If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.



Carbon Dioxide As An Industrial Feedstock, For Real

Pilot project is stripping the greenhouse gas from a cement plant’s flue gas

by Jeff Johnson
November 17, 2014 | A version of this story appeared in Volume 92, Issue 46

Credit: John Davidson, Skyonic
Skyonic’s demonstration technology captures CO2 from an adjacent cement plant and uses the greenhouse gas to make sodium bicarbonate, sodium hypochlorite, and hydrochloric acid, for industrial applications.
A photograph of Skyonic Corp.’s addition to San Antonio Texas cement plant to capture CO2 to process and use for hydrochloric acid and sodium bicarbonate and bleach.
Credit: John Davidson, Skyonic
Skyonic’s demonstration technology captures CO2 from an adjacent cement plant and uses the greenhouse gas to make sodium bicarbonate, sodium hypochlorite, and hydrochloric acid, for industrial applications.

Discovering and applying technologies to turn carbon dioxide, a greenhouse gas, into usable, marketable products has long been a goal of researchers and green entrepreneurs. In recent weeks, a Texas company claims to have made that dream come true.

On Oct. 21, Skyonic, a technology developer in Austin, Texas, fired up an added-on system to capture and use CO2 from a portion of the waste stream of a 60-year-old coal-fired cement plant in San Antonio. The $125 million addition will capture 75,000 metric tons of CO2 annually from the cement plant and use it—along with saltwater and electricity—to make sodium bicarbonate, sodium hypochlorite, and hydrochloric acid.

Company officials claim that the project is the first to capture and use CO2 onsite as a raw material for manufactured products. They say their process is unlike other technologies that capture CO2 and inject it underground for storage or, in some cases, to enhance oil recovery. Skyonic has contracts in hand to make $48 million in annual sales to chemical distributors and $28 million in earnings, says Stacy MacDiarmid, the company’s communications director.

However, the sheer amount of CO2 emitted annually by U.S. power plants, motor vehicles, manufacturers, and other sources—more than 5 billion metric tons—limits the climate impact of the new technology. At this project, the new system will remove only 15% of the CO2 emitted by Capitol Aggregates, the cement plant. And moving the technology beyond pilot scale may be a challenge. Several critics say bicarbonate and hydrochloric acid markets in the U.S. aren’t large enough to support multiple plants.

But the project represents a significant advance on a path that might eventually lead to widespread industrial use of captured CO2 emissions. “This is more than a green technology,” said Skyonic Chief Executive Officer Joe Jones when he announced the company’s project, called SkyMine. “It is a profitable, smart business decision that makes money. It is the first step in our vision to mitigate the effects of industrial pollution and close the carbon cycle.”

Skyonic received some $28 million in Department of Energy grants for SkyMine through the American Recovery & Reinvestment Act, according to Energy Secretary Ernest Moniz. Other investors include venture capital firms, petroleum conglomerates—including ConocoPhillips and BP—as well as manufacturers, such as General Electric, and the energy company NRG.

The company’s history of getting DOE support stretches back to 2010. That’s when Skyonic first gained federal funding and was one of a handful of technology developers that were pursuing technologies to capture and use CO2 in industrial products.

Skyonic’s technology was designed for existing plants that burn fossil fuels, and it potentially has applications for coal- and gas-fired industrial plants in many sectors, including glass and steel as well as cement, according to Moniz.

DOE and Skyonic also argue that by using the gas as a raw material for making products, the technology has the potential to eliminate CO2 emitted when traditional raw materials are manufactured or mined. In addition, the new process cuts the amount of air pollution emitted from coal-fired facilities.

To create the chemical products it’s selling, the company’s technology includes a small chlor-alkali operation that splits a solution of sodium chloride and water via electrolysis to produce chlorine, hydrogen, and sodium hydroxide—also known as caustic soda. Chlor-alkali plants traditionally are big users of electricity, consuming 2% of the world’s electricity, but MacDiarmid says Skyonic’s facility is small and efficient.

CO2 from the cement plant is captured by reacting flue gases with aqueous sodium hydroxide from the chlor-alkali facility, forming sodium bicarbonate. The hydrogen and chlorine are used to make hydrochloric acid, and the remaining chlorine is reacted with sodium hydroxide to form sodium hypochlorite, which is used in chlorine bleach.

After the CO2 is removed, the cement plant’s flue gas is cooled from about 125 °C to 35 °C through two heat exchangers and then enters a condenser where nitrogen oxides, sulfur oxides, and mercury and other heavy metals are pulled out.

Currently, Skyonic has no plans to scale up its operations at the cement plant, MacDiarmid says. “We don’t own the cement plant. We just run postcombustion flue gas over to our facility for treatment,” she says.

Skyonic is a technology developer, she underscores. “We will ultimately be in the business of licensing a family of similar technologies.”

The market for the technology and its products is global, MacDiarmid says, and if the technology takes hold and leads to more installations, new markets and uses may result from more products. Globally, cement generates between 3.5 and 5% of all CO2 emissions, both directly through the calcination of limestone and indirectly through fuel and electricity, according to federal figures.

When it began the project, the company hoped the U.S. would set a price on CO2 emissions. But that didn’t happen.

“Carbon pricing doesn’t have to come for us to be successful,” MacDiarmid says. “But the advantage is we have time to run and improve operating in a real-world situation right now, so when there is a price on carbon emissions or a carbon trading regime, which is probably inevitable, we will be well ahead of the game. We will be established and have operating facilities, and we will have developed our secondary technologies that much further.”

The project’s importance is its focus on curbing industrial emissions, says John Thompson, director of the Fossil Transition Project of the Clean Air Task Force, a nonprofit that supports greenhouse gas reduction technologies. Industrial sources generate about one-quarter of global CO2 emissions, or about 8 gigatons a year Thompson notes.

“If Skyonic’s technologies are profitable and are applicable to the growing industrial sector, this will be a really big deal,” he says.

However, Thompson notes, “there are no sodium bicarbonate or HCl markets large enough to make an impact on global warming.” But Skyonic is developing another technology that leads from this project and could result in mineralization of CO2 into a solid calcium carbonate to more permanently lock up CO2,Thompson says.

“We need more options to address industrial greenhouse gas emissions, and this could be one of them. If the company can build a few more facilities and make some money, it could move to this second technology. That I am excited about.”  


This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.