Well, once you move beyond proof-of-work, the energy use drops 99%. It's not about energy, it's about bottlenecks. Blockchain has bottlenecks, and if you have one blockchain for all the apps, it's going to be either inefficient or centralized.

Back in 2017, I designed a system to avoid global consensus:

https://intercoin.org/technology.pdf

If you want to see a visual presentation that explains why we need to go beyond blockchains, then check this out:

https://intercoin.org/intercloud.pdf