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Gewählte Doctoral Thesis:

Johannes Bachmaier (2012): Treibhausgasemissionen und fossiler Energieverbrauch landwirtschaftlicher Biogasanlagen. Eine Bewertung auf Basis von Messdaten mit Evaluierung der Ergebnisunsicherheit mittels Monte-Carlo-Simulation..
Doctoral Thesis - Institut für Landtechnik, BOKU-Universität für Bodenkultur, pp 137. UB BOKU obvsg FullText

Data Source: ZID Abstracts
Abstract:
So far, the environmental impact of biogas production and utilization has been evaluated mostly on the basis of theoretical models and without taking into account data uncertainties. This work presents balances of greenhouse gas emissions and fossil energy consumption for real biogas plants in agriculture, including the evaluation of data uncertainty. The study is based on extensive time series of material flows, collected from 16 agricultural biogas plants with diverse designs between 2007 and 2010. The mass balance study follows the standards for life cycle assessment using the software Umberto. Each variant evaluated is based on an observation period of one year. The functional unit is one kilowatt-hour of electricity (kWhel) exported to the grid. Side-products of electricity generation are included as credits. To quantify uncertainty due to inaccurate input data, stochastic risk analysis was performed using the method of Monte-Carlo simulation. The results from overall 21 variants of 16 different biogas plants demonstrate that in comparison to a fossil reference system, electricity supply from biogas can avoid greenhouse gas emissions and save fossil resources. Greenhouse gas emissions calculated per kWhel from biogas ranges from a net credit of 321 g CO2e to net emissions of 275 g CO2e. The consumption of fossil resources per kWhel varies from -0.83 kWhfossil to 0.38 kWhfossil. The variability and inaccuracy of direct methane emissions, credits for side-products and nitrous oxide emissions are mainly responsible for the large variation of the calculated environmental impact. The efficient utilization of heat energy from co-generation, low methane emissions, a low internal electricity consumption and a slim nitrogen cycle are main factors to reduce greenhouse gas emissions and fossil resource consumption of biogas plants in agriculture.

Betreuer: Boxberger Josef
1. Berater: Moitzi Gerhard

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