I read that a lot of electricity is consumed in mining bitcoins. Is block chain bad for the environment?
A lot of human resources is consumed by banking and finance. Cryptocurrencies could free up much of what is basically a waste of workforce.
You can operate a blockchain without any mining power needed if you would want to. It's simply a ledger that isn't distributed by a central system, but rather peer 2 peer. Look at ripple et al. They don't need hashing power.
Ripple is centrally issued and requires a network of trust. Ripple and the likes of it fail at providing some of the core value propositions made by cryptocurrencies, namely being permissionless, trustless and decentralized.
I would however conclude that the bitcoin mining process is pretty wasteful. With most miners located in china (where clean energy is a word they don't know.)
You might want to rethink your conception of China:
https://www.theguardian.com/environment/2018/jan/10/china-on-track-to-lead-in-renewables-as-us-retreats-report-says