Sten and I are corresponding on the drying of the sawdust and chips he is able then to compact. You can achieve use of those gases' energy for drying only if you have two process chambers operating sequentially, one drying and one pyrolysing. The trouble with using air is that, once the sawdust is dry, if the air is hot enough to pyrolyse it, it will burn it, i.e. the air will immediately ignite the pyrolysis gases as happens in a stove. This is why we are drying wood, etc., in recirculating superheated steam instead of air and, once the volume of pyrolysis gases being generated has displaced and replaced the machine's steam atmosphere, using recirculating pyrolysis gases as the heat and mass transfer medium.
Air is excluded throughout.
During subsequent pyrolysis of the dried material, hot, virtually steam-free pyrolysis gases are vented which can then be burnt easily and their combustion gases' thermal energy used to dry the next load of moist material ready for it in turn to be pyrolysed. What I don't like about this is the reliance on a fan to force the air through the mass of sawdust to be dried. I'd rather be off the grid. Heat is and will be supplied by a wood burning stove. We are also looking into using a Stirling engine heated by our dryer's indirect heater's flue gases to generate the electricity needed to operate the fan, thus eliminanting the need for 12 v batteries.