Let me share some #36C3 talks (Resilience and Sustainability track https://media.ccc.de/c/36c3/Resilience%20&%20Sustainability#t=6):
Reducing Carbon in the Digital Realm
Slides: https://fahrplan.events.ccc.de/congress/2019/Fahrplan/events/11113.html Recording: https://media.ccc.de/v/36c3-11113-reducing_carbon_in_the_digital_realm
Framing digital industry into planetary limits and transition policies
Slides: https://fahrplan.events.ccc.de/congress/2019/Fahrplan/events/11237.html Recording: https://media.ccc.de/v/36c3-11237-framing_digital_industry_into_planetary_limits_and_transition_policies#t=1548
Check out the category for more talks, they had an impressive track there.
Regarding Bitcoin: Assumptions here are tough. While the hashing power is known, the energy efficiency of the actual hardware used remains unknown (we only know that it varies widely). My diploma thesis focussed on the "fundamental value of bitcoin". Adam Hayes wrote a couple papers modelling a production cost model for the value of bitcoin, that may also be usable for making assumptions/calculations about Bitcoins power draw: https://adamhay.es/wp-content/uploads/2019/07/hayes-telematics.pdf
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