transport

Reducing the embodied emissions of cars

There are two elements to consider when assessing the carbon impact of a car: the CO2 from using it over the course of the vehicle’s lifespan, and the embodied emissions from making it in the first place. For the average family car, 20-25% of total emissions come from production, and the rest from driving it.

Electric cars are a little different. We all know that they are better for the environment, provided the car is charged from renewable energy. But they are more complicated to make, especially the batteries, and so they have higher embodied emissions. There are stories on the internet suggesting that a 4×4 is ultimately better for the environment than a Toyota Prius, or a Tesla (or insert hate object of choice). These are nonsense. An electric car or hybrid starts with more carbon to its name than a fossil fuel equivalent, but it will clear that over the course of driving it and perform better in the long run.

But it is a problem. As more and more electric cars take to the roads, the embodied emissions slice of total emissions will get larger. Eventually it will be a bigger decarbonisation problem than driving, and that calls for imaginative solutions. So how do we reduce the embodied emissions of vehicles?

One obvious solution is to use recycled materials where possible, especially metals. That saves the emissions from mining and processing new ore. If a car is recycled at the end of its lifetime, then its embodied emissions will be reduced as materials are shared across multiple vehicles. Electric car batteries can also be recycled. Moving to a circular economy model for car manufacturing will ensure that materials are well stewarded, saving emissions throughout the supply chain.

Another big component of embodied emissions in cars is the electricity used in production. Car companies are aware of this, with many aiming for renewable energy in their factories. Tesla hopes to make their battery gigafactory net zero by producing as much clean energy as it uses. With an eye on their target market, Toyota builds the Prius in an ‘eco-factory’ in Japan.

Manufacturing is a global business, and cars are assembled from parts that are made all over the world. It isn’t always possible to make everything on site, but reducing the distance that parts travel helps. How things travel matters too, with a preference for rail where possible, and slow sea freight.

Another way to reduce embodied emissions is to make lighter weight cars, and that does seem to be easier with EVs. New materials and composites have a role, including moving away from metals altogether. Among the most radical proposals is this experiment from Holland, which I shall make the transport innovation of the week – a biodegradeable car made from beet sugar and flax. It’s not an entirely new idea. Henry Ford made a car out of soy plastic in 1941, in response to metal shortages. Neither is it a technology that can be immediately adopted, as it doesn’t meet safety standards. But it does show what’s possible, and the variety of approaches that we could still adopt. You might want to keep it in the garage.

9 comments

  1. To me it make sense to refurbish cars rather than recycle them. However, cars are status symbols and although I’d be happy with an older car that’s been refurbished many people would not.

    You focus on carbon but make no mention of the rare earth metals that are so important in making high performance electric motors and batteries. These are scarce substances, often mined in unstable countries. These MUST be recovered and reused, unless the things made from them – batteries and motors – are reused as you mention.

    1. Good point on rare earth metals, those need to be recycled as much as possible. EVs don’t depend on them as much as one might think though – it’s a recurring theme among those who oppose them, but not all EVs use them. It depends on what kind of motors they use. Those with induction motors don’t need them, and there are several of those on the market.

      Batteries without rare earth metals are also possible. Honda developed one last year. The car companies have every incentive for doing so – rare earth metals are expensive and heavy. And needless to say, rare. China has restricted exports in the past, so it’s totally in the industry’s interests to develop alternatives.

    1. I’m with you on that, but cars aren’t exactly going to disappear in the coming years. Even if we make far fewer in future, and I share your hopes there, we’d still want them to have the lowest possible embodied emissions.

      1. You are right as well, but there is method in my madness. With cars you always have a lot of talk about how they can be improved- lower emissions, electric cars, self-driving cars etc. which no doubt suits the car manufacturers fine, but ignores the issue of whether there is a real need for the amount of cars which exist. Making the manufacturing process more energy efficient or otherwise less polluting per unit of production is a good thing up to a point, but I am sure far more impact can be made by simply reducing the number of units since each must have a non-zero amount of embedded emissions.

  2. Interesting article. However, am I wrong in thinking that driving style and reduced speed limits could also have a huge impact on CO2 emissions? I have a Diesel Skoda Octavia and actually managed 100mpg on a recent motorway trip driving around 55mph. I have a photo sitting at 98.6mpg if you can use it?

    1. You’re right, and I should do a post on that. Actually there are a couple of ideas there, driving style and reduced speed limits. The first is something any of us can do any time we like, and I use a handful of efficient driving techniques myself. Lowering speed limits would also bring down CO2 levels, though I can only imagine the screaming it would induce from the tabloids. We can all voluntarily reduce our speeds too of course, though doing 55mph on the motorway takes a fair degree of patience!

      If you send me the photo I might be able to use it if I write about efficient driving. If you’d like to collaborate on a post, let me know.

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