With the increasing application of energy crops in agricultural biogas plants and increasing digester volumes, the phenomenon of self-heating in anaerobic digesters appeared in some cases. Until now this development was just known from aerobic systems. To obtain an idea of the thermodynamics inside an anaerobic digester, a detailed analysis of all heat fluxes in a full-scale agricultural biogas plant was carried out. Several experiments were realised to quantify the influences of different internal and external energy sources. To estimate the impact of self-heating in anaerobic systems, data of other full-scale agricultural biogas plants in Austria were collected. Alternatives to the cooling of the digesters are discussed based on individual experiences of several plants. A connection between carbohydrate-rich substrates, especially with high starch contents, and the self-heating could be shown. From the results it can be assumed that the anaerobic digestion of most energy crops is exothermic, which is in contrast to the current thermodynamic belief.
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Research Article| April 01 2006
Self-heating of anaerobic digesters using energy crops
1BOKU - University of Natural Resources and Applied Life Sciences, Vienna, Department for Agrobiotechnology, IFA-Tulln, Institute for Environmental Biotechnology, Konrad Lorenz Str. 20, 3430 Tulln, Austria
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Water Sci Technol (2006) 53 (8): 159–166.
H. Lindorfer, R. Braun, R. Kirchmayr; Self-heating of anaerobic digesters using energy crops. Water Sci Technol 1 April 2006; 53 (8): 159–166. doi: https://doi.org/10.2166/wst.2006.246
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