#Bitcoin has a dark side: its carbon footprint
▻http://pando.com/2013/12/16/bitcoin-has-a-dark-side-its-carbon-footprint
Bitcoins aren’t mined from the earth’s crust like most physical commodities – although at least that leaves tangible evidence of its environmental impact. Rather, they are “mined” by computers solving a set of complicated computational problems. These problems are designed to get more difficult over time, until the year 2140 when the 21 millionth (and final) bitcoin is mined. Early in bitcoin’s existence, it was feasible to run a successful mining operation with a standard PC. Now the task requires custom mining rigs that can run orders of magnitude more processes per second.