now sawdust burning is a very interesting topic, ive a friend who is building a sawdust burning 'engine' to run his bedford RL (green godess) all i know so far is, that you need a stainless steel grid with air holes in it, in the bottom, to keep it going. i believe dick strawbridge built one and ran a car on it. it works by generating combustible fumes. this is from memory and may not be entirely accurate!!
i too have piles of the stuff. i hate wasting anything and need to find a use other than longterm compost for it.
earlier in the year during the phytoptera clearance i got my hands on half a dozen winched out oak and rhody rootballs, im saving them for properly cold weather, i suspect this winter will be as harsh as the one 2 years ago.