TABLE OF CONTENTS Landfill gas is produced by the microbial decomposition of landfilled waste in an oxygen free (anaerobic) atmosphere. The gas is approximately 65 percent methane and 35 percent carbon dioxide plus traces of other organic compounds and the composition varies with age and the type of waste (Table 12.1). The odor of landfill gas is associated with trace compounds such as hydrogen sulfide (H 2S), mercaptans (R-SH), and ethylene (CH 2=CH 2).
| Component | Percent by volume | Characteristics |
|---|---|---|
| Methane | 45 60 | Methane is a naturally occurring gas. It is colorless and odorless. Landfills are the single largest source of U.S. man-made methane emissions. |
| Carbon dioxide | 40 60 | Carbon dioxide is naturally found at small concentrations in the atmosphere (0.03%). It is colorless, odorless, and slightly acidic. |
| Nitrogen | 2 5 | Nitrogen comprises approximately 79% of the atmosphere. It is odorless, tasteless, and colorless. |
| Oxygen | 0.1 1 | Oxygen comprises approximately 21% of the atmosphere. It is odorless, tasteless, and colorless. |
| Ammonia | 0.1 1 | Ammonia is a colorless gas with a pungent odor. |
| NMOCs (non-methane organic compounds) | 0.01 0.6 | NMOCs are organic compounds (i.e., compounds that contain carbon). (Methane is an organic compound but is not considered an NMOC.) NMOCs may occur naturally or be formed by synthetic chemical processes. NMOCs most commonly found in landfills include acrylonitrile, benzene, 1,1-dichloroethane, 1,2-cis dichloroethylene, dichloromethane, carbonyl sulfide, ethylbenzene, hexane, methyl ethyl ketone, tetrachloroethylene, toluene, trichloroethylene, vinyl chloride, and xylenes. |
| Sulfides | 0 1 | Sulfides (e.g., hydrogen sulfide, dimethyl sulfide, mercaptans) are naturally occurring gases... |
