From WhatsApp encrypting every chat to bitcoin as a secure & mostly anonymous way to transact, encryption and security is all the rage these days. Also all the rage is being eco-friendly & aware of how much energy we consume - but this doesn't naturally fit with security.
It's an old stat, but the quote below from a 2014 paper showed that even then bitcoin consumed as much energy as an entire country (Ireland). The distributed nature of blockchain, which is so important to maintaining a secure & true record when you don't trust your fellow participants, is by its very nature energy hungry. Nearly everything you can do to increase security (adding encryption, anomaly detection, managing permissions) also require additional energy. This is rarely an issue on a smaller scale, but at large scales it can be.
The blockchain ledger is a great example of a fundamental design choice that is tough to scale up, but it's the right choice. Without it you wouldn't have a key product feature. Sometimes though, casual choices in design can have similar implications to scaling up systems, and you don't want one of these creeping into your product by accident.
We also estimate under reasonable, reasonable assumptions, that currently the entire Bitcoin mining network is on par with Ireland for electricity consumption