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Bonn, Germany

Liebetrau J.,DBFZ German Biomass Research Center | Reinelt T.,DBFZ German Biomass Research Center | Clemens J.,Gewitra mbH | Hafermann C.,Gewitra mbH | And 2 more authors.
Water Science and Technology | Year: 2013

With the increasing number of biogas plants in Germany the necessity for an exact determination of the actual effect on the greenhouse gas emissions related to the energy production gains importance. Hitherto the life cycle assessments have been based on estimations of emissions of biogas plants. The lack of actual emission evaluations has been addressed within a project from which the selected results are presented here. The data presented here have been obtained during a survey in which 10 biogas plants were analysed within two measurement periods each. As the major methane emission sources the open storage of digestates ranging from 0.22 to 11.2% of the methane utilized and the exhaust of the co-generation units ranging from 0.40 to 3.28% have been identified. Relevant ammonia emissions have been detected from the open digestate storage. The main source of nitrous oxide emissions was the co-generation unit. Regarding the potential of measures to reduce emissions it is highly recommended to focus on the digestate storage and the exhaust of the co-generation. © IWA Publishing 2013.

Liebetrau J.,DBFZ German Biomass Research Center | Clemens J.,Gewitra mbH | Cuhls C.,Gewitra mbH | Hafermann C.,Gewitra mbH | And 3 more authors.
Engineering in Life Sciences | Year: 2010

The emissions of ten representative agricultural biogas plants located in Germany were investigated to generate a comprehensive inventory of greenhouse gas emissions that occur within the biogas production process. The main methane emission sources were identified by a site inspection with a portable flame ionization detector. Whenever possible, the released amount of methane was quantified by installing a chamber around the identified sources. The chamber was flushed with air, and the values of the flow rate and the measured concentrations in the exhaust allowed the determination of the methane emissions. The two main sources of emissions turned out to be the digestate storage tanks when constructed without a sealed cover and the cogeneration unit. In some cases, improper handling of equipment within the gas-filled digester headspaces and pipes caused substantial emissions. The results will be used for a comprehensive life cycle assessment of the biogas production process. Finally, sufficient measures for a substantial reduction of emissions will be developed. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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