Can Coal Ever Be Clean?

Coal provides 40 percent of the world’s electricity. It produces 39 percent of global CO₂ emissions. It kills thousands a year in mines, many more with polluted air.

Environmentalists say that clean coal is a myth. Of course it is: Just look at West Virginia, where whole Appalachian peaks have been knocked into valleys to get at the coal underneath and streams run orange with acidic water. Or look at downtown Beijing, where the air these days is often thicker than in an airport smoking lounge. Air pollution in China, much of it from burning coal, is blamed for more than a million premature deaths a year. That’s on top of the thousands who die in mining accidents, in China and elsewhere.

These problems aren’t new. In the late 17th century, when coal from Wales and Northumberland was lighting the first fires of the industrial revolution in Britain, the English writer John Evelyn was already complaining about the “stink and darknesse” of the smoke that wreathed London. Three centuries later, in December 1952, a thick layer of coal-laden smog descended on London and lingered for a long weekend, provoking an epidemic of respiratory ailments that killed as many as 12,000 people in the ensuing months. American cities endured their own traumas. On an October weekend in 1948, in the small Pennsylvania town of Donora, spectators at a high school football game realized they could see neither players nor ball: Smog from a nearby coal-fired zinc smelter was obscuring the field. In the days that followed, 20 people died, and 6,000 people—nearly half the town—were sickened.

Coal, to use the economists’ euphemism, is fraught with “externalities”—the heavy costs it imposes on society. It’s the dirtiest, most lethal energy source we have. But by most measures it’s also the cheapest, and we depend on it. So the big question today isn’t whether coal can ever be “clean.” It can’t. It’s whether coal can ever be clean enough—to prevent not only local disasters but also a radical change in global climate.

Last June, on a hot and muggy day in Washington, D.C., President Barack Obama gave the climate speech that the American coal and electric power industries had dreaded—and environmentalists had hoped for—since his first inauguration, in 2009. Speaking in his shirt-sleeves and pausing occasionally to mop his brow, Obama announced that by June 2014 the Environmental Protection Agency (EPA) would draft new rules that would “put an end to the limitless dumping of carbon pollution from our power plants.” The rules would be issued under the Clean Air Act, a law inspired in part by the disaster in Donora. That law has already been used to dramatically reduce the emission of sulfur dioxide, nitrogen oxides, and soot particles from American power plants. But carbon dioxide, the main cause of global warming, is a problem on an entirely different scale.

In 2012 the world emitted a record 34.5 billion metric tons of carbon dioxide from fossil fuels. Coal was the largest contributor. Cheap natural gas has lately reduced the demand for coal in the U.S., but everywhere else, especially in China, demand is surging. During the next two decades several hundred million people worldwide will get electricity for the first time, and if current trends continue, most will use power produced by coal. Even the most aggressive push for alternative energy sources and conservation could not replace coal—at least not right away.

How fast the Arctic melts, how high the seas rise, how hot the heat waves get—all these elements of our uncertain future depend on what the world does with its coal, and in particular on what the U.S. and China do. Will we continue to burn it and dump the carbon into the air unabated? Or will we find a way to capture carbon, as we do sulfur and nitrogen from fossil fuels, and store it underground?

“We need to push as hard as we can for renewable energy and energy efficiency, and on reducing carbon emissions from coal,” says Stanford University researcher Sally Benson, who specializes in carbon storage. “We’re going to need lots of ‘ands’—this isn’t a time to be focusing on ‘ors.’ ” The carbon problem is just too big.

American Electric Power’s Mountaineer Plant, on the Ohio River in New Haven, West Virginia, inhales a million pounds of Appalachian coal every hour. The coal arrives fresh from the ground, on barges or on a conveyor belt from a mine across the road. Once inside the plant, the golf-ball-size lumps are ground into dust as fine as face powder, then blown into the firebox of one of the largest boilers in the world—a steel box that could easily swallow the Statue of Liberty. The plant’s three steam-powered turbines, painted blue with white stars, supply electricity round the clock to 1.3 million customers in seven states. Those customers pay about a dime per kilowatt-hour, or roughly $113 a month, to power the refrigerators, washers, dryers, flat screens, and smartphones, to say nothing of the lights, of an average household. And as Charlie Powell, Mountaineer’s plant manager, often said, even environmentalists like to keep the lights on.

The customers pay not a cent, however, nor does American Electric Power (AEP), for the privilege of spewing six to seven million metric tons of carbon dioxide into the atmosphere every year from Mountaineer’s thousand-foot-high stack. And that’s the problem. Carbon is dumped without limit because in most places it costs nothing to do so and because there is, as yet, no law against it in the U.S. But in 2009 it looked as if there might soon be a law; the House of Representatives had already passed a bill that summer. AEP, to its credit, decided to get ahead of it.

That October, Mountaineer began a pioneering experiment in carbon capture. Powell oversaw it. His father had worked for three decades at a coal-fired power plant in Virginia; Powell himself had spent his career at Mountaineer. The job was simple, he said: “We burn coal, make steam, and run turbines.” During the experiment, though, it got a bit more complicated. AEP attached a chemical plant to the back of its power plant. It chilled about 1.5 percent of Mountaineer’s smoke and diverted it through a solution of ammonium carbonate

The system worked. Over the next two years AEP captured and stored more than 37,000 metric tons of pure carbon dioxide. The CO₂ is still underground, not in the atmosphere. It was only a quarter of one percent of the gas coming out the stack, but that was supposed to be just the beginning. AEP planned to scale up the project to capture a quarter of the plant’s emissions, or 1.5 million tons of CO₂ a year. The company had agreed to invest $334 million, and the U.S. Department of Energy (DOE) had agreed to match that. But the deal depended on AEP being able to recoup its investment. And after climate change legislation collapsed in the Senate, state utility regulators told the company that it could not charge its customers for a technology not yet required by law.

In the spring of 2011 AEP ended the project. The maze of pipes and pumps and tanks was dismantled. Though small, the Mountaineer system had been the world’s first to capture and store carbon dioxide directly from a coal-fired electric plant, and it had attracted hundreds of curious visitors from around the world, including China and India. “The process did work, and we educated a lot of people,” said Powell. “But geez-oh-whiz—it’s going to take another breakthrough to make it worth our while.” A regulatory breakthrough above all—such as the one Obama promised last summer—but technical ones would help too.

Capturing carbon dioxide and storing or “sequestering” it underground in porous rock formations sounds to its critics like a techno-fix fantasy. But DOE has spent some $6.5 billion over the past three decades researching and testing the technology. And for more than four decades the oil industry has been injecting compressed carbon dioxide into depleted oil fields, using it to coax trapped oil to the surface. On the Canadian Great Plains this practice has been turned into one of the world’s largest underground carbon-storage operations.

Since 2000 more than 20 million metric tons of carbon dioxide have been captured from a North Dakota plant that turns coal into synthetic natural gas, then piped 200 miles north into Saskatchewan. There the Canadian petroleum company Cenovus Energy pushes the CO₂ deep into the Weyburn and Midale fields, a sprawling oil patch that had its heyday in the 1960s. Two to three barrels of oil are dissolved out of the reservoir rock by each ton of CO₂, which is then reinjected into the reservoir for storage. There it sits, nearly a mile underground, trapped under impermeable layers of shale and salt.

For how long? Some natural deposits of carbon dioxide have been in place for millions of years—in fact the CO₂ in some has been mined and sold to oil companies. But large and sudden releases of CO₂ can be lethal to people and animals, particularly when the gas collects and concentrates in a confined space. So far no major leaks have been documented at Weyburn, which is being monitored by the International Energy Agency, or at any of the handful of other large storage sites around the world. Scientists consider the risk of a catastrophic leak to be extremely low.

They worry more about smaller, chronic leaks that would defeat the purpose of the enterprise. Geophysicists Mark Zoback and Steven Gorelick of Stanford University argue that at sites where the rock is brittle and faulted—most sites, in their view—the injection of carbon dioxide might trigger small earthquakes that, even if otherwise harmless, might crack the overlying shale and allow CO₂ to leak. Zoback and Gorelick consider carbon storage “an extremely expensive and risky strategy.” But even they agree that carbon can be stored effectively at some sites—such as the Sleipner gas field in the North Sea, where for the past 17 years the Norwegian oil company Statoil has been injecting about a million tons of CO₂ a year into a brine-saturated sandstone layer half a mile below the seabed. That formation has so much room that all that CO₂ hasn’t increased its internal pressure, and there’s been no sign of quakes or leaks.

At a coal-fired power plant the situation is different. The CO₂ is part of a complex swirl of stack gases, and the power company has no financial incentive to capture it. As the engineers at Mountaineer learned, capture is the most expensive part of any capture-and-storage project. At Mountaineer the CO₂ absorption system was the size of a ten-story apartment building and occupied 14 acres—and that was just to capture a tiny fraction of the plant’s carbon emissions. The absorbent had to be heated to release the CO₂, which then had to be highly compressed for storage. These energy-intensive steps create what engineers call a “parasitic load,” one that could eat up as much as 30 percent of the total energy output of a coal plant that was capturing all its carbon.

One way to reduce that costly loss is to gasify the coal before burning it. Gasification can make power generation more efficient and allows the carbon dioxide to be separated more easily and cheaply. A new power plant being built in Kemper County, Mississippi, which was designed with carbon capture in mind, will gasify its coal.

Existing plants, which are generally designed to burn pulverized coal, require a different approach. One idea is to burn the coal in pure oxygen instead of air. That produces a simpler flue gas from which it’s easier to pull the CO₂. At the DOE’s National Energy Technology Laboratory in Morgantown, West Virginia, researcher Geo Richards is working on an advanced version of this scheme.

“Come and see our new toy,” he says, hunching his shoulders against a bitter Appalachian winter day and walking briskly toward a large white warehouse. Inside, workers are assembling a five-story scaffold for an experiment in “chemical looping.” Making pure oxygen from air, Richards explains, is costly in itself—so his process uses a metal such as iron to grab oxygen out of the air and deliver it to the coal fire. In principle, chemical looping could radically cut the cost of capturing carbon.

Richards has dedicated more than 25 years of his career to making carbon capture more efficient, and for him the work is largely its own reward. “I’m one of those geeky people who just like seeing basic physics turned into technology,” he says. But after decades of watching politicians and the public tussle over whether climate change is even a problem, he does sometimes wonder if the solution he’s been working on will ever be put to practical use. His experimental carbon-capture system is a tiny fraction of the size that would be required at a real power plant. “In this business,” Richards says, “you have to be an optimist.”

Last fall, as world coal consumption and world carbon emissions were headed for new records, the Intergovernmental Panel on Climate Change (IPCC) issued its latest report. For the first time it estimated an emissions budget for the planet—the total amount of carbon we can release if we don’t want the temperature rise to exceed 2 degrees Celsius (3.6 degrees Fahrenheit), a level many scientists consider a threshold of serious harm. The count started in the 19th century, when the industrial revolution spread. The IPCC concluded that we’ve already emitted more than half our carbon budget. On our current path, we’ll emit the rest in less than 30 years.

Changing that course with carbon capture would take a massive effort. To capture and store just a tenth of the world’s current emissions would require pumping about the same volume of CO₂ underground as the volume of oil we’re now extracting. It would take a lot of pipelines and injection wells. But achieving the same result by replacing coal with zero-emission solar panels would require covering an area almost as big as New Jersey (nearly 8,000 square miles). The solutions are huge because the problem is—and we need them all.

“If we were talking about a problem that could be solved by a 5 or 10 percent reduction in greenhouse gas emissions, we wouldn’t be talking about carbon capture and storage,” says Edward Rubin of Carnegie Mellon University. “But what we’re talking about is reducing global emissions by roughly 80 percent in the next 30 or 40 years.” Carbon capture has the potential to deliver big emissions cuts quickly: Capturing the CO₂ from a single thousand-megawatt coal plant, for example, would be equivalent to 2.8 million people trading in pickups for Priuses.

The first American power plant designed to capture carbon is scheduled to open at the end of this year. The Kemper County coal-gasification plant in eastern Mississippi will capture more than half its CO₂ emissions and pipe them to nearby oil fields. The project, which is supported in part by a DOE grant, has been plagued with cost overruns and opposition from both environmentalists and government-spending hawks. But Mississippi Power, a division of Southern Company, has pledged to persist. Company leaders say the plant’s use of lignite, a low-grade coal that’s plentiful in Mississippi, along with a ready market for its CO₂, will help offset the heavy cost of pioneering new technology.

The technology won’t spread, however, until governments require it, either by imposing a price on carbon or by regulating emissions directly. “Regulation is what carbon capture needs to get going,” says James Dooley, a researcher at DOE’s Pacific Northwest National Laboratory. If the EPA delivers this year on President Obama’s promise to regulate carbon emissions from both existing and new power plants—and if those rules survive court challenges—then carbon capture will get that long-awaited boost.

China, meanwhile, has begun regional experiments with a more market-friendly approach—one that was pioneered in the U.S. In the 1990s the EPA used the Clean Air Act to impose a cap on total emissions of sulfur dioxide from power plants, allocating tradable pollution permits to individual polluters. At the time, the power industry predicted disastrous economic consequences. Instead the scheme produced innovative, progressively cheaper technologies and significantly cleaner air. Rubin says that carbon-capture systems are at much the same stage that sulfur dioxide systems were in the 1980s. Once emissions limits create a market for them, their cost too could fall dramatically.

If that happens, coal still wouldn’t be clean—but it would be much cleaner than it is today. And the planet would be cooler than it will be if we keep burning coal the dirty old way.

Source: National Geographic

http://ngm.nationalgeographic.com/2014/04/coal/nijhuis-text

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