Compounding the problem are persistent toxins from sprays used on forests (forest products make up a large share of commercial compost).The addition of sewage sediments and sludge — once freely labeled as such, now more stealthily named — as well as other waste water by-products harboring everything from heavy metals to prescription drugs show up in compost.
This practice grew as corporate farm operations, livestock growers, the timber industry and other businesses realized there was profit to be made from the waste of their activities.
As in Los Angeles, municipal compost operations started as an answer to rapidly filling landfill sites.
Since leaves and yard wastes comprise such a large percentage of landfill volume, as much as 30 per cent depending on the season, many cities began to see the value of composting their green waste and recycling (Los Angeles reached 50 percent by including food, paper products and other soluble wastes).
The city of Davis, California has had such a program since 1972.
Even early on in these programs, there were concerns about the quality of the compost produced as well as the harmful ingredients it might contain.