Actually, there is a negative component to chasing after the latest and greatest in bicycles.

It creates excellarated consumerism with some people changing out bicycles that should last 50 years every 2-5 years instead. No matter what the material, that leaves a large footprint.

Recycling a used quality frame or sticking with what one currently has is the best environmental option IMO. For me that happens to be chromoly steel. My frame is 26 years old currently.