Assumptions and Data Sources
SMART BET works by taking data entered by the user and estimating the greenhouse gas and cost savings from implementing SMART. The per capita disposal rate post-implementation is estimated at 500 lbs. per capita annually, so total post-implementation total disposal is dependent on population size only. Increases in recovery (recycling and composting) and source reduction are estimated by assuming that 65% of disposal decreases are due to recovery, and 35% are due to source reduction (based on a 2006 report by Skumatz Economic Research Associates, Pay as You Throw (PAYT) in the US: 2005 Update and Analyses). Cities that have current disposal rates at or below 500 lbs. per capita annually should be aware that this tool will provide results that show a net increase in disposal following SMART implementation, which is unlikely to be the case; therefore this tool is not recommended for such cities, as the results will be inaccurate.
Cost savings are estimated by multiplying the decrease in disposal by the landfill or combustor tip fee. Changes in recycling revenue are calculated by multiplying the increase in recovery by the recycling cost or revenue. The disposal and recycling cost changes are then summed.
Recycling cost should include only the direct cost of, or revenue from, recycling materials collected by the recycling program. For example, include what you pay the hauler, but don't include other recycling program costs such as advertising/marketing.
Disposal and recycling tonnages should include only municipal solid waste and not construction and demolition (C&D) debris (except to the extent that some residents may dispose of C&D-like materials in the municipal waste stream).
Greenhouse gas emissions are estimated by estimating the change in disposal, recovery, and source reduction for a particular material and multiplying that amount by a greenhouse gas emission factor for disposal, recovery, or source reduction, respectively.
Greenhouse gas emission factors in SMART BET are taken from the current version of EPA's Waste Reduction Model (WARM). The emissions estimates provided by SMART BET are intended to support voluntary GHG measurement and reporting initiatives and are not meant to be used for inventory purposes. The categories of waste used in SMART BET are more general than those used in WARM, and composition assumptions were used to assign WARM emission factors to SMART BET categories. The latest version of WARM is available at: http://www.epa.gov/climatechange/wycd/waste/calculators/Warm_home.html.
Specific material assumptions include:
- Metal is assumed to consist of aluminum and steel cans, according to their relative prevalence in the recovered materials stream according to the latest version of EPA’s report, Municipal Solid Waste in the US: 2007 Facts and Figures.
- Glass corresponds to the WARM category "Glass Bottles"
- Plastic is assumed to consist of HDPE, LDPE, and PET, according to their relative prevalence in the recovered materials stream according to the latest version of the Facts and Figures report.
- Paper is assumed to consist of 48% corrugated cardboard, 8% magazines, 24% newspaper, and 20% office paper.
- Wood corresponds to the WARM category “Dimensional Lumber.”
- Food scraps and yard trimmings correspond to the identical categories in WARM.
All averages used are national averages. The extent that your community’s waste-related demographics differ from the national average could alter the results.
The national average rate of recovery for landfill gas is assumed. Recovery comprises use for energy or flaring. The assumption is based on the US landfill gas collection characteristics that reflect the latest values from the US Greenhouse Gas Inventory.
A rate of 0.00014 metric tons CO2 equivalent per ton-mile is assumed for transportation of waste to a landfill or waste-to-energy facility, based on EPA's 1998 report Greenhouse Gas Emissions From the Management of Selected Materials. The default distance assumed is 20 miles.
The default percentages of materials in the disposal and recycling streams and the per capita disposal and recycling rates are based on data from the latest version of EPA's report, Municipal Solid Waste in the US: 2007 Facts and Figures.
The default percentages of materials in the disposal and recycling streams and the per capita disposal and recycling rates are based on data from the latest version of EPA's report, Municipal Solid Waste in the US: 2007 Facts and Figures available here: http://www.epa.gov/osw/nonhaz/municipal/msw99.htm.
The annual greenhouse gas emissions per average passenger vehicle are taken from the EPA's Online Equivalencies Calculator available here: http://www.epa.gov/cleanenergy/energy-resources/calculator.html.
The estimate of 500 pounds of waste disposed per capita per year following SMART implementation is an estimate based on findings from Kristen Brown of Waste Solutions in February 2009. Communities that implement SMART generally see an annual per capita disposal rate of 400-600 pounds. For estimation purposes, we use 500 pounds in this tool, but lower rates can and are achieved, often by increasing focus on organics collection, composting, and enhanced educational efforts. (Brown, Kristen. "The Tide Is Turning", 2008. Resource Recycling, p. 23.)