To my mind I think that sawdust will be difficult to anaerobically digest.
The natural wood fibre glue (lignin isone of the few substances that
are not
anaerobically digestible. So the sawdust as Kai Hillebrecht stated
might be
better treated with other methods. Straw as a structure material for
instance does not have such high lignin contents and usually is used
for cow
and hog manure.
Kind regards
Jan Kai