Solid Waste Handling Permit Exemption for Anaerobic Digesters

What is the purpose of this exemption?
To allow operators of anaerobic digesters (AD) processing mostly dairy manure to accept pre-consumer food waste as a supplemental feedstock (up to 30 percent by volume) and operate without a local solid waste handling permit. Mixing pre-consumer food waste with the manure may result in greater methane production in the AD. Operating the AD under the conditions of the permit exemption allows for the use of the digestate at a dairy, transfer to a composting operation or other approved uses.
Who issues this exemption?
Department of Ecology
What activities are eligible for this exemption?
ADs that accept up to 30% (by volume) of off-farm pre-consumer food waste as digester feedstock (to be mixed with dairy manure) must apply for this permit exemption unless they are applying for the solid waste handling permit. ADs in compliance with the exempt conditions are limited in how they may use digestate solids and liquids. Use is allowed on the dairy as described in their updated nutrient management plan. The updated nutrient management plan must account for the added nutrients from the off-farm pre-consumer food waste. Solids may be transferred to a composting operation or other uses if compost testing standards are met. The exemption conditions are detailed in the law RCW 70.95.330 and WAC 173-350-250.
How much will this exemption cost?
There is no fee.
Where can I get the application for this exemption?
The application is called 'Anaerobic Digester Notice of Intent to Operate under Terms and Conditions for Solid Waste Permit Exemption per SSB5797' is online and can be accessed at
Do I need to include anything with my application?
The application requires several documents to be provided with the notice of intent to operate as an exempt facility, to allow Ecology to review the permit exemption status. These documents may include, but are not limited to: digester and storage design plans and specifications, digester operation plan, confirmation of updated dairy nutrient management plans, digestate transfer documentation, digestate management plans, or sampling plans. There is no application fee.
Is the decision on my exemption dependent on anything besides the information in my application?
Ecology's determination for the permit exemption may include:
  • Review of the notice of intent to operate and submitted documents, discussion of the application with the AD operator.
  • Confirmation from Washington State Department of Agriculture that the dairy has an updated nutrient management plan.
  • Compliance with other applicable local, state and federal laws.
  • A site inspection.
How long will it take to review my application?
Application review will be completed within 30 days.
Where do I submit my application?
You must submit the notification form to the region where the anaerobic digester is located. The form includes a map of where Ecology’s regional offices are located and the address to use for submitting the form to that office.
How long is my exemption valid?
The permit exemption is reviewed annually. Ecology will provide technical support for the AD when new organic waste feedstocks are considered. The AD operator should contact Ecology to confirm that the permit exemption allows new material. Lack of compliance with the exemption requirements may invalidate the exemption and a permit may be required.
What is the appeal process for the exemption?
This permit exemption may be appealed to the Pollution Control Hearings Board, as described in RCW 43.21B.
Notes / Comments:
Use of liquid and fiber digestate is subject to review by the Department of Ecology and the Washington Department of Agriculture. For details please refer to the Guidelines for Operating an Anaerobic Digester Exempted from Solid Waste Handling Permit at
Legal Authority:
Where can I get permitting assistance?
Web page URL:
Subject matter expert phone: (425) 649-7192
Subject matter expert email:
Department of Ecology
Northwest Regional Office
Dawn Marie Maurer
3190 - 160th Avenue SE
Bellevue, WA 98008-5453
Telephone: (425) 649-7000
Fax: (425) 649-7098
Triggering Questions:
  • Are you planning to operate a dairy manure anaerobic digester taking pre-consumer food waste as a supplemental feedstock?
* Permit information last updated 3/7/2022