I just started doing some background research on green, whole tree chip boilers. The concept would be to use one for multi-building district heating in a fairly large institutional setting. Pluses immediately are on-site forest land that will supply the chips and therefore minimal transportation cost. First, does anyone have experience with these, particularly in a cold climate like northern Minnesota? Second, these are some of the issues I have identified, and how are these dealt with, do they cause problems? Third, are there other issues that need to be examined? 1) The chips consist of fines, bark, needles/leaves, twigs, and branches, as well as solid and decayed wood from the bole of the tree, and on-site dirt and debris, and as such they contain a much higher percentage of incombustible material. What is the impact on ash production, what effect on need and frequency to clean the boiler, do they produce clinkers that cause operational problems? 2) The chips are wet (45-65% moisture). Does this cause more labor, operational, and maintenance costs for the boiler than dry chip boilers? 3) Do wet chips in storage have spontaneous combustion issues? 4) How susceptible are wet chips to freezing into clumps and blocks, or solid masses, resulting in operational problems or failure of the loading mechanism to fuel the boiler? The area climate typically not only is well below freezing, but frequently well below 0F for substantial periods of time. 5) Do wet chips result in higher emissions than dry chips? 6) Can any green chip boilers also burn green chunk wood or stove wood material, such as rounds and splits? Can they burn seasoned chunk or stove wood material (20% MC +/-)? 7) Are any green chip boilers classified as gasification boilers? Thanks for the input.