Localities here and across the nation are saving thousands of dollars on their utility bills by joining in partnerships with private firms to harness methane from sanitary landfills that otherwise would go unused.

Many scientists and public officials have urged that methane, a gas often mixed with other substances, be collected, filtered and transported for use in heating and lighting nearby facilities because sanitary waste is an abundant resource. About half the matter in landfills decomposes into methane.

They also agree that harnessing methane is safer than allowing it to seep into nearby land, where it can sometimes cause explosions like the two blasts last month at the Lorton Reformatory in Fairfax County. One man was killed and another seriously burned in those explosions. The experts cite the trouble-free safety record of the Kenilworth Aquatic Gardens methane recovery project in the District of Columbia, which has saved taxpayers thousands of dollars since its completion in 1981.

Prince George's County is planning to capitalize on the use of methane in one of the region's most complex designs for a recovery project. The Brown Station Road Landfill in Upper Marlboro is scheduled to be used beginning in June 1986 to provide heat, hot water and electricity for a 256,000-square-foot detention and rehabilitation center for drunk drivers under construction 10,000 feet from the landfill. The system also will supply utilities for several county office buildings about three miles from the landfill.

The landfill is expected to generate 11 billion cubic feet of methane over 20 years, the equivalent of 46 million gallons of gasoline or enough oil to heat 93,000 homes for a year, according to Michael Kelly, engineer for CE Maguire, a Rhode Island firm designing the conversion system. Kelly said the county should save $10 million over 10 years by harnessing the methane.

Full decomposition of sanitary landfill matter into methane takes from two to 30 years, experts say.

"Making pure methane is a costly operation," said Don Walters, director of energy for municipal waste at the U.S. Department of Energy. "But with that endless supply of garbage, you can burn and burn."

The initial stage of methane recovery at the Prince George's project will require installing 43 wells on 110 acres, Kelly said. After the methane is drawn from 60-foot wells, it will be piped to two boilers near the detention center where it will be burned after water and hydrogen are removed. Because the waste sites are near the burners, the methane does not have to be compressed, thus saving a substantial amount of money compared with commercial projects.

The $6.1 million project, one of the largest on the East Coast, will use more than 300 acres of sanitary waste by the end of the century, according to a feasibility study conducted by the Johns Hopkins University Applied Physics Laboratory.

Methane not used for heat will be burned by two generators to make electricity. The excess heat and electricity then will be sent about a mile away to the county administration building, the county courthouse and the Board of Education building, Kelly said.

Maryland Environmental Service, a private firm with 10 percent public funding, is financing the system. The Prince George's County Council is expected to give the firm authorization to sell county-backed bonds to local lending institutions to raise the money, according to Council Chairman William B. Amonett.

Amonett said he and other council members toured several methane recovery sites last year. "We liked what we saw," he said. "The idea of using byproducts for energy is great and well overdue."

One big bonus for the county is a contract to sell excess electricity from the conversion system to Potomac Electric Power Co. (Pepco). Kelly estimated that the county could reap as much as $650,000 annually for the next 10 years.

Ten years ago, the first methane recovery project was activated in Palos Verdes, Calif. Today more than 30 methane systems, about half of them in California, are in operation, and as many are in final planning stages, according to the 1984 Resource Recovery Yearbook.

The oldest methane recovery project in the region, at the Kenilworth Aquatic Gardens, harnesses methane from 35 acres of a now-defunct landfill about a mile away to heat four of the seven greenhouses.

James Wolfe, regional chief of maintenance for the National Park Service, said the system, when completed in 1981, funneled heat from methane into three greenhouses used to grow plants eventually sent to the White House. "But that only lasted a year because the White House didn't want to take any chances," Wolfe said. "You know, because it was 'different' they were wary of its use."

In the past three years the system has saved taxpayers about $30,000, Wolfe said.

Kenneth Shuster, chief of the land disposal branch of the Environmental Protection Agency, said collecting and burning methane in controlled environments may be safer than allowing the methane to escape into the atmosphere, a problem that has cropped up in several communities in recent years.

"When methane constitutes more than 15 percent of the elements in the air, it becomes particularly volatile," he said.

Walters said one of methane's characteristics is that it seeps through the "path of least resistance. If it happens to seep into a neighboring residential basement and comes in contact with the furnace, the whole house could blow."

Last March a house in Akron, Ohio, exploded after gas seeped into it from a nearby landfill. And in 1976, methane escaping from a Richmond landfill forced 1,000 families to evacuate their homes and two schools to close for several days.

The conversion of methane also may reduce noxious fumes that surround landfills when garbage decomposes and sulfur oxides are released. In Montgomery County, the Gude Landfill was closed by the state health department in 1982 after it filled to capacity and residents complained of foul odors.

Today a Los Angeles energy firm, Pacific Lighting Energy Systems, leases the landfill from the county and plans to use the methane to produce electricity that will be sold to Pepco by the end of 1985.

Project manager James Kennelly said Pacific Lighting has agreed to pay up to 19 percent of its gross revenues to the county over 25 years.

Electricity harnessed from Gude will constitute less than 1 percent of Pepco's capacity, said Pepco spokeswoman Nancy Moses.

"It's really not going to make much of a dent," she said. "But they're scratching the surface of what is becoming a significant energy conversion method."

Howard County, also seeking to fatten its coffers, is negotiating with a Pennsylvania energy firm to lease its 85-acre New Cut Road Landfill, which was closed in 1980, according to Steve Hudgins, chief of the Department of Environmental Services.

If Obrien Energy Products of Downingtown, Pa., leases the landfill, it would convert methane from the landfill for electricity to sell to Baltimore Gas & Electric Co., according to Jonathan Hall, an engineer for the utility.