involving alcohols or weak organic acid seems to be an attractive means as both are
intermediary metabolic processes during biogas formation. Kabir et al. (2015)
pretreated forest residues with ethanol, methanol, or acetic acid prior to anaerobic
digestion and showed higher methane production and also suggested that methanol
can be a cost-effective chemical agent utilized for pretreatment due to its lower cost
and easy recovery after completion of biogas production process.
4.5.2 Use of Microbial Consortia
The conversion of all the biowaste hydrolysis products such as pentoses, hexoses,
volatile products, and soluble lignin to methane is practical using a mixture of
microbes and a very good way to improve anaerobic digestion process (Fox et al.
2003). The quantities of the microbial groups during each step of biogas production
affect the rate of the whole reaction (Griffin et al. 1998). Among all the groups of
microorganisms involved in biogas production process, methanogens are very
sensitive to fluctuations in environmental conditions, temperature, pH, redox potential, and inhibitors and hence are considered to be a rate-limiting factor in biogas
production process (Chen et al. 2008). One obvious strategy proposed by researchers
working in the field of biogas process improvement is genetic modification of
microorganisms involved in the process of biogas formation so as to get higher
metabolic efficiency which ultimately leads to production of energy-rich biofuels
(Xu and Koffas 2010). Besides, substitute strategies suggest the blocking of undesired metabolic pathways to divert energy flow toward target-based metabolism of
microorganisms present in anaerobic digestion system (Weng et al. 2008).
4.5.3 Additives
Biogas yield can be enhanced by accelerating microbial activities in the biogas
digester plant. Generally additives are used as nutrients for microbes, and proper
monitoring of its concentration is needed (Chen et al. 2008; Demirel and Scherer
2011). Incorporation of additive calcium salts and magnesium improved methane
production and reduced foaming of slurry (Yadvika et al. 2004). Moreover,
incorporation of additives for stabilization of pH and reducing concentration of
hydrogen sulfide and ammonia are also recommended (Kuttner et al. 2015). Enrichment of crop residues like water hyacinth, wheat straw, onion storage waste, maize
stalks, rice straw, cotton stalks, etc. with moderately digested cattle manure
enhanced gas production to the tune of 10–80%. Additives like zeolite enhance
biogas production by 15%, and calcium carbonate improved output by 8%. Iron salts
such as iron chloride decrease hydrogen sulfide concentration in biogas with no side
effects when added at the rate of 0.03 and 0.06 g l
À1 (Kuttner et al. 2015).
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G. Monika et al.
intermediary metabolic processes during biogas formation. Kabir et al. (2015)
pretreated forest residues with ethanol, methanol, or acetic acid prior to anaerobic
digestion and showed higher methane production and also suggested that methanol
can be a cost-effective chemical agent utilized for pretreatment due to its lower cost
and easy recovery after completion of biogas production process.
4.5.2 Use of Microbial Consortia
The conversion of all the biowaste hydrolysis products such as pentoses, hexoses,
volatile products, and soluble lignin to methane is practical using a mixture of
microbes and a very good way to improve anaerobic digestion process (Fox et al.
2003). The quantities of the microbial groups during each step of biogas production
affect the rate of the whole reaction (Griffin et al. 1998). Among all the groups of
microorganisms involved in biogas production process, methanogens are very
sensitive to fluctuations in environmental conditions, temperature, pH, redox potential, and inhibitors and hence are considered to be a rate-limiting factor in biogas
production process (Chen et al. 2008). One obvious strategy proposed by researchers
working in the field of biogas process improvement is genetic modification of
microorganisms involved in the process of biogas formation so as to get higher
metabolic efficiency which ultimately leads to production of energy-rich biofuels
(Xu and Koffas 2010). Besides, substitute strategies suggest the blocking of undesired metabolic pathways to divert energy flow toward target-based metabolism of
microorganisms present in anaerobic digestion system (Weng et al. 2008).
4.5.3 Additives
Biogas yield can be enhanced by accelerating microbial activities in the biogas
digester plant. Generally additives are used as nutrients for microbes, and proper
monitoring of its concentration is needed (Chen et al. 2008; Demirel and Scherer
2011). Incorporation of additive calcium salts and magnesium improved methane
production and reduced foaming of slurry (Yadvika et al. 2004). Moreover,
incorporation of additives for stabilization of pH and reducing concentration of
hydrogen sulfide and ammonia are also recommended (Kuttner et al. 2015). Enrichment of crop residues like water hyacinth, wheat straw, onion storage waste, maize
stalks, rice straw, cotton stalks, etc. with moderately digested cattle manure
enhanced gas production to the tune of 10–80%. Additives like zeolite enhance
biogas production by 15%, and calcium carbonate improved output by 8%. Iron salts
such as iron chloride decrease hydrogen sulfide concentration in biogas with no side
effects when added at the rate of 0.03 and 0.06 g l
À1 (Kuttner et al. 2015).
114
G. Monika et al.