Anaerobic digestion is the process through which organic materials break down in the absence of oxygen. Composting is the break down of the material with oxygen.
Anaerobic digestion produces gas - sometimes called biogas - primarily composed of methane and carbon dioxide, which occurs naturally in decomposition. By controlling the process and collecting the biogas, it can be used for energy. If it’s not collected, biogas escapes into the atmosphere and contributes to climate change.
Anaerobic digesters have been around for hundreds of years and come in all shapes and sizes. Most are designed to process organic materials, extract energy in the form of biogas, and produce by-products that can be land applied to improve soil health. Anaerobic digestion can reduce harmful pathogens in waste, making it safer to use as a beneficial soil amendment.
We provide support for the development and use of anaerobic digestion technologies. We also assist local governments in overseeing anaerobic digesters and conducting inspections.
Anaerobic digester regulations
- Washington’s Solid Waste Handling Standards includes permitting requirements for solid waste anaerobic digesters.
- See specific regulations at Chapter 70A.205.290 RCW.
- For solid waste permit information and forms, see our Solid waste permits web page.
Solid waste permit exemption for dairies
Under certain conditions Washington law exempts dairy manure anaerobic digesters from solid waste permitting. Permit exemption conditions are detailed in WAC 173-350-250.