Landfill Methane Emission Monitoring

GHG-1 analyzer package and eddy covariance system for measuring emissions of CH₄, CO₂, and H₂O deployed at Bluff Road Landfill in Lincoln, NE.

Methane (CH₄) plays a critical role in the radiation balance and chemistry of the atmosphere. According to the most recently published IPCC Fourth Assessment Report^[6], methane is the second most important greenhouse gas after carbon dioxide. The global average abundance of methane has increased from 1570 ppb in 1979 to over 1800 ppb in 2011^[7]. The major anthropogenic sources are anaerobic production from landfills, ruminant animals and their waste, release from the mining and use of fossil fuel, burning of biomass, etc.^[5]. On average, over the global scale, landfill methane emissions contribute between 10-19% of the anthropogenic methane burden into the atmosphere^{[2, 4, 6]}. In the United States, as much as 37% of annual anthropogenic CH₄ emissions to the atmosphere are from landfills^[3].

In the United States, the Environmental Protection Agency (USEPA) has recently enacted a new rule related to the mandatory reporting of greenhouse gases, which requires some municipal solid waste landfills to report their emissions of greenhouse gases, including methane.

Many landfills currently report emissions using the inventory method, which is based on methane production rate, the rate of methane oxidation and the amount of methane recovered^[1]. The production rate is based on the estimated rate of decay of the various biodegradable components of solid wastes. This approach often involves large uncertainties due to inaccuracies of the input data and many assumptions in the estimation^[2]. Measuring methane emissions directly from landfills and developing a better understanding of how environmental variables control these emissions are essential for reducing the uncertainty in reported greenhouse gas emissions.

The eddy covariance method is just starting to be used in landfill gas emission studies, although it has been widely used by micrometeorologists and ecologists to measure exchanges of CO₂, H₂O, CH₄ and other gases and energy between various ecosystems and the atmosphere since the late 1980's. The main advantages of this method are that it provides a continuous, automatic, direct measurement of spatially averaged gas flux over a large upwind area with limited labor. These advantages make the eddy covariance technique an excellent tool for understanding the processes, such as how various environmental variables control gas emissions.

The following analyzer packages can be used to measure landfill emissions
of CH₄, CO₂, and H₂O

• Turnkey systems to measure CO₂, H₂O, and CH₄ flux
• Open path and enclosed path options
• Modular systems can be expanded with additional biomet sensors

LI-7500A Open Path CO₂/H₂O Analyzer

• In-situ open path measurements
• Designed for field use
• Low power consumption

LI-7700 Open Path CH₄ Analyzer

• Connects directly to sonic anemometer and CO₂/H₂O analyzer
• High precision
• Low power consumption

For more information on the theory behind the eddy covariance method, view the Ecosystem Gas Exchange application page:

Eddy Covariance