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Capsule - What if all the gasoline cars became electric vehicles? Would there be more or less pollution?

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What if we could snap our fingers and turn all the gas powered cars in the US into electric vehicles [EVs]? Would there be more or less pollution?

Description

The number of electric vehicles in the U.S. (and the world) is growing quickly [7]. This growth is largely driven by a desire to decrease the negative impact personal motor vehicle transportation on the environment. It is pertinent to attempt to characterize the environmental impact of gas powered vehicles versus EVs. I present a simple attempt at calculating and comparing the emissions of gas powered vehicles in the U.S. versus EVs. The goal is to get a rough idea of the environmental impact of the two vehicle types as well as present it in a manner that is digestible to non-academics. This study uses data from published sources online for the various values used in the calculation. I ignore the potentially, important environmental impact of the manufacturing processes of the two types of vehicles. I describe the data used in the calculation, the calculation itself, and some basic conclusion and comparison to other studies.

Method

How do we calculate the amount pollution? In the interest of creating a tractable and clear result to a wide audience, I chose to start by comparing the amount of C02 produced per year if all the vehicles were of either all gas powered or all electric. This is a naive and simplistic approach but it is a starting point and allows us to highlight this very important aspect of the topic. Furthermore, these values are still relevant in more complex calculations which take into account other factors like manufacturing, maintenance, longevity, etc [9].

Data

There are roughly 282 million cars registered in the U.S. [2].

Gas vehicles burn about 150 billion gallons of gas per year in the US [1] and one gallon of gas burned by a car produces roughly 20 lbs of C02 [6].

The average EV uses 196 Wh/km [3] or 241.4 Wh/mile. We assume the average US car drives 14,000 miles per year [4]. Therefore, an EV uses about 3,379,600 Wh per year. That yields 953 Trillion Wh/per year consumed if all cars were EVs in the US. Electric vehicles receive energy from the US power grid which produces about 0.85 lbs of C02 per kWh [5].

Calculation

To estimate the total emissions produced by the two vehicle types we perform the following calculations:

For gas powered vehicles:

(gallons of gasoline per year)*(pounds of C02 per gallon of gas) = (total C02 per year)

specifically

150,000,000,000 gallons/year * 20 lbs C02/gallon = 3 trillion lbs C02/year

For EVs vehicles:

(number of vehicles)*(miles driven per year per vehicle)*(Wh per mile)*(C02 per kWh) = (total C02 per year)

specifically:

282,000,000 vehicles * 14,000 miles/(year vehicle) * 241.4 Wh/mile * 0.85 lbs C02/kWh = 810.1 billion lbs of C02/year

I predict a 73.0% decrease in carbon emissions if all vehicles in the US were EV instead of gasoline powered going from 3 trillion lbs of C02 to 810.1 billion lbs of C02.

We can see rough validation of the results by comparing to an entirely different study which presents us with two values for annual emissions for the two vehicle types [8]. Using these values we get 3.6 trillion lbs of C02 produced annually by gas powered vehicles and 794.4 billion lbs of C02 produced annually if all cars in the US were EVs.

We can also use 24.2 mpg as the average fuel economy for a gas powered vehicle in the U.S. [10]> to expand on our approach, slightly. Using this value we find a slightly largely value for total gallons of gasoline burned per year of 163 billion. Using this number we calculate the total carbon emissions for gas powered cars to be approximately 3.3 trillion. This comes closer to the values produced using the data in [8] and might be a more accurate result.

Conclusion

I predict that if all gasoline vehicles were replaced by EVs we would see total C02 produced drop from 3 trillion lbs per year to 810.1 billion lbs per year, a 73.0% decrease. Comparing this result using data from [8] we see a 77.9% decrease predicted. We consider this validation for such a simplistic, high level approximation with the goal of being understandable to people outside of academia. We performed a separate calculation using 24.2 mpg for the fuel economy for gas powered vehicles in the U.S. and calculated the total annual emission to be 3.3 trillion lbs. This value lands in between the previous two methods of calculating total annual gas emissions.

The predicted decrease in emissions is compelling but it is still important to expand on these of calculations to include more environmental effects that distinguish the impact of these two types of vehicles. The type of impact is most likely not completely characterized by carbon emissions alone [9].

created by wuliwong


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Links

  1. In 2020, U.S.
    U.S. gasoline & gasohol consumption by vehicles | Statista
  2. How many registered motor vehicles are there in the U.S.?Some 276 million vehicles were registered here in 2020.
    Number of motor vehicles in U.S. | Statista
  3. Energy consumption of full electric vehicles cheatsheet. Quick reference for all plug-in hybrid en full electric cars.
    EV Database
  4. Average miles driven per year
  5. Frequently Asked Questions (FAQs) - U.S. Energy Information Administration (EIA)
  6. This page answers questions about GHG emissions from passenger vehicles and how these emissions are measured and calculated.
    Greenhouse Gas Emissions from a Typical Passenger Vehicle | US EPA
  7. Although the global share of electric mobility is still small, the EV fleet is expanding quickly. Ambitious policy announcements have been critical in stimulating the electric mobility transition in major vehicle markets.
    Electric vehicles - IEA
  8. All-electric vehicles, plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs) typically produce lower tailpipe emissions than conventional vehicles do, and zero tailpipe emissions when running only on electricity. Tailpipe emissions are only one factor in considering a vehicle's life cycle emissions; gasoline and electricity fuel pathways also have upstream emissions to consider, which include extracting, refining, producing, and transporting the fuel. Estimating cradle-to-grave emissions must account for both fuel-cycle emissions (also known as "well to wheels") and vehicle-cycle emissions (material and vehicle production as well as end of life). The combined emissions from vehicle and fuel production through vehicle decommissioning (i.e., recycling or scrapping) are referred to as life cycle or cradle-to-grave emissions.
    Alternative Fuels Data Center: Emissions from Electric Vehicles
  9. Yes: although electric cars' batteries make them more carbon-intensive to manufacture than gas cars, they more than make up for it by driving much cleaner under nearly any conditions.
    Are electric vehicles definitely better for the climate than gas-powered cars?
  10. Alternative Fuels Data Center: Maps and Data - Average Fuel Economy by Major Vehicle Category