ECN publication
Validatie van de methaan-emissie-reductie op stortplaats Nauerna
Published by: Publication date:
ECN 1-6-1998
ECN report number: Document type:
ECN-C--98-052 ECN publication
Number of pages: Full text:
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Methane emission measurements were performed at a landfill site locatedapproximately 20 km west of Amsterdam, Netherlands. These measurements aimed to determine the emission level of the 60 ha landfill site after the implementation of a gas extraction unit. In order to assess the emission, the concentration levels in the plume downwind of the site were determined using a Tuneable Diode Laser Atomic Spectrometer mounted in a small truck. This measurement system combines a high selectivity for methane (or nitrous oxide) with a high time resolution (up to 20 Hz is possible). The position of the truck was determined using a differential global positioning system (DGPS) that uses up to 8 satellites to retrieve the position. Meteorological measurements were obtained using an ultrasonic anemometer located on top of the landfill. The concentrations measured on transects through the plume that run about 780 m downwind of the centre of the landfill were compared with modeled concentrations. The model divides the landfill area into 100 point sources and calculates a gaussian plume for each point. The source strength is estimated by making a match between the measured and modelled concentrations in the plume. A validation of the model was done by releasing a tracer (nitrous oxide) from a known location on the landfill. The TDLAS is capable of measuring N2O simultaneous with CH4. A total number of 14 transects have been obtained. For 11 transects plumes were found. The emissions that were estimated ranged from 19 gCH4.s"-"1 to 40 gCH4.s"-"1 with one extreme value of 65 gCH4.s"-"1. The best guess for the average emission was estimated to be 31 #+# 13 gCH4.s"-"1. In 1997 the same kind of measurements was performed to evaluate the emission level before implementation of this extraction system. In that campaign 8 plume measurements were obtained, which resulted in a best guess for the landfill emission of 62 #+#12 gCH4.s"-"1. The conclusion is that a reduction of about 50% of the emission has occurred. This is partially due to the reduction of the emission because of the extraction system, the other reason is that the CH4 production inside the landfill (estimated using CH4 formation models) is decreasing. The decrease estimated from the formation model estimates and the production figures of the extraction system indicate a smaller emission reduction than observed from the measurements. The difference is not alarming facing the uncertainty both in the measurements presented here and the uncertainty in the production estimates

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