How to quantify fugitive methane emissions from landfills
There are two main challenges when quantifying fugitive methane emissions from landfills to the atmosphere: The spatial and the temporal variation of the emission. But the dynamic tracer gas dispersion method can help overcome these challenges.
How much methane is being emitted to the atmosphere from landfills?
Biological degradation of organic material in anaerobic conditions will form methane which is known as a potent greenhouse gas. While some of the produced methane can be used for producing energy, a part of the methane in landfills is emitted to the atmosphere every year, increasing the warming of the atmosphere.
Minimizing the emissions of methane into the atmosphere can thus contribute to revoking the current warming of the Earth.
But how can we be certain of the amounts of methane that are being emitted to the atmosphere from landfills?
Dynamic tracer gas dispersion method can help overcome spatial variation
Quantifying methane from landfills poses several challenges, the biggest of them being spatial and temporal variation of the emissions.
The spatial variation is specifically a major challenge, as emissions can occur from various soil cracks, wells or even migrate into neighbouring areas. This is a problem because these point sources at large areas are difficult to locate and quantify individually.
To overcome the spatial emission variation, it is a good idea to measure the integrated emission from the whole landfills.
The dynamic tracer gas dispersion method makes it possible to measure the integrated emission. The method relies on release of a tracer gas close to the emitting source, e.g. near cracks and wells on a landfill, and subsequent downwind measurements of methane and the tracer gas. By comparing the downwind concentrations and knowing the release rate of tracer gas, the total methane emission from the emitting source can be calculated.
Temporal variation of the emission is under study using the dynamic gas dispersion method
The temporal variation is different from source to source. Research has shown that especially the atmospheric pressure plays a significant role in the temporal emission variation from landfills.
A measurement using the dynamic tracer gas dispersion method usually takes hours. To quantify an average emission from a landfill, it is therefore imperative to find the right period that represents a typical atmospheric condition for the location.
Studies are currently made, using the dynamic tracer gas dispersion method, in longer periods and during stable and unstable atmospheric conditions, as well as with and without mechanical gas extraction from the landfills. The goal is to gain more knowledge about the emission dynamic to enable quantification in unstable conditions and relate these to an average/yearly emission.
Contact us for more information about quantification of methane emissions or visit our page on air emissions measurements.