|Abstract Title:||Quantifying temporal variation in methane emission from a landfill using tracer dispersion method|
|Session Choice:||Fence line monitoring & measurement of fugitive/diffuse emissions|
|Presenter Name:||Dr Jacob Mønster|
|Co-authors:||Dr Christian Juncher Jorgensen|
Dr Anders Michael Fredenslund
Prof Charlotte Scheutz
Abstract Information :
Methane plays a significant role in the Earths energy balance and thus the increasing concentration in the atmosphere contribute to the rising average temperature of the Earth. The increasing concentration in caused by emission from many different sources, both natural and anthropogenic. Methane is a strong greenhouse gas. Methane has a relatively short atmospheric lifetime compared to carbon dioxide. Methane therefore appears as an even stronger greenhouse gas when the global radiation budget is modelled in a shorter time window than the normally used 100 years. A change in the global methane emission can therefore change the radiation budget much faster on a short time scale. This fact causes an increasing focus on reducing methane emissions to the atmosphere.
One of the important anthropogenic sources to methane is landfills. Waste handling and landfilling differs greatly between the different countries in the world. While some countries are having uncontrolled landfills, others are burning most of the waste for heat and energy recovery. Some countries are controlling the landfills building in gas extraction systems to recover the generated methane and use it for producing energy. Common for all landfills are that methane is generated and that a part of the methane is emitted to the atmosphere. Historically, the methane generation and emission has been modelled using knowledge about the organic content of the waste. However, there is often limited knowledge about how big a part of the landfill generated methane that is lost to the atmosphere through fugitive emission from the landfill surface. The surface emissions have a large spatial and temporal variation and thus very difficult to quantify. Some measurement methods, such as DIAL and tracer dispersion method, can overcome the spatial variation and quantify the emission from the whole landfill. However, these methods are normally only used to measure in a short timeframe (hours) at each part of the landfill (DIAL) or whole landfill (tracer dispersion method), which makes it difficult to obtain the temporal variations over days and weeks. The tracer dispersion method does not use wind speed and direction in the quantification of the emission and the method can therefore be used for studying the temporal emission variation during changing atmospheric conditions.
We have applied the tracer dispersion method at a covered landfill with gas extraction. Measurements were done in time windows to cover various atmospheric conditions, such as high/low and increasing/decreasing atmospheric pressure. Some old landfills with gas extraction are having so low methane concentration that the gas extraction must be stopped in periods for building up the methane inside the landfill. We therefore also tested how fast the fugitive methane emission from a landfill change as a result to starting and stopping the extraction of gas from the landfill.