Are Electric Vehicles Really Greener than Internal Combustion Engine Vehicles?

This story is contributed by Prof. Ramesh K. Guduru and Raghavender Tummala

• Inefficient Li-ion battery recycling technologies will be detrimental to the sustainability of BEVs.
• The adoption of Battery Electric Vehicles (BEVs) over Internal Combustion Engine Vehicles (ICEVs) varies by country and the reduction in carbon emissions is strongly dictated by the power generation technologies of that country.
• The energy consumption and greenhouse gas emissions are significantly higher during the battery pack manufacturing stage of BEVs than the ICEVs and hence recycling is mandatory to realize the real benefits of BEVs over ICEVs.

Figure 1: Sustainability in life cycle of ICEVs vs. BEVs

The introduction of electric cars into the automobile sector has paved the way for cleaner and greener technologies all over the world. Although many countries in Asia and Europe have pledged to reduce their CO2 emissions by implementing cleaner technologies, questions remain on how green electric automobiles truly are. This is highly debatable primarily because it depends on the production of electricity in different nations. For example, electric vehicles are easily justifiable in countries that produce a majority of their electricity from greener and fossil-fuel free (e.g., nuclear and hydroelectricity) technologies. Currently, the European nations have been focusing more on greener technologies for the production of their electricity. On the other hand, developing nations like India and China produce the majority of their electricity from coal and have become major contributors to the global emissions of CO2 due to the rapid growth of their economies. Thus, implementation of electric vehicles under these two extreme scenarios needs to be better understood for the eventual reduction of global emissions. In performing this analysis and comparison, CO2 emissions should include those associated with pre-use i.e., during manufacturing, in-use i.e., while driving, and post-use i.e., after the life of the ICEVs and BEVs.

A recent report by Transport & Environment [T&E] [1] has provided an excellent analysis of how green the electric vehicles are under the best and worst case scenarios. With several critical factors from this report in mind, we look at the sustainability of ICEVs from a different angle. To illustrate this, we compare the CO2 emissions of same size cars using ICEV and BEV technologies.

Figure 1 shows a parallel comparison of ICEVs and BEVs from manufacturing to recycling or end of life in four stages. When carrying out this analysis, it is necessary to understand the life cycle analysis (LCA) of battery packs as well, see Fig. 2, because battery recycling will be a huge concern when the whole world adopts electric vehicles not only in the transportation sector but also in other industries, such as aviation, manufacturing, indoor utility vehicles and consumer products. The LCA of batteries is detailed in Stage — 4 emissions about post-use.

Figure 2: Life cycle of a battery from cradle to end of life.

In pre-use, the CO2 emissions generated during the production of both ICEVs and BEVs as well as the transportation of fuel from the well to the tank in ICEVs, and manufacturing and integration of battery packs in BEVs are considered. We further divide pre-use emissions into manufacturing and fueling as shown in Fig. 1.

Stage 1: Emissions during the manufacturing of ICEVs and BEVs

Based on T&E’s report and other studies [1], the powertrain in ICEVs is much heavier and energy intensive than the electric powertrain. Per Knobloch’s [2] estimates, 9200 kWh of electricity is required for producing a medium size car of 1600 kg, equivalent to 5900 kg of CO2 emissions. Per T & E’s estimates [1], production of electric cars without the battery pack is about 10.7% less carbon intensive in terms of energy used compared to the production of ICEV equivalents. This certainly benefits the greenness of BEVs over ICEVs.

Stage 2: Emissions during energy transfer

In this stage, for ICEVs, the emissions associated with fuel supply until the tank are considered. In the Well-to-Tank (WTT) CO₂ upstream or indirect emissions, which includes emissions starting from drilling/extraction and processing/refining all the way through transportation to the gas station. As per Knobloch et al.’s LCA analysis [2], tailpipe emissions increase by 28% for diesel and 26% for gasoline and is equivalent to 0.735 kg CO2 equivalent/Liter and 0.614 kg CO2 equivalent/Liter, which in turn correspond to 73.7 g CO2 equivalent/kWh (Diesel 1 L ~ 10 kWh) and 69.8 g CO2 equivalent/kWh (Petrol 1 L ~ 8.8 kWh), respectively.

In the case of BEVs, emissions during battery pack manufacturing before integrating with the vehicle need to be thoroughly considered. According to Maeva Philippot et al.’s report [3], battery pack manufacturing has two important variables. The first is the country of manufacturing and the second is the volume. In countries like China, where the majority of the electricity is produced by fossil fuels (hard coal), battery pack manufacturing results in higher amounts of CO2 emissions per kWh (~160 kg CO2 equivalent/kWh). In countries like France and Sweden, where the majority of the electricity is produced by hydropower and nuclear energy, battery pack manufacturing results in ~ 80–90 kg CO2 equivalent/kWh, almost half of the emissions in China. Thus, the electricity generation technologies of a country will have a major impact on the carbon emissions of battery pack manufacturing in BEVs. With volume production, as the number of cells increases from 7x107 to 2x109 the emissions drop almost by 30%. Therefore, it may be premature to assign a specific number to the emissions for battery pack manufacturing in any given country while the production of BEVs is still ramping up. However, it is very clear that the amount of CO2 emissions per battery pack manufactured in a country is dictated by the power generation technologies of that particular nation.

The above data clearly shows that the battery pack manufacturing results in significant emissions compared with the WTT of fossil fuels. This contradicts with the current perception of the sustainability of BEVs over ICEVs.

Stage 3: In-Use Emissions

ICEV tailpipe emissions from the combustion of fossil fuels is accounted for in this stage. For the amount of power required, around 404 g of CO2 emissions are released per mile driven for an average passenger ICEV [4]. Although this stage appears to favor electric vehicles due to their lack of emissions, it is necessary to take into account the following three sources of CO2 emissions for an unbiased comparison between ICEVs and BEVs:

• Transmission losses from the power plant to the charging port of the vehicle are usually around 7%. [1]
• Power losses in the charging equipment amount to 5%. [1]
• The amount of energy required to drive the BEV the same number of kilometers as an ICEVs and the associated CO2 emissions during the generation of that energy also need to be taken into account.

In addition, the technologies for electricity production must also be considered to assess the sustainability of BEV usage in a particular country. For example, in 2019, China emitted ~ 900 g of CO2 per kWh energy produced [5]. This would be equivalent to ~ 1018 g of CO2 per kWh of electricity usage in BEVs after accounting for power losses during the transmission and charging stages. Given that the average power consumption efficiency of BEVs is ~ 0.33 kWh/mile [6], around 336 g of CO2 emissions are released per mile driven. In contrast, France and Sweden emit only 105 and 47 g of CO2 per kWh of electricity produced, respectively in 2018 [7] and hence ~ 39 and 18 g of CO2 are released per mile driven by BEVs in these two nations, respectively, after accounting for all the losses. Thus, BEVs have significantly lower indirect CO2 emissions compared to ICEVs in both France and Sweden (~ 936% and 2145% less carbon intensive in France and Sweden), whereas they are only ~ 16% less carbon intensive in China. Although the CO2 emissions of BEV usage is very much dependent on a country’s electricity production technologies, BEVs are still generally greener than ICEVs in the usage stage.

Stage 4: Post Use Emissions

With the increase in demand and usage of BEVs every day, there is an absolute need for lithium-ion battery materials, both inactive components and active materials, which have a significant CO2 impact on the environment. Hence, the recycling of lithium-ion batteries after reusing BEV packs for a second life as grid storage has been a topic of research and commercialization in many countries. While production of the materials may cause around 50% of the GHG emissions [8], the use of recycled materials can decrease the energy demands of materials production by 48% [9]. Various recycling techniques like pyrometallurgy, hydrometallurgy, a combination of both or direct recycling processes (magnetic separation or air ballistic separation of components) have proven that these technologies were able to recover materials like steel, nickel, aluminum and plastic to a certain extent. However, the major active materials, such as lithium, manganese, carbon, and fluorine, are not fully recoverable even with a combination process [10]. In addition, some recycling processes also have a negative effect on the environment, such as pyrometallurgical and hydrometallurgical processes, which produce greenhouse gases while in operation. The overall efficiency of recycling is also dependent on the energy consumed and the amount of GHG emissions produced. According to H. Hao et al. [11], recycling of a battery pack (alone) in BEVs in China account for 13.6% of the total energy consumed in the full vehicle recycling, see Fig. 3, and correspondingly contribute to 12.6% of GHG emissions. Thus, the recycling of battery packs is an additional contributing factor to CO2 emissions for BEVs when compared with ICEVs even though recycling of the vehicle bodies in both the cases should be comparable. Therefore, recycling of BEV battery packs can never be greener than ICEVs. However, the recycling efficiencies can be improved by developing new processing techniques for other cell components like graphite, aluminum, and electrolyte, and with the use of recycled materials, the overall GHG emissions in post use life can be reduced by 50% across the battery production process making it a significantly more sustainable process [12].

Conclusions

The energy consumption and CO2 emissions in different stages from cradle to grave are analyzed and BEVs and ICEVs are compared at each stage. While the manufacturing of BEVs is 10.7% less carbon intensive than that of ICEVs in Stage — 1, battery pack manufacturing in Stage — 2 is highly carbon intensive and needs revolutionizing technologies to cut down the CO2 emissions. Although scaling the production of battery packs could reduce the emissions by a considerable margin (30% for scaling up by two orders of magnitude), this would likely happen only after greater adoption of BEVs globally. During usage in Stage — 3, BEVs prove to be greener than ICEVs and the extent of this difference depends significantly on how electricity is produced in those countries. In Stage — 4, current recycling technologies have high GHG emissions and require heavy innovation if global adoption not only BEVs perspective but also other battery applications, such as consumer electronics, is to be sustainable. At the same time, innovations in this stage could significantly reduce emissions during battery pack manufacturing in Stage — 2 where the BEVs are causing dramatically more CO2 emissions then ICEVs. The sustainability advantage of BEVs over ICEVs is smaller than might be perceived due to CO2 emissions over the life cycle of BEVs and Battery Packs, which is heavily dependent on emissions from power generation. BEVs still have a long way to go to achieve their promised vision of sustainability over ICEVs irrespective of country.

Authors

Ramesh K. Guduru is an Associate Professor, and Energy and Environmental researcher in India. Prior to that he worked as a faculty member at Lamar University in Texas, USA, and also as adjunct faculty at the University of Michigan, MI, USA. His research focuses on the Energy — Environment — Food nexus with an emphasis on batteries and supercapacitors with multivalent electrolyte chemistries, CO2 capture, Water Treatment and Hydrogen. He is actively applying nanotechnology to Energy — Environment — Food research. Dr. Guduru obtained his Ph.D. in Materials Science and Engineering from NC State University, Raleigh, USA.

Raghavender Tummala is a Research Project Leader for the Solid-State Battery team at Somnio Global, MI USA. He has more than twelve years of academic research and industrial experience in the development of rapid manufacturing systems for fabricating tailored nanopowders and thin films for energy storage and solar applications. He holds a Masters’ Degree in Mechanical Engineering and another Masters’ Degree in Automotive Systems Engineering from the University of Michigan.

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References:

1. Article: “How clean are electric cars? T&E’s analysis of electric car life cycle CO₂ emissions”, A briefing by T&E, 2020
2. Florian Knobloch et al., “Net emission reductions from electric cars and heat pumps in 59 world regions over time”, Nature Sustainability, 2020, 3, 437–447
3. Maeva Philippot et al., “Eco-Efficiency of a Lithium-Ion Battery for Electric Vehicles: Influence of Manufacturing Country and Commodity Prices on GHG Emissions and Costs”, Batteries, 2019, 5, 23
4. Report: “Greenhouse Gas Emissions from a Typical Passenger Vehicle”, Office of Transportation and Air Quality, [EPA-420-F-18–008] 2018
5. Report: “China’s Emissions Trading Scheme, Designing efficient allowance allocation”, IEA, 2020
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9. Hans Eric Melin, “Analysis of the climate impact of lithium-ion batteries and how to measure it”, Circular Energy Storage, 2019
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