If you power that steam engine with wood or other natural (non-fossil) fuel, then it’s also carbon neutral … and might even be more environmentally friendly than charging it from grid power, since grid power may include coal and natural gas power plants.
Unless you’re charging your ebike with an inefficient, poorly-tuned gasoline generator, obviously yes.
And even then, honestly. You might have to be burning an oil drum for heat while you wait to be less efficient.
Coal fired steam engine to charge it.
Honestly would be kinda cool to charge a bike with a steam engine though.
If you power that steam engine with wood or other natural (non-fossil) fuel, then it’s also carbon neutral … and might even be more environmentally friendly than charging it from grid power, since grid power may include coal and natural gas power plants.