Life cycle assessment (LCA) studies of biogas systems from around Europe were
done by some workers, and they reported that (Hijazi et al. 2016) most suitable
substrate for high biogas (methane) production is animal dung and maize.
As compared to other biomass such as cellulose municipal solid wastes, some
workers have compared various microalgae and cyanobacteria for production of
biogas (Mussgnug et al. 2010). It was reported that green algae Chlamydomonas
reinhardtii is more beneficial in terms of biogas methane production as compared to
other microalgae.
In biogas production, mostly carbon is used in the production of methane while
nitrogen left can be used as manure which enriches soil fertility by replacing
chemical fertilizers depending on the kind of solid agrowaste used. Rice straw is
posing huge problems of disposal instantly and its recalcitrant nature makes it
difficult for its conversion to methane. Some workers stressed on changing the
pattern of pretreatment which can get rid of extra silica and can make it a suitable
biomass for conversion for biogas production (Gurung et al. 2013).
5.5
Lignocellulosic Biomass for Biogas Production
Lignocellulosic biomass is present in abundance in the nature, which can be utilized
for conversion to biogas. Various lignocellulosic feedstocks with their cellulose,
hemicellulose, and lignin content have been summarized in Table 5.2 and Fig. 5.1.
5.6
Biogas Production Mechanism
Hydrolysis of biomass is a must for large organic biomass in order to get rid of
recalcitrant structure such as silica and lignin which impregnate cellulosic and
hemicellulosic biomass. Anaerobic bacteria can be used in anaerobic digesters to
access the energy potential of the material, which can be broken down into their
smaller constituent parts. Sugars released in this way are readily used by other
acetogenic and further by methanogenic bacteria. Acetate and hydrogen produced
in the first stages can be used directly by methanogens.
The third stage of anaerobic digestion is acetogenesis where microbial acetogens
are added to produce largely acetic acid as well as carbon dioxide and hydrogen. The
terminal stage of anaerobic digestion is the methanogenesis. Here methanogens
utilize the intermediate products of the preceding stages and convert them into
methane, carbon dioxide, and water. It is these components that makes up the
majority of the biogas emitted from the system. Methanogenesis is sensitive to
both high and low pH and occurs between pH 6.5 and pH 8. The remaining,
nondigestible material which the microbes cannot feed upon, along with any dead
bacterial remains, constitutes the digestate.
5 Biogas: An Effective and Common Energy Tool – Part III
127
done by some workers, and they reported that (Hijazi et al. 2016) most suitable
substrate for high biogas (methane) production is animal dung and maize.
As compared to other biomass such as cellulose municipal solid wastes, some
workers have compared various microalgae and cyanobacteria for production of
biogas (Mussgnug et al. 2010). It was reported that green algae Chlamydomonas
reinhardtii is more beneficial in terms of biogas methane production as compared to
other microalgae.
In biogas production, mostly carbon is used in the production of methane while
nitrogen left can be used as manure which enriches soil fertility by replacing
chemical fertilizers depending on the kind of solid agrowaste used. Rice straw is
posing huge problems of disposal instantly and its recalcitrant nature makes it
difficult for its conversion to methane. Some workers stressed on changing the
pattern of pretreatment which can get rid of extra silica and can make it a suitable
biomass for conversion for biogas production (Gurung et al. 2013).
5.5
Lignocellulosic Biomass for Biogas Production
Lignocellulosic biomass is present in abundance in the nature, which can be utilized
for conversion to biogas. Various lignocellulosic feedstocks with their cellulose,
hemicellulose, and lignin content have been summarized in Table 5.2 and Fig. 5.1.
5.6
Biogas Production Mechanism
Hydrolysis of biomass is a must for large organic biomass in order to get rid of
recalcitrant structure such as silica and lignin which impregnate cellulosic and
hemicellulosic biomass. Anaerobic bacteria can be used in anaerobic digesters to
access the energy potential of the material, which can be broken down into their
smaller constituent parts. Sugars released in this way are readily used by other
acetogenic and further by methanogenic bacteria. Acetate and hydrogen produced
in the first stages can be used directly by methanogens.
The third stage of anaerobic digestion is acetogenesis where microbial acetogens
are added to produce largely acetic acid as well as carbon dioxide and hydrogen. The
terminal stage of anaerobic digestion is the methanogenesis. Here methanogens
utilize the intermediate products of the preceding stages and convert them into
methane, carbon dioxide, and water. It is these components that makes up the
majority of the biogas emitted from the system. Methanogenesis is sensitive to
both high and low pH and occurs between pH 6.5 and pH 8. The remaining,
nondigestible material which the microbes cannot feed upon, along with any dead
bacterial remains, constitutes the digestate.
5 Biogas: An Effective and Common Energy Tool – Part III
127