Evaluation of biogas production in anaerobic digesters

The valorization of organic waste for biogas production through anaerobic digestion is a well-established and widely applied technology for the production of energy from renewable raw materials. One of the most important factors, which significantly influence the viability of such an investment, is the quality of the different feedstocks to the anaerobic digesters, in terms of their biodegradability and the corresponding quantity of biogas produced. Consequently, in order to gain insight into the key design parameters of the anaerobic digestion process, the so-called biogas production potential of the materials intended to be fed to the digesters must be determined. Therefore, in technical and economic feasibility studies, carried out prior to the construction of a biogas plant, the expected energy output is estimated by carrying out biogas production tests.

In addition, in existing installations that accept mixtures of different materials for digestion, the assessment of the biogas production potential for a new substrate is necessary to determine the suitability of the material to be digested and therefore its acceptance in the installation.

In a biogas production evaluation test, a substrate is mixed with a suitable culture of microorganisms (methanogenic bacteria). The mixture is kept in suspension under constant temperature for a period of 20 to 30 days. Key components of the biogas, such as methane (CH₄) and hydrogen sulphide (H₂S) produced during test evolution due to the anaerobic degradation of organic matter, are continuously determined. At the end of the test, the total amount of methane produced is calculated and compared with the typically expected amount, based on qualitative parameters of the influent substrate (COD, TS, VS, etc.).