CO2 legislation in the motor industry is based on what comes out of the tailpipe, but this is an inaccurate measure of real-world carbon footprints
3 May 2018

What is the world’s greenest car?

You could be forgiven for thinking that would be a simple enough question to answer; that there should be a list somewhere. After all, what comes out of the tailpipe is used as a basis for legislation.

Much more important, however, and ignored by legislation, are the cradle-to-grave CO2 emissions generated during a car’s lifetime.

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Life cycle assessment (LCA) is performed by most manufacturers, scientific bodies and engineering consultants such as Ricardo. The results can be revealing and sometimes contradict the simplistic yardstick of tailpipe emissions used today.

Ricardo breaks LCA into four main blocks: creation and distribution of fuel; vehicle production; vehicle use; and vehicle disposal. Each one of these categories generates CO2 and yet only the tailpipe emissions of the vehicle use phase are accounted for in legislation. 

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1. Creation and distribution of fuel

The first thing analysts consider is the primary energy source – where the fuel comes from. It’s obvious that petrol and diesel, derived from crude oil, create tailpipe emissions, but factor in the energy used to extract and refine them and the CO2 burden goes even higher. Biofuels still produce CO2 emissions at the tailpipe but it’s compensated for by the absorption of CO2 when the crops used to make it were growing.

Any CO2 liberated during their production and distribution should be included in establishing green credentials. The CO2 emissions from battery EVs during use depends on the sustainability of the electricity used to charge them.

2. Vehicle production 

The CO2 burden of any car starts even before the idea has been signed off. The design and development process – testing and movement of thousands of people, together with heat and light for offices – contribute to small amounts of embedded CO2. The production phase is the bigger villain, taking into account the supply chain, from raw materials to finished product. The choice of materials, powertrain, size, weight and the number of components all affect the car’s carbon footprint.

3. Vehicle use

This is where the tailpipe emissions come in but, according to Ricardo, it can represent only 70-80% of the lifetime CO2 burden of a medium-sized petrol car, assuming a lifetime mileage of 93,000. Some 15-20% of a car’s lifetime CO2 can be accounted for by production alone. For a medium-sized battery EV, the production element is even greater, with around 52% of CO2 indirectly from the ‘tailpipe’ depending on the electricity mix used to charge the car, compared with 46% during production.

A medium-sized diesel car will emit less CO2 during use, but more during production, so the cradle-to-grave emissions of equivalent-sized petrol and diesel cars are about the same. Maintenance, including parts and consumables, will also make a small contribution.

The measurement of CO2 in Europe is based on the NEDC test, which was replaced by the more real-world-focused WLTP test in September 2017. It’s widely acknowledged that NEDC figures are optimistic compared with real-world consumption, yet they have long formed the basis for, and skewed, official European CO2 figures, with real-world testing only now beginning to be implemented.

4. Vehicle disposal

Much as with production, the size and weight of a car, the technology and number of components in it and the materials used all affect what the CO2 impact will be at the end of the car's life. So do the logistics of dismantling it, the people involved, the recycling of material and the waste. If the car is easy to dismantle and has a large quantity of parts that can be remanufactured, then its CO2 impact will be lower. Although ‘end of life’ is mandated by an EU directive, there’s not much information available today about CO2 emissions from some aspects of it, such as processing.

How do conventional cars and electric cars compare? 

Battery-electric cars still produce less CO2 during their lifetime than petrol and diesel cars, based on 500g/kWh of CO2 emitted during electricity generation. In fact, the UK National Grid is much cleaner today at around 300g/kWh, making battery EVs even cleaner too.

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Nearly half of the total life cycle CO2 of an EV results from production, though, with the battery alone accounting for more than 40% of that. For that reason, in the unlikely event an EV were to need a battery replacement during its lifetime, then its cradle-to-grave CO2 emissions would come close to that of an equivalent-sized petrol car.

The amount of CO2 produced in making an EV’s battery could fall as numbers ramp up in plants such as Tesla’s forthcoming Gigafactory. Optimised production techniques and the use of renewable energy for plants would also help. But one thing is certain: no EV can truly be described as ‘zero emission’.

How carbon footprints differ: 

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There are specific regulations in Europe for reducing the impact of a car during the fuel, use and disposal phases, but there are no targets in place for the crucial production phase.

There’s work to be done before LCA could form the basis of regulation and Ricardo recommends the creation of a central database with details of the carbon content of materials and processes, finding out more about the environmental impact of a car coming to the end of its life, a closer look at emissions during use and more.

Overall, there’s increasing evidence to suggest that using LCA instead of the existing system would be a more accurate way of measuring the carbon footprint of cars. More important, it could give a startling new insight into what is truly green and what is not.

How car size affects carbon footprint: 

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Comments
30

3 May 2018

So when an EV uses electricity from a green source nothing can beat it. So it's logical to have more EV's and build more offshore wind farms, hydro plants, solar farms etc.  

typos1 - Just can’t respect opinion

3 May 2018
It depends on how you define pollution. Day after day I am forced to stare at an example of how the VISUAL pollution of wind farms are destroying vast areas of the Country.
And just wait till the current turbines start aging and need replacing!

3 May 2018
Lapps wrote:

It depends on how you define pollution. Day after day I am forced to stare at an example of how the VISUAL pollution of wind farms are destroying vast areas of the Country. And just wait till the current turbines start aging and need replacing!

Agree, not to mention the noise pollution from turbines, nuclear is they way to go...

#Dieselsforlife

3 May 2018

OMG are those 2 quotes from above for real ? ! Wind turbines look ok and besides the clean energy they produce far out weighs their looks, as for nuclear, how could anyone seriously suggest that the dangers of nuclear fission energy should be pursued cos they dont like the look of a few wind turbines, besides, nuclear fission is the single most dirty energy source there is.

XXXX just went POP.

3 May 2018
typos1 wrote:

OMG are those 2 quotes from above for real ? ! Wind turbines look ok and besides the clean energy they produce far out weighs their looks, as for nuclear, how could anyone seriously suggest that the dangers of nuclear fission energy should be pursued cos they dont like the look of a few wind turbines, besides, nuclear fission is the single most dirty energy source there is.

Wind turbines do not look ok in my opinion, they’ve blighted many beautiful areas in the north east of Scotland. Subjective I know. They’ve just started installing huge wind turbines close to the shore of Aberdeen too, and it ruins the beach view. They might be the lesser of the evils, but they are not ok to look at when dotted over beautiful scenery  

Of the renewables wind is the most likely, and is relatively emission free. Other renewables don’t seem to have the ultimate capacity, so we’re still going to need back up generation for low wind conditions. Nuclear has waste issues and needs serious money (don’t build them in tsunami areas for example - Japan we’re talking about you!). What’s worse - x tonnes nuclear waste stored safely, or x tonnes CO2 in the atmosphere? 

Gas is better than coal, but I don’t buy the whole carbon capture thing as it’s a short term gimmick even if someone makes it work. So if it has to be fossil fuels then let it be the cleanest ones.

Then you have all the geopolitics of surrendering control to foreign companies and investors, having fuel supply dictated by Russia and Qatar for example.

Electricity generation is a nightmare for politicians in the UK, and 20 plus years all the parties have avoided major decisions like the plague until the EdF Hinckley plant, and that’s an absolute consumer price disaster. Needs a government who are prepared to sacrifice their party and build a policy and put it into law, and there will be dissenters whatever they decide, so they’ll get voted out. Oh for some decent cooperation between cons and labour to get something done.

 

Add in the move to electric cars to the supply issue too.....

3 May 2018

Indeed and thats what we re doing. But its also logical to carry on using cars that exist currently til they reach at least 300,000 miles and retro fit retro fit emisions equipment, cos wastefully scrapping them and building more to replace them is definitely NOT good for the environment at all, even if these replacement cars are EVs. Sadly most people (including governements and you) cannot see this so we produce more "green" cars to be "better" for the environment, when in reality its 100% worse.

XXXX just went POP.

3 May 2018
typos1 wrote:

Indeed and thats what we re doing. But its also logical to carry on using cars that exist currently til they reach at least 300,000 miles and retro fit retro fit emisions equipment, cos wastefully scrapping them and building more to replace them is definitely NOT good for the environment at all, even if these replacement cars are EVs. Sadly most people (including governements and you) cannot see this so we produce more "green" cars to be "better" for the environment, when in reality its 100% worse.

If you lose the 20% non running manufacturing, etc emissions by scrapping an old car then it is clearly better overall to replace it with a new car with half the running emissions. Don’t see any retrofit emissions tech on the market for now, so unless it’s very cheap then it won’t be fitted to valueless old cars anyway. Need to target the worst emitters first for scrap - this will mean the former owner will have to buy another probably used car, and create demand for a new lower emissions car? So get rid of the worst first. 

3 May 2018
Great article I actually learnt something today. It deals another telling to the dirty diesel lobby. Americans have worked out a way to quote emissions for EVs. They do not have tail pipe emissions but they do have some emissions which are produced while making them and while generating the electricity that drives them. Where electricity is produced from renewable resources the emissions come down further. In that graph the most shocking thing for me is the minuscule difference that divides the EV and petrol PHEV - assuming that they are electrically charged every time they are used. Amazing and informative article. Thank you.

3 May 2018
This article assumes that the production of biofuels is clean - and this is where it's stupidly wrong. Do any research on mass biofuel production and you'll be horrified.

3 May 2018

Indeed, a lot depends on whether the biofuels are made from genuine waste products, or whether large areas of arable land (which could be used for food production) are instead producing fuel.

Or worse still if rainforest and other wilderness areas are destroyed to produce it...

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