What Can Be Composted?

Greens and Browns

Backyard Composting is primarily a biological process so you must feed your microorganisms to keep them happy. Microbes need both carbon (C) and nitrogen (N), food sources to function. All materials contain both C and N. The ratio of carbon to nitrogen within a material is called the carbon to nitrogen ratio (C:N).

Materials with favorable proportions of carbon and nitrogen (C:N) offer the decomposer microorganisms a "complete meal".

"Greens" - Nitrogen Sources - Materials that are a good source of nitrogen are called "Greens" and are characterized as having a low C:N ratio (C:N ratio less than 30:1) and are generally high in moisure and fast to decompose. Examples of "greens" include manure, inorganic fertilizer, vegetable kitchen scraps, green leaves, and grass clippings.  Not all "greens" are green in color.  For example, coffee grounds are a nitrogen source.

"Browns" - Carbon Source -  Materials that are high in carbon relative to nitrogen (i.e., C:N greater than 30:1), are called "Browns", and are generally dry and slow to decompose.  They are generally brownish or darker in color.  Examples of "browns" include: straw, leaves, chipped branches and tree trimmings, paper, and sawdust. Browns decompose at low temperatures unless combined with a source of nitrogen.

Finding a mix of greens and browns that is in balance can be important. The optimum C:N ratio for rapid composting is about 30:1.

"Greens and Browns"

If there is a specific material that you are wondering about, go to "Can I compost it?" Some people are concerned about problematic materials such as possible residues from pesticides, herbicides, weeds, and/or plant diseases.  The most conservative response to these concerns is to avoid adding these materials to the composting system.  However, many people who compost at home use their own judgement about what materials can be added to the compost system.

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