3.4. Water absorption
When biomass absorbs water, free water becomes bound water,
reducing the volume available for water flow. Biomass behaves
similarly to a sponge, absorbing and holding many times its weight
in water. Fig. 4 illustrates the sponge like behavior of bagasse, poplar
and switchgrass with and without particle size reduction as
well as after pretreatment. Bagasse with no particle size reduction
absorbed 10.7 times its weight in water, the most of all substrates
studied. Poplar chips absorbed 2.5 times its weight in water, the
least of all substrate studied. Keeping in mind that free water in
the reactor is necessary for flow, the absorption behavior determines
how much biomass can be loaded in the FT reactor. Therefore,
a bagasse FT reactor requires a much lower solids