Biosolids are nutrient-rich organic materials that result from the treatment of wastewater. They are commonly recycled as a fertilizer for crops and as a soil amendment to improve depleted soils. However, because biosolids have low levels of pollutants and pathogenic organisms, their use in the U.S. is regulated by the Environmental Protection Agency (EPA). Managing biosolids safely and effectively is an important issue for communities because of the quantities that are produced. The EPA estimates that the annual U.S. production of biosolids, recorded at seven million tons in 2000, will continue to increase.

In developed countries, biosolids are produced at treatment facilities that receive wastewater from homes, businesses, and industries. Domestic wastewater carries organic matter from food preparation, cleaning of clothes and cookware, and human waste. Industrial wastewater may contain organic material, oils, metals, and chemical compounds, but it is usually pretreated at the industrial facility to...