I know you are not specifically targeting a certain generation of potential employees, rather targeting environmentally focused talent, but I think this specific workforce also casts a large net over an intriguing group of people, Millennials.
While the age ranges may differ from study to study, Millennials are approximately 25 to 35 years old, we went through college as cell phones and email became a part of our everyday lives. Many times we are referred to as the entitled generation or trophy generation, neither of which are flattering monikers. But it is important to understand the negative connotation to these labels to be able to utilize these traits to your (employers) advantage.
Many of the descriptions of this generation include highlighting our desires to be involved in decision making processes, our distaste for being considered 'entry level', and the idea that our voices are just as important as the CEO's. While not everyone falls into these traps, the consensus is the same; we want to be a part of something bigger. Surveying suggests that we care less about titles, and more about opportunity to grow, great leadership and company reputation.
So how does this relate to environmentally conscious employees? We are the first generation to grow up saying reduce reuse recycle. We expect our companies and government to make environmentally sounds choices, and we are embracing the commercialization of organic foods and recycled goods. The point is this generation has been growing step by step with the modern 'green' movement. We will be raising our children in 'green' households; we will invest in sustainable building and development and leverage our dollars to support the companies we believe in. As we begin to find ways to bring eco practices into our everyday lives, we want to be a part of socially conscious companies that are doing the same thing. The opportunity to be a part of that growth, the green evolution, is intriguing. At the end of the day we can come home and say, 'I was a part of something big today'.

With all due respects to Adam, his is not the first generation to grow up saying

Of course lots of other generations have embraced recycling, and Marc's comment is a great analogy to discovering something that already exists. Recycle programs have been around for a long time, look at all the great government recycling programs instituted during WWII. But what I think is unique about this generation and recycling is that at the time our births the saying 'reduce, reuse, recycle' was mainstream and widely accepted as good practice. Obviously recycling programs have been around for a long time, but I think we might be the first generation to have never not known the motto from a very young age.
You always run the risk of missing some data when you make large generalizations about groups of people or generations, I try to use the analogies sparingly

I have to wonder if part of the answer to attracting a workforce committed to corporate sustainability is in knowing where and when to look. As a former Scoutmaster and parent of two Millenials who are Boy Scouts, I can tell you there are close to 80 other Millenials in our Troop who share our passion for the outdoors and the environment. From the time when they were Cub Scouts, we've ingrained in them the Outdoor Code, which says: