I'd always suspected it would be high, not from mining as this article claims, but as a result of the storage of each Blockchain entry. If you accept that CO2, is a problem, then Bitcoin is also.

I think there is an error in the second paragraph: "For a Bitcoin transfer to be executed and validated, a mathematical puzzle must be solved by an arbitrary computer in the global Bitcoin network. "

As I understand it, the maths puzzle is involved *only* in the mining i.e. creating, of Bitcoins. Worse, as the number increase, the puzzles require increased computing power. Again, as I understand it, the creation of a Blockchain record as a result of a transaction requires little electricity - but how much is required to maintain that record? Go figure!