In March 2005, the U.S. Environmental Protection Agency (EPA) promulgated the Clean Air Mercury Rule (CAMR), the first rule ever to restrict mercury emissions from coal-fired power plants. Because the rule is designed to be a cap-and-trade program, mercury measurement is an important component. As a result, substantial effort and resources have been invested in developing mercury measurement protocols both in terms of continuous mercury measurement for compliance purposes and reference methods for conducting relative accuracy test audits (RATAs). Although utilities are the largest source of anthropogenic mercury, they are not the only source. EPA has announced mercury emission standards for new cement kilns but currently exempts existing facilities. Many states are also reviewing the potential of reducing mercury from other sources such as metals smelting, waste-to-energy facilities, and the cement industry. In the manufacture of cement, four raw materials are necessary, limestone, shale, clay, and iron slag. Of these four raw materials, three (limestone, shale, clay) are generally mined on-site, with only the iron slag being imported. To provide the energy required for the processing of the kiln feed in the pyroprocess, a typical plant can use coal, natural gas, used oil, tire-derived fuels, and/or other refuse-derived fuels. A potential source of mercury can be from either the raw materials or the fuel used during the cement-manufacturing process.
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