Modernizing Models and Data on Methane Production from Landfills
Investigators: North Carolina State University
There have been changes in both the operation of landfills and in waste composition since the EPA developed default model parameters for its landfill gas emissions model (LandGEM). The accuracy of this model is important as it guides landfill owners on appropriate investments in gas recovery equipment, and is also used to estimate greenhouse gas emissions. The objective of this project is to develop an improved data set and model to predict methane production from U.S. landfills. It is thought that by the acquisition and analysis of current data on landfill gas, improved estimates for the decay rate (k) and methane yield (L0), two key input parameters that are used in LandGEM, can be provided. In addition to improved estimates of k and L0, whether or not alternate model formulations provide improved predictability will be considered.
To date, 5 landfills have been visited and data analysis is in progress and the process of identifying landfills for data analysis is ongoing. As such, inquires for potential site visits are welcomed as efforts are made to identify landfills with the highest quality data sets. Date requirements include:
1. records of gas volume and methane composition for at least 5 years,
2. the mass and types of waste received, which can broadly be classified as containing significant biodegradable material (e.g., residential, commercial, institutional waste) as opposed to inert material (e.g., ash, contaminated soil), and
3. the history of cover type and gas well installation that will be used to estimate gas production rates from gas collection data.
Finally, uncertainty in model predictions will be characterized such that the results can be used to predict how much gas can be generated with a particular degree of certainty, such as noting there is an 80% chance that a landfill will generate for example, 4000 cfm, and a 90% chance that the landfill will generate 3200 cfm. Ultimately, the project will provide a more robust way to analyze landfill gas generation.
Wang, X, Nagpure, A, DeCarolis, J, and Barlaz, M. (2015), “Characterization of Uncertainty in Estimation of Methane Collection from Select U.S. Landfills,” Environmental Science & Technology, ACS, 49, 1545-1551.