Growing evidence of a commercial herbicide in municipal compost has heightened concerns about the future of green waste recycling in California--a thriving business that could be seriously jeopardized if its end product is contaminated.
The herbicide, which has shown up in compost in San Diego and Los Angeles, is clopyralid, a weed killer. Manufactured by Dow AgroSciences, it is not harmful to people. But even trace amounts in compost can stunt or kill plants such as peas, peppers, tomatoes, potatoes and daisies. Clopyralid is used to kill dandelions in lawns and thistles on farmland and parkland.
Clopyralid in compost was detected in Washington state in 1999, and now is seen as a threat to green waste recycling programs. California has the most ambitious standards in the country for recycling lawn waste. During the past 10 years, the state has required cities and counties to divert 50% of their waste from landfills by 2000. Those that didn't comply faced penalties as high as $10,000 a day. Final results are not in, but Los Angeles diverted 55%.
Howard Levenson, California Integrated Waste Management Board supervisor, said clopyralid could put an end to the state's recycling success story and force tainted compost back to landfills.
"We're very concerned about the potential presence of this chemical and how it might impact the compost marketplace and how that then impacts our waste diversion programs," he said.
The chemical was introduced to California in 1997. In 2000, about 13,000 pounds of clopyralid was used in 54 of the state's 58 counties.
The chemical is popular with lawn care companies because one application lasts as long as a year. But the same persistence has made it a problem for the firms that convert garden waste to compost.
Alerted in May by reports of clopyralid damage to tomato and potato crops in Washington state, San Diego's Environmental Services Department started testing its compost and got its first positive results in June, and its second last week.
In late January, Los Angeles officials found clopyralid residue in compost.
"We naturally are becoming alarmed," said Stephen Fortune, the principal sanitary engineer with the Bureau of Sanitation. Los Angeles manages to meet its landfill quotas only by diverting 2,000 tons a day of yard waste for composting.
Statewide, green waste amounts to about a third of the 66 million tons of waste generated each year.
"It's a big part of the waste stream, which is why cities and counties have made such an effort to collect that stuff and keep it out of the landfill," said Ronnie Java, spokeswoman for the California Integrated Waste Management Board.
Stephen Grealy, San Diego's recycling program supervisor, said the presence of clopyralid in compost threatens the state's entire composting program. "All of our green waste recycling efforts that have been promoted and developed by the city and state for the last 20 years are at risk because of this," he said.
The most immediate threat to compost comes from contaminated grass clippings. Department of Pesticide Regulation records show that almost half the clopyralid used in the state is applied by landscaping companies. The heaviest applications are in Sonoma, Santa Clara, Contra Costa and Los Angeles counties.
In Washington state, where clopyralid has been used since 1987, contamination is so pervasive that Mike Pearson, lab director of the firm doing most of the tests, said 90% of tests for the chemical have been positive.
After public meetings in January, the Washington State Department of Agriculture is circulating draft rules that propose banning clopyralid from landscaping uses where clippings from treated plants are likely to enter the compost stream.
Dow spokesman Garry Hamlin said the company does not plan to contest the decision.
Inspired by proposed Washington restrictions, recently the California Compost Quality Council, a Sonoma-based trade association, pushed for a statewide testing program that might result in similar rules in California. It distributed a mass mailing offering a special rate for testing. It will present these to the California Integrated Waste Management Board on March 6.
An Environmental Protection Agency spokesman said the federal government also is monitoring clopyralid, and has an e-mail address for composters to use in reporting contamination: clopy email@example.com.
But it remains unclear how many composters will voluntarily consent to tests. Most of the state's 100 compost facilities are run by private contractors that could face bankruptcy if their product is tainted.