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Gewählte Master / Diploma Thesis:

Lutz Christian Krapf (2008): Suoercritical Carbon Dioxide Pre-treatment of Rye Straw for Biogas Generation.
Master / Diploma Thesis, BOKU-Universität für Bodenkultur, pp 91. UB BOKU obvsg FullText

Data Source: ZID Abstracts
Abstract:
The process of anaerobic digestion describes the transformation of organic material into methane-rich biogas. However, utilization of lignin-rich biomass is characterized by a retarded transformation of this process of biomass conversion. The lignocellulosic matrix constitutes a barrier against enzymatic hydrolysis of the polysaccharides into oligo- and monosaccharides. By application of two different pre-treatment methods, this study aimed for a better transformation of rye straw into biogas via anaerobic digestion. In this regard, the aim was to rupture the lignin-carbohydrate complexes by means of thermo-chemical hydrolysis. Both methods tested in this work included the utilization of supercritical carbon dioxide. The first pre-treatment process applied a binary CO2-H2O system. The second pre-treatment utilized a ternary mixture of carbon dioxide, ethanol, and water. Ethanol is a useful organic solvent for non-polar substances such as lignin. The application of a supercritical fluid is believed to increase solvolysis of lignin and subsequent removal out of the cell wall. Formation of carbonic acid due to dissolution of CO2 in water at elevated pressure is believed to improve pre-treatment processes. Results from this work do not show a clear tendency regarding the impact of the application of supercritical carbon dioxide on subsequent fermentation of the rye straw. An increase in methane formation has been achieved for the pre-treatment with the ternary mixture, compared to straw that only has been mechanically comminuted. However, the specific effect of supercritical carbon dioxide remained rather unclear. No increase in biogas formation could be achieved with regard to the pre-treatment process applying the binary mixture. Besides these physico-chemical requirements on pre-treatment processes, energy balances for such systems are considerably important for assessing its applicability for biobased energy systems.

Beurteilende(r): Wendland Martin

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