How Clean are Electric Cars? A Life Cycle Assessment of Advanced Vehicle Technologies

, , former engineer and Kendall Science Fellow | September 18, 2014, 10:03 am EST
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As electric vehicles (EVs) gain popularity in the United States and policies to encourage EV sales are implemented, significant research has been done on reductions in global warming emissions and oil use associated with operating them. This includes research published in the Union of Concerned Scientists’ report State of Charge. However, the broader impacts of EV production and recycling remain less well characterized, and are important when assessing the total environmental impact of consumer vehicle choices.

The importance of life cycle assessment

Life cycle assessment (LCA) is a method to analyze the total impacts of a good or service. This analysis is often termed “cradle-to-grave” as it includes the extraction of raw materials used to make a product all the way to the disposal or recycling of the product at the end of its useful life.

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This post is part of a series on National Drive Electric Week.

The impacts most commonly measured are costs, energy, and emissions. The LCA of costs is a standard business tool, as accounting for all the costs of a good or service is necessary to determine if a good or service will be profitable and competitive. More recently, energy and emissions have become a larger part of the LCA dialogue spurred by growing concern of climate change and local health impacts.

LCA is important because it helps decision makers (whether policy makers, businesses, or consumers) better understand the true impacts of a given good or service. When the goal is to optimize or reduce the total costs, energy, or emissions, it is critical to look at the process holistically to avoid negative tradeoffs and unforeseen consequences. More information on this can be found in my previous LCA post.

Applying LCA to advanced vehicles

The largest source of global warming emissions from conventional internal combustion engine vehicles comes from the tailpipe when the vehicle is in use. Battery-electric and fuel cell vehicles, on the other hand, do not have an internal combustion engine and thus generate no global warming emissions during operation. However, there are emissions associated with production of EVs and the fuel used to power them (electricity or hydrogen) that would increase the total global warming emissions associated with using the vehicles.

Emissions from fuel production

Regardless of whether EVs run partially or fully on electricity, producing the electricity used to charge them can generate global warming emissions. In State of Charge, my colleagues found EVs’ global warming emissions vary significantly based on the mix of energy sources used to power a region’s electricity grid. And just recently my colleague updated the main findings with the most current electricity data. Overall, the report finds, nationwide, EVs charged from the electricity grid produce lower global warming emissions than the average new compact gas-powered vehicle (with a fuel economy of 28 miles per gallon)—even in regions powered primarily by coal.In regions with greater proportions of renewable energy resources, EVs produce fewer global warming emissions than even the most fuel-efficient hybrids.

Emissions from manufacturing and recycling

Since the State of Charge report, questions around EVs’ manufacturing- and recycling-related global warming emissions have become more prominent. While recent research suggests the additional components required for EVs (e.g., large battery storage) increase life cycle emissions, the increase is not sufficient to negate the environmental benefits of EVs over their lifetimes. Most studies agree U.S. EVs are cleaner than conventional vehicles, but how much cleaner is still being researched. However, the relative importance of manufacturing and recycling to overall vehicle emissions increases as cleaner sources of electricity generation are added to the grid and the emissions generated by using EVs decreases. In addition, mass-market EVs are in an early stage of deployment and new EV models with different technology approaches (e.g., range, battery chemistry, body design and materials) are rapidly entering the market. Manufacturing processes are likely to evolve and mature over the coming years, as are recycling processes that could change the amount of EV materials being recycled, reused, or scrapped.

At UCS I am investigating the impacts of current and future trends in manufacturing and recycling EVs in order to more fully assess the current and potential future emissions of these vehicles over their entire life cycle. This research, along with fuel-production research already published, is critical to determining how much EVs can contribute to reducing global warming emissions and oil use. So stay tuned!

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  • Markus

    Hi Rachael
    In case you haven’t seen this (because its in German), you may find this report interesting: http://www.empa.ch/plugin/template/empa/*/104369
    (if you cannot find anyone to translate it for you, let me know).
    I look forward to reading your report.
    Cheers
    Markus
    PS: I am in the process of setting up an organisation connecting consumers with science based environmental information on consumer products and services. If you or anyone else on this forum would be interested to provide some feedback on the Beta site, I’d be grateful – please get in touch at info@envormation.org

    • rnealer

      Thanks for your comment, Markus!

  • rnealer

    Thanks for all the great comments! These are all issues that I’m looking into, so stay tuned to my blog for more discussions and look forward to my report in the coming year.

  • Martin

    Don’t overlook the tremendous strain these EVs put on our rare earth resources. The rare earth metals, essential to manufacturing those massive batteries that power EVs, are aptly named – they are excruciatingly rare and, worse, most are mined from deposits in communist China, who controls and profits from a parsimonious global distribution. Sure, carbon dioxide in our atmosphere is the trendy concern but it should not be studied to the exclusion of old-fashioned natural resources conservation. When we’ve finished digging massive holes in the earth to mine out the last of the rare earth metals that wasteful travesty will be the eternal legacy of our contemporary battery operated personal transportation.

    • UCSBcpa

      “Rare Earth” metals are not rare at all. There are deposits dotted everywhere on the planet. Also, wholes in the earth will be done without one second of concern for “rare” Earth metals, why you ask: because all Rare Earth metals are co-products of the real reason the whole is being dug. Find a whole for copper and you will find a tiny amount of “rare” Earth metals…..whole will be dug without concern for this margin of a product.

  • Basil van Rooyen

    There is no mention of the advantages in source emissions of the plug-in hybrid vehicle (PHEV) vs the EV, since these have smaller batteries for only average daily commuting – about 30 mi. This smaller battery allows charge-ability from a domestic outlet (no fast-charge infrastructure required) and overnight from say 10pm on off-peak power – when dirty power stations cannot switch off – so no EXTRA emissions are created despite charging all autos in the US as PHEV’s. The commutes longer than average would total under 10%, when the small range-extender combustion engine would produce normal emissions for current economical autos. See http://www.citsengine.com.au

    • rnealer

      Thanks for your comment, Basil!

    • UCSBcpa

      Strong comment! – thanks!

      My retort to this would be a question regarding where the batteries are being manufactured, for instance: note that countless data centers are huddled around essentially free energy – large dams, nuclear sites, etc.

      Those data centers (and other industries) are essentially not using any “extra” – as you put it – energy.

      I am not saying (maybe I am right, but need a lot of time to determine that) that all battery manufacturing plants are located on the Columbia River….but…if they could be, then the Rivers energy dump could go directly to this outlet. – Which would be great!

      Perhaps an ideal situation would be to build a massive battery plant not in Nevada but right next to an already built nuclear plant or large dam, so long as there was an excess power. And, it would be impossible to build solar and wind that could economically compete with the kWh prices from the Columbia River…..

      Great comment, none the less!

      • Basil van Rooyen

        UCSBcpa – Martin ? Your hopes of batteries being charged near dams or nuclear power plants are admirable – but as autos will be charged at home and globally, reality takes over. The source of power generated in US, UK, Russia, China, Australia, Poland, Germany, Canada, South Africa to name a few, is over 50% from fossil fuel, creating CO2 – so I hope you will allow my previous statement to stand. PHEV is the transition auto format for the next decade or two until nuclear, Hydro, wind and other clean sources replace dirty generators. And even that needs the three innovations referred to in http://www.citsengine.com.au – if it is to reach the mass auto market of under $20,000. i.e. in-wheel electric motor, new batteries in the pipeline, and the CITS range-extender IC engine or one that can halve the present cost per kW