physical pretreatment (Chandra et al. 2007; Yang and Wyman 2008; Hendriks and
Zeeman 2009; Taherzadeh and Karimi 2008). Milling is proved to be effective by
reducing the degree of polymerization in the specific surface area by shear and
polymerization degree between the physical structures. Thus, hydrolysis yield
improved from 5% to 25% (Jin and Chen 2006; Zeng et al. 2007). These types of
development depend on the type of biomass in addition to the duration and type of
milling (Jin and Chen 2006; Monavari et al. 2009; Lennartsson et al. 2011;
Teghammar et al. 2012). Overall, it has been repeatedly seen that small particles
get more sugar yields. This is the reason that physical exposure is often done in
conjunction with other pretreatment technique. On the other hand, the element
representative intended for pretreatment may perform as a possible blocker for the
microbial community concerned in AD in some cases. It was established that
remaining residues negatively affected the digestive process when forest residues
were mixed with organic solvent, n-methylmorpholine-n-oxide, even in
concentrations up to 0.008% (Kabir et al. 2013). Apart from this, in spite of the
optimization of the pretreatment conditions, a few inhibitors still get produced in the
slurry (Ahring et al. 1996; Hendriks and Zeeman 2009).
It was recently shown that use of alcohol or weak organic acids seems to be an
interesting way to digest lignocelluloses (Kabir et al. 2015).
4.5
Recent Advances in Biogas Production Technology
To overcome the problems associated with poor utilization of lignocellulosic waste
for biogas production and poor methane yield, a number of alteration in the existing
technology have been done like pretreatment of lignocellulosic waste, addition of
substrate, and use of microbial consortia and additive incorporation to accelerate the
biogas production process and enhance gas yield.
4.5.1 Pretreatment
Due to complex structure of lignocellulosic waste, it became less economic feedstock for biogas production process. Pretreatment of lignocellulosic waste is an
attractive option for accelerating anaerobic digestion process and increasing biogas
yield. Pecorini et al. (2016) reported that recalcitrant compounds of municipal waste
can be hydrolyzed by autoclaving and microwave oven treatment. Model biomass
pretreatment decreases crystallinity of the cellulosic structure which makes substrate
easily accessible to microbes and enables them to completely or partially digest
substrate into fermentable sugars. Pretreatment of lignocellulosic waste by milling
increases specific surface area, thereby improving hydrolysis yield by 5–25%. The
degree of such progress depends on the type of biomass and the time and type of
milling (Jin and Chen 2006; Zeng et al. 2007). Many of the chemical agents are
suggested for pretreatment, but in one or other case, they may serve as inhibitors of
microbial community involved in biogas production process. Chemical pretreatment
4 Biogas: An Effective and Common Energy Tool – Part II
113
Zeeman 2009; Taherzadeh and Karimi 2008). Milling is proved to be effective by
reducing the degree of polymerization in the specific surface area by shear and
polymerization degree between the physical structures. Thus, hydrolysis yield
improved from 5% to 25% (Jin and Chen 2006; Zeng et al. 2007). These types of
development depend on the type of biomass in addition to the duration and type of
milling (Jin and Chen 2006; Monavari et al. 2009; Lennartsson et al. 2011;
Teghammar et al. 2012). Overall, it has been repeatedly seen that small particles
get more sugar yields. This is the reason that physical exposure is often done in
conjunction with other pretreatment technique. On the other hand, the element
representative intended for pretreatment may perform as a possible blocker for the
microbial community concerned in AD in some cases. It was established that
remaining residues negatively affected the digestive process when forest residues
were mixed with organic solvent, n-methylmorpholine-n-oxide, even in
concentrations up to 0.008% (Kabir et al. 2013). Apart from this, in spite of the
optimization of the pretreatment conditions, a few inhibitors still get produced in the
slurry (Ahring et al. 1996; Hendriks and Zeeman 2009).
It was recently shown that use of alcohol or weak organic acids seems to be an
interesting way to digest lignocelluloses (Kabir et al. 2015).
4.5
Recent Advances in Biogas Production Technology
To overcome the problems associated with poor utilization of lignocellulosic waste
for biogas production and poor methane yield, a number of alteration in the existing
technology have been done like pretreatment of lignocellulosic waste, addition of
substrate, and use of microbial consortia and additive incorporation to accelerate the
biogas production process and enhance gas yield.
4.5.1 Pretreatment
Due to complex structure of lignocellulosic waste, it became less economic feedstock for biogas production process. Pretreatment of lignocellulosic waste is an
attractive option for accelerating anaerobic digestion process and increasing biogas
yield. Pecorini et al. (2016) reported that recalcitrant compounds of municipal waste
can be hydrolyzed by autoclaving and microwave oven treatment. Model biomass
pretreatment decreases crystallinity of the cellulosic structure which makes substrate
easily accessible to microbes and enables them to completely or partially digest
substrate into fermentable sugars. Pretreatment of lignocellulosic waste by milling
increases specific surface area, thereby improving hydrolysis yield by 5–25%. The
degree of such progress depends on the type of biomass and the time and type of
milling (Jin and Chen 2006; Zeng et al. 2007). Many of the chemical agents are
suggested for pretreatment, but in one or other case, they may serve as inhibitors of
microbial community involved in biogas production process. Chemical pretreatment
4 Biogas: An Effective and Common Energy Tool – Part II
113