About 99% of the whole "carbon footprint" thing is crap.
The "experts" touting this drivel usually don't have a clue what they are ranting about, or they are scam artists trying to make a quick buck from the gullible.
Take, for instance, that massive instigator of "smug", the hybrid car that all the greenies and lefties HAVE to have.
If they ever considered just the footprint of the battery manufacturing and disposal, let alone the rest of the vehicle, they would just buy a bike.
Or a Hummer...