How dry do you want it ? What is the destination of dry bulk material.
Thermcools' statement on rough approximation is correct - except I don't understand what He means by "heat absorbed by bulk biomass" and "loss to the ambient".
While as a unit operation Themcool is correct on rough approximation as a single step process. However a more complex precess arrangement would enable you to achive pretty low moisture levels for less than 100 btus / lb of water removed.
Much more detail required to determine suitability of such.
Regards,