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The briny water has to be removed to make room for the liquid CO2, and cleaning the salts and dissolved minerals from the water was one of the largest hurdles to providing a viable CO2 storage facility.
“Now, with the potential of lithium, we can turn that whole thing into a profit center,´ said CMI director Ron Surdam, adding that the brine “becomes an asset instead of a deficit.”
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The best-case scenario is that the entire 2,000-square-mile Rock Springs Uplift could contain up to 18 million tons of lithium: equivalent to about 720 years of current global lithium production. The discovery could have a major impact on the global market, transforming the United States from a significant lithium importer to an independent lithium producer.
Lithium – a key ingredient in batteries – is in short supply in the United States. At present there is only one other lithium mine in the nation, and it can only produce about 30 percent of current domestic demand. Reserves at Rockwood Lithium in Silver Peak, Nev., are estimated to be 118,000 tons in a 20-square-mile area. Preliminary research suggests that a comparable 25-square-mile area of the Rock Springs Uplift could contain 228,000 tons of lithium.
With worldwide demand for lithium increasing at about 10 percent each year, according to U.S. Geologic Survey estimates, lithium mining could be a viable new industry in the region.
In addition, the production of lithium will help pay for a major cost of CO2 storage: treatment of the briny water that must be removed from the uplift to make room for the liquid CO2.
“Due to their high salinity, brines from the CO2 storage reservoirs would have to be pumped to the surface and treated – often an expensive process,´ said Scott Quillinan, CMI’s senior hydrogeologist. “Recovering and marketing lithium from the brines would produce significant revenue to offset the cost of brine production, treatment and CO2 storage operations.”
There are other benefits as well.
“Although other researchers have evaluated the economic potential of producing metals and salts from saline oilfield brines, incorporating lithium production into the CO2 storage process is a new concept,” Surdam said. “Several factors make southwest Wyoming ideal for testing this process.”
The lithium was discovered in brine removed from a test well during Wyoming Carbon Underground Storage Project research. On a commercial scale, CO2 capture and underground storage is the emission-reduction technology of choice since it allows industrialization and environmental quality to coexist.
CUSP began in 2010 as a jointly financed project between the federal Department of Energy and the University of Wyoming.
“There is no question that, if we’re going to utilize our coal resources, we need to capture the CO2 and store it in the subsurface,” Surdam said. “We were out looking for the best place in Wyoming to do that.”
CUSP will wrap up in December, but another joint project with the DOE looking at the confining rock layers to make sure there is permanence in CO2 storage has just begun and will continue for another three years, Surdam said.
The Rock Springs Uplift is a collection of geologic features (including Madison limestone and Weber/Tensleep sandstone) that provide a cap to a vast underground storage space. Currently that space is awash in hot, pressurized brine.
“The brine is three times as salty as seawater,” Surdam said. “Since we’re in the Colorado River drainage, just putting the brine in an evaporative pond and storing the salts in a landfill wasn’t going to work. The best way is to bring it to the surface, remove the lithium and most of the water. The small amount of slurry left would be re-injected.”
Surdam said Quillinan has designed a facility that can handle the extractive process. Quillinan also will be meeting with scientists at the Lawrence Livermore National Laboratory in Berkeley, Calif., in the near future. “They are the world’s experts on treating brine,” he said. “We want to set this up on a (laboratory) bench setting.”
“In addition to lithium, the brines contain other recoverable, economically valuable metals and salts,” added Fred McLaughlin, CMI’s senior petrologist. “Also, the treated water resulting from the recovery process could benefit local communities, agriculture and industry.”
Brines from the Rock Springs Uplift are ideally suited for the multi-step extraction process. The heat that comes up with the brine will be run though a heat exchanger to make electricity to run the plant. Because the brine already is pressurized, one of the big costs of desalination – pressurization – already is taken care of.
The next step, reverse osmosis, will produce potable water and concentrated brine. Magnesium needs to be removed from the brine before the lithium can be extracted. Fortunately, the brines from the Rock Springs Uplift reservoirs contain much less magnesium than brines at existing, currently profitable lithium mining operations.
The lithium-containing brine will then be mixed with sodium carbonate (soda ash, also known as trona) to precipitate the lithium as lithium carbonate. Importing the soda ash is a large expense for most lithium producers.
Luckily, the world’s largest naturally occurring soda ash deposit is less than 40 miles from the Rock Springs Uplift, so transportation costs would be minimal.
“We’re excited about this discovery,´ said Shanna Dahl, CMI deputy director. “More work must be done to fully assess the potential, but our research is very encouraging at this point.”