I think miners should start invest on renewable energy source (solar panels, wind turbines) to lessen the impact of bitcoin on environment?
I agree with you that investors on miners should invest on renewable energy but their power consumption not even a fraction of the industrial and manufacturing company.
There are already miners shift to renewable practice to save money. Renewable energy may expensive to start but it is more cheaper in the long run.
I do not think that there's a technology that is already existing where renewable energy will be available for mining. The best thing for mining rig to become more profitable is that your area will have a low electricity consumption, just like in china and that's the reason why 30% of the contributor in the market is coming from chinese miners.