In the last few years, multiple announcements have been made in several European countries for the phasing out of the sale of passenger cars with combustion engines, starting as soon as 2025 in Norway and followed by Sweden, Denmark, the Netherlands and Ireland in 2030. In parallel, automotive companies plan more and more to shift their product portfolio heavily towards battery electric passenger vehicles. As the phase-out of vehicles with combustion engines is mostly driven by the need to decarbonize the transportation sector to tackle climate change, one might derive from these observations that the environmental performance of electric vehicles, especially with regard to greenhouse gas emissions from the manufacturing, use and end of life phases of battery-electric cars, has finally been clarified.
But examining media publications about this topic leaves us with a rather ambiguous picture. I recently read an article in a weekly business magazine about a study commissioned by the Association of German Engineers (VDI) that, over their life cycle, battery electric vehicles are, in terms of greenhouse gas emissions, not any better than conventional passenger vehicles with combustion engines. A second weekly business magazine reported that the study was biased and used the wrong set of assumptions. What could be the reasoning for contradicting assertions about the ability to decarbonize the transportation sector with electromobility? Here we could respond with the common phrase used when determining the facts for solving complex challenges: Well, it depends!
It depends if the electric car is used in Norway with 100% hydro power in the power grid or in Poland with around 75% electricity from coal. It also depends on user behavior with regard to mileage, consumption and individual electricity supply. However, studies can compare apples to apples: we can work with the same set of comparative restraints, including the size of the car and its mileage/consumption. In doing so, we find significant differences in greenhouse gas emissions. This is especially the case for the manufacturing of batteries. Some of these differences might be related to the methodology used within the Life Cycle Assessment (LCA) or the carbon footprint used to analyze the greenhouse gas emissions of the manufacturing phase. Other differences have to do with the background data used to express the impact for the supply of materials and energy that can be found in Life Cycle Inventory (LCI) databases. But the majority of differences are related to the assumptions for the manufacturing of the battery itself.
Electric vehicle production is not a brand-new technology, by any means. The first electric vehicle was put on the street in 1881 by Gustave Trouvé in Paris. However, there has been tremendous development in the technology and production of electric batteries in the last decade. According to BloombergNEF, lithium-ion battery (LIB) prices decreased from 1.183 USD/kWh of battery capacity in 2010 to 156 USD/kWh in 2019, a reduction of more than 85%. A part of this cost reduction is related to lower capital and labor costs, which came about with the increase in production volumes of the battery cells. Another part of the reduction in cost is related to the increased energy densities of the battery cells, changing cell chemistries toward lower cobalt content and decreasing energy demand during precursor and cell manufacturing, clearly reducing the carbon footprint of lithium-ion batteries used in vehicles.
Within LCAs, it is not necessarily required to use the latest data for a particular technology, because it might not reflect the average production of, for example, a chemical like ammonia or methanol, as the average age of the manufacturing plant for such chemicals could be 10, 15 or 25 years. For a technology working with such developments, as the price reduction suggests for LIBs, the use of older data (that fails to refer to the actual situation), has a high potential to lead to misleading or arbitrary results. Examining the VDI study makes this more obvious. The study uses a NMC111 battery for an electric vehicle put out on the streets in 2020 and a NMC622 battery in 2030. We did not check the battery chemistry of every single electric vehicle that can be purchased today, but I doubt there is still any vehicle with a NMC111 battery. NMC622 is state of the art today and NMC811 is already waiting in the wings. In other words, the study is 10 years behind today’s technological developments.
In scientific LCA papers, we find a huge range in the energy consumption for the cell production, ranging from 3 MJ electricity/kWh of battery capacity to 2300 MJ electricity/kWh. This larger range is the result of a severe lack of available primary data from cell factories. Some looked for analogies in large-scale production of other technologies, like photovoltaic modules, others used data from lab scale or small-scale cell production, which resulted in very high consumption values per unit. The electricity consumption of the cell production is probably the most sensitive parameter with regard to greenhouse gas emissions, because all important production countries (China, South Korea, Japan and the U.S.) use a high share of fossil fuels for electricity generation. Meanwhile, energy consumption values for cell factories with capacities of up to 24 GWh/a have been disclosed or estimated at around 200 MJ electricity and heat / kWh cell capacity.
Figure 1: Greenhouse gas emissions of NMC batteries using Sphera’s LCA battery model
Figure 1 summarizes the greenhouse gas emissions to produce various NMC batteries derived from Sphera’s LCA battery model. The decrease in greenhouse gas emissions of up to 60% between NMC 111, assuming small volume cell production with high energy consumption, and the current NMC 622, with large volume cell production and distinct lower energy consumption production, illustrates the need for up-to-date assumptions and data in LCAs for emerging technologies. In recently published studies, one can still find greenhouse gas impacts for lithium-ion batteries in the range of 150-200 kg CO2-eq./kWh of battery capacity, which is also true for the VDI study (185 kg/kWh), but it makes an important difference if the production of a compact battery-electric passenger vehicle creates 10 or 16t CO2-eq.
As mentioned above, the country or region in which an electric vehicle is used has a significant influence on its environmental performance. In Figure 2, the greenhouse gas (GHG) emissions associated with the use of a compact passenger vehicle with different propulsion systems in various countries in the EU is displayed. For diesel and gasoline vehicles, the location of use influences only the impact of the fossil fuel supply, the emissions from the fuel combustion are the same assuming the same vehicle and WLTP consumption. Consequently, the variation of impacts from the use phase between the countries is small.
Figure 2: Influence of the use location on GHG emissions of passenegr vehicles
On the other hand, the impact from the use phase of electric vehicles is directly linked to the individual electricity supply in a specific country, region or grid. And this is also why general messages about the performance of electric vehicles with regard to greenhouse gas mitigation are difficult. An electric vehicle operated in Norway can reduce greenhouse gas emissions by 70% compared to a gasoline vehicle. In that context, further emissions reductions are only possible by reducing the impact of the manufacturing of the vehicle. Electric vehicles used in China or Poland create comparable (or even higher) greenhouse gas emissions than their gasoline or diesel counterparts.
An additional important factor is the development of the energy carrier mix for electricity generation within a country, region or grid during the time when the electric vehicles are used. Projections, published by national authorities or organizations, considering already decided or planned build-up of renewable electricity generation capacities or phase-out from coal use for electricity generation, are not without uncertainty. However, at least they provide an understanding for how a possible change in electricity generation during the use phase could influence the impact of an electric vehicle. Figure 3 illustrates this influence, using the current EU grid mix or a projection in the IEA World Energy Outlook to calculate the greenhouse gas emissions of an electric car during the use phase.
Figure 3: Impact of constant and projected electricity supply on electric vehicles in the EU
For a fair comparison of electric and conventional vehicles the additional reduction potential, associated with the development of the electricity supply, needs to be discussed to demonstrate that a decarbonization of the transportation sector with battery electric vehicles can only happen with a simultaneous decarbonization of the electricity supply.
Battery manufacturing and electricity supply are just two factors that have an important impact on the environmental performance of electric vehicles compared to conventional or other alternative vehicles. Recycling, resource supply, real driving consumption, urban transportation or the use of other alternative drivetrains or fuels, such as fuel cell electric vehicles or advanced biofuels and synfuels, are additional topics that need to be considered for greener transportation. In addition, the current focus on climate change risks a shift of burdens to other environmental impacts. The roll-out of battery electric vehicles as a mass product will have impacts on the supply and scarcity of certain metals. Water consumption for lithium supply, for example, is already being discussed in the media. But there are also emissions from the mining and preparation of battery precursors. These topics need to be tracked to better understand the environmental performance and benefits of electric vehicles and alternative solutions. The life cycle assessment method and related data and tools provide the possibility to cover a multitude of impact categories beyond climate change. Together with further accompanying studies on the social impacts and resource consumption, LCA should be used on a broader scale to assess the benefits and risks of new technologies.