Definite answers to compost contamination proving difficult to find

The Green Mountain Compost facility. Photo by Kate Robinson

The Green Mountain Compost facility. Photo by Kate Robinson

The Chittenden Solid Waste District and federal and state officials are working together to find a solution to what CSWD head Tom Moreau calls a “multi-headed dragon.”

Since traces of persistent herbicides that damage plants were found in compost manufactured by the Green Mountain Compost, a subsidiary of the waste district, officials have tried to make sense of conflicting results from extensive testing over the last two months.

Tests by different labs on products from local compost companies and on “feedstocks,” or material used in the compost, produced different results. Some of the feedstocks, including horse manure samples and horse feed from various companies, tested particularly high for persistent herbicides.

Though herbicides were found in other composts made in Vermont, Green Mountain Compost is the only operation whose customers’ gardens have suffered ill effects from persistent herbicides. At least 276 customers whose gardens were damaged have received reimbursements from the company.

On Aug. 22, Moreau announced steps the district will take to prevent herbicide contamination in Green Mountain Compost. As of this week, the company will no longer accept horse manure for composting. It will begin using chicken manure as soon as the Agency of Agriculture gives its approval. Since some grass clippings in the original samples tested positive for clopyralid, new grass clippings are being set aside for now. They will be tested to see how long it takes for the herbicides to degrade.

The district is providing an “herbicide absorption kit” to customers who have confirmed herbicide exposure. Customers are asked to bring in garden waste in marked bags and take away a bag of oats to be planted from now into September and harvested in November. The oats cover crop is meant to speed withdrawal of residual herbicides from the soil and the material is not to be plowed back into the soil as is normally done with a cover crop. The oats are to be delivered back to Chittenden Solid Waste District drop-off centers in another marked bag.

Specialty horse feeds and herbicides

State and commercial compost experts say the horse feed industry has not adequately labeled products that have high levels of the herbicides.

Pat O’Neill of the Composting Association of Vermont says, “The point is not that horse farms are careless but that labeling of the herbicides does not sufficiently alert everyone down the compost economic chain from herbicide to field to feed to animal to manure to compost.”

Last week Lisa Jackson, chief administrator for the U.S. Environmental Protection Agency, met with state officials and large-scale composters about the still-fraught issue of persistent herbicides in compost. Tom Gilbert of Highfields Center for Composting presented talking points to Jackson. They ran from “safeguard[ing] the livelihood of composters and farmers and prevent[ing] further contamination of compost” to “develop[ing] a compostability standard for herbicides and pesticides” and setting up a fund to compensate composters affected by chemicals in EPA-approved products.

A moratorium on the use of persistent herbicides was requested by the U.S. Composting Council earlier this month. They want “compostability” added to the list of tests the manufacturers must do before the EPA approves the pesticide. So far the U.S. EPA has declined to do this.

To remedy the problem, Dan Goossen, GMC’s general manager, has changed the mix of feedstocks in the compost and has cooled it down by reducing the height of the piles during the second phase of composting from 12 feet to eight feet.

Another proposal on the table is requiring companies to label feed products that have high concentrations of the weed killers.

Cary Giguere, head of the pesticide program for the Vermont Agency of Agriculture, said a change in labeling protocol would take time and is a matter of negotiation between the EPA and the feed companies.

In the meantime, the state is helping the Chittenden Solid Waste District figure out how the herbicides got into the Green Mountain Compost system.

Moreau has consulted with research universities around the country, and he is convinced that most, if not all, of the contamination from picloram and clopyralid residues is from grain-based horse feed, as the herbicides pass intact through the animals into their manure. He thinks the tests the CSWD conducted will prove to have identified the right culprits, clopyralid and picloram.

Most Vermont composters use horse manure that is potentially contaminated by herbicides derived from specialty feeds such as Equine Senior manufactured by Purina. Experts, including Moreau, theorize that the reason these composts have not damaged plants has to do with a slower composting process that breaks down the herbicides. At Green Mountain Compost, a faster process has been used.

To remedy the problem, Dan Goossen, GMC’s general manager, has changed the mix of feedstocks in the compost and has cooled it down by reducing the height of the piles during the second phase of composting from 12 feet to eight feet.

CSWD won’t have proof that the herbicides have been rendered inert until plants grown in soil with their compost leaf out healthily. Bio-assays of the material (growing tests) are being started in a greenhouse provided by the University of Vermont.

A larger problem

The Green Mountain Compost crisis has turned out to be part of a larger problem, one which has different dimensions for different composting operations. Some of the composters for whom the persisting of herbicides now looms large are frustrated with the EPA.

Moreau says the EPA should have developed a standard method of testing for persistent herbicides down to the trace levels that can damage garden plants and should have a certification process through approved labs to conduct the necessary analysis when contaminated compost is found.

Steve Wisbaum, owner of the Champlain Valley Compost Co., who has been producing compost since 1996, says it’s his “hope that the EPA starts requiring manufacturers of products such as herbicides to conduct thorough compostability tests to ensure these products don’t end up contaminating finished compost and damaging plants.”

Meanwhile pressure is building for composting companies to take more material. New requirements for mandatory composting were put in place this summer. The Chittenden Solid Waste District will be required to take food waste by 2014 under the recently passed Act 148.
Gardeners buy thousands of cubic yards of Vermont-made compost and compost products each year from solid waste districts, farms that produce compost and independent composters like Karl Hammer, whose Vermont Compost is in demand nationwide, Steve Wisbaum and Tom Gilbert of Highfields. Demand for “amendments” like compost that enrich soil depleted by hungry plants and keep it moisture retentive and friable has risen steadily.

Composted waste is a soil additive that, while not qualifying under the stringent state rules as a “fertilizer,” has virtues such as available nitrogen, properties that keep garden soil from compacting so that plants can take up nutrients properly and microbes that perform many functions that help a garden succeed, including breaking down unwelcome organic compounds.

Composters who use food scraps (“residuals”) are keeping them from going into landfills where they create methane, are likely to smell and attract rodents, and become “leachate,” with unwelcome chemicals going into soil and water. Composters using garbage are regulated by the state and come under regular scrutiny. And sending food waste to, say, Green Mountain Compost is a benefit to businesses like Fletcher Allen Health Care. It costs them about $37.50 a ton to truck to the CSWD vs. $100 a ton to a landfill. (In Europe you can’t landfill food waste anymore, and Canada is almost as stringent.)

Kate Robinson

Comments

  1. Jane Stein :

    Fascinating story. Many thanks for keeping on this. I’m impressed by the efforts being made to figure this out and the things they’re learning in the process.

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