Environmental Engineering Reference
In-Depth Information
Table 3.1
Summary of process conditions, major effects, advantages and disadvantages of biomass pretreatment methods.
Pretreatment methods
Major process conditions
Major effects
Advantages
Disadvantages
Mechanical processes
Chipping, grinding, and
milling
Final particle size of the
material (10-30 mm after
chipping and 0.2-2 mm
after milling or grinding)
Reduction of particle size and
the crystallinity of lignocellulosic
materials
Control of the final particle
size
High energy
requirements
Densification
(pelletization)
High pressure
Reduction of particle size;
conversion of biomass into
high-density solid energy carriers
Increased biomass energy
value
Limited choice
of raw materials
Physical processes
ScCO
2
and natural
solvent
Pressure and temperature
above the critical point of
the compounds
Extraction of bio-oil and
extractives
Specific compounds
extraction; low
environmental impact; no
remaining solvent residues
High energy
requirements
AFEX
Treated with liquid
anhydrous ammonia;
temperature: 60-100°C;
pressure: 250-300 psi
Lignin solubilization;
hemicellulose hydrolysis;
cellulose decrystallization;
increased surface area
No wash stream; no need
for neutralization; free of
contaminants
High energy
requirements
Sub- and supercritical
water treatment
Temperature: near or above
374°C;
pressure: near or above
218 atm
N/A
Allow high concentrations
of reactants; free of
biologically active organism
or compounds; high
solubility of various organic
compounds and gases
High energy
requirements;
corrosive; high
operating costs
(
Continued
)
