The transport sector accounts worldwide for 27% of final energy consumption, and for 25% of the world carbon dioxide emissions [1]. The United States, European countries, especially Organisation for Economic Co-operation and Development (OECD) countries, and China are the world’s largest transportation energy consumers. Together, they account for about 55% of total energy consumption in the transport sector. Currently, transportation energy consumption is dominated by fossil fuels, gasoline and diesel, leading to different negative impacts on humans and environment.

Due to the urgent need to reduce Greenhouse Gas (GHG) emissions and local air pollution interest in electrification of mobility is rapidly increasing. However, in spite of the different supporting policies implemented in many countries, the amount of electricity used in the transport sector is still negligible. In 2016, the share of world total electricity consumption in the transport sector was only 1.7% (Figure 1). This is even for 0.7% lower than it was in 1973 [2].

Figure 1.

World electricity consumption by sectors (own compilation based on data source [2])

In the past, there were several waves of electrification of mobility. The first boom was at the turn of the 19^th century. The next wave emerged in the 1990’s but it disappeared very rapidly due to the limits of battery performances. With the emergence of lithium-ion batteries, which have been mostly used in the information technology sector, a new wave of enthusiasm regarding electric vehicles (EVs) started about 10 years ago.

In the meantime, EV’s have been recognized by many governments as technology which can contribute to emission reductions in the transport sector [3], [4]. Due to supporting policies implemented in many countries worldwide, the number of EV’s has been continuously increasing reaching more than 3 million vehicles in 2017 (Figure 2). The largest percentage of EV’s in the total EV’s stock exists currently in China (39%) and the USA (25%) followed by European countries, especially Norway (6%) and the Netherlands (4%) [5].

Figure 2.

Development of the global stock of rechargeable EV’s (own compilation based on data source [5])

However, total number of EV’s is still very low comparing to the total vehicle stock. The major reasons for the slow penetration of EV’s are higher purchase prices, shorter driving range and longer charging time comparing to conventional cars, as well as limited charging infrastructure [6], [7].

All these existing problems as well as future challenges have been discussed in literature over the last decade. Hoyer [8] documented the history of electric and hybrid cars, while recent developments of EV’s and future prospects have been investigated by Propfe et al. [9]. Economic assessment of EV’s is pretty good documented in literature. Weiss et al. [10] has analyzed the electrification of road transport with a special focus on learning rates and prices of Hybrid Electric Vehicles (HEV’s) and Battery Electric Vehicles (BEV’s). Business models for electric cars have been discussed by Kley et al. [11] and Christensen et al. [12]. Total costs of ownership are calculated for different cases, e.g. different types of EV’s, their use in different countries or different lifetime of EV’s [13], [14]. Currently, due to limited driving range of EV’s and restricted charging infrastructure, BEV’s are mostly used for short distances in cities, where average daily travel need is between 10 and 40 km [15]. In the future with the increasing energy density of batteries, as well as broader availability of charging infrastructure (including also possibilities for fast charging), the number of specific kilometers driven of EV’s could be much higher, making BEV’s more attractive and more cost-competitive with conventional cars. This could be supported also with deployment of inductive charging [16] as well as with the use of advanced materials in EV’s production [17].

In spite of the current limits, EV’s are widely supported by monetary and non-monetary measures implemented in many countries, as well as by policy targets set for the future. For example, according to the Paris Declaration on Electro-Mobility and Climate Change & Call to Action goal is to have worldwide more than 100 million EV’s and 400 million two and three-wheelers by 2030 [18]. However, the increasing electrification of mobility leads to intensified discussion on the real environmental benefits of EV’s.

Figure 3 shows different types of EV’s [BEV’s, HEV’s, Plug-In Hybrid Electric Vehicles (PHEV’s), and Range Extenders (REX’s)] with different level of electrification and consequently with different contribution to the emission reductions. A comprehensive discussion of different types of EV’s is provided by Ajanovic [19] and Ajanovic and Haas [20].

Figure 3.

Level of electrification of electric vehicles in comparison to conventional internal combustion engine (ICE) vehicles (own compilation based on Ajanovic [19])

Although, HEV’s are currently mostly used, due to similarity to conventional Internal Combustion Engine (ICE) vehicles, their contribution to the reduction of environmental problems is very limited. This paper focuses on rechargeable EV’s (PHEV, REX and BEV), which have higher level of electrification.

The core objective of this paper is to investigate the overall environmental impact of midsize rechargeable EV’s in different regions. The method of approach is based on a LCA of EV’s including emissions from electricity generation, vehicle production and disposal, and vehicle use. In addition, discussion on battery recycling is conducted.

Some of the environmental issues of EV’s have been addressed in several papers. The relevance of the use of electricity from Renewable Energy Sources (RES) for EV’s has been discussed by Sweeting and Winfield [21] and Ajanovic [19], [20]. These papers stress that to reach full environmental benefits of EV’s they have to be charged by electricity generated from RES. Anair and Mahmassani [22] provides an environmental analysis of EV’s regarding GHG emissions for several electricity grid regions in the USA. Zackrisson et al. [23] have used LCA to optimize the design of lithium-ion batteries for PHEV’s. Egedea et al. [24] presents a framework for the LCA of EV’s to consider influencing factors in the use phase. A comparison of the life cycle GHG emissions of BEV’s and ICE vehicles has been conducted by Ma et al. [25].

Hawkins et al.[26] reviewed about 50 studies on lifecycle of EV’s, concluding that study-to-study comparison is very difficult due to different definition of LCA boundaries, scopes and methods. The assumptions regarding the lifetime of EV’s, type and size of battery are also very different from study to study. Peters et al.[27] reviewed a large number of LCA analysis conducted in period 2000-2016 showing large dependency on data used and a weak base of primary life-cycle inventory data. Ellinger et al.[28] concludes in their work that data about manufacturing emissions of batteries differ a lot since it is very difficult to get a primary data from the battery industry.

The analysis in this paper provides a comprehensive assessment of major environmental issues related to EV’s in four selected areas, China, the USA, and Norway, and the EU-28 as a whole.

To assess the full environmental impact of different types of automotive technologies it is necessary to consider all emissions that occur in the whole energy supply chain including battery recycling. The environmental assessment of mobility focused usually on Well-to-Wheel (WTW) analysis including upstream emissions [Well-to-Tank (WTT)] that occur during the fuel or electricity production and supply, and tailpipe emissions [Tank-to-Wheel (TTW)] that occur during the car use.

In addition to this, it is important to consider emissions related to the manufacturing and disposal of cars. In this paper a combined WTW and Cradle-to-Grave (CTG) analysis is conducted (Figure 4). Moreover, emissions related to battery production and recycling are discussed in the scope of the sensitivity analysis.

Figure 4.

Method of emission assessment

In this paper the whole LCA assessment is divided in two categories: CO₂ emissions from the fuel cycle (electricity generation and vehicle use) and embedded emissions from vehicle production and scrappage.

The emission calculation is done by using the following formal framework: The total carbon dioxide emissions (CO₂) are calculated as the sum of embedded CO₂ emissions (CO_{2VEHICLE_CYCLE}) and the CO₂ emissions of the fuel cycle (CO_{2FUEL_CYCLE}):

The CO₂ emissions of the vehicle cycle are dependent on the embedded CO₂ emissions per kilometer driven and vehicle life-time [eq. (2)]:

The total embedded CO₂ emissions of the vehicle are obtained from the sum of the embedded CO₂ emissions of different materials (CO₂EMB_MAT_i) used in vehicle production and the CO₂ emissions of the production process (CO₂PRODUCTION):

The CO₂ emissions of the fuel cycle (CO₂FUEL_CYCLE) are calculated as:

where EIis electricity/energy intensity [kWh/km] of vehicles.

The specific CO₂ emission factor (f_CO2 ) is calculated by weighing the shares of electricity and fossil fuels:

The corresponding factor for electricity (f_CO2el) is calculated by weighing the shares of the single energy carriers (j) in the electricity mix:

where q_jrepresents the share of the single energy carriers in electricity generation.

The major contribution of this paper is that it addresses simultaneously all key impact parameters on the environmental impact of EV’s: the electricity mix, type of EV’s, travel activity and the embedded energy of the car. In addition, a discussion on the sensitivity of the impact of major parameters on the specific CO₂ emissions per kilometer driven is conducted. The impact of km driven per car and year, the fuel mix for electricity generation and the category of EV (PHEV, REX, BEV) are analyzed in detail.

The analysis of the emissions related to electric vehicles is conducted in four steps:

• WTT assessment based on different energy mix for electricity generation;

• TTW assessment which is dependent on vehicle type and use;

• Emissions related to vehicles production;

• Discussion on possible benefits of the battery recycling.

Well-to-Tank assessment: Electricity generation

While for conventional vehicles the TTW energy conversion accounts for the most of the total GHG emissions, total emissions of EV’s are largely dependent on WTT emissions. In the case of conventional cars, WTT emissions are known quite well – the carbon intensity for petrol production is 0.46 kg CO₂/L [29]. However, carbon intensity of electricity could be very different depending on the primary energy sources used for electricity generation (Figure 5).

Figure 5.

The carbon intensity of electricity generation (own compilation based on [30])

The total carbon intensity of grid electricity is dependent on the emissions caused during electricity generation and the losses in transmission and distribution of electricity. It is different from country to country depending on the mix of energy sources used in electricity production. The development of the mix of energy sources used in electricity generation in the EU-28 is shown in Figure 6. It can be noticed, especially in the last few years, a significant decrease in use of solid fuels and petroleum, and very rapid increase in the use of renewables.

Figure 6.

Electricity generation in the EU 28 (own compilation based on [31])

However, there are significant differences between carbon intensity of the electricity mix across European countries (Figure 7). While the average carbon intensity of electricity generation in the EU in 2014 was about 376 g CO₂/kWh, in some countries (Greece, Malta and Estonia) it was more than 700 g CO₂/kWh, and in some below 60 g CO₂/kWh (e.g. Sweden, France and Austria).

Figure 7.

CO₂ per kWh electricity generated in different European countries (2014) (own compilation based on [32])

According to the EU’s Energy and Climate Change Packages for 2020 and 2030 increasing use of RES in electricity generation is one of the three major targets [33], [34]. Increasing share of RES in the electricity mix should make EV’s more environmentally friendly and therefore more attractive. However, as shown in Figure 6, in spite of increasing use of renewables for electricity generation in the EU, coal still makes a significant contribution.

Currently, in Europe, Norway is a leading country in promotion and use of EV’s. On the other side, largest number of EV’s is in the USA, China and the EU (Figure 2). However, due to very different country specific electricity mixes, contribution of EV’s to the reduction of the global GHG emissions is very different. As shown in Figure 8, electricity mix in Norway is dominated by renewables (about 98%), in the USA and China by fossil energy (about 70%). In the EU-28 renewables, nuclear and coal have about the same share.

Figure 8.

Electricity mix in selected countries/regions: China, the EU, Norway and USA, 2014 (own compilation based on [35], [36])

The actual electricity mix has significant impacts on the WTT emissions of EV’s, as well as emissions from the EV’s manufacturing, including battery.

EV’s are widely promoted as environmentally friendly technology and many governments worldwide have provided different incentives with the goal to increase use of EV’s and finally to reduce local air pollutions and GHG emissions from the transport sector.

However, as discussed above, total emissions of EV’s are dependent from the emissions caused during the vehicle production and use, and especially from the emissions caused during the production of electricity which is used in EV’s. The use of EV’s in selected countries/regions, which are very active in promotion and use of EVs ‒ China, the USA, the EU and Norway ‒ and also have very different specific electricity mix, is analyzed in this paper to stress the impact of electricity mix on total environmental benefits of EV’s.

Total CO₂ emissions per km driven for various types of EV’s and different electricity mixes in the selected countries are shown in Figure 9 compared to gasoline vehicles. An average driving range of 15,000 km is assumed.

Figure 9.

Total CO₂ emissions per km driven for various types of EV’s and different electricity mixes in selected countries/regions: China, Norway, the EU and the USA

In contrary to ICE vehicles, which have the same CO₂ balances in all analyzed countries, rechargeable EV’s show significant differences in their environmental benefits in China, the USA and Norway. Only in Norway, clear advantage of rechargeable EV’s can be seen. In the USA, total emissions of rechargeable EV’s are almost in the same range with conventional cars. The worst situation is in China where rechargeable EV’s caused higher emissions then conventional cars. The only advantage in this case is that these emissions could be easier controlled, and that in spite of the overall higher emissions, local emissions and pollutions could be reduced what is also of high priority in most urban areas in China.

However, the results shown in Figure 9 are sensitive on the assumptions regarding the total number of vehicle kilometers driven over vehicle lifetime in all countries, in some more in some less. These are shown in detail in Figure 10.

Figure 10.

Total CO₂ emissions per km driven for different numbers of vehicles km driven in selected countries/regions

It is obvious that, due to the impact of embedded emissions, total CO₂ emissions per km driven are decreasing with the increasing number of vehicle kilometers driven. However, the impact of the number of kilometer driven is moderate compared to the effect of the generation mix. While for gasoline cars for 23,000 km driven total emissions per km are about 16% lower than for 8,000 km, for BEV’s in China, the USA and Norway it is 21%, 31% and 65% less emissions, respectively. This is because in Norway the emissions from the fuel cycle are close to zero.

Figure 10. Total CO₂ emissions per km driven for different numbers of vehicles km driven in selected countries/regions

Moreover, CO₂ emissions of PHEV’s and REX are sensitive on the assumptions regarding the use of electricity and fossil fuels in car. For example, Samaras [42] has calculated total GHG emissions of PHEV’s in the USA assuming different ratios of electricity and gasoline – 30:70, 60:40 and 90:10 – however, the largest difference is about 30 g CO₂ per km driven.

For the average EU, electricity mix in 2010 is estimated that BEV’s and PHEV’s (assuming 50:50 electricity and gasoline ratio in PHEV’s) could contribute to the reduction of emissions in comparison to conventional cars up to 75 g CO₂ per km [40].

Similar analysis for BEV’s has been conducted by Wilson [50], showing very high emissions per km driven in China, Indonesia, Australia, South Africa and India. On the other side, Paraguay, Iceland and Sweden are also countries in which E-mobility could provide clear environmental benefits.

As discussed above, the impact of battery recycling is still heavily disputed. Especially the possible magnitude of a reduction of CO₂ emissions due to battery recycling varies very widely, from 7% to 70% as cited above. In Figure 11, a comparison of the overall CO₂ emissions per km driven is shown for two different cases, with “No recycling” and “50% recycling”.

Figure 11.

Impact of battery recycling on total emissions

Figure 11. Impact of battery recycling on total emissions

It can be seen that even a reduction of the embedded emissions in the cars by 50% due to the battery recycling would not significantly change the overall balance between EV’s and conventional cars. In the case of recycling, total emission reduction is about 25 g CO₂/km for the average number of km driven (Figure 11). However, as shown in Figure 10, the impact of travel activity is between 15 and 40 g CO₂/km. Hence, battery recycling lies somewhere in the middle of the impact of km driven.

Finally, the major finding is that the impact of the electricity mix is dominating, followed by travel activity and battery recycling.

The public tends to judge the environmental benefits of cars usually by their energy consumption and emissions at the point of use. However, the whole effects of mobility on the environment have to be based on LCA analyses over the vehicle’s entire lifetime.

The major conclusions of our analysis are: EV’s could contribute to solving some of the problems in the transport sector. However, they cannot be considered automatically to be environmentally benign. The specific conditions in every country/region have to be considered very carefully.

As analyzed in this paper, the environmental benignity of EV’s is sensitive on:

• Electricity mix;

• Travel activity (number of km driven per year);

• Embedded CO₂ in car production.

As shown in this paper, the highest sensitivity is with respect to the electricity mix. Since BEV’s are locally emission-free, their WTT emissions have a great impact on the total environmental performance. Considerable differences can occur depending on the regional electricity mix. However, the full environmental benefits can be obtained only in combination with electricity from RES. Due to difference in electricity mix used in different countries, the environmental impact of EV’s could be very positive as well as negative. The sources for electricity generation may lead to major setbacks in the emission reduction through electrification of mobility. The most important issue to make EV’s more environmental friendly is to increase the use of RES in electricity generation, what is already one of the priorities of the European energy and climate policy.

Travel activity has multiple impacts on the emissions. On the one side, a lower number of km driven per year means lower energy consumption. On the other side, using CO₂ per km driven as an indicator implies that the car is the more environmentally benign the more km are driven with the car per year. With the higher number of km driven per car, the impact of emissions embedded in car is lower. This implies that a good option could be to use EV’s for car sharing where the number of km driven is relatively high. It is simply more favorable to drive, for example, 24,000 km with one car than three times 8,000 km with three cars.

In addition, battery recycling plays a considerable role in reduction of CO₂ emissions. Moreover, some of the materials used for battery productions are limited, and their mining and refining is associated with negative environmental impacts. Currently, many governments support the use of EV’s with different measures and policies but clear framework for lithium-ion battery collection and quality of recycling is still lacking. Today we have about 3 million EV’s on the road worldwide. In 6 to 10 years, we will have 3 million batteries to salvage. The idea of second life for these batteries will not solve but rather delay this problem. It is now of highest priority that the policymakers in all countries promoting EV’s become aware of this problem and try to find solutions which will not create new environmental problems.