CLIMATE:

Utility gambles that technology will keep coal plants in business

NIEDERAUSSEM, Germany -- Europe's biggest carbon dioxide emitter has no plans to stop burning coal.

Johannes Heithoff, the research chief for the German utility RWE, said his company's goal is to burn through its 3.4 billion metric tons of brown coal reserves, a supply that could last for decades.

But there's a complication: Europe's CO2 limits will tighten soon, making the operation of the smoke-stained, decades-old Niederaussem power station here prohibitively expensive. And when the boilers go cold as scheduled in the next few years, Heithoff vows he will replace them and reduce RWE's overall carbon footprint -- by building more coal-burning plants.

Seriously.

"By replacing these older units with state-of-the-art power stations, we can reduce CO2 emissions by 30 percent, roughly, based on the same amount of electricity produced," Heithoff said in a recent interview.

The Niederaussem plant looms over this small town, located on the outskirts of Cologne and the Rhine River, Europe's main industrial artery. Niederaussem dates to the 1950s, and the progression of coal-fired boiler buildings on the site -- each taller and more gleaming than the next -- reads like an evolutionary chart. Combined, they pump out some 3,800 megawatts of electricity and 26 million tons of CO2 each year, the latter nearly equal to the total emissions of New Zealand.

The CO2 reductions would come through efficiency, the leaps utilities have made in optimizing the power burned out of every cubic inch of lignite. Previous generations operated at efficiencies just above 30 percent, but RWE is now confident its newest-generation boilers, which include a new 1,000-megawatt unit at Niederaussem, will soon operate at 50 percent efficiency.

"This is a breakthrough in the technology," Heithoff said. "In history, we needed more than 30 years to improve from 30 percent up to 43 percent," while 50 percent will be reached within a decade, spurred largely by a technical process that dries coal prior to combustion.

Such an emissions reduction should not be discounted in the near future, when it could inch closer, but not nearly equal, to cuts that would be made by switching from coal to natural gas. But the problem remains that coal plants operate for far longer than a decade, and after 2020, far deeper CO2 cuts will be sought in Germany. In essence, any future construction of coal plants by RWE would be a long-term gamble that CO2 can be captured from flue gases.

That is why Heithoff put the "leech" on his plant.

At least, it looks like a leech. Using stacks of tubes and scaffolding stretching 40 meters vertically along the expansive backside of Niederaussem's newest plant, RWE for more than a year has operated a small, €9 million pilot plant that takes a pittance of the plant's waste flue gas -- 0.05 percent, to be precise -- and uses a chemical loop to remove 90 percent of the carbon dioxide from the stream.

In coal utilities' dreams, this is the shape of what's to come. Nearly all CCS projects launched recently -- including American Electric Power Co. Inc.'s high-profile Mountaineer project in West Virginia -- have attached capture systems onto existing plants, using a technology called post-combustion capture. It is the third and most expensive system competing to lead in CO2 capture technology, and, if only for the ubiquity of existing coal plants, it is the most likely to reach commercial use.

At first thought, it seems like a pipe dream that you could capture CO2 from the high volume and hot mix of water vapor, nitrogen and pollutants that constitute coal's flue gas. But Earl Goetheer, an engineer who manages CO2 capture research at TNO, the Dutch applied sciences research institute, says there is nothing to it.

"Capturing CO2 with post-combustion capture is really, really easy. It's child's play," Goetheer said. "The principles are well known. ... The problem at the end of the day is money."

Capture technology's 'parasitic load'

Companies have known for decades how to capture CO2 from other gases, even at the low atmospheric pressures found at most coal plants. Scrubbers had to be developed to prevent CO2 buildup in sealed systems like submarines and spaceships. And much of the industry's knowledge stems from the need to separate CO2 from natural gas or for use in ammonia production.

Indeed, one of the reasons BASF SE, the world's largest chemical company, is collaborating with RWE on its capture pilot has nothing to do with coal, Heithoff said. BASF wants to improve its ability to pull CO2 out of natural gas in the Middle East, which could then be used to enhance oil production as some of the region's wells begin to run dry.

In the end, capturing carbon dioxide requires little more than high-school chemistry, according to Andreas Northemann, BASF's head of gas treatment. CO2 is an acid, and drawn to react and bond with base chemicals, in this case solvents. So if you have a lot of solvents on hand -- and, with the massive volume of CO2 coal plants spew, "a lot" is an understatement -- CO2 can be pulled out.

Problem is, once the CO2 is out, those solvents don't want to let go.

"Simply phrased, if you take an acid and a base and put them together, you usually get heat," Northemann said. Regenerating the solvent so it can absorb more CO2 takes more heat than you have to put back in, stealing from electricity production and, in the utility's views, its profits.

Nearly all current post-combustion capture research is about this problem: reducing the "parasitic load" that the capture technology will have on the plant. This is often measured as a drop in efficiency. For example, the current state of the art in commercial solvents, from Dow Chemical Co., would drop a plant's efficiency by 11 percentage points, Goetheer said.

There are many routes to reducing this load, though most research focuses on better materials. In Europe, research has focused on using solvents called amines, or amino acid salts, the latter of which are less likely to escape into flue gas. In the United States, work has focused on chilled ammonia, an elegant system pioneered by the Energy Department that, so far, seems to promise the lowest energy toll, according to Goetheer.

There is another major problem with solvents, Goetheer added. They are expensive and will have to continually be replaced thanks to the strain coal byproducts put on them.

"When you burn coal, you don't just get CO2 and nitrogen," he said. "You get the full periodic system. All the garbage that's in coal will get out. And it will degrade your solvent."

At BASF, researchers tested 150 candidate solvents until settling on a few formulations. After setting a baseline with the RWE pilot, several months ago the firm began testing its first novel solvent, code-named "Gustaf 200." With Gustaf and several other candidates, Northemann said, BASF "is showing that the chemistry works. ... We're finely screening the results we had on the lab scale."

'People are in a hurry'

After the pilot, the next stage will be a demonstration system, which would cost several hundred million euros. RWE will decide later this year whether to move forward, Heithoff said, adding that he hopes to receive E.U. funds. Unlike its competitor, Vattenfall, RWE received no stimulus money.

Such a demonstration plant would be a "huge system," Heithoff said. The height would remain the same -- the 40 meters represents how much water/solvent mix the flue gas must bubble through for 90 percent of its CO2 to be captured -- but its width would increase exponentially. The quick scale-up proposed by RWE and other utilities is unusual in engineering, normally a conservative profession, Goetheer said.

"Because people are in a hurry, we need to scale up much faster" than normal, he said. Engineers can do it -- the rush to implement acid rain controls is a good example, he said -- but the first demonstration and commercial plants are going to be "tremendously expensive."

The costs of capturing CO2 will come down, and it is likely that in the future, better options than solvents -- physical adsorption, membranes -- will reach commercial use, Northemann said.

"I strongly believe that one day there will be something better than chemical absorption," he said. "No question about that."

But until then, the cost of post-combustion capture will be, along with public acceptance of CO2 storage, the major factor holding back carbon capture and storage, Goetheer said.

"The cost is not in storage. The cost is not in transport," he said. "The cost is in capture."