A year after chemical weed-killers contaminated compost in Vermont, the composting industry is calling for tighter federal regulations on persistent herbicides.
The industry wants the Environmental Protection Agency to require more rigorous testing and to set safe levels of the chemicals in compost.
States around the country – including Vermont – are taking steps to reduce the amount of organic waste going into landfills. The leaves and yard clippings have to go somewhere. And that’s meant a boon business for commercial composters who turn the stuff into soil and garden supplements
Lori Scozzafava is the executive director of the U.S. Composting Council. She said the industry is alarmed by the growing use of persistent herbicides, which are harmful to plants in minute quantities.
Scozzafava said her group closely followed the chemical contamination last year of compost produced by the Chittenden Solid Waste District.
“The U.S. Composting Council represents composters who are in the business of producing that compost. And if they can’t produce compost that is of high quality, then they can’t be in the business,” she said. “And so, right now, it’s really important for us to get to the bottom of the issue and ensure that the persistent herbicides don’t get into the composting stream.”
Scozzafava said her organization wants the EPA to set safe levels for the chemicals in compost. The council has also called for better testing methods to detect the chemicals in the parts per billion range.
Composters also want federal regulators to pressure chemical companies to develop herbicides that break down easily in compost.
Tom Moreau, general manager of the Chittenden Solid Waste District, said the opportunity for regulators will come later this year because the chemical company Dow needs to re-register its herbicide, aminopyralid, the compound that caused problems for the Chittenden operation. Moreau said Dow needs to develop the next generation of persistent herbicides.
The chemicals must be safe for animals, he said. But they also must be “compostable” and be destroyed in the composting process.
The persistent herbicides are sprayed on hay or grain fields to kill weeds. But when manure from the animals that eat the feed is composted, the herbicides remain active.
That’s what happened to the Chittenden Solid Waste District last summer. Horse manure from a farm in Colchester contained trace amounts of Dow’s aminopyralid. The compost then harmed plants in hundreds of gardens.
Moreau would also like to control Internet sales of the persistent herbicide because unlicensed applicators can buy the chemicals on-line. And he said the EPA should not have to rely on the chemical industry itself for product testing. In the Chittenden case, the only lab that could detect aminopyralid in the compost was Dow’s own corporate lab.
“We need independent verification of what they call the dose response, at what dose will deform a tomato plant from aminopyralid,” he said.
The Chittenden issue was not the first time persistent herbicides have contaminated compost. Ten years ago a compost facility in Spokane Washington was affected. More recent incidents have occurred in Pennsylvania and Nebraska.