Most emission inventories of quarries contain point sources such as cement kilns and hot asphalt
plants. However, quarry equipment is a major source of emissions that is often overlooked or not
accurately estimated. A variety of minerals are mined in the San Antonio region: limestone, aggregate,
granite, sand and gravel, and lignite. Current methodologies, including the use of NONROAD model
factors, have proven unreliable in developing an accurate emissions inventory for the San Antonio
region. Since quarry equipment emits 3.2 tons of nitrogen oxides (NOx) a day in the San Antonio area, it
is important to have a methodology that produces accurate emissions estimations.