. 17.
While Denver city officials and WM made the decision to build a renewable natural gas plant at the Denver Arapahoe Disposal Site outside of the state’s new regulations, it is an example of how landfill operators and state regulators are working to reduce landfills’ impacts on the climate.
The renewable natural gas facility will capture and refine almost all of the methane released at Denver’s only landfill, which is also the largest in the state. That process will produce gas that is nearly chemically identical to the natural gas that comes from fossil fuels. The gas conversion will reduce the landfill’s carbon footprint.
WM — formerly known as Waste Management — will finance construction of the facility at the landfill, which is located at 3500 South Gun Club Road in Arapahoe County, and Denver will earn royalties from WM’s sales of natural gas, said Zach Clayton, the environmental land use and planning manager at the Denver Department of Public Health and Environment.
The facility should begin operating by the end of 2027.
“It’s not only an environmental benefit,” Clayton said, “but it’s a monetary benefit for us to capture this as a commodity and sell it, in lieu of it going into the environment.”
Brian Snyder, the director of renewable energy operations for WM Renewable Energy, a subsidiary of WM, says the company will use a collection system to pull gases from the landfill. Then it will send those gases through a process that will separate methane from carbon dioxide and other impurities. Once the methane becomes natural gas, the facility will feed it into a pipeline to be sold on the energy market.
That natural gas could be used to heat homes or to fuel large trucks, Snyder said.
“We can collect our trash — and then refuel that truck with the gas that’s collected off that trash,” he said.
Renewable natural gas plants are being deployed across the country as people try to slow climate change. There are 536 such plants across North America, and WM plans to build 20 new facilities through 2026, Snider said. In Colorado, renewable facilities already are converting methane from dairy farms or wastewater into natural gas, Conway said.
WM will be involved in this month’s hearing over the new landfill methane rules, but company officials declined to talk about the proposed rules and referred questions to an industry association. Efforts to reach officials at the National Waste and Recycling Association were unsuccessful.
Potential compromise emerges
The Air Quality Control Commission considered new rules in August. But it tabled its work after landfill operators and environmentalists struggled to reach an agreement on how closely landfill operators should monitor those emissions and what expense they should be willing to pay to limit methane leaks.
At the time, the waste disposal industry opposed the new regulations. But Shoup said various stakeholders have met repeatedly over the last three months to hammer out a compromise that she believes the commission will approve.
“They still don’t love it,” Shoup said of industry support. “There’s still some disagreement.”
The proposed rules include more monitoring and reporting of emissions to determine exactly how much landfills release each year, which environmentalists believe will help regulators decide later whether the state needs more requirements.
“We all know we can’t control what we can’t measure,” said Ryan Call, the policy and campaigns manager at Eco-Cycle, a Boulder nonprofit group that promotes policies to achieve zero waste in the state’s garbage disposal system. “This rule will phase in requirements for landfills to measure their emissions, rather than estimating emissions based on the amount of waste they bring in.”
Colorado’s landfills released an estimated 1.45 million metric tons of greenhouse gases in 2020, according to the Colorado Department of Public Health and Environment. That was 1% of all the greenhouse gas emissions in the state, the department reported in late 2024.
But the amount of methane leaking from landfills could be much greater, environmentalists and regulators have said.
In June 2024, a NASA study that used satellite data estimated landfills in the U.S. were releasing 50% more methane than the EPA had reported, and a subset of high-emitting landfills were 77% higher, on median, than what was reported to the EPA.
Colorado regulators have discovered previously unknown methane leaks from landfills when conducting flights around the state to measure emissions from oil and gas wells, Shoup said.
Multiple states already have methane emissions rules in place, and the technology to detect it and control it is improving, said Katherine Blauvelt, the executive director of Full Circle Future, a nonprofit that focuses on reducing landfill emissions.
“Landfills overall are stuck in the 1970s and haven’t caught up to all the technology and available methods we have today,” she said. “That’s just a real recognition that it’s sitting on the shelf and it would be good to use it. A day without using that technology is a day lost without improving human health.”
Most landfills look for leaks by having employees walk through the piles of garbage to hunt for them. But the new rules would encourage operators to use drones and other aerial technology to detect leaks.
“The desire is to be able to use more remote technologies. That’s where the drones come in,” Shoup said. “It would help them to be able to identify those sources faster and fix them faster.”
Eliminating flares
The state’s largest landfills dispose of methane by using flares to burn off the pollutants seeping into the air. The proposed rules would require them to install enclosed combustion systems rather than resorting to the open flames burning into the sky, Shoup said.
Owners of smaller landfills would be pushed to start using flares, though the rules would not require all of them to do so.
State regulators have taken into account that small county-owned landfills in rural Colorado do not pollute as much as large landfills owned or managed by private companies, Shoup said. Those smaller landfills also do not have large budgets.
So the proposed regulations would give those smaller landfills an extra three years to comply, she said.
One possible measure that continues to be disputed by the industry is whether the state should require landfill owners to use biocovers to contain the methane underground. Those covers make use of compost or other organic waste to serve as filters over the landfill. But some companies argued they weren’t as effective in Colorado’s arid climate and would be a wasted expense.
So the state is proposing to put biocovers on three landfills that closed before 1996 and then study whether or not they reduced methane emissions, Shoup said.
“We will have a better idea for future landfills that shut down, and what they might need to do,” she said. “These are facilities that run for decades, but then the emissions don’t stop when they close.”
Projects such as the Denver plan to build a renewable natural gas facility at its landfill wouldn’t become a requirement under the proposed rules, but the state wants to make sure operators have the flexibility to build them, Shoup said.
The project will not eliminate methane or natural gas, which also releases pollutants when burned, Shoup said, but it will benefit the environment.
For now, WM collects about a third of the methane gas leaking from the landfill and sends it to an on-site generation plant. There, a combustion device converts it to energy that is sold on the grid. But those turbines release enough pollutants that the landfill needs a federal Title 5 air permit for the plant, Conway said.
The new renewable natural gas plant will eliminate those pollutants — and the company will no longer need a Title 5 air permit.
Conway, who has been working on the project for years, said it will keep methane from pouring into the air on the front end, and then the natural gas created from it will be used to power trucks, reducing emissions from traditional diesel-powered vehicles, which are dirtier to operate.
“You’re improving air quality because you’re not flaring, and you’re improving on the latter end of the cycle because you’re not burning diesel,” Conway said. “You’re fixing it in two places.”
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