The Azimuth Project
Carbon capture and storage (Rev #16)

Contents

The idea

Carbon capture and storage, also known as carbon capture and sequestration or CCS, describes a variety of ways to reduce the carbon dioxide emitted by burning fossil fuels. Most commonly it refers to methods based on capturing carbon dioxide from large point sources such as fossil fuel power plants and storing it so that it does not enter the atmosphere. It also refers to ways of removing CO2 directly from ambient air, for example by biological methods such as biochar.

In the following paper:

  • D’Alessandro et al, Carbon dioxide capture: prospects for new materials, Angew. Chemie Int. Ed. 49 (2010), 2–27.
the authors summarize two of the key issues as follows:

Two points must first be made with respect to capture materials and potential capture technologies, given the sheer magnitude of global CO2 emissions. First, any chemical employed to capture CO2 will rapidly exhaust its global supplies if it is used in a once-through manner; and second, any chemical produced from CO2 as a reactant will rapidly saturate global markets for that chemical. These considerations underscore the necessity that capture materials must be regenerable. In this case the energy input for regeneration is one of the key factors in determining the efficiency and cost.

List of methods

We need a listing of different methods of CCS. What follows is a start. Then: how they work, how well they can be scaled up, and some scientific and engineering challenges that need to be addressed for each one!

Injection into the ground

One widely studied approach to CCS is simply injecting CO2 into the ground. See:

In 1991, Norway became the first country in the world to impose a federal tax on atmospheric CO2 emissions from operations such as coal-fired power plants. Later this tax of $55 of per ton of CO2 was extended to cover offshore oil and gas production. This motivated Norwegians to set up an operation called Sleipner which strips CO2 from natural gas offshore in the North Sea and reinjects 0.3 megatons of carbon a year into a non–fossil-fuel–bearing formation. This is apparently the world’s largest carbon capture and storage project. However, a one-gigaton ‘[[stabilization wedges|wedge]]’ would require building 3500 Sleipner-sized projects (or fewer, larger projects).

For more details, see:

For safety issues, see these comments on the Sleipner project:

Among other things, they write:

The injected CO2 will potentially be trapped by geochemical processes. Solubility trapping has the effect of eliminating the buoyant forces that drive CO2 upwards, and through time it can lead to mineral trapping, which is the most permanent and secure form of geological storage.

Solubility trapping

Solubility trapping is where the CO2 dissolves in water. It’s harder for the CO2 to escape the reservoir when it’s dissolved, rather than just sitting on top of water in a light buoyant phase. The solution itself sinks deeper and more securely into the reservoir, because it’s heavier with CO2 in it. Mineral trapping is where the CO2 chemically reacts with minerals so that carbon gets sequestered in stable, solid precipitates.

On Azimuth, [[John Furey]] writes:

I don’t have any confidence in high volume injection over the long term. Our species has been geologically injecting at all only about 50 years. The ground underneath our feet is not in homogeneous layers, contrary to the cartoons comprising most all modeling, and even if it were there are unpredictable side effects at any given site. If you’ve been following the news about fracking, you’re aware that the most experienced corporations with the most economic incentives to do things right environmentally fail miserably because they do not really understand even shallow injection:

Of course leaking, contamination, etc is to be expected (rational i.e. calculated risks). What is not being reported is volcanos of fracking fluids kilometers from injection sites. They scratch their heads, close that well, and move over horizontally a little bit.

Hank Roberts writes:

Worry seems to be that old oil and gas fields will have had lots of old wells drilled over time – often not mapped or recorded – plugged with concrete and abandoned, and increasing CO2 pressure will accelerate failure:

Here are some further references discussing trapping mechanisms and sometimes failure modes:

Here is the executive summary:

The success of geologic carbon dioxide (CO2) sequestration as a large-scale carbon management strategy is critically dependent on the ability of the geologic sinks and trapping mechanisms to confine the injected CO2 for hundreds to thousands of years. Leakage of CO2 from geologic sinks could result in significant release of the CO2 back to the atmosphere, potentially reducing, if not negating altogether, the benefits of geologic CO2 sequestration. For example, a leakage rate of 1% per year from 1 billion tons of geologically stored CO2 (10 million tons) would exceed the current annual CO2 emissions from all the power plants in North Dakota (4 million tons). Further, leakage could have negative ecological effects and present the potential for health problems other than global warming. Clearly, the more CO2 that is stored, the greater the potential that leakage from geologic sinks could result in adverse environmental and atmospheric impacts. It has recently been proposed that leakage rates of 0.01% per year be established as a performance requirement for geologically sequestered CO2 (White et al., 2003).

This report provides an analysis of how the physicochemical properties of CO2 would affect its trapping potential and mobility in various types of geologic environments. Analog studies of geologic environments containing large, concentrated amounts of CO2 or hydrocarbons gas were also used to derive insight regarding the leakage processes that would be inherent in geologic CO2 sequestration. The analogs included a) naturally occurring deposits of high-purity CO2, b) a mature CO2 flood enhanced oil recovery (EOR) project, c) an aquifer natural gas storage reservoir, and d) coalbed natural gas deposits.

Injected CO2 can be trapped in geologic sinks by four types of mechanisms. Different types of geologic sinks in combination with their site-specific properties would trap CO2 by different mechanisms. More than one type of trapping mechanism would typically be present in a single geologic sink. Most trapping mechanisms do not permanently immobilize CO2. Thus leakage of CO2 to the surface can potentially occur from all types of geologic sinks.

In the right types of geologic settings, a large, concentrated amount of CO2 could be stored for a geologically long time period without the risk of significant CO2 leakage to the surface. The dominant, but by no means sole, barrier to CO2 leakage to the surface from geologic sinks is not the trapping mechanism(s) but rather the permeability characteristics of the rock layers overlying or adjacent to the geologic sinks. The hydrologic properties of the formations containing the geologic sinks would also affect the potential for CO2 leakage. Geologic settings with relatively static hydrology, i.e., low formation.

Injecting CO2 into deep geological strata is proposed as a safe and economically favourable means of storing CO2 captured from industrial point sources. It is difficult, however, to assess the long-term consequences of CO2 flooding in the subsurface from decadal observations of existing disposal sites. Both the site design and long-term safety modelling critically depend on how and where CO2 will be stored in the site over its lifetime. Within a geological storage site, the injected CO2 can dissolve in solution or precipitate as carbonate minerals. Here we identify and quantify the principal mechanism of CO2 fluid phase removal in nine natural gas fields in North America, China and Europe, using noble gas and carbon isotope tracers. The natural gas fields investigated in our study are dominated by a CO2 phase and provide a natural analogue for assessing the geological storage of anthropogenic CO2 over millennial timescales. We find that in seven gas fields with siliciclastic or carbonate-dominated reservoir lithologies, dissolution in formation water at a pH of 5–5.8 is the sole major sink for CO2. In two fields with siliciclastic reservoir lithologies, some CO2 loss through precipitation as carbonate minerals cannot be ruled out, but can account for a maximum of 18 per cent of the loss of emplaced CO2. In view of our findings that geological mineral fixation is a minor CO2 trapping mechanism in natural gas fields, we suggest that long-term anthropogenic CO2 storage models in similar geological systems should focus on the potential mobility of CO2 dissolved in water.

Direct capture from the air

In capturing CO2 from point sources, the dominant cost is supposedly the cost of capture rather than storage. However, [[David Keith]] has argued that direct capture from the air could be viable:

Enhanced weathering

One of the main long-term mechanisms that removes carbon dioxide from the ocean and atmosphere is the natural weathering of rocks. We can vastly accelerate this process by digging up suitable rocks, crushing them into powder and spreading them around. The rock dust then ‘weathers’ by reacting with carbon dioxide. This method of carbon capture and storage is called enhanced weathering. In principle it can also serve as a source of [[carbon negative energy]].

For more details, see [[Enhanced weathering]].

Cement manufacture

The manufacture of ordinary Portland cement uses a large proportion of limestone. This is heated in a kiln, driving off the CO2. By replacing the calcium from limestone with magnesium from minerals such as serpentine it is possible to make the manufacture low- or even negative-carbon, producing a cement which has similar properties. Annual world production of cement, 2010, is around 2 billion tonnes.

See:

Making methanol

This is not exactly a form of carbon capture and storage, but related. See [[Methanol economy]].

Coal bed methane extraction

Disused and uneconomic coal mines continue to emit methane. They can also be used to sequester carbon dioxide. Coal has a stronger affinity for CO2 than methane. So, putting CO2 in mine shafts displaces the methane, which can be captured and used as it rises to the surface. This idea is called coal bed methane extraction. It may constitute a source of [[carbon negative energy]].

See:

Methane hydrate reactions

Another idea, due perhaps to ‘Uncle Al’ of internet fame, is to pump liquid CO2 into methane hydrate formations. He claims that the recovered natural gas plus sequestered CO2 has net zero carbon footprint. The reactions involved are

CH4 + nnH2O(s) \to CH4(g) + nnH2O(l) + 54.44 kJ/mol gas

CO2 + nnH2O(s) \to CO2(g) + nnH2O(l) + 63.6 kJ/mol gas

For more on the chemistry of methane hydrates (also known as methane clathrates), see

Carbon capture and storage for coal-fired power plants

For a good introduction to CCS for coal-fired power plants, see:

Here are some particularly relevant bits:

Overall, coal-burning power plants provide nearly half (about 46 percent this year) of the electricity consumed in the United States. For the record: natural gas supplies another 23 percent, nuclear power about 20 percent, hydroelectric power about 7 percent, and everything else the remaining 4 or 5 percent. The small size of the “everything else” total is worth noting; even if it doubles or triples, the solutions we often hear the most about won’t come close to meeting total demand. In China, coal-fired plants supply an even larger share of much faster-growing total electric demand: at least 70 percent, with the Three Gorges Dam and similar hydroelectric projects providing about 20 percent, and (in order) natural gas, nuclear power, wind, and solar energy making up the small remainder. For the world as a whole, coal-fired plants provide about half the total electric supply. On average, every American uses the electricity produced by 7,500 pounds of coal each year.

So, Fallows argues, it’s hopeless to quit burning coal anytime soon — so we need to do it better.

What would progress on coal entail? The proposals are variations on two approaches: ways to capture carbon dioxide before it can escape into the air and ways to reduce the carbon dioxide that coal produces when burned. In “post-combustion” systems, the coal is burned normally, but then chemical or physical processes separate carbon dioxide from the plume of hot flue gas that comes out of the smokestack. Once “captured” as a relatively pure stream of carbon dioxide, this part of the exhaust is pressurized into liquid form and then sold or stored. Refitting an existing coal plant can be very costly. “It’s like trying to remodel your home into a mansion,” a coal-plant manager told me in Beijing. “It’s more expensive, and it’s never quite right.” Apart from research projects, only two relatively small coal-fired power plants now operate in America with post-combustion capture.

Designing a capture system into a plant from the start is cheaper than doing refits. But even then the “parasitic load” of energy required to treat, compress, and otherwise handle the separated stream of carbon dioxide can come to 30 percent or more of the total output of a coal-fired power plant—so even more coal must be burned (and mined and shipped) to produce the same supply of electricity. Without mandatory emission limits or carbon prices, burning coal more cleanly is inevitably more expensive than simply burning coal the old way. “When people like me look for funding for carbon capture, the financial community asks, ‘Why should we do that now?’” an executive of a major American electric utility told me. “If there were a price on carbon”—a tax on carbon-dioxide emissions—“you could plug in, say, a loss of $30 to $50 per ton, and build a business case.”

“Pre-combustion” systems are fundamentally more efficient. In them, the coal is treated chemically to produce a flammable gas with lower carbon content than untreated coal. This means less carbon dioxide going up the smokestack to be separated and stored.

Either way, pre- or post-, the final step in dealing with carbon is “sequestration”—doing something with the carbon dioxide that has been isolated at such cost and effort, so it doesn’t just escape into the air. Carbon dioxide has a surprisingly large number of small-scale commercial uses, starting with adding the sparkle to carbonated soft drinks. (This is not a big help on the climate front, since the carbon dioxide is “sequestered” only until you pop open the bottle’s top.) All larger-scale, longer-term proposals for storing carbon involve injecting it deep underground, into porous rock that will trap it indefinitely. In the right geological circumstances, the captured carbon dioxide can even be used for “enhanced oil recovery,” forcing oil out of the porous rock into which it is introduced and up into wells.

These efforts are in one way completely different from “advanced research and development” as we often conceive of it, and in another way very much the same. They are different in that the scientists and entrepreneurs involved do not seem to count on, or even hope for, the large breakthroughs we have come to assume in biological sciences and info-tech.

Instead of big breakthroughs, he argues that we need the incremental improvements that come when you’re actually doing something on a large scale. And that’s where China comes in:

In the search for “progress on coal,” like other forms of energy research and development, China is now the Google, the Intel, the General Motors and Ford of their heyday—the place where the doing occurs, and thus the learning by doing as well. “They are doing so much so fast that their learning curve is at an inflection that simply could not be matched in the United States,” David Mohler of Duke Energy told me.

“In America, it takes a decade to get a permit for a plant,” a U.S. government official who works in China said. “Here, they build the whole thing in 21 months. To me, it’s all about accelerating our way to the right technologies, which will be much slower without the Chinese.

“You can think of China as a huge laboratory for deploying technology,” the official added. “The energy demand is going like this”—his hand mimicked an airplane taking off—“and they need to build new capacity all the time. They can go from concept to deployment in half the time we can, sometimes a third. We have some advanced ideas. They have the capability to deploy it very quickly. That is where the partnership works.”

How it works:

Ten years ago, at the end of the Clinton administration, the Chinese and American governments signed a “Fossil Energy Protocol,” to coordinate research on better use of coal and oil. Political leaders have come and gone since then, but the cast of technicians, civil servants, and business officials on each side has been relatively stable and has gotten used to working together. After taking office as secretary of energy last year, Steven Chu—a celebrity in China because of his Chinese heritage and his Nobel Prize—gave a new push to these efforts, hiring additional staff members for the U.S.-China office and committing $75 million to a joint Clean Energy Research Center.

The efforts of two scientists we’ve already met, Julio Friedmann and Ming Sung, illustrate what Americans can and cannot do to shape what happens in China—and the mounting advantages on China’s side relative to America’s.

Friedmann, who is in his mid-40s, has become one of the world’s experts on sequestration: how and where carbon dioxide can safely be stored underground. He was trained in geology at MIT and the University of Southern California and initially went to work for ExxonMobil. But by the early 2000s he had become fascinated with the emerging science of underground carbon-dioxide storage. “At that point, it was clear that nearly all of the really cool work was being done in the national labs,” he told me. In 2004 he and his family moved from Maryland to California, where he joined Lawrence Livermore. He is now the head of the Carbon Management Program there and the technical leader of a government-university-business consortium that this summer won a Department of Energy competition to help develop carbon-sequestration projects in China. To give an idea of the consortium’s range, it includes three universities, three national laboratories, two scientific nongovernmental organizations, and six large corporations, among them General Electric, Duke Energy, and AEP.

What Julio Friedmann? does:

On a typical trip to China, he will spend half his time in Beijing or Shanghai, meeting with government and corporate officials—and the other half in Xi’an or the Inner Mongolian wilderness, where many of the most promising storage locations are found. What he and his team have to offer, from the American part of the supply chain, is expertise on geological formations, on computer models for how the “plume” of liquefied carbon dioxide will settle into porous rock, and on other benefits of America’s decades of experience in petroleum geology. He can also put Chinese plant managers, scientists, and bureaucrats in touch with overseas counterparts they would otherwise never meet. “Projects like these are sort of like the school dance,” he told me. “You’re not getting married, but you’re figuring out how to interact. We need to start the process in a way that gives people the confidence to do it again, and again, and again. The confidence is the product.” The more often Chinese and foreign officials work together, the more easily they continue to work together. This might sound trivial, but I’ve become convinced that the steady expansion of these contacts will make a major difference in how an ever more powerful China deals with the rest of the world. What does Friedmann, or the United States, get from the process? “More tons sequestered, rather than emitted, in China,” he told me. But also something unavailable in America: a chance to see new technology in new plants and learn how it works. “In the U.S. today, there is not a single demonstration of capturing CO2 from a coal-fired plant at large scale,” he said. “The technologies have been a little too expensive to actually implement. That’s why we started looking at China.” They can afford to build, and Americans can hope to watch and learn.

What Ming Sung’s Clean Air Task Force? does:

In the early 2000s the task force, originally a conventional anti-air-pollution group, embraced the necessity of cleaning up coal. In Beijing, Sung gave me a copy of its latest working paper, in both Chinese and English, called “Coal Without Carbon.”

The group has sponsored research on sequestration, on post-combustion capture, and on the “cleanest” of the emerging pre-combustion coal technologies—“underground coal gasification.” In this process, jets of air (or pure oxygen), sometimes with steam or various chemicals, are blasted into coal seams deep underground. They interact chemically with the coal to produce a gas that flows back up a pipe and can be burned. It leaves in the ground much of the carbon, sulfur, nitrogen, and other elements that create greenhouse gases and other pollutants when coal is burned.

“And this can be very cheap,” Sung told me. “You don’t have to mine the coal. You don’t have to send men underground or haul coal around or dispose of ash. All the dirty stuff stays buried.” Because of these and other savings, he said, coal used this way could match or beat the price of today’s standard dirty power plant.

But in advocating the whole range of “clean coal” technologies, Sung and his team have the same problem Julio Friedmann has with carbon sequestration: it’s not happening in the United States. There’s one significant exception: the Texas Clean Energy Project?, a plant being built outside Odessa, which will apply underground-gasification technology to capture 90 percent of its carbon, more than any other commercial plant in the world. It received a $450 million federal award, just over half from the Department of Energy’s [[Clean Coal Power Initiative]] and the rest from the American Recovery and Reinvestment stimulus program (toward the $2.1 billion total capital cost). If it works as promised, this facility will be an advance over any coal-fired plant operating anywhere: it will gasify coal underground, eliminating the cost and damage of mining; it will sell urea (for fertilizer) and other chemical by-products of the underground gasification; and it will use the captured carbon dioxide for enhanced oil recovery in the nearby Permian Basin oil fields—all in addition to generating power.

(Correction: The decarbonization and other cleanup steps that make this plant distinctive are done above rather than underground. For full details, see texascleanenergyproject.com/about-tcep.)

References

For starters, try:

  • Carbon capture and storage, Wikipedia.

  • The Carbon Capture Report — daily reports, daily newspaper and analytics from the University of Illinois.

  • ICO2N — the Integrated CO2 Network, a group of Canadian companies representing multiple industries, including coal and the oil sands. All ICON member companies claim to have a strong interest in developing carbon capture and storage.

category: carbon