The Value of Sludge

Day after day, residents and industries in the Chicago area flush 1.5 billion gallons of raw wastes into the city's sewers --out of sight and mind. The flushings become the metropolitan sanitary district's Sisyphean task; the engineers must not only treat the ceaseless torrents of raw sewage but also find some place to put the day's residues--and space for such byproducts is limited. Yet Chicago now seems to have solved the dilemma with such practical and ecological wisdom that its program may well become a model for other cities while incidentally and fortuitously reclaiming some of the U.S.'s most ravaged land.

Despised Origins. Like several other cities, Chicago purifies sewage with a combination of mechanical and chemical processes. One product is clean water. The other is "sludge," a black goo that smells like tar and has the consistency of pea soup. The sanitary district's problem has been what to do with the sludge. In the past, Chicago sold tons of dried sludge to Florida citrus growers as fertilizer. But drying the waste caused massive amounts of air pollution and was expensive ($59 a ton).

Trying to use it undried to fertilize farms in nearby Kankakee County proved a flop, because sanitation men ran up against a basic American prejudice. Though U.S. farmers have never hesitated to use animal manure, they quailed at the thought of sludge, which is basically purified human manure. Public outcry effectively banned sludge from the county. In desperation, the sanitary district dumped the goo into man-made "lagoons" that it had bulldozed years before into 450 acres of the potentially best industrial land around Chicago.

As the lagoons slowly filled, district engineers, aided by technicians from the University of Illinois, tested sludge in demonstration projects. The results were startling. The soupy product was easy to spray where needed with standard irrigation equipment and did not smell bad --both distinct advantages over animal manure. Better yet, used as a soil nutrient, it caused clay and even silicate sand to bloom. Still, nobody wanted sludge because of its despised origins. "We flew thousands of miles looking for people to take it," says Ben Sosewitz, general superintendent of the district. "Some people laughed at us. Though we had developed economical, beneficial methods of disposal, we were always frustrated by lack of public acceptance."

A year ago, officials from downstate Fulton County heard about sludge's marvels and thought it might help solve their major problem. Blessed with abundant reserves of coal, the county was cursed with strip mining. Each year 2,500 acres of topsoil was peeled back, the coal gouged out, and the land rendered unfit for any use but as poor pasturage. In total, 40,000 acres of Fulton County had been ripped and scarred so completely that any remedy was welcome. Even sludge. Would the sanitary district like some of the land?

Goo Spray. District officials did not need to be asked twice. After buying 7,000 acres, they set up a small test project. "It was amazing," says Bart T. Lyman, chief of maintenance and operations. "Corn planted on three acres of land treated with sludge grew eight feet tall. By comparison, the stalks on two acres of untreated land were stunted, only three feet high."

Barges now carry the sludge down the Chicago Sanitary and Ship Canal to Fulton County where it is stored in huge reservoirs. Next spring the goo will be sprayed over the torn, acidic land. If the sludge works as well as anticipated, the acreage will return to productivity, and the district expects to lease it for recreation and farming (corn, soybeans, hay). No air or water pollution attends the process, and disposal costs will in time be cut to $25 per ton.

Eventually the sanitary district expects to buy up to 50,000 acres of stripped land--enough to use all the sludge Chicago can produce. Since the U.S. already contains about 2,000,000 acres of similarly ruined land, lowly sewage may yet turn out to be a prized commodity, the salvation of landscapes of desolation.

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