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Sonoma Public Infrastructure

Proposed Sonoma County Compost Facility

Image of a building on Slusser Road in Santa Rosa

Proposed Compost Facility at 5200 Slusser Road, Windsor

Sonoma County is considering a new compost facility at 5200 Slusser Road in Windsor, just west of the Charles M. Schulz - Sonoma County Airport. The facility would process household food scraps, yard trimmings, wood waste, and food-soiled paper collected in residential green bins and turn them into compost for local residents, farmers, and businesses.

The proposed facility could process up to 70,000 tons of material each year, or about 80% of the residential green bin material generated annually in Sonoma County.

Why Is This Project Needed?

State law requires organics recycling

California law requires residents and businesses to separate food scraps and yard waste into green bins. Recycling these materials helps reduce methane emissions from landfills.

Most of our compost leaves the County

Since 2015, nearly all of Sonoma County’s green bin material has been hauled to facilities outside the county, including to composting facilities in Novato and Ukiah. This increases truck traffic and greenhouse gas emissions, limits local access to compost, and leaves the County dependent on facilities outside the region.

Why a Local Compost Facility

Today, this means
  • More truck traffic
  • More greenhouse gas emissions
  • Less local access to compost
  • Dependence on facilities outside the region
Creating a local compost facility allows us to:
  • Reduce transporation impacts
  • Keep materials and finished compost local
  • Strengthen regional composting capacity
  • Support Sonoma County's 5-year Strategic Plan
Where Would the Facility Be Located?

The proposed site is located at 5200 Slusser Road in Windsor on County-owned property, just to the west of the Charles M. Schulz - Sonoma County Airport. A portion of the proposed site was a former landfill that closed in 1971 and is now vacant and fenced.

A 2022 feasibility study found that about 15 acres of the former landfill could support composting operations. Additional buildings and infrastructure would be located immediately adjacent on County-owned land.

What Would the Facility Do?

The facility would:

  • Receive residential green bin materials
  • Process up to 70,000 tons per year of green materials
  • Produce about 130,000 cubic yards of finished compost annually
  • Make compost available locally, including public sales on Saturdays

The facility would not accept self-hauled material from the public.

How Would Composting Work?

Proposed Composting System
  1. Receive materials inside an enclosed building.
  2. Screen and mix materials to prepare them for composting.
  3. Place materials in long rows over aeration pipes.
  4. Cover rows with a breathable GORE® fabric membrane.
  5. Allow naturally occurring microbes to break down the material.
  6. Screen and prepare finished compost for sale.
  7. Finished compost stored under cover.

California map highlighting locations using GORE cover system

Composting System Benefits
  • Control odors
  • Reduce water use
  • Contain stormwater and leachate (water that contacts composting materials)
  • Speed up composting

Project Status

Click image to see enlarged view.

  • Facility layout
  • Traffic circulation
  • Composting system configuration
  • Environmental protection features

Design rendering of proposed compost facility close-up

Click image to see enlarged view.

The conceptual renderings shown above represent the project at the 30% design milestone and are intended to illustrate the overall vision for the proposed facility. The current design includes the proposed facility layout, traffic circulation, composting system, and environmental protection features. Design details may continue to evolve as the project progresses through environmental review and future design phases.

Recent Community Outreach

Sonoma Public Infrastructure hosted two community open houses in May 2026 to share information about the proposed Sonoma County Compost Facility Project and answer questions from residents. The project has now reached 30 percent design and is moving into environmental review, an important step in the planning process.

The California Environmental Quality Act (CEQA) review process will include public notice, opportunities for public input, release of environmental documents for review, and public meetings before the Board of Supervisors. While major project milestones and design updates are not anticipated until early 2027, the County remains committed to sharing information as it becomes available and encourages community members to submit questions or comments to the project team and sign up for project updates.

No final decision has been made on the project, and public input will continue to be an important part of the process.

Learn More

Frequently Asked Questions

Available Documents:

Additional documents will be posted as the project progresses.

Contact Us

We know we have a strong composting community in Sonoma County and we want to hear from you!

Email us at SPI-Compost@sonomacounty.gov with your questions or to ask to join our emailed community updates list.