Bitcoin mining powered by hydroelectric is "green" - right?
I was at a Bitcoin Meetup last year, and the point of Bitcoin being "green" - as in the use of green energy came up.
We consider that hydroelectric power is fairly green energy. Or is it? Billy Garrison raised an interesting point which I had never heard before. That the reservoirs for dams release CO2. I had to look into this because it sounds like an interesting phenomenon.
I found this paper: Greenhouse Gas Emissions from Reservoir Water Surfaces: A New Global Synthesis
Sure enough - hydroelectric dams produce greenhouse gasses. It's not a lot but "... these emissions still contribute significantly to global budgets of anthropogenic CO2 equivalent emissions."
Diablo Dam © Steven Pavlov / https://commons.wikimedia.org/wiki/User:Senapa / CC BY-SA 3.0
Where do the GHGs come from?
The paper suggests 3 sources.
- Microbial decomposition of organic matter during the initial flooding of the reservoir,
- Variability in the depth of the reservoir (shoreline decay)
- Runoff of man-made material into the reservoir from the local land.
It is entirely feasible that hydroelectric dams are not as green as I thought! I learned something new.