Scientists from John Hopkins University have discovered two large underground "lakes" of high-quality methane beneath former Washington garbage dumps, according to the National Park Service.

Federal officials hope to tap the methane, also known as swamp gas, to heat government buildings and to fire a distillery that would produce another fuel -- alcohol -- to power lawn mowers and other small engines used in the 50,000 acres of federal parkland around Washington.

The methane is being produced by the huge mounds of decomposing garbage and trash now buried under several feet of earth at the former Kenilworth dump along the Anacostia River in Northeast Washington, and at Oxon Cove on the Washington-Prince George's County line.

Kenilworth, an open-burning dump that for decades was the worst source of air pollution in Washington, was converted to a santiary landfill in 1968 after a 7-year-old boy was burned to death in one of the windswept fires that frequently raced across the dump. It was finally closed in 1970.

Most city refuse was sent to Oxon Cove until 1972, when Washington began trucking trash to the huge Lorton prison complex in Fairfax County.

The National Park Service has since turned Kenilworth into a community recreation area and plans to build a golf course over the gently rolling hills of trash at Oxon Cove.

As part of its $60,000 methane study for the park service, the Johns Hopkins scientists, who are with the university's Applied Physics Lab, will begin additional exploratory drilling at the dumps within the next few weeks to determine the exact size of the methane "lakes."

"But based on the holes they've already dug, there should be plenty of gas to heat the greehouses" and other federal buildings near the Kenilworth Aquatic Gardens and to operate an alcohol still at Oxon Cove, said James Wolfe, local park service chief of maintenance.

The park service now spends about $40,000 a year to heat the greenhouses with natural gas, and uses nearly 500,000 gallons of gasoline a year just to operate some 350 lawnmowers in parks.

Parks service officials are so optimistic about their swamp gas discovery that already they are visiting nearby alcohol stills and training employes to modify lawnmower engines.

"We plan to put all our maintenance people on alcohol next spring," says Wolfe, buying alcohol at first and making their own by the spring of 1981. The alcohol will be manufactured from the corn grown at the three park service "living history" farms in Oxon Hill, Turkey Run and National Colonial Farm. A bushel of corn produces about 2 1/2 gallons of alcohol.

Both the methane gas and the corn would be free. The government's only costs would a pipe system to harness the gas and building a still at Oxon Cove, which would be run by present park service employes at the Oxon Hill Children's Farm.

Wolfe predicts that producing methane and alcohol not only will conserve energy and save money for the park service, but also will be a safety measure. The methane that now rises slowly through the soil at the dumps is explosive and occasionally seeps underground into nearby buildings when the ground is frozen, Wolfe said.

"We found gas in the pump room of a recreation center next to Kenilworth, and when some kids built an outdoor fire there recently they couldn't put it out," he said.

Because President Carter last spring reduced gasoline supplies for the park service and other federal agencies to 90 percent of their 1978 allowances, Wolfe said the park service has been looking for new ways to save gasoline. The park service already has bought 60 electric trucks, buses and cars for use in Washington area parks, making its fleet of electric vehicles the second largest in the nation (next to that of the U.S. Postal Service). The park service also is converting two dozen U.S. Park Police vehicles to run on propane and is proposing to buy as many as 10 alcohol-burning police cars.

Wolfe and park service agronomist Robert Cook last week visited the A. Smith Bowman distillery in Reston, where Virginia Gentleman bourbon is produced, and Maryland's St. Mary's County, which has applied for a $50,000 federal grant to distill alcohol from the county's surplus corn corp. St. Mary's plans to sell the protein-rich residue to local cattle farmers and use the alcohol to heat its three-story county office building and run the county fleet of about 35 buses, trucks and cars.

The Bowman distillery makes its bourbon from corn rye and barley, but it plans to modify its plant to produce about 2,200 gallons of alcohol daily from corn. The firm hopes to begin selling the alcohol as a fuel by next March, according to distillery vice president John Adams. It will make Bowman the first liquor distiller in the country to produce alcohol fuel. m

It can be mixed with gasoline and produce 22,000 gallons of gasohol, Adams said, or mixed with water and used in modified gasoline engines.

Gasohol -- 90 percent gas and 10 percent alcohol -- can be used in automobiles without any engine modifications. It already is being sold at a few Washington area gas stations and is commonly available in many midwestern states. The alcohol to be used in park service lawnmowers will be 180 proof (90 percent alcohol), with the remaining 10 percent (plain tap water," said Wolfe.

"We tried all kinds of ratios, from 200 proof down to 160 proof, which didn't work very well," Wolfe said. On Monday the park service began an alcohol lawnmower training program for memebers of its maintenance staff at Prince William Forest Park.

Using methane to heat buildings and run motors is not new in Washington. It has been done since 1938 at the Blue Plains Sewage Treatment Plant near Oxon Cove, where the methane produced from heating sewage has been used to fire furnaces and heat all buildings at the huge complex, according to Jean B. Levesque, District of Columbia water resources plant administrator.

The Blue Plains methane also is used to operate two 500-horsepower water pumps that pump 100 million gallons of water daily, Lveseque said. Usually, methane must be liquified like propane to be used in such engines, but Levesque said once the motors are started with diesel fuel "they then run beautifully on methane. It has been saving us $150,000 a year in fuel costs just for two motors alone."