Most sawmills use their “waste”, or it is sold to manufacturers of things like OSB and particle board, or other composites. Plus with the housing crash, the sawmills aren’t producing as much these days.
Locally, we have small Amish sawmills. They had contracts for years with the state to provide split logs for trails and black locust fence posts. About a year ago, Wisconsin closed a lot of the waysides and curtailed building and maintenance in the parks. Since the cheapest local firewood is slab, there was a lot of worry that the mills would close.
Instead, those capitalistic Amish went out and found other contracts and are still in business.
They burned their sawdust, much to the disgust of the local leftists, who fume about air pollution. Granted, I wouldn’t want to be downwind when they do this. I have heard that instead of burning it, they are selling it for wood pellets.
I was wondering about the bark. About all we do with it now, at the end of the heating season, is chip it for mulch. I just wondered if it could be used in this process. There has been kitty litter made from corn cobs (don’t know how good it is). Again, I wonder if cobs would work in this process.