What is R&D GREET?
Developed by Argonne National Laboratory (Argonne) with support from the U.S. Department of Energy (DOE), the Research & Development Greenhouse gases, Regulated Emissions, and Energy use in Technologies (R&D GREET®) is a life cycle assessment (LCA) model that assesses the energy use and environmental impacts of vehicles, fuels, chemicals, and materials at multiple points along their life cycles. With R&D GREET, users can compare clean energy technologies—such as electric vehicles, sustainable aviation fuels (SAF), and hydrogen—to incumbent fossil fuel-based technologies like gasoline powered vehicles.
R&D GREET in Action
R&D GREET can be used to compare and contrast the complete GHG emission impacts for all components of a vehicle's life cycle. For instance, researchers can assess the GHG emission impacts between gasoline and electric vehicles (EVs), including emissions from vehicle production and end-of-life, fuel production and use, and facility construction (i.e. embodied emissions in fuel production facilities).
Figure 1: Electric vehicles today produce 46% fewer GHGs than their comparable gasoline vehicles on a life cycle basis, with even deeper reductions by 2035.
The life cycle GHG emissions on a per-mile basis for representative electric and gasoline light-duty passenger vehicles (small, sports utility vehicles). Life cycle GHG emissions include those from construction of the fuel production facility (e.g. oil well and electricity generation equipment), vehicle and battery production and end-of-life, and production and use of fuel in the vehicle.
Source: R&D GREET 2024; Simulation year: 2025. All years use 2023 NREL Standard Scenarios Midcase for estimated electricity grid generation mix.
Figure 1 shows this comparison in action by calculating the life cycle GHG emissions of two representative light-duty sports utility vehicles: one a gasoline-powered internal combustion engine (ICE) vehicle and the other an EV. This comparison looks at the emissions produced per mile (g CO2 e/ mile). Each vehicle is using a representative fuel: E10 gasoline for the ICE and the U.S. average electricity grid generation mix for the EV.1 For the ICE, fuel use (i.e., gasoline combustion in the vehicle during use) is the greatest contributor to GHG emissions, while fuel production (i.e., generating electricity) is the biggest contributor for EVs. Overall, R&D GREET shows that the 2025 EV produces 46% less GHG emissions than a comparable ICE vehicle. In 2035, R&D GREET predicts that the EV will produce 76% less GHG emissions than the 2025 ICE.
Compared to diesel internal combustion engine (ICE) trucks, hydrogen fuel cell vehicles (FCVs) have zero tailpipe emissions since the byproduct of a fuel cell operating on hydrogen is only water vapor. However, there are some upstream emissions associated with hydrogen production and delivery and with vehicle/component manufacturing. Using R&D GREET 2024, Figure 1 compares hydrogen fuel cell and diesel-ICE heavy-duty (Class 8, sleeper cab) trucks produced in 2025. It includes two different hydrogen production methods with different emission rates and compares the emissions produced per ton-mile traveled, which accounts for the distance traveled and payload that each truck can carry.
Figure 1: In 2025, life cycle GHG emissions of hydrogen fueled fuel cell trucks are less than conventional diesel trucks
The life cycle GHG emissions on a per-ton-mile basis for representative 2025 sleeper-cab heavy duty trucks (Class 8) with a 19-ton payload. FCVs assumed to have 700 bar on-board gaseous storage tank, 500-mile range. Life cycle GHG emissions include those from construction of the fuel production equipment (*e.g. wind turbines + concrete foundation, electrolyzers, oil well equipment, grid electricity generation equipment), vehicle production (including end-of-life disposal methods), and production and use of fuel in the vehicle. Error bar on diesel ICE and steam methane reforming reflects a literature estimated range of upstream natural gas recovery, processing, and transmission emissions from ~0.7% up to 5%. CCS assumes 96% capture rate. Error bar for wind electrolysis reflect a range of onshore wind capacity factors across the USA (0.11 to 0.55, see ref in fact sheet).
Source: R&D GREET 2024; Simulation year: 2025.
R&D GREET 2024 shows that:
- For the ICE, fuel use (i.e., diesel combustion in the vehicle during use) is the greatest contributor (~80%) to life cycle GHG emissions
- For fuel cell trucks, the GHG emissions depend on how the hydrogen was produced, but all pathways examined here result in emissions less than the ICE, ranging from 20 to 80% reduction relative to the diesel vehicle.
- Wind powered electrolysis (water-splitting) with gaseous delivery results in the least life cycle GHG emissions — a 70 to 80% reduction from the conventional ICE depending on where the wind turbine is located.
- Wind turbine construction contributes ~20% to the life cycle GHG emissions of hydrogen produced by wind electrolysis.
Uncertainty in upstream methane emissions from natural gas extraction results in significant uncertainty in life cycle GHG emissions for hydrogen produced from steam methane reforming (SMR) with carbon capture and sequestration (CCS). Even when accounting for this uncertainty, an SMR with CCS hydrogen fueled FCV still has lower life cycle GHG emissions than a diesel ICE truck.
What is Life Cycle Assessment?
Life cycle assessment (LCA) is a methodology used to measure and compare the impacts of products—such as fuels, vehicles or materials—on the environment to support informed decision-making. LCA evaluates a product's life cycle, encompassing all consecutive and interlinked stages, from raw material acquisition or generation from natural resources to final disposal. Ideally, LCA practitioners adopt a broad system boundary, capturing the impacts of as many stages involved in the life cycle of a product as possible.
The diagram below illustrates the life cycle of a product:
It's important to note that the figure above is meant to be illustrative – not every product will go through every stage. For instance, gasoline fuel will go through Facility Construction (e.g. oil refinery construction), Product Production (e.g. oil refining to gasoline), and Product Use (e.g. gasoline combustion in a vehicle), but it will not go through "End-of-Life" since gasoline fuel is consumed during the Product Use stage.
The individual stages are described in more detail below, using the production of a car, and gasoline fuel for the car, as examples:
Example: A refinery is constructed to refine crude oil into gasoline
Subprocesses involved in construction:
- Raw material extraction and processing to construct the facility
- Material transportation to facility construction site
- Construction and maintenance of the facility
Example: The car is built in a facility and the gasoline is refined in a refinery
Subprocesses involved in production:
- Raw material extraction and processing to produce the product
- Product manufacturing and processing
- Transport of materials to the facility to produce the product and transport of the product to consumers
Example: The car is used and consumes gasoline
Subprocesses involved in use:
- Consumption of other product(s)
Example: The car is scrapped for parts and/or sent to a junkyard
Subprocesses involved in end-of-life stage:
- Disposal
- Re-use
- Recycling
The entire collection of subprocesses that models the life cycle of a product is called the product system.
Every product serves a function, and in LCA, one of the most important concepts is the functional unit. For vehicles, the function is transportation—specifically driving a certain distance before the vehicle reaches its end-of-life.
Consequently, a common functional unit for transportation LCA is a measurable distance, such as miles or kilometers. In practice, this involves summing up the emissions associated with producing, using, and eventually disposing of a car, then normalizing (i.e. dividing) those emissions by the number of miles driven over its lifetime. This enables a fair comparison of emissions between different vehicles on a per mile driven basis.
With this information we can answer questions like: "Which type of vehicle emits fewer greenhouse gas emissions per mile driven over its entire life cycle?" Being able to answer these types of questions is critical for informed decision-making to reduce greenhouse gas emissions across many sectors of our society.
In addition to the R&D GREET versions and modules developed by Argonne National Laboratory, different GREET versions have been developed for other applications.
What Can R&D GREET Do?
For each life cycle phase of a given system, R&D GREET can calculate:
- Total energy use (non-renewable and renewable)
- Fossil fuel energy use (petroleum, natural gas, coal)
- Greenhouse gas (GHG) emissions
- Air pollutant emissions
- Water consumption
This assessment can guide research, development, and decision-making for current and future vehicle and fuel systems by analyzing trends and identifying key drivers of environmental impacts. R&D GREET uses a variety of reliable, publicly available sources for its data.2
Who is R&D GREET For?
1The U.S. grid is powered by a mix of power plants that use different fuel sources to generate electricity (e.g. coal, natural gas, wind, solar, nuclear, and others)
2Data sources include: EPA's Emissions & Generation Resource Integrated Database, or eGRID, for data on electric systems and emissions inventories, the U.S. Energy Information Administration for current and future energy projections, simulation models for predicting the energy use, emissions, and resource use of future technologies, peer-reviewed publications, data from private industry and other government agencies.