Energy Unlimited Inc has been manufacturing and installing sawdust burners for over 15 years. We have supplied sawdust burners for rotary drum dryers drying many products including, alfalfa, wood shavings, sawdust for wood pellets and plastic lumber, shrimp heads, bakery waste and PVC resin. We can attach our sawdust burner to your existing dryer and gas burner without removing the gas burner if the need to reuse it ever arises.  With most of our burners paying for themselves in less than a year, the choice to switch off of natural gas is obvious .  There are many burners on the market that look similar to ours but upon close inspection one would realize the differences.  Note the placement of the combustion blowers.  We place ours away from the burner . The design on the right will burn these motors up in about a years time.  Note that we use less motors. Why buy three fans including starters, extra wiring, more installation time etc, when one is all you need. Of course you would need two on our larger burners but others would sell you five or six fans on a compatible size burner.  We use all 12 gauge minimum steel in the construction of our sawdust burners. With some of that being stainless steel in key ares to prolong burner skin life.  Another thing to look at is the door. A properly designed door will not have huge gaps with fire blanket stuffed in it. It should be self sealing and prevent sparks and ash from leaking out.  Stronger refractory in the ductwork and the option of precast octagon sawdust burners are also things offered only by Energy Unlimited Inc.