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Principles of fermentation biology

The formation of biogas is a complex fermentation process involving various micro-organisms, which require a stable process environment. In practice, various factors can unbalance the fermentation biology and in doing so inhibit biogas production.

The production of biogas - a complex process

Biogas is produced in four phases

Biogas is the end-product in an anaerobic breakdown process. This process can basically be split into four phases. Different micro-organisms and different enzymes are involved in each of its process stages, and these work together in close proximity to form a type of symbiosis.
Biogas is produced in four phases:
In the first step, the hydrolysis phase, the carbohydrates are broken down to simple sugars, the proteins to amino acids and the fats to fatty acids. The products of hydrolysis are broken down further in the subsequent acid formation phase (acidogenesis), predominantly to organic acids and lower alcohols. The acetic acid formation phase (acetogenesis) represents the link to methane formation. Here, the products for acid formation are converted to acetic acid, carbon dioxide and hydrogen, which are ultimately the starting products for methane formation (methanogenesis). In a healthy process, all these steps run simultaneously.

Optimum nutrient supply allows a smooth process

Stable process conditions must be created for all these process steps to run smoothly. The supply of the nutrients and trace elements to the involved micro-organisms plays a decisive role in this.
Trace elements are, in addition to their function in the formation of the cell structures, required primarily as components of the enzymes and co-enzymes, which in turn are responsible in many ways for the catalysis of the individual reaction steps of the processes described above. Alone, seven enzymes and three co-enzymes are involved in the breakdown steps for the formation of methane from CO2 and H2.

Not too many and not too few - the nutrient ratio is decisive

Liebig’s barrel

The “Law of the minimum” according to Liebig applies to the fermentation process. It states that if one nutrient is limiting, full yields cannot be achieved. However, excess availability of minerals can also have a toxic effect on the micro-organisms.

As the limits of optimum supply and toxic effect lie very close together for some elements, a precise analysis and dosage of the trace elements is of huge importance in the methane production process. Furthermore, from the point of view of ground protection, excessive concentrations of micro- and macronutrients should be avoided in principle, to prevent unnecessary environmental impacts.



Fermentation additives

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