The long tailpipe explained

The long tailpipe is an argument stating that usage of electric vehicles does not always result in fewer emissions (e.g. greenhouse gas emissions) compared to those from non-electric vehicles. While the argument acknowledges that plug-in electric vehicles operating in all-electric mode have no greenhouse gas emissions from the onboard source of power, it claims that these emissions are shifted from the vehicle tailpipe to the location of the electrical generation plants. From the point of view of a well-to-wheel assessment, the extent of the actual carbon footprint depends on the fuel and technology used for electricity generation, as well as the impact of additional electricity demand on the phase-out of fossil fuel power plants.

Description

Plug-in electric vehicles (PEVs) operating in all-electric mode do not emit greenhouse gases from the onboard source of power but emissions are shifted to the location of the generation plants. From the point of view of a well-to-wheel assessment, the extent of the actual carbon footprint depends on the fuel and technology used for electricity generation. From the perspective of a full life cycle analysis, the electricity used to recharge the batteries must be generated from renewable or clean sources such as wind, solar, hydroelectric, or nuclear power for PEVs to have almost none or zero well-to-wheel emissions.[1] [2] On the other hand, when PEVs are recharged from coal-fired plants, they usually produce slightly more greenhouse gas emissions than internal combustion engine vehicles and higher than hybrid electric vehicles.[1] [3]

Because plug-in electric vehicles do not produce emissions at the point of operation are often perceived as being environmentally friendlier than vehicles driven through internal combustion. Assessing the validity of that perception is difficult due to the greenhouse gases generated by the power plants that provide the electricity to charge the vehicles' batteries.[4] [5] For example, the New York Times reported that a Nissan Leaf driving in Los Angeles would have the same environmental impact as a gasoline-powered car with 79mpgUS compared to the same trip in Denver would only have the equivalent of 33mpgUS.[6] The U.S. Department of Energy published a concise description of the problem: "Electric vehicles (EVs) themselves emit no greenhouse gases (GHGs), but substantial emissions can be produced 'upstream' at the electric power plant."[7]

A recent study[8] by the German IfW shows that the increased electricity demand, and the resulting delay in the shutdown of coal-fired power plants in Germany, causes electric vehicles to have 73% higher emissions than Diesel vehicles.

Carbon footprint in selected countries

A study published in the UK in April 2013 assessed the carbon footprint of plug-in electric vehicles in 20 countries. As a baseline the analysis established that manufacturing emissions account for 70 g CO2/km. The study found that in countries with coal-intensive generation, PEVs are no different from conventional petrol-powered vehicles. Among these countries are China, Indonesia, Australia, South Africa and India. A pure electric car in India generates emissions comparable to a 20mpgUS petrol car. The country ranking was led by Paraguay, where all electricity is produced from hydropower, and Iceland, where electricity production relies on renewable power, mainly hydro and geothermal power. Resulting carbon emissions from an electric car in both countries are 70 g CO2/km, which is equivalent to a 220mpgUS petrol car, and correspond to manufacturing emissions. Next in the ranking are other countries with similar low carbon electricity generation, including Sweden (mostly hydro and nuclear power), Brazil (mainly hydropower) and France (predominantly nuclear power). Countries ranking in the middle include Japan, Germany, the UK and the United States.[9] [10] [11]

The following table shows the emission intensity estimated in the study for each of the 20 countries, and the corresponding emissions equivalent in miles per US gallon of a petrol-powered car.

Note that changes since 2013 will make significant changes to the figures, for example the UK emission factor for electricity in 2013 was 0.44546 kg/kWh,[12] by 2023 this had dropped to 0.207074 kg/kWh,[13] about 46% of the 2013 figure, which would move the UK into the "Low carbon" section.

Country comparison of full life cycle assessment
of greenhouse gas emissions resulting from charging plug-in electric cars and
emissions equivalent in terms of miles per US gallon of a petrol-powered car
CountryPEV well-to-wheels
carbon dioxide equivalent
emissions per electric car
expressed in (CO2e/km)
Power
source
PEV well-to-wheels
emissions equivalent
in terms of mpg US
of petrol-powered car
Equivalent
petrol car
align=left 70218mpgUSHybrid
multiples
align=left Iceland70217mpgUS
align=left 81 159mpgUS
align=left 89134mpgUS
align=left 93123mpgUS
align=left 115 Fossil light 87mpgUSBeyond
hybrid
align=left 146 61mpgUS
align=left 15557mpgUS
align=left 170Broad mix 50mpgUSNew
hybrid
align=left 175 48mpgUS
align=left 179 47mpgUS
align=left 18944mpgUS
align=left 202Fossil heavy 40mpgUSEfficient
petrol
align=left 203 40mpgUS
align=left 204 40mpgUS
align=left 258Coal based30mpgUSAverage
petrol
align=left 27028mpgUS
align=left 292 26mpgUS
align=left 318 24mpgUS
align=left 37020mpgUS
Note: Electric car manufacturing emissions account for 70 g CO2/km
Source: Shades of Green: Electric Cars’ Carbon Emissions Around the Globe, Shrink That Footprint, February 2013.

Carbon footprint in the United States

In the case of the United States, the Union of Concerned Scientists (UCS) conducted a study in 2012 to assess average greenhouse gas emissions resulting from charging plug-in car batteries from the perspective of the full life-cycle (well-to-wheel analysis) and according to fuel and technology used to generate electric power by region. The study used the Nissan Leaf all-electric car to establish the analysis baseline, and electric-utility emissions are based on EPA's 2007 estimates. The UCS study expressed the results in terms of miles per gallon instead of the conventional unit of grams of greenhouse gases or carbon dioxide equivalent emissions per year in order to make the results more friendly for consumers. The study found that in areas where electricity is generated from natural gas, nuclear, hydroelectric or renewable sources, the potential of plug-in electric cars to reduce greenhouse emissions is significant. On the other hand, in regions where a high proportion of power is generated from coal, hybrid electric cars produce less CO2 equivalent emissions than plug-in electric cars, and the best fuel efficient gasoline-powered subcompact car produces slightly less emissions than a PEV. In the worst-case scenario, the study estimated that for a region where all energy is generated from coal, a plug-in electric car would emit greenhouse gas emissions equivalent to a gasoline car rated at a combined city/highway driving fuel economy of 30mpgUS. In contrast, in a region that is completely reliant on natural gas, the PEV would be equivalent to a gasoline-powered car rated at 50mpgUS.[14] [15]

The following table shows a representative sample of cities within each of the three categories of emissions intensity used in the UCS study, showing the corresponding miles per gallon equivalent for each city as compared to the greenhouse gas emissions of a gasoline-powered car:

Regional comparison of full life cycle assessment
of greenhouse gas emissions resulting from charging plug-in electric vehicles
expressed in terms of miles per gallon of a gasoline-powered car with equivalent emissions[16] [17]
Rating scale
by emissions intensity
expressed as
miles per gallon
City PEV well-to-wheels
carbon dioxide equivalent
(CO2e) emissions per year
expressed as mpg US
Percent reduction in
CO2e emissions
compared with
27 mpg US average
new compact car
Combined EPA's rated
fuel economy and
GHG emissions
for reference
gasoline-powered car[18]
Best
Lowest CO2e emissions
equivalent to
over50mpgUS
align=left Juneau, Alaska112mpgUS315%2012 Toyota Prius/Prius c
50mpgUS
align=left San Francisco79mpgUS 193%
align=left New York City74mpgUS 174%
align=left Portland, Oregon 73mpgUS170% Greenhouse gas emissions (grams/mile)
align=left 67mpgUS 148% Tailpipe CO2Upstream GHG
align=left 58mpgUS 115% 178 g/mi (111 g/km) 44 g/mi (27 g/km)
Better
Moderate CO2e emissions
equivalent to between
41mpgUS to
50mpgUS
align=left Phoenix, Arizona48mpgUS78%2012 Honda Civic Hybrid
44mpgUS
align=left 47mpgUS 74%
align=left Houston46mpgUS 70% Greenhouse gas emissions (grams/mile)
align=left Columbus, Ohio 41mpgUS52% Tailpipe CO2Upstream GHG
align=left 41mpgUS 52% 202 g/mi (125 g/km)50 g/mi (31 g/km)
Good
Highest CO2e emissions
equivalent to between
31mpgUS to
40mpgUS
align=left Detroit38mpgUS41% 2012 Chevrolet Cruze
30mpgUS
align=left Des Moines, Iowa 37mpgUS37%
align=left St. Louis, Missouri 36mpgUS33% Greenhouse gas emissions (grams/mile)
align=left Wichita, Kansas35mpgUS30% Tailpipe CO2Upstream GHG
align=left 33mpgUS22%296 g/mi (184 g/km) 73 g/mi (45 g/km)
Source: Union of Concerned Scientists, 2012.
Notes: The Nissan Leaf is the baseline car for the assessment, with an energy consumption rated by EPA at 34 kWh/100 mi or 99 miles per gallon gasoline equivalent (99mpgus) combined.
The ratings are based on a region's mix of electricity sources and its average emissions intensity over the course of a year. In practice the electricity grid is very dynamic, with the mix of
power plants constantly changing in response to hourly, daily and seasonal electricity demand, and availability of electricity resources.
An analysis of EPA power plant data from 2016 showed improvement in mpg-equivalent ratings of electric cars for nearly all regions, with a national weighted average of 80 mpg for electric vehicles.[19] The regions with the highest ratings include upstate New York, New England, and California at over 100 mpg, while only Oahu, Wisconsin, and part of Illinois and Missouri are below 40 mpg, though still higher than nearly all gasoline cars.

Criticism

The long tailpipe has been the target of criticism, ranging from claims that many estimates are methodologically flawed to estimates that state that electricity generation in the United States will become less carbon-intensive over time.[20] Tesla Motors CEO Elon Musk published his own criticism of the long tailpipe.[21] The extraction and refining of carbon based fuels and its distribution is in itself an energy intensive industry contributing to CO2 emissions. In 2007 U.S. refineries consumed 39353 million kWh, 70769 million lbs of steam and 697593 million cubic feet of Natural Gas. And the refining energy efficiency for gasoline is estimated to be, at best, 87.7%.[22]

External links

Notes and References

  1. Book: Sperling, Daniel and Deborah Gordon . Two billion cars: driving toward sustainability . 2009 . 22–26 and 114–139 . Oxford University Press, New York . 978-0-19-537664-7 . registration .
  2. Book: Plug-In Electric Vehicles: What Role for Washington?. David B. Sandalow. David B. Sandalow. 2009. The Brookings Institution. 978-0-8157-0305-1. 1st.. 2–5. See definition on pp. 2.
  3. News: The Dirty Truth about Plug-in Hybrids, Made Interactive. Scientific American. July 2010. 2010-10-16. Click on the map to see the results for each region.
  4. Web site: Analyzing effects from well to wheel to air (the long tailpipe). Green Transportation. 20 December 2012. 27 Oct 2011.
  5. News: Hickman. Leo. Are electric cars bad for the environment?. 20 December 2012. The Guardian. 5 October 2012.
  6. News: STENQUIST. PAUL. How Green Are Electric Cars? Depends on Where You Plug In. 20 December 2012. New York Times. 30 April 2012.
  7. Web site: Electric Power. Energy Information Administration. U.S. Department of Energy. 21 December 2012.
  8. Web site: Electric Mobility and Climate Protection: A Substantial Miscalculation. Institut fuer Wirtschaftsforschung. 7 July 2020.
  9. News: India named least green country for electric cars . The Guardian. 2013-02-07. 2013-07-08.
  10. Web site: Véhicules électriques et émissions de – de 70 à 370 g /km selon les pays. French. Electric Vehicles and emissions - 70 to 370 g /km by country . Michaël Torregrossa. Association pour l'Avenir du Véhicule Electrique Méditerranéen (AVEM). 2013-03-21. 2013-07-08.
  11. Web site: Shades of Green: Electric Cars' Carbon Emissions Around the Globe. Lindsay Wilson. Shrink That Footprint. February 2013. 2013-07-08.
  12. Web site: Greenhouse gas reporting - Conversion factors 2013 .
  13. Web site: Greenhouse gas reporting: Conversion factors 2023 . 28 June 2023 .
  14. Web site: State of Charge: Electric Vehicles' Global Warming Emissions and Fuel-Cost Savings across the United States. Don Anair and Amine Mahmassani. . April 2012. 2012-04-16. pp. 16-20.
  15. News: How Green Are Electric Cars? Depends on Where You Plug In. Paul Stenquist. The New York Times. 2012-04-13. 2012-04-14.
  16. News: Carbon In, Carbon Out: Sorting Out the Power Grid. Paul Stenquist. The New York Times. 2012-04-13. 2012-04-14. See map for regional results
  17. News: When it Comes to Carbon Dioxide, Lower is Better and Zero is Perfect. Paul Stenquist. The New York Times. 2012-04-13. 2012-04-14.
  18. Web site: Compare side-by-side. U.S. Department of Energy and U.S. Environmental Protection Agency. 2012-04-13. 2012-04-15. Energy and Environment tab: cars selected Toyota Prius, Prius c, Honda Civic Hybrid, and Chevrolet Cruze automatical, all model year 2012.
  19. News: New Data Show Electric Vehicles Continue to Get Cleaner. 2018-03-08. Union of Concerned Scientists. 2018-08-26. en-US.
  20. Web site: Hall. Dean. Holes in the Long Tailpipe. neoHOUSTON. 21 December 2012. 5 Apr 2010.
  21. Web site: Musk. Elon. The Secret Tesla Motors Master Plan (just between you and me). Tesla Blog. Tesla Motors. 20 December 2012.
  22. Web site: Wang. Michael. Estimation of Energy Efficiencies of U.S. Petroleum Refineries. Argonne National Laboratory. 6 March 2016. Mar 2008.