As the field of solid waste management becomes more developed and specialized, the categories into which solid waste is sorted and managed become more numerous. Yard waste—often called vegetative waste—includes leaves, grass clippings, tree trimmings, and other plant materials that are typically generated in outdoor residential settings. Depending on the season and the neighborhood, leaves may account for 5–30% of the total municipal solid waste stream, grass clippings may comprise 10–20%, and wood may form about 5–10%. Yard waste does not include food and animal wastes except possibly as impurities. Yard waste is usually perceived as cleanest type of solid waste, in contrast to household refuse or industrial and commercial trash.

Since yard waste is almost entirely vegetative in nature, it lends itself easily to composting. Composting is the natural breakdown of organic matter by microbes, in the presence of oxygen, to form a stable end product...