It matters what kind of stems your using. Bud stem has a THC level similar to the bud on it. You can make make some nice edibles and extracts with bud stem.
Branches and stalk aren't worth it,IMO,unless you have the time and patience to process them.
Leaf stem from the buds are close to bud stem itself in potency,well worth working with.
There was a guy posting a guide to quick and easy way to make firecrackers in the microwave on this board a few days back. Use about a joint's worth of ground bud stem to make one and see what happens? A couple hours after downing it you should have an idea if the stem you have is worth fooling with.
Heck,I might do just that when I get home tomorrow with some stem? It can't hurt me,and the doc say's I need more fiber in my diet.