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It was said on National Public Radio in the US that in most cases the carbon foot print from the exhaust off your old car would be less in a life time then carbon footprint to manufacture new cleaner car for you. So unless you are going from V8 to a hybrid it is better just to repair it for the Earth.

That made me think how far do you have to travel on a bike to equal out the carbon foot print it takes to make a bicycle or an electric bike?

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    I read that the diet of the rider/driver can have more of an effect on climate change than whether they drive a car or ride a bike. As for me, I like to put my bike on the back of my car, go get a burger, drive out really far, ride my bike around, and then drive back home and maybe get another burger on the way back.
    – user37012
    Commented Mar 23, 2018 at 14:35
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    Can we assume you mean how far to travel on a bike instead of driving a car?
    – Argenti Apparatus
    Commented Mar 23, 2018 at 16:33
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    You may have better luck asking the question on the Earth Sciences SE
    – Argenti Apparatus
    Commented Mar 23, 2018 at 17:13
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    I've changed the tags because its not road or mtb specific, its nothing to do with carbon which is a tag for carbon fibre, and electric is only slightly related. We don't really have a tag for "carbon" as in atmospheric. So @ArgentiApparatus 's suggestion would be a good idea. That said, its a good question because I have no idea.
    – Criggie ♦
    Commented Mar 23, 2018 at 23:38
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    @EvilSnack Do you have a reference for that rule of thumb? It does sound broadly plausible but it feels like gasoline could be a significant exception, since it's relatively easy to extract and refine, it's bought purely to be turned into carbon dioxide and its price varies very much between different locales. For example, the current average price in the US is about $2.60/gal, whereas in the UK it's about £1.20 per litre, which is about $5.74/gal.
    – David Richerby
    Commented Mar 24, 2018 at 11:33

1 Answer 1

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We can do some rough estimates. Let's assume that bikes are made exclusively of metal, and that only the mass of the bike counts (no energy consumed in welding etc.). Looking up the carbon footprints of aluminium and steel we have:

Material Tonnes CO2 per tonne material Source
Steel (tube) 0.857 NewSteelContruction.com
Aluminium (best) 3 CarbonTrust.com
Aluminium (worst) 20 Ibid.

So a bike weighing 10 kg would lead to somewhere between 8.6 (steel) and 200 (aluminium, refined using coal power) kg of CO2 emitted.

I couldn't quickly find reliable figures for carbon fibre or rubber, but metals are very likely to dominate based on the share of the mass in a bike, and the market share of bike frames.

Compared to an efficient car with 100 g/km of CO2 emissions, you'd have to replace 86 to 2000 km of driving with cycling for the emissions of making the bike to offset the emissions of using the car. This is a small enough distance that we can neglect other consumables. While not a direct comparison it's a helpful one—many people have a car and are being encouraged to get a bike and use it. Food makes things interesting. Strava claims I burn 26 Cal/km on a hilly ride. If I got that from eating beef alone (as a worst case), that would be something like 10 g of beef per km, or apparently 270 g CO2e per km. Of course we all know carbs are much better for powering our rides; typical sources are 10× better than beef.

Returning briefly to the original claim, when I've seen this claimed it tends to use low mileage figures, and neglect the fact that the metals in cars tend to be recycled (for Al this makes a big difference). It would make a good question at skeptics.se if you could source the claim more thoroughly.

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    I know this is only really a start, but I didn't want to go too far into it (and don't have journal access at home for solid values). As a bonus I can claim I chose a steel tourer for environmental reasons (pity about the MTB then).
    – Chris H
    Commented Mar 24, 2018 at 20:29
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    Trek Bikes released a sustainability report in 2021 that included estimated kg of CO2 equivalent to produce a number of bikes in its lineup. The numbers vary considerably. They're also hard to read and don't cover every single bike/frame. I think one takeaway was that carbon frames cost more CO2e. You're doing a surprising amount of heating when producing one. view.publitas.com/trek-bicycle/…
    – Weiwen Ng
    Commented Dec 10, 2021 at 20:10
  • There's a small math error in this answer. You'd have to replace 86 km to 2,000 km. I'll edit. As for beef, riding on an all-beef diet wouldn't be easy...
    – Therac
    Commented Aug 6, 2023 at 8:45
  • @Therac, good spot. And I certainly couldn't fuel myself on beef: I've given up eating ruminants completely and barely touch any meat, so I'd feel quite ill if I stuffed my face with it. But it's an easy worst case.
    – Chris H
    Commented Aug 6, 2023 at 8:49
  • Our edits coincided - I've changed that error but kept the worst case figure for Al. It is meant to be a worst case after all
    – Chris H
    Commented Aug 6, 2023 at 8:52

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