It was early and I'd been up way too late the night before watching an old Humphrey Bogart movie.

Some scientists at the General Motors Corp. Technical Center were explaining a complex thermal recycling process called pyrolysis. Somebody said it might someday make it possible to "mine" landfills. That was the trigger.

Suddenly I see Bogie, rifle in hand, lying behind a worn-out truck tire on top of a huge reeking garbage pile. EPA agents on horseback are approaching from below, asking if he has a permit to mine the trash mountain.

"How do I know you're really from the EPA?" Bogie asks warily from behind the tire. "Show me your badges."

The lead horseman looks at him menacingly. "Badges? Badges? We're from the EPA. WE don't need no STINKING badges!"

Was there something in the coffee?

Reusing parts and materials on today's vehicles is everyone's vision of recycling. But just imagine digging up shredded instrument panels and seats and tires from old landfills and recycling them for profit. That's the ultimate dream for pyrolysis, a controversial, 2,000-year-old process that chemically breaks down materials with heat but without burning. In this case, scrap rubber and plastics are heated to 1,400 [degrees] F (760 [degrees] C) in a sealed, oxygen-free chamber (preventing combustion), which causes them to chemically break down and turn into fuel oil, gas and potentially valuable ash.

Unfortunately, basic economics may prevent pyrolysis from ever taking off. It could turn into a gold mine if landfill fees and oil prices soar, but neither looks likely in the near future. Environmentalists aren't cheering for the process, either. Many complain it's closer to incineration than recycling. Prponents say it isn't so, but the stigma persists.

This leaves few incentives for potential plastic-scrap prospectors.

Nevertheless, a few hardy souls at GM and elsewhere are forging ahead. They've already built some small demonstration units. Irvin E. Poston, manager of Polymer Composites at Gm's Manufacturing Center in the Tech Center complex, is hoping GM can entice an outside contractor or consortium into building a larger experimental pyrolysis operation capable of processing 2 tons of waste per hour directly at the vehicle shredding machine.

He says GM has talked with several groups, but admits it's a tough sell on a purely economic basis: A pyrolysis unit would cost $1 million to $2 million. GM wants to contribute technology, but doesn't want to fund the project.

Anyone buying into a large-scale pyrolysis operation will have to be interested in its long-term potential, not near-term profits, Mr. Poston emphasizes. Some government funding may be necessary to get things started. Right now, the steel portion--about 75% of a car's total content by weight--already is recycled. The other 25%, consisting of plastic, rubber, glass, dirt and other materials is ground up into an ugly mess known as automotive shredder residue (ASR) and carted off to landfills. About 10 million scrapped cars create about 3 million tons of ASR each year.

Automakers and plastic producers are trying to reduce the plastic portion of ASR by making major plastic parts easier for dismantlers to remove and sort so they can be somehow reused. But unless they are precisely sorted according to chemical composition, they can't be reused at all.

A new labeling system allows plastics to be identified and sorted more easily. But these benefits won't be realized for another 10 to 15 years. In the meantime, ASR from junkers is piling up.

Enter pyrolysis. Used for centuries to make charcoal from coal, and by the Germans in World War Il to produce synthetic oil, it's the only process that can turn ASR into anything of value: the oil it produces is like #2 heating oil, and only 25% of the high-quality gas produced is needed to fuel the process.

The ash has been successfully used as a reinforcement material to create high-tech concrete that doesn't shrink or swell and as filler for new polymer composite formulations.

Even so, few seem to think it's possible to make a profit using pyrolysis on ASR. It'll be a shame if GM can't find a partner in the venture and this opportunity is lost. Then we'll all be like the banditos who robbed Bogart in The Treasure of the Sierra Madre. They took his animal hides, but they threw away a fortune in gold dust because they thought it was just dirt.