San Francisco Department of the Environment

What happens during composting and why do we do it?

When Recology picks up the green compost bin, the compostable materials are taken to Jepson Prairie Organics in Vacaville, California where the curbside material is transformed into nutrient-rich, organic compost for local farms. 

Composting Process

Operations at Jepson Prairie Organics in Vacaville, CA. 

When compostable materials arrive at Jepson Prairie Organics, they are:

  1. Sorted for plastics and other non-compostable items, otherwise known as "contaminants"

  2. Compostables are shredded to facilitate the naturally-occurring microbes in breaking down materials

  3. The shredded material is laid out in rows and covered to retain heat, so the naturally-occurring microbes can process the organic matter and destroy harmful pathogens. The difference between your household compost pile and commercial composting facilities (as some home composters know - meat, bones, and dairy cannot be composted at home because backyard compost piles do not reach temperatures high enough to kill pathogens).

  4. After 45 days, the transformation is complete and nutrient-rich compost can be sold to local farms to grow produce and protect the soil. 

Why We Compost

 

Nigel Walker form Eatwell Farm in Dixon, CA shows off his organically grown heirloom tomatoes using organic compost from food scraps collected in San Francisco. 

Participating in a compost program helps prevent sending valuable materials to the landfill, as well as provide a nutrients and other benefits to the land to which it is applied.

Food scraps and other compostables sent to the landfill break down in an anaerobic environment and create methane gas, which is 25 times worse than carbon dioxide as a harmful greenhouse gas.

Compost used on farmland reduces the need for artificial, chemical-heavy fertilizers. In addition, compost improves soil structure and density which provide a better environment for plant roots and produce to grow, increases moisture in soil which reduces erosion, improves and stabilizes soil pH, and supplies a variety of nutrients. The economic benefits associated with compost involve the reduction in the need for water, fertilizer, and pesticides.