Bitcoin issues an increasingly smaller share of coins to miners, in order to maintain their supposed guarantee of a hard cap of 21 million that will ever be created. This means that the price of Bitcoin has to double every four years just to keep the amount of money paid to miners the same. Bad for viability/security of the network, but good for long term carbon footprint prospects. Although it’s probably likely that there’s always going to be some kind of semi-scalable and fungible way to make money from running computations, so the failure of any one method isn’t going to be a lasting solution to environmental problems.