Determination of methanogenic pathways through carbon isotope (δ13C) analysis for the two-stage anaerobic digestion of high-solids substrates.
This study used carbon isotope (δ(13)C)-based calculations to quantify the specific methanogenic pathways in a two-stage experimental biogas plant composed of three thermophilic leach bed reactors (51-56 °C) followed by a mesophilic (36.5 °C) anaerobic filter. Despite the continuous dominance of the acetoclastic Methanosaeta in the anaerobic filter, the methane (CH4) fraction derived from carbon dioxide reduction (CO2), fmc, varied significantly over the investigation period of 200 days. At organic loading rates (OLRs) below 6.0 gCOD L(-1) d(-1), the average fmc value was 33%, whereas at higher OLRs, with a maximum level of 17.0 gCOD L(-1) d(-1), the fmc values reached 47%. The experiments allowed for a clear differentiation of the isotope fractionation related to the formation and consumption of acetate in both stages of the plant. Our data indicate constant carbon isotope fractionation for acetate formation at different OLRs within the thermophilic leach bed reactors as well as a negligible contribution of homoacetogenesis. These results present the first quantification of methanogenic pathway (fmc values) dynamics for a continually operated mesophilic bioreactor and highlight the enormous potential of δ(13)C analysis for a more comprehensive understanding of the anaerobic degradation processes in CH4-producing biogas plants.
†Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstrasse 150, Bochum 44801, Germany.
Tito
T
Gehring
‡Leibniz Institute for Agricultural Engineering Potsdam-Bornim (ATB), Max-Eyth-Allee 100, Potsdam 14469, Germany.
Johanna
J
Klang
§Institute of Geology, Mineralogy and Geophysics, Ruhr-Universität Bochum, Universitätsstrasse 150, Bochum 44801, Germany.
Andrea
A
Niedermayr
†Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstrasse 150, Bochum 44801, Germany.
Stephan
S
Berzio
§Institute of Geology, Mineralogy and Geophysics, Ruhr-Universität Bochum, Universitätsstrasse 150, Bochum 44801, Germany.
Adrian
A
Immenhauser
‡Leibniz Institute for Agricultural Engineering Potsdam-Bornim (ATB), Max-Eyth-Allee 100, Potsdam 14469, Germany.
Michael
M
Klocke
†Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstrasse 150, Bochum 44801, Germany.
Marc
M
Wichern
†Institute of Urban Water Management and Environmental Engineering, Ruhr-Universität Bochum, Universitätsstrasse 150, Bochum 44801, Germany.
Manfred
M
Lübken
D000085:Acetates / Q000378:metabolism; D000693:Anaerobiosis; D056804:Biofuels / Q000032:analysis*; D019149:Bioreactors; D002247:Carbon Isotopes / Q000032:analysis; D019605:Euryarchaeota / Q000378:metabolism; D005232:Fatty Acids, Volatile / Q000032:analysis; D005374:Filtration; D008697:Methane / Q000032:analysis / Q000378:metabolism*; D017019:Methanosarcinaceae / Q000378:metabolism*; D059013:Microbial Consortia; D003313:Zea mays
D000085:Acetates; D056804:Biofuels; D002247:Carbon Isotopes; D005232:Fatty Acids, Volatile; D008697:Methane