optimal conditions, i.e., enzymatic hydrolysis at 45–50
C and fermentation at about
35
C (Cardona and Sanchez 2007; Kurian et al. 2013). Hydrolysis and fermentation
can also be performed through integrated techniques, such as simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation
(SSCF), and consolidated bioprocessing (CBP) (Vohra et al. 2014).
1.4.3.4 Bioethanol Production Through Syngas Fermentation
Syngas conversion using microbial catalysts offers three main advantages:
– It requires significantly lower temperature and pressure conditions (usually atmospheric conditions).
– It is less susceptible to varying feed gas compositions.
– Chemical catalysts are more susceptible to poisoning, compared to microbial
processes (Köpke et al. 2011).
After biomass gasification has been performed, cleaned gas is cooled to the
normal ambient temperature and stored at a high pressure. The gas is then fed into
an ethanol conversion chamber, where microbes ferment it into ethanol and acetic
acid. After fermentation is completed, the liquid is distilled to separate ethanol from
other products. Then ethanol is dehydrated (Dwivedi et al. 2009); see Fig. 1.9.
A large number of bacterial strains have been isolated that have the ability to
ferment producer gas (composed by CO, CO2, and H2) to ethanol, acetic acid, and
other useful liquid products; see, for example, Clostridium ljungdahlii (Henstra et al.
2007), Butyribacterium methylotrophicum, and Clostridium autoethanogenum
(Abubackar et al. 2011).
Fig. 1.8 Lignocellulosic biomass conversion into bioethanol process flow diagram (Vohra et al.
2014)
1 Biofuels: Types and Process Overview
17
C and fermentation at about
35
C (Cardona and Sanchez 2007; Kurian et al. 2013). Hydrolysis and fermentation
can also be performed through integrated techniques, such as simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation
(SSCF), and consolidated bioprocessing (CBP) (Vohra et al. 2014).
1.4.3.4 Bioethanol Production Through Syngas Fermentation
Syngas conversion using microbial catalysts offers three main advantages:
– It requires significantly lower temperature and pressure conditions (usually atmospheric conditions).
– It is less susceptible to varying feed gas compositions.
– Chemical catalysts are more susceptible to poisoning, compared to microbial
processes (Köpke et al. 2011).
After biomass gasification has been performed, cleaned gas is cooled to the
normal ambient temperature and stored at a high pressure. The gas is then fed into
an ethanol conversion chamber, where microbes ferment it into ethanol and acetic
acid. After fermentation is completed, the liquid is distilled to separate ethanol from
other products. Then ethanol is dehydrated (Dwivedi et al. 2009); see Fig. 1.9.
A large number of bacterial strains have been isolated that have the ability to
ferment producer gas (composed by CO, CO2, and H2) to ethanol, acetic acid, and
other useful liquid products; see, for example, Clostridium ljungdahlii (Henstra et al.
2007), Butyribacterium methylotrophicum, and Clostridium autoethanogenum
(Abubackar et al. 2011).
Fig. 1.8 Lignocellulosic biomass conversion into bioethanol process flow diagram (Vohra et al.
2014)
1 Biofuels: Types and Process Overview
17