You can produce 28 aluminium bicycle with motors for the emissions of ONE Citroen C1 or 163 such bicylces for ONE Land Rover Discovery. The numbers for steel framed without a motor is nearly twice as high. It really does not matter what kind of bicycle you buy, as long as it lowers car usage it is a really good idea enviromentally speaking. Perfect is the enemy of the good.

tl;dr: e-bikes with a steel frame optimized for cost are more sustainable that weight optimized aluminum bikes.

I'm not sure that's the takeaway since they also talk about the multiple motor and battery replacements an e-bike needs over its lifespan undoing the initial lower emissions to manufacture, or how a well-built aluminum bike can last long enough to offset the higher carbon footprint compared to a poorly made steel one.

It seems the article is really pointing out that cheaply made bikes are the "problem". Bikes need to be built better (ideally locally so that bigger repairs are then feasible) and have better, more universal serviceable parts. Get more people biking instead of using motor vehicles whenever possible, and stop making the "disposable" tier of bikes so that switch is even more impactful.

tl;dr: e-bikes with a steel frame optimized for cost are more sustainable that weight optimized aluminum bikes.

I'm not sure that's the takeaway since they also talk about the multiple motor and battery replacements an e-bike needs over its lifespan undoing the initial lower emissions to manufacture, or how a well-built aluminum bike can last long enough to offset the higher carbon footprint compared to a poorly made steel one.

It seems the article is really pointing out that cheaply made bikes are the "problem". Bikes need to be built better (ideally locally so that bigger repairs are then feasible) and have better, more universal serviceable parts. Get more people biking instead of using motor vehicles whenever possible, and stop making the "disposable" tier of bikes so that switch is even more impactful.

... and I'm deeply skeptical of that. Bodies use a lot of energy sitting still and when we do work it's not all additional energy burnt.

On top, if you start bike commuting it's not necessarily extra exercise in your day. For a lot of people it'll be more a case of shifting how and when you get exercise. My commute's up to 7 miles with some hills now and I am absolutely doing less physical work the rest of the time as a result. I'm getting a great amount of exercise and having shorter commute time and saving a lot of money and getting healthier. Perhaps I eat more as a result of doing this commute, but I don't perceive it. I just eat the same meals at the same size as ever.

... and ... I don't remember the article justification for sure, but I seem to recall they were comparing the full lifecycle energy cost of the ebike, including ultimate disposal and reuse of motors and batteries. All in all, I frankly flat out don't believe it, though I freely admit this mostly my gut feel.