29 May 2008
Governments, Industry Working to Stem CO2 Emissions from Coal
Power plant advances seen as key to lowering carbon dioxide in atmosphere
Washington -- Coal is among the fastest-growing components of the global energy supply, but power plants that burn coal are major contributors to rising atmospheric concentrations of the greenhouse gas carbon dioxide (CO2), which contributes to global warming.
Solutions to this conflict are complex, expensive and evolving. A growing number of groups worldwide -- governments, power generators, equipment suppliers, research organizations -- are working together and separately to reduce CO2 and other emissions from this critical resource.
Major approaches for reducing CO2 emissions from power plants include improving energy efficiency and sequestering carbon dioxide. Sequestering is the process of capturing emissions from power plants and either storing gas deep underground in porous rock formations or injecting it into depleted oil and gas fields or coal seams. (See “Tests on Capturing, Storing Carbon Dioxide Move Forward.”)
Injecting CO2 into an oil field -- enhanced oil recovery -- reduces the oil’s viscosity, expands its volume and changes its stickiness, all of which allow drillers to get more oil out of the ground.
In the United States and around the world, engineers have been capturing CO2 from industrial flue streams for 70 years and injecting it underground for 30 years to enhance oil recovery. But sequestration efforts that combine capture and storage have been occurring only since about 1997.
A range of capture technologies and demonstration projects are being developed worldwide but none is yet commercially available.
“The challenge of carbon capture,” Victor Der, deputy assistant secretary for clean coal at the U.S. Department of Energy (DOE), told America.gov, “is the cost of the equipment and the energy penalty associated with capture.”
In capture, CO2 must be separated from the plant’s exhaust gas and then compressed. Both processes require power -- a 30 percent or more energy penalty, depending on the plant design -- that comes from the power plant and reduces the total amount of generated electricity.
“In the total cost of carbon capture and storage,” Der added, “the capture part is about 90 percent of the cost.”
LARGE-SCALE DEMONSTRATIONS
Several countries have initiated large-scale programs for capturing CO2 from coal-fired power plants. In 2006, the Elsam Power Plant in Denmark initiated a pilot program coordinated by the Institut Francais du Petrole and funded by the European Commission.
Another European project, the Zero Emissions Fossil Fuel Power Plant (ZEP), was set up in 2007 with participation by leading public-sector and nongovernmental organizations to promote sequestration technologies for power generation. ZEP will build 12 industrial-scale CO2 capture and geological storage operations in European countries by 2015, with commercial operation around 2020.
In Australia, government-owned ZeroGen is mixing integrated gasification combined cycle (IGCC) technology with CO2 sequestration. The energy-efficient process combines two kinds of turbines, combustion and steam.
ZeroGen was modified from a single project into two stages. The ZeroGen Mark II demonstration, in central Queensland, will develop by 2012 an IGCC power plant that captures and stores CO2 emissions. At the same time, a commercial-scale plant will be developed to come online by 2017.
The U.S. zero-emissions effort, FutureGen, also has been restructured since its announcement in 2003 -- from a near-zero-emissions 275-megawatt power plant that produced hydrogen and electricity from coal to a demonstration of carbon sequestration at multiple commercial-scale (300-megawatt) coal gasification plants.
In the new version of FutureGen, DOE will join with industry to build IGCC plants by funding sequestration technology for several plants slated to be operational by 2015.
“Our fiscal year 2008 budget for sequestration is $118.9 million,” John Grasser, DOE Office of Fossil Energy communications director, told America.gov, “for fiscal year 2009 we have asked for [just over] $149 million, a $30.2 million increase.”
PRIVATE EFFORTS
In the United States, Ohio-based American Electric Power (AEP) -- which began utility operations in 1907 and now delivers electricity to more than 5 million customers in 11 states -- is working with international companies and the Electric Power Research Institute to commercialize carbon sequestration in its power plants.
Two years ago, amid a flurry of rejections, on environmental grounds, by state public utility commissions of applications to build new coal-fired power plants, including some proposed by AEP, the company decided to continue its focus on clean-coal technologies and pursue carbon capture and storage and other new technologies.
“We burn about 80 million tons [72.5 metric tons] of coal a year” Nick Akins, AEP’s executive vice president for generation, told America.gov. “We have some 38,000 megawatts of generation and over 25,000 megawatts of that is coal-fired capacity, so it’s incumbent upon us to ensure that new coal technologies move forward and that our existing power plants remain viable for the future.”
In a project announced in 2007, and with partners Alstom of France and RWE of Germany, AEP is using Alstom technology to capture CO2 from a slipstream (portion) of AEP’s 1,300-megawatt Mountaineer Plant in West Virginia. The slipstream is equivalent to 20 megawatts of generation. The Alstom system will capture up to 200,000 metric tons of CO2 each year for injection into deep saline aquifers at the site.
“If Mountaineer is successful,” Akins said, “our intent is to upscale that even further to a 200- to 250-megawatt facility to be located at one of our power plants to further expand the technology.”
After commercial viability is validated at Mountaineer, AEP plans to install Alstom’s technology on a 450-megawatt coal-fired unit at its Northeastern Station in Oklahoma. The commercial-scale system is expected to be operational at Northeastern around 2012 and to capture about 1.5 million metric tons of CO2 annually for sale to a regional oil and gas operator for enhanced oil recovery.
AEP hopes to have its plants upgraded for carbon sequestration by around 2020, and will seek to participate in DOE’s FutureGen program.
“We’ve participated in conferences around the world associated with our projects, and there’s no question that CO2 is on the radar screen even in Asia,” Akins said. “I think this is one way that the United States can lead the way in terms of developing the [carbon sequestration] technology. It’s not only going to benefit this country but the entire world.”
