GREET Life Cycle Analysis of Plastic Pathways 

to Support a Circular Economy

Troy R. Hawkins, Thathiana Benavides, Ulises Gracida, Taemin Kim

Systems Assessment Center

Energy Systems and Infrastructure Analysis Division

Argonne National Laboratory

NIST Plastics Data & Harmonization Workshop

January 25, 2023
Systems Assessment Center

 Assess technologies and programs 

against sustainability goals

– Focus on greenhouse gas, criteria 

pollutants, and resource use.

– Identifying opportunities for 

improvement. 

 Diverse group of ~65 engineers, 

economists, analysts, modelers, and 

planners.

Analyzing the benefits and 

challenges of technologies to 

make the U.S. more sustainable, 

secure, and resilient.

2
GREET Model Overview

Greenhouse Gases, Regulated Emissions, and Energy Use in Technologies

3

– Used to inform and guide DOE research and external policies

• Argonne has been developing GREET since 1995 with annual 

updates and expansions.

• Expanded from transportation-focus to include a wide range 

of technologies

– Fuels, Vehicles, Chemicals, Plastics, Agriculture, Metals, 

Concrete, Buildings, Batteries, Electricity Infrastructure

• Consistent tracking of the life cycle performance of energy and products
GREET Scope

Key LCA metrics

4
~50,000 Registered Users
GREET Informs Policy and Regulation • California-GREET is an adaptation of Argonne’s GREET model

• Specified in Inflation Reduction Act related to the Clean Fuel Production 

Credit and the Clean Hydrogen Credit

• U.S. EPA uses GREET with other sources for Renewable Fuels Standard 

pathway evaluations

• Oregon Clean Fuels Program also uses an adaptation of Argonne’s GREET 

model

• National Highway Traffic Safety Administration for fuel economy 

regulation

• Federal Aviation Administration and International Civil Aviation 

Organization using GREET to evaluate aviation fuel pathways

• U.S. Maritime Administration - renewable marine fuel options for IMO 

2020 sulfur limits

• U.S. Dept. of Agriculture bioenergy LCA and carbon intensity of farming 

practices

• Canadian Clean Fuel Standard for Environment and Climate Change 

Canada fuel pathways
Plastics in GREET 

GOAL: 

Conduct analysis of advanced technologies to enable bioplastics and a 

circular economy for plastics. Provide scientific research and build 

consensus around technologies to address plastic waste and improve 

sustainability.

• LCA of bioplastics, plastic re-/upcycling, and plastic-to-fuels. 

• Develop a circular economy sustainability analysis framework.

• Stakeholder engagement and consensus building.

Key issues:

• Establish technologies to enable a sustainable future for plastics.

• Understand the potential for chemical recycling vs. pyrolysis vs. wasteto-energy.

• Improve the environmental performance and economics of biofuels 

with co-products.

• Build consensus around the sustainability implications of circular 

economy strategies.

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Feedstock

• Fossil-based

• Chemical 

precursors 

(ethylene, 

propylene, 

naphtha, etc.)

• Bio-based

• Cellulosic

• Woody

• Waste

• Biochemical 

precursors: 

adipic acid, 

acrylic acid, bioethylene, etc.)

Conversion

• Chemical

• Thermochemical

• Biochemical

Manufacturing

& Processing

• Extrusion

• Compression 

molding

• Blow molding

• Calendaring

• Injection 

molding

Products 

• Fossil-based

• PET

• HDPE/LDP

E

• Nylon 6, 66

• PC

• PP

• PUR

• PVC

• Bio-based

• Bio-PE

• Bio-PET

• PLA

• PEF

End-of-Use

• Landfill 

• Composting

• Combustion 

with energy 

recovery

• Recycling 

• Mechanical 

recycling 

• Chemical 

recycling 

• Biochemical 

recycling

Plastics

GREET contains plastics supply chains to help address environmental concerns related to the 

production and use of plastics

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 Objectives

– Quantify and compare energy and environmental metrics for conventional and circular plastic packaging pathways by 

extending the life cycle analysis (LCA) framework to address circular/upcycling pathways

– Specify a framework for analysis of plastic in circular economy, building on established LCA methods

 Analysis

– The study compares the production of PET bottles through different technologies

– A circular economy sustainability analysis framework was developed in GREET

– The framework integrates LCA with Material Flow Analysis (MFA) to simultaneously estimate environmental and circularity 

metrics

– Four case studies were designed to evaluate the interactions between the conventional and circular PET production 

pathways 

Conventional pathways

• Virgin PET - PTA & EG route

• Virgin PET - DMT & EG route

Circular pathways

• Mechanical recycling

• Enzymatic hydrolysis

Life Cycle Analysis

Greenhouse Gases, Regulated 

Emissions, and Energy Use in 

Technologies (GREET) Model

Estimation of material flow factors

• Recycling rates

• Yields of operations

• Recycled content

• Co-product shares

• Technology shares

Estimation of flows in the supply chain

Material Flow Analysis

Environmental metrics

• GHG emissions

• Total energy consumption

• Water consumption

Circularity metrics

• Virgin material use

• Solid waste generation

PET: Polyethylene terephthalate

PTA: Purified terephthalic acid

DMT: Dimethyl terephthalate

EG: Ethylene glycol

1) Current state

2) Max. mechanical recycling

3) Mechanical & Chemical

4) Mechanical, Chemical & Upcycling

Circular Economy Sustainability Analysis Framework of Plastics
Circular Economy Sustainability Analysis for Plastics

10 Gracida et al., 2022. A Circular Economy Sustainability Analysis Framework for 

Plastics: Application for Polyethylene Terephthalate (PET). Under review. 

Net 

recycled 

bottles

1-B

B Bottle 

to bottle

Bottle to 

co-products

1-E

E

Polymerization

Waste 

PET 

bottles

Injection 

stretch 

blow 

molding

R5r

Injection 

stretch 

blow 

molding

R5

Bottles from 

virgin and 

recycled 

resources

Fossil MEG 

and PTA 

production Polymerization

Fossil MEG 

and DMT 

production

Polymerization

Virgin 

PET

Operations 

at MRF

R2b

Reclaiming 

bottle

R3b

Collection

R1b

Mechanical 

extrusion

R4r

Enzymatic 

hydrolysis

R4h

Solid waste

Recycling losses

U2

Waste 

PET 

textile

Collection

R1f

Reclaiming 

textile

R3f Net 

recycled 

fiber

1-D

D Fiber to 

bottle

Fiber to 

co-products

Polymerization

Methanolysis

R4m

Waste 

PET 

carpet

Collection

R1f

Solid waste Recycling losses

Reclaiming 

carpet

R3f

Fossil 

feedstock

Fossil 

feedstock

Recycled PET

(Bottle-to-bottle)

Upcycling

(Fiber-to-bottle)

LCA

Life cycle inventories

MFA

Material flow factors

Environmental 

indicators Circularity indicators

Technology pathway Multicycle Systems analysis

Tools

Technology pathways

Approaches

Metrics

Recycling rates 

Yields

Yields

Determine the 

Mass flows

New plastic recycling 

pathways for PET (bottle) 

production:

- Mechanically-recycled PET

- Chemically-recycled PET 

(via enzymatic hydrolysis)
Circular Economy Sustainability Analysis for Plastics

Life cycle impacts and circularity metrics of the supply chain of PET Bottles by 

applying different circular economy strategies

System boundary of 

the analysis in GREET

Sankey diagram of the U.S. supply chain of PET bottles when applying 

simultaneous circular economy strategies

Major findings of the study

• Trade-offs between the environmental and circularity indicators of the 

recycling technologies were identified

• Recycling technologies with lower GHG emissions increase the reliance on 

virgin materials and vice versa

• Reclaiming operations are the major drivers of GHG emissions in the 

recycling pathways

• Chemical recycling and upcycling do not reduce the life-cycle impacts of the 

current supply chain but reduce virgin material use and solid waste generation
Post-Use Plastic (PUP) conversion to products

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• Updated version of post-use plastic conversion via 

pyrolysis

• Industry data collected to characterize post-use 

plastic pathways

• Included production of intermediate product such as 

pyrolysis oil and fuel such as ultra-low sulfur 

(ULS) diesel.

• Presented the data for two types of facilities: (1) 

pioneer, and (2) Nth-plant. 

• New inventories

• PET reclaiming operations (PET bottle-to-PET 

flake), 

• Mechanical extrusion (PET flake-to-mechanically 

recycled resin),

• Enzymatic hydrolysis (PET flake to purified 

terephthalic acid and ethylene glycol). 

• New lubricant pathways

• Plastic Upcycling to Lubricant Product: (Cappello, 

V. et al. 2022)

Collection

Sorting 

at MRF Pretreatment

Conversion

Separation/ 

Upgrading 

PCP

Transport

Pyrolysis oil

Feedstock 

logistics and 

processing

Operations at 

pyrolysis facility

Transport

ULS 

Diesel

(Displacement or 

allocation)

A B

Char

(Displacement or 

allocation)

1) Landfill

2) Energy

co-product Vehicle 

operation

GREET model for 

ULS diesel

PIP

Transport

Fuel 

gas

Heat 

generation

Naphtha Wax

(Displacement or 

allocation)

(Displacement or 

allocation)
Life cycle analysis of plastic-to-plastic pathways via pyrolysis

 Evaluate the impacts of producing polyolefins through cofeeding of PUP-derived pyrolysis oil with conventional feedstocks ( 

naphtha and natural gas liquids)

 Use the mass balance approach to estimated GHG Emission reductions of different scenario including 5% and 20%, Plant 

capacity of the pyrolysis conversion facility (Pioneer vs Nth-plant), Counterfactual scenarios (U.S. vs. E.U), composition of 

the baseline feedstock of crackers

 HDPE with 100% allocated recycled feedstock showed up to 23% reductions in GHG emissions compared to conventional 

production of HDPE

 Inclusion of the avoided emissions from traditional end-of-life management in the United States reduced in up to 50% the 

GHG emissions compared of the conventional production of HDPE

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Cross-database comparisons for plastics LCA: goal and scope

Database GREET USLCI Ecoinvent GaBi

Software GREET OpenLCA OpenLCA GaBi

Version 2021* 2021 Spring Quarter v.3.7.1 v.10

Publisher ANL NREL Ecoinvent Sphera

Access Free public access Free public access One-time purchase Subscription-based

PET O (dataset available) O O O

HDPE O O O O

PP O O O O

bio-PE O X (not available) X O

PLA O O O O

Landfill O X O O

Incineration O X O O

Mech. Recycling O O O X

• Different plastics LCA databases have significant cross-database discrepancies

• To identify the sources and quantify the degree of the discrepancy, multiple LCA databases are investigated 

for five popular resin products and three post-use phases.

• The outcomes can help governmental agencies implement environmental regulations and other policies to plastics 

industry using the LCA approach

*Some of the significant updates in GREET 2022 are reflected in the current analysis

Resin 

production

Post-use 

phase
Cross-database comparisons for plastics LCA: metrics investigated

Datasets (UUID)

LCI references

Temporal representation

Geographical representation

System boundary

Final product and functional unit

Technology coverage and details

Degree of representation

Number of plants (and/or producers)

Foreground co-products and allocation methods

Granularity (or Transparency)

Metadata characteristics comparisons Breakdown analysis

• Metadata comparisons and breakdown analysis are conducted to quantify the degree and identify the sources of 

discrepancy.

• Life cycle impact assessment (LCIA) results are compared across the databases on the consistent impact 

category and factors for valid comparisons.
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Series of publications providing LCA results for 

biobased plastics and plastic-to-energy pathways.

• Environmental benefits of bio-based PET and 

recycled PET bottles

• Incorporating biodegradation of compostable 

plastic into LCA of bioplastics

• LCA of non-recycled plastics to fuels

• LCA comparison of biobased and conventional 

chemicals

• LCA of stover-derived lactic acid and ethyl 

lactate

• LCA of new bioplastic

• New feedstocks, alternative feedstocks

• Data collection from industry waste plastic 

conversion process

– Expansion of GREET® to include biobased 

plastics, conventional virgin and recycled plastics, 

biochemical co-products from biorefineries, and 

conventional chemicals. 

Accomplishments
Thank you!

https://greet.es.anl.gov/ 

greet@anl.gov

Michael Wang

Amgad Elgowainy

Uisung Lee

Kwang Hoon Baek

Adarsh Bafana

Thathiana Benavides

Andrew Burnham

Hao Cai

Vincenzo Cappello

Peter Chen

Yu Gan

Ulises Gracida

Troy Hawkins

Rakesh Iyer

Jarod Kelly

Taemin Kim

Shishir Kumar

Hoyoung Kwon

Kyuha Lee

Xinyu Liu

Zifeng Lu

Farhad Masum

Clarence Ng

Longwen Ou

Krishna Reddi

Nazib Siddique

Pingping Sun

Pradeep Vyawahare

Hui Xu

Greg Zaimes

GREET 2022 Contributors
GREET 1

• Updated and expanded hydrogen production pathways 

with GUI in GREET Excel version

• Updated CO2 utilization simulations: carbon accounting, 

detailed modeling of CO2 capture, compression, and 

transportation, direct air capture

• Included offshore macroalgae production technologies

• Updated and expanded marine fuel production 

pathways, with a GREET marine module

• Updated and expansion of biodiesel and renewable 

diesel: used cooking oil is added. 

• Updated post-use plastic pyrolysis conversion

• Updated and expanded waste to polylactic acid (PLA) 

and plastic modeling

• Updated and expanded of ammonia production 

pathways (conventional, blue, and green ammonia)

• Added post-use plastic to lubricant product pathways 

(including synthetic lubricants poly-alpha olefins)

• Added an air separation unit to O2 and N2 production

GREET 2022 Updates

• Updated infrastructure LCA for nuclear power, hydropower, wind 

turbines, solar photovoltaics

• Updated and expanded LCA of electrolyzers (solid oxide, alkaline, 

and proton exchange membrane)

• Updated light-, medium-, and heavy-duty vehicle components

• Updated and expanded the battery LCA module with new 

materials and domestic lithium production

• Updated inventory data for aluminum production

• Updated LCA of critical materials (Ni, Cu, Ti, and rare earth elems)

• Added the end-of-life credit approach of vehicle recycling (steel 

and aluminum)

• Global warming potentials of AR6

• US electricity generation mix and crude oil mix

• Methane leakage of natural gas supply chain

• Fuel use for natural gas recovery

• Expansion of plastic inventory

• Energy intensity of rail movement of passengers

• Aviation payload energy intensities and combustion emissions

• HD hybrid electric vehicle fuel economy

• Feedstock slate for U.S. steam crackers

GREET 2

Background Data