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Carbon capture and storage finally approaching debut

Long-awaited method to rein in carbon emissions still faces hurdles and doubts

3:11pm, August 22, 2014
carbon capture and storage illustration

POCKETING POLLUTION  Carbon capture and storage can cut up to 90 percent of carbon dioxide emissions from power plants. With more than a dozen false starts, the technology has yet to be demonstrated on a commercial scale. Two projects nearing completion could soon change that. 

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Like every other project, Jänschwalde failed.

In 2008, it was set to become the world’s largest demonstration of just how cleanly coal could be burned to generate electricity. The revamping of an aging power plant in Germany, Jänschwalde was to become a paragon of a technology that can slash up to 90 percent of the carbon dioxide emitted by fossil fuel–burning power plants — the single largest global source of greenhouse gas emissions. The technology, called carbon capture and storage, or CCS, collects planet-warming carbon pollution produced by power plants and permanently removes it from circulation. As the world steadily increases its use of fossil fuels, and greenhouse gas emissions continue to soar, CCS holds massive potential to help avert the dire climate scenarios predicted for the next century.

Yet, like more than a dozen similar projects, Jänschwalde was abandoned. CCS, with all its potential, returned to a state of limbo. For years now — starting well before Jänschwalde folded — scant funding and hostile politics have held CCS back. Despite successful trials and pilot projects, the promising technology still has no large-scale demonstration, no foothold in mainstream power production.

“This is a bit of a sad story,” says Wolfgang Rolland of Vattenfall, the Swedish state-run power company that ran the Jänschwalde project. “We’ve lost four or five years,” says Rolland, head of business communication for Vattenfall’s mining and generation unit. “On the other hand, none of the problems we have are solved. We still have climate, we still have the world increasing the use of coal.”

This year, the story of CCS could change. In North America, two commercial-scale power plants are on the cusp of firing up CCS technology for the first time. Both are entering the final stages of construction. The projects, one in Mississippi and the other in Canada, already have made it further than any other carbon capture demonstration project to date. If the two projects come online, they could clear a path for other CCS-equipped plants around the world, lower emissions and help to combat climate change. If the new plants go the way of Jänschwalde, it would mean more years in limbo for the technology.

Worries about these projects are percolating within the CCS community. The specific technologies that each plant has chosen may be hard to replicate elsewhere. And both projects have faced financial struggles and delays, perhaps setting a troubling precedent for future plants.

The field is wary, says Howard Herzog, a senior research engineer at MIT and an expert on CCS technology. “People are more in a wait-and-see attitude,” Herzog says. “In 2008, there was a lot of optimism. Now, there are not a lot of new projects coming into the pipeline.”

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Shaky starts

Despite uncertainty over its implementation, the technology behind CCS works. In some cases, it has worked for decades. Even without a commercial rollout, CCS scientists and engineers have crept toward cheaper, more efficient methods. Bits and pieces of the technology have cropped up in environmental monitoring systems and in the food processing and beverage industries, which can use CO2 collected from power plants. More than a dozen small trials worldwide have proven that CCS can cut emissions from power plants and safely store the captured gas in rock formations deep underground.

So far, scientists have developed three ways to capture carbon from power plants and other emission sources: oxyfuel combustion, precombustion and postcombustion. The oxyfuel method burns fuel not in air but in pure oxygen, resulting in exhaust that is mostly CO2 and water vapor, which are easy to separate. In precombustion, fuel is converted to a gassy mixture of CO2 and hydrogen. The two gases are then
separated, and the CO2 is collected while the hydrogen moves to a turbine. In postcombustion, the most established capture method, the exhaust created by burning fuel moves through large silos that chemically scrub it of CO2. After capture, the CO2 is piped down to storage. 

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“The individual technological pieces that fit together for CCS are all established,” says CCS expert Casie Davidson of the Pacific Northwest National Laboratory in Richland, Wash. The only missing step, she says, “is to demonstrate how the technologies work together as a whole.”

Jänschwalde was meant to be that demonstration. The 1.5 billion euro (around $2 billion) project would have spruced up an old, air-polluting coal plant in Germany with both oxyfuel and postcombustion technologies, giving its operators the ability to lock away about 1.7 million metric tons of CO2 each year. But in 2011, amid public fears and drawn-out policy battles, Vattenfall ditched Jänschwalde before the project ever broke ground. This May, Vattenfall announced its defeat, abandoning all efforts on CCS.

Vattenfall found the technology trapped in a catch-22: Without a demonstration of CCS on the scale of Jänschwalde, critics say the technology isn’t ready for prime time or worthy of government incentives and public backing. And without that backing, building a large demonstration is difficult, given the financial and regulatory obstacles. The dilemma played out in the United States last September, when the Environmental Protection Agency proposed that new fossil fuel plants come equipped with CCS technology. Power companies balked, claiming that requiring the expensive, “unproven” technology would drive coal plants out of business. In June, the EPA released regulations to cut carbon pollution from existing power plants but made no requirements for CCS.

Rolling out new technology isn’t easy, says Ken Humphreys, chief executive officer of FutureGen Industrial Alliance, which is planning one of the few full-scale CCS projects still in the pipeline. “It’s not particularly surprising that around the world, for every 10 projects you see announced, only one or a couple go to construction,” he says. FutureGen, based in Jacksonville, Ill., is planning to retrofit a coal plant in Illinois with oxyfuel combustion and have it running by 2017.

The potential for CCS to help fight climate change makes the struggle worthwhile, says Humphreys. The scientific community agrees. In a report released in April, the United Nations Intergovernmental Panel on Climate Change included CCS in a small set of clean-energy solutions that it says are needed to avoid a 2-degree-Celsius rise in global temperatures above preindustrial levels. Without tripling or quadrupling the use of these greener energies globally, climate change will continue to imperil communities worldwide, the IPCC concluded. The risks include flooding, extreme weather, threats to farm yields and fishery production and the spread of disease-carrying organisms.

Meanwhile, greenhouse gas emissions continue to increase. Global CO2 emissions linked to fossil fuel combustion reached roughly 31 gigatons in 2011. Of that, 42 percent, or about 13 gigatons, came from the generation of electricity and heat, according to the International Energy Agency, an intergovernmental organization. Since 1990, CO2 emissions from this sector have nearly doubled. While CCS potentially could cut carbon emissions from burning any fossil fuel, coal is an obvious first target. Releasing more CO2 during burning than any other fossil fuel, coal is the world’s leading source of energy-related CO2 emissions, accounting for about 44 percent. Its share of total energy sector emissions is expected to grow over the next two decades.

“The IPCC report is saying there’s going to be dire consequences,” says Herzog. Yet “the result is business as usual.”

Carpe carbon

According to Vattenfall’s Rolland, the best hope for anything other than business as usual is wrapped up in the fate of the two North American CCS projects: Mississippi’s Kemper County energy facility and the Boundary Dam power station in Estevan, Canada.

Even so, North American scientists don’t feel like front-runners. “If anything, we’ve gone downhill from 2009,” says chemical engineer Gary Rochelle of the University of Texas at Austin. Rochelle specializes in postcombustion capture, the technology slated for the Boundary Dam plant. Given the long string of failed CCS projects, Rochelle worries that the science behind CCS has stalled, and others worry that the field has lost engineering talent. The basic method for postcombustion capture was patented in the 1930s.

The Boundary Dam technology boils down to a simple acid-base reaction, using a method called amine scrubbing. In some modern versions, the gas produced in burning coal — usually a mix of oxygen, water vapor, nitrogen, CO2, and other trace pollutants such as sulfur dioxide — is blasted through a 15-meter-tall, 30-meter-wide cylinder packed with layers of eggcrate-shaped material. The gas blows in at the bottom, while an amine solution — an alkaline liquid — pours down from the top. The solution trickles over the large surface area created by the grooves and ridges in the material packing the cylinder. As the amine drips down, it grabs the acidic CO2 moving up. The exhaust, now scrubbed of any CO2, vents out the top. Meanwhile, the CO2-bearing solution pools at the cylinder’s bottom before being sucked into another giant tower. There, the mixture is boiled, releasing a stream of pure CO2 for capture.

Over the last 80 years, researchers have made incremental improvements — picking the best amine and tweaking designs to use less energy. Even so, the process can require about a quarter of a plant’s power output, particularly to boil off the CO2 in the stripping step. “We continue to make advances,” Rochelle says, “5 percent here, 5 percent there — evolutionary improvements.” Without a full-scale demonstration to tweak and perfect, these gains are academic.

Though Rochelle isn’t involved in the Boundary Dam project, he’s watching it closely. In addition to perhaps becoming one of the first large-scale demonstrations of CCS, the project could provide a model of how to equip existing power plants with postcombustion scrubbing. The $1.35 billion project, run by the Saskatchewan-based electric utility SaskPower, involves retrofitting part of an old coal-fueled plant with the technology. The company says the plant will capture about 90 percent of its CO2 emissions, or 1 million metric tons of CO2 each year, about the same annual reduction as taking 250,000 cars off the road.

The project has hit snags. It was initially expected to open this past April. Last October, SaskPower announced a delay and added $115 million to the project’s budget. The aging plant needed unforeseen upgrades, including steel reinforcements and lead paint removal. Work also slowed that month as the power company paused to remove 800 federally protected frogs from the area around the construction site. With more than 90 percent of the construction complete, SaskPower now plans to open the plant later this year.

The setbacks seem trifling when compared with those faced by Mississippi’s Kemper project, run by Southern Company. The $5.5 billion project was originally slated to open in early 2014. Its opening has been bumped to the first half of 2015, and its budget overruns are more than $1.5 billion. Delays and cost overruns aren’t the only problems facing the project.

Incendiary capture

The Kemper project will use precombustion capture that requires first turning unburned coal into a gas. The coal is pulverized, mixed with oxygen and steam and then heated in an apparatus called a gasifier. The process transforms the coal into a gaseous mixture containing hydrogen and CO2. To collect the carbon, the gases move into a pressurized silo where the CO2 meets a liquid solvent. Instead of a chemical reaction, as in amine scrubbing, the solvent physically absorbs the CO2 under high pressure, sort of like carbonating a beverage. And just as an uncapped bottle of soda eventually becomes flat, the CO2 can be released by dropping the pressure, which happens in an adjoining silo. That’s where the CO2 is collected.

At Kemper, the precombustion method is expected to capture about 65 percent of the plant’s CO2 emissions. “The environmental footprint is about the same as a natural gas plant,” says engineer Randall Rush, who manages the gasification technology group at Southern Company.

Although Kemper will be a lot cleaner than other coal-fired plants, Southern Company’s main goal isn’t to showcase CCS. Instead, it’s to demonstrate a newfangled, proprietary gasifier. In fact, the federal support Kemper has received, in the form of a $270 million grant from the Department of Energy, wasn’t part of the more than $3 billion the department has spent to support CCS; it came from a $2 billion federal fund to demonstrate coal technology that reduces nitrogen, mercury and sulfur pollution. Kemper’s gasifier makes efficient use of lignite, a low-quality coal. The moist, young coal packs less energy and is dirtier to burn relative to higher-quality coal. It’s also plentiful: Kemper sits near a minable reserve of more than 3.5 billion metric tons of lignite. 

Although Kemper is close to its debut, the project doesn’t thrill CCS experts. “Kemper is a very bad example,” says chemical engineer Stanley Santos, who works with the greenhouse gas research and development group of the International Energy Agency. Kemper’s massive budget overrun, delays and a plan to capture less carbon than other proposed projects make it a poor example of how to go about CCS, he says. And Southern Company seems to agree with Santos. In a February public hearing on the EPA’s proposed rules to reduce carbon pollution from existing power plants, the energy company’s environmental director testified that Kemper should not be used as a model for CCS because the technology may not be suitable for all coal-fired plants. 

Perfect cache

As a model for other CCS projects, the problems don’t end with Kemper’s precombustion technology. Its storage plans also don’t offer much of an example. The same applies to Boundary Dam’s. Ideally, captured carbon would be compressed, sucked into a pipeline and sent to an injection well. There, it would be shoved hundreds of meters belowground, beneath an impermeable cap of rock where the gas could be sequestered indefinitely.

Both Kemper and Boundary Dam plan to take a different approach: Captured CO2 will be sold to oil companies. These companies will use the gas to flush out extra oil from a field, extending a well’s productive life by pushing out extra drops of petroleum in a process called enhanced oil recovery. Although selling CO2 can help offset the costs of CCS, it may not be a long-term solution. Oil companies tend to recycle their CO2, sending it into oil wells over and over again. Such reuse could limit how much captured CO2 they buy.

Still, enhanced oil recovery definitely represents an advantage for North American companies, says Vattenfall’s Rolland. Places outside North America don’t have the same market for the practice. And long-term geological storage can be a sticking point, particularly in Germany. Part of the reason Jänschwalde never got off the ground was because of public fears that CO2 injections would carbonate water wells and trigger earthquakes.

While those concerns are real, carbon storage has advanced to a point where it can avoid those problems, says earth scientist Sally Benson of Stanford University, who’s been working on geological carbon storage since the 1990s. “We’ve basically just learned a tremendous amount that will allow us to select sites for maintaining the CO2 essentially permanently,” she says.

Experimental CO2 injections are now under way in a variety of places to help scientists observe and predict how the gas behaves underground and interacts with the surrounding rock. First, researchers make detailed maps of geological formations deep underground and forecast long into the future how injected COwill move within subterranean layers over time. Most of the injection trials and lab models have focused on saline aquifers, stores of salty water, in layers of sedimentary rock such as sandstone. But some researchers are studying CO2 injected into porous layers of basalt, a volcanic rock. Basalt has a unique chemistry that allows it to react with CO2, forming solid carbonate minerals that trap carbon indefinitely.

Once the CO2 is actually injected through deep-reaching wells, the gas pushes into the rock layer, where it can fan out through tiny pores and cracks. Engineers try to find injection sites that are far from geological faults and well below the depth of aquifers tapped for drinking water. They also look for areas that have a layer of solid rock above the aquifer that can act as a natural cap to keep CO2 from bubbling back up. As the CO2 plume moves through a rock layer, scientists can collect data and continually update their models to refine predictions, Benson says.

So far, CO2 storage in the United States has been tried only on an experimental basis. In March, the EPA issued its first-ever draft permit for the type of well needed for long-term CO2 storage. The so-called class VI permit went to FutureGen, the group planning the CCS project in Illinois that is slated to open in 2017. The plan is to store the carbon in a saline aquifer 48 kilometers from the power plant and more than 1,200 meters belowground. FutureGen worked closely with the EPA to lay out careful plans to inject, seal and monitor the 1.1 million metric tons of CO2 it plans to sequester each year. “Our objective is to prove that there are off-the-shelf technologies,” says FutureGen’s lead geologist Tyler Gilmore, who hopes the project will be a model for CCS.

Like so many CCS projects before it, FutureGen’s $1.65 billion effort is off to a good start. The FutureGen Industrial Alliance, a nonprofit made up of mining and coal companies, has worked to avoid delays and manage cost, signing labor contracts and completing detailed construction plans. Humphreys, the CEO, is certain the work is worth it. As long as power plants burn fossil fuels, carbon pollution will be a problem, he says. “I’m extremely confident that the technology is absolutely essential.”

CCS is well out of the gate. Now, Humphreys says, it just needs to cross the finish line.

This story appears in the September 6, 2014, issue with the headline, "Carbon Quagmire: Technology to capture CO2 from power plants approaches its long-delayed debut. But hurdles and doubts linger."

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