SAN FRANCISCO  – San Francisco wears its environmental consciousness like a green badge of honor. Residents separate and recycle their food scraps. Streets close to cars so people can walk and bike them. A city department even gives away “high-quality, nutrient-rich, organic bio-solids compost” to any and all takers.

But hold on there: A public interest and environmental advocacy group says San Francisco’s free compost, used by community, backyard and school gardens in the Bay Area, is processed sewage sludge – the product of anything flushed, poured or dumped into the wastewater system, including industrial, chemical and pharmaceutical toxins.

“This sludge belongs in a hazardous waste dump,” said Ronnie Cummins, national director of the Organic Consumers Association, before he poured some of the compost on carefully laid out plastic sheeting at the steps of San Francisco City Hall on Thursday.

The protest, he said, was the launch of an all-out campaign the organic foods movement is planning to wage against the use of bio-solids compost.

The San Francisco Public Utilities Commission, which manages the city’s sewage treatment, says 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.

San Francisco isn’t even the only California city to have bio-solid giveaways, according to the Organic Consumers Association. Los Angeles, San Diego, San Juan Capistrano, Santa Rosa, Fortuna, Carlsbad, and Calabasas do the same.

Not only that, sewage or bio-solids compost is packaged and sold in major house and garden centers across the country. And fertilizer made from bio-solids is used on millions of acres of land throughout the U.S. where plants are grown, according to a report by the U.S. Geological Survey. That fertilizer is not treated and heated to the point where it becomes compost and is not used for human food crops, though it is used for animal food crops.