The Environmental Protection Agency has announced it will delay rules aimed at cutting methane emissions from landfills, a move that could unravel attempts to limit the potent greenhouse gas from leaking into the atmosphere from the nation's garbage dumps.

The rules, created during the Obama administration to help combat climate change, require landfills to measure and capture methane, a short-lived climate pollutant with significantly more heat-trapping power than carbon dioxide over a shorter timeframe. They would reduce methane emissions from landfills by 334,000 tons a year, starting in 2025, roughly the equivalent of 8.2 million metric tons of carbon dioxide a year.

"Landfills are the third-largest source of methane emissions, so they're really a big source of climate pollution," said Peter Zalzal, a lead attorney with the Environmental Defense Fund. "Our concern is that this is the first in a series of actions that will undermine these efforts and eventually do away with them altogether."

The rules were part of President Barack Obama's effort to cut greenhouse gas emissions under his sweeping Climate Action Plan. They require new, modified and existing landfills to capture about 30 percent more landfill gas emissions, including methane, than required under the previous standards, which were put in place in 1996.

Environmental groups and the EPA have argued that technology has advanced significantly, including improved gas collection systems, gas-trapping landfill covers and monitoring systems, as well as systems that allow landfill operators to more easily capture gas as an energy source. Waste, much of it organic, generates methane and carbon dioxide as it decomposes, contributing to climate change.

But in October of last year, the waste management industry petitioned the EPA to reconsider or stay some of the provisions in the new standards. The industry said its main concerns were over technical requirements for monitoring and reporting under the rule.

On May 5, EPA Administrator Scott Pruitt sent a letter to the industry petitioners, which included the nation's largest waste management companies—Waste Management and Republic Services—saying the agency would issue a 90-day stay and "expects" to conduct another rulemaking process.

That letter was not made public until Tuesday, just a week before the May 30 deadline for landfill operators to submit their methane-reduction plans to the agency.

"This is not something the public was aware of," Zalzal said. "The way in which it was accomplished was done in a way to shield this from public scrutiny."

Waste Management, the country's largest waste hauler and landfill operator, said it was pleased with the EPA's decision.

"We will continue to comply with the original regulations while working with the agency to remedy the rules," Kerry Kelly, senior director of federal affairs for the company, wrote in an emailed statement. Kelly argued that the new rules "created redundant and conflicting layers of regulations on landfills with no apparent benefit to the environment."