You've heard of the oil lobby. Now meet the peat lobby.

Nowhere near the size of the oil lobby, the peat lobby may nonetheless be the fasting growing in Washington. Nonexistent a few years ago, the peat lobby's membership includes Alaska, Minnesota, Maine and North Carolina, as well as Ireland, Finland, Sweden and the Soviet Union. Not to mention the Gas Research Institute, the Institute of Gas Technology, the Midwest Research Institute. First Colony Farms and the Minneapolis Gas Co.

Peat. The decayed and carbonized remains of aquatic plants that somehow never decayed long enough to become coal. Compressed and dried, peat has been used as a kitchen fuel for 200 years in Ireland and now the high price of oil has brought it back to the attention of energy users around the world.

The peat lobby includes its leading users, such as Ireland, Finland and the Soviet Union. Both the Finns and the Soviets have sold peat-harvesting machines to the United States in hopes this country will adopt them and perhaps even improve them.

The Irish have been described on Capitol Hill as "active lobbyists" to free funds for spending on peat projects in the hope that the research will benefit them. The states of Minnesota and North Carolina are active. So are the Institute of Gas Technology and its sister organization, the Gas Research Institute, which hopes to get research funds to convert peat into synthetic natural gas.

The peat lobby sells its product in two ways. The first is by emphasizing it as an alternate to high-priced Arab oil.The other is to point to its cleanliness. They say only natural gas burns cleaner, and peat's combustion products are far and away cleaner than those of oil and coal.

The world's second richest (behind the Soviet Union) peat reserves are in the United States, where there is no less than 120 billion tons of peat in ground no deeper than six to 10 feet. That's the equivalent of 240 billion barrels of oil, a 30-year supply.

For this reason alone, the United States will soon join the ranks of the world's peat burners. Two big peat projects are under way, one in Minnesota, started by the Minneapolis Gas Co., the other in North Carolina, begun by the rural Electric Membership Corp.

The Minnesota project involves burning peat to make synthetic gas. The North Carolina scheme has as its goal an electricity plant that will generate 600,000 kilowatts of power from the burning of peat.

The Minneapolis gas project has a head start, having spent $1.5 million of Department of Energy funds to find out if peat will decompose rapidly enough to produce a useful synthetic gas. The North Carolina project is not as far along, but is a sure candidate to share the $4.5 million the Department of Energy has been appropriated for the coming fiscal year to develop U.S. peat reserves.

The principal barriers to expanded peat use are the difficulties of digging it up and drying it out.

In the ground, peat contains up to 80 percent water by weight. The Finns squeeze some of the water from peat by bulldozing it out, and then leaving it in the sun for three days to dry.

"No matter how hard you try you never get all the water out of peat," one Finnish energy expert said not long ago. "It's impossible to get dry peat."

Harvesting peat is just as difficult. First Colony Farms of North Carolina, which sits on 372,000 acres of peat in two remote counties of eastern Carolina, has just finished testing 17 peat-harvesting machines supplied by Finland and the Soviet Union and has concluded it must devise its own machines to do the job.

It's not that the Finnish and Soviet machines were bad, it's just that North Carolina peat is so filled with the trunks of ancient trees that the machines couldn't cut the peat loose. They worked fine in northern Europe, where the dead trees in the peat were small, but not in North Carolina, where they were three times as big.

If you listen to the peat lobby, these are only temporary drawbacks. Minnesota and North Carolina say that dewatering of peat is well on its way to solution, and Finland and the Soviet Union are on the verge of remodeling their machines to handle bigger logs. The Energy Department is thinking of financing the design of a new harvesting machine that will cut through Carolina peat.