San Francisco wears its environmental consciousness like a green badge of honor. A city department even gives away processed sewage sludge for use in community, backyard, and school gardens.
The biosolids compost has drawn the ire of a public interest and environmental advocacy group.
The Organic Consumers Association doesn't think the variety used in gardens or the one laid on farmlands is tested enough and is waging a national campaign against its use. The sludge, they say, could potentially include thousands of industrial, pharmaceutical and chemical toxins and carcinogens.
"This sludge belongs in a hazardous waste dump," said Ronnie Cummins, the group's national director, before he poured some of the compost on carefully laid out plastic sheeting at the steps of San Francisco City Hall recenty.
In San Francisco, a utility spokesman said that federally mandated testing shows that the compost it distributes to the gardens has far lower levels of nine pollutants than the Environmental Protection Agency deems acceptable.
"We're in the business of protecting public health and the environment," Tyrone Jue said. "That's our mandate and our mission statement. That's what we do. If for even a minute we thought one of our activities was going against that mandate we would absolutely stop."
Several cities in California have bio-solid compost giveaways, including Los Angeles, San Diego, San Juan Capistrano, Santa Rosa, Fortuna, Carlsbad, and Calabasas, according to the Organic Consumers Association. Sewage or biosolids compost is also packaged and sold in major house and garden centers across the country.
A different category of fertilizer made from biosolids is used on millions of acres of land all over the United States to grow plants, according to the US Geological Survey. That fertilizer is not treated and heated to where it becomes compost and is not used for human food crops, although it is used for animal food crops.
The organic advocates group chose San Francisco for its protest because the city is so environmentally aware. "San Francisco as the greenest large city in the country should be the first to stop this," Mr. Cummins said.
The San Francisco Public Utilities Commission, which manages the city's sewage treatment, says that the 1 percent of the city's 80,000 tons of sewage that is converted into compost each year is treated and tested to the point of sterility.
But the problem, say groups like the Organic Consumers Association and the Center for Food Safety, is that the EPA requires testing for only nine metals, when there are potentially thousands of chemicals in the compost.
The EPA is evaluating if more pollutants need to be regulated and believes additional studies are needed, said Lauren Fondal, an environmental engineer for the EPA Office in San Francisco.
"I don't believe there have been any major studies of all these chemicals that we've begun detecting," she said.
There is no hard science that the compost is safe, the organic groups say, while there is anecdotal evidence that it is not.
In 2008, for example, a federal judge in Georgia ruled in favor of farmers who sued the United States Department of Agriculture when their cows became ill and died after eating silage grown on land upon which the compost had been applied.
US District Court Judge Anthony Alaimo concluded that "the EPA cannot assure the public that current land application practices are protective of human health and the environment."
Last fall, the Center for Food Safety, an advocacy group with offices in Washington, D.C. and San Francisco, tried to raise awareness of the biosolids issue when it petitioned San Francisco to end the compost giveaways.
The city made no promises. But the PUC stopped calling its free compost "organic." Under USDA rules, no sewage sludge compost, or farms that use biosolids, can be called "organic."
On Thursday, when the Minnesota-based members of the Organic Consumer Association held their "toxic sludge giveback" at City Hall, five protesters were flanked by about a dozen reporters and curious passers-by.
One of those watching was Mr. Jue of the PUC. He said that the city still considers the compost giveaways a pilot project. The city has held six giveaways since 2007. Jue said none are planned for the near future.
"Of course, if the public doesn't want it, we'll stop," he said.
Check out the Monitor’s main gardening page, which offers articles on many garden topics. Access all our blog posts here (keep scrolling down to read more), If you don't want to miss any of our gardening coverage, consider subscribing to the RSS feed of the gardening page and the RSS feed of Diggin' It. Do visit Gardening With the Monitor on Flickr. Take part in the discussions and get answers to your gardening questions. If you join the group (it’s free), you can upload your garden photos and enter our next contest.