The water content of upper phases was higher than in bio-oils
resulting from the pyrolysis of woody feeds using classical heating,
where it typically did not exceed 30 wt% [2,7]. However water content
of upper phases was close to those reported by Ren et al. [34]
for the microwave pyrolysis of Douglas fir sawdust pellets. The
heat supplied through microwave heating was different than in
the classical process, as reported above, because it caused a different
degradation of cellulose and hemicellulose and promoted different
amount of water formation. High amounts of water could
not be only ascribed to the heating method, because quenching
speed and efficiency of vapors condensation might also influence
the kinetics of secondary reactions involving intermediates formed
in the course of cellulose and hemicellulose pyrolysis [2,3,35].