I do not have direct experience, but many years of observing physical, thermal effects on many materials, I offer the following.
Kiln dried sawdust will give a "mild" drying effect.
Cement kiln dust will give a "large" drying effect.
Many tables show cellulose vs. equilibrium data. Books have been written on the subject. Do a literature search. Not so many tables for kiln dust, but the Portland Cement Institute maintains good library information on such data. It's worth a look.