There is a lot of hype about electric vehicles. On the Internet you can find articles heralding electric vehicles as world saviors, due to reduced greenhouse gas emissions (GHGs). You can also find articles purporting to debunk that idea. Then you find articles debunking the debunkers, and so forth.

In 2014, I reported on a study comparing the lifetime carbon emissions of electric vehicles vs. gasoline powered automobiles. The study concluded that whether electric vehicles produced fewer greenhouse gas emissions depended on where you lived. If you drew your energy from an electricity grid with low carbon sources of electricity (translation: not generated by burning coal), your electric vehicle would produce fewer GHG emissions than would a gasoline powered vehicle. An electric vehicle consuming electricity that came from 100% renewable sources was the lowest emitting type of all vehicles. However, if you drew your energy from a grid with high carbon sources of electricity, then an electric vehicle was perhaps the worst kind of vehicle you could own, at least from the perspective of GHG emissions. (See here for my previous post.)

It has been 4 years. Perhaps it is time to look again. In this post, I’ll look conceptually at why an electric vehicle might be expected to have lower GHG emissions than a gasoline vehicle. In the next post, I look at some studies I was able to find, and report what they had to say.

A lifetime analysis considers all of the GHGs emitted by a vehicle during its entire lifetime. Typically they divide the life of a vehicle into 3 stages. First is the manufacturing: raw materials have to be mined, transported, processed, and refined. Then they have to be manufactured into parts. Then the parts have to be transported to the assembly plant, where the vehicle is put together. All of these stages consume energy, which means they emit GHGs.

Many of the components of gasoline and electric vehicles are similar in the amount of GHG emitted during manufacture. However, one component is not: gasoline cars store their energy in gas tanks, which are not especially energy intensive to build. Electric cars, however, store their energy in lithium-ion batteries. These batteries are energy intensive to build in all phases of manufacture: obtaining the raw materials, refining it, and constructing the batteries. Thus, in terms of manufacturing, the studies I have looked at agree that it is more carbon intensive to manufacture an electric vehicle than a gasoline vehicle. However, the largest area of uncertainty in the analysis of electric vehicles involves just how much GHG is emitted by manufacturing a lithium-ion battery. Estimates disagree.

Second, the vehicle is driven by its owner or operator. In this stage, the vehicle consumes fuel. Most studies agree that the fuel consumed by a vehicle is the largest source of GHG emissions during the life of the vehicle. Burning gasoline to power an internal combustion engine is relatively energy inefficient – only a fraction of the energy is used to move the vehicle down the road, the rest gets wasted. Further, it is not particularly clean. The result is that vehicles release a lot of GHGs (and also other forms of pollution). And finally, every time the vehicle stops, all of that wonderful energy moving the car down the road is dissipated into heat by the friction of the brakes. It is just thrown away.

Electric motors are much more energy efficient than are gasoline motors. Further, when an electric vehicle stops, it can recapture some of the energy of the moving car through regenerative braking. The recovered energy gets put back into the battery, and it is used to power the car the next time it starts moving. This is the advantage hybrid cars have, and it is why they get better gas mileage than do conventional cars. A Toyota Corolla (a compact gasoline burning car) will go 36 miles on the energy in a gallon of gas. On the other hand, a Nissan Leaf, an all-electric car, will go 112 miles on an equivalent amount of energy.

Further, an electric vehicle draws its energy from the electrical grid, where there is a much greater opportunity for the energy to be clean. To oversimplify the point, renewable energy (solar, wind, and hydro) are the lowest GHG forms of energy we have. Natural gas is next, then comes oil, and worst is coal. (I’ve left nuclear out; it is low GHG-producing, but it is objectionable for other reasons.) Electrical generators can be inefficient, just like gasoline engines are. However, there is a much greater chance that some of the electricity on the grid will come from clean sources. If it comes from coal, then the electricity on which the car runs will be particularly high in GHG emissions, although they will be emitted at the power plant, not the tailpipe of the vehicle. If it has a significant mix of solar, wind, hydro, or natural gas, then it will be lower in GHG emissions.

The third step involves disposing of and/or recycling vehicle components. The studies I have read suggest that the GHGs emitted from disposing of and recycling gasoline and electric vehicles are roughly equivalent, except for that pesky lithium-ion battery. There is some hope that in the future it can be effectively recycled or reused (it will still be suitable for many uses, just not powering a car). However, this is uncertain. Thus, as in manufacturing, the GHG emissions associated with disposing of and/or recycling an electric vehicle were estimated to be higher than those for a gasoline engine.

So, the question becomes: are the GHG savings from operating an electric vehicle more than the higher emissions during manufacture and disposal? And if so, by how much?

In the next post, I’ll look at some studies that try to answer that question.

Sources

Bureau of Transportation Statistics. 2016. Average Fuel Efficiency of U.S. Light Duty Vehicles. Downloaded 9/3/2019 from https://www.bts.gov/content/average-fuel-efficiency-us-light-duty-vehicles.

Department of Energy. 2019a. Emissions from Hybrid and Plug-In Electric Vehicles. Downloaded 9/2/2019 from https://afdc.energy.gov/vehicles/electric_emissions.html.

Department of Energy. 2019b. “Find and Compare Cars.” www.fueleconomy.gov. Viewed online 9/2/2019 at https://www.fueleconomy.gov/feg/findacar.shtm.

U.S. Energy Information Administration. 2019. Missouri State Energy Profile. Downloaded 90302019 from https://www.eia.gov/state/?sid=MO#tabs-4.

European Environment Agency. 2018. Electric Vehicles from Life Cycle and Circular Economy Perspectives. Downloaded 9/2/2019 from https://www.eea.europa.eu/publications/electric-vehicles-from-life-cycle/electric-vehicles-from-life-cycle/viewfile#pdfjs.action=download.

Kukreja, Balpreet. 2018. Life Cycle Analysis of Electric Vehicles. City of Vancouver. Downloaded 9/3/2019 from https://sustain.ubc.ca/sites/sustain.ubc.ca/files/GCS/2018_GCS/Reports/2018-63%20Lifecycle%20Analysis%20of%20Electric%20Vehicles_Kukreja.pdf.

Nealer, Rachael, David Reichmuth, and Don Anair. 2015 Cleaner Cars from Cradle to Grave. Union of Concerned Scientists. Downloaded 9/2/2012 from https://www.ucsusa.org/sites/default/files/attach/2015/11/Cleaner-Cars-from-Cradle-to-Grave-full-report.pdf.