Energy

The Dirty Secret

Better technologies exist for extracting coal, a major source of carbon dioxide emissions. The challenge is getting people to adopt them.

Coal is the black sheep of the energy family. Uniquely abundant among the fossil fuels, it is also among the worst emitters of greenhouse gases. Mindful of coal’s bad reputation, President Bush promised the world three and half years ago that the United States would develop a superclean coal plant in an initiative known as FutureGen. The plant would have zero emissions; even the carbon dioxide it released would be pumped underground.

Today there is a patch of land in Great Bend, OH, where an advanced coal plant may one day be built. The plant could eventually include equipment for siphoning off carbon dioxide. But it’s not FutureGen, which today remains a collection of research projects. No FutureGen plant has been constructed, and no site for one has been chosen. The proposed plant at Great Bend could more appropriately be called “PresentGen.” The technology involved doesn’t demand a White House neologism suggesting that clean coal is something for which we must wait.

Smog in Shanghai results from the burning of low-grade coal. Chinese coal consumption is rising sharply. (Credit: Sherlyn Menez/WPN)

Great Bend is owned by American Electric Power (AEP), the largest coal-burning company in the United States. The company proposes to build what’s called an integrated gasification combined-cycle (IGCC) plant. IGCC is frequently referred to as a “new technology,” but it’s really a combination of two well-established technologies – both of which are also intended for FutureGen. The first is gasification, in which coal is partly combusted under carefully controlled temperatures and pressures and turned into a concentrated “syngas” of mainly carbon monoxide and hydrogen. (From syngas, impurities such as sulfur dioxide can readily be removed.) The second is the “combined cycle” – the electricity generation technology already ubiquitous in natural-gas power plants, where turbines are driven both by a stream of gas and by steam produced from waste heat. Most importantly, carbon dioxide can be captured from a gas stream far more easily than from the smokestacks of a conventional coal plant.

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IGCC plants are vastly more advanced than today’s pulverized-coal plants – which are planned in ever larger numbers around the world – but they’re hardly futuristic. “We’ve done a pretty thorough due diligence on the technology, and we didn’t casually come to the conclusion that IGCC was ready,” says Robert Powers, AEP’s executive vice president for generation. “Gasifiers have been used since the turn of the last century, in a crude sense, and used in the petrochemical industry and refining industry for years. And certainly, on the generating end of the plant, combined-cycle combustion turbines – we own combined-cycle combustion plants now. Each of those pieces is a mature and developed technology.”

Indeed, coal gasification, developed about a century ago, has long been the technology of last resort for countries unable to gain access to oil. The Nazis used it to fuel the Luftwaffe; South Africa adopted it during apartheid. In North Dakota, a coal gasification plant went online in the early 1980s after the Arab oil embargo, later began capturing and selling its carbon dioxide for use in oil recovery, and is still humming today.

Multimedia

And AEP is not alone in revisiting the technology. In Pennsylvania, an industrial consortium is proposing a 5,000-barrel-per-day coal-to-liquid plant, using technology from South African gasification giant Sasol. Peabody Energy is talking about a plant in Illinois that would produce natural gas from coal. The governor of Montana, Brian Schweitzer, is trying to jump-start a coal-to-liquids industry in his state. Abroad, a few companies are planning “oxy-fuels” plants, in which coal is burned in pure oxygen. (The exhaust gases are mainly carbon dioxide and water vapor; water can be condensed and removed, allowing collection of the concentrated carbon dioxide.)

What’s lacking is broad action to build such plants in significant numbers. Coal presents the world’s single largest opportunity for carbon dioxide mitigation. Coal consumption produces 37 percent of the world’s fossil-fuel-related emissions of carbon dioxide, the chief greenhouse gas. While oil consumption produces more – nearly 42 percent – much of that comes from cars, trucks, planes, and other means of transportation for which carbon dioxide capture is practically impossible. In the United States, coal contributes 51 percent of the electricity but 81 percent of the carbon dioxide related to power generation. The technology for cleaner coal plants and carbon dioxide capture exists. But in a story repeated across many energy sectors, little of it is actually being used.

AEP expects the Great Bend IGCC plant to cost 15 to 20 percent more overall than a conventional coal plant, but it could recoup the difference from customers under pending regulation in Ohio and West Virginia (site of a second proposed AEP IGCC plant). Capturing the carbon dioxide emitted by the plant, however, is another story. This part of AEP’s site plan is literally a blank space, reserved for some future day when carbon dioxide emissions might be regulated. AEP says it is already deploying its own strategies to cut carbon dioxide emissions by 6 percent. But like the White House, it opposes carbon dioxide limits – on the grounds that the United States shouldn’t do anything China and India aren’t doing. Yet the technology for carbon capture is mature, too. For years, the Norwegian company Statoil has been capturing and sequestering carbon dioxide produced by its natural-gas wells in the North Sea. And AEP maintains the position that underground sequestration seems feasible in regions it serves.

If IGCC is more than ready, its benefits are apparent, and sequestration seems plausible, why aren’t plants that at least make carbon dioxide capture simpler getting built? “I don’t necessarily think the technology is the limiting step. What’s not there is the economic incentive, of course,” says Howard Herzog, a chemical engineer at MIT, who manages an industrial consortium called the Carbon Sequestration Initiative. AEP estimates that IGCC plants with carbon sequestration could carry a 50 percent overall cost premium compared with traditional plants. But IGCC plants are also a little more efficient than traditional plants, and their cost might come down when they’re built in volume, or if improved designs and materials boost their efficiency further. Markets might even emerge for carbon dioxide, which can be pumped into oil wells to enhance production. Still, the proliferation of better coal-fired power plants will need kick-starting. “You are not going to do this without some policy changes,” Herzog says. “But technology-wise, I think we can do this quickly.”

The Coal Menace

Coal supplies 24 percent of all global energy and 40 percent of all electricity, and it spews more carbon than any other fossil source – kilowatt for kilowatt, twice as much as natural gas. Yet coal is the most abundant fossil fuel, and its use is intensifying. While estimates of remaining fossil supplies vary, the World Coal Institute says there are 164 years’ worth of coal still in the ground, in contrast to just 41 years’ worth of oil. Coal is being enthusiastically mined not only in the United States but also in India and China (where at least 79 percent of electricity comes from coal). The equivalent of more than 1,400 500-megawatt coal power plants are planned worldwide by 2020, according to the Natural Resources Defense Council. This includes 140 U.S. plants of various sizes. “Coal is going to be used. It was a bad joke played by God that oil and gas were put where there is no demand, and coal was put in China, India, and the United States,” says Ernest J. Moniz, an MIT physicist and a former under-secretary of the U.S. Department of Energy.

In short, we’re stuck with coal. Since there’s little reason to expect that humankind will stop digging for it, we will have to find cleaner ways to burn it. This was made clear by a Princeton University analysis that showed immediate ways to reduce carbon dioxide emissions. The analysis goes like this: Already, humankind is pumping about seven billion tons of carbon per year into the atmosphere, about three times as much as in the 1950s, and that figure looks likely to double by 2055. (These tonnages are for carbon; for carbon dioxide, multiply by 3.7.) At that rate, we’re on track to triple atmospheric carbon dioxide concentrations from preindustrial levels, creating temperatures not seen since three million years ago, when sea levels were 15 to 35 meters higher (see “The Messenger”).

But the Princeton group, called the Carbon Mitigation Initiative, showed that it’s possible, with today’s technologies, to deploy a variety of strategies that would each save one billion tons of carbon emissions per year. Deploy seven over the next 50 years and you’ve at least stopped the increase in carbon emissions. The group calls each billionton saving a “wedge.” Its report showed that sequestering carbon from 800 coal power plants – or 180 coal-based synfuels plants, which make liquid fuels – would furnish a wedge each. So would tripling nuclear power, doubling automotive efficiency, and implementing the best available energy efficiency technologies in buildings (see “The Un-Coal”). “These aren’t pipe dreams. These are here today and could be deployed at scale,” says Princeton’s Robert Socolow, a professor of mechanical engineering and codirector of the Carbon Mitigation Initiative.

But not all wedges are created equal. If we “get the automobiles wrong,” says Socolow, it’s not an insurmountable problem, because “they are not going to be there 20 years from now. But when we build a power plant – a new one – it’s going to be around for 50 or 60 years.” And that – along with coal’s impending status as the remaining cheap fossil fuel – is why a discussion of wedges very soon becomes a discussion of coal.

The Plug

We still need even better clean coal technology, but when it comes to reducing carbon emissions, the overriding research question is geological. No clean coal technology can forestall climate change without the aid of carbon dioxide sequestration. Unless the carbon dioxide from coal-fired plants is permanently stored somewhere, it will go into the atmosphere and worsen global warming. Sequestration proposals include pumping carbon dioxide underground, pumping it under the sea, and mineralizing it for burial. But significantly reducing carbon emissions while still increasing fossil fuel consumption will require a massive effort: liquid carbon dioxide would have to be sequestered on the same general scale on which the original fossil fuel sources were removed. It’s a staggering proposition.

To date, pumping carbon dioxide underground has mainly been a way to push more oil to the surface; the primary objective wasn’t really to store carbon dioxide permanently. So a critical question remains unanswered: will carbon dioxide stay where you want it?

In an old steel-walled lab at Los Alamos National Laboratory in New Mexico, geochemist George Guthrie holds out a smooth chunk of cement the size of a sea scallop. The chunk was recently drilled out of cement poured more than 50 years ago to plug the pipe in an old Texas oil well that had been crammed with carbon dioxide to enhance oil recovery. Guthrie holds up the chunk: a quarter-inch swath of it is the color of an orange Creamsicle. This staining, Guthrie says, is acid corrosion induced by carbon dioxide, which forms carbonic acid when it mixes with groundwater.

The chunk is a kind of Rorschach test. On the one hand, it could be read to imply that the carbon dioxide damaged the cement plug. On the other hand, it might imply that the damage was minimal – and may not progress further. There’s a lot riding on the answer. If the plug on a reservoir blew, the carbon dioxide could be released – and the climate benefits of sequestration would, as it were, vanish into thin air. “There are significant consequences for doing this wrong,” Guthrie observes. “On the other hand, it may be that much of the technology for doing this right already exists. There has been such enthusiasm behind [sequestration] that it is easy to forget about the implications of doing this on such a large scale.”

There is reason for guarded optimism. The Statoil project and the Dakota gasification plant have already stored 20 million tons of carbon dioxide each; a gas field in Algeria has stored 17 million tons; a project in the Netherlands, eight million. The U.N.’s Intergovernmental Panel on Climate Change estimates – based on experience and on models – that properly engineered systems could retain 99 percent of their carbon dioxide over 100 years and would “likely” do so over 1,000 years. AEP’s Powers, too, seems confident. “If you look at the science, it suggests that our footprint in the U.S. is blessed with the right geologic formations to sequester hundreds of years’ worth of CO2 emissions,” he says. “I’m not trying to trivialize the public-policy aspect of this, but you get a picture painted that the geology is there.”

What carbon dioxide we can’t sequester, or sell to oil companies hoping to use it to force out more oil, we could use to produce alternative fuels. Specifically, it could help make methanol, which could be a more practical fuel than hydrogen. Hydrogen is merely an energy carrier; energy is required to create it in the first place, either by splitting water molecules with electricity or by extracting it from fossil fuels. To make the transition to a “hydrogen economy,” not only would you need to produce the hydrogen, but you’d also need an entirely new infrastructure for delivering and storing it, plus vast improvements in fuel cell technology to make it useful.

But if you took hydrogen and combined it with carbon dioxide (which would be, admittedly, another energy-consuming step), you could produce methanol, essentially creating a liquid energy carrier. Unlike hydrogen, methanol could be transported using today’s infrastructure and burned in slightly modified versions of today’s vehicles. “The president says nice things about moving from a carbon-based economy to a new one. I think it’s said easily, but it’s not so easily done,” says George Olah, a Nobel laureate in chemistry and director of the Loker Hydrocarbon Research Institute at the University of Southern California. Olah is an active proponent of the “methanol economy”: “What I’m saying is that we have the basis of carbon dioxide that can be recycled,” he says.

Carbon’s Price

After President Bush told the nation it was addicted to oil in the State of the Union address this year, he reeled off several clean-energy research ideas and said we were “on the threshold of incredible advances.” The implication seemed to be that we need these “incredible advances” before we can really get serious about replacing fossil fuels or dealing with climate concerns.

The reality is that we already have several good technological options. The question remains one of policy. No energy company will reduce carbon dioxide emissions unless carbon dioxide has a cost. But because emissions are a classic example of what economists call a “negative externality,” where the cost of a thing is not borne by the parties involved in a transaction (here, energy producers and buyers), the government must impose that cost through regulation. One approach would be a “cap and trade” system – used successfully for sulfur dioxide – in which an overall limit is set on emissions from all regulated sources. Companies work out where best to cut emissions, then trade emissions credits in order to stay under the collective national “cap,” which can be gradually lowered as cleaner technologies emerge.

The first halting steps toward carbon dioxide regulation are being taken. California has moved to limit greenhouse-gas emissions from vehicles – but is facing court challenges from the auto industry. And the European Union has launched a carbon-trading system, now in its initial phase (see “Rocky Start for CO2 Trading”). But in the U.S., there is little imminent likelihood that carbon dioxide emissions from vehicles or power plants will be federally regulated.

In the summer of 2006, there is good reason to think that technology available today can significantly mitigate the carbon dioxide problem. But the technology is not enough. “People think you can do this without the policy, and that’s a myth,” says Herzog of MIT. Without public policy that imposes a cost on carbon emissions, he points out, “it’s always going to be cheaper to put it in the atmosphere than to do capture and storage.” Still, he and Socolow believe that regulatory help may be on the way. “We are at the point where some carbon dioxide policy is going to come out,” Socolow says.

In Great Bend, AEP is preparing for a possible new regulatory climate. It sees clean coal technology as more than ready – in this case, combined-cycle power plants from GE married to gasification technology purchased from Chevron. But without a policy incentive, AEP will not do any carbon dioxide sequestering. As the world digs for more coal, and the atmospheric concentrations of carbon dioxide inexorably rise, the part of the Great Bend plant that would capture and store carbon dioxide – forming a key wedge against worsening climate change – remains an empty space on an engineer’s drawing.

David Talbot is Technology Review’s chief correspondent.

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