In case anyone is interested I have been playing around with coffee for a print developer. I kind of blended Gainer's Ascorbic Acid developer with coffee to get pretty good results. Basically it improves the develop rate compared to just using coffee and helps to preserve the solution a bit longer. The end result is pretty good with some warm tones in the greys. Here is an article with more details.

http://www.nspatel.com/article1.php