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Basic Information about the Waste Reduction Model (WARM)

EPA created the Waste Reduction Model (WARM) to help solid waste planners and organizations track and voluntarily report greenhouse gas (GHG) emissions reductions, energy savings and economic impacts from several different waste management practices.

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What is WARM?

WARM is a tool that calculates and totals the GHG emissions, energy savings and economic impacts of baseline and alternative waste management practices, including source reduction, recycling, combustion, composting, anaerobic digestion and landfilling. The model calculates emissions, energy units and economic factors across a wide range of material types commonly found in municipal solid waste in the following categories:

  • Metric tons of carbon dioxide equivalent (MTCO2E),
  • Energy units (million British Thermal Unit - BTU),
  • Labor hours,
  • Wages ($), and
  • Taxes ($).

WARM is currently available as a tool based on a database developed in open life cycle assessment (openLCA) software, with versions available for both Windows and Macintosh users. WARM is also available as a downloadable Microsoft Excel spreadsheet.

GHG savings are calculated by comparing the emissions associated with managing materials under an alternative scenario with the emissions associated with the user’s baseline scenario (i.e., current practices), as opposed to simply multiplying the quantity of materials managed by an emission factor. For example, the GHG savings of recycling one (1) short ton (standard U.S. ton) of aluminum cans instead of landfilling them would be calculated as follows:

(1 short ton × -9.13 MTCO2E/short ton) - (1 short ton × 0.02 MTCO2E/short ton) = -9.15 MTCO2E

WARM is periodically updated as new information becomes available and new material types are added. Users may refer to the model history to better understand the differences among various versions of WARM. WARM was last updated in May 2019.

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Who Should Use WARM?

WARM helps solid waste planners and organizations track and voluntarily report greenhouse gas (GHG) emissions reductions, energy savings and economic impacts from six different waste management practices including source reduction, recycling, composting, anaerobic digestion, combustion and landfilling. WARM can be used by individuals and organizations ranging from state and local governments, solid waste planners, students, small businesses, and other organizations interested in the GHG, energy and economic impacts frm materials management decisions.

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What Materials Are in WARM?

WARM now recognizes 60 material types, which are presented in the table below. Their emission, energy and economic factors are available for viewing in units of metric tons of carbon dioxide equivalent (MTCO2E), million BTU, labor hours, wage dollars and tax dollars. 

Material Types Recognized by WARM
Aluminum Cans Fly Ash Mixed Paper (primarily from offices)
Aluminum Ingot Food Waste Mixed Paper (primarily residential)
Asphalt Concrete Food Waste (meat only) Mixed Plastics
Asphalt Shingles Food Waste (non-meat) Mixed Recyclables
Beef Fruits and Vegetables Newspaper
Branches Glass Office paper
Bread Grains PET (polyethylene terephthalate)
Carpet Grass Phonebooks
Clay Bricks Hard-copy Devices PLA (polylactic acid)
Concrete HDPE (high-density polyethylene) Portable Electronic Devices
Copper Wire LDPE (low-density polyethylene) Poultry
Corrugated Cardboard Leaves PP (polypropylene)
Cathode Ray Tube (CRT) Displays LLDPE (linear low-density polyethylene) PS (polystyrene)
Dairy Products Magazines/Third-Class Mail PVC (polyvinyl chloride)
Desktop Central Processing Units (CPU)s Medium Density Fiberboard Steel Cans
Dimensional Lumber Mixed Electronics Textbooks
Drywall Mixed Metals Tires
Electronic Peripherals Mixed MSW (municipal solid waste) Vinyl Flooring
Fiberglass Insulation Mixed Organics Wood Flooring
Flat-Panel Displays Mixed Paper (general) Yard Trimmings

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