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Electric Vehicles: Will EVs make our climate better?

September 25, 2020

Electric vehicles have gained momentum in the recent years due to a considerable percentage of personal vehicle users as well as freight companies that converted from using internal combustion engine vehicles to some type of electric vehicles. Electric vehicles by definition, have at least some electric powerplant that powers the engine particularly or completely by one or more electric motors. This article forces on the environmental impacts of electric vehicles that entirely depend on batteries for storage and delivering  electric power for the motors.

Plug-in hybrid electric vehicles (PHEVs) are being developed for a decade or so for mass production by the automotive industry by some major automakers. However, the rise of Tesla, the most valued automaker at the moment during the time of writing this article,  have pushed the limit of how an average car user can adopt completely to an all electric car and thereby save the environment from massive carbon footprint resulting from fossil fuels. PHEVs do not use any type of fuel other than battery packs that store and deliver energy. PHEVs have been touted for their potential to reduce the transportation system’s petroleum dependence and greenhouse gas emissions by using off-peak excess electric generation capacity and increasing the vehicle’s energy efficiency. As such, PHEVs are in a massive boom as several other companies have emerged with large financial backings that have pledged to produce EVs to save the environment and to ensure a zero emission transportation system in the future. The burning question is of course: do EVs actually have a significant impact in the improvement of environment?

The U.S. Department of Energy’s has a Vehicle Technology Program that examines the precompetitive, high-risk research needed to develop the component and infrastructure technologies necessary to enable a full range of affordable cars and light trucks that are expected to reduce the U.S. dependence on imported oil and minimize harmful vehicle emissions, without sacrificing freedom of mobility and freedom of vehicle choice [1]. Although PHEVs are similar to the regular hybrid electric vehicles (HEVs), the battery can be charged using electricity from the grid by being recharged through a wall outlet. In terms of the overall environmental impact, PHEVs not only have direct impact as a result of not burning traditional fuels, but also the battery chemistry, the amount of grid electricity that can be stored in the battery, recycling ability of the raw materials, and the ability to give unused “power back to the grid” could significantly impact the environment. 

Below is a schematic showing the life-cycle for a typical EV from production to termination of usage. An EV, by its nature of production type as well as type of usage, typically have less carbon footprint in each lifecycle phase compared to that of a fossil fuel burning vehicle.

It is important to note that while PHEVs offer the potential for significant reduction in the usage of fossil fuel and resulting emissions of greenhouse gases, the actual benefit calculations need to take into account the upstream energy and emissions penalties that are associated with the electricity generation needed to power the charging systems and the load on the grid. Few studies have indeed taken all of these factors into account for certain vehicles that offer a choice of electric or internal combustion engine options for the same model. A study on the well known Volkswagen Golf model showed that, using the latest EU electricity mix, the current Golf TDI (Diesel) emits 140g CO2/km on average over its entire life cycle, while the e-Golf1 reaches 119g CO2/km. Based on the report, most of the emissions occur during the use phase of the internal combustion engine vehicle. Here the diesel reaches 111g CO2/km while a corresponding vehicle with electric drive emits only 62g CO2/km during the same phase [2].

Key findings about EV and carbon emission

  1. Several european countries where EVs are prevalent have significantly more carbon-intensive power generation – due to reliance on coal plants – EVs still perform better there on a lifecycle basis, which includes the emissions in manufacturing the battery and vehicle. Based on the Polish average, an EV emits 25% less CO2 over its lifetime. In Sweden, which has one of the cleanest energy mixes in the EU, an EV emits 85% less than a diesel car [3]. The figure below shows a summary of the study [3,4].

        EV Climate impact for different Energy Mixes (reproduced from Transport and Environment) 
  2. Replacing a traditional ride-hailing car with an electric vehicle would deliver three times the environmental benefits and emission reductions, according to a new study. The finding comes as a new cost analysis shows that e-vehicles are cheaper to run for Uber drivers in many European cities, and Uber in Portugal says it will only take on new drivers if they have an EV.
  3. Both Uber and Lyft have made recent statements expressing their intention to move towards a totally electric fleet. But now, for the first time, a study has looked at what the environmental impact might be. The study by University of California’s transportation institute, looked at 400,000 journeys made in a battery EV by 1,000 ride-hailing drivers, and compared the impact with 118,668 journeys made in a petrol or diesel car, as well as over 15,000 in a plug-in hybrid EV [5].
  4. The biggest finding is that the potential environmental and emission reduction benefits of replacing a ride-hailing traditional car with an EV are ‘approximately three times higher compared with those of regular vehicle usage in California’, and on emissions alone this was ‘the most pessimistic scenario’. This is because vehicles owned by Uber, Lyft and other ride-hailing drivers are driven more than if they were only used for private use (about 305km on average per day compared to 48km) [5].
  5. Below is a chart based on data from EPA in the US for greenhouse gas emissions by different sectors [9] . Based on the data, it can be seen that transportation sector contributes to a large amount of green house emission. It will be interesting to see the insights about how EVs and PHEVs come into play.
Share of Greenhouse Gas Emission by Sector

How to calculate carbon footprint:

Carbon offsetting funds solutions to reducing carbon emissions now. Frequently carbon offsetting reduces emissions much faster than you can as an individual/single company. Carbon offsetting projects help to combat global climate change as well as caring for local communities. In many instances providing much needed employment, health improvement, biodiversity,  reforestation and broad social benefits to impoverished communities.

Calculator:

This free to use online carbon calculator tool is independently audited on an annual basis as part of the Quality Assurance Standard (QAS) for Carbon Offsetting. 

https://www.carbonfootprint.com/calculator.aspx

Reference:

    1. Elgowainy, A., Burnham, A., Wang, M., Molburg, J., & Rousseau, A. (2009). Well-to-wheels energy use and greenhouse gas emissions of plug-in hybrid electric vehicles. SAE International Journal of Fuels and Lubricants, 2(1), 627-644.
    2. https://www.lowcvp.org.uk/news,vw-study-shows-co2-benefits-of-evs-over-whole-lifecycle_3946.htm (accessed October 2020)
    3. https://www.transportenvironment.org/press/electric-cars-emit-less-co2-over-their-lifetime-diesels-even-when-powered-dirtiest-electricity (Accessed September 2020)
    4. Messagie, M. (2014). Life cycle analysis of the climate impact of electric vehicles. Journal of Life Cycle Assessment, 2014, 14.
    5. Jenn, A. (2020). Emissions benefits of electric vehicles in Uber and Lyft ride-hailing services. Nature Energy, 5(7), 520-525.
    6. Noori, M., Gardner, S., & Tatari, O. (2015). Electric vehicle cost, emissions, and water footprint in the United States: development of a regional optimization model. Energy, 89, 610-625.
    7. Data from US Dept of energy: https://afdc.energy.gov/data/10347  (annual energy usage impact) (Accessed September 2020)
    8. https://afdc.energy.gov/data/10301  (US HEV sales by model) (Accessed September 2020)
    9. https://afdc.energy.gov/data/10802  (Green house gas emission by economic sector) (Accessed September 2020)
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About Author

I am a OMSCS student at Georgia Tech. I also have a BS and MS in Civil Engineering. My work experience is in transportation systems and traffic engineering. I live in Seattle, and love the beautiful Pacific Northwest. I have a passion for all things tech, and an avid motorsports and cricket fan.

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.