Are electric vehicles sustainable?
The transport sector is one of the largest consumers of energy in the world, it currently consumes 21% of all the global energy and feedstock fuels. Road transport represents 73% of this energy consumption , enormously dependent on fossil fuels (close to 93%). Related to the emissions, the transport sector represents a quarter of the total CO2 emis- sions in the world, with 8.1 Gt of CO2. The passenger road vehicles are responsible for the 44% of these emissions, with 3.6 Gt of CO2 . Therefore, is one of the most important sectors contributing to climate change, and also contribute to high concentrations of air pollutants. Based on the above, for the coming years, it is important to switch from a fossil fuel- dependent energy source to a clean energy source, to reduce the greenhouse gas emissions and increase the air quality. One of the ways to reach this objective is to move from internal combustion engine vehicles to electric vehicles. There are several electric vehicles types  including pure battery electric vehicles, pow- ered by an electric motor only, as well as plug-in hybrid cars that have both an electric motor and an internal combustion engine. In 2018, the number of electric vehicles reaches 5.1 million, almost doubling the number of electric vehicles in the market. China has the largest electric car market, followed by Europe and the US . Referred to the market share, Norway is the country with the highest participation of electric vehicles in the market, with 46%.
Figure 1: Electric car stock by country, 2018. Source: IEA Analysis based on country submissions, complemented by Chinabaogao (2019) and EAFO (2019).
The growing of electric mobility will produce an important increase in energy demand in the future. In the New Policies Scenario , electricity demand for EVs is projected to reach 640 TWh in 2030. This is a tenfold increase from the 2018 level of 58 TWh. Therefore, electricity procurement within the power system is of immense importance. The level of sustainability of the electric vehicles depends highly on the source of the electricity they use, and it also depends on the pollution and emissions generated by the manufacturing process of their batteries.
The source of energy matters The potential of electric vehicles to reach the decarbonization of the future road transport sector highly depends on how the demand for additional electricity for EVs will be gen- erated. In a scenario assumed by the European Environment Agency in where the share of electric cars will represent 80% by 2050, the energy demand from electric vehicles will increase from 0.03% in 2014 to around 4-5% by 2030 and 9.5% by 2050 . In countries with high shares of fossil power plants, the increase in electricity demand could lead to higher CO2 emissions. Therefore, the environmental benefit of electric cars in these cases would not be fully reached. The production of electric vehicles is more energy-intensive than internal combustion en- gines vehicles manufacture. The electric engine system and batteries of electric vehicles need around 70% more primary energy than conventional vehicles . This higher energy demand can produce higher emissions of greenhouse gases, depending on the source of energy used. To fully understand the total impact of different vehicles and fuel types we need to look at their complete lifetime, from the production to the disposal. A recent Dutch study  that. compares different vehicles powered by different fuel types clearly shows the importance that the source of electricity has.
Figure 2: Range of life-cycle CO2 emissions for different vehicles and fuel types. Source: TNO, 2015
According to the study, Battery electric vehicles produce higher emissions than a conven- tional vehicle if the source of electricity is assumed 100% by fossil fuels. During their lifetime, battery electric vehicles are only as clean as their source of electricity. Greater demand for electricity will require both adequate generation capacity as well as the capability of electricity grids to handle the additional amounts of electricity generated. Emissions from the road transport sector will be displaced to the power generation sector. These emissions will depend on the overall fuel mix used in that sector, and, if the fuel mix varies throughout the day, on the time when vehicles are charged. Assuming that the power generation decarbonization is consistent with the IEA Sus- tainable Development Scenario , the electric vehicles (battery electric vehicles, plug-in hybrid electric cars and hybrid vehicles) will emit less GHGs than a global average internal combustion engine vehicle using gasoline over their life cycle.
Emissions for battery production are key A critical parameter in the comparison between electric vehicles and conventional vehicles is the quantification of emissions from battery production. Battery production require- ments imply a bigger demand for new materials in the automotive sector. An interesting study in China  indicates that Chinese EV battery manufacturers produce up to 60% more CO2 during fabrication than conventional vehicles. With the development of bat- tery manufacture techniques, the CO2 emissions from Li-ion batteries can be reduced, to reduce the environmental impact of this type of vehicles. Decision-makers in China are stimulating innovation to the battery sector, giving preference to those that offer batteries with the best performance. The actual extraction process of batteries generates higher pollution than the manufac- turing process of petrol or diesel-based engines. One of the most important elements of the existent batteries is lithium. This element is not considered a critical metal, global supplies are ample. On the other hand, batteries also are produced by cobalt, copper and nickel . Specifically, the production of cobalt and nickel present potential environmental and health hazards.
Figure 3: Main extraction and refining locations of key materials for automotive batteries
The main risks of raw material supply for batteries are production-related (lack of reserves resources), geopolitical (highly dependent on national policies) and environmental (local pollution, supply chain-related CO2 emissions, landscape destruction). The battery end-of-life management is key to reduce the dependency of the critical raw materials needed in batteries and to limit risks of shortages. A reduce, reuse and recycle of batteries must be achieved to reduce the environmental impact. Improvements in battery manufacturing and use can give potential reductions in GHGs . First, grid decarbonization not only helps to reduce the emissions of the use of electric vehicles, but it also helps to reduce the emissions related to battery production. The use of renewable energy and more efficient power plants will lead to cleaner batteries. Second, stationary storage applications can reuse the batteries removed from electric cars. Therefore, they could be used to support the electric grid, especially as intermittent renew- ables become more widespread. Third, with battery recycling, the total carbon footprint caused by battery production can be reduced, specifically from the material extraction that is responsible for half of the GHG emission form battery production. Finally, battery energy density is increasing at an average rate of approximately 5%–8% per year .
Conclusion Based on the analysis conducted by many studies, it can be concluded that electrical vehi- cles could help the world decarbonization and be sustainable if the electricity source they use comes from renewable sources. However, personally speaking, to make the transport sector sustainable, we not only have to look for the GHGs emissions and air pollution among the different technologies, but we have to look at innovative ways of reducing our dependence on vehicles. For instance, we can look for car-sharing schemes, develop bet- ter and efficient public transport efficient and increase the use of zero-emission transport modes. Only replacing conventional vehicles with electric vehicles will not solve the plenty of problems that the transport sector has, such as growing congestion and increasing de- mand for roading infrastructure. We need to change how we use our transport systems. This will also help to reach the multiple objectives to a more resource-efficient, green and competitive low-carbon economy. On the other hand, in the short term, people will continue using motorized road vehicles, and therefore developing new technologies such as electric vehicles powered by renewable sources is necessary. Moreover, electric vehicles can provide flexibility services to power systems with the inte- gration of variable renewable energy source for electricity generation. Not less important, in the case that both electric vehicles and conventional vehicles cause the same emissions, the exposure to that emissions cannot be compared. Most of the emissions of electric vehicles come from the power generation and most of the emissions of conventional vehicles come from its use . Emission from road transport occurs at ground level and generally, in areas such as in cities and towns, so many populations are exposed to them. On the other hand, power plants are generally outside cities, in less pop- ulated areas. Besides, electric vehicles are quieter than conventional vehicles. Therefore, contributes to less noise pollution. Finally, to conclude, to assume the sustainability of electric vehicles we need to assure the extra electricity they will demand is supplied by the energy mix projected for 2050 by the EU Reference Scenario 2013 . Future emissions of both GHGs and air pollutions would be lower, producing a clear environmental benefit. Also, according to the batteries that electric vehicles use, it is necessary to achieve the reuse, the recycle and a greater energy density to reduce the life cycle emissions of one of the most important elements that conform the electric vehicles.
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