Mines and Geology study maps strategies for carbon sequestration

2/29/2008 - By: John Trent

As the country continues to explore ways to efficiently and safely capture carbon dioxide emissions from coal- and gas-fired power plants, a recently completed study by the Nevada Bureau of Mines and Geology has given the state of Nevada an important snapshot of the viability associated with this emerging technology.

According to Jon Price, director of the Nevada Bureau of Mines and Geology and state geologist, carbon dioxide sequestration in Nevada, though possible, could prove to be highly expensive for the state.

“When you look at some of the conventional approaches, there isn’t much potential,” Price said. “But when you look at unconventional approaches, yes, there is some potential in Nevada.”

Geological carbon dioxide sequestration is the technology of capturing carbon dioxide emissions from fossil-fuel burning industries, such as coal- or natural-gas fired power plants, and then storing the emissions, either underground or in rock.

Carbon dioxide sequestration techniques are used in oil-rich areas of the country, such as west Texas, where excess carbon dioxide is pumped into underground oil reservoirs. Price said the process also helps enhance oil production, as carbon dioxide dissolves and lubricates oil from rock, making it easier to retrieve.

For Nevada, the volume of oil that is produced within the state is far below oil-rich areas such as the Permian Basin of west Texas.

“We took a look at that opportunity in Nevada and concluded that there wasn’t much potential for using carbon dioxide for enhanced oil recovery,” Price said, noting that Nevada’s historic total of about 50 million barrels produced is far below the 7.5 billion barrels needed for the procedure to work for a large coal-fired power plant.

Another possibility was the sequestration of carbon dioxide in deep brine aquifers, a technique that is used in the Gulf Coast region of the United States. Due to differences in the geothermal gradient between the Gulf Coast and Nevada, as well as current State of Nevada water law, which prohibits injecting CO2 into aquifers, the team determined the technique could not be used effectively in Nevada.

A far more intriguing possibility for the state would be what Price called a more “unconventional” approach that would use basalt, which is found throughout most of the state, to create a chemical reaction between the rock and carbon dioxide. The process occurs naturally, Price said.

A typical power plant would need about 1.3 cubic kilometers of basalt in order to permanently lock up its produced carbon dioxide. The material produced from the reaction between basalt and carbon dioxide increases in volume by about 31 percent, Price said, which would fill the area that was originally mined – and create a small mountain on top of it.

Having basalt and carbon dioxide react underground is not a good idea, Price said. He noted that the 31 percent volume increase would not only fill every pore space it could find underground, there could also be potential for the carbon to escape through cracks, fissures or faults.

“So you’re really talking about mining the basalt in the first place, and then either trucking it to power plants or building power plants close by,” he said.

Price and his team found nine areas in the state where 5 cubic kilometers or more of basalt could be found. Locations included an area near Gerlach in northwestern Washoe County, another near Battle Mountain in the hills on either side of Interstate 80 East, an area that includes both Pershing and Churchill counties, as well as areas in southern Nevada.

“There is a lot of opportunity for reaction with C02 with basalt in Nevada,” Price said. “Sequestration by reaction with rocks will require considerably more research and development before it can be considered technologically feasible or cost effective.”

As Price noted, with any “unconventional” technology, comes a cost. He noted that, according to a study by the California Energy Commission, even conventional approaches to geological carbon sequestration could increase operating costs of coal-fired power plants by as much as 65 percent.

The reports, which were distributed last month to state energy policymakers, are available at the Nevada Bureau of Mines and Geology. Click on “Reports.” The documents are Reports 51 and 52 and Open-File Report 07-7.


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