Even with current advances in the development of mercury control technologies, there is no single best way to control mercury emissions that can be applied to all power plants in the UNITED STATES. Based on available mercury control technologies, the cost of mercury removal is estimated to be $11,000 to $150,000 per kg ($5,000 to $70,000 per pound)[17] and adds up to 0.005 dollars per kWh to the cost of electricity. Mercury emissions from coal-fired boiler flue gases is a much more difficult problem due to the low concentrations of mercury in electric boiler flue gases (typically 0.01 versus 100+ ppm) and the chemical speciation of the mercury in different physical forms. An understanding of the physical and chemical distribution of mercury in the system is essential to the development and deployment of control systems. There are a number of currently available control technologies that coal-fired power plants use to reduce their mercury emissions into the atmosphere. The effectiveness of these technologies for mercury removal varies depending on the characteristics of the coal and the configuration of the power plant. In general, two approaches can be adapted to reduce mercury emissions from coal-fired boilers: pollution prevention and post-combustion pollution control. . Pollution prevention, in some cases, uses commercially available technologies that do not require capital investment. Many conventional post-combustion control technologies used in coal-fired power plants to control SO2 and particulate matter have the co-benefit of reducing Hg emissions. A combination of some of these controls can achieve high control (above 95%) of mercury. Coal cleaning can reduce the Hg content of coal fed... middle of paper ... candidate which has been shown to oxidize >95 percent of elemental mercury in pilot-scale testing.[21] The iron oxides, Fe2O3 and Fe3O4 present in fly ash, have been shown to promote mercury oxidation.[23,24] Although fly ash appears to promote mercury oxidation, studies have shown that only a small portion of the active surface area (1 to 3 percent) plays a role in the process.[25, 26] Fe2O3 has also been used as an effective catalyst in small-scale systems.[27, 28] It has been demonstrated that two refractory components, Al2O3 and TiO2, oxidize some elemental mercury.[29,30] Other metal catalysts that promote mercury oxidation include iridium[31], MnO2[28] and CuO .[28] Photochemical oxidation of mercury by ultraviolet irradiation, particularly promising in the presence of TiO2, is another emerging technology being investigated for use in coal-fired power plants..[32-35]