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Quantification of methane emissions from full-scale open windrow composting of biowaste using an inverse dispersion technique
- Marlies Hrad, Erwin Binner, Martin Piringer, Marion Huber-Humer
- Waste management 2014 v.34 pp. 2445-2453
- acetylene, composts, greenhouse gas emissions, landfills, methane, models, sieving, tracer techniques, wastes, wind speed, windrow composting
- 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.