Also, the name Earthcoin suggests to me that it may be somehow more sustainable with regards to the computing resources required to support it; is there any basis in that? 

The official site appears to be <http://getearthcoin.com/> which has some pretty logos but is woefully lacking in technical detail. As it probably always the case with an altcoin, it also has a [thread on bitcointalk.org](https://bitcointalk.org/index.php?topic=379236.0) which seems to describe a very odd block reward system with some days paying 2 or 5 times the normal block reward.