Use of EPA's Emission Factors Hub's Waste Emission Factors vs.
the Waste Reduction Model (WARM): Guidance for Organizations

EPA developed this resource to help organizations better understand two EPA-developed tools and
when the tools may meet the needs of stakeholders. This resource clarifies when organizations should
use waste emission factors to develop a Scope 3 GHG emissions inventory and when to use the WARM
Tool as a decision-making tool for waste management activities (e.g. recycling) and to communicate the
environmental benefits of such efforts.

What is WARM and what is the Emission Factors Hub's waste emission
factors?

•	The WARM Tool [https://www.epa.gov/warm] calculates and totals GHG emissions of baseline
and alternative waste management practices—source reduction, recycling, combustion,
composting, anaerobic digestion and landfilling. WARM version 15 models 6 management
practices and 60 materials. WARM version 15 can be downloaded here:
https://www.epa.gOv/warm/versions-waste-reduction-model-warm#15

•	The waste GHG emission factors in the Center for Corporate Climate Leadership's Emission
Factors Hub [https://www.epa.gov/climateleadership/center-corporate-climate-leadership-ghg-
emission-factors-hub] are intended to be used to calculate emissions from scope 3 category 5:
Waste generated in operations and scope 3 category 12: End of life treatment of sold products
for a corporate inventory. If a company has waste data by material type and weight (e.g., short
ton) generated in a specified time period (usually one year), GHG emissions can be calculated by
multiplying by the factors in the Emission Factors Hub. The Emission Factors Hub can be
downloaded at: https://www.epa.gov/climateleadership/center-corporate-climate-leadership-
ghg-emission-factors-hub.

•	Both EPA's WARM tool and the Emission Factors Hub rely on the same underlying data from
EPA's WARM Tool. However, these tools have different applications and are not
interchangeable.


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When and why should these tools be used?



WARM Tool

Waste emission factors in
the

Emission Factors Hub

Purpose

Supports GHG-based decision-
making for materials
management.

Support voluntary reporting under
the GHG Protocol Corporate
Accounting and Reporting
Standard.

Function

Communicates life-cycle impacts,
including avoided emissions
across different waste
management practices.

Assess Scope 3 emissions from
waste generated in an
organization's operations or from
end-of-life treatment of sold
products.

Use

Compares baseline and
alternative materials
management scenarios to
determine the least
environmentally impactful waste
management practice

Used to report on emissions from
third-party disposal and treatment
of waste that is generated in the
reporting company's owned or
controlled operations in the
reporting period.

Hypothetical
Use Scenario

Hypothetical Use Scenario:

A company is considering
different ways it can manage
waste. The considerations are
source reduction, landfilling,
recycling and composting. Before
making a decision, the leadership
at a company wants to
understand the life cycle GHG
impacts of these management
methods. This company should
use the WARM model.

Hypothetical Use Scenario:

A company is completing a
comprehensive scope 3 GHG
inventory consistent with the GHG
Protocol Scope 3 Standard. It
determined that emissions from
waste disposal (category 5) are
relevant and it therefore needs
emission factors to estimate GHG
emissions for this category. This
company should use the waste
factors in the Emission Factors
Hub.

The following decision tree summarizes when organizations should use the WARM Tool or the waste
emission factors from the Emission Factors Hub to measure and communicate on the GHG emissions
associated with waste management activities:


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Key differences between WARM emissions data and the Emission Factors
Hub's waste emission factors:

Waste emission factors in the Emission Factors Hub: Under the GHG Protocol Corporate Accounting
and Reporting Standard, companies should not report negative or avoided emissions associated with
recycling or other materials management activities. Any claims of avoided emissions associated with
recycling should not be included in, or deducted from, the scope 3 inventory. The waste emission factors
in the Emission Factors Hub were adapted from WARM and modified to account for all future emissions
that result from the treatment of waste generated in the reporting period. The waste emission factors
exclude negative or avoided emissions from materials management efforts, such as recycling.

By comparison, the WARM Tool includes both emissions generated and emissions avoided across the
life-cycle of materials based on both the baseline and alternative scenarios presented by the user.

For example, using the WARM model to examine alternative waste management scenarios, the act of
landfilling 100 tons of aluminum cans results in approximately 2 MTC02e. Recycling 100 tons of
aluminum cans results in a net savings of nearly 913 MTC02e which accounts for the net benefit of using
recycled aluminum compared to virgin ore in the manufacturing processes. The net GHG emissions
saved from the alternative recycling scenario is 913 MTC02e + 2 MTC02e = 915 MTC02e.

In contrast, when developing a scope 3 inventory for waste management activities, the emissions
associated with the act of landfilling 100 tons of aluminum cans are 2 MTC02e and the emissions
associated with the act of recycling are 6 MTC02e.

Guidance on communications:

For companies seeking to communicate to stakeholders the emissions resulting from their waste
management activities and/or the environmental benefits of its waste management activities (e.g.
recycling, composting, source reduction):

• Users of the Emission Factors Hub factors should present scope 3 emissions separately from any
claims of avoided emissions from materials management activities.

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•	WARM results can be used to communicate potential lifecycle impacts from decisions made by
the organization but shouldn't be presented as part of the organization's Scope 1, 2, and 3
inventories.

•	WARM results can also be translated into common equivalencies such as acres of trees planted
or number of cars taken off the road for a year. These conversions are supported by the EPA's
Greenhouse Gas Equivalencies Calculator (https://www.epa.gov/energy/greenhouse-gas-
equivalencies-calculator).

•	The GHG Protocol includes guidance on how companies can present avoided emissions in
Section 9.5 of the GHG Scope 3 Protocol, where data are available

[https://ghgprotocol.org/sites/default/files/standards/Corporate-Value-Chain-Accounting-
Reporing-Standard 041613 2.pdf1.

For more information:

•	WARM documentation and guidance documents [https://www.epa.gov/warm]

•	GHG Protocol Corporate Value Chain (Scope 3) Accounting and Reporting Standard
[https://ghgprotocol.org/standards/scope-3-standard]

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