FOR AN INGENIOUS way to advance several interests at once, consider some Maryland officials' plan for using Baltimore County trash to help revive the state's anemic coal industry. The idea was prompted by the Baltimore Gas and Electric Company's desire to convert a power plant in Eastern Baltimore County from oil back to coal. What makes this controversial is the utility's request for state permission to burn high-sulfur coal - because it is cheaper than low-sulfur coal, by perhaps $5 million per year, and because it is the type that those two 200-megawatt boilers were originally designed to use.

Baltimore County Executive Donald P. Hutchinson has objected, however, because of the added pollution that high-sulfur coal would cause. Although the converted plant would apparently not violate federal or state air-quality standards, Mr. Hutchinson fears that it would increase pollution levels enough to preclude most other industrial development in the area.

That's where the trash comes in. Trash, turned into pellets and mixed with coal, can be burned effectively as boiler fuel. The Maryland Environmental Service has been experimenting with refuse-derived fuel - and officials there have now suggested reducing the pollution problems at the BG&E plant by combining high-sulfur coal with Baltimore County trash.

That could have benefits all around. BG&E customers could pay less for fuel; the area could get less pollution; the country would not have to build a multimillion-dollar trash-disposal facility. And, yes, Western Maryland mines might get a new, long-term customer - but that is the most problematic aspect of the plan. BG&E officials are not yet certain that the Maryland mines, many of which are small, could supply enough of the right kind of coal at a competitive price. It would be splendid if things worked out that neatly. But if they don't, the utility should not be forced or cajoled into a "buy Maryland" plan. Besides being uneconomic, such a move could spur other coal-producing states to erect equally obnoxious barriers to Maryland coal - or for that matter, Maryland trash.