During 2013, approximately 36 billion tons of CO2 were emitted into the atmosphere – an average of roughly 5 tons of CO2 for every man, woman and child alive today. CO2 emissions in 2013 were 60% higher than in 1990, the year the Kyoto Protocol was adopted.
The burning of coal, primarily for the generation of electricity, accounted for 43% of global CO2 emissions or roughly 15.5 billion tons during 2013. Petroleum was the next largest source of CO2 emissions, approximately 33% or roughly 12 billion tons. Natural gas consumption and cement production accounted for most of the remaining CO2 emissions (18% and 5.5%, respectively).
China is by far the largest consumer of coal accounting for 49% of the world total, with the US a distant second at 10.5% and India at 9%.
Global coal consumption is currently forecast by the International Energy Agency to grow at an average annual rate of 2.1% through 2019, reaching a level in excess of 9 billion metric tons per year by 2019.
In 2013 the US consumed 925 million short tons of coal (839 million metric tons), a vast majority of it used to generate electricity. During 2013, coal powered steam generators were used to generate approximately 39% of the electricity consumed in the US but they accounted for almost 76% of the total CO2 emissions from the electrical power sector.
To get a better idea of the role that coal plays in today’s electrical power system it is worth examining in some detail a typical, large scale, US coal power facility, such as Wisconsin Energy’s Oak Creek generator site shown in the figure below:
This site which occupies approximately 1,000 acres of land on the shore of Lake Michigan some 20 miles south of Milwaukee, consists of two interconnected power plants. The older of the two, referred to as the “Oak Creek Power Plant (OCPP)” was built at an initial cost of $246 Million between 1959 and 1967. It is equipped with four steam turbines with a total capacity of 1,135 megawatts. Advanced air quality control systems were installed in 2012 on all four generating units at a combined cost of $750 million.
The newer of the two power plants at the Oak Creek site, referred to as “Oak Creek Expansion Units 1 and 2 (OCXP)”, was built at a cost of $2.3 billion. It came on line in 2011 and is equipped with two large turbines with a net total generating capacity of 1,230 megawatts.
The two power plants, OCPP and OCPX, use a shared coal handling and distribution system. The coal handling system has an aggregate indoor storage capacity of 77,500 tons and an aggregate outdoor storage capacity of 750,00 tons. The facility has 26 large pulverizers capable of crushing coal at an aggregate rate of more than 1,000 tons per hour.
The Oak Creek operating site uses water drawn from Lake Michigan to condense the exhaust steam from the from the turbines back into water which is then returned to the lake. The combined cooling water intake system for OCPP and OCXP draws up to 1.56 million gallons of water from the lake every minute. The water intake pipe runs underground for approximately 2 miles out into Lake Michigan and is 28 feet in diameter. Most coal-fired generating plants recirculate water from condensers to a cooling tower and back, which sends heat into the atmosphere. Oak Creek relies instead upon what is referred to as “once-through” cooling technology which eliminates the need for large cooling towers. Once-through cooling is feasible only when there is a very large body of water available.
When operating near full capacity, the Oak Creek site consumes approximately 1,000 tons of coal per hour (approximately 10 rail cars of coal) and emits approximately 2,000 metric tons of CO2 per hour into the atmosphere. [Note the long line of coal cars in the foreground of the photograph of the Oak Creek site.]
As of the end of 2012 there were 1,308 coal-fired power generating units at 557 power plant sites in the US with a total capacity of 310 Gigawatts (310,000 Megawatts). The Oak Creek power plant site represents less than 1% of the total US coal-fired electrical capacity.