San Francisco’s Composting Revolution: Turning Food Waste into Farm Fuel

Each year, food scraps pile up in America's landfills, producing methane—a greenhouse gas far more potent than carbon dioxide in the short term. This wasted organic material could instead be turned into compost, an invaluable resource for farms looking to boost soil health, reduce or eliminate chemical fertilizer, and improve resilience in the face of climate uncertainty. San Francisco’s groundbreaking composting program offers a clear blueprint for how local governments can tackle food waste and mitigate climate change, establishing a local circular economy that feeds productive farmland rather than landfills.[1]

A Model for Municipal Composting

San Francisco pioneered household organic waste collection in 1996, long before widespread discussions about climate resilience and the circular economy. By 2009, the city made composting mandatory through the San Francisco Mandatory Recycling and Composting Ordinance (No. 100-09), requiring residents to separate recyclables, compostables, and trash.[2] This legal mandate transformed composting from an optional green habit into a citywide standard. As a result, more than 500 tons of organic waste are diverted from landfills each day, generating nutrient-rich compost for local farmers and significantly reducing methane emissions.[3]

How San Francisco’s Closed-Loop System Works

The success of the program relies on a coordinated four-step process involving residents, policy, technology, and farming partners.

1. Collection and Separation

San Francisco’s three-bin system, with its distinctive bright green bin dedicated to compost, makes it easy for residents to sort waste at home.[4]  The city reinforces this with extensive communication campaigns, including educational materials translated into twenty languages and door-to-door education efforts, which help ensure high rates of compliance.[5]

2. Financial Incentives and Accessibility

Policy nudges encourage participation and promote equity:

• Differential Pricing: The city charges residents more for trash pick-up than for compost collection, financially incentivizing households to maximize use of the green bin.[6]
• Low-Income Discounts: Low-income residents can apply for a 25% fee reduction, making the program more equitable and inclusive.[7] These measures collectively boost composting rates across different socioeconomic groups.

3. Processing and Advanced Technology

San Francisco partners with the company Recology to haul and process the city's organic waste.[8] Recology turns municipal organic waste into a certified organic compost[9] using advanced technologies to separate out non-compostable materials like plastics from the compost.[10]

4. Distribution to Farms

Farmers—particularly those in nearby counties—buy Recology’s compost to use as an organic fertilizer. Because transporting compost long distances can be expensive, local farmers benefit most. By closing this loop, food scraps from San Francisco ultimately nourish the soils that grow the region's produce.

Key Challenges and Lessons for Other Localities

The successful transition to a closed-loop system highlights both the critical role of policy and the operational necessity of advanced infrastructure.

Technology and Contamination Control

For cities that want to compost municipal solid waste and sell the resulting product to local farmers, technology to remove contaminants is crucial. Contamination of compost is often cited as a reason why farmers are reluctant to apply compost derived from municipal solid waste.[11],[12] Recology’s use of multiple technologies to remove plastics and other contaminants helps increase farmer uptake of the product while improving the product's environmental impact.

Economic Viability and Scale

Economies of scale and the sheer size of San Francisco’s waste program facilitate the operation of a large facility with more advanced technologies. Smaller cities or towns may not generate enough waste to justify such investment, but they could explore options to transport waste to larger facilities that collect from multiple municipalities, an approach currently being explored in California due to a state-wide composting mandate.[13] Long-distance hauling is unlikely to eliminate the greenhouse gas benefits of the practice, though transportation cost is a constraining factor.[14]

San Francisco’s compost is economically viable for farmers due to two features:

1. Proximity: The composting facility is located near farms, orchards, and vineyards, which cuts down on transportation costs.[15],[16]
2. Certified Organic: The resulting compost is a certified organic input, enabling organic farmers to use the product. The organic label may increase demand by boosting the product's value to farmers who often view cost as a deterrent to using compost.[17]

Policy Design and Equitable Access

San Francisco's policy design demonstrates how multiple complementary approaches can drive program success and high participation. The combination of infrastructure support (three-bin system), extensive education (multilingual materials and door-to-door outreach), and financial incentives (differential pricing) creates multiple pathways for resident engagement. Importantly, the city’s attention to equity—through measures like the 25% low-income discount and translation of materials into twenty languages—helps ensure the program serves all residents. Other cities implementing composting programs should consider how their policy design can similarly address common barriers while ensuring equitable access.

Key Legal Instrument: Mandatory Recycling and Composting Ordinance (No. 100-09)

Under this city law, which underpins the entire system:[18]

"All persons in San Francisco must source separate their refuse into recyclables, compostables and trash, and place each type of refuse in a separate container."

References

[1] "San Francisco Celebrates Major Climate Success With 25 Years of Composting | San Francisco Environment Department (SFE)," San Francisco Environment Department, October 20, 2021. https://www.sfenvironment.org/press/san-francisco-celebrates-major-climate-success-25-years-composting.

[2] "Mandatory Recycling and Composting," Pub. L. No. 100-09, San Francisco Environment Code (2009), https://www.sfenvironment.org/files/policy/sfe_zw_sf_mandatory_recycling_composting_ord_100-09.pdf.

[3] "San Francisco Celebrates Major Climate Success With 25 Years of Composting | San Francisco Environment Department (SFE)," San Francisco Environment Department, October 20, 2021. https://www.sfenvironment.org/press/san-francisco-celebrates-major-climate-success-25-years-composting.

[4] Yerina Mugica, Andrea Spacht, and Alice Henly, "San Francisco Composting from Fork to Farm and Back." Natural Resources Defense Council, November 2017. https://www.nrdc.org/sites/default/files/food-matters-san-francisco-composting-cs.pdf.

[5] Yerina Mugica, Andrea Spacht, and Alice Henly, "San Francisco Composting from Fork to Farm and Back." Natural Resources Defense Council, November 2017. https://www.nrdc.org/sites/default/files/food-matters-san-francisco-composting-cs.pdf.

[6] Yerina Mugica, Andrea Spacht, and Alice Henly, "San Francisco Composting from Fork to Farm and Back." Natural Resources Defense Council, November 2017. https://www.nrdc.org/sites/default/files/food-matters-san-francisco-composting-cs.pdf.

[7] Yerina Mugica, Andrea Spacht, and Alice Henly, "San Francisco Composting from Fork to Farm and Back." Natural Resources Defense Council, November 2017. https://www.nrdc.org/sites/default/files/food-matters-san-francisco-composting-cs.pdf.

[8] Yerina Mugica, Andrea Spacht, and Alice Henly, "San Francisco Composting from Fork to Farm and Back." Natural Resources Defense Council, November 2017. https://www.nrdc.org/sites/default/files/food-matters-san-francisco-composting-cs.pdf.

[9] "Compost," Recology, accessed February 11, 2025, https://www.recology.com/organics/products/compost/.

[10] "2023 Sustainability Report" (Recology), accessed February 11, 2025. https://www.recology.com/pdfviewer/2023-sustainability-report/.

[11] J. C. Hargreaves, M. S. Adl, and P. R. Warman, "A Review of the Use of Composted Municipal Solid Waste in Agriculture," Agriculture, Ecosystems & Environment 123, no. 1 (January 1, 2008): 1-14, https://doi.org/10.1016/j.agee.2007.07.004

[12] Karen Hills et al., "Differentiating the Value and Cost of Compost Across Likely Farm Use Scenarios in Western Washington." Washington State University, September 2019. https://wpcdn.web.wsu.edu/cahnrs/uploads/sites/44/Differentiating-the-Value-and-Cost-of-Compost-v.4Nov2019.pdf.

[13] Brendan P. Harrison et al., "Quantifying the Farmland Application of Compost to Help Meet California's Organic Waste Diversion Law.," Environmental Science & Technology 54, no. 7 (April 7, 2020): 4545-53, https://doi.org/10.1021/acs.est.9b05377.

[14] Brendan P. Harrison et al., "Quantifying the Farmland Application of Compost to Help Meet California's Organic Waste Diversion Law.," Environmental Science & Technology 54, no. 7 (April 7, 2020): 4545-53, https://doi.org/10.1021/acs.est.9b05377.

[15] "Compost," Recology, accessed February 11, 2025, https://www.recology.com/organics/products/compost/.

[16] Mohammad Rahmani, Alan W Hodges, and Clyde F Kiker, "Compost Users' Attitudes Toward Compost Application In Florida," Compost Science & Utilization 12, no. 1 (Winter 2004): 55-60

[17] Karen Hills et al., "Differentiating the Value and Cost of Compost Across Likely Farm Use Scenarios in Western Washington." Washington State University, September 2019. https://wpcdn.web.wsu.edu/cahnrs/uploads/sites/44/Differentiating-the-Value-and-Cost-of-Compost-v.4Nov2019.pdf.

[18] "Mandatory Recycling and Composting," Pub. L. No. 100-09, San Francisco Environment Code (2009), https://www.sfenvironment.org/files/policy/sfe_zw_sf_mandatory_recycling_composting_ord_100-09.pdf.