WE OFFER three cheers for Montgomery County's decision to launch a mandatory newspaper recycling program, and one strong plea to the citizens of the county to give this smart and courageous undertaking their full support.

The county's new program was adopted to solve an immediate problem -- the near-saturation of its landfull site. But residents who participate can have the satisfaction of knowing that, in the few minutes per week it will take them to stack and bundle their old papers, they are also saving considerable energy, reducing air and water pollution and, along with 200 other enlightened communities, demonstrating to the rest of the nation that Americans are not indifferent to the country's problems and will change their houshold habits when offered reasonable opportunities to do so.

As a country, we produce about 140 million tons of municipal garbage each year and spend about $4 billion trying to get rid of it. In most cities garbage collection and disposal is the second-largest item in the city budget -- right behind the public schools. Most of the waste goes into open dumps, and it's getting harder and harder to find the 500 new dump sites that are needed each year. All methods of dispoasl -- incineration, dumping and landfill -- create environmental problems. Part of the answer lies in generating less waste: more sensible packaging and more products not planned for instant obsolescence would make a big difference. And part of the answer -- one that local communities can choose to do on their own -- is recycling.

About one-fifth of the country's newspapers is already being recycled. The only good way to collect it is through source separation programs (that is, directly from consumers) like Montgomery County's. This produces a high-quality waste and saves the energy that would otherwise be needed to separate the paper from other types of garbage after it has all been mixed together in the garbage truck. Every ton of newsprint made from this recycled waste uses about 25 percent less energy than a ton of newsprint made fresh: a substantial savings.

In the past, uncertainty about the availability of a market for recycled materials has held back many programs. Today, however, the situation looks more promising.A major study by Congress' Office of Technology Assessment recently concluded that the potential market is larger than any likely level of resource recovery for paper (as well as for iron, steel and aluminum) from now through 1995. Now the chief impediment to source separation programs is the fear that people won't cooperate.

It is up to the residents of Bethesda, Silver Spring, Potomac, Rockville, Wheaton and Kensington to prove that, given good local leadership, most Americans are still interested in being part of the answer.