FREE ORGANIC COMPOST for your garden in San Francisco! Come and get it! Except — it’s toxic sewage sludge from San Francisco and 8 other counties, “composted” at the Carlyle Group’s Synagro plant in Merced, contaminated with dioxins, flame retardants, and thousands of other chemical and biological contaminants. What goes down the drains ends up in the sludge, and then in your garden.