Government Accountability Office
http://www.gao.gov/products/GAO-12-545R
http://www.gao.gov/assets/600/590188.pdf (letter to Chairman Whitehouse)
Older electricity generating units—those that began operating in or before 1978—provided 45 percent of electricity from fossil fuel units in 2010 but produced a disproportionate share of emissions, both in aggregate and per unit of electricity generated. Overall, in 2010 older units contributed 75 percent of sulfur dioxide emissions, 64 percent of nitrogen oxides emissions, and 54 percent of carbon dioxide emissions from fossil fuel units. For each unit of electricity generated, older units collectively emitted about 3.6 times as much sulfur dioxide, 2.1 times as much nitrogen oxides, and 1.3 times as much carbon dioxide as newer units…
Your content really informative as well as helpful for my Electricity Generation Plants Projects Research and Development.