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 dioxide equivalent (MTCO₂E) and metric tons of carbon equivalent (MTCE) across a wide range of material types commonly found in municipal solid waste (MSW).¹

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 for each management practice to calculate the GHG emissions and energy use 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. The model documentation describes this methodology in detail.

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."

Material Types Recognized by WARM
Aluminum Cans	Glass	Mixed Recyclables
Asphalt Concrete	Grass	Newspaper
Asphalt Shingles	HDPE	Office Paper
Branches	LDPE	Personal Computers
Carpet	Leaves	PET
Clay Bricks	Magazines/Third-Class Mail	Phonebooks
Concrete	Medium-density Fiberboard	Steel Cans
Copper Wire	Mixed Metals	Textbooks
Corrugated Cardboard	Mixed MSW	Tires
Dimensional Lumber	Mixed Organics	Vinyl Flooring
Drywall	Mixed Paper (general)	Wood Flooring
Fiberglass Insulation	Mixed Paper (primarily from offices)	Yard Waste
Fly Ash	Mixed Paper (primarily residential)
Food Scraps	Mixed Plastics

Who Should Use WARM?

WARM was developed for solid waste managers (from state and local governments and other organizations) who want to calculate the GHG emissions associated with different waste management options. Emissions estimates provided by WARM are intended to support voluntary GHG measurement and reporting initiatives, such as waste management components of state and local climate change action plans, and other waste management projects for which an understanding of GHG emissions is desired. WARM is not a GHG inventory tool.

Using WARM

Before using WARM, you first need to gather data on your baseline waste management practices and an alternative scenario. In order to effectively use the tool, users should know how many tons of waste was managed (or will be managed) for a given time period by material type and by waste management practice. The "mixed" material types are defined in the documentation.

Both models allow you to customize your results based on project-specific landfill gas recovery practices and transportation distances. Note that you may use default values if you are unsure of landfill gas recovery practices and/or transportation distances.

Web-based version:

To use the web-based version of WARM, you will need Firefox (version 3 or higher), Chrome, Safari, or Internet Explorer (version 6 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 button for MTCO₂E, MTCE, 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 link 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 allow the use of macros.

Excel 2003
You must have Excel security set to medium (recommended) or low (not recommended). To change this setting, 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 you the choice to enable macros; when set to low, macros are always enabled. When Excel security is set to medium, users are asked upon opening the tool whether to enable macros. Macros must be enabled in order for WARM to work. Once they are enabled, the tool will open to the introduction page.

Excel 2007
To allow macros in Excel 2007, launch Microsoft Excel 2007 before opening WARM. Once in Excel, select the “Office” icon in the top left-hand corner and click on “Excel Options” in the bottom right-hand corner of the dropdown list. In the Excel Options window, select the “Trust Center” section and click on the “Trust Center Settings…” box. Within the Trust Center Settings window, select the Macro Settings section and select the button for “Disable all macros with notification”. Within the Trust Center settings window, select the Message Bar and select the “Show the Message Bar in all applications when content has been blocked” if not previously selected. Next, open WARM. You will notice a security warning bar above the tool indicating that macros have been disabled. Select the “Options…” button next to the warning. In the “Microsoft Office Security Options” window that pops up, select “Enable this content” and click OK.

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 3-7. WARM will use the answers to these questions to customize its GHG estimates to reflect your waste management situation. If the requested data is not available, WARM will use the national average defaults.
Step 8 allows you to customize your report, with your name, organization, and project period.
In Step 9, choose whether to have your results displayed in either MTCO₂E or MTCE.
To view the energy consumption impacts of your waste management scenarios, check the box in Step 10.
Once you have completed Steps 1-10 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 "Energy Consumption" box on the input sheet, the model provides the equivalent sheets in units of energy consumption.

Assistance

If you need additional assistance with using WARM, please email orcrWARMquestions@epa.gov.

¹MTCE and MTCO2E are units of measurement that express the heat-trapping effects of various greenhouse gas emissions in carbon and carbon dioxide equivalent, respectively. An international protocol has established carbon dioxide (CO2) as the reference gas.

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