Identification of methanogenic pathways in anaerobic digesters using stable carbon isotopes

• Published in: Engineering in life sciences Vol. 10; no. 6; pp. 509 - 514
• Main Authors: Laukenmann, Stephan, Polag, Daniela, Heuwinkel, Hauke, Greule, Markus, Gronauer, Andreas, Lelieveld, Jos, Keppler, Frank
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.12.2010; WILEY‐VCH Verlag
• Subjects: Anaerobic digestion; Biogas; Methane; Stable isotopes; Zea mays
• ISSN: 1618-0240; 1618-2863; 1618-2863
• DOI: 10.1002/elsc.201000074

In a series of anaerobic batch experiments, the stable carbon isotopes, δ13CCH?4? and δ13CCO?2?, were measured in biogas produced from various sources (maize, cellulose, inoculum) to identify the degradation kinetics and specific methanogenic pathways. Isotopic analysis was performed using a new absorption laser spectrometer in addition to conventional MS. A comparison of the isotopic evolution shows large isotope dynamics for maize and cellulose, indicating a temporal change in degradation pathways and/or a change in the relative contribution from different carbon fractions within the substrate. Further batch experiments with isotopically labelled acetate (either 13CH3CO2Na or CH 313CO2Na) were carried out to study the degradation of acetate in inoculum systematically. The results suggest that the acetate is completely oxidized into CO2 which in turn is partly reduced to CH4. Furthermore, the distinct isotopic signature CH4 and CO2 (for acetate‐methyl labelling as well as for acetate‐carboxy labelling) indicate that only a minor part of the produced methane derives from acetate. A substantial fraction of methane may have been produced at an earlier stage of the reaction chain or by other potential methane precursors such as formate or methanol.