Originally published as:Lienen, T., Kleyböcker, A., Verstraete, W., Würdemann, H. (2014) AbstractThe microbial community composition in a full-scale biogas plant fed with sewage sludge and fat, oil and grease (

Background: The use of biogas as renewable resource of energy is of growing interest. To increase the efficiency and sustainability of anaerobic biogas reactors, process failures such as overacidification, foaming, and floating layers need to be investigated to develop sufficient countermeasures and early warning systems to prevent failure.

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Originally published as:Kleyböcker, A., Lienen, T., Liebrich, M., Kasina, M., Kraume, M., Würdemann, H. (2014): Application of an early warning indicator and CaO to maximize the time-space-yield of a completely mixed waste digester using rape seed oil as co-substrate. AbstractIn order to increase the organic loading rate (OLR) and hereby the performance of biogas plants an early warning indicator (EWI-VFA/Ca) was applied in a laboratory-scale biogas digester to control process stability and to steer additive dosing. As soon as the EWI-VFA/Ca indicated the change from stable to instable process conditions, calcium oxide was charged as a countermeasure to raise the pH and to bind long-chain fatty acids (LCFAs) by formation ofaggregates. An interval of eight days between two increases of the OLR, which corresponded to 38% of one hydraulic residence time (HRT), was sufficient for process adaptation. An OLR increase by a factor of three within six weeks was successfully used for biogas production. The OLR was increased to 9.5 kg volatile solids (VS) m -3 d -1 with up to 87% of fat. The high loading rates affected neither the microbial community negatively nor the biogas production process.Despite the increase of the organic load to high rates, methane production yielded almost its optimum, amounting to 0.9 m³ (kg VS)

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