Recipe For Sludge

Sift it, bake it, and put it on the garden. That is basically how contaminated soil or sludge is cleaned and returned to use. The baking process causes the contaminants to vaporize leaving the soil clean enough for a variety of human uses. Soil Restoration and Recycling (SR2) is a Chattanooga, Tenn., company that is using the process technically known as low-temperature thermal desorption to build a thriving international business.

The company has a reputation for environmentally sound practices. At its high-tech plant in Chattanooga, the power is supplied by methane gas which is piped to the site from the city landfill. The methane generates more energy than the plant can use, and the excess is put on an electrical grid and sold to local utilities. SR2 also collects rainwater on the 60-acre site to use in the treatment process.

Another plant in Knoxville is awaiting regulatory approval and the company is negotiating with 10 other communities to build methane-fueled plants. SR2 treats more than sludge. The process can be used to treat PCBs, coal tar, insecticides, herbicides, and oil, but not lead, heavy metals, or nuclear wastes. By linking up with landfills, SR2 is also helping to control methane fumes.

Mobile treatment equipment has been shipped to Mexico and Canada, and the company also sees expanding markets in Europe and Latin America where stricter environmental regulations are in force.