According to a study conducted at San Jose State University, the release of heavy metals into the environment by retail photo processing labs declined by 73% between 1996 and 2006. This is an obvious result of the decline of film and the ascension of digital photography.
My current process is digital up to the final step where I outsource to a hybrid digital/silver pro lab. I've often wondered about the environmental impact of continuing to use a silver-based printing process. Though it's impossible to get precise information from the labs regarding their disposal procedures, it's clear that those chemicals eventually end up somewhere, most likely in our rivers.
With that thought in mind, I've been considering going to an in-house pigment-based printing process; in other words, I'm thinking about purchasing a pro quality inkjet printer. If I do so, my process will be 100% digital from start to finish, and I'll have control over the waste products (at least until they go to the recycler).
The other factor is that black & white inkjet has finally fully come of age with the advent of Jon Cone's Piezography ink sets. Piezography's varying shades of gray ink are formulated specifically to replace the color inks in an inkjet printer. The result is a dedicated black & white printer capable of producing exceptionally subtle tones and gradients. Using these inks, black & white inkjet prints have the potential to surpass even the best traditional darkroom silver prints.