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bioweb.sungrant.org » Technical » Biomass Resources » Urban Biomass Resources » Municipal Solid Waste

Municipal Solid Waste	Printer Friendly

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. A number of these products are recycled, but the majority are disposed of in landfills. Some of these materials, most notably wood, could be recovered and used for bioenergy and bioproducts. Waste material generation is not limited to cities, but is most concentrated there due to the high density of population, thus these wastes are often referred to as urban wastes - even though they can include wastes generated in rural and non-metropolitan areas as well.    Most ordinary household waste (i.e., garbage or trash) is classified as municipal solid waste (MSW) and is disposed of in MSW landfills. The wood component of MSW consists of packaging materials such as wooden crates and pallets, and durable materials such as furniture. Yard trimmings are mostly grass clippings and leaves, but about 25% is wood obtained from pruning and brush removal (EPA, 2000).       Data on the quantities of wood contained in MSW is limited and of variable quality. Each state has its own method of collecting data and definition of what materials are contained in MSW. Construction and demolition wastes, as well as other non-MSW wastes, are sometimes reported as MSW waste. Tons of material landfilled in-state and used in waste-to-energy facilities are regulated and thus relatively consistent from year to year. However, recycling facilities and facilities that compost yard trimmings are often not required to report the amount of material they use. Additionally, waste generated in one state and exported to another state for disposal is not always well tracked (BioCycle, 2006). State and local data can be found on some state government web sites, but the availability and quality of data varies substantially by state.         The Environmental Protection Agency (EPA, 2006) estimated that in 2005, 245.7 million tons of municipal solid waste (4.54 lbs/person/day) was generated (table 1). About 32% was recycled or commercially composted (backyard composting not included). Wood and yard trimmings represented 5.7% and 13.1% of the total (by weight), respectively. The recovery rate for wood was low (9.4%), but nearly 62% of the yard trimmings were recovered, mainly to produce compost.                     McKeever (2003) estimated that 18.9 million tons of wood wastes were contained in MSW and yard trimmings in 2001. Of these quantities, he estimated that 6.2 million tons of wood could be available for bioenergy use. Falk and McKeever (2004) estimated that 12 million metric tons of durable and packaging wood waste, and 14.8 million metric tons of wood yard trimmings were generated in 2002; 5.5 and 3.2 million metric tons of durable/ packaging material and wood yard trim, respectively, were available for bioenergy use. Neither study provided estimates of wood waste prices, and both limit the quantities of available wood wastes to those that are not currently recovered and recycled. The estimated quantities are based on EPA data for total MSW generated and percent of MSW that is yard trimmings and wood, and corrects for recycling rates and quantities of insufficient quality to use for bioenergy.   BioCycle magazine has collected state data (mostly MSW and some limited construction and demolition waste) since 1989, via its State of the Garbage Survey of state solid waste management agencies (BioCycle, 2006). Data includes total quantities of MSW generated, as well as data on recovery and recycling operations (including wood recycling and composting of yard trimmings), but does not provide MSW compositional data. Araman et al. (1997) surveyed MSW landfills and collected wood disposal and recycling data, primarily for pallets, but including some other wood information for 1995. The data is somewhat dated, but provides a regional (rather than a single national) breakdown of the amount of wood contained in MSW and the recycling rates. Some local and regional quantity studies are also available, such as the Triangle J study in North Carolina (Buehlmann, 2001).       Few studies attempt to estimate MSW wood waste prices. The Antares Group (1999) estimated that 10.1 million wet tons of yard trim and 6.8 million wet tons of other MSW wood wastes are available annually at delivered prices of less than $4.00/Btu. Wiltsee (1998) surveyed waste generation rates in 30 U.S. metropolitan areas and extrapolated the data to the remainder of the U.S.  He estimated that up to 60 million tons of wood wastes could be available at prices of less than $0/ton, based on tipping fees. Walsh et al. (2000) estimated that 36.8 million dry tons of urban wood wastes (combined MSW, construction/ demolition, and yard trimmings) could be available at a delivered price of $30/dt.   Walsh (2006) estimated county level supply curves for MSW wood wastes (packaging, crates) and MSW yard trim for the years 2005, 2010, 2015, 2020, and 2025 using a number of national, state, and local studies that provided MSW quantity and compositional data. The author estimates that 26.1 million dry tons of wood wastes are generated annually in MSW and yard trim. Projections of future quantities are based on population growth. Unlike most studies that assume recycled wood materials are unavailable for bioenergy use, Walsh estimates prices that could be paid to attract wood resources away from their current uses to bioenergy uses. The estimated prices are a function of sorting costs (mixed and source separated by waste stream type), net tipping fees (fee received, minus post-sorting disposal costs for contaminated wood), the value of other products resulting from sorting (i.e., metal, glass, plastic), and a rough approximation of the profitability of existing uses of the wood material. The analysis has significant data and methodology limitations and represents a crude approximation of potential MSW wood supplies. Estimated supplies of wood wastes for several price levels are contained in table 2. Wood wastes are ubiquitous, with small quantities available in nearly every county and greatest concentration near highly populated areas.

References
Antares Group, Biomass Residue Supply Curves for the United States, June 1999. Araman, Phil, Robert J. Bush, and Vijay S. Reddy, Municipal Solid Waste Landfills and Wood Pallets–What’s Happening in the United States, Pallet Enterprise, February 1997, pp. 50-56. BioCycle, April, 2006, 15th State of the Garbage Survey, JG Press, Inc., pp. 26-43. Buehlmann, Urs, and Judy Kincaid, Scrap Wood Availability in the Triangle J Region (North Carolina), April 2001. Falk, Robert H. and David B. McKeever, April 2004, Recovering wood for reuse and recycling: a United States perspective, in Proceedings of Management of Recovered Wood Recycling, Bioenergy and Other Options, Cristos Gallis (editor), University Studio Press, Thessaloniki, pp. 29-40. McKeever, David B., Taking Inventory of Woody Residuals, BioCycle, July 2003. U.S. Environmental Protection Agency, Office of Solid Waste Management, Municipal Solid Waste in the United States—2005 Facts and Figures, EPA530-R-06-011, October 2006. U.S. Environmental Protection Agency, Municipal Solid Waste in the United States: 2000 Facts and Figures. Walsh, Marie E., Robert L. Perlack, Anthony Turhollow, Daniel de la Torre Ugarte, Denny A. Becker, Robin L. Graham, Stephen E. Slinsky, and Daryll E. Ray, Biomass Feedstock Availability in the United States, Unpublished Oak Ridge National Laboratory Report, January, 2000. Walsh, Marie E., July 2006, U.S. Cellulosic Biomass Feedstock Supplies and Distribution, paper presented at Energy From Agriculture: New Technologies, Innovative Programs and Success Stories Conference, Farm Foundation, St. Louis, Mo., December 14-15, 2005.  Wiltsee, George, Urban Wood Waste Resource Assessment, November, 1998, NREL/SR-570-25918.