Who says you need coal to get a little heat, apparently a mixture of hay and sheep manure work as well.
I typically build a compost pile, which is really just hay waste and sheep manure off my HUA, and put it up into a big pile, and then in the Spring go haul it off to my fields for incorporating. It is illegal in Maine to spread manure on your fields from Dec 1st through March 15th, so I clean it up in the Spring.
Today it caught fire.
I am not that concerned about it. With all the snow we have, it will not burn anything, and it is not like it kicks off a lot of embers anyway. Just a lot of smoke and a little heat. Granted it does smell a bit from the manure, but at least this Spring the pile will be a whole lot smaller, and I will have a whole lot less mess to deal with.

The worse one I've been on was a couple Towns over a few yrs back.--He lost the barn & about 100 dairy cows--nothing we could do but keep the old farm house from burning