(See DISCOVER's earlier coverage of "Anything Into Oil" here and here. See the follow-up article here.)

The smell is a mélange of midsummer corpse with fried-liver overtones and a distinct fecal note. It comes from the worst stuff in the world—turkey slaughterhouse waste. Rotting heads, gnarled feet, slimy intestines, and lungs swollen with putrid gases have been trucked here from a local Butterball packager and dumped into an 80-foot-long hopper with a sickening glorp. In about 20 minutes, the awful mess disappears into the workings of the thermal conversion process plant in Carthage, Missouri.

Two hours later a much cleaner truck—an oil carrier—pulls up to the other end of the plant, and the driver attaches a hose to the truck's intake valve. One hundred fifty barrels of fuel oil, worth $12,600 wholesale, gush into the truck, headed for an oil company that will blend it with heavier fossil-fuel oils to upgrade the stock. Three tanker trucks arrive here on peak production days, loading up with 500 barrels of oil made from 270 tons of turkey guts and 20 tons of pig fat. Most of what cannot be converted into fuel oil becomes high-grade fertilizer; the rest is water clean enough to discharge into a municipal wastewater system.

For Brian Appel—and, maybe, for an energy-hungry world—it's a dream come true, better than turning straw into gold. The thermal conversion process can take material more plentiful and troublesome than straw—slaughterhouse waste, municipal sewage, old tires, mixed plastics, virtually all the wretched detritus of modern life—and make it something the world needs much more than gold: high-quality oil.

Appel, chairman and CEO of Changing World Technologies, has prodded, pushed, and sometimes bulldozed his way toward this goal for nearly a decade, and his joy is almost palpable. "This is a real plant," he says, grinning broadly. He nods at the $42 million mass of tanks, pipes, pumps, grinders, boilers, and catwalks inside a corrugated steel building. The plant is perched 100 yards from ConAgra Foods' Butterball plant, where 35,000 turkeys are butchered daily, surrendering their viscera to Appel's operation. The pig fat comes from four other midwestern ConAgra slaughterhouses. "To anybody who thinks this can't work on an industrial scale, I say, 'Come here and look.' This is the first commercial biorefinery in the world that can make oil from a variety of waste streams."

Still, Appel looks wearier than he did when Discover broke the news about his company's technology. Back then, when the process was still experimental, Appel predicted that the Carthage plant would crank out oil for about $15 a barrel and rack up profits from day one. But the plant was delayed by construction problems, and federal subsidies were postponed. After it started up, a foul odor angered town residents, leading to a temporary shutdown in December 2005. Production costs turned out to be $80 per barrel, meaning that for most of the plant's working life Appel has lost about $40 per barrel. As recently as last April, he feared the whole operation might implode. "There have definitely been growing pains," he says. "We have made mistakes. We were too aggressive in our earlier projections."

But now, after more than $100 million in private funding and $17 million in government grants, several hurdles have tumbled. The Carthage plant has been optimized and is expected to turn a small profit. A tax credit has leveled the playing field with other renewable fuels like biodiesel and ethanol. Appel is confident that new ozone scrubbers and other equipment will abate the odors. State officials are warily optimistic. "We are not hoping to shut them down [permanently] and take away jobs," says Connie Patterson, spokesperson for the Missouri Department of Natural Resources. "We have given them a window of opportunity to solve the problem."

Others are optimistic too. "I'm impressed," says Gabriel Miller, a New York University chemistry professor and a consultant to KeySpan Corporation, a gas and electric utility that serves New York. "The fuel that comes out is better than crude, and you don't need a refinery to use it. I think they can bring it deep into commercialization." Miller has recommended that KeySpan burn the oil in its generators.

Appel, a former Hofstra University basketball star, leans his 6-foot-5-inch frame against a counter in the company's lab and rubs his face. He says he is confident that the process can indeed solve thorny waste problems, supplement oil supplies, become an odor-free "good neighbor," and at last, become immensely lucrative.

The catch? It may not happen in the United States.

Left to right: An on-site lab checks oil and fertilizer quality a dozen times daily; some of the plant's 45 workers stroll under oil-bearing pipes; daily maintenance logs are kept on a whiteboard; (Below) a truck is weighed before dumping turkey leftovers; the scrubber system's exhaust stack, wrapped in a steel framework, looms over the plant.

Appel has shepherded development of the thermal conversion process(previously known as the thermal depolymerization process; Appel changed the unwieldy moniker last year) since 1997, building on organic-solids-into-oil research stretching back nearly a century. By 1999 he had lined up investors, hired an engineering staff, and had a pilot plant chewing through seven tons of waste daily in a Philadelphia industrial yard. Early in 2003, company officials predicted their first industrial-size plant would be steaming ahead 24/7 in Carthage by that summer. As it turned out, continuous production did not start until February 2005.

Which is surprising because at first blush, the thermal conversion process seems straightforward. The first thing a visitor sees when he steps into the loading bay is a fat pressurized pipe, which pushes the guts from the receiving hopper into a brawny grinder that chews them into pea-size bits. Dry feedstocks like tires and plastics need additional water at this stage, but offal is wet enough. A first-stage reactor breaks down the stuff with heat and pressure, after which the pressure rapidly drops, flashing off excess water and minerals. In turkeys, the minerals come mostly from bones, and these are shunted to a storage bin to be sold later as a high-calcium powdered fertilizer.

The remaining concentrated organic soup then pours into a second reaction tank—Appel says the two-stage nature of the process distinguishes it from dozens of failed single-stage waste-to-oil schemes devised over the last century—where it is heated to 500 degrees Fahrenheit and pressurized to 600 pounds per square inch. In 20 minutes, the process replicates what the deep earth does to dead plants and animals over centuries, chopping long, complex molecular chains of hydrogen and carbon into short-chain molecules. Next, the pressure and temperature drop, and the soup swirls through a centrifuge that separates any remaining water from the oil. The water, which in the case of slaughterhouse waste is laden with nitrogen and amino acids, is stored to be sold as a potent liquid fertilizer (see "Garden Delights," next page). Meanwhile, the oil goes to the storage tank to await the next truck. The whole process is efficient, says Terry Adams, the company's chief technology officer: Only 15 percent of the potential energy in the feedstock is used to power the operation; 85 percent is embodied in the output of oil and other products.

The oil itself meets specification D396, a type widely used to power electrical utility generators. The oil can be sold to utilities as is, further distilled into vehicle-grade diesel and gasoline, or, via a steam process, made into hydrogen. Until last year, Appel distilled his output on-site, but he has since decided to sell the oil directly to utilities and refineries. "We just don't make enough volume to make operating our own refinery viable," he says.

So why has success been so long coming? Basically, Appel says, everything has been more complex and expensive than anyone guessed. First, the conversion process needed tweaking. Each variable—temperature, pressure, volume, tank-residence time—needs to precisely match the feedstock, which proves to be no mean feat on an industrial scale. "The really difficult thing has been finding the sweet spot in the process parameters," says Appel. "This isn't a laboratory. We have to respond to the real world of varying supply. If I get two truckloads in a row of just feathers, I need to deal with that high-protein peak. Or if I get too much blood at once, the result is too much water." The solution has been to blend disparate truckloads of stock in a holding tank, making what enters the process relatively consistent.  

"Fat, fiber, protein, moisture, ash—getting those right, that's our mantra," says Jim Freiss, vice president of engineering. "Now we are able to nail the same quality every day." Freiss says he and fellow engineers Terry Adams and William Lange "have learned so much that I am very confident we can build a second plant that's optimized from the start."

Chemistry was not the only challenge. Since 2004, the federal government has subsidized biodiesel, usually made from soybeans, at $1 a gallon. It gave Appel zero for the fuel he produced from turkey guts. "It was hard to believe that a competitor could walk away with a dollar a gallon while we were excluded," Appel says. In August that hole was plugged: The fuel Appel makes, known officially as renewable diesel, received a subsidy of $1 per gallon from the Energy Policy Act of 2005, which took effect in January. That boosted the company's income by $42 a barrel, allowing a slim profit of $4 a barrel.

Appel offers no apologies for needing government largesse to make money. "All oil, even fossil-fuel oil, gets government subsidies in the form of tax breaks and other incentives," he says, citing a 1998 study by the International Center for Technology Assessment showing that unsubsidized conventional gasoline would cost consumers $15 a gallon. "Before we got this, I had the only oil in the world that didn't get a subsidy."

Another hurdle: Within months after opening in February 2005, the plant smelled, and by August it had been hit by six notices of emissions violations by the Missouri Department of Natural Resources. But some in the town, which has other large food processing operations, contend the new plant was unfairly singled out. "The thing was, any odor at all was blamed on them," says Mayor Kenneth Johnson. In any case, Renewable Environmental Solutions, the subsidiary of Changing World Technologies that runs the Carthage plant, spent $2 million on biofilters, scrubbers, and other odor stoppers. Between July and late September complaints had dwindled from 23 to 5 a week, says Mark Rader, an environmental specialist with the department's southwest regional office.

Nonetheless, the Department of Natural Resources issued a temporary shutdown order for the plant in December, prompting Appel and his colleagues to install more ozone scrubbers. But even critics say the persistence of a smell does not invalidate the technology. The plant is just four blocks from downtown Carthage and two blocks from residences. Building future plants in less dense areas would "make more sense," says Department of Natural Resources spokesperson Connie Patterson.