Editor’s Note: Click here to watch the news clip of this story on CBS 5. For more information, please visit OCA’s Toxic Sludge and Organic Compost Information page.

SAN FRANCISCO (CBS 5) ― It’s called biosolids compost and its being given away by the San Francisco Public Utilities Commission for use in school and community gardens, and homes. But some activists are protesting the giveaways because that material is actually treated sewage sludge which experts say often contains toxins.

Student activities coordinator Roni Ben-David said she jumped at the chance to get free compost for the new organic garden she’s planning at San Francisco’s Jewish Community High School of the Bay:

“I drove down there and picked it up, picked up as much as I could,” she said.

And where did she get it? From a program run by San Francisco’s Public Utilities Commission that advertised a “high quality,” “non-toxic” “organic biosolids compost,” for use in local gardens.

But Ben-David noticed something different about this product. “This compost doesn’t smell great. It smelled a little stinky,” she recalled.

And now local activists say something else stinks. Because that free “organic” biosolids compost the San Francisco PUC began giving away in 2007, it’s actually the city’s sewage sludge – in other words, human wastes.

Not that human wastes can’t be good fertilizer, as the SFPUC’s Natalie Sierra points out.

“They have a lot of good nutrients, they also have energy value,” she said.

The problem is what often comes with it: toxins, from businesses, hospitals, heavy industry.

“Flame retardants, heavy metals, pharmaceuticals, steroids, hormones, PCB’s, all kinds of nasty stuff,” said Paige Tomaselli with the Center for Food Safety. Tomaselli said any of those toxins can be in that sludge, which is why her group filed a petition with the city to stop those giveaways.

“For people to be putting that in their garden, we think that’s ridiculous,” Tomaselli said.

Especially since the USDA doesn’t even allow the use of sewage sludge in organic food production. Yet gardeners like Roni Ben-David say they thought the product they were getting was organic and safe for growing food. “I just thought I was getting free, good organic compost,” she said.

“I think it’s very misleading to consumers and to farmers in the city,” said Tomaselli.

When CBS 5 Investigates asked the SFPUC’s Sierra she said, “We were not marketing it as organic compost.”