Feels like it's less cut and dry than this article suggests....

It's weird to me to assume the lifespan of a steel frame vs aluminum when only looking at a perfectly maintained bike. A poorly maintained steel frame rusts out way faster than a poorly maintained aluminum one (does the oxide ever get past the very outer layer?), and I'm not sure anyone bothers recycling the steel bike frame but they do recycle the aluminum one. Also, we're just looking at manufacturing, but wouldn't a lighter aluminum bike require fewer calories to move and therefore cause less carbon emissions from the rider over the lifespan as well? Never mind they mention transportation emissions of old vs new but what about new vs new? Would a local aluminum frame be better than a Chinese steel one, especially if considering the other points I've raised above?

I guess the point I'm trying to make is maybe now isn't the time to really be looking at this. Maybe get more people biking, any bike, and if it becomes a major enough form of transportation then we can worry about transitioning people from better to best.