Waste Reduction Model (WARM)

Kimberly Cochran, Ph.D.

Chief, Sustainable Materials Branch

Office of Resource Conservation and Recovery

NIST’s Workshop: Data and Harmonization to Improve the Circularity of Plastics

January 24 - 26, 2023
EPA’s Waste 

Reduction 

Model (WARM)

Overview

 Created in 1998 to offer high-level estimates of 

potential greenhouse gas (GHG) emissions reductions, 

energy savings, and economic impacts from waste 

management options. 

 Estimates impacts from baseline and alternative waste 

management options, including:

 Source reduction, recycling, anaerobic digestion, 

combustion, composting and landfilling.

 Models 60 materials commonly found in MSW and C&D 

debris, including plastics.
WARM Stakeholders

• Understand and compare potential solid waste management options

Municipal and state government employees

• Elementary school to higher education

Students and educators

• Commodity/material specific groups provide data and use the tool

Industry groups

• Composting council, recycling organizations, etc.

Waste reduction and waste management groups
https://www.epa.gov/sites/default/files/2020- 12/documents/warm_containers_packaging_and_non

-durable_goods_materials_v15_10-29-2020.pdf

Plastics modeled:

• HDPE

• LDPE

• PET

• LLDPE

• PP

• PS

• PVC 

• Mixed Plastics 

(40% HDPE, 60% PET)
Biobased polymer: 

PLA

• Can be 

composted, 

unlike other 

plastics 

categories

• Recycling not 

modeled
Plastics Emission Factors

Per Ton Estimates of GHG Emissions for Baseline and Alternative Management Scenarios

Material

GHG Emissions 

per Ton of 

Material 

Produced 

(MTCO2E)

GHG Emissions 

per Ton of 

Material Source 

Reduced 

(MTCO2E)

GHGEmissions 

per Ton of 

Material 

Recycled 

(MTCO2E)

GHG Emissions 

per Ton of 

Material 

Landfilled 

(MTCO2E)

GHG Emissions 

per Ton of 

Material 

Combusted 

(MTCO2E)

GHG Emissions 

per Ton of 

Material 

Composted 

(MTCO2E)

GHG Emission per 

Ton of Material 

Anaerobically 

Digested 

(MTCO2E)

HDPE 1.42 -1.42 -0.76 0.02 1.29 NA NA

LDPE 1.8 -1.8 NA 0.02 1.29 NA NA

PET 2.17 -2.17 -1.04 0.02 1.24 NA NA

LLDPE 1.58 -1.58 NA 0.02 1.29 NA NA

PP 1.52 -1.52 -0.79 0.02 1.29 NA NA

PS 2.5 -2.5 NA 0.02 1.65 NA NA

PVC 1.93 -1.92 NA 0.02 0.66 NA NA

Mixed Plastics 1.87 -1.87 -0.93 0.02 1.26 NA NA

PLA 2.45 -2.45 NA -1.64 -0.63 -0.09 NA
Plastics Management: Source Reduction

Choosing displacement of 

“current mix” or 100% 

virgin changes source 

reduction emission factors
Plastics Management: Recycling

 WARM models plastics at resin level (e.g., not bottles/other end uses).

 Recycling is modeled as closed loop, resin-to-resin.

 Recycled input credit: difference between manufacturing virgin and recycled resin.
Plastics 

Management: 

Combustion

 Emissions based on carbon content of plastics and % 

of that carbon converted to CO2 during combustion.

 Utility offsets: uses assumptions of plastic energy 

content, combustion system efficiency and national 

average grid electricity generation emissions.
Plastics 

Management: 

Landfilling

 Only emissions associated with landfilling 

plastics are transportation to landfill.

 Carbon is not biodegradable, so no CH4 

emissions or capture.

 Doesn’t count as carbon storage because fossil- fuel-derived.
Management of plastic waste in the 

United States

EPA’s Facts and Figures about Materials, Waste, and Recycling report 

estimated 35.68 million tons of plastic waste generated in 2018

These estimates do not account for littering or other mismanagement

9%

16%

75%

Recycled

Used for energy recovery

Landfilled
U.S. Plastics in MSW (2018)

Current Plastics 

Waste Management 

(tons)*

GHG 

(Million 

MTCO2e, 

est.)**

Energy 

(million 

BTU, 

est.)**

Labor 

(million 

hrs, 

est.)**

Wages 

(million 

USD)**

Taxes 

(million 

USD)**

Recycling 3,090,000 (8.7%) (3) (108) 185 $4,106 $674

Combustion 

with energy 

recovery

5,620,000 (15.8%) 7 (76) 8 $259 $96

Landfilled 26,970,000 (75.6%) 0.5 7 37 $1,244 $462

*Estimates on managed plastics waste come from EPA’s Facts and Figures report. 

** Estimates are based on using the WARM factors and include emission and energy 

offsets.
Future Plastics Work in WARM

Add Reuse 

pathway 

(for 

plastics 

reuse).

Preliminary 

scoping 

complete; 

potential 

FY24 work.

Add 

Textiles 

category 

(nylon and 

polyester).

Preliminary 

scoping 

complete; 

potential 

FY24 work.

Add 

Chemical 

Recycling 

pathway 

(plastics 

only).

Potential 

FY24 

scoping.

Plans to 

Expand 

Impact 

Categories

Potential 

FY24 

scoping.

Align with 

MSW DST 

and Peer 

Review

Potential 

FY24 

scoping.
WARM 

Resources

Documentation chapters

Containers, Packaging, and 

Non-Durable Good 

Materials Chapter

Main page: epa.gov/warm
15

Thank You!

For more information: 

epa.gov/warm

EPARecycles@epa.gov

SWIFR@epa.gov