Compost

Composting is an important component of "closed loop" recycling. We set regulatory standards for composting facilities and compost quality and also provide technical assistance to local governments. By composting yard debris, food scraps, manure, and crop residues, waste can be turned into a valuable resource for farmers, orchardists, and gardeners, and reduce the production of greenhouse gases.

Using compost

Compost can be used in landscaping, new construction, and roadside applications. In Washington, there are best management practices for using compost when soil is disturbed on developed land.

  • Soils for Salmon — Learn about preserving site topsoil and vegetation, reducing compaction, and amending disturbed soils with compost to restore healthy soil functions.
  • Building Soil — Guidelines and resources for implementing soil quality and depth:  Best management practices for landscape designers, builders, planners, and inspectors to protect and restore soil.
  • Stormwater Management Manuals for Washington — Includes field inspection techniques, suppliers of compost, and soil testing laboratories, and specification language in APWA and CSI formats.

Composting at home

We conducted a recent study that showed that 50 percent of residential garbage in Washington could have been composted. Most of this material consisted of food (18 percent); and leaves, grass, or prunings (12 percent).

Vermicomposting
Vermicomposting is a great way to manage food waste at home! Vermicomposting is a process for converting food waste into a soil amendment by feeding the food waste to red wiggler (eisenia fetida) worms.  The worms live in a single level box or in a multi-level unit where they spend their time eating the food you feed them.  This process results in “castings” and in some cases, liquid “worm tea” that act as soil enhancers when added directly to gardens, potted plants, or to compost. 

The worms may be bought at retail outlets or obtained from local vermicomposters. Containers to house the worms can be made at home from wood or by using large plastic storage containers or more elaborate systems may be purchased on line.  Everything you need to know about the care and feeding of red wigglers can be found on-line.

Ecology composting publications

Herbicides

Some herbicides do not break down during the composting process. If contaminated compost is used, the herbicide may still be active and could impact growth of some sensitive plants. If you apply herbicides to your lawn, check the label to see whether you can compost the grass clippings. See the U.S. Composting Council's Persistent Herbicide FAQ page.

Compost data

From 2010 through 2015, more than a million tons of material was composted at commercial facilities in Washington. These charts show what materials were composted and how much was produced.

See a spreadsheet of this data.

 

See a spreadsheet of this data.

See a spreadsheet of this data.