carbon dioxide and methane in the molar ratio of 1:2, is a gaseous fuel cast-off for
transportation as well as combined heat as well as power (CHP) generation (Emerson
2008). Biogas can be also used as a precursor to produce valuable biochemicals. It is
manufactured through a sequence of different chemical reactions collectively called
as anaerobic digestion (Sivamani et al. 2018). Anaerobic digestion converts substrate
to biogas as well as digestate, which can be used as a replacement for chemical
fertilizers, that enhances the sustainability of environment, energy security, as well
as social economy (Ganguly et al. 2006). Figure 3.1 shows the detailed flowchart for
biogas production process.
Anaerobic digestion is a complicated method that requires strong basic knowledge on biochemistry, microbiology, and process engineering (Ali Shah et al. 2014).
It involves a group of microbes such as hydrolytic, acidogenic, acetogenic, as well as
methanogenic organisms with different growth requirements as well as metabolic
capacities. The nutritional requirements of each group of microbe should be complete for their growth as well as efficient biogas production (Schnürer 2016). The
factors affecting biogas production are characteristics of substrate (especially C/N
ratio and VSS/TSS ratio), concentration of substrate in feed, process temperature,
retention time, working pressure, as well as pH of feed. Substrate characteristics are
one of the essential parameters in biogas production because its nutrients provide
sufficient growth factors (Westerholm and Schnürer 2019). Pure substrates or
co-substrates which are selected for biogas production based on C/N as well as
VSS/TSS ratios are used to deliver favorable conditions for microbial growth as well
as biogas generation (Khan 2019). However, additives are essential to support the
metabolic activity of microorganisms as well as avoid process damage.
In addition to the nutritional factors, non-nutritional parameters such as concentration of substrate in feed, process temperature, retention time, working pressure, as
well as pH of feed should be optimized to achieve maximum biogas yield with
minimum inhibition. Thus, numerous aspects are to be considered to obtain sufficient metabolic activity as well as higher gas production (Banerjee and Sirkar 2012).
The process becomes complicated because of the interaction between nutritional and
non-nutritional parameters (van Ommen et al. 2009). Figure 3.2 illustrates the
digestion process (anaerobic) life cycle.
Table 3.1 shows the sequence of steps in anaerobic digestion process. This is a
biochemical as well as microbial process comprising hydrolysis of the complex
nutrient, acidogenesis of the converted biomass, acetogenesis of the remaining
product, as well as methanogenesis. Hydrolysis contains the breakdown of biopolymers to its monomers in the occurrence of water (Thirugnanasambandham
et al. 2014). Acidogenesis involves the formation of volatile acids from the monomers (Karichappan et al. 2014). Acetogenesis produces acetates as well as acetic acid
from various volatile acids (Thirugnanasambandham et al. 2016). Finally, acetates as
well as acetic acid are converted to methane as well as carbon dioxide during
methanogenesis (Sivamani et al. 2020).
Methanogens are a type of biocatalysts which will supply the energy in the form
of methane (Enzmann et al. 2018). There are a diverse group of methanogens which
have a potential ability to supply energy. Methane is considered to be the alternative
54
S. Sivamani et al.
transportation as well as combined heat as well as power (CHP) generation (Emerson
2008). Biogas can be also used as a precursor to produce valuable biochemicals. It is
manufactured through a sequence of different chemical reactions collectively called
as anaerobic digestion (Sivamani et al. 2018). Anaerobic digestion converts substrate
to biogas as well as digestate, which can be used as a replacement for chemical
fertilizers, that enhances the sustainability of environment, energy security, as well
as social economy (Ganguly et al. 2006). Figure 3.1 shows the detailed flowchart for
biogas production process.
Anaerobic digestion is a complicated method that requires strong basic knowledge on biochemistry, microbiology, and process engineering (Ali Shah et al. 2014).
It involves a group of microbes such as hydrolytic, acidogenic, acetogenic, as well as
methanogenic organisms with different growth requirements as well as metabolic
capacities. The nutritional requirements of each group of microbe should be complete for their growth as well as efficient biogas production (Schnürer 2016). The
factors affecting biogas production are characteristics of substrate (especially C/N
ratio and VSS/TSS ratio), concentration of substrate in feed, process temperature,
retention time, working pressure, as well as pH of feed. Substrate characteristics are
one of the essential parameters in biogas production because its nutrients provide
sufficient growth factors (Westerholm and Schnürer 2019). Pure substrates or
co-substrates which are selected for biogas production based on C/N as well as
VSS/TSS ratios are used to deliver favorable conditions for microbial growth as well
as biogas generation (Khan 2019). However, additives are essential to support the
metabolic activity of microorganisms as well as avoid process damage.
In addition to the nutritional factors, non-nutritional parameters such as concentration of substrate in feed, process temperature, retention time, working pressure, as
well as pH of feed should be optimized to achieve maximum biogas yield with
minimum inhibition. Thus, numerous aspects are to be considered to obtain sufficient metabolic activity as well as higher gas production (Banerjee and Sirkar 2012).
The process becomes complicated because of the interaction between nutritional and
non-nutritional parameters (van Ommen et al. 2009). Figure 3.2 illustrates the
digestion process (anaerobic) life cycle.
Table 3.1 shows the sequence of steps in anaerobic digestion process. This is a
biochemical as well as microbial process comprising hydrolysis of the complex
nutrient, acidogenesis of the converted biomass, acetogenesis of the remaining
product, as well as methanogenesis. Hydrolysis contains the breakdown of biopolymers to its monomers in the occurrence of water (Thirugnanasambandham
et al. 2014). Acidogenesis involves the formation of volatile acids from the monomers (Karichappan et al. 2014). Acetogenesis produces acetates as well as acetic acid
from various volatile acids (Thirugnanasambandham et al. 2016). Finally, acetates as
well as acetic acid are converted to methane as well as carbon dioxide during
methanogenesis (Sivamani et al. 2020).
Methanogens are a type of biocatalysts which will supply the energy in the form
of methane (Enzmann et al. 2018). There are a diverse group of methanogens which
have a potential ability to supply energy. Methane is considered to be the alternative
54
S. Sivamani et al.