Environmental Engineering Reference
In-Depth Information
Table 6.7. Methods for pre-treatment of lignocellulosic wastes for ethanol production.
Method
Characteristics
Performance
Comments
References
Steam
High temperature,
Cost-effective
Mosier
et al.
(2005)
explosion
high pressure steam
for hard wood
Silverstein (2004)
Less effective
for soft wood
Ammonia
Prewetting with
Less effective
Recovery of
McMillan (1997)
fiber/freeze
NH
3
followed by
for wastes with
NH
3
possible
Silverstein (2004)
explosion
pressurization
high ligning
(
>
12 bar)
content
Acid
Several types of
Dilute acid
Brink (1993)
pre-treatment
acids possible,
mostly used
Chung
et al.
(2005)
sulfuric acid,
Re-precipitation
Dale and Moelhman
hydrochloric acid,
of lignin need to
(2000)
peracetic acid,
be prevented
Hussein
et al.
(2001)
nitric acid,
Karimi
et al.
(2006)
phosoric acid
Knauf and Moniruzzaman
Continues (loading
(2004) Kurakake
et al.
5-10 mass-%
+
(2005)
>
160
◦
C) or batch
McMillan (1997) Tucker
(loading 10-40
(2003)
mass-%
+
<
160
◦
C)
Teixeira
et al.
(1999)
Wyman (1999)
Alkaline
Ambient
Production of
Börjesson (2006)
pre-treatment
temperature, low
irrecoverable
McMillan (1997)
pressure, dilute
salts
NaOH
Easy removal of
lignin content
Biological
Special
Simple process
Wyman (1999)
pre-treatment
microorganisms
Long reaction
time
Expensive
microorganisms
For the substrates that are not directly fermentable, substrate pre-treatment for conversion
into sugar monomers are necessary. Possible pre-treatment methods for ethanol production from
lignocellulosic material are presented in Table 6.7.
Agriculture waste and food industry wastewater can also be fermented to butanol. The process
is similar to the production of ethanol but with other microorganisms. Butanol can be used as
stand-alone transportation fuel or blended with petrol or diesel. Examples of wastes that have been
tested for butanol production are corn stover, switch grass, straw, and whey (Kumar and Gayen,
2011; Qureshi
et al.
, 2010; Napoli
et al.
, 2010; Wang and Chen, 2011). There are still questions
to be solved to reach high yields of butanol and high production rates. The process has yet not
been widely demonstrated in scaled up plants or showed clear economic feasibility. However,
remarkable development efforts are directed to this field of improved “real” biotechnologies
utilizing the biocatalysis. For example, the problem of some compounds that are formed during
the degradation of lignocelluloses inhibiting the butanol producing microorganisms, could be
avoided by pretreatment.
The cost of butanol downstream processing is very sensitive to butanol concentration in the
broth (Zhu and Yang, 2010). In order to increase the concentration in the production broth, in
turn, it is crucial to increase the cell concentration of the production organism. This goal could be
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