Specific methanogenic activity (SMA) can be defined as the maximum methane production capacity of a consortium of anaerobic microorganisms, carried out under controlled laboratory conditions, in order to enable the maximum biochemical activity of organic substrate conversion.

The activity is calculated from the direct measurement of the methane production rate or substrate consumption, per unit of biomass (VSS), and per unit of time. The concentration of volatile suspended solids must be considered, as well as the use of equipment capable of monitoring changes in metabolic activity or the consumption of the test substrate during the analysis period.

Knowledge of this parameter makes it possible to establish the maximum COD removal capacity in the liquid phase, allowing for the estimation of the maximum organic load that can be applied while minimizing the risk of imbalance in the anaerobic process.

Methane-producing archaea, or methanogens, are recognized for their ability to obtain energy for growth through methanogenesis. Methanogenic archaea are specialized in methane production, with no species known to grow independently of it. They display a wide morphological variety but are generally prokaryotic cells with chemically diverse cell walls.

There are two groups involved in methanogenesis: microorganisms that generate methane from acetic acid or methanol (acetoclastic) and those that produce methane from hydrogen and carbon dioxide (hydrogenotrophic).

Similar to Methanosarcina sp..

Similar to Methanospirillum sp..

Since biogas production is carried out by bacteria, factors that affect their survival will directly impact methane formation. Among the controlled factors are:

· Air tightness: methanogenic bacteria are strictly anaerobic; therefore, the reactor must be perfectly sealed;

· Temperature: the rates of biochemical reactions are directly affected by temperature—higher temperatures increase biogas production;

· Alkalinity and pH: reactor instability is generated by an increase in volatile acid concentration;

· Nutrients: the main nutrients for microbial populations are nitrogen, sulfur, phosphorus, iron, cobalt, nickel, molybdenum, among others.

SMA analysis can be used as a monitoring parameter of the efficiency of the methanogenic population present in the biological reactor, becoming a tool for operational control, as well as for adopting more rational procedures for sludge disposal in anaerobic systems.