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The production of biogas within a landfill is a product of anaerobic decomposition, a process by which biodegradable organic materials are utilized as substrates by microorganisms. Biogas produced within a landfill typically consists of 50-70% methane, with the balance being carbon dioxide and small amounts of other trace gases. As a result, landfills have consistently been listed as one of the largest sources of anthropogenic methane in the United States by entities such as the Intergovernmental Panel on Climate Change (IPCC) and the U.S. Environmental Protection Agency (U.S. EPA). These agencies also maintain inventories of global greenhouse gas (GHG) emissions and/or inform policy-making. 

The objectives of this report are to: 

  • Calculate the amount of organic waste and degradable organic carbon (DOC) in MSW and other Subtitle D waste streams using sample-and-sort composition data. 
  • Determine the relative fraction of MSW and non-MSW (e.g. C&D, ash, industrial) deposited in MSW landfills in the U.S., and the resulting bulk waste DOC values. 
  • Explore if current U.S. reporting guideline values are validated by composition-based DOC results 

These have been accomplished through the analysis of recent waste composition sample-and-sort data, state and federal facility reporting datasets, and the U.S. EPA Facts & Figures data from 1960 through present. 

For clarity, this report provides separate analyses that are divided into two key sections: 

  • Analysis of the MSW Stream. This section analyzes DOC values for only the MSW fraction of waste materials, herein referred to as DOCMSW. The analysis is pertinent particularly to landfills that only accept MSW materials or receive negligible non-MSW materials. Further, the analysis is useful in understanding DOC values of the MSW steam entering other landfills. The DOC guideline of 0.31 is compared with DOCMSW values computed based on U.S. EPA’s Facts and Figures reports over a 20-year period as well as those computed from state waste characterization studies. 
  • Analysis of All Waste Entering MSWLFs. This section summarizes data regarding non-MSW materials being accepted at MSWLFs. This information is then used to evaluate the impact of these non-MSW materials on DOC values. Values are expected to change given the relative fractions of organic materials used in the DOC computation are greatly affected by the addition of non-MSW streams. DOC values are computed for various states based on the relative fraction of MSW and non-MSW Subtitle D waste(s) accepted, herein referred to as DOCSubD to specify it reflects all Subtitle D wastes accepted at MSWLFs. These values are then compared to the DOC guideline of 0.20 for bulk wastes at MSWLFs. 
  • Summary Statistics & Future Work. This section summarizes the attempt to validate DOC guideline values using the findings from Sections I and II. The statistical significance of the findings based on one-tailed, single sample t-tests is also discussed.