I cut wood and sell it and buy a little coal with some of the proceeds.
I can't tell you how to make it burn more efficiently, but I can make you feel better. I really only have 2 customers; one guy burns 150 cords of tree length firewood every year (about 1 cord per day), and the other one burns 40 cords tree length. Between those two, I stay pretty busy keeping them in wood. If you burn less than that, feel lucky!
The guy that burns 40 cord, he spent two years cutting his own wood lot figuring when he bought the stove it would use his "free wood". Then after seeing the swath that 80 cords of wood required, he told me he is buying all his wood from now on.
Myself, I am happy to send them truck loads of wood, but my father had one and it burned his house down, and a few more homes around here have burned because of them. My parents and siblings we lucky to escape with their lives as they lived in a split level home and the fire ended up beneath them (in the garage) and over them (in the attic space). My biggest gripe is their 35% burn efficiency. That means for every 100 cords of wood you put into it, you get 35 cords worth of heat out...that does not seem like good math to me.