Food safety groups complain that the San Francisco Public Utilities Commission has until recently been dumping its crap in the backyards and gardens of any residents who unwittingly asked for it.

The city calls this crap “biosolids compost,” and for Mayor Gavin Newsom and the SFPUC, it seemed like a green dream come true. But it turns out that putting processed human excrement into people’s vegetable gardens might not be the elegant – if somewhat gross – reuse strategy it once seemed to be.

The vexing sewage sludge left over after treatment and separation of the city’s wastewater was being treated, combined with woodchips and paper waste, and labeled compost so it could, according to the SFPUC’s Web site, “provide essential plant nutrients, improve soil structure, enhance moisture retention, and reduce soil erosion.” Not bad for the ultimate human waste product.

The problem, say groups including the Center for Food Safety and Organic Consumers Association, is that the SFPUC’s compost contains a host of other toxins and hazardous materials not necessarily originating with what the city’s granola-munching denizens flush down the toilet. In fact, a January 2009 Environmental Protection Agency study of sewage sludge from 74 treatment plants found, in nearly every sample, “28 metals, four polycyclic aromatic hydrocarbons, two semi-volatiles, 11 flame retardants, 72 pharmaceuticals, and 25 steroids and hormones.” Yikes.

“You name it, it’s in there,” John Mayer, said spokesperson for the Organic Consumers Association. The compost “is hazardous waste, and it’s absurd to claim that it’s safe to consume. No matter what the sludge processing industry claims, it is by definition dangerous.” The EPA report would certainly seem to support Mayer’s claim, except that it expressly stops short of doing just that, stating that the results “do not imply that the concentrations for any [substance] are of particular concern to EPA.”