Did a quick search on the forum but didn't find anything directly relevant; excuse me if this has been suggested before.
With respect to pollution and an ever increasing deforestation of the environment, eco-savvy players might want to "go green" and (re)plant some of that lovely, dovely green heritage.
My suggestion:
- Make trees drop seeds/saplings sporadically that allow the player to plant new trees and thus combat deforestation/give their factory a little touch of nature.