User's Guide for WARM

Calculating Greenhouse Gas Emissions with the WAste Reduction Model

What is the WAste Reduction Model?

The WAste Reduction Model (WARM) was created by the U.S. Environmental Protection Agency (EPA) to help solid waste planners and organizations estimate greenhouse gas (GHG) emission reductions from several different waste management practices. WARM is available in a Web-based calculator format and as a Microsoft Excel^© spreadsheet. Both versions of WARM are available on EPA's Web site.

WARM calculates GHG emissions for baseline and alternative waste management practices, including source reduction, recycling, combustion, composting, and landfilling. The model calculates emissions in metric tons of carbon equivalent (MTCE) and metric tons of carbon dioxide equivalent (MTCO2E) across a wide range of material types commonly found in municipal solid waste (MSW).¹ In addition, the model calculates energy use for each of the options, and the Microsoft Excel^© version allows users to report results by year, by gas, and by year and gas. These options facilitate reporting to the Department of Energy's 1605(b) program.

The user can construct various scenarios by simply entering data on the amount of waste handled by material type and by management practice. WARM then automatically applies material-specific emission factors specific for each management practice to calculate the GHG emissions and energy savings of each scenario. Several key inputs, such as landfill gas recovery practices and transportation distances to MSW facilities, can be modified by the user.

NOTE

ReCon and WARM were developed for purchasers and waste managers, respectively. ReCon calculates the benefits of alternative recycled content purchasing decisions. WARM, on the other hand, calculates the benefits of alternative end-of-life waste management decisions. Both tools calculate the benefits of an alternative scenario versus a business-as-usual scenario. The WARM and ReCon tools are based on a life-cycle approach, which reflects emissions and avoided emissions upstream and downstream from the point of use. As such, the emission factors provided in these tools provide an account of the net benefit of these actions to the environment. This life-cycle approach is not appropriate for use in inventories because of the diffuse nature of the emissions and emission reductions contained in a single emission factor.

The GHG emission factors were developed following a life-cycle assessment methodology using estimation techniques developed for national inventories of GHG emissions. EPA's report Solid Waste Management and Greenhouse Gases: A Life-Cycle Assessment of Emissions and Sinks (EPA 530-R-02-006) describes this methodology in detail. For a free copy of this report, visit http://www.epa.gov/epaoswer/non-hw/muncpl/ghg/greengas.pdf (1,165 KB PDF) or call National Service Center for Environmental Publications (NSCEP) at 1-800-490-9198.

For some material types, WARM indicates that recycling reduces more GHG emissions than does source reduction. This is because recycling is assumed to displace 100 percent virgin inputs, whereas source reduction is assumed to displace some recycled and some virgin inputs. For more information, please see "Why Recycling Some Materials Reduces GHG Emissions More than Source Reduction."

WARM was recently revised to include 5 new materials: personal computers, carpets, fly ash, clay bricks, and concrete used as aggregate. The methodologies used to develop these emission factors are described in detail in the following background reports: Carpet and Personal Computers (346 KB PDF), Fly Ash Used as a Cement Replacement in Concrete (585 KB PDF), and Clay Brick Reuse and Concrete Recycling (775 KB PDF).
 

Material Types Recognized by WARM
Aluminum Cans	Branches	Carpet
Clay Bricks	Concrete Recycled as Aggregate	Corrugated Cardboard
Dimensional Lumber	Fly Ash	Food Scraps
Glass	Grass	HPDE
LDPE	Leaves	Magazines/ 3rd -Class Mail
Medium-Density Fiberboard	Mixed Metals	Mixed MSW
Mixed Organics	Mixed Paper	Mixed Plastics
Mixed Recyclables	Newspaper	Office Paper
Personal Computers	PET	Phonebooks
Steel Cans	Textbooks	Yard Trimmings

Who Should Use WARM?

Using WARM

Web-based version:

• To use the web-based version of WARM, you will need Internet Explorer or Netscape versions 4 or higher.
• For the web-based WARM model to be able to calculate your GHG emissions you must enter the tons of each material type managed into the baseline and alternative management tables. The boxes in the baseline and alternative tables correspond to specific material types and management practices. Be sure to enter your data in the correct boxes.
• Answer the questions pertaining to landfill gas recovery and transportation distance by selecting the appropriate toggle buttons. If the requested data is not available, WARM will use the national average defaults.
• Select a format to display your results by selecting the corresponding toggle buttons for either MTCE, MTCO2E, or energy units (million BTU).
• To customize your report, enter your name, organization, and reporting period in the input cells.
• Once you have completed the tables and answered all of the questions on the inputs page, WARM will calculate the GHG emissions associated with the baseline and alternative waste management scenarios you specified. Click "Create Summary" to see your results.
• The summary sheet provides a concise report of GHG emissions from the baseline and alternative waste management scenarios, as well as an estimate of the net change in emissions.
• Once you have seen your results, you can return to the inputs page to run additional scenarios by selecting the button labeled "Exit Summary."
• Alternatively, you can view the emission factors used to estimate emissions for various materials and management practices; note that these emission factors will reflect national average default values for landfill gas recovery and transportation distances in the units you select. To access these emission factors, click the button labeled "View Emission Factors" from either the inputs page or the summary page.
• Please note that web-browser third-party tool bars (such as Google^TM) may attempt to “autofill” input cells and result in a yellow highlight. To prevent this please disable the autofill function of any third-party tool bars.

Microsoft Excel ^® Version:

IMPORTANT

Because WARM employs macros, users must have Excel security set to medium (recommended) or low (not recommended). To change this setting, first launch Microsoft Excel before opening WARM. Once in Excel, go to the Tools menu, click on the Macro sub-menu, and then select “Security”. The Security box will appear. Click on the “Security Level” tab and select medium. When set to high, macros are automatically disabled; when set to medium, Excel will give users the choice to enable macros; when set to low, macros are always enabled. When Excel security is set to medium, users are asked whether to enable macros upon opening the module. Click “Enable Macros” in order to activate macros, which will allow the tool to function properly.

• To use the Microsoft Excel^© version of WARM, follow the directions on the Web site for downloading and installing Microsoft Excel^© WARM. After successfully downloading the file, open the spreadsheet.
• Now, click on the "Analysis Inputs" tab at the bottom center of the screen to open the input sheet. Follow the instructions for Steps 1 and 2. This involves filling in the tables describing your baseline and proposed alternative waste management scenarios.
• Fill in the data requested in Steps 3-5. WARM will use the answers to these questions to customize its GHG estimates to reflect your waste management situation. For example, you are asked for data on transportation distances and on your landfill gas recovery systems, if applicable. If the requested data is not available, WARM will use the national average defaults.
• Step 6 allows you to customize your report, with your name, organization, and project period.
• In Step 7, choose whether to have your results displayed in either MTCE or MTCO2E.
• If you are a participant in the Department of Energy's 1605(b) program, check the box in Step 8. This will display results phased over 30 years and by gas.
• To view the energy consumption impacts of your waste management scenarios, check the box in Step 9.
• Once you have completed Steps 1-9 on the "Analysis Inputs" sheet, WARM will calculate the GHG emissions attributable to the baseline and alternative waste management scenarios you have specified. Emissions calculations are presented on separate output sheets, as described below. From the "Analysis Inputs" sheet, click on a tab at the bottom of the screen for the results sheet you want to view first.
• The "Summary Report" sheet provides a concise report of GHG emissions from the baseline and alternative waste management scenarios, as well as an estimate of net emissions in the units selected.
• The "Analysis Results" sheet shows GHG emissions for each scenario in the units selected. You can compare the total impact of the baseline and alternative scenarios, or, if you want more detail, you can scroll down to view GHG emissions or energy results by material type and management practice.
• If you checked the “DOE 1605(b) User” box on the input sheet, the model provides the equivalent sheets displaying the results phased over 30 years, by gas, and by gas phased over 30 years.
• If you checked the "Energy Consumption" box on the input sheet, the model provides the equivalent sheets in units of energy consumption.

Assistance