What to Put in Your Compost Pile

Understanding the Carbon to Nitrogen Ratio (C:N)

Fungal-dominated composts begin with materials that have a higher carbon to nitrogen ratio, and bacterial-dominated composts contain materials with a lower C:N ratio. This ratio is sometimes referred to as the “brown to green ratio” because generally materials that are high in carbon are brown, woody, and/or dried and materials that are high in nitrogen are green and/or fresh. Therefore, fungal-dominated composts generally contain more brown materials, and bacterial-dominated composts generally contain more green materials.

Note: The most efficient decomposition occurs when the C:N ratio is between 25-30:1. Too much carbon (a high C:N ratio) causes decomposition to slow down and too much nitrogen (a low C:N ratio) can cause foul odors.

Common Sources of Carbon and Nitrogen in Compost

Carbon-Containing Ingredients (Brown) Nitrogen-Containing Ingredients (Green)
Dried Grass Clippings Fresh Grass Clippings
Straw, Old Hay Alfalfa, Fresh Hay
Wood Chips, Wood Ashes, Sawdust Seaweed
Dried Leaves & Pine Needles Kitchen Scraps, Coffee Grounds, Tea Bags
Black & White Newspaper Blood Meal
Paper Towels, Tissue Paper Manure
Shredded Cardboard Garden Waste

Materials to AVOID using in your compost pile include:  large amounts of dried leaves and pine needles because they break down slowly and can affect pH levels, human and pet waste, waxed cardboard, colored newspaper, grease & oil, meat, dairy, weed seeds, and plastic.

Helpful tools:
Compost Mix Calculator – Determine the C:N ratio of up to four materials in a mix, from Klickitat County, Washington.
List of C:N Ratios for Compostable Materials – View this extensive list generated by the Oregon Biodynamics Group.