Skip to main content

Vashon Island compost study

Learn how we're working with Zero Waste Vashon to explore options for processing organic waste on Vashon Island.

Project background

Over 35% of the waste landfilled each year in King County is organic material such as food and yard waste. Recycling organics creates many economic and environmental benefits including:

  • Reducing the extraction of natural resources.
  • Reducing carbon emissions from processing and shipping.
  • Reducing toxins and GHG in the environment from landfilling.

Organic material can also be turned into compost, a valuable natural soil-enhancement.

Currently, households and businesses on Vashon don't have curbside organics collection. Some compost their own organics or haul it to the Vashon Recycling and Transfer Station. The material collected at the transfer station is transported by Cedar Grove to their Maple Valley facility. 

We've partnered with Zero Waste Vashon to explore whether there's a way to process organic waste produced by Vashon, on Vashon. Our project considers the costs and benefits of an on-island compost processing facility. We'll determine whether to proceed based on a feasibility study and community survey.

Highlight Banner 1

Have questions or comments?

Project description 

In 2019 we partnered with Zero Waste Vashon, a volunteer group working to make Vashon a waste-to-resource community. Together, we are working to research creating a self-sustaining organics system on Vashon Island and help meet King County’s zero waste goal by 2030. 

We have taken several steps since the project began, including:

  • Holding scoping meetings
  • Consultant selection
  • Development of accurate feedstock numbers 
  • Reaching out to potential Island partners
  • Investigating facility siting needs
  • Survey consultant selection
  • Drafting survey content
  • Informing community about ongoing developments via newspaper, web, e-newsletter, and social media
  • Promotion of survey through signboards, newspaper articles, email newsletter and social media

Next steps 

King County continues to discuss and explore organics processing options on the Island with stakeholders and haulers.

We are currently working on:

  • Monitoring and responding to the new state organics law
    • The new law, House Bill 1799, was signed into law on March 25, 2022
    • This law requires that we provide organics collection options by 2027
  • Pursuing curbside collection options
  • Continuing with facility siting research
  • Identifying the best landfill location

As the project moves ahead, we'll continue to work with Zero Waste Vashon on community outreach. We will continue to provide opportunities for the public to share their thoughts.

Project schedule

Updated November 2022 (subject to change)

To date, several studies have been completed to determine the feasibility of this type of program on the island, as well as additional surveys and meetings with the community to share information and gain feedback on interest. We will continue to update this schedule as we take new actions in the future.

Date Action taken
2020 In 2020, we hired HDR to study small-scale organics management options on Vashon. Their work assessed project viability and did not include facility siting. They looked into:
  • Feedstock
  • Composting methods
  • Technologies
  • Estimated costs
  • End markets

The findings are now available in two reports. Final Phase 1 looks at feedstock sources, technologies, and high-level facility sizing. Final Phase 2 shows the estimated costs and a greenhouse gas analysis for the recommended approach.

Final Phase 1 (1250 KB) Final Phase 2 (215KB)

Early 2022

King County Solid Waste staff worked with Zero Waste Vashon and Comengage, a market research firm, to conduct a community survey in early 2022. The survey gathered input on organics collection, processing, and on-island compost use.

Vashon Island Solid Waste Survey (4MB)

June 2022

In June 2022, King County Solid Waste staff, Zero Waste Vashon representatives and consultants from HRD presented to Vashon residents about the results of the community survey and feasibility study for processing organics on the island. Staff detailed next steps that the County would take in it's analysis and decision making and answered questions from residents.

Vashon community meeting presentation (2MB)

Vashon community meeting minutes (200KB)

July 2022

In July 2022, an internal siting study was completed by King County Solid Waste staff. The report identified two locations adjacent to a closed landfill which may be suitable for use. Each site is greater than one acre in area and has a slope less than 5%. A third option combines the two sites into approximately 2.7 acres. This provides a much wider area for development.

A team of staff made up of King County Recycling and Engineering Services members met and discussed the report's recommendations. It was agreed that the report should be handed over to HDR for further technical analysis and recommendations.
Vashon facility site study (1384KB)

November 2022

In mid-November of 2022, the project consultant, employees from HDR, Zero Waste Vashon representatives and King County Solid Waste staff toured the proposed project site at the Vashon closed landfill.

The HDR consultants inspected and discussed the physical attributes of the site, landfill installations, the adjacent storm drain and pond, proximity issues with the transfer station and the neighboring property of the site.