By Guest Author 16/10/2019 13


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There is a lot of discussion on the benefits of electric cars versus fossil fuel cars in the context of lithium mining. Please can you tell me which one weighs in better on the environmental impact in terms of global warming and why?

Md Arif Hasan, Victoria University of Wellington and Ralph Brougham Chapman, Victoria University of Wellington

Electric vehicles (EVs) seem very attractive at first sight. But when we look more closely, it becomes clear that they have a substantial carbon footprint and some downsides in terms of the extraction of lithium, cobalt and other metals. And they don’t relieve congestion in crowded cities.

In this response to the question, we touch briefly on the lithium issue, but focus mainly on the carbon footprint of electric cars.

The increasing use of lithium-ion batteries as a major power source in electronic devices, including mobile phones, laptops and electric cars has contributed to a 58% increase in lithium mining in the past decade worldwide. There seems little near-term risk of lithium being mined out, but there is an environmental downside.

The mining process requires extensive amounts of water, which can cause aquifer depletion and adversely affect ecosystems in the Atacama Salt Flat, in Chile, the world’s largest lithium extraction site. But researchers have developed methods to recover lithium from water.

Turning to climate change, it matters whether electric cars emit less carbon than conventional vehicles, and how much less.

Emissions reduction potential of EVs

The best comparison is based on a life cycle analysis which tries to consider all the emissions of carbon dioxide during vehicle manufacturing, use and recycling. Life cycle estimates are never entirely comprehensive, and emission estimates vary by country, as circumstances differ.

In New Zealand, 82% of energy for electricity generation came from renewable sources in 2017. With these high renewable electricity levels for electric car recharging, compared with say Australia or China, EVs are better suited to New Zealand. But this is only one part of the story. One should not assume that, overall, electric cars in New Zealand have a close-to-zero carbon footprint or are wholly sustainable.

A life cycle analysis of emissions considers three phases: the manufacturing phase (also known as cradle-to-gate), the use phase (well-to-wheel) and the recycling phase (grave-to-cradle).

The manufacturing phase

In this phase, the main processes are ore mining, material transformation, manufacturing of vehicle components and vehicle assembly. A recent study of car emissions in China estimates emissions for cars with internal combustion engines in this phase to be about 10.5 tonnes of carbon dioxide (tCO₂) per car, compared to emissions for an electric car of about 13 tonnes (including the electric car battery manufacturing).

Emissions from the manufacturing of a lithium-nickel-manganese-cobalt-oxide battery alone were estimated to be 3.2 tonnes. If the vehicle life is assumed to be 150,000 kilometres, emissions from the manufacturing phase of an electric car are higher than for fossil-fuelled cars. But for complete life cycle emissions, the study shows that EV emissions are 18% lower than fossil-fuelled cars.

The use phase

In the use phase, emissions from an electric car are solely due to its upstream emissions, which depend on how much of the electricity comes from fossil or renewable sources. The emissions from a fossil-fuelled car are due to both upstream emissions and tailpipe emissions.

Upstream emissions of EVs essentially depend on the share of zero or low-carbon sources in the country’s electricity generation mix. To understand how the emissions of electric cars vary with a country’s renewable electricity share, consider Australia and New Zealand.

In 2018, Australia’s share of renewables in electricity generation was about 21% (similar to Greece’s at 22%). In contrast, the share of renewables in New Zealand’s electricity generation mix was about 84% (less than France’s at 90%). Using these data and estimates from a 2018 assessment, electric car upstream emissions (for a battery electric vehicle) in Australia can be estimated to be about 170g of CO₂ per km while upstream emissions in New Zealand are estimated at about 25g of CO₂ per km on average. This shows that using an electric car in New Zealand is likely to be about seven times better in terms of upstream carbon emissions than in Australia.

The above studies show that emissions during the use phase from a fossil-fuelled compact sedan car were about 251g of CO₂ per km. Therefore, the use phase emissions from such a car were about 81g of CO₂ per km higher than those from a grid-recharged EV in Australia, and much worse than the emissions from an electric car in New Zealand.

The recycling phase

The key processes in the recycling phase are vehicle dismantling, vehicle recycling, battery recycling and material recovery. The estimated emissions in this phase, based on a study in China, are about 1.8 tonnes for a fossil-fuelled car and 2.4 tonnes for an electric car (including battery recycling). This difference is mostly due to the emissions from battery recycling which is 0.7 tonnes.

This illustrates that electric cars are responsible for more emissions than their petrol counterparts in the recycling phase. But it’s important to note the recycled vehicle components can be used in the manufacturing of future vehicles, and batteries recycled through direct cathode recycling can be used in subsequent batteries. This could have significant emissions reduction benefits in the future.

So on the basis of recent studies, fossil-fuelled cars generally emit more than electric cars in all phases of a life cycle. The total life cycle emissions from a fossil-fuelled car and an electric car in Australia were 333g of CO₂ per km and 273g of CO₂ per km, respectively. That is, using average grid electricity, EVs come out about 18% better in terms of their carbon footprint.

Likewise, electric cars in New Zealand work out a lot better than fossil-fuelled cars in terms of emissions, with life-cycle emissions at about 333 g of CO₂ per km for fossil-fuelled cars and 128g of CO₂ per km for electric cars. In New Zealand, EVs perform about 62% better than fossil cars in carbon footprint terms.The Conversation

Md Arif Hasan, PhD candidate, Victoria University of Wellington and Ralph Brougham Chapman, Associate Professor, Director Environmental Studies, Victoria University of Wellington

This article is republished from The Conversation under a Creative Commons license. Read the original article.


13 Responses to “The environmental footprint of electric versus fossil car”

  • Hi- could you explain a little more about the 251g of CO₂ per km for an ICE car? That’s noticeably higher than the CO₂ ratings normally cited for cars of this size. Does it include the cost of distributing and selling the fuel at service stations also?

  • 250g CO2 per km implies around 9.2km per litre consumption rate for petrol. For the average car (even small ones) on an urban cycle thats within the bounds of reason.

  • @Ashton Dempsey – I have a 13 year old 2l car that’s rated at 195g per km. A modern Suzuki Swift does 87g per km. A modern 1.8l Toyota Corrola does 147g per km. This all according to the rightcar.govt.nz website. To get to 250g per km the fuel economy would really have to suffer and we’d all be driving at extreme conditions. So I’m not sure it quite adds up.

  • There are two big failings in the analysis.
    The first is the extraction of cobalt and the rare earths (used in the motors). There is more cobalt in a lithium battery than lithium. The major supplier is the Congo, though the mines are controlled by the Chinese. The rare earths mainly come from China and have devastating environmental pollution.
    The second issue is the supply of electricity. The marginal supplier in New Zealand is coal fired power, and it will be fore the foreseeable future. Even on a windy day like today, we are currently producing more coal power than wind power. Every new car on the grid is powered by burning more coal.
    Taking those factors listed above into account changes the inputs into the analysis significantly. And that is without even looking at the problems of battery recycling. Don’t quote desktop studies – use real life experiences and the issues.

  • Hi Brendan

    “I have a 13 year old 2l car that’s rated at 195g per km. A modern Suzuki Swift does 87g per km. A modern 1.8l Toyota Corrola does 147g per km. This all according to the rightcar.govt.nz”

    They may be rated at that, but what is the real world performance?

    Our Volvo V50 does pretty well on the open road – probably around 13km/l . So, that is around 175g/km of CO2.

    Around town its about 2/3 that in Auckland, so about 8km/l and the proportional increase in CO2/km.

    87g/km for the Suzuki implies a fuel consumption half that of our V50 Volvo, so 26km/l or around 70mpg in the old money. I’m skeptical – that isn’t a real world result.

  • There are additional issues in respect to electric battery production and use of rare metals not being discussed. Given it is possible for some EV’s a 300% increase in Sulfur release into the atmosphere. This article is very good in expanding on carbon to consider water toxification and starting to discuss material embodied energy but the sulfur is the killer to our planetary environment future and needs yo be included within the assessments. Ultimately it is people’s behaviour not technology that will minimise our impact on the planet.

  • What is NZ’s capacity to increase renewable energy production? Can it do so at sufficient rate to maintain that 84% when electric vehicle’s become the norm? (assuming nuclear will remain a non-starter in NZ). If today I sold my petrol car and bought an electric vehicle, and draw more energy from the electricity grid, wouldn’t this simply result in an equivalent volume of extra coal being shoveled into Huntly power station and thus emissions reductions don’t look so flash at all? A “rapid, far-reaching and unprecedented change” (UN Special Climate Report, 8 October 2018, https://ipcc.ch/report/sr15/ ) in how we ‘do’ transport would surely be preferable.

  • @Ashton_Dempsey
    I think the estimates are an aggregate of part open road, part urban traffic estimates. I know I can do much better than say 195g on the open road but it is harder around Auckland.
    Lighter cars with smaller engines always do better than cars of the same age. And because of increasing fuel efficiency standards newer cars are also using less fuel than their older counterparts. There’s some stats on our light car fleet that shows this downward trend and it is quite remarkable. I did think the more reasonable explanation was that building a service station, powering it, and transporting the fuel to the station also generates a lot of GHG.
    My own strategy has been to bike a lot (which dilutes the GHG per km of weekly commuting) and well, use biofuel (Gull E10). And fuel efficient tyres that are kept properly inflated. Partly because I don’t use a car often enough to merit getting a new and expensive electric car. And partly because an electric car in my case, isn’t a very cost-effective way to reduce GHG emissions. Cycling is a very cost-effective way to make big cuts in my transport GHG

  • @Marcus_Wilson
    The amount of new renewable energy schemes supposed to be added is expected to take us to 90% relatively soon. That’s why most political parties were happily promising 90% at the last election. It was going to happen anyway.
    Electricity markets (at the wholesale/production side) is one of these odd markets where supply and demand need to clear instantly because (as yet) we don’t store it. Once the power is in the grid, there’s no way to apportion electrons between electric cars, TVs or ovens. What’s more relevant is when you charge. If you charge at offpeak times most of the power will come from renewables (hydro) so the contribution from coal etc will be less. If you charge at peak times, then there’s likely to be more coal/NG in the mix, but wholesale prices are also making adjustments. So some people/firms/users might use less as you use more. So it is complicated.

  • Brendan – You do not understand how the grid works and it shows.
    Moving the demand to off-peak just smooths the peak. It does not change the ratio of renewable to fossil fuel when spread over a day or week. No water or wind is spilled in the generation even now. In fact, if you reduce the peak by spreading the shoulders or moving into graveyard shift, it is more likely that the load will be generated by coal, not gas in an OCGT.
    Increasing demand increases coal consumption. Fact. That is why Huntly coal generation is up to nearly 400GWh per quarter. Unless the new generation matches that, they will still burn coal

  • Ultimately, the answer is that personal vehicles are, over time, going to be the exception. No matter the source of energy for movement, the embedded energy and the costs associated with the physical space occupied by the personal car will mitigate against the continued widespread ownership of such devices.

    When you consider the current state of housing in NZ, it is foreseeable that the two-car garage (a 40m2 space) as a standard feature of most mid-sized private accomodation will be a key motivation for going car-less. At current build prices of approximately $3k/m2, that economics of owning and storing a car are highly questionable.

  • @Ashton_Dempsey I think you’re largely right. Good point about the cost of garaging. And if cities insisted that roads were actually public spaces and that people couldn’t appropriate the patch outside of their house as their private car park, the cost of car ownership would be higher.
    There was a recent AA survey that showed people were driving less now than they used to. And a car is an expensive ‘asset’ to purchase and maintain for the use they get. Most private cars spend most of the day parked, shedding dollars of value in depreciation. It’s not a great economic prospect. PLus as you note the sheer physical area of space allocated to them isn’t cheap either.
    By my back of the envelope calculations, I can get roughly the same reductions in GHG (for commuting) as an electric car by biking most days, and running the car on biofuel instead. And the bike does actually reduce congestion 🙂

  • To reply to some of the points raised above, the Chinese study on which this article is based used well-to-wheel emissions for the petrol car, which explains the 250gCO2/km. Extracting, refining, and transporting the fuel adds about 25% to the emissions which was included. The NZTA has found that the average real-world fuel use in New Zealand is around 10l/100km which would equate to 290gCO2/km. The quoted study found that lifecycle emissions of the EV would be lower after about 13,000 km total driving. However, the grid is not that clean in China and the figures I have seen from US or European suggest a smaller breakeven point at around 8,000 km. This is for a small EV (27 kWh battery), a larger battery would have a longer breakeven distance.

    Studies of the NZ electricity market suggest that if more renewables are built, the first fossil-fueled plants to shut would be the remaining baseload coal and gas, which would lower emissions significantly. Even before then, I expect that the 240 MW of new wind starting construction this year will curtail some of the open-cycle gas. Time will tell. At some point, more storage or low-carbon baseload would be needed but that seems to be some time (more than a decade?) off.