More or less lithium in our vehicles?

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The carbon footprint of EVs

Electric vehicles (EVs) have several benefits. They help keep a good quality of air in cities, reduce sound pollution, and they are more efficient than internal combustion engine vehicles (ICEV).

However, EVs are not intrinsically better for the environment.

The environmental impact of a vehicle can be measured by using its life-cycle emissions. This metric considers the CO2 and other greenhouse gas emissions produced during the vehicle’s production, its use (we use 180 000 km as a reference here), and its recycling. Lifecycle emissions are usually expressed in tons of CO2 equivalent (tCO2-eq) or simply tons of CO2 (tCO2).

The potential of EVs to be low-emission solutions depends mainly on three factors mentioned hereinabove:

1. The sources of energy used to produce the electricity they are powered with;
2. Their energy consumption;
3. Their production: An EV can have 30 to 90% higher production emissions than an ICEV of equivalent size, mainly due to its battery (Ellingsen et al. 2016).

Let’s look at the effect of these three factors.

Energy sources

The sources of energy used to fuel an EV can determine if an EV’s total emissions will be higher or lower than those of an ICEV.

The emissions of coal-produced electricity are actually higher than those of petrol or diesel. Thus, powering an EV from coal-produced electricity during its life results in higher emissions than using ICEV of equivalent size.

The life-cycle emissions of electricity generation range from 21 gCO2 per kWh for the wind energy to 1029 gCO2 per kWh for coal. The European electricity mix average is somewhere halfway these two at 521 gCO2 per kWh (Ellingsen et al. 2016). The image below illustrates the effect of these energy sources on the life-cycle emissions of EVs. 

Energy consumption

The energy consumption of a vehicle is directly affected by its weight. A heavier vehicle produces more emissions per kilometer than a lighter one as it requires more energy to move. In fact, the weight of an EV correlates to its energy consumption by a factor of 5.6 kWh/km per 100 kg (Ellingsen et al. 2016).

The energy consumption of a luxury EV that weighs 2100 kg (20.7 kWh/100km) is 42% higher than the energy consumption of a small EV that weighs 1100 kg (14.6 kWh/100km). This difference is directly reflected in their use phase emissions, where the luxury EV produces 42% more emissions than the small EV. 

The energy consumption is also directly affected by the energy efficiency of the propulsion system of the vehicle (EVs vs. ICEVs). EVs have tank-to-wheel (TTW) efficiencies ranging from 1.4 to 6.7 times higher than those of an ICEV. 

When we compare a small EV to its equivalent-size ICEV, the EV produces 61% less emission than its ICEV counterpart. Similarly, a luxury EV produces 90% less emissions than its ICEV counterpart (considering Europan electricity mix). This is partly due to the cleaner energy sources, and greatly due to their higher tank-to-wheel efficiencies. These efficiencies allow EVs to have consumptions of 1.6 Le/100km for the small EV, and 2.3Le/100km for the luxury EV (with a conversion factor of 8.9 kWh per liter of gasoline. Source: Natural Resources Canada). 

Battery size

The size of the battery plays an important role in the footprint of an EV. It contributes 14% to 26% of the EV’s total life-cycle emissions.

The largest contribution of the battery to the footprint of an EV comes from its production, adding about between 0.5 to 5 tons of CO2 per 10 kWh (Hall et Lutsey 2018). This represents 33% to 46% of the total production phase emissions and puts EVs at a high initial environmental debt compared to ICEVs.

For the use and recycling phases, the battery contributes 4% to 11% and 14% to 23% of the phase emissions, respectively, depending on the vehicle and battery size.

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Beyond CO2

Electric batteries have other environmental impacts, aside from contributing to the carbon footprint of EVs. For example, 75% of the Lithium reserves are located in the water-scarce regions of Bolivia, Chile, and Argentina. The water-intensive extraction of Lithium puts extra pressure on water resources, introduces risks of water, soil, and air contamination, and destroys the local landscape (Hollender et Shultz 2010).

The most popular battery used by EV manufacturers is the Lithium Nickel Manganese Cobalt Oxide (NMC) because of its competitive energy density. This battery is 6% made of Cobalt. Cobalt is a toxic metal and it is extracted in an unregulated artisanal manner in poor and politically unstable Republic of Congo, who has 50 to 60% of the world resources (Mann 2017).

Considering the environmental costs of the three factors discussed (sources of energy, energy consumption, and vehicle production), as a VIGOZ manufacturer we ask ourselves the question:

How much lithium should we have in the vehicle we develop?

We decided to answer this question in the following way.

Our fastest vehicle

At CIXI we are building the VIGOZ, a new type of active and low-footprint vehicle that (re)introduces daily physical activity in our lives. We believe daily physical activity brings more than improved health. We also believe that people are ready to adopt new and lower environmental impact solutions.

In the spirit of creating a low-footprint vehicle, we carried out a study to better understand people’s daily mobility needs. The idea behind this study was to find out how big of a battery we should put in the VIGOZ to satisfy our pilots, without necessarily joining the market race of bigger-is-better.

This study consisted on collecting and analyzing GPX files of a large sample of people that recorded their trips for one week. GPX files contained GPS information or their position over time. From these files, we could extract speed, acceleration, and elevation throughout a trip. With a simple model of a vehicle, we could then compute the energy consumption over the recorded trip.

This information enabled us to do two things.

Firstly, it helped us understand the mobility needs of individuals: their autonomy, type of roads taken, type of trips, number of people. Considering this, we could better understand the battery size that would best satisfy people.

Secondly, we thanked participants by preparing them a personalized report containing their energy consumption and environmental footprint in grams of CO2. This helped us and participants better understand the environmental impacts of their mobility. To give a little CIXI touch to this report, we also shared the potential extra time people would have for exercising and developing a healthier lifestyle.

Thanks to this study, we have determined the ideal autonomy for our vehicle, that is 160 km.

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References

1. H. C. Righolt and F. G. Rieck, “Energy chain and efficiency in urban traffic for ICE and EV”, 2013 World Electric Vehicle Symposium and Exhibition (EVS27), Barcelona, 2013, pp. 1–7. doi: 10.1109/EVS.2013.6914820
2. Linda Ager-Wick Ellingsen et al, “The size and range effect: lifecycle greenhouse gas emissions of electric vehicles,” 2016 Environ. Res. Lett. 11 054010. doi:10.1088/1748–9326/11/5/054010
3. European Environment Agency. “Infographic: Range of life-cycle CO2 emissions for different vehicle and fuel types” Prod-ID: INF-66-en, Published 29 Aug 2017 Last modified 22 Nov 2017. Ragan’s PR Daily
4. Hall et N. Lutsey, “Effects of battery manufacturing on electric vehicle life-cycle greenhouse gas emissions”, Thr international council on clean transportation — ICCT. Beijing, Berlin, Brussels, San Francisco, Washington, 2018, pp. 1–12.
5. R. Hollender and J. Shultz, “Bolivia and its Lithium: Can the ‘Gold of the 21st Century’ Lift a Nation out of Poverty?” A Democracy Center Report, Cochabamba, 2010. pp. 1–57.
6. E. Mann, “Digital Technology is Dependent on Forced Labor: The Exploitative Labor Practices of Cobalt Extraction in the Democratic Republic of Congo”, 2010. 

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