Are electric cars cleaner for climate change ?
Climate change, air pollution, dieselgate, electrification, gray energy, coal power plants, nuclear transition. Consumers are bombarded with a deluge of connected but often contradictory and confusing information about their personal mobility. This situation is made worse by political and ideological agendae. Faced with confusing inputs, daunting implications and remote consequences, most consumers are tempted to gravitate to the status quo. In an open minded quest for clarity, we poured over studies which examine the climate of footprint of different types of cars.
CO2: transportation matters
On October 9th 2018, the council of european environment ministers settled in favour of a 35% reduction of CO2 emissions by 2030 for manufacturers of passenger cars and vans compared to 2021 targets (95 g/km). The european parliament had asked for 40%. The final figure will have to be negotiated between the parliament and the Commission, but is very likely to fall in the 30 to 40% range, or 57 to 67 g/km. It is very likely that the Swiss Confederation, which is not a member of the European Union, will adopt the same targets.
This decision falls within the context of the release of the IPCC special report on the effects of a 1.5 degC global warming compared to the pre-industrial era. The findings are grim:
The median scenario (in gray) assumes net zero CO2 emisssions after 2055 and projects average temperatures at the surface of the earth. The purple scenario reflects the outcome if CO2 emissions were not to be reduced. This graph also shows that the 1.5 degC is may be reached before 2040. The severity of this situation is recognized by most OECD country governments, with the extremely notable exception of the current United States administration. The next questions is: do cars matter in this global equation ?
The state of transportation
In the European Union’s 28 countries in 2015, the transportation sector represented 25.8% of greenhouse gas emissions. Among different modes of transportation, road transport accounted for 72.9% while aviation and sea were only 13% each. These 72.9% are further split as follows: 44.4% for passenger cars, 8.6% for light duty vans and 18.8% heavy duty trucks. Passenger cars are therefore not a scape goat of climate policies. They are a material contributor to the carbon footprint of consumers, and an inevitable topic when it comes to carbon emissions reduction. The next question is then: do electric cars help ?
Are electric cars a solution ?
The simple answer to this complex question is: it depends. On multiple factors, including the place where you live and move. This type of answer unfortunately does not align well with pre-conveived ideas – sometimes ideologies – which only tolerate absolute and monolithic answers.
The comparison of two complex ecosystems such as:
– the petrol industry and the internal combustion engine vehicle on the one hand,
– electricity production, batteries and electric vehicles on the other hand
requires a holistic analysis which encompasses the full life cycle, from manufacturing to usage to disposal at end of life.
We review here the findings of four such life cycle studies, conducted in or for four countries, in Europe and North America:
– Life Cycle CO2e Assessment of Low Carbon Cars 2020-2030 (2013), a study conducted in 2013 by PE International under mandage from the Low Carbon Vehicle Partnership, a british organization aiming to accelerate a sustainable shift to low carbon vehicles and fuels in the UK
– Cleaner Cars from Cradle to Grave (2015), a study lead by the Union of Concerned Scientists
– Bilans énergétiques, des émissions de gaz à effet de serre et autres impacts environnementaux induits par l’ensemble des filières de véhicules électriques et thermiques (2013), a study commissioned by Agence française De l’Environnement et de la Maîtrise de l’Energie (Ademe) and co-written by PE International
– Aktualisierung Umweltaspekte von Elektroautos), a swiss study mandated by the étude suisse mandatée par the swiss Federal Office for the Environment and updated in 2018.
The british study
The british study concludes that, in a typical scenario for 2020, an electric car will have a lifetime footprint of 21.6 tons of CO2, 6% higher than a PHEV (Plugin Hybrid Electric Vehicle) but 12% lower than a HEV (non rechargeable hybrid car). Total emissions for the electric car are 24.7% lower than its equivalent with an internal combustion engine.
The footprint, computed in tons of Green House Gas CO2 equivalent, is substantially the same between an electric and a plugin rechargeable. The electric car is cleaner, from a climate change standpoint, than an equivalent combustion engine vehicle, but only by 25%.
The main assumptions of this study are:
– Life cycle evaluation on the basis of 150’000 km of use
– Compact petrol car (Golf, Mégane, Focus) weighing 1240 kg and fueld by an E10 mix (gas with 10% of ethanol) and a NEDC mileage of 5.83 L/100 km, improving by 7% in 2020
– Hybrid car: Toyota Auris with a 1.3 kWh NiMH battery pack and a NEDC mileage of 4.0 L/100 km, improving by 6% in 2020
– Plugin rechargeable hybrid car: Toyota Prius Plug-In, with a 4.4 kWh Lithium Ion pack, an a NEDC mileage of 2.1 L/100 km, improving by 4% in 2020
– Electric car: Nissan Leaf, with a 24 kWh Lithium Ion pack and an electric consumption of 150 Wh/km, improved by 2% in 2020
– Production of electricity resulting in 390 g of CO2 equivalent per kWh
The british study estimates the CO2e footprint related to the manufacturing of the different vehicle categories, often called grey energy:
Updated for contemporary models with an electric range more acceptable to consumers i.e. doubled, the difference in the manufacturing footprint becomes more stark.
The manufacturing footprint estimate in this study suggests the following comments:
– the place of manufacturing and related energy source(s) assumed are not clearly documented while they should play a prominent role in the footprint of the supply chain
– recycling of the battery pack at vehicle end of life, for instance for grid storage, if it eventually becomes scalable
The french study
The study mandated by the french environment agency is a variant of the british study, and was co-written by the same consultancy, PE International.
The assumptions were adapted to the specifics of the french market and car industry:
– Comparaison of three sub-compact with lengths ranging from 3.8 to 3.9m, one with a petrol engine (5.9 L/100km), one with a diesel engine (4.1 L/100km) and an electric car with a 24 kWh battery, and all three with 75 hp of power.
– The greenhouse gas impact is assessed over 150’000 km (93’226 mi).
– Electricity is accounted at 83 g CO2e/kWh for France in 2020, and 636 g CO2e/kWh for Germany. For reference, the british study assumes 390 g/kWh.
The french study lands on the following of the manufacturing footprint, projected for year 2020:
The grey energy embedded in the diesel and petrol cars are comparable to the british study, but the assessment of the electric car – though identical in its definition – is 23% lower.
Combined with driving-related emissions, the french study reaches the following tally:
With 23 tons of CO2e, the small petrol car has a climate change footprint 21% higher than the the small diesel car (19 tons). The compact electric car, powered mostly by french nuclear power (83 g CO2e/kWh) comes out significantly ahead.
If the working assumptions are adjusted by:
– doubling the battery capacity to 48 kWh to reflect consumer range expectations
– using german electricity with a 7.7x higher CO2e footprint,
the result becomes:
The climate footprint of a battery electric vehicle (BEV) can easily triple depending on the capacity of its battery pack and the source of the electricity used to charge it. This does not make a BEV worse than a petrol car from a climate impact viewpoint, but it does not make it better either, and certainly does not qualify as clean. One will note that the absolute figures are very comparable to the british study, with figures above 20 tons of CO2e over a 150’000 km lifecycle.
The american study
The study of the Union of Concerned Scientists (UCS) is more recent and focuses on the comparison of the climate footprint of two passenger car categories, each with petrol and BEV alternatives:
– A 24 kWh Nissan Leaf achieving 186 Wh/km
– A 1362 kg compact petrol car achieving 29 MPG i.e. 8.1 L/100km, for instance a Ford Focus, Mazda 3 or VW Golf
– A Tesla Model S 85 kWh achieving 236 Wh/km
– A 1952 kg full size sedan achieving 21 MPG i.e. 11.2 L/100km.
Lifecycle impact for the compact cars is assessed over 135’000 miles (217’000 km), and 179’000 miles (288’000 km) for sedans.
With 8.8 tons of CO2e for the same Nissan Leaf, the american model estimates the manufacturing footprint at 9 tons, a level comparable with the british study, but 28% higher than the french study. The Tesla Model S 85 kWh is estimated at 15.2 tons of CO2e, including 5.4 tons for the battery pack.
With high mileage assumptions, the lifecycle estimate puts significant emphasis on the energy consumtion from driving. And in this are, the UCS study builds on an questionable assumption: electricity production is weighed based on the EV sales in each region, not on the basis of population or car sales. If the intent is to study the environmental impact of widespread adoption, the regions where early adopters abound should not skew the results and be assumed to represent the environmental equation for all consumers. The problem statement lies in the benefit of EVs for the broad majority, not EVs for the sub-1% minority who has adopted them already.
The UCS reports extremely significant disparities in the electricity climate footprint by region of the US, with an average at 480 g/kWh, and extremes at 291 g/kWh in Alaska, and 942 g/kWh in the midwest. EVs can be dirtier than ICE depending on where you drive them.
With this assumption, the UCS study thereby reaches favorable results for both electric cars: a reduction of more than 50% of greenhouse gases emissions. However, for a midwest consumer, the break even point between an ICE sedan and a Tesla Model S is at 60’000 km. The selected petrol full size sedan is more advantageous, in climate terms, before this milestone.
Assuming a modern sedan, for instance a light hybrid sipping 6.5 L/100km, would push the break even point with Model S fed with 480 g/kWh electricity to more than 80’000 km.
And in Switzerland ?
The swiss Federal Office for the Environnement has commissionned an impact study for electric passenger cars (Aktualisierung Umweltaspekte von Elektroautos).
This document reviews the manufacturing and driving footprint of a wide array of passenger cars:
– an average diesel compact car (6.0 L/100km)
– an average petrol compact car (8.5 L/100km)
– a car powered by Compressed Natural Gas
– the best in class di (Citroen C4 1.6 BlueHDI 100, 4.6 L/100km)
– the best selling compact petrol car (VW Golf 1.4 TSI DSG, 7.1 L/100km)
– a battery electric car (BEV): VW eGolf with a 33.4 kWh battery
– a hybrid petrol car (HEV): Toyota Prius III (5.6 L/100km)
– a plugin hybrid car (PHEV): Toyota Prius III plug-in (3.4 L/100km)
In this study, the manufacturing footprint includes maintenance as well. Emissions related to the source of energy are split between energy production and energy consumption. For the electric car (BEV), driving emissions result from the air conditioning refrigerant gas.
A few assumptions stand out from some of the other studies:
– real mileage values are used, not normalized NEDC values which are notoriously optimistic
– electricity production estimated at 182 g/kWh CO2e based on the consumption mix in Switzerland, including energy imports
– hybrids being driven in electric mode for 35% of distances
– a car lifecycle of 150’000 km, but with half of Lithium Ion battery packs requiring a replacement at 100’000 km.
These factors amplify the footprint estimate of all internal combustion cars: with 32 to 40 tons of CO2e, compact diesel cars are estimated 1.5 to 2x higher than in the french study. The swiss study also reaches a strikingly higher manufacturing footprint than the three other papers.
The differences are striking but, in absolute terms, energy supply during the driving phase remains the dominant factor.
So ? Are EVs cleaner ?
All studies point to similar conclusions: the climate footprint of battery electric compact cars (Nissan Leaf 24 kWh, VW eGolf 33.4 kWh) is significantly smaller than their internal combustion engine counterparts. There is however a significant nuance: smaller does not mean null. From a climate change standpoint, BEVs pollute twice less at best.
The factor that can offset dramatically the equation is the eletricity production footprint, which can sharply vary based on geography: there is a 10x factor between nuclear electricity (France) and territories with fossile power generation (Germany, US midwest).
Battery pack capacity, which can quadruple between a 24 kWh first generation Nissan Leaf and a Tesla Model S 100D is also a significant factor, and the estimates for grey energy vary a lot between studies:
The assumptions underlying the footprint of the Model S batteries as computed by the US look particularly optimistic, especially given the fact that cell production is located in Japan (554 g CO2/kWh in 2016).
Here again, the swiss study is an outlier and under these assumptions, for the same cell chemistry, increasing capacity and range to meet consumer adoption thresholds harms the ecological equation. However, none of these study concludes that battery grey energy is a decisive factor for the footprint. The electricity source is always a bigger factor.
Electricity production collides with political trends in the energy sector (Energiewende in Germany, Strategy 2050 in Switzerland). Both countries have decided to obsolete their nuclear production infrastructure, but without a clear alternative providing a reliable energy production bedrock which can be relied upon independently from seasons or weather events, 365/24.
Switzerland, for instance, must replace its aging nuclear power plants (31% of electricity consumption in 2017) with other sources in a context where the hydroelectric potential of the alps is tapped out and climate change is expected to erode precipitation. Converting 25% of the passenger car fleet to electric is estimated to result in a consumption incrase of 2.3 TWh, or 3.7% of the country’s total consumption. In macroscopic terms, replacing nuclear is therefore a far bigger challenge than converting cars from petrol/diesel to electricity. This conversion however only makes environmental sense if the substitute to nuclear is cleaner than fossile fuels.
Conclusion
Currently available battery electric cars are only selling in very low volumes: the 2018 marketshare was 0.6% in GB, 1.2% in France and 1.7% in Switzerland. Limited range, high purchase costs, practical constraints, the recipe for a wider adoption is not yet on the market. But from a climate impact standpoint, a broader adoption of electric cars would be beneficial to greenhouse gas emissions as long as the electricity source remains reasonably clean. The four studies reviewed in this article diverge in terms of assumptions and estimates, but all reach the same conclusion in this regard.
The temptation to deploy massive incentives should however be tempered. Climate change is by essence a global phenomenon, and investments into forestry projects in Indonesia or Brazil can have far greater effect than local EV incentives. This is the conclusion reached by a study of the University of Trondheim on norwegians EV subsidiessur which are judged to be wasteful.
It is also worth noting that the most ecological forms of mobility are 1) sedentary (moving less) 2) human-powered (walking, cycling) 3) public transportation (less than 10g/person-km the swiss rail company).
Links
Forum topic – hybrid and electric cars road tests – further reading:
