I, too, collect beer cans - in a way. I collect any brand, any number, I even collect soft drink cans at the same time.

My collecting urge began some months ago when I saw an advertisement for a recycling center. They were paying - paying, mind you - 20 cents a pound for aluminum. All kinds of aluminum. I was struck by a combination of ecological awareness and simple greed. Now that old beer cans had suddenly become a penny's worth of aluminum apiece, I began to notice them. Everywhere. The streets of Washington are practically paved with aluminum.

So now I am a roving collector as I stroll to the bus stop, to work and back home again.A casual effort nets me six to ten cans a day. My worst haul was four on a rainy day; my best was 19 after a long wait at the bus stop.

There is plenty of litter left for others, so I am passing on my hard-won experience to a new generation. They, too, can make their fortunes by mining the sidewalks and gutters over which they pass.

Metallurgy is the first problem. Beer cans come in two kinds: aluminum (worth about 1 cent) and steel (worth about nothing). Distinguishing the two takes practice. Gradually the eye learns to spot the telltale signs of worthless steel: the brown flecks of eary rust, the welded seams. The hand learns to detect the extra weight of a steel can and to discard it as part of the same motion that picked it up. Until such sophistication develops, the novice can test cans with a magnet (aluminum is nonmagnetic).

On-site processing is essential. It is both awkward and ostentatious to walk down the corridors of power clutching an armload of beer cans picked up on the way to work. It is essential that a can be rendered flat enought to slip inconspicuously into a briefcase, a lunch bag or a quarterly report.

There are several ways in which a little human effort can change a symmetrical beer can into a flat splotch of metal. My favorite method is to bend in the center of the can with a quick thrust of my thumbs. (I especially like this way because I was the only one in my high school who could never bend one of those solid steel beer cans in The Happy Days.) Then place the can on the pavement, dented side up, and press down the ends with the heel of a shoe, being careful to place the shoe accurately and to apply a slow, steady pressure. A flamenco stomp on the can may be added for exercise or from sheer animal spirits, but serious collectors avoid it.

When this collecting becomes popular, we will doubtless see special handtooled leather carrying cases, complete with individual compartments to hold squashed cans side by side. Until then, the pioneer collector will carry off his prizes in whatever is available; the back corner of a briefcase, a used lunch bag or a side pocket. I prefer a plastic bag, which serves as a handy barrier against dampness. The collector quickly learns that old beer cans are damp.

And that brings us to danger. The greatest hazard in this eco-collection is not jagged edges, curious pedestrians or passing cars. It is unfinished drinks. By my own estimates, about one-fifth of dicarded beer and soft drink cans still contain from a few dribbles to a few ounces of their original contents. The veteran collector quickly learns caution, dexterity (the quick upending of the can while it is still held at arm's length) and the use of plastic bags.

To generalize from a few street corners to the entire United States, it would seem that, sitting in discarded cans, there is an unnoticed reservoir of some 200 million galons of fluid, enough to fill 5,000 swimming pools with an elixir composed of 35 percent Schlitz, 10 per cent Pabst, 5 percent Lite, 30 percent Coke, 5 percent Mr. Pibb, 10 percent Mountain Dew, and 5 percent Other. I'm not sure whether this is a health problem or an untapped resource.

A word about explanations: You don't need any. I began my career with several excuses on the tip of my tongue: "I'm cleaning up the environment"; "My kids and I are having a contest"; "I need the money." I never had a chance to use one. It seems the average bystander, seeing a middle-aged bureaucrat snatch a beer can from the gutter, stomp it flat and slip it into a briefcase, does not ask questions. Nobody wants to get involved any more.

Gradually the grocery bags in my garage are filling up with stomped-flat cans. At about $1.50 a bag, I will soon have enough to buy the gas to get them to the recycling center. Of course by that time (early 1981) the recycling center may have gone out of business, and I will have to put 10 sacks of beer cans out into the garbage. Look out, Environment! Here they come again!