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A Compost Refresher

So by now you know composting involves layering roughly equal parts carbon- and nitrogen-rich waste, but you might be unclear on exactly which of the two are found in a particular kind of waste. The quick guide below, based on some handy charts from the University of Illinois Extension, indicates which nutrient is provided by compostable materials, which to avoid, and how to handle the tricky bits.


Livestock Bedding (C+N)compost bin
Blood Meal (N)
Bone Meal (N)
Coffee and Tea Grounds (N)
Egg Shells (C)
Feathers (N)
Fruit (N)
Dried Garden Debris (C)
Fresh Garden Debris (N+C)
Veggie Scraps (N)
Straw (C)
Manure (N)
Lint (N)
Hair (N)

The Tricky Bits

Cardboard (C) – Slow to decompose; shred and soak before adding to compost pile
Corn Cobs (C) – Slow to decompose; chop into small pieces and mix with nitrogen-rich material
Diseased Plants (C) – Bake in sun until thoroughly dried, burn, or add to a hot compost pile reaching 131-140 degrees F
Chemically-Treated Lawn Clippings (C+N) – wait 2-3 weeks before using treated clippings or allow to compost for 12 months
Nut Shells (C) – Very slow to decompose; pulverize or use as roughage
Peat Moss (low in nutrients) – Slow to decompose and very absorbent; use in small quantity and mix well
Pine Debris (C) – Very acidic and slow to decompose; use sparingly in compost for vegetable application
Rhubarb (N) – Contains oxalic acid which deters beneficial microbes; use sparingly and mix well
Sawdust (C) – Can restrict aeration, add in thin layers and turn pile regularly
Sod N – Slow to decompose; compost roots-up on top of pile or separately under cardboard or a dark tarp
Walnut Leaves (C) – Can be toxic to plants; add in small quantities and avoid contact with other plants for 30-40 days
Weeds (C+N) – Roots and seeds can be hard to kill; bake in sun before adding to a hot pile for at least another week
Wood Ash (alkaline) – Can change pile chemistry and cause nutrient imbalance; do not add to top of pile and use in thin layers

To Avoid

Bones – Can attract pests and disease; consider making bone meal instead
Cat Litter – Clay, perfumes, and chemicals are not plant-friendly; switch to a natural litter, like wood chips, that you can compost
Dairy Products – Very slow to decompose and attract pests
Glossy Paper – May contain toxic inks
Human Feces – Requires very high temperatures to kill pathogens and parasites; should be composted carefully over a number of years before handling. See The Humanure Handbook if you want to learn more.

Photo Credit: Food scraps via Brooklyn Based, with a nice video on urban composting.

Margie is the founder of IG and is passionate about the therapeutic benefits of working with nature in the garden. She enjoys mangosteen, the rainy season, hammocks, and wild visitors in the garden.

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