Electric vehicles and their role in our decarbonisation ambitions
In order to achieve its goals of reducing greenhouse gas emissions, air pollution, noise and dependence on oil, Europe has recognized the electrification of road transport as a priority, pushing for legislation and providing incentives to drive demand for electric vehicles. However, every once in a while, a new study makes the news with headlines such as “Electric cars have a dirty little secret”, or “Electric cars aren’t as green as you think they are”. So, what does the actual research suggest?
By Francisco Correia da Fonseca
Decarbonising road transportation
Today, road transportation based on highly-pollutant internal combustion engines is in urgent need of a major reform. Just in 2015, conservative estimates indicate that global transportation was responsible for 385 thousand to half a million premature deaths, and $976 billion in welfare loss due to air pollution alone [1,2]. These values do not account for the catastrophic impacts of climate change on human and wildlife, to which road transport is responsible for almost one fourth of Europe’s greenhouse gas emissions [2]. According to the World Health Organisation, between 2030 and 2050, climate change will be responsible for approximately 250,000 additional deaths every year [3,23].
During the last decade, electric cars have become more appealing than ever, in a world where carbon emissions, pollution, and sustainability are growing concerns for many people. During this time, technology has made impressive advances. According to McKinsey[4], the cost of batteries fell from $1000 in 2010, to $227/kWh in 2016, and it is expected to fall below $100 by 2030. Battery capacity also increased sharply, as many new electric vehicles (EV) today have driving ranges around 400km, making EVs also useful for inter-city commuting.
However, an important issue regarding electric vehicles is the environmental friendliness of EV batteries. The manufacturing of lithium-ion car batteries is an energy and carbon intensive process, and the materials used are toxic and hard to dispose. Lithium mining requires immense quantities of groundwater, and the impacts on the environment and human health include water depletion and contamination, toxicity impacts on flora and fauna, waste generation, and land subsidence (due to the large amounts of groundwater extraction), despite the documented socio-economic benefits derived from increased revenues to the state and profits for national and foreign companies [5, 6].
One must therefore ask: “Looking at the big picture, weighting the trade-offs for the entire lifecycle (i.e. from manufacturing to dismantling) of both electric and combustion engine vehicles, does transitioning to electric vehicles make environmental sense?”
Decarbonisation potential of electric vehicles — Debunking flawed arguments
Today, it is well established that electric vehicles can and will contribute to our decarbonisation efforts, having “significantly lower impacts on the climate” when compared to ICEVs [7]. However, every now and then, less thorough studies arrive to a different conclusion. Recently, a new study has compiled a list of erroneous assumptions that flawed studies typically make [8].
The first flawed assumption is the exaggeration of Green House Gas (GHG) emissions during manufacturing. These assumptions are commonly based on a single, highly controversial study from 2017, which was debunked and revised by the authors later in 2019. Today there is a consensus that GHG emissions in battery manufacture assume a range of 40 to 100 kgCO2/kWh, below the previously reported 175 kgCO2/kWh of battery [8]. It follows that, even though battery-powered electric vehicles have higher emissions than conventional vehicles during the manufacturing stage, this “debt” is paid on average after 1.5–2 years, depending on the penetration of renewable energy in the electricity grid [9]. As importantly, the environmental footprint of the battery production is expected to further reduce with time as technology matures.
A second common assumption that affects the perceived sustainability of electric vehicles is the battery lifetime, which is arbitrarily assumed as 150'000 km (in contrast to diesel cars which are assumed to last 300'000 km). However, recent research based on 6300 electric vehicles suggests that the observed battery degradation rates are consistent with the vast majority of batteries outlasting the usable life of the vehicle [10,17]. Longer battery lifetimes further amplify the decarbonisation potential of electric vehicles.
A third flawed assumption is related to the considered electricity mix. Naturally, the benefits of the electric vehicles are constrained by the carbon intensity of the electricity used to recharge the batteries of the vehicle. Countries with lower penetration of low-carbon energy generation are expected to experience lower positive effects. In order to simplify their calculations, many of such studies assume that the European electricity mix will remain the same in the next 20 years, which is a grave mistake (the GHG emissions per kwh of electricity are expected to lower from 269 g CO2eq/kWh in 2018 to 32 g CO2eq/kWh in 2040) [11]. The progressive decarbonisation of the electricity sector means that the already existent environmental advantages of electric vehicles will even amplify over time.
Finally, it is worth mentioning that diesel and petrol technologies are mature and with little room for improvement. Today it is well known that the emissions related to the production of gasoline and diesel are in reality much higher than previously thought, due to oil field flaring, methane leaks, and fuel distribution. In essence, when petroleum crude oil is extracted and produced from onshore or offshore oil wells, raw natural gas is also released from the ground. The cheapest and most commonly adopted solution is burning this gas, wasting it. On other occasions, that methane gas escapes to the atmosphere which is considerably more damaging to the environment. These aspects are typically not accounted for in comparative studies, despite adding about 24% and 30% to the vehicle’s tailpipe emissions, for diesel and gasoline vehicles respectively [8,19].
Environmentally speaking, are all electric vehicles the same?
In short, no.
Types of electric vehicles
Electric vehicles can be classified according to their operating principle and degree of electrification of their powertrain, while their environmental performance varies accordingly. In recent years, the definition of electric vehicle (EV) evolved to include all vehicles with an electric motor as the primary source of propulsion. This includes battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), extended-range electric vehicles (EREVs), and fuel cell (FCEVs). However, as schematized in Figure 4, this definition excludes the conventional non-plug-in hybrid electric vehicles (HEVs).
Hybrid Electric Vehicles (HEV) are powered by two engines: an internal combustion engine (ICE) and a small electric motor which uses energy stored in small batteries. They can be further divided into three types according to the degree of electrification and functionalities. Depending on the level of electrification of the HEV, the electric motor may provide brake energy regeneration but also power to the wheels when torque peaks are reached (mostly at start or at very low speeds). In HEVs, the batteries are recharged exclusively through brake regeneration and by the ICE. Today, conventional HEVs without plug-in are not included in the electric vehicle category.
Plug-In Hybrid Electric Vehicles (PHEV) are hybrid vehicles with the ability to recharge their batteries by plugging into an electric power source (a wall socket or EV charger). PHEVs typically have larger batteries and electric motors which allow them to transit using the electric mode only, although their electric range and speeds are limited (above a given speed, the ICE kicks in).
Battery Electric Vehicles (BEV) are fully electric vehicles with rechargeable batteries and no internal combustion engine. Their electric motor uses batteries that are recharged by plugging into an electric power source. Braking energy (which in conventional vehicles is dissipated through heat) can be partially recovered to recharge the batteries and slightly extend the vehicles range.
Extended Range Electric Vehicles (EREV) are essentially designed as BEVs, but integrated with an auxiliary power unit (called a range extender) which increases the EREV’s driving range. The range extender consists of an internal combustion engine connected to an electric generator, whose sole purpose is to recharge the electric batteries.
Finally, Fuel Cell Electric Vehicles (FCEV) use a propulsion system similar to BEVs. However, it has a hydrogen tank and a fuel cell that converts the chemical energy in hydrogen directly into electricity, powering the electric motor.
Differences in environmental performance
Pure electrics (BEVs) have been repeatedly shown to offer the lowest overall environmental footprint on most impact categories, including climate change (referred to as Global Warming Potential, or GWP, in Figure 6). However, hybrids (HEV, PHEV, E-REV) greatly vary [7,9,12,13].
Plug-in Hybrids are regarded as an important transitional technology as the world steers away from conventional ICEVs to full-electric BEVs. Presently, PHEVs account for about one third of the total number of electric vehicle worldwide, alleviating drivers range anxiety due to subpar battery ranges and underdeveloped charging infrastructure [14]. In urban environments, where vehicle speeds are low and accelerations are high, hybrid vehicles are capable of reducing fuel consumptions and emissions since internal combustion engines have characteristically low efficiencies under such conditions [15,16].
However, in real world conditions, the environmental benefits of plug-in hybrids are less obvious. One of the problems of hybrids is that the reductions in fuel consumption and emissions become negligible for long-distance trips as their all-electric range is limited, and their combustion engines typically kick in at higher speeds. Moreover, the owner’s driving and charging behaviour significantly affects the number of all-electric kilometres of hybrid vehicles. On top of that, in some cases, some PHEVs are designed for greater vehicle performance (greater accelerations and top speeds) and thus when driving in ICE-only mode (on an empty battery), the CO2 emissions may be actually worse than the vehicles they were designed to replace [18].
A new study by ICCT/Fraunhofer [13], based on approximately 100,000 PHEVs in China, Europe, and North America, has concluded that just a very small portion of the real world kilometres PHEVs is accomplished in electric mode (about 37% of the total kilometres at a worldwide level). This large study revealed that in real-world conditions, fuel consumptions of PHEVs were shown to be about 43–86% of the fuel consumption of comparable conventional vehicles. Yet, even though the achieved fuel savings were able to generate on average 15%–55% less tailpipe CO2 emissions compared to conventional cars, PHEVs were still shown to be producing on average two to four times higher emissions than their official values as advertised by car manufacturers [13].
Final thoughts
There is a lot of conflicting information regarding electric vehicles. Today, the decarbonisation potential of the large-scale adoption of battery-powered vehicles is very well documented. Studies that claim otherwise typically commit one or many of the methodological flaws previously described.
However, while the climate benefits of pure electric vehicles cannot be doubted, not all electric vehicles are the same. Despite offering significant logistic advantages, the environmental advantages of hybrid vehicles over conventional vehicles are not as high as initially thought. Even though it is true that if driven predominantly in their electric mode, hybrid vehicles can genuinely be low in emissions, large data statistics suggest that this is not always the case in real world conditions. Long-distance trips and the plug-in recharging frequency plays a big role on carbon footprint of PHEVs. Results also suggest that hybrid vehicle manufacturers have been exaggerating the environmental performance of their vehicles, vastly understating their fuel consumptions and CO2 emissions. This represents not only a carbon compliance trick, but most importantly a subsidy and tax loophole since some PHEVs have been unfairly benefiting from huge subsidies and tax benefits.
Despite offering some potential savings in carbon emissions, research suggests that the carbon footprint of plug-in hybrids may not be sufficiently low to achieve climate neutrality by 2050. This is particularly concerning since sales of plug-in hybrids are expected to massively increase in the next few years. Subsidies and tax incentives to electric vehicles must therefore be quickly revised in order to reflect their real contribution to our decarbonisation targets.
References
[1] Susan C Anenberg, Joshua Miller, Daven K Henze, Ray Minjares and Pattanun Achakulwisut, “The global burden of transportation tailpipe emissions on air pollution-related mortality in 2010 and 2015”, Environmental Research Letters, September 2019.
[2] Emisia, “ERTE2020: European Road Transport and Emissions Trends Report — For a sustainable future in road transport”, December 2019.
[3] World Health Organisation, “Climate change and health”, 2017, Available online at: http://www.who.int/mediacentre/factsheets/fs266/en/ (Accessed February 17, 2018).
[4] McKinsey, Electrifying insights — How automakers can drive electrified vehicle sales and profitability. Electrifying insights — How automakers can drive electrified vehicle sales and profitability_vF.ashx (mckinsey.com)
[5] Rennie B Kaunda, “Potential environmental impacts of lithium mining”, Journal of Energy & Natural Resources Law, May 2020, DOI: 10.1080/02646811.2020.1754596.
[6] Datu Buyung Agusdinata, Wenjuan Liu, Hallie Eakin, Hugo Romero, “Socio-environmental impacts of lithium mineral extraction: towards a research agenda”, Environmental Research Letters, November 2018.
[7] Ricardo Energy & Environment, “Determining the environmental impacts of conventional and alternatively fuelled vehicles through LCA”, Prepared for the European Commission — DG Climate Action, July 2020.
[8] Auke Hoekstra, Maarten Steinbuch, “Comparing the lifetime green house gas emissions of electric cars with the emissions of cars using gasoline or diesel”, Eindhoven University of Technology, August 2020.
[10] Auke Hoekstra, The Underestimated Potential of Battery Electric Vehicles to Reduce Emissions, Joule, Volume 3, Issue 6, June 2019.
[11] International Energy Agency (IEA), “Carbon intensity of electricity generation in selected regions in the Sustainable Development Scenario, 2000–2040 — Charts — Data & Statistics”, June 2020.
[12] Transport & Environment (T&E), “How clean are electric cars? — T&E’s analysis of electric car lifecycle CO₂ emissions”, April 2020, available online at https://www.transportenvironment.org/sites/te/files/downloads/T%26E%E2%80%99s%20EV%20life%20cycle%20analysis%20LCA.pdf
[13] Patrick Plötz, Cornelius Moll, Georg Bieker, Peter Mock, Yaoming Li, “Real-world usage of Plug-in Hybrid Electric Vehicles — Fuel Consumption, electric driving, and CO2 emissions”, 2020, The International Council on Clean Transport (ICCT).
[14] Sinan Küfeoğlua, Dennis K. K. Hong, “Emissions performance of electric vehicles: A case study from the United Kingdom”, Applied Energy, February 2020.
[15] F. Orecchini a , A. Santiangeli a , F. Zuccari a *, F. Ortenzi b , A. Genovese b , G. Spazzafumo c , L. Nardone, “Energy consumption of a last generation full hybrid vehicle compared with a conventional vehicle in real drive conditions”, Energy Procedia, September 2018.
[16] Patrick Moriartya, Stephen Jia Wang, “Can Electric Vehicles Deliver Energy and Carbon Reductions?”, 2017, Energy Procedia 105, pages 2983–2988.
[17] Charlotte Argue, What can 6,000 electric vehicles tell us about EV battery health?, GeoTab, July 2020.
[18] Transport and Environment (T&E), “Plug-in hybrids: Is Europe heading for a new dieselgate?”, November 2020.
[19] Auke Hoekstra, “Producing gasoline and diesel emits more CO2 than we thought”, Innovation Origins, February 2020
[20] Christian Bauer, et. al, “Opportunities and challenges for electric mobility: an interdisciplinary assessment of passenger vehicles”, Final report of the THELMA project in co-operation with the Swiss Competence Center for Energy Research “Efficient technologies and systems for mobility”, November 2016.
[21] Fabio Orecchini, Adriano Santiangeli, Alessandro Dell’Era, “EVs and HEVs Using Lithium-Ion Batteries”, Chapter 10, Lithium-Ion Batteries — Advances and Applications, 2014. Available online: https://www.sciencedirect.com/ science/article/pii/B9780444595133000108
[22] Amsterdam Roundtables Foundation, “EVolution — Electric vehicles in Europe: gearing up for a new phase?”
[23] Richard Parncutt, “The Human Cost of Anthropogenic Global Warming: Semi-Quantitative Prediction and the 1,000-Tonne Rule”, Frontiers in Psychology, Volume 10, pages 2323, October 2019. DOI: https://doi.org/10.3389/fpsyg.2019.02323
