A New Effort to Capture Coal's Dirty Breath & Bury It Underground

An experimental power plant in New Jersey could give the coal an attractive (and lucrative) makeover—if the technology, policy, and economics come together.

By Michael Lemonick|Monday, November 29, 2010
RELATED TAGS: ALTERNATIVE ENERGY
coalmedia
coalmedia
photography by Nicholas Eveleigh

Daniel Schrag gets visitors all the time—graduate students in despair over their dissertations, fellow faculty members dropping by to chat about the Cretaceous sulfur cycle or some equally abstruse topic, or visiting scientists collaborating with him on one of the scores of scholarly papers he has churned out in a career that has earned him a professorship in Harvard’s department of earth and planetary sciences and a MacArthur genius grant.

The two men who stopped by his office one afternoon three years ago were not interested in professorial chitchat, however. Frank Smith and Jim Croyle are hard-nosed businessmen, and they wanted Schrag’s advice on a major investment. Smith and Croyle are cofounders of SCS Energy, a power plant development company in nearby Concord, Massachusetts, and they were planning to spend 5 billion dollars on a radical new type of coal-based power plant called PurGen One. Burning coal accounts for about 40 percent of all carbon emissions worldwide, but this plant would emit essentially no carbon at all. Smith and Croyle had read some of Schrag’s papers about carbon capture and sequestration, or CCS—a technique for keeping globe-warming carbon dioxide out of the air by burying it—and they were ready to put it into action. “I was kind of surprised,” Schrag admits. “I told them, ‘I’d love it if you’d sequester carbon. But how would you make money?’”

Coal is plentiful around the world, especially in three of the most energy-intensive economies: the United States, India, and China. It would be tough to abandon it entirely. On the other hand, capturing the carbon from a coal-burning plant and pumping it underground is expensive. Such “clean coal” technology could cost 50 percent more than regular, dirty coal-generated power, wiping out much of the black rock’s economic appeal. Schrag politely brought up all the reasons why CCS might never be commercially viable, but Croyle and Smith just kept talking. They didn’t seem to care how much money it took to get started. “They knew the project depended on making a profit,” Schrag says, “and they thought they had figured out the way to do it.”

As the two investors explained their plan, Schrag grew increasingly excited: They had come up with a breakthrough in clean-coal power generation that just might work. PurGen would transform raw coal into cleaner-burning hydrogen and fire its generators with that instead, in a process that would also yield valuable by-products. Croyle and Smith already had a few potential sites in mind (they later decided on a heavily industrial section of Linden, New Jersey), and they were convinced they could have their plant up and running by 2016, largely by using off-the-shelf technology. The project could mark the beginning of a transformation in the way we produce electricity. We could drastically cut back on human-generated carbon emissions without giving up on an energy source that could last us a century or more.

If all Croyle and Smith had to offer was the idea of turning coal into hydrogen, Schrag would not have been impressed. The basic technology for turning coal into other fuels, known as gasification, has been around since the 1920s. During South Africa’s apartheid period, for example, the country could not import oil, so it gasified locally abundant coal to make gasoline. Creating hydrogen requires merely tweaking the process. To do so, explains PurGen project manager Tim Bauer, coal is ground up and heated under pressure in the presence of oxygen. The right mix of heat, pressure, and chemistry keeps the coal from burning; instead, it undergoes a series of reactions that give rise to a mix of gases, including hydrogen, carbon monoxide, nitrogen, and sulfur dioxide. The solids left over at the end are recycled back into the pressure vessel, where more gases are extracted until all that is left are “clinkers”—inert, glassy cinders that can be added to concrete to strengthen it. The gases, meanwhile, are combined with steam, which changes the carbon monoxide to carbon dioxide that can be extracted, liquefied, and buried.

Processing coal this way is substantially more complicated than burning it whole, which is why Schrag initially assumed that SCS Energy’s plan would be a money loser. “Even regular coal-fired power plants are generally terrible investments,” Bauer says. They cost billions of dollars to build but make money only part of the time. During the day, when people are using computers, appliances, electric machinery, and so on, the plants can sell all the power they can churn out. At night, though, demand goes way down—especially in winter, when air conditioners are turned off.

Here is where the cleverness that sparked Schrag’s interest comes in. At an estimated $5.2 billion to construct, PurGen will be twice as expensive as a conventional coal plant. But what the SCS people realized is that while coal is pretty much good for only one thing, the hydrogen locked inside the coal has multiple uses. In particular, it can be a feedstock to make ammonia and urea, which are used to manufacture fertilizer. So the PurGen plant will be two plants in one: a hydrogen-burning power plant churning out electricity when demand is high, and a chemical plant making hydrogen-based ammonia and urea when electricity demand is low. And sulfur dioxide extracted from the coal will be converted into sulfuric acid and sold as well. As a result, PurGen should yield substantially more income than a conventional 750-megawatt coal power plant could. “It puts the capital investment to work 24 hours a day,” Schrag says.

And churning out ammonia and urea is only one potential source of extra income. Hydrogen has plenty of other applications. It can be used to generate electricity in fuel cells, for example, which could become a significant source of energy for transportation and distributed power in the coming decades. At present, most commercially produced hydrogen is derived from natural gas in a process that “has an awful carbon footprint,” Bauer says. Any serious attempt to tax or cap carbon emissions would make PurGen’s hydrogen much more attractive to the chemical industry than the conventional sort.

Strictly speaking, PurGen will not be entirely emission-free. When you burn hydrogen in pure oxygen, the only by-product is water; when you burn it in air, as PurGen will, you also get nitrogen oxides. The urea plant will create some particulate emissions too. Bauer says all of these will fall well within state and federal pollution guidelines. The big advantage of PurGen, though, is that it avoids the copious carbon emissions that normally come with burning coal.

The captured CO2 will be liquefied on site and pumped through a two-foot-diameter pipeline that will snake south through the waters of the Arthur Kill, turn eastward through Raritan Bay out into the Atlantic Ocean, and arrive, about 140 miles later, at a natural repository of Lower Cretaceous sandstone more than 8,000 feet below the seafloor. The formation is huge, stretching from Long Island to Georgia. It is highly permeable, making it easy to pump the CO2 in, and is capped by layers of impermeable shale with a total thickness of about a mile, making it hard for the CO2 to get back out. “There’s no way that CO2 is going to leak out in a million years,” Schrag says.

SCS acknowledges that even with sharply reduced emissions, coal is inherently dirty. No matter how you burn it, you still have to mine it—dumping West Virginia mountaintops into nearby rivers, gouging huge scars into the earth in Montana or Wyoming, and exposing miners to the risk of injury or death. “We take these issues seriously,” Bauer says, “which is why we’ve pledged not to use mountaintop-removal coal.” Instead, the company will use high-sulfur coal—mined mostly in Pennsylvania, Ohio, and West Virginia—and will then pull the sulfur out as part of the CCS process.

Environmentalists, who have formed an ad hoc group called the Arthur Kill Watershed Alliance to oppose the plant, have plenty of other objections. For starters, they ask, what if the CO2 leaks? “This is almost like storing nuclear waste,” says Jeff Tittel, director of the Sierra Club’s New Jersey chapter and chairman of the Watershed Alliance. “What happens if there’s an earthquake? You’re going to end up with a giant burp that puts all that carbon back into the environment.”

Schrag tends to lose his cool when he hears this sort of thing. “The New Jersey Sierra Club is crazy,” he says. Although earthquakes do occur in the northeastern United States, he notes, there is no reason to expect that even a massive quake could release CO2 stored underneath a mile and a half of rock: “This is nothing more than a scare tactic. It’s no different from the irresponsible scare tactics right-wing think tanks use.”

Another objection to PurGen has to do with resources. For the $5 billion cost of PurGen, Tittel says, “we could put more than 550 windmills off our coast, creating 1,600 to 1,800 megawatts of electricity. We could put solar on every roof in Union County,” where Linden is located. “And we could reduce energy consumption by 15 percent in New Jersey through efficiency alone.”

Schrag’s response to this argument is even pithier. “Garbage,” he says. “I’m an environmental scientist and a super-advocate for dealing with climate change.” But New Jersey isn’t very sunny, he points out, and it isn’t especially windy. At the outside, he thinks the state might be able to get 20 percent of its power from renewables. “For the rest, the only nonpolluting alternatives are coal with CCS and nuclear,” he says. “The New Jersey Sierra Club opposes both.” (The opposition notwithstanding, the town of Linden approved the project in January. SCS now expects to begin construction in 2012 and to finish in 2016.)

But the greatest hurdle facing carbon-capture coal-fired power plants—not just in New Jersey but around the country and the world—is the other kind of green: dollars. Even with PurGen generating income around the clock, SCS admits that the plant still might not be financially appealing if not for the $20-per-metric-ton carbon-sequestration tax credit that was tacked onto 2008’s TARP bank-rescue legislation. (The law covers up to 75 million metric tons of sequestered carbon from all sources; PurGen will generate 5 million tons per year.) “Over the longer term,” says Bradley Campbell, the former commissioner of New Jersey’s Department of Environmental Protection and now chief counsel to the PurGen project, “we’re going to need a price on carbon, whether it’s a tax or cap-and-trade legislation, for this plant to meet its potential.”

With a focused, decades-long effort, the United States could probably get most of its electricity from wind, solar, and other renewable sources. But the most abundant and reliable supplies of wind and solar energy are in the Great Plains and Southwest. Not only would major new wind farms and photovoltaic arrays have to be constructed there, but the entire electric grid would have to be upgraded and reconfigured to bring that electricity to the population centers where it is needed. Americans would also have to become far more efficient in their use of electricity.

If that really does happen, the need for carbon capture and sequestration will disappear. Schrag and the folks at SCS Energy think that a wholesale movement toward renewables and extreme efficiency is a very long shot, however, so they are moving ahead with what they think could be a model for America’s energy future, or at least a big part of it. And because the technology is not especially exotic, it could also in principle work for China and India, places where coal is almost surely going to be the primary energy source for decades to come. Fertilizer and distributed power from fuel cells would satisfy important demands in both of those countries, so the economic model of PurGen could make sense there, too—again, assuming that local tax laws recognize the benefits of burying carbon rather than spewing it into the atmosphere.

If the world ever does reach an accord to cap CO2 emissions, the PurGen model might go global and the carbon might go back underground. Which would make the capitalists at SCS Energy very happy indeed.

 


Let a Thousand Boxes Bloom

In February, millions of viewers of 60 Minutes on CBS saw a laudatory profile (CBS, Discover) of the Bloom Box, a refrigerator-size device that could provide enough electricity to power 100 U.S. homes. Since then, buzz on the box and its creator, Bloom Energy of Sunnyvale, California, has been relentless. “From a market perspective, what they’ve done is remarkable,” says Scott Samuel­sen, director of the National Fuel Cell Research Center at U.C. Irvine. “After 20 years of these fuel cells’ being out there, in one week Bloom Energy has captured the attention of the media and the public.”

Fuel cells can run on hydrogen, natural gas, or biofuels—the latter two requiring a reformer that processes the fuel to extract hydrogen. The hydrogen flows into the cell on one side while oxygen enters from the other. The reaction yields a flow of electrons that produce a current. Because there is no combustion, fuel cells run extremely cleanly: Their emissions are just water and carbon dioxide, and they produce less than half as much CO2 per kilowatt-hour as do traditional power plants. If the cells run on hydrogen—which could be derived from a clean-coal plant, for instance—the only direct by-product is water. Fuel cells are also compact and nearly silent, making them appealing as backup generators or even as distributed power sources for the home.

The biggest hurdle is cost: At present, electricity from fuel cells costs four times more than the juice from your wall outlet. Many solid-oxide fuel cells, including the Bloom Box, operate at 1,250 to 1,800 degrees Fahrenheit. Economically viable cells will need to use inexpensive materials that can withstand the heat for years while operating at high efficiency. That is what Bloom Energy says it has done. The positive and negative terminals of its fuel cells are made with a proprietary coating that the company has not identified; in between is a layer of baked sand—silicon. Samuelsen notes that Rolls Royce and Delphi are working on similar technologies but says commercial versions are at least three years away.

Revised regulations could help fuel cells catch on. Several states—including California, New York, and Connecticut—are rewriting their utility rules so individuals or companies can sell electricity (from a fuel cell or other private power source) back into the grid. “Fuel cells are clean and efficient, but we have to create a market for them,” says Neal Montany, director of the stationary fuel cell business at UTC Power, which recently installed fuel cells at a handful of Whole Foods markets.  —Amy Barth

See Discover's earlier coverage of FutureGen, another CCS plant.

Next Page
1 of 2
Comment on this article
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT
ADVERTISEMENT
Collapse bottom bar
DSCNovCover
+

Log in to your account

X
Email address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it emailed to you.

Not registered yet?

Register now for FREE. It takes only a few seconds to complete. Register now »