During the past decade, we made significant progress in reducing the emissions of air pollutants from our power plants. During 2010, approximately 6 million workhours were devoted to construction-related activities at our power plants, most of them on environmental retrofits. Since 2004, we have invested more than $5 billion to install state-of-the-art air emissions controls on many of our coal-fired power plants. We spent additional billions on low-sulfur fuel, chemical reagents and other pollution control measures.

Between the late 1990s and 2010, our investments have led to annual reductions in sulfur dioxide emissions of more than 800,000 tons, or about 65 percent, and to nitrogen oxide emissions by more than 450,000 tons, or about 80 percent. Most of the installed controls are on our Midwestern power plants, where more than 80 percent of our coal-fired generation is located. One flue gas desulfurization unit (scrubber) came on line in 2010 at the Amos Plant in West Virginia; the third and final scrubber at that plant came on line early in 2011. See the update on the 2007 NSR consent decree.

To meet our commitment made through the Chicago Climate Exchange, we reduced or offset our carbon dioxide emissions by approximately 95 million metric tons between 2003 and 2010, exceeding our goal of 48 million metric tons. Much of this reduction resulted from reduced operation of our fossil-fueled power plants. We also worked to improve the efficiency of our power plants, invested in forestry and other offsets and increased the size of our renewable energy portfolio. One source of offsets was agricultural methane; we have cancelled that contract because of the lack of a federal climate mandate and uncertainty over cost recovery. Read more about this in the Climate Change section of this report. Our CO₂ emissions will decline further as we retire coal units but they may increase slightly in the near-term as the economy and electricity use rebounds.