The Perdue tanker truck parked behind the company slaughterhouse in Salisbury, Md., sucking up 6,000 gallons of sludge -- a muddy paste scraped from the plant's water treatment works. Fifteen miles west, outside Mardela Springs, Md., a tractor waited to take it off Perdue's hands.
The tractor belonged to Bio Gro, a Baltimore company that annually disposes of more than 4 million gallons of sludge from Perdue plants in Maryland and Delaware by injecting it into soils as fertilizer, according to a 1998 letter from Perdue to the Maryland Department of the Environment. Perdue buries another 3.9 million gallons annually near its slaughterhouse in Showell, Md.
Although sludge contains nutrients that feed crops, it fuels water problems when applied in greater quantities than plants can absorb. But how much was going into the field on this February day was something only Perdue and Bio Gro could know for sure.
Although Delaware and Virginia both regulate sludge as industrial waste, demanding that companies limit how much they put into soils, Maryland has, for nearly a decade, treated sludge as fertilizer.
Once a company sends a letter to the Maryland Department of Agriculture certifying sludge as agricultural waste, it can dump as much as it likes, with no inspections and no obligation to test soils or monitor wells for groundwater contamination.
The wide-open conditions prompted Perdue to haul more than 2.5 million gallons of sludge in 1997 from Delaware into Maryland. "We just feel very comfortable with the regulatory process they have here," explained John K. Chlada, Perdue's manager for environmental services.
Bio Gro's technical services administrator, Brooke Henderson, said the company tests soils and applies only as much sludge as crops can use, leaving none to run off or leach. "We're managing the material responsibly," she said.
Tyson Foods offered similar assurances, even as it was injecting so much sludge in fields near its Berlin, Md., plant that neighbors complained of the smell and of dogs returning home covered in chicken waste. When Maryland inspectors visited the site in 1998, after years of Tyson's repeated dumping, they found ponds of waste. Now the state is in court, accusing Tyson of polluting state waters and seeking more than $5 million in penalties.
In May 1998, Tyson formally promised Maryland it would apply only what crops could absorb. But according to soil tests taken by the state in July 1998, the Berlin field contained eight times as much phosphorus as crops required, and enough nitrogen to spur 13 years' to 45 years' worth of crop growth. When the Worcester County health department tested nearby wells, one yielded a nitrate level more than twice the EPA standard for safe drinking water.
As waste water treatment plants improve, sludge ironically becomes more of a problem: The newer plants catch more pollution before treated waste water slips into creeks, meaning more pollution is concentrated in the sludge.
In March, Maryland announced it would close its regulatory gap on sludge: Under new slaughterhouse permits now being drafted, plants would need to deliver formal plans for disposal, restrict applications to what crops need and submit to state inspections.
Perdue is now seeking ways to break down sludge during waste water treatment, rather than unload it on land. "The regulatory structure and framework is getting more difficult," Chlada said. "Public perception is a problem."