The transition to electric mobility is being driven by the need to reduce greenhouse gas (GHG) emissions from fossil fuels that contribute to climate change. The transportation sector produces about 25% of global greenhouse gases or 12 gigatonnes of CO2 equivalent (CO2eq) annually. Transitioning to electric mobility displaces fossil fuel combustion as part of a larger strategy (ref. the Paris Agreement) intended to limit global warming to less than 2 degrees Celcius.
What are greenhouse gases – GHG and CO2 eq
The term ‘greenhouse’ implies an enclosure with transparent walls and ceilings where sunlight can enter and heat retained to create conditions favourable for plant growth. Earth’s atmosphere is like a giant greenhouse. The gases in our atmosphere allow sunlight through and provide insulation to slow heat dissipation at night. The amount of insulation provided depends on the mixture of gases. Some gases provide more insulation than others and are called ‘greenhouse gases’. Every greenhouse gas has its own Global Warming Potential (GWP) based on its chemical properties.
There are many different Greenhouse gases (GHGs) that fall into two categories – naturally occurring and synthetic. The three main naturally occurring GHGs are carbon dioxide (CO2), methane (CH4), and nitrous oxide (NO2). The synthetic gas family includes hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride. Synthetic gases are manufactured and are used in household, commercial and industrial processes (such as air conditioning). Carbon Dioxide makes up the majority of US and Canadian GHG emissions, at about 80%.
Ref: US Environmental Protection Agency
Referencing the global warming potential of any specific source of GHG emission can be cumbersome because of the many variations of gas mixtures. In order to provide a basis for comparison of different sources, the GHG content may be represented by the equivalent carbon dioxide content which would result in global warming. Each different gas in a mixture is assigned a weighted value of its warming potential relative to that of carbon dioxide. The weighted sum of the carbon dioxide equivalent warming can be calculated for any gas mixture. The term CO2 eq is used to describe the total warming effect of gas mixtures without getting bogged down with the specifics of the mix.
Vehicles produce GHGs through various mechanisms throughout their lifecycles. Internal combustion engine (ICE) vehicles produce most GHGs during their use phase through tailpipe emissions from burning fossil fuels. The life cycle carbon emission of an ICE depends mostly on its fuel efficiency and the fuel production process (well to tank).
Battery Electric Vehicles (BEVs) on the other hand produce no tailpipe emissions and are classified as Zero-Emission Vehicles (ZEVs). It does not suggest that ZEVs have a zero carbon footprint. They produce carbon through the use phase of their life cycle from the generation of electricity to charge their battery. ZEVs also create significant emissions through battery manufacturing. At this time EV batteries are largely manufactured in China, Japan, and South Korea where electricity generation is mostly from fossil fuels. The emission produced by ZEVs depends mostly on the carbon intensity of the electrical generation in the region where batteries are manufactured and the vehicle is used.
Transportation carbon emission varies widely depending on vehicle type and geographic region. It is possible to select extreme use-cases to promote various narratives, however, the vast majority of circumstances support the case for adopting EVs to reduce global carbon emissions. Research published by the University of Cambridge in England in 2020 concluded that EVs were better than ICEs for the climate in 95% of the world. In the USA it would be reasonable to estimate that EVs will provide a 60% to 68% % (Bieker, ICCT – 2021) lifecycle reduction in carbon emissions. In Canada, the reduction would be greater because of the lower carbon intensity of the electricity grid.
The science supports the premise of an overwhelming net reduction in lifecycle global emissions through electric mobility.
Lifecycle assessment
The only meaningful way to compare the carbon emission of mobility options is through lifecycle assessment (LCA) to determine the carbon footprint of competing technologies. The term ‘lifecycle‘ means cradle to grave and includes all of the incremental environmental impacts which can be attributed to a vehicle. Lifecycle assessment of mobility alternatives is complex and requires intellectual resources typically only available to academic institutions, research organizations, and governments. Fortunately, assessments have been ongoing for decades in order to support government policies and actions to meet climate change goals identified in international agreements, including the 2015 Paris Agreement.
In the United States, a 2012 “Lifecycle Comparison of a Battery Electric Vehicle and a Conventional Gasoline Vehicle” conducted by the UCLA Institute of the Environment and Sustainability for the California Air Resources Board found a 50% life-cycle emission reduction in a BEV compared to an ICE.
In 2018, the City of Vancouver performed a life cycle carbon emission assessment comparing a Ford Focus ICE with a Mitsubishi i-MiEV and determined that the EV would produce 50% less carbon than the ICE option.
A 2021 White Paper by the International Council on Clean Transportation (ICCT) “A Global Comparison of the Life-Cycle Greenhouse Gas Emissions of Combustion Engine and Electric Passenger Cars” found:
“…assessment finds that the life-cycle emissions over the lifetime of BEVs registered today in Europe, the United States, China, and India are already lower than a comparable gasoline car by 66%–69% in Europe, 60%–68% in the United States, 37%–45% in China, and 19%–34% in India. For medium-size cars projected to be registered in 2030, as the electricity mix continues to decarbonize, the life-cycle emissions gap between BEVs and gasoline vehicles increases to 74%–77% in Europe, 62%–76% in the United States, 48%–64% in China, and 30%–56% in India.”
In 2021 the International Energy Agency published a lifecycle assessment:
A recent study published in January 2022 by the Fuels Institute in the US “Life Cycle Analysis Comparison” shows a 41% reduction in life cycle emissions through the use of electric vehicles.
A collaborative academic article on lifecycle assessment with authors from multiple European Universities published in 2022 looked at 790 different vehicle variants to find EVs reduce…
“…total life-cycle emission in comparison to combustion engine vehicles by 73% and 89%, respectively”
Case studies consistently point to the use phase of the life cycle to be the source of the largest portion of carbon emissions regardless of the technology used. The UCLA study finds that conventional ICE vehicles generate 96% of their carbon emissions during the use phase compared to 69% for EVs.
Battery manufacturing produces more carbon emissions than conventional vehicle manufacturing and is the second-largest contributor to emissions from BEVs. Conventional vehicle emission for all lifecycle phases outside of actual use is very small (5% total) compared to the use phase of the lifecycle.
The case for transitioning ICE-based mobility to electric becomes stronger as electricity generation migrates to lower carbon sources and battery technology improves. Reducing the carbon intensity of electricity generation is another initiative being driven globally by climate agreements.
“EVs convert over 77% of the electrical energy from the grid to power at the wheels. Conventional gasoline vehicles only convert about 12%–30% of the energy stored in gasoline to power at the wheels.”
Some additional insight into fossil fuel-based transportation vs electric vehicles
For a well-done summary comparing ICE vs EVs see the video below by Mark Linthicum on YouTube.
All sources are cited on the YouTube page “EV or Gas, What Pollutes More?“
posted with permission from Mark Linthicum
Note that the video creator, Mark Linthicum has pointed out that the calculation at the 2-minute mark of the video is actually 13 billion kWh used by oil rigs and not 1.3 billion. The video originally used performance data from a 2019 Tesla Model 3. The new 2021 Tesla Model 3 is more efficient than the 2019 version meaning that over 70 million electric cars can run off the energy used to pump oil out of the ground in the US and offshore, not 19,500,000, as mentioned in the video.
Additional fact-checking by the Carbon Brief is available in their article “Factcheck: How electric vehicles help to tackle climate change“. The article is geared toward Europe and the UK, however, it is relevant to the rest of the globe.
Citations:
The following articles provide supporting data for this article.
Reuters: Analysis: When do electric vehicles become cleaner than gasoline cars?, 2021, Paul Lienert
World Auto Steel: LCA – Life Cycle Assessment of Vehicle Emissions
Fuels Institute: “Life Cycle Analysis Comparison“, 2022, Ricardo Strategic Consulting
Renewable and Sustainable Energy Reviews: “Total CO2-equivalent life-cycle emissions from commercially available passenger cars”, 2022, Johannes Buberger, Anton Kersten, Manuel Kuder, Richard Eckerle, Thomas Weyh, Torbjörn Thiringer
Government agencies
US EPA: “Greenhouse Gas Emissions from a Typical Passenger Vehicle”
Canada Energy Regulator: “Market Snapshot: How much CO2 do electric vehicles, hybrids and gasoline vehicles emit?”
Academic references
University of California, Los Angeles: “Lifecycle Comparison of a Battery Electric Vehicle and a Conventional Gasoline Vehicle”, 2012, UCLA Institute of the Environment and Sustainability
Cambridge University (UK): “Net emission reductions from electric cars and heat pumps in 59 world regions over time“, 2020, Florian Knobloch, Steef V. Hanssen , Aileen Lam, Hector Pollitt, Pablo Salas, Unnada Chewpreecha, Mark A. J. Huijbregts and Jean-Francois Mercure
Simon Fraser University: “Environmental Life Cycle Assessment of Electric Vehicles in Canada”, 2018, Pete Poovanna, Ryan Davis, and Charlotte Argue
The University of British Columbia: “Life Cycle Analysis of Electric Vehicles – Quantifying the Impact”, 2018 by Balpreet Kukreja
Eindhoven University of Technology, Netherlands: “Comparing the lifetime greenhouse gas emissions of electric cars with the emissions of cars using gasoline or diesel” , by Auke Hoekstra (2019 or 2020)
International Energy Agency (IEA): “Comparative life-cycle greenhouse gas emissions of a mid-size BEV and ICE vehicle“, IEA, 2021
Research Organizations
The International Council on Clean Transportation (ICCT): “A Global Comparison of the Life-Cycle Greenhouse Gas Emissions of Combustion Engine and Electric Passenger Cars”, 2021 by Georg Bieker
Union of Concerned Scientists: “Cleaner Cars from Cradle to Grave – How Electric Cars Beat Gasoline Cars on Lifetime Global Warming Emissions”, 2015 by Rachael Nealer, David Reichmuth and Don Anair.
Argonne National Laboratory, Argonne, Illinois, USA: “Life Cycle Analysis of Lithium-Ion Batteries for Automotive Applications”, 2019, Qiang Dai, Jarod C. Kelly, Linda Gaines and Michael Wang
IVL Swedish Environmental Research Institute: “Lithium-Ion Vehicle Battery Production”, 2019, Erik Emilsson, Lisbeth Dahllöf
Derek
