Sludge, a free fertilizer for farmers, can pose health and environmental risks
For 30 years, sludge has been applied to farmland throughout the U.S. to fertilize fields that grow food for livestock and, in some cases, humans. Yet it's only in the last decade that sludge has garnered attention from citizens, scientists and the FDA because of the uncertainty of its contents.
Sludge isn't just a byproduct of waste that creates optimal fertilizer; it can contain heavy metals, bacteria like staphylococcus (the cause of staph infection) and thousands of chemicals yet to be tested for safety by the FDA.
Sludge begins as human waste, manufacturing chemicals, landfill runoff—essentially, anything that flows down a drain, which makes knowing its contents nearly impossible. Sludge infiltrates the food chain through livestock that ingest sludge while grazing on sludge-applied fields or eating food grown in those fields. Sludge comes full circle when people eat the crops grown in the field, consume the meat or drink the milk of animals that directly or indirectly ingested the sludge. It can also enter waterways used for drinking water or irrigation.
In the Triangle, thousands of acres of farmland are spread with sludge generated from wastewater treatment plants and then hauled and applied by Houston-based Synagro Technologies, Inc., the largest recyclery of waste in the United States and a company with a problematic environmental record. While there are federal and state rules governing sludge, there is little enforcement or monitoring of the practice. And local governments have no voice in regulating the sludge that is sprayed on fields in their jurisdictions.