While making a cup of coffee, Frank Pringle stumbled onto something. Now, after years of experimentation, he fervently believes he is taking important first steps that could play a role in meeting acute energy demands.

And he says, his voice filled with passion, that he's on the way to a new approach to cleaning material dredged from rivers and disposing of worn-out tires.

For years, according to one who has watched him, some dismissed Pringle as "that microwave guy." But over the last year, he has gained recognition at the U.S. Department of Energy and other places where oil-supply issues are studied. Over the last month, the potential of his inventions, for which he is seeking patents, has been heralded by Popular Science and Time magazines.

Last week, Dinesh Agrawal, director of Pennsylvania State University's Microwave Processing and Engineering Center, signed a contract with Pringle's company, Global Resource Corp. of West Berlin, N.J., to help him get funding and develop large-scale applications.

"It is very, very significant, what he has done," said Agrawal, a professor who has been studying microwave uses for 20 years and now is a minor stockholder in Pringle's company. "It could benefit entire mankind."

How Pringle, 64, of Marlton, got this far is a saga of experimentation, ardor and serendipitous discoveries by a man who had no background in the energy field. Lots of great discoveries were accidental, Agrawal said.

The happy ending Pringle envisions is far from assured. "There are lots of issues in scaling up to millions of tons a month. It will involve four or five disciplines working together to resolve challenges," Agrawal said.

Pringle is no university scientist. In fact, in the early 1960s, he dropped out of Hiram College in Northeast Ohio to play professional baseball. After three weeks on a Cleveland Indians farm team in Arizona, he injured his rotator cuff. "They sent me out there on a turboprop airplane. I came home on a bus," he said.

He never got a college degree. But he kept learning, he said, and has run an engineering and recycling company, and patented four materials-handling inventions.

When he made the cup of coffee in the early 1990s - the one that put him on the road to where he is now - he was trying to rebound from a big disappointment. He had invented what he called an economically viable way to recycle glass. But a potential customer found a problem he had overlooked: Much of discarded glass is broken or gets broken before it gets to the recycling facility, and ceramics that look like glass get mixed in.

If ceramic material finds its way into a recycled beer bottle, with contents under pressure, it could blow up.

While using an ordinary microwave oven to make a cup of coffee, he discovered that glass gets hotter than other cups and dishes. "I spent the next two days microwaving everything I could find and recording the temperatures," Pringle said.

He read up on microwave technology, and learned from many others already experimenting in the field that there are more than 10 million frequencies. "There's got to be a frequency that excites ceramics," making it easy to separate it from glass.

Then came the big Philadelphia tire fire. It started on March 13, 1996, in an illegal Port Richmond tire dump. It caused damage that closed busy Interstate 95 for eight days, sparking news stories about the growing problem of getting rid of old tires.

Pringle's fascination quickly turned to microwaving car tires. Working in a North Carolina laboratory, Pringle said, "we dialed and dialed up microwave frequencies until a tire went poof."

Car tires, of course, have steel belts, and metal, - as many home microwave-oven users have accidentally discovered - reacts poorly to microwaves. "The microwave door hit me in the head a few times before I figured out how to deal with that," Pringle said.

Oxygen causes that bad reaction. So he microwaved tires in a vacuum. After many trials and errors, he, chief engineer Hawk Hogan, researcher George Birch, and others found a frequency that turned tires into useful material. With 50 cents' worth of electricity for the large microwave he has fabricated, he demonstrates. He turns a single 14-inch car tire, one small piece at a time, into 1.2 gallons of diesel fuel, 7.5 pounds of carbon black, 50 cubic feet of combustible gas, and two pounds of high-strength steel.

Through tubes from the vacuum chamber inside the microwave, the diesel fuel goes into a glass container and the combustible gas is captured in a tank. The solids remain in a container inside the oven.

Each demonstration finishes with a flourish, when he flicks a cigar lighter to a torch and burns off the gas he just produced.

"I've tested the diesel fuel in my pickup," Pringle said. "The truck ran fine, but the exhaust smelled like burning rubber. At stoplights, people around me kept checking to see if they'd left their parking brake engaged."

He later dialed the right frequency to harvest usable fuels from material dredged from river bottoms.

Brian J. Preski, who heads the governmental-affairs practice at the Wolf, Block, Schorr & Solis-Cohen law firm, was until recently chairman of the Philadelphia Regional Port Authority. "He's a good guy," Preski said of Pringle. "He came to us and said he had a new approach to cleaning dredged material."

Preski observed Pringle's demonstrations. "What was left was aggregate material that was completely clean and safe." Preski reviewed articles in engineering journals and decided there was potential in what Pringle developed.

The port authority will seek bids on disposing of material dredged to deepen the Delaware River shipping channel, and Pringle plans to submit a proposal.

Pringle keeps experimenting and learning.

He says he has microwaved lawn cuttings into a substance that could be refined into alcohol fuel. In small-scale laboratory experiments, he demonstrates turning both oil shale and coal into clean energy. He thinks he's found a way to extract huge amounts of thick oil left in long-abandoned wells and produce fuel that is cheaper than foreign oil.

The capped wells alone would add several hundred years to the nation's oil supply, he says with intensity, pointing to charts and scientific papers and journals.

Pringle said he started with about $450,000 - "that's a ballpark estimate" - of his own money. About 2,000 friends, neighbors and acquaintances have invested $3.5 million, buying shares, said his company's chief financial officer, Jeff Andrews. The company's shares are thinly traded on the OTC Bulletin Board.

Working in a South Jersey industrial park, Pringle's small company can produce some products on its own. To have any chance at pulling off big projects, "we'll need a big brother," he said.

Agrawal, the Penn State scientist who has received a "small amount" of Global Resource stock in exchange for his research collaboration, said the next task is to "understand the science behind what Frank does with microwaves. We know what he can do. To do it on a large scale requires understanding why it happens."

Contact staff writer Henry J. Holcomb at 215-854-2614 or hholcomb@phillynews.com

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