Interesting article outlining the detriments (massive energy consumption and carbon dioxide emission) inherent with proof-of-work algorithms such as Bitcoin and Ethereum.

https://www.technologyreview.com/s/613658/bitcoin-mining-may-be-pumping-out-as-much-cosub2-sub-per-year-as-kansas-city/

This is one of the primary reasons we have selected proof-of-stake for the Aptum project. Additional to this, proof-of-stake as approached via our Pure-Proof-of-Stake implementation fosters network security and decentralization by rewarding only active participants with little financial barrier to entry.