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Here’s a statement you don’t read every day: “We believe that coal use will increase under any foreseeable scenario because it is cheap and abundant.”
That declaration comes right at the start of a recently released study by a dozen faculty members at MIT, writing in a report called “The Future of Coal.” The volume is the second such “future” report written by the interdisciplinary group of academics. Their first study, “The Future of Nuclear Power”, was published in 2003. Work on the coal volume began in 2004.
The lists of reports or books having much good to say about coal are fairly short. But the MIT report, although hardly without its criticism for the fuel as a contributor to greenhouse gas emissions, offers a series of arguments that the industry would do well to note. After all, some coal proponents have had difficulty lately making a case for their position. In its 192 pages, the MIT report offers more than a few useful arguments for the fuel and provides a reasonable basis for debate. Here are some highlights.
First, the authors note the “massive” scale of carbon capture and sequestration required to make what they call “a major difference” in global greenhouse gas concentrations. They calculate that sequestering one gigatonne of carbon each year (roughly equivalent to four gigatonnes of carbon dioxide) would require injecting about 50 million barrels a day of “supercritical CO2” from 600 coal plants on the order of 1,000 MWe.
They go on to say that if 60 percent of the CO2 produced from U.S. coal generation were captured and compressed into a liquid for geologic sequestration, its volume would equal the entire daily U.S. oil consumption of 20 million barrels. To add more perspective, the largest sequestration project currently in operation injects 1 million tons a year of carbon dioxide from the Sleipner gas field into a saline aquifer under the North Sea.
The MIT authors also caution against any rush to select a single “winning” technology for carbon capture. Instead, they advocate that government and industry demonstrate capture for several alternative coal combustion and conversion technologies. They note that at present, integrated gasification combined cycle technology is the leading candidate for electricity production with CO2 capture. They say this status is based on an assumption that IGCC will have a lower cost than pulverized coal with capture. The researchers rightly point out, however, that neither IGCC nor any other coal technology has been successfully demonstrated with carbon capture and sequestration.
“There is no operational experience with carbon capture from coal plants and certainly not with an integrated sequestration operation,” the researchers write. “Given the technical uncertainty and the current absence of a carbon charge, there is no economic incentive for private firms to undertake such projects.”
The MIT group also suggests that the idea of pledging to retrofit an existing coal-fired plant to handle carbon capture implies a strategy that will require major future technical modifications. Retrofit will require a change to all power plant process conditions, which, in turn, implies making changes to turbines, heat rate, gas clean-up systems and other process units. Based on current estimates, they say the cost of retrofitting an IGCC plant for carbon capture appears to be cheaper than the retrofit cost for a supercritical pulverized coal plant.
A widely discussed option is to build “capture ready” features into new coal plants, regardless of the technology. The researchers conclude that such opportunities are actually limited and don’t extend much beyond leaving room in a plant’s footprint for retrofit equipment. They suggest that a cheaper strategy would be to build a lower capital cost plant without capture now, and later either pay the price placed on carbon emissions or invest to retrofit for carbon capture when it’s justified by a carbon price signal.
The researchers say that current priorities should focus on successful large-scale demonstration of the technical, economic and environmental performance of the technologies that allow for CO2 capture, transportation and storage. They express reservations with the DOE’s FutureGen project, citing what they say is a lack of clarity in the program’s research vs. development objectives.
Despite reservations such as these, the MIT researchers conclude that coal can provide energy at a cost of between $1 to $2 per MMBtu (compared to the $6 to $12 per MMBtu they calculate for oil and natural gas). Moreover, they point out that coal may be found in regions of the world other than the Persian Gulf and in abundant supply in the United States, India and China, all of which are major coal consumers.
In the carbon-constrained world that the MIT research team concludes is coming, they see carbon-free technologies such as nuclear and renewable energy as playing important roles. But absent some sort of technological breakthrough that the researchers admit they do not foresee, coal in “significant quantities” will remain “indispensable” as a fuel for electric generation. The report, available for download at http://web.mit.edu/coal, should be required reading.
Power Engineering April, 2007
Author(s) :
David Wagman
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