You wouldn't believe it! there IS an environmentally friendly way of mining bitcoin. It doesn't require any GPU miners, nor a computer. Even a calculator is redundant. This is how it's REALLY done!
Watch the softmining legend Ken Shirriff validate blocks just with gridded paper and pencil
Ken's work is crazy inspiring. To actually understand how every single movement on the chain is validated, check his post here:
I think he's also calculated how efficient would the mining be was he to feed himself cheapest calory-rich food (yes..donuts). Turns out that chances of winning a block are so slim to nill it's not even worth theoretising about it making it completely unefficient.
But he isn't theoretising, he's doing it. And its so worth it! <3