Maryland has significantly underestimated the amount of potent greenhouse gases leaking from its landfills and should take immediate steps to remedy the problem, an environmental group said Wednesday.

About 51,500 tons of methane escaped from the state’s landfills in 2017, or more than four times the amount reported by the Maryland Department of the Environment and more than any other source of methane pollution in the state, according to a report issued Wednesday by the Environmental Integrity Project. The report says the state also underestimated the amount of carbon dioxide released into the atmosphere from its municipal waste landfills.

The MDE confirmed the report’s findings and updated its website with revised data that set methane emission estimates even higher, at 58,000 tons. The agency said the environmental group’s report also prompted revisions going back to 2006 in its emissions data, known as inventories.

“We agree with the group’s findings,” Ben Grumbles, Maryland’s secretary of the environment, said in a statement. “The revised estimates reinforce the need for new actions to control methane emissions from landfills and also boost efforts to reduce the amount of waste going to landfills, which is exactly what we are doing.”

A simple mathematical error, among other lapses, led MDE to estimate that only 12,500 tons of methane had leaked from the landfills, said Ryan Maher, an attorney with the Environmental Integrity Project and the report’s lead author. He said state environmental officials appeared to have inverted a fraction when calculating the rate at which methane breaks down at the landfill’s surface, a process known “surface oxidation.”

Instead of reducing the amount of methane emissions by 90 percent, surface oxidation only cuts them by about 10 percent. Other errors included excluding five landfills and counting the emissions of a nonexistent landfill when estimating the total emissions, Maher said. He said his report examined the MDE’s data only, without challenging its theoretical models. But assumptions built into the models could also use another look, he said.

The new findings suggest that methane emissions from Maryland’s more than 40 landfills account for about 37 percent of the state’s methane emissions, not 13 percent as the state estimated previously. Prince George’s County’s Brown Station Road Landfill emitted the most greenhouse gases, followed by Washington County’s Forty West Landfill, the report found. Third highest was Baltimore’s Quarantine Road Landfill.

But the report also says that the state could alleviate the problem and perhaps have an impact on carbon accumulation in the atmosphere by better monitoring and regulating landfill emissions. Only 21 of the state’s landfills have systems in place to collect or control methane emissions, and only four are required to comply with government standards to ensure that they work, the report says.

“Climate change is already upon us,” Maher said in an interview Tuesday. “If we attack methane, we can really actually achieve important carbon reductions in the atmosphere, in part because of methane’s potency.”

Methane is produced in landfills when organic waste inside decomposes, including food scraps, grass clippings and paper products. Though the molecule remains in the atmosphere for a shorter time than carbon dioxide, methane causes more intense warming. Over 20 years, a single ton of methane has the equivalent impact on atmospheric warming as 86 tons of carbon dioxide, Maher said.

The Environmental Integrity Project called on the state to tighten regulations on monitoring and reducing greenhouse gas emissions from landfills, and urged Maryland to go even further than the federal Environmental Protection Agency. The group also said the state needs to divert more organic waste from landfills and establish financial incentives to create new composting facilities to reduce methane emissions.

MDE spokesman Jay Apperson said that the agency has adopted stricter rules on methane emissions from landfills since 2017 and that a new push is underway to adopt stricter regulations along the lines of those in California and Oregon. He said MDE is also setting up an office to explore new and expanded use of recyclables and finding markets for them, and it’s working on implementing a new law that requires certain supermarkets, convenience stores and government or school cafeterias to keep food scraps out of the garbage.