It depends on whether your manuscript is fiction or nonfiction. Most publishers of nonfiction pbs are looking for green themes. BUT--and this is a huge one, you'll need a unique slant on the topic. (I use the Amazon Advanced Search option to do preliminary research on what's already been published.) Also, if it's nonfiction, try to get an expert or two to vet your work, and possibly recommend it.
If it's fiction and has a lively plot, that would be appealing too. Go to your local independent bookstore and look at other, similar books. See who published them. That should give you a list. It's impossible for us to tell you specifically without knowing more about the manuscripts.