I think its well established that I know very little about the process of constructing surfboards but I'll offer my 2c
The life cycle of a surfboard strikes me as pretty high impact. They are made of foam that is quite toxic and epoxy and glues that are very, very toxic. These materials contain high levels of what are known as Volatile Organic Compounds (V.O.C.) If you want to get the environmental impact of your surfboards down then look at finding ways to reduce levels of these VOC's. Probably by using less epoxy or foam or finding a way to substitute them for something less toxic but that will still retain the performance you want.
There is a guy in europe called Corran who is producing surfboards that are supposedly very low impact. I've only had a cursory look at his website and not really at all at his production process but the hype seems pretty promising. They are called Imagine Surfboards. He posts regularly on the StandupZone and I wouldnt be surprised if he was here too.
www.imaginesurfboards.com/eng/eco-friendly-performance-surfboards.htmlGood luck!
