Outdoor Coal Boiler?

I was talking to a friend the other day about the horrendous price of oil and gas. Naturally, I smiled smugly and told her that I heat with coal. She said that her husband wants to put in an outdoor wood-fired boiler. I'm pushing her towards coal (don't know why, the more demand, the higher the cost per ton) but I could not find any outdoor coal boilers in my searches.

Does anyone use an outdoor coal boiler that they bought off-the-shelf, so to speak? Or would they need to build a shed/barn and install there? I see a lot of outdoor wood boilers around here, but not coal.

Some of the outdoor Wood ones can use coal, but have to have a few mods to them to burn coal, but probably not efficiently.
Coal burning is different than wood and has to be setup to burn coal, either shaker grates, stoker mechanisms, combustion blower from underneath, etc...

here is one I found.

http://www.heatinnovations.com/coalheat.htm

They claim to have an outdoor coal boiler.
http://www.taylorstove.net/TaylorCoalstove.htm

I have two friends that burn coal in their outdoor furnaces. They are both designed to burn coal. One is a Mahoning OWB and the other is a Freedom OWB which is just about an exact copy of the Mahoning. We live in Bituminous coal country and that is what we all burn around here. They claim they work well.

I am skeptical of the longevity of these outdoor boilers. I have yet to see an old one. Atleast an old one that hasn't been welded a few times...