First of all, I tend to agree with Defmall, I truly believe this a is niche product, and you should concentrate all ur efforts on marketing to an "audience" that is willing to listen.  My self being an environmental scientist, I have to say that I sometimes get nauseated by organizations that use "green" or "environment" just as selling strategy; 

Having said that I HONESTLY don't think this applies to you but unfortunately for the public (i.e. online customers) all corporations (including small businesses) are guilty until proven innocent. So here is my suggestion:

In addition to the comments  Graig, Videography and Defmall made (making the green more obvious") you should not just give a blurb on sustainable development  but DO something tangible about it.  You could put a portion of your profits towards a cause that u feel strongly about. You can go to www.globalgiving.com and choose the cause or project that means the most to you (there are over 50 projects on Sustainable Devlpmt) and send 1% of ur profits (or whatever u can) towards funding it. Nothing stops you from linking your website to the project (s) you are now officially "funding". In my book, action speaks louder than words; 

Have a look at the pampers -unicef campaign: http://www.pampers.com/en_US/unicef_video_commercial.do

One pack-one vaccine. A vaccine costs 50 cents..50 cents!!! when a  see the commercial the skeptic in me can't avoid but think "another marketing plot" (but that is another story) but when you think about it, from a marketing standpoint, Pampers' has tapped in the "altruistic" side of their target audiences: mothers; If a mother has to chose between two major brands (huggies vs pampers) she will go with pampers because she feels that she helping another mother and her child. 

The cost for the "I will feel good about myself" feeling=50 cents

Profits for Pampers: unlimited

" AND I SAID TO MY SELF.....WHAT A WONDERFUL WORLD"!!!

cheers

Magda