Landfills are emission sources of particulates and gases. Active sites conduct many activities that produce particulate emissions including, but not limited to; cover material quarrying, soil screening, rock crushing, open cover material storage piles, haul roads, solid waste compaction, cover application, composting, and green waste recycling. Particulate emissions from inactive landfills are usually limited to short term cover maintenance projects. Landfill gases containing methane, carbon dioxide, hydrogen sulfide, and a wide variety of organic compounds are released from the decomposition of waste at all sites. The quantity of landfill gas released depends primarily on the size, age, and moisture content of each disposal site. Additionally, combustion by-products are emitted from landfills equipped with flares and energy recovery systems. Emission estimation techniques used by the District are generally based upon methods and emission factors specified in AP-42.