During the course of everyday living, society generates a number of waste products including glass, plastic, paper, aluminum and other metal cans, yard clippings, wood, construction materials, etc. Household garbage (trash) and some commercial wastes (such as paper, cafeteria food wastes, etc.) are termed municipal solid waste (MSW) and are disposed of in MSW landfills. The construction of new buildings and structures along with the renovation, remodeling, and demolition of existing buildings and structures generates construction and demolition wastes (C&D) which are mostly disposed of in C&D landfills, although some (generally remodeling wastes from home do-it-yourself activities) are also disposed of in MSW landfills. The wood component of MSW and C&D wastes either alone, or combined with other organic components (refuse derived fuels) can be recovered and used for bioenergy and bioproducts. Additional urban biomass resources include the capture of gases produced by the decay of organic materials that have been landfilled, and biosolids generated in the wastewater treatment of sewage.
The wood component of MSW includes durable wood components (e.g., cabinets, furniture), packaging materials (e.g., pallets, crates) and some construction materials. Yard trimmings are mostly leaves and grass, but about 25% is wood. Estimated MSW wood quantities generated vary by study, ranging from 19 to 34 million green tons. Much of the wood waste is in a format not readily useable and must first be sorted and processed, is contaminated (e.g., painted, stained, pressure or chemically treated), or if clean, already collected and used to produce other products (e.g., mulch, recycled pallets, firewood, etc.). When these considerations are accounted for, estimated quantities available for bioenergy and bioproducts are significantly lower and higher priced than frequently assumed.
Wood is usually the largest component of construction and renovation wastes and is a small component of demolition wastes. Construction wastes are generally cleaner, less contaminated, and more easily sorted at the generation site than demolition wastes and are therefore more readily useful for bioenergy and bioproducts. Renovation wastes are intermediate to construction and demolition wastes. Estimated combined construction and renovation wood waste quantities range from 9 to 23 million green tons and estimated demolition wood waste quantities range from 23 to 28 million green tons, depending on study. As with MSW, when sorting and processing costs are considered, and contaminated materials excluded, available C&D wood wastes are significantly lower and higher price than assumed.
Landfill gas is the by-product of the decomposition of solid wastes in landfills. It is composed primarily of carbon dioxide and methane, which can be recovered and used for energy. As of 2005, there were 395 operational landfill energy projects in the U.S. and an additional 600 landfills are considered good candidates for projects.
An estimated 6.9 million dry tons of biosolids were generated in 1998 and projected 2010 quantities are 8.2 million dry tons. About 17% of biosolids are landfilled, while the remainder are recovered and used, often for land application.