In August 1928, Madison, Wis.’s research into the effectiveness of using wastewater sludge as fertilizer was featured in The American City. Working with a biochemist, the city turned the solids collected at the sewage treatment plant into a fertilizer that looked like dried peat, felt similar to soil and was odorless. It contained nitrogen, phosphorous and potassium, and tests on crops like oats and corn showed that the city’s fertilizer performed as well as higher-priced commercial fertilizer and better than cattle manure. Madison sold its product for 50 cents per cubic yard, generating almost $1,000 annually.
Madison’s fertilizer production has continued, and since 1979, the Madison Metropolitan Sewerage District has been producing liquid fertilizer and soil conditioner through its Metrogro Program for farms in four counties. Currently, 450 farms use the product on 5,000 acres annually, predominantly to grow corn. Metrogro is applied as a liquid using special equipment that injects the biosolids approximately 8 to 10 inches beneath the soil surface. The district’s Environmental Management System (EMS) is platinum-certified, the highest level of recognition awarded by the National Biosolids Partnership (a consortium of the U.S. Environmental Protection Agency, the Washington-based National Association of Clean Water Agencies and the Alexandria, Va.-based Water Environment Federation).