The San Francisco Mandatory Recycling and Composting Ordinance is a local municipal ordinance requiring all persons located in San Francisco to separate their recyclables, compostables and landfilled trash and to participate in recycling and composting programs. Passed by the San Francisco Board of Supervisors in 2009, it became the first local municipal ordinance in the United States to universally require source separation of all organic material, including food residuals.

Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by decomposing plant and food waste, recycling organic materials, and manure. The resulting mixture is rich in plant nutrients and beneficial organisms, such as bacteria, protozoa, nematodes, and fungi. Compost improves soil fertility in gardens, landscaping, horticulture, urban agriculture, and organic farming, reducing dependency on commercial chemical fertilizers. The benefits of compost include providing nutrients to crops as fertilizer, acting as a soil conditioner, increasing the humus or humic acid contents of the soil, and introducing beneficial microbes that help to suppress pathogens in the soil and reduce soil-borne diseases.