A Rock-Solid Solution?

by VALERIE BROWN & r & & r & & lt;span class= & quot;dropcap & quot; & A & lt;/span & s the reality of global warming sinks in, more and more people are hoping against hope for a Miracle Cure, a way to avert global catastrophe by reducing or stabilizing the amount of carbon dioxide in the atmosphere. Owing to the huge combined inertia of major energy interests and the U.S. government and the absence of clear-cut energy alternatives in the public mind, so far there's been little movement toward reducing fossil-fuel use. But the federal government is encouraging efforts to develop technologies that can capture and contain CO2 emissions before they reach the atmosphere.





Carbon sequestration, as it has come to be known, has one primary attraction: It could enable the U.S. to keep using its most abundant (but until now dirtiest) fossil fuel -- coal. Some sequestration may be accomplished by growing or preserving forests and other plant-heavy ecosystems that take up carbon dioxide by respiration. But a big part of the sequestration scenario involves stripping CO2 from power plant exhaust and injecting it into natural underground reservoirs and rock formations.





Research in Richland


Pete McGrail is right in the middle of the carbon sequestration quest. McGrail is an environmental engineer at Richland, Wash.-based Battelle, which manages the Pacific Northwest National Laboratory at the Hanford Nuclear Reservation for the U.S. Department of Energy. His research specialty is a type of volcanic rock known as flood basalt, which has potential for carbon sequestration.





Most sequestration experts think basalt sequestration a rather quirky, even quixotic idea. After all, most of the country lacks the layered volcanic flows that spread to form the Columbia and Snake River plains. But basalt has one virtue that other geologic formations lack. In the laboratory, it can transform CO2 into calcium carbonate -- the equivalent of seashells or limestone -- in a matter of weeks or months, effectively immobilizing carbon in a solid. And because most of the Pacific Northwest is awash in basalt, carbon sequestration of this type could be an excellent regional method of reducing carbon dioxide emissions -- if what happens in the lab can be made to happen 3,000 feet below the Columbia River Basin.





Basalt is a majestic rock, a deep black when young that gradually weathers into softer colors, especially the telltale reds that show where iron in the stone has reacted with oxygen. Depending on how it cools, basalt sometimes forms huge or tiny vertical columns -- Wyoming's Devils Tower and the Giant's Causeway in Northern Ireland are prominent examples of the big versions. In the Northwest, one of the best places to see large-scale basalt columns is in the Columbia River Gorge 200 miles west of Richland, where massive columns rear above Interstate 84 as it snakes alongside the river. In the rain-drenched climate west of the Cascades, the stately columns are graced with conifers and ferns, waterfalls and rockslides that are very different from the drab flats and tortured hills in the heart of the Columbia basalt to the east. As they erode and break down, volcanic rocks form rich soils abundant in minerals.





The center of McGrail's interest lies in this area and in the Columbia River Basalt Group, which consists of about 300 lava flows that ran fast and often in the Miocene epoch between 6 million and 17 million years ago. It covers about 65,000 square miles, in places to a depth of three miles; some of the crustal rifts disgorging the basalt were as much as 100 miles long.





Of the world's major continental flood basalts, the Columbia group is the youngest and smallest. (The much larger Deccan traps in west-central India erupted about the time the dinosaurs disappeared 65 million years ago, and the even vaster Siberian traps surged out nearly 250 million years ago at the end of the Permian period. The Siberian traps are too remote from large sources of CO2 emissions to be widely considered a candidate for sequestration, but India is intensely interested in the potential of the Deccan traps.) The Columbia basalt's surface landscape is classic Western sagebrush desert, which, unmodified by paved roads, irrigation or air conditioning, appears to be a trackless, inhospitable and worthless wasteland, good for nothing but possibly grazing sheep. The federal government viewed it as a handy spot to conduct dangerous experiments and dispose of nasty wastes, building the Hanford Nuclear Reservation just northwest of Richland to manufacture plutonium during World War II.





At one point, the Department of Energy considered injecting its millions of gallons of liquid nuclear waste deep into the Columbia basalt. During the search for an appropriate injection site, hundreds of core samples were drilled and archived. Those core samples have come in very handy for Pete McGrail as he conducts studies that may lead to another industrial use for an already hard-used land.





Regardless of geology, proper carbon sequestration requires a chamber or system of interconnected pores to accept an infusion of carbon dioxide, as well as a competent caprock above it, to keep the CO2 from escaping. Spent oil and gas formations and saline aquifers contained in sedimentary rock have usually been considered the most likely candidates for geosequestration; experts frequently point out that oil and gas have been safely held for millions of years in such formations.





The Columbia basalt is volcanic, rather than sedimentary, rock. But based on the Energy Department's core samples of the area and other research, McGrail believes the Columbia group has real sequestration potential. The cylindrical cores he has studied are about three inches in diameter and clearly show the boundaries between lava flows, interrupted periodically by thinner, small-grained layers from non-eruptive periods, when windblown soil, volcanic ash, and other materials drifted across the landscape. Because the Columbia basalt is made up of many separate flows, it has numerous alternating porous and dense layers. McGrail thinks the former can absorb and transform large amounts of CO2 and the latter can serve as an effective caprock, aided by the occasional sedimentary layer that lies in between.





CO2 and basalt have attributes whose combination could be a marriage made in heaven. At depths below around 3,000 feet, CO2 becomes supercritical -- that is, it turns into a liquid slightly less dense and much runnier than water. Injection pressure and the weight of the earth above it will force the CO2 to dissolve in groundwater residing in aquifers and distributed throughout the small cracks and holes in porous sections of basalt. As anyone familiar with Perrier can attest, dissolved CO2 makes water fizzy; this sparkling, mildly acidic "pore water" reacts with minerals in the basalt, principally calcium, and eventually breaks up CO2 molecules, sequestering their carbon in solid deposits of calcium carbonate, also known as limestone. Over long time periods, further reactions convert the available elements into even more stable types of rock, such as olivine.





Peer Review


When McGrail first started working on basalt sequestration, he thought it a wacky idea. Experience has since changed his mind, but other experts still question the details.





George Peridas, a science fellow with the Natural Resources Defense Council, supports geosequestration in general, saying that "with rigorous regulatory controls, we are confident that sequestration can work very well without endangering health or the environment." He thinks McGrail's research worthwhile, although he's not ready to treat it as "a high confidence scenario." Peridas is concerned that the columnar joins and other crack networks that allow CO2 to travel into porous areas of the basalt will also allow it to come back out. Monitoring may also be a problem. For example, Peridas says, when seismic signals are used to determine underground structures, "in the data you get back it's hard to distinguish between the CO2 and the rock itself."





Nick Riley, a geosequestration researcher for the British Geological Survey, says, "My take on this is that the (chemical) reactions are too slow. I also think it will be difficult to get the rock to receive the CO2 at the rates required."





But McGrail has reason to differ. In unpublished lab experiments currently being prepared for peer review, McGrail and his team put small amounts of basalt into a vessel with CO2, heating and pressurizing the samples to levels representing conditions deep underground. The carbonate minerals, he says, formed in "weeks to months." "We really did not expect this," McGrail says. "It was pretty close to serendipity."





Such rapid transformation is orders of magnitude faster than the rate of similar reactions in sedimentary rocks, which can take tens to thousands of years to fix injected carbon dioxide into solids. Since the trick is to keep the liquid CO2 buried long enough for the chain of chemical reactions to immobilize it, basalt's processing speed is one of its strongest assets in the carbon sequestration race.





A 2005 Intergovernmental Panel on Climate Change report on geosequestration estimates that the world's deep saline formations could handle more than a trillion tons of CO2. The Columbia basalt, however, may only be able to absorb a hundred billion tons, and McGrail has an even more conservative estimate of 20-50 billion tons. Fossil fuel emissions are putting about 26 billion tons of CO2 into the atmosphere every year, and the figure is rising. So if the Columbia basalt were the planet's sole repository of captured CO2, it would likely fill up in a couple of years.





Still, McGrail points out, the Columbia basalt could hold centuries' worth of the CO2 produced in the region. The Northwest's long dependence on hydropower has made it a minor source of greenhouse gases so far. But the area's power mix is likely to change as population and power demand grow, and the region may have to one day rely on basalt sequestration, because it has relatively few saline aquifers or spent gas and oil wells for CO2 storage.





McGrail's work is part of the Big Sky Carbon Sequestration Partnership, a consortium led by Montana State University and drawing on researchers from all three of Idaho's universities, the U.S. Department of Energy's Idaho National Laboratory near Idaho Falls, and Battelle. The DOE and several private companies have given $17.9 million to the Big Sky partnership, which covers the eastern halves of Washington and Oregon, Idaho, Montana, Wyoming and South Dakota and is one of six regional programs covering the whole country.





A map of the entire Big Sky region shows only 21 major industrial sources of CO2 within the Columbia basalt. But the area is surrounded by more than 100 major sources. And because the economics of energy and sequestration discourage long-range transport of CO2, the Columbia Plain may wind up hosting many new coal-fired power plants, sited there specifically to be close to sequestration opportunities. Once again, it seems, the Northwest's massive intermountain desert may become the waste receptacle for interests beyond its borders. On the other hand, assuming the unintended consequences of basalt sequestration remain minor, the region is likely to benefit from the resulting jobs and economic growth.





But we're a long way from knowing how CO2 will behave in actual basalt formations, a state of ignorance that will be reduced by the outcome of McGrail's field test.





Obstacles to Overcome


The search for a solution to the climate crisis demonstrates that we need to know a lot more about what lies beneath us. Perhaps ironically, the deepest such knowledge resides in the fossil fuel industries themselves, which for many years have injected CO2 routinely into oil and gas wells to push hydrocarbons to the surface. Doing this, however, has not necessarily required the CO2 to stay buried for the lengths of time required to slow the greenhouse effect. The Department of Energy's 2006 Carbon Sequestration Roadmap sets a goal of less than a 1 percent escape after 100 years. An earlier escape would nullify the benefits of the sequestered CO2, not to mention that CO2 would be emitted during the process of injection, McGrail says.





Although generally considered nontoxic, CO2 can harm vegetation and subsurface organisms. Soil organisms are adapted to the naturally higher CO2 content of their environment, but they can be killed by higher-than-normal concentrations. In large volumes, of course, CO2 can be lethal to large organisms, too. In 1986, a massive natural CO2 release from the bottom of Lake Nyos in Cameroon suffocated about 1,800 people.





Explosive releases of CO2 from sequestration sites are highly unlikely, provided the target formation is properly characterized and monitored, George Peridas says. The main concern is that leaks would return CO2 to the atmosphere, reversing the benefits of the process.





Another worry about injecting CO2 involves the contamination of shallow groundwater used for drinking and irrigation. The very mineral leaching that is desirable for sequestering CO2 deep underground would make drinking water unpalatable, so it's imperative to determine the risk of communication between aquifers of different character. Most injection will be into deep aquifers that are already too brackish or saline for human use due to eons of chemical reactions with the rocks. But if underground equilibrium is disturbed, pressure from injected CO2 could cause undrinkable, salty aquifers to contaminate groundwater consumed by humans.





And earthquakes may also pose problems: The increased pressure of intruding CO2 on rock formations can trigger an earthquake, or a natural earthquake could enlarge existing cracks and faults or create new ones in sequestration zones. Most geosequestration researchers, including McGrail, consider earthquakes a minor risk in the Columbia basalt. But there have been instances of induced quakes elsewhere. In the 1960s, the U.S. Army injected about 165 million gallons of liquid toxic waste from munitions manufacture into a formation under the Denver basin. From 1962 to 1967, there were some 1,500 seismic "events" centered on the injection area, including three earthquakes at or above Richter magnitude 5.





As to natural seismicity, McGrail says, extensive monitoring at Hanford shows that most earthquakes in the region are weak, sparse and random. The Columbia basalt is a few hundred miles from the complex subduction zone along the Pacific Coast, where the North American plate, the Juan de Fuca plate and the Pacific plate are sumo wrestling. Dirk Dunning, an environmental engineer with the Oregon Department of Energy who is involved with Hanford safety issues, says when that zone experiences its next magnitude 9 earthquake -- due any time -- the Hanford area would be rattled by a "5-plus" shock. It's not clear what effect this would have on the Columbia basalt.





McGrail's confidence in the safety of basalt sequestration has been strengthened by tests showing that air and water have remained trapped in basalt pores for millions of years without mixing between formations. McGrail says this is good evidence that the basalt has been "undisrupted by seismicity," and that the injected CO2 will not migrate out of its target formation.


Still, many environmentalists are concerned about potential side effects. They are even more worried about other aspects of carbon sequestration.





"If (sequestration) were a simple solution to a complicated problem," says Sierra Club spokesman Josh Dorner, "people would already be using it." Still, he says, "we would love it if it turned out to work." The Sierra Club opposes new coal-fired power plants unless they sequester 100 percent of their emissions, Dorner says.





"It will take so much time to test it," Friends of the Earth spokesman Nick Berning notes. "There's an urgency about addressing global warming that demands that we take steps that can make a difference now, moving to cleaner energy, wind, solar, and conservation. We know wind power can generate energy with zero carbon emissions. We know solar can."





Regardless of any given site's geology, nobody knows how well the earth's crust will tolerate being saturated with CO2 in the volumes necessary to slow global warming. For his part, McGrail stresses that many basic questions must be satisfactorily answered before any large-scale CO2 sequestration in basalt can begin. His data, he says, "are compelling, but I would not regard it as sufficient proof of analogous isolation for CO2 storage until we have some field data to support it."





Time for a Test Run


In late June, the site of McGrail's sequestration field test was finally revealed: Wallula, Wash., a few miles south of the Tri-Cities on the east bank of the Columbia River just below its confluence with the Snake and Yakima rivers. McGrail's team will inject 3,000 tons of CO2 into the Grande Ronde formation of the Columbia basalt at a depth of 3,000 feet or more.





The site, an industrial park, has easy access to hydropower, rail lines and the Columbia River. Energy producers have taken notice: A new Gig Harbor, Washington-based energy consortium called the Wallula Energy Resource Center has announced plans to build a $2 billion state-of-the-art power plant near the test site. It would be an integrated gasification combined cycle coal-fired power plant with 600-700 megawatts of capacity. The power plant would use McGrail's test site to sequester 65 percent of its CO2. If the Byzantine energy-facility permitting process goes well, the plant could be operating by 2013.





Some Washington environmental organizations share the doubts of the national groups about the "clean coal" scenario. Sequestration is "unproven, it's expensive, and it's going to add some costs and risks for Washington utilities and residents," says Paul Horton, executive director of Climate Solutions, an Olympia, Washington-based nonprofit. "We'd rather enable other kinds of investments, a smarter way of using energy."





Indeed, any successful geosequestration technology risks enabling a continued reliance on fossil fuels, even though most experts agree that climate change requires action on many fronts, including a reduction in the use of hydrocarbons. If geosequestration works, keeping the good news from seeming like a panacea will be difficult. Some cynics even suspect that coal interests will promise sequestration to get their permits -- and then renege after the plants are built, claiming it would be too costly.





Horton, however, thinks that in the near future Washington state's new regulations and federal climate policies will bring "legal limits and caps." These new guidelines will change the price of power, making renewables and energy efficiency much more competitive. "The rules of the game change at that point," he says.





But even if it works perfectly, CO2 sequestration of any sort won't be the Holy Grail of global warming; McGrail stresses that all the other options have to be employed as well, from energy conservation to alternative energy sources. Geosequestration, he says, is just "the linchpin that finally gets us to stable (atmospheric) CO2."





It will take about three years to get an idea of how well McGrail's lab tests and calculations have predicted the behavior of CO2 in basalt under real-world conditions. If things go well, perhaps basalt's poor-relation status will change, and its main champion will go down in history as the "Holy McGrail" of carbon sequestration.





Valerie Brown, a science writer and musician, lives near Portland, Ore. She grew up on Idaho's Snake River flood basalt; her grandfather ran sheep on Oregon's Columbia River basalt in the early 20th century; and her geologist father intensely studied gabbro, a close relative of basalt, in a formation on the Oregon-Idaho border. This story first appeared in High Country News (www.hcn.org).