and generally less amount of bioenergy is required than aerobic digestion processes.
Upflow anaerobic sludge blanket (UASB) reactor is cast off mainly in the anaerobic
wastewater treatment process. In this process, there are two openings. The upper one
is used to discharge the cleaned water, and the lower one is used to send the raw
wastewater into the reactor. A sludge blanket is formed inside the reactor which is
acting as a filter again for the treatment of upcoming wastewater, which is then
discharged or removed from the reactor. In this blanket, the methanogens are
converting organic materials into the stable product in the form of biogas (Sarkar
and Banerjee 2013).
Agricultural wastes are the main biologically degradable waste to get biogas in
the form of methane as well as carbon dioxide. It also consists of poultry, pig, and
cattle waste as well as slurry and manure coming from animals. The anaerobic
digestion of these types of waste not only decreases the pollution load as well as
generates biogas in the form of methane, but it decreases the concentration of
pathogen and smell and enhances the quality of the manure used as a fertilizer
(Sahlström 2003). It is observed that in many agricultural fields like those of maize
silage as well as sugar beet, simultaneously the biogas plant can also run (Demirel
and Scherer 2008; Lebuhn et al. 2008).
Among the available technologies, anaerobic digestion presents a number of
relevant advantages. Firstly, this process reduces the chemical oxygen demand
(COD) of the waste to produce valuable energy (methane). Secondly, it has been
experimentally demonstrated that this process is particularly well adapted for concentrated wastes such as agricultural (e.g., plant residues, animal wastes, etc.) and
food industry wastewater. In addition, it is able to operate under severe conditions,
i.e., high-strength effluents as well as short hydraulic retention times. Finally,
anaerobic digestion is also often used as sludge treatment for the stabilization of
primary as well as secondary sludge. Only a few research works have been reported
for the production of methane-rich biogas using industrial wastes (Banerjee and
Biswas 2004).
Several methanogenic strains have also been shown to produce hydrogen
(Valentine et al. 2000; Gieg et al. 2008). This can happen when the amount of
hydrogen is very low (around below nano-molar), so that methanogenic bacteria is
about to start producing metabolic hydrogen instead of taking in hydrogen. It has
been proven that formate and possibly other metabolites, not methane, may be the
source of H 2 . It is not seen in the case of reverse methanogenesis (Valentine et al.
2000; Lupa et al. 2008).
In current decades, tools for the production of genetically modified methanogen
have been developed, which leads to open a novel arena of research. At the initial
stage, the production of methanogenic microbes can be improved. As an example,
modification of the strain M. maripaludis to create geraniol is possible in place of
biogas from the formate or carbon dioxide and hydrogen (Liu et al. 2016).
About 70% of the petroleum is well stored in the field if natural extraction
procedure is implemented. The residual oil present in the oil field is converted in
the form of biogas by the concerted action of the methanogenic bacteria. The used
strain is generated from the sediment of the intermediate layer, and maybe a high
72
S. Sivamani et al.
Upflow anaerobic sludge blanket (UASB) reactor is cast off mainly in the anaerobic
wastewater treatment process. In this process, there are two openings. The upper one
is used to discharge the cleaned water, and the lower one is used to send the raw
wastewater into the reactor. A sludge blanket is formed inside the reactor which is
acting as a filter again for the treatment of upcoming wastewater, which is then
discharged or removed from the reactor. In this blanket, the methanogens are
converting organic materials into the stable product in the form of biogas (Sarkar
and Banerjee 2013).
Agricultural wastes are the main biologically degradable waste to get biogas in
the form of methane as well as carbon dioxide. It also consists of poultry, pig, and
cattle waste as well as slurry and manure coming from animals. The anaerobic
digestion of these types of waste not only decreases the pollution load as well as
generates biogas in the form of methane, but it decreases the concentration of
pathogen and smell and enhances the quality of the manure used as a fertilizer
(Sahlström 2003). It is observed that in many agricultural fields like those of maize
silage as well as sugar beet, simultaneously the biogas plant can also run (Demirel
and Scherer 2008; Lebuhn et al. 2008).
Among the available technologies, anaerobic digestion presents a number of
relevant advantages. Firstly, this process reduces the chemical oxygen demand
(COD) of the waste to produce valuable energy (methane). Secondly, it has been
experimentally demonstrated that this process is particularly well adapted for concentrated wastes such as agricultural (e.g., plant residues, animal wastes, etc.) and
food industry wastewater. In addition, it is able to operate under severe conditions,
i.e., high-strength effluents as well as short hydraulic retention times. Finally,
anaerobic digestion is also often used as sludge treatment for the stabilization of
primary as well as secondary sludge. Only a few research works have been reported
for the production of methane-rich biogas using industrial wastes (Banerjee and
Biswas 2004).
Several methanogenic strains have also been shown to produce hydrogen
(Valentine et al. 2000; Gieg et al. 2008). This can happen when the amount of
hydrogen is very low (around below nano-molar), so that methanogenic bacteria is
about to start producing metabolic hydrogen instead of taking in hydrogen. It has
been proven that formate and possibly other metabolites, not methane, may be the
source of H 2 . It is not seen in the case of reverse methanogenesis (Valentine et al.
2000; Lupa et al. 2008).
In current decades, tools for the production of genetically modified methanogen
have been developed, which leads to open a novel arena of research. At the initial
stage, the production of methanogenic microbes can be improved. As an example,
modification of the strain M. maripaludis to create geraniol is possible in place of
biogas from the formate or carbon dioxide and hydrogen (Liu et al. 2016).
About 70% of the petroleum is well stored in the field if natural extraction
procedure is implemented. The residual oil present in the oil field is converted in
the form of biogas by the concerted action of the methanogenic bacteria. The used
strain is generated from the sediment of the intermediate layer, and maybe a high
72
S. Sivamani et al.