Chia is about as close as you can get. Created by the guy who wrote Bittorrent.
Blockchains that don't use proof of work are as wasteful as any other electronic platform
Also proof of work can be translated into anything, like serving websites, images, processing video, and in that case is equivalent to any cloud or hosting provider
Blockchain itself cannot be carbon negative or neutral. Miners choose what energy source they use for mining, which can be anything from fossil fuels to geothermal energy from volcanoes.
Hyperledger ecosystem might be of interest, Fabric uses Proof of Authority by default
Have you looked into Nano?
no
Nah.
Longer version: Proof or work wastes energy by design, and while proof of stake is less wasteful, it is still not remotely as efficient or performant as modern banking systems. Proof of (hard drive) Capacity is wasteful of device production and running energy, and proof of elapsed time seems to be a lottery system, which looks likely to be difficult to secure in practice.