Chris and Thomas : I did a quick search to hoping to find pictures of the smaller sizes of coal,
pea coal, chestnut, and buckwheat i remembered from my childhood!
These types were supposed to be stored in a hopper the size to the medium sized chest freezer, and the coal was delivered to the coal furnace via auger, for heat
protection the coal in the auger had to be used up or there was liable to be a fire outside of the Furnace, lots of asbestos was used as part of heat shields that needed
to be replaced every so often, the home owner was expected to be able to get out of bed in the middle of the night to find and fix his problems himself, which kinda
negated the whole point of the auger system !
Anyway here is a website where they talk about burning coal, scroll down and check out the coal sizes, The periodic job of cleaning the grates, and hauling ashes is
the hard part to automate, otherwise you
should be able to use the smaller sizes where you could use wood pellets
http://nepacrossroads.com/about14181-60.html
For the Good of the crafts ! Big Al