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Unlike the rest of car sales in the UK, which are currently in decline, the uptake of so-called ‘green’ cars – electric vehicles (EV) and hybrids – actually increased by nearly 40% between 2016 and 2017.

According to those same figures from the Society of Motoring Manufacturers and Traders (SMMT) they sold as many by October this year as they did in the whole of 2017. Forecasts suggest that by 2040, 55% of all new car sales globally will be EVs.

With the scandal at Volkswagen over their manipulated diesel emissions, worldwide (almost) pledges to clean up air quality and reduce CO2 emissions, the reducing prices, and government grants assisting people to make their motoring more environmentally friendly, it’s hardly surprising that many people are looking to reduce their own carbon footprints.

On the face of it, the impact of green cars is less than a third of that of internal combustion engine vehicles (ICE). Looking at figures from carbonfootprint.com, based on vehicles charged from the UK mains, the emissions of driving 10,000 miles are as follows:

Average Electric Vehicle: 0.96t CO2e
Average Petrol Car: 2.99t CO2e
Average Diesel Car: 2.88t CO2e

The green credentials here are hard to ignore, but it’s important to remember that emissions are only half the story, and for the purposes of this piece we’re not including hybrids because they do, of course, have a separate combustion engine.

The truth is, when it comes to ‘green’ credentials there is no such thing as a zero-emissions vehicle.

While governments legislate based on exhaust emissions, a vehicle’s emissions don’t start at the end of the production line as it hits the road or the forecourt, but rather at the beginning of it. The figures from manufacturers and engineering consultants take this into account in their lifecycle assessments (LCA), and these figures suggest something quite different from what we might expect.

The first item when looking at a car’s LCA is its fuel creation and distribution. When it comes to fuel, we all know that petrol and diesel generate exhaust emissions when they’re consumed in the engine, but once you account for the amount of energy that goes into extracting and refining that fuel, those figures rise considerably. They rise further still when you account for distributing both the crude oil to the refineries and the final fuel distributed around the world.

Next is the vehicle production. Think about that from the beginning: the design and development – the movement of designers, engineers, operators, the running of offices and factories – it all contributes. It’s the actual factory floor, though, where most of the CO2 is generated when you factor in the supply of raw materials and the power required to create the finished product.

Vehicle use is where our exhaust emissions come in, and it’s here and in the production where we see the biggest differences between ICEs and EVs.

Over a lifetime, exhaust emissions account for 70-80% of a medium-sized petrol car’s total COemissions, with 15-20% accounted for by production. A medium-sized diesel car emits less through the exhaust, but more in production, and so the two almost equate.

On the other hand, a medium-sized EV creates 46% of its lifetime CO2 in its production phase (with 40% of that percentage just being the battery) and, depending on the energy source, 52% indirectly through daily recharging.

One of the big problems with the batteries is the materials used to create them. Some, such as lithium and cobalt, are quite rare, and at the moment the environmental impact of the mining and processing of these materials, not to mention the distribution and so on, seriously affects those precious green credentials.

That said, of course, if you only recharge at home and your energy supplier uses only renewable sources of energy, that 52% is going to shrink a lot and will reduce the overall lifetime carbon emissions of your EV considerably.

Finally, when it comes to the lifecycle assessment we need to look at the end of a car’s life and its disposal. For this, the CO2 emissions come from the logistics and process of dismantling, and the energy sources used to do it. It will also vary according to the size and weight of a car, the technology employed in it, and the number of people involved in the process. Due to the vagaries of current EU directives on ‘end of life’, there is very little specific information on the CO2 emissions at this stage of the LCA, but by and large, it remains a relatively tiny amount compared to fuel, production, and use.

Looking at percentages only, EVs are looking decidedly less competitive, but that can be misleading when there are so many variables, so let’s look at some more figures. These are approximate and come from engineering consultants Ricardo. They are based on a medium-sized petrol car vs a medium sized EV.

The full totals also incorporate approximate figures for disposal and the small number of vehicles using biofuel.

The figures demonstrate that, over its lifetime, an EV produces only 25% less CO2 than its petrol counterparts, rather than the 66% the earlier figures suggest.

To answer the initial question? Yes, they are greener, but they’re not as green as “zero emissions” and “green” car salesmen might have you believe.

We mentioned variables, though, and those EV figures are based on normal electricity consumption from a power grid using a percentage of fossil fuels.

If we look at that again, drawing electricity from only renewable resources you see the lifetime CO2 emissions of the average EV plummet to 8,500kg against petrol’s 24,000kg, because the 10,000kg “use” no longer applies. While the current infrastructure might not yet be up to the task of providing only renewable energy, the fact that EVs can do so, and will continue to do so, gives us hope for the future.

No matter which way you look at it, a combustion engine is always going to produce CO2, even if its entire production was able to run on renewable energy.

For EVs, their CO2 emissions are only ever likely to decrease as battery production becomes more efficient and as manufacturing and the power infrastructure that fuels the cars moves more toward renewable sources.

Green cars might not be as green as we may have been led to believe, but they’re still the greenest we’ve got, and they’re just going to get greener. The same can never be said for combustion engines.