Funnily enough, I've recently been looking at this conversion (I'm outside Boston, using natl. gas). One hugh advantage of coal is you can
stockpile it very easily and safely: it doesn't rot, is waterproof and cheaper by the truckload.
Worth considering in anticipation of any upcoming BTU tax on the stuff eh?
Avoid stockpiles of uncompacted coal that catches rain and sun. There's nothing worse than trying to find a hot spot in a coal pile, which can happen spontaneously.