This is a great question!
The core team is actually working on getting an official answer in that at this time and will be releasing that information soon.
I can give my unofficial answer right now and then update the information here when the official answer is available.
Constellation's Hypergraph Network has a very low Carbon Footprint for many reasons.
1. Unlike Bitcoin the Hypergraph will have a set of rules to follow when it comes to being a Node Operator. On Bitcoin anyone can build a system and run a mining rig from home. Whereas Constellation recommends (and possibly will make mandatory) that all nodes be run from a VPS on DigitalOcean or Amazon Web Services (AWS). Both of these companies are trying to be as Green as possible.
2. The way $DAG is handled is much less intense then Bitcoin and the Hypergraph Network gets faster and more efficient as it gets busier.