No, Tesla batteries are not a global warming disaster

But, we probably should think about the supply chain.

A new report from the Swedish Environmental Research Institute has attempted to quantify the emissions tied to EV battery manufacturing. The study aims to better understand where emissions accrue in the supply chain and to shed some light on where we can do better.

In an early piece on the Swedish website NyTeknik, another researcher from the Swedish Environmental Research Institute, not involved with the original study, did some rough calculations and came to the conclusion that you would need to drive your new Tesla for 8 years (or drive a Nissan Leaf for nearly 3 years) just to break even on CO2 emissions. This later got picked up by English-language outlets eager to publish more “EVs are actually bad for the environment” takes.

But, of course, the devil is in the details. The payback conclusion gets complicated depending on where you live, how you charge the EV, and what your alternatives would be. This means some big differences depending on whether you live in the U.S. or Sweden. For example:

  1. Swedes drive less than we do,
  2. Swedes buy more efficient conventional cars than we do, and
  3. Swedish gasoline/diesel is cleaner than ours.

(On the other hand, charging from the grid is likely to be much cleaner in Sweden. More on that in a moment.)

The payback period assumes someone drives 7,650 miles/year, fuel is 18% bio-based, and that the average tailpipe emissions of new cars is 208 g/mile.

By contrast, in the U.S. we drive around 11,000 miles/year, our passenger fuel is mostly gasoline with 10% ethanol, and average tailpipe emissions are about 350 g/mile.

Of course, we also need to think about the emissions related to charging the EV during use. The Tesla driver in Sweden can top up with very low-emission power: Sweden’s energy mix is nearly 50% Nuclear and 50% Hydro. The average U.S. energy mix is more like 65% fossil, giving us emissions per EV-mile of something like 176 g CO2.

Once we account for higher-emission conventional cars one the one hand and charging from a higher-emission grid power on the other, it seems like the CO2 payback period is about the same in both countries.

Tesla’s Gigafactory is Carbon Neutral

The report assumes that the energy used in manufacturing the battery is 50% fossil-based. Tesla has long committed to making its Gigafactory carbon-neutral, and appears to be working towards that goal. The original research states that about half of the CO2 impact of battery manufacturing occurs at the battery plant, while only 10–20% comes from mining and the rest comes from materials production. That means, for the Tesla batteries at least, the CO2 emissions payback is halved.

A Cleaner Grid Matters Here

We saw the same debate play out a few years ago when researchers showed that if you charge a car from a coal-fired grid, your emissions reductions are limited. While that’s certainly true, the grid is getting cleaner over time. Today you could charge your Tesla from your home solar system, or — soon — from Tesla’s all-solar Supercharger stations.

The Bottom Line

Under the assumptions above, the CO2 payback for a 100 kWh Tesla battery comes out to about just under 3 years in the best case and 6 years in the worst case.

The average car in the US lasts for about 8 years, but many don’t expect EV batteries to last that long. On the other hand, lots of people are trying to figure out how (or whether) to give the batteries a second life, for things like stationary storage.

This research is a great step towards understanding the climate impact of a long supply chain, and it highlights the need to think about responsible sourcing and energy-efficient manufacturing. It should also highlight, yet again, that as transportation becomes increasingly electrified, a clean and reliable grid is more important than ever.

But, it doesn’t give you an excuse not to buy a Tesla.

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