There has been a lot of talk about environmental effect of mining Proof-of-Work cryptocurrencies. People assume mining all cryptocurrencies will require enormous amount of electricity, even though it's only big mining farms that use a lot of electricity.
One of the arguments against mining farms is that they use so much electricity that there isn't enough left for normal daily needs of people who don't use cryptocurrencies (or even computers). This has been already proven to be not a fact, as mining farms use surplus electricity that would be otherwise wasted as alternate current can't be stored in batteries as when the voltage goes negative, it discharges the battery if there is no diode bridge to protect against reverse flow. Also, some mining farms or rigs, use solar power, which means they are not even connected to power grid.
Argument for supporting mining farms is that the heat they produce can be reclaimed and used for heating other buildings, or water.
Cryptocurrencies that can be mined with CPUs usually require so little amount of electricity (less than 100 watts, comparable to old 60W light bulbs) that bigger impact on environment is when the circuit boards are scrapped after end-of-life.
When some countries switched from using mostly cash to using mostly credit and debit cards or mobile payments, the need for cotton, chemicals and metals used in banknotes and coins went down, and number of required printing machines and coin presses. and operating hours for them went down significantly. This obviously reduced the amount of electricity that is drawn from power grid. A lot of chemicals are also hazardous to environment.
