The Army has refused to let Fairfax County consider using 300 acres at Fort Belvoir for a massive resource recovery operation that would turn the region's trash and sewage sludge into revenue-producing compost and steam energy.

Alan J. Gibbs, assistant Army secretary for installations, logistics and financial management, said the Army, after reviewing Fairfax's request, has concluded that the land "will not be excess to (its) needs. . ." Gibbs said the acreage is part of the only area at Belvoir that can be used for engineer combat training.

Given the decision, Fairfax probably will drop its efforts to have belvoir made available as a possible site for resource recovery. County Board of Supervisors Chairman John F. Herrity (R) said. "We'll have to go back to the drawing board," he said.

One possibility, according to Gov. John N. Dalton's adviser on environmental affairs, Fairfax nuclear engineer Noman N. Cole, Jr., is the District of Columbia's sprawling Lorton corrections facility west of Belvoir where trash and sewage sludge could be shipped by rail.

Under Fairfax's plan, which would have had to go through a lengthy local, state and even congressional approval process, thousands of tons of the region's trash and sludged would be barged daily to the Belvoir site on Pohick Bay. There it would be composted to produce a salable soil conditioner or incinerated to make steam that could be converted into electricity and sold.

A drive against the facility was being organized by an environmentalist who claimed it would wreck the area's ecology.