by Ankur Podder and Rhea Grover
figures by Jovana Andrejevic
Electric Vehicles (EVs) were once regarded as hopeless, tasteless, and incapable of replacing the fossil fuel-powered vehicles. In 2006, the award-winning documentary “Who Killed the Electric Car?” illustrated the impending obsolescence of EVs after a series of failed experiments by the automotive industry. The predicted doom didn’t stop environmentalists from pressing for the industry to make better EVs, however. Over the course of the next decade, the industry responded to these requests by rolling out EVs like Tesla Model 3 and Nissan Leaf as frontline products. These EVs fueled a new wave of strategies to combat the effects of climate change, and today, these vehicles strongly foreshadow the imminent end of fossil fuel-powered vehicles. The worldwide projection of EVs as mechanical messiahs begs us to ask the question: are EVs really as environmentally friendly as they seem?
Embodied energy emissions of EVs
Although EVs are purported to be energy efficient, the energy required to produce these vehicles is actually relatively high. EVs seem eco-friendly if we only consider their operating energy emissions, or the emissions produced while driving the car. For example, the fact that EVs have zero carbon dioxide (CO2) emissions during operation suggests that these vehicles are very eco-friendly. However, achieving zero CO2 emissions while driving EVs does not necessarily make them environmentally friendly because this metric does not account for embodied energy emissions.
Embodied energy is the sum of all the energy required to produce a product (including raw materials extraction, assembly, and transportation of the product), treating that energy as though it was incorporated or ’embodied’ in the product itself (Figure 1). The production of batteries and other EV components contributes to the majority of embodied energy emissions for these cars, as noted in this 2011 study. In fact, CO2 emissions related specifically to materials and EV assembly are higher than that of a traditional car. In the end, EVs do have lower total energy (embodied + operating) emissions as compared to traditional cars, making them more environmentally friendly overall. Being better, though, is not the same as being the best. These vehicles could be significantly more eco-friendly if we innovate to lower their unexpectedly high embodied energy emissions.
Innovative lightweighting of EVs
One of the reasons that the embodied energy emissions of EVs is higher than expected is because the materials required to make them are quite heavy, and thus their acquisition, processing, and transport leads to relatively high CO2 emissions. To render EVs as environmentally friendly as they are purported to be, we must devise novel methods to lower the amount of heavy materials required to produce EV components. One method is lightweighting: a process that makes products lighter by reducing the amount of materials used to make them. Using fewer materials reduces embodied energy emissions in the stages of material extraction, transportation, and assembly. As part of their EV Everywhere Grand Challenge, the U.S. Department of Energy (DOE) proposed to lightweight EVs by 2022, specifically reducing 35% of the weight of a car’s body structure, 25% of its base frame supporting the rest of the car, and 5% of its interior.
Various approaches to lightweighting EVs include transitioning to lighter materials (e.g. substituting strong but lightweight organic materials for heavier, more traditional materials like iron) and redesigning battery components with less heavy metals. Additionally, a breakthrough method of lightweighting is being devised by Volvo with the goal of integrating battery components into the vehicle body. According to Volvo, the future EV body (made of reinforced carbon fibers) would sandwich the battery components. These battery components would be molded and formed to fit around the car’s frame, such as its door panels, trunk door and wheel bowl (Figure 2).
All of these lightweighting techniques will require the use of novel, sturdy, lightweight materials. A recent material science study presents a proof of concept of using cellulose and carbon-fiber composites as materials that are strong enough but also light enough to achieve these lightweighting goals. However, these novel materials still need to be demonstrated at a commercial scale. According to the same study, organizations such as the Centre for Biocomposites and Biomaterials Processing (a materials science research center at University of Toronto) are actively working to achieve success on this front. They have demonstrated that using cellulose and carbon-fiber composites instead of traditional materials like steel could reduce the weight of a vehicle by 15 to 30%. Such innovation at a commercial scale would make lightweighting a logical game-changer in the reduction of embodied energy emissions of EVs.
EVs without lightweighting: More raw material extraction
In addition to lowering the embodied energy emissions of EVs, lightweighting will also have an impact on the sustainability of EV production. Specifically, many of the materials used to achieve lightweighting are polymers that can be synthesized in laboratories. Some examples are polypropylene, polyurethane and polyvinyl chloride (these three can be used for approximately 66% of EV parts). This is in stark contrast to the traditional, heavier materials used to make EVs, such as lithium, cobalt, manganese, and nickel. These raw materials must be mined and extracted from the earth prior to use, making them a less sustainable option than lightweighting materials. Until our goals of lightweighting are achieved at a commercial scale, EVs will continue to depend on these heavy materials, thereby maintaining the need for continual raw material extraction.
According to a study by U.S. Geological Survey, the U.S. already imports many of these rare earth minerals from other countries each year, adding to the increasing mining dependency for EVs. As EV demand increases in the future, existing mining locations may become overexploited. Mining areas in Argentina (with 9 million tons of lithium resources), India (for manganese), Japan (for nickel), China (for carbon), and conflict zones of Democratic Republic of Congo (for cobalt) could face more pressure of resource extraction to meet these demands. Notably, these lands are natural habitats rich in flora and fauna, and mining these areas could harm their habitats. If mining practices in these lands are left unregulated, there could be a high environmental price to pay.
The Gigafactory approach: Source globally, produce locally
Besides lightweighting, embodied energy emissions can also be lowered by transitioning from shipping batteries and other EV components over long distances to producing them locally, closer to where the EV is assembled. The United States International Trade Commission reported that the U.S. was the second highest importer of lithium-ion batteries (the batteries used in EVs) from 2013 to 2017, with $2.5 billion worth of lithium-ion batteries imported in 2017 itself. There is a hidden environmental cost here, associated mainly with emissions from commercial container ships. Thus, producing batteries and EV components locally at EV factories could help reduce these emissions. The good news for the U.S. is that Tesla’s Gigafactory, a massive EV assembly factory, will also produce lithium-ion batteries. The novel factory aims to account for 60% of global lithium-ion battery production by 2020. The Nevada Gigafactory produced over 20 gigawatt hours (GWh) worth of batteries in 2018 (in collaboration with Panasonic) while hoping to generate 35 GWh once fully operational. Once this is achieved, the U.S. would no longer need to import batteries but only source raw materials from existing global trade ties, thus decreasing energy expenditure on heavy battery transport (Figure 3).
Future opportunities for making EVs truly ‘green’
Reducing embodied energy emissions requires government support in establishing a framework of rules and regulations to ensure cost-effective, energy-efficient, and environmentally-friendly practices of raw material extraction and global transportation for EV components. Research investment in lightweighting EVs and environmentally-friendly manufacturing of EVs can be promoted through appropriate policy measures. Reducing embodied energy emissions from EVs, coupled with expanding our use of public transit systems and eco-friendly living decisions (like choosing to walk rather than drive), can accelerate humanity towards the bigger goal of a fully low-carbon civilization.
Ankur Podder is a second-year student of Master of Science in Architecture Studies (SMArchS) Urbanism program at Massachusetts Institute of Technology (USA) researching embodied energy and design.
Rhea Grover is a first-year Master’s student in English Language and Literatures program at University of Delhi (India) researching ecocriticism and policy.
Jovana Andrejevic is a third-year Applied Physics Ph.D. student in the School of Engineering and Applied Sciences at Harvard University.
For more information:
- For a review of embodied energy emissions, check out this description from Smarter by Nature
- To learn more about how composite materials may contribute to lightweighting, check out this paper from Scientific Research
- To find out how eco-friendly your EV is, use this online tool
- For more information on the EV battery supply chain, check out this paper from the US International Trade Commission
- To learn more about battery components and sources, see this piece from The Conversation
- To read about how cargo ships and oil tankers may be able to evade attempts to regulate carbon emissions, check out this article from Clean Technica
- For information about challenges faced by Tesla’s Gigafactory, see this blog post
- To learn about how the U.S. relies on other countries for mineral resources, see this description from the United States Geological Survey
- For information about how trade policy is impacting EV distribution, see this piece from The International Centre for Trade and International Development
- For more on Tesla’s Gigafactory, see this Verge article
This article is part of our SITN20 series, written to celebrate the 20th anniversary of SITN by commemorating the most notable scientific advances of the last two decades. Check out our other SITN20 pieces!