Board Thread:Suggestions forum/@comment-2607:FEA8:A2E0:E12:B0E2:C52B:660E:250D-20190109053327/@comment-29620769-20190110085618

Metal does not burn, the coal only melts it, just like lava. Except with coal, it is easier to keep the fuel and metal separated, instead of them mixing.

I think the coal is better option, however, lava should also be possible to use. And maybe durnaur too.