Do you know how much carbon dioxide is produces by printing paper currency and how many trees have to be cut?
in my simple mind any new digital currency that is such a HUGE resource hog won't be sustainable either in the long run. feel free to persuade me that i'm wrong
one thing that does not affect mystical carbon footprint is sitting still without breathing (well, at least until you start to decompose) why not to try that instead of bitcoins?