This is a pretty straight forward article. Nora Young addresses the potential future issue of energy usage that mining bitcoin requires and speaks with someone who has studies this topic more thoroughly. She points out a couple possible (unappealing) solutions.

This article is correct on many fronts. It's true that Bitcoin needs to solve its energy problem if it seeks to scale and be used for mainstream transactions. It's also true however that Bitcoin can be massively valuable even if it never serves as a transactional currency and instead remains as a store of value(digital gold). Ethereum, which the author mentions in this article, is attempting to solve the energy/trust problem by moving away from Proof of Work(costly mining of coins) over to Proof of Stake(staking your Ether as you validate future blocks). It's true that Proof of Stake disproportionately rewards those that got in early on Ethereum, but it also creates disincentives to maliciously attack the blockchain which is perhaps more important in the longterm. Teunis Brosens' idea of having "trusted" nodes in the blockchain such as regulated banks completely defeats the purpose of a decentralized monetary system. Bitcoin and the rest of the crypto-community would never support it, therefore it should hardly qualify as a proposed solution.

Much like the title eludes, the electrical power used to mine bitcoin is currently not a sustainable form of security. The article's argument lies on the shoulders of one key expert so there could be room for further backing up any claims mentioned.