I hope this is the right place to ask this. I have a traditional wood/coal boiler with shaker grates and forced draft. I mentioned to a coworker that I burn coal sometimes to augment my wood supply and increase the burn time. He suggested burning sawdust or woodchips. I can get either of these free or at little cost. My questions are will they burn up quickly or smolder for a long time? Will they make any usable heat? Will this cause a lot of creosote? My coworker claims he burns hardwood mulch in his wood furnace with no problems but I have known this coworker to lets say stretch the truth a bit. He also claims that he puts sawdust in a five gallon bucket with small holes in the bottom and wets it down. Then he puts another five gallon bucket on top and fills it with stone creating a sort of press. He claims after a couple weeks he can pop the saw dust out and it holds together making what I guess you would call a poor mans bio brick. Is this possible? I can almost believe that the hardwood mulch would burn OK because of the grates and the air moving through but I would think it would burn up quickly. He claims they don't. I'm going to try it next year just to see but i wanted to get the thoughts of the experts.