I have been burning rice coal in my Harman P61 pellet stove since Oct 24 of this year and have had no problems up to this point. I realize this is not what this stove was designed for, nor would I recommend doing this if you had a design other than the P61's, meaning an auger/bottom fed burn pot with a myriad of adjustments for feed,stove temp, and the like. I would also NOT do this if the stove was still under warranty. I have had mine for over 7 years so the "Harman Gold 6 year warranty" has expired,for what it was worth. The stove is in the basement of my 2 story home and keeps the basement nice and toasty and the first floor only marginal. I would think that with more work,like air returns cut into the floor or maybe hooking it up directly to my air handler I could keep the whole house nice, but I have yet to do that after 7 years. If you look at the design of the P61 it is almost identical to their previous coal burner called the 44 magnum which had something like a 44k btu output. I estimate my output accordingly. Also,it depends on your pellet availabilty. I refused to pay $300 a ton for my fuel this year,and none to be had that wasn't already spoken for so I was left with letting sit unused,trying to find a coal stove, or experimenting. I chose the experimenting route. I paid $145 for my first ton of coal ,and will be getting more. I am pleased with my decision. " Your results may vary, no warranty is expressed or implied. Care and feeding is the responsibility of the owner,yadda,yadda,yadda "