well, HUMANS and everything they do isn't green. The problem is that this energy must be used to decipher the SHA256 hashes, which is how the btc supply is naturally regulated. If only there was some other low-power activity we could be doing instead this would be great.

How about every time you plant a tree you register the tree and get 1 btc...or something. Someones would figure a way to scam the system, the value will decimate, and people will lose faith and stop using btc. And anyway who is gonna issue you that 1 btc? The central bank of btc? I think alot of people participate in btc because its decentralized and anonymous, and the environmentally unfriendly methods we have now give the currency the unique qualities that make people want to trade in some of there dollars for it.