Features & Images » Feature Story

A climate change solution?

Beneath the Columbia River Basin, a real-life trial of the uncertain science of carbon sequestration – Part I

comment

By Valerie Brown

High Country News

An environmental engineer who favors the techie national uniform — Dockers and a light yellow Oxford shirt — Pete McGrail works out of a utilitarian office and lab, two among dozens of similar small rooms in the rabbit warren of cloyingly beige hallways at the Battelle campus in Richland, Wash. A global science and technology nonprofit, Battelle manages the Pacific Northwest National Laboratory at the Hanford Nuclear Reservation for the U.S. Department of Energy. In the post-Cold War era, the United States' national laboratories have stayed alive by shifting their focus to study technological and scientific issues outside the nuclear arena, including global warming.

McGrail is a clear-eyed man who speaks in the precisely worded sentences typical of scientists; he's careful to obey the strictures imposed on employees at defense installations (and increasingly, on everyone who works at a federal agency). At least one public information officer accompanies him to press interviews. No photos can show his security badge. And whether from natural reticence, scientific rigor, or administrative pressure, McGrail firmly repulses journalistic queries into taboo subjects such as the date and location of his upcoming field test of the transformative powers of... lava.

Actually, except for the details of his field test, McGrail is anything but close-mouthed when it comes to his research specialty, a type of volcanic rock known as flood basalt. In fact, he sings basalt's virtues at every opportunity — and the government has begun listening to his tune.

As 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 of 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 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.

Among the types of rock being investigated for carbon sequestration is McGrail's focus: flood basalt. 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 colours, 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. The Whistler area has several pockets of basalt columns. In Washington state, one of the best places to see large-scale columnar joining 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. Late in the 19th century, when early boosters like the Spokane newspaper and the railroads dubbed the area the "Inland Empire," the Columbia basalt area drew optimistic would-be farmers. Except for wheat, however, dryland farming was a bust. Not until the dams sprang up on the Columbia and large-scale irrigation became possible did farming expand in a big way.

The centre 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. Because the lava gushed out and spread horizontally, on a relief map the flood basalt region looks like it has been ironed out compared to the mountainous topography surrounding it.

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.

Today, Hanford is considered the most contaminated spot in North America, storing a variety of "legacy" nuclear wastes that are far from being completely contained and immobilized. And just across the Columbia River in Oregon lies the 20,000-acre Umatilla Army Depot, where the Defense Department is destroying millions of pounds of chemical weapons at a snail's pace.

For 60 years, these two blights have brooded over the region even as more life-affirming activities like farming and recreation have expanded. Today, the area's population centres on the Tri-Cities — Richland, Pasco and Kennewick — which cluster where the Columbia River, flowing down from the north and skirting nuclear wasteland, swallows the Snake and Yakima rivers before taking a sharp westward turn to become the border between Washington and Oregon.

Giant storage site

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.

Lava oozing out of a fissure can contain high volumes of trapped gas, such as sulfur dioxide and CO2. These gases will push toward the top of the flow to escape. As the lava begins to set, some of the gas is trapped in bubbles, which form the pores or vesicles that are the targets of CO2 injection. The more bubbles, the more surface area is available for the CO2 to make contact with basalt's minerals. The cylindrical cores McGrail 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.

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.

David Keith, a professor of chemical and petroleum engineering and economics at the University of Calgary, says bluntly, "I don't think (basalt) is that important. Saline (aquifer) capacity is gigantic. I think (basalt) doesn't matter for a long time. We're not going to run short for half a century even if we do this at a huge scale."

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 over 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.

ABOUT THE AUTHOR

Valerie Brown, a science writer and musician, lives near Portland, Oregon. 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 in September.

Add a comment