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Hrad M.,University of Natural Resources and Life Sciences, Vienna | Binner E.,University of Natural Resources and Life Sciences, Vienna | Piringer M.,Institute for Meteorology and Geodynamics | Huber-Humer M.,University of Natural Resources and Life Sciences, Vienna
Waste Management | Year: 2014

An inverse dispersion technique in conjunction with Open-Path Tunable-Diode-Laser-Spectroscopy (OP-TDLS) and meteorological measurements was applied to characterise methane (CH4) emissions from an Austrian open-windrow composting plant treating source-separated biowaste. Within the measurement campaigns from July to September 2012 different operating conditions (e.g. before, during and after turning and/or sieving events) were considered to reflect the plant-specific process efficiency. In addition, the tracer technique using acetylene (C2H2) was applied during the measurement campaigns as a comparison to the dispersion model. Plant-specific methane emissions varied between 1.7 and 14.3gCH4/m3d (1.3-10.7kg CH4/h) under real-life management assuming a rotting volume of 18,000m3. In addition, emission measurements indicated that the turning frequency of the open windrows appears to be a crucial factor controlling CH4 emissions when composting biowaste. The lowest CH4 emission was measured at a passive state of the windrows without any turning event ("standstill" and "sieving of matured compost"). Not surprisingly, higher CH4 emissions occurred during turning events, which can be mainly attributed to the instant release of trapped CH4. Besides the operation mode, the meteorological conditions (e.g. wind speed, atmospheric stability) may be further factors that likely affect the release of CH4 emissions at an open windrow system. However, the maximum daily CH4 emissions of 1m3 rotting material of the composting plant are only 0.7-6.5% of the potential daily methane emissions released from 1m3 of mechanically-biologically treated (MBT) waste being landfilled according to the required limit values given in the Austrian landfill ordinance. © 2014 Elsevier Ltd. Source


Hrad M.,University of Natural Resources and Life Sciences, Vienna | Piringer M.,Institute for Meteorology and Geodynamics | Kamarad L.,University of Natural Resources and Life Sciences, Vienna | Baumann-Stanzer K.,Institute for Meteorology and Geodynamics | Huber-Humer M.,University of Natural Resources and Life Sciences, Vienna
Environmental Monitoring and Assessment | Year: 2014

Open digestate storage tanks were identified as one of the main methane (CH4) emitters of a biogas plant. The main purpose of this paper is to determine these emission rates using an inverse dispersion technique in conjunction with open-path tunable diode laser spectroscopy (OP-TDLS) concentration measurements for multisource reconstruction. Since the condition number, a measure of "ill-conditioned" matrices, strongly influences the accuracy of source reconstruction, it is used as a diagnostic of error sensitivity. The investigations demonstrate that the condition number for a given source-sensor configuration in the highly disturbed flow field within the plant significantly depends on the meteorological conditions (e.g., wind speed, stratification, wind direction, etc.). The CH4 emissions are retrieved by removing unrepresentative periods with high condition numbers, which indicate uncertainty in recovering the individual sources. In a final step, the CH4 emissions are compared with the maximum biological methane potential (BMP) in the digestate analyzed under laboratory conditions. The retrieved methane emission rates represent an average of 50 % of the maximum BMP of the stored digestate in the winter months, while they comprised an average of 85 % during the measurement campaigns in the summer months. The results indicate that the open tanks have the potential to represent a substantial emission source even during colder periods. © 2014 Springer International Publishing Switzerland. Source


Hrad M.,University of Natural Resources and Life Sciences, Vienna | Piringer M.,Institute for Meteorology and Geodynamics | Kamarad L.,University of Natural Resources and Life Sciences, Vienna | Baumann-Stanzer K.,Institute for Meteorology and Geodynamics | Huber-Humer M.,University of Natural Resources and Life Sciences, Vienna
Environmental Monitoring and Assessment | Year: 2014

Open digestate storage tanks were identified as one of the main methane (CH4) emitters of a biogas plant. The main purpose of this paper is to determine these emission rates using an inverse dispersion technique in conjunction with open-path tunable diode laser spectroscopy (OP-TDLS) concentration measurements for multisource reconstruction. Since the condition number, a measure of “ill-conditioned” matrices, strongly influences the accuracy of source reconstruction, it is used as a diagnostic of error sensitivity. The investigations demonstrate that the condition number for a given source-sensor configuration in the highly disturbed flow field within the plant significantly depends on the meteorological conditions (e.g., wind speed, stratification, wind direction, etc.). The CH4 emissions are retrieved by removing unrepresentative periods with high condition numbers, which indicate uncertainty in recovering the individual sources. In a final step, the CH4 emissions are compared with the maximum biological methane potential (BMP) in the digestate analyzed under laboratory conditions. The retrieved methane emission rates represent an average of 50 % of the maximum BMP of the stored digestate in the winter months, while they comprised an average of 85 % during the measurement campaigns in the summer months. The results indicate that the open tanks have the potential to represent a substantial emission source even during colder periods. © 2014, Springer International Publishing Switzerland. Source

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