Master Composters know that the secret to fast, hot composting is a balanced recipe of browns and greens. Different plant materials will impart different physical or chemical qualities to the composting process, which is why we often refer to the plants we compost as browns or greens.
Browns are dry, woody plant materials – think dry leaves, twigs, pine cones, etc. Browns become a source of carbon for soil microbes, and since most biological organisms need 25x more Carbon than Nitrogen, Brown materials should make up 3/4 of the materials in your compost pile.
Greens are more fresh, wet plant wastes – think fresh leaves, grass clippings, weeds, food scraps, etc. Greens become a source of nitrogen for soil microbes, and greens should really only make up about 1/4 of the pile by volume.
A good rule of thumb is to always mix 3 parts ‘browns’ to every 1 part ‘greens’. For practicality, think of this ratio on a volume basis, not by weight.