The info you and others have provided gives me ideas for how to do it beter with distribution next time! Perhaps environmental groups could be encouraged to add some funding for library distribution into the budget of publication grant proposals.
At least for some publications, numerous free copies are mailed out. If we included certain libraries on our distribution lists for those free copies, we might well reach more people with our info.
By the way, I'd never heard the term "grey literature" before. Didn't know there was a name for what I've been doing all this time.