"Im sure most of you have seen the news about Bitcoins energy consumption. For instance, in Iceland, more energy is used to mine Bitcoin than to power peoples homes and per day the global Bitcoin network now consumes more energy than Ireland. Hence, we chose to build on the Stellar network as it is the most environmentally friendly blockchain available. For comparison, a transaction on the Stellar network only uses 0.03 Wh whereas VISA uses 1.69 Wh per transaction. Clearly, the Stellar blockchain is the perfect technology partner for our platform."
Read morehttps://datafloq.com/read/amp/blockchain-can-save-climate-poseidon/5235?__twitter_impression=true
You can run different decentralized consensus systems that don't burn nearly as much power as Proof of Work. But the thing is that PoW is the one that is proven and demonstrably secure by having a very clear cost to attack that is extremely high. It's possible some of the alternatives will stand the test of time, but PoW in pretty solid.