Yard Waste Composting

Turn your “waste” into a soil builder!

Photo of woman adding leaves to compost container
Adding leaves to her compost container.

Do Compost: Grass clippings, leaves, stalks, dead plants, twigs up to pencil diameter, and most weeds.

Don’t Compost: Weed seeds and invasive weeds like ivy (they resprout!), diseased plants, pet waste, clippings treated with weed or bug killers, or food waste. Instead, try the rodent-resistant methods described in Food Waste Composting.

Yard waste composting systems

These include simple piles, holding bins made of plastic, wood, or wire, and multiple bins where you move and turn the compost regularly to speed up the process. It takes 6 to12 months for soil creatures to change most yard waste into finished compost.

Secrets to success

For faster composting, keep your pile as moist as a wrung-out sponge. Chop up stalks and twigs. Mix “green” materials like grass clippings with “browns” like fall leaves and stalks.

Troubleshooting your compost pile

Symptom Cause Solution
Bad smells Pile too wet, no air, or contains food or pet waste Turn pile. Add dry stalks or leaves. Remove food.
Pile is dry Not enough water Turn pile. Add water to keep as moist as a sponge.
Moist enough, but slow composting Not enough “greens” Turn pile. Add “greens” like grass, plants, or manure
Slimy grass, ammonia smell Too much fresh grass in pile Leave clippings on lawn, instead of composting. Mix in brown leaves or stalks.
Pile shrunken, but looks un-decomposed Top too dry, finished compost is at bottom Harvest finished compost from bottom. Start new pile with un-composted material.

Print material

Composting at Home Guide (pdf) - Request a free copy.
Growing Healthy Soil Guide (pdf) - Has more information on using compost and mulches for a healthy, easy-care yard.
Compost Resource List (pdf) - Lists bin suppliers, tools, and more.
Composting Questions & Answers (pdf) - Answers to some common questions.

Links on other sites

Tilth Alliance - Offers classes in composting and organic gardening, and home-made compost bin plans.

Public Utilities

Andrew Lee, General Manager and CEO
Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000

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Seattle Public Utilities (SPU) is comprised of three major direct-service providing utilities: the Water Utility, the Drainage and Wastewater Utility, and the Solid Waste Utility.