"Biosolid" Fertilizers Cheap, but, Worrisome

Jun 22, 2011

Given the high price of petroleum-based fertilizers, more farmers are considering sludge from sewage treatment plants.  It’s free, but, many local governments worry about the safety of so-called biosolids.  And, as Sandy Hausman reports from Virgina, it also makes some farm neighbors uneasy

Carrsbrook is a leafy neighborhood in Charlottesville.  Homes here, built in the 60’s and 70’s, routinely sell for more than $350,000.  It’s a  short drive to the airport and the shopping mall, but every so often a truck will come through, pulling some kind of farming equipment. 

That’s because Carrsbrook is adjacent to 88 acres of agricultural land.  From his backyard, Ray Caddell has a clear view of the property.  It’s in a flood plain where nothing can be built, so the owners lease it to a farmer and take an agricultural tax credit,  which was fine with Cadell until three years ago when he saw a sign announcing biosolids would be applied.  It was not a term he knew.

“Turns out it’s just a polite word sewage sludge,” said Caddell.”

Caddell didn’t think it was right to be bringing human waste from a treatment plant in Washington DC into a residential area.

The first time biosolids were applied, Caddell’s daughter started having more frequent asthma attacks, and his wife developed a cough that lasted months.  Doctors couldn’t figure out what was wrong, and Ray wondered if dangerous components of biosolids might get into drinking water or the corn grown in that field. 

By law, the farmer had to mix biosolids into the ground within 48 hours, so the smell wasn’t a big problem, but other rules gave Ray pause.  If it’s so safe, he wondered, why can’t cattle graze on a piece of treated land for a month?  Why can’t farmers plant root vegetables in treated fields for three years, and why is this whole business regulated by the Environmental Protection Agency?

Greg Evanylo, a professor of environmental sciences at Virginia Tech, has been studying biosolids since 1975, and so have many other scientists concerned about safety. 

Where the EPA saw any real risks, he says it drafted regulations to reduce them.  There’s some question about whether airborne biosolids could make people sick, but farmers who work with the stuff have not reported health problems, and scientists say pathogens in biosolids are killed by treatment, sunlight, microbes in the soil and the passage of time.

Biosolids may also contain heavy metals – like mercury, copper or lead, industrial wastes, pharmaceuticals and hormones excreted by humans.  Evanylo says research suggests levels are very low and in some cases less prevalent than in our homes.

Still, the state is formulating new rules for the application of biosolids.  Albemarle County Board President Ann Mallek, herself a farmer, says it’s about time.

While the experts debate the relative safety of fertilizing with biosolids, there is widespread agreement that scientists must keep an eye on possible harmful effects, and government must keep an eye on the science.