1.2 Anaerobic Co-digestion (AcD)

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Technical issues could be overcome by reliable public–private partnership,

government initiatives, financial supports followed by technological advancement.

1.1.3

Sustainable Biomethanation

Sewage water treatment plants mandatorily follow AD for sludge treatment, and

the ensuing methane-based gas is used for running wastewater treatment plants

(WWTPs), though this is in principle, but the scenario is that many WWTPs struggle

to maintain sustainable digesters, which are progressively jeopardized by frequent

reactor failures. Biogas plants were ideally found to be an alternate source for renew-

able energy and were operated widely in rural areas of India; however, over the last

few decades, it has taken a back seat, partially attributed to:

●digester operational instability,

●nonhomogeneous substrate,

●lack of good microbial inoculum,

●promotion and easier availability of LPG,

●deeper reach of electricity to remote rural areas,

●dip in active promotion of AD and their significance, especially in rural areas.

Renewed interest in AD stems from the problems of rapid urbanization and urgent

need of waste management. Running successful biogas digesters depends mainly on

two important factors: nature of substrate and the quality of inoculum. Real-time

monitoring emphasizes on the following factors:

●balanced micro- and macronutrients,

●efficient microbial inoculum,

●digester design optimization,

●optimized organic loading rate (OLR),

●efficient monitoring of critical parameters (pH fluctuations, temperature range,

total solids (TSs) utilization rate, volatile solids (VSs) accumulation and dispersal

rates, microbial profiling: that is, eubacterial versus archaeal load ratio),

●continuous evaluation of digester performance [rate of biogas production,

methane percentage, reduction in total solids, reduction in chemical oxygen

demand (COD)],

●Reducing inhibitor concentrations.

1.2

Anaerobic Co-digestion (AcD)

Biogas technology is a perfect example to emphasize on zero waste concept,

conversion of waste into fuel, and even the final digested remnant slurry’s immense

value as organic manure, which is potentially free of pathogens. Mono-digestion

refers to the classical way for biogas production from a single type of feedstock while

a co-digestion refers to mixing of two different feedstocks in a digester for biogas

production. Co-digestion was initially planned to balance a carbon-to-nitrogen