A few years ago, a story began spreading that the Toyota Prius hybrid consumed more energy over its lifetime than the vast Hummer H3 off-roader. This claim was rapidly debunked, but it did raise an interesting question: Just how green are hybrid and electric vehicles (EVs) once you factor in everything from material extraction to end-of-life recycling?
Various engineering consultancies and non-profit organisations have released comparative studies into the lifecycle impact of EVs versus combustion-engine models. But Volvo-spinoff Polestar recently became the first car manufactured to do so publicly, with an in-depth lifecycle assessment (LCA) that compares its own all-electric Polestar 2 with the petrol-only version of the Volvo XC40.
“The results of this study are important, but equally important for us was to publish our methodology,” explained Lisa Bolin, climate lead for Polestar. “When I looked at the work that was out there already, I was quite surprised – coming from a research background – at how difficult it was to follow the methodology. So we set out with our colleagues at Volvo to put together a lifecycle assessment that was completely transparent.”
The numbers
The headline figures are interesting – but perhaps not greatly surprising. With 350kg of lithium-ion battery modules onboard, an all-up weight that’s 25 per cent heavier than the XC40 and a larger share of energy-intensive aluminium and electronics, the Polestar 2 does indeed require substantially more energy to produce.
Combining material extraction and processing, manufacturing, and the various transport stages in between, the study estimates the carbon footprint of a Polestar 2 at 26.2 tonnes CO2-equivalent at the point it rolls off the production line, whereas the XC40 sits at 16.1 tonnes. That makes the electric car’s initial impact more than 60 per cent higher than that of the petrol model.
However, the figures show a very different story over the complete product lifecycle of 200,000km. With a typical European electricity mix, the equivalent CO2 production during the use phase is slashed by around two thirds compared to the XC40; switch exclusively to wind power, and it’s less than a tenth of the impact (0.4 tonnes for the EV versus 41 tonnes for the petrol car).
The end-of-life treatment is fractionally less impactful for the EV too, accounting for 0.5 tonnes of CO2-equivalent, as opposed to 0.6 tonnes. Combine all these factors, and the lifecycle carbon footprint of the Polestar 2 is around 28 per cent lower when running on a standard European electricity mix, or 53 per cent lower on wind power alone.
“Broadly speaking, there weren’t too many surprises with the results,” said Bolin. “We knew from other studies that the batteries, the aluminium and the steel would be the main contributors. But at the same time, it emphasised the need to work on a holistic solution; we have to work on all fronts, looking at the body structure, the chassis and the interior to reach our goals. Going from a twin motor design to a single motor design, for instance, doesn’t make that big a difference on its own.”
The methodology
Essentially, the LCA provides a convenient way to collate and analyse information that’s already out there. Much of it was compiled using generic data, with each component broken down into material categories by weight. For instance, a part might contain 500g of cast aluminium, 250g of deep drawn aluminium and 125g of unalloyed steel.
This information is taken from the industry-standard International Material Data System (IMDS) and matched to separate datasets that give the CO2 impact by mass for each material and process. This sounds straightforward, but the first issue is the sheer complexity of a product the size of a car. Even employing some fairly broad generalisations, there are thousands of components sub-divided into more than 70 material categories.
In some cases, there can be numerous different terms to cover broadly similar processes or tradenames that are submitted to the IMDS in place of a physical description of the material. Volvo developed a tool to help filter and sort the definitions, but in some cases, Bolin and her colleagues had to break it down further.
“We had to go into the individual data sheets for some components to really check what was inside them. For instance, when it comes to electronics, we don't put small, low voltage electronics and high-voltage contactors in the same category,” she said. “There are also different datasets out there, so we had to compare those and understand which are the most reliable.”
Where generic data has been used, Polestar has taken care to reference global datasets to account for variations between different regions and suppliers. For instance, it’s assumed that the manufacturing processes are carried out with a global energy mix rather than best-case scenarios, such as factories run exclusively on renewables.
For some components, however, more accurate product-specific data has been used. The main example of these is the battery pack, Bolin explained: “We knew from the beginning that the batteries would have a big impact, so we collaborated with our suppliers CATL and LG, with data taken direct from their production sites. Likewise, we have detailed data on the parts that we manufacture in house. The rest is generic information, but we’re working to get more exact data from external suppliers.”
Track and trace
Polestar is now working with supply chain specialist Circular to digitise and track its materials using blockchain. The two organisations have already collaborated on a project to trace the cobalt used in Polestar’s batteries to ensure it’s not linked to any human rights abuses in mining. The same methodology can be used to do a deep dive into the carbon footprint of the materials.
In some cases, it may be possible to make significant improvements with relatively fundamental shifts. Bolin gives the example of aluminium smelting with renewable energy rather than coal, which is potentially an order of magnitude greener for the same end result. “Locating our smelters in areas with renewable power can make a big difference with just one change,” she said.
As an increasing number of vehicles boast zero tailpipe emissions, more attention is being paid to their lifecycle impact. “We really want to show that you cannot just buy an electric vehicle, and say ‘that's okay, now I’m being sustainable’,” said Bolin. “From a manufacturer’s perspective, we have to take responsibility for the whole value chain. And that's maybe something that has not been a priority in the automotive industry historically, due to the focus on tailpipe emissions.”
For this to happen, the industry will need a standardised methodology for carrying out LCAs. “It doesn't have to be as rigidly defined as an ISO standard, but I think that we as an industry have to come together and decide on at least a basic framework,” Bolin said. “The first step is to be transparent on the various assumptions that people are making. We want to start a discussion on how we can agree on some common practices.”
A framework like this could have far-reaching consequences for the future of the automotive industry. It’s not hard to imagine vehicles one day being ranked on their lifecycle impact, as they currently are on tailpipe emissions. And while the debate rages on as to which technologies should power the next generation of passenger cars, the results of this study are a reminder that the manufacturing impact will always be too significant to ignore.
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