CHATTANOOGA, Tenn. -- Take 30 tons of gasoline-soaked soil. Sift in giant rotating cylinder. Bake at 750 degrees. Cool and package. Spread on softball field. Play ball!
This is the recipe followed by Soil Restoration and Recycling, a Chattanooga company that has been building a reputation for efficient and environmentally sound ways to recycle contaminated soil and sludge.
The process just described is called low-temperature thermal desorption. The soil or sludge is "cooked" to vaporize contaminants. What's left can then be used for athletic fields. Or even gardens.
The technology isn't new, but the company, known as SR2, adds a few environmentally friendly twists.
Its high-tech plant is largely fueled by methane gas captured in underground pipes from garbage fumes at the Chattanooga landfill. The fumes can generate more power than the plant needs, and the excess is put on an electrical grid and sold to local utilities. Rainwater is captured on the 60-acre site for use in the treatment process. And SR2 intends to use heat siphoned from the plant to warm greenhouses on the property.
"It's good for our city," Chattanooga City Councilman Dave Crockett said. "It creates a local business opportunity and it's good for the environment. It helps us be a living laboratory based on principles of sustainable economic development."
The company doesn't just cook soil and sludge. It also can treat PCBs, coal tar, insecticides, herbicides, oil and other pollutants.
John Cipriani, SR2's regional facility manager, said the company hopes its location -- in a once-heavily polluted city that now bills itself as a model environmental community -- will help draw business.
SR2 already has set its sights beyond Chattanooga.
A Knoxville plant is awaiting regulatory approval, and the company hopes to sign deals with other communities and build 10 more methane-fueled plants. The U.S. Environmental Protection Agency has been helping SR2 link up with communities looking to control landfill gas fumes.
SR2 has international aspirations as well. Its mobile treatment equipment can be shipped to other states and countries for on-site projects. The company already has sent seven truckloads of equipment weighing 100,000 pounds to Mexico to clean petroleum from soil.
Thermal desorption was developed in the late 1980s when the federal government began requiring large-scale treatment of contaminated soils and sludges -- specifically targeting leaky underground gasoline storage tanks.
Incineration was expensive and researchers began looking for cheaper ways to remove pollutants. They found they could "cook" rather than incinerate the waste and save on fuel costs.
The technology has been used at Superfund sites targeted by the federal government for cleanup in Massachusetts, New Jersey, Florida, Ohio, and at plants in Texas and in other states.
SR2 has restored a Chattanooga property where a company manufactured carpet and textile dyes for 20 years, killed parasites and viruses in wastewater-contaminated soil in Dalton, Ga., and removed contaminants at a Tennessee Valley Authority storage yard in Stevenson, Ala.
The approach has its limits; the processing can emit dangerous vapors that must be closely monitored. Rigorous testing is needed to ensure the soil has been thoroughly cleaned and is safe. And the technology is not effective enough to process lead and other heavy metals, along with highly toxic contaminants such as nuclear waste.
Communities also need to be careful how they use the cleaned soil, said Tom Tiesler, Tennessee's solid-waste management director.
"If the material is treated to the point where contaminants are virtually the same as virgin soils, it doesn't pose a risk to the environment," he said. "But because it's a processed waste, we say it can't be used for just anything."
Despite these drawbacks, the technology is popular and remains cheaper than incineration.
The privately held SR2 would not reveal its profits, but said it has processed more than 1.5 million tons of contaminated materials in the last seven years.
The company is expanding at a difficult time in the industry. Stiff competition has cut earnings for many firms and the supply of contaminated soil is dwindling in this country, according to Ramin Abrishamian, a waste-treatment consultant who has overseen installation of thermal desorption plants at refineries in the United States and Europe.
"The amount of soil went down because (the companies) completed so many underground tank jobs," he said. "The whole environmental and regulatory conditions have changed because of Congress. There's (also) less enforcement, so more soils aren't being brought into the marketplace."
SR2 business development director Glen Palmer isn't worried.
The company has won jobs in Mexico and Canada, and any community or utility struggling to find ways to dispose of waste is a potential customer, he said. More work also is available in South America and Europe, where environmental regulations are now being implemented, he added.
In the past two years, SR2 acquired Four Seasons Environmental Inc.'s Thermal Treatment Division in Greensboro, N.C., and Southwest Soils Remediation Inc. in Tucson, Ariz., and the company now has permits to work in about 24 states.
SR2's soil sales are in their infancy, but Mr. Palmer hopes to expand the business to processing 50,000 tons annually. Its soil already has been used at a softball stadium that opened this year in Chattanooga.
"We look at SR2 as more than a soil remediator," Mr. Palmer said. "When we go to a community ... we're able to take once unused properties and turn them into an active part of the tax base."