Skip to main content
Hands sift through compost ready for use


The basic rule for backyard composting: You can compost anything that was once alive... with caveats!

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 organic materials contain both C and N. The amount of carbon and nitrogen within a material is used to determine the carbon-to-nitrogen ratio (C:N). Finding a mix of greens and browns that is in balance can be important, with the optimum C:N for rapid composting about 30:1.

Materials with a favorable C:N offer the decomposer microorganisms a "complete meal".

"Greens" - Nitrogen Source

Materials that are a good source of nitrogen are called "greens." They generally have a C:N less than 30:1, are high in moisture, and decompose quickly. 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 considered "greens" because they are high in nitrogen.

"Browns" - Carbon Source

Materials high in carbon relative to nitrogen (i.e., C:N greater than 30:1), are called "browns." They generally are dry, decompose slowly, and, yes, are 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.

And then, The Caveats.

If there is a specific material that you are wondering about, visit our "Can I compost it?" page. Some people are concerned about problem 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 judgment about what materials can be added to the compost system.