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Learning To Love CO2

Companies and academics seek out profitable pathways to materials made from the unwanted gas

by Alex Scott
November 16, 2015 | A version of this story appeared in Volume 93, Issue 45

A rainbow appearing above a pair of smoke stacks.
Credit: Shutterstock/C&EN

Lothar Mennicken proudly tugs at a badge on his lapel that states, “I love CO2.” Mennicken, the senior scientific officer for the German Federal Ministry of Education & Research, wants to dispel the notion that CO2 is only a “problem” chemical that causes global warming. He says it should also be considered an abundant, low-cost raw material.


Carbon capture and usage (CCU) developers are competing against petrochemical processes.

Number of CCU technologies in development worldwide: >250

Amount of CO2 that would be consumed yearly if the chemical industry were CO2-based: 300 million metric tons

Amount of CO2 generated by human activity last year: 35 billion metric tons

Cost of capturing and storing CO2: $50 to $100 per metric ton

XPrize Foundation’s prize for technologies that capture CO2 and turn it into high-value products: $20 million

Cost of making methanol from CO2: $1,500 per metric ton from natural gas: $400 per metric ton

Cost of making formic acid from CO2: $2,900 per metric ton from natural gas: $775 per metric ton

Germany’s investment in CCU R&D: $110 million between 2010 and 2016

Amount of CO2 that would be consumed yearly if the transportation fuels industry were CO2-based: 12 billion metric tons

Amount of CO2 generated by coal-fired power plants last year: 14 billion metric tons

CCU = carbon capture and usage.

SOURCES: German Ministry of Education and Research, University of York, European Commission, United Nations, CRI, C&EN

Converting waste CO2 into useful products or fuels also cuts emissions to the atmosphere, Mennicken says. Thus, in recent years, his department has invested more than $100 million into research projects that aim to make chemicals and fuels from CO2.

This practice, known as carbon capture and usage, or CCU, faces skepticism because large amounts of energy are needed to break the CO2’s carbon-oxygen bonds. Converting CO2 into useful chemicals typically requires hydrogen, which can be expensive to produce. And even widespread adoption of CCU is not likely to have a big impact on climate change.

“When I began working with carbon capture and usage projects five years ago, people more or less laughed at me,” Mennicken says.

But because it doesn’t rely on fossil fuels, CCU could be a more sustainable way of making chemicals and other materials. It could also play an important role in energy storage by harnessing excess renewable energy, such as that from wind turbines on a blustery day, and, in effect, storing it in the form of chemicals or fuels.

A growing number of chemical processes that use waste CO2 have hit the market or are getting ready to launch. If a step up in public funding for R&D were to combine with sympathetic government policies, CCU could quickly overcome cost hurdles and move from niche to mainstream, proponents say. And a policy shift could be triggered as early as December at the United Nations climate summit in Paris if participating nations agree to stringent controls on CO2 emissions.

Companies and academics in Denmark, Germany, Switzerland, the U.K., and the U.S. are currently among the leading developers of CCU technologies.

Mennicken’s agency will spend $110 million on CCU R&D projects between 2010 and 2016 to help bridge the gap between the lab and commercialization. An additional $55 million is coming from German industry. Together the investments have funded 33 collaborations, leading to the development of more than 150 individual CCU projects in Germany. Worldwide, more than 250 CCU projects are under development.

Tens of millions of dollars more in funding is set to be available in Germany in the coming years. In Europe more broadly, a similar amount will be spent on CCU via Horizon 2020, the European Union’s R&D program, which runs through 2020.

Policies fostering CCU also are being developed in the U.S., where the Environmental Protection Agency is now looking at the technique as a tool for reducing CO2 emissions. EPA recently indicated that it may allow certain CCU technologies to be used to cut CO2 emissions from power plants under its Clean Power Plan.

Prospective CCU technologies that already have benefited from German funding include the “dream reaction,” in which CO2 is used as a raw material to make polyurethane. The process was codeveloped by RWTH Aachen University and Covestro, formerly Bayer MaterialScience.

In the second half of 2016, Covestro intends to open a plant in Dormagen, Germany, that will produce up to 5,000 metric tons per year of polyols, a polyurethane intermediate. About 20% of the content of the polyols will be from waste CO2 captured from a nearby ammonia plant.

In Covestro’s process, CO2 is reacted with propylene oxide in the presence of a zinc-based catalyst to make polyols. Initially, the polyols will be used to make foam mattresses. The process uses another intermediate that can be derived from methanol, which in the future could also be made from waste CO2, Covestro says.

The facility is set to cost about $17 million. The new process will be economically viable once it is at commercial scale, insists Christoph Gürtler, who manages the project.

Covestro is also developing variants of the CO2-consuming reaction to make other polymers, including materials made from unsaturated polyethercarbonate (PEC) polyols. PEC, for example, can be used to produce cross-linked films that are resistant to solvents, Gürtler says. “It’s a new class of material.”

The Covestro plant will be an example of what can be achieved and should inspire other firms, says Gürtler, who predicts that additional CO2-based processes will emerge across the chemical industry. “CO2 will become a reasonable and profitable raw material,” he says.

Although Covestro is breaking new ground, it is hardly the first company to convert CO2 into useful chemicals. The Kolbe-Schmitt synthesis for producing salicylic acid using CO2 is more than 150 years old. And sodium bicarbonate has long been produced by reacting CO2 and sodium carbonate.

But the largest-volume CO2-based reaction is the Bosch-Meiser process, which combines CO2 and ammonia to make urea. It was introduced in 1922. About 100 million metric tons per year of urea is produced today using the process, consuming roughly an equal amount of CO2.

A more sustainable version of the Bosch-Meiser process may soon be introduced on the island of Shapinsay, near the north coast of Scotland. Assisted by project partners that include the University of Sheffield, the island’s 300 inhabitants plan to use excess energy generated by their wind turbine to power a proton-exchange membrane electrolyzer that will create hydrogen.

Credit: enCO2re project / Technical University of Berlin’s Centre for Entrepreneurship

Explore this interactive map of more than 150 carbon capture and usage projects across the world.

The partners plan to react the hydrogen with CO2 emitted from the island’s whiskey distillery to form carbon-neutral synthetic diesel. Hydrogen also will be combined with nitrogen captured from the air to make ammonia. The ammonia will then be reacted with CO2 to form urea.

“No one can see why it wouldn’t go ahead,” says Katy Armstrong, network manager for U.K.-based CO2Chem, a network of 1,100 academics, industrialists, and policy-makers from around the world. Energy storage is the main driver for the project, she says.

Indeed, CCU backers say the technology could solve the problem of fluctuations in output from renewable energy sources such as wind and solar farms. Excess electricity can drive CO2-based chemical reactions to produce a chemical or fuel that stores the energy.

Used this way, CCU could encourage the deployment of renewable energy, says Michael Carus, head of the Nova Institute, a German firm that provides technical information on biomaterials and CCU.

Like the Scottish islanders, the German technology developer Sunfire also seeks to store excess renewable energy in the form of chemicals. It has developed a solid-oxide fuel cell to generate hydrogen, which it reacts with waste CO2 to make hydrocarbon fuels. When renewable electricity is in short supply, such as on cloudy or windless days, the process can be reversed so that the fuel is converted back into electricity.

“It is for grid stabilization. It is not able to replace fossil fuel,” says Christian von Olshausen, chief technology officer for Sunfire. The firm started up a pilot facility in November 2014 and recently secured an order from Boeing for a 120-kW reversible solid-oxide fuel-cell system.

Unlike the Shapinsay project, for which electricity will be free, Sunfire will have to pay for electricity to make hydrogen. In general, von Olshausen expects that CO2-based fuels will always be more costly than fossil fuels and require financial support. “If we don’t have regulation to support renewable fuels, then we won’t have a business case,” he says bluntly.

The cost of making hydrogen is a wrench in the business case of the Dutch CCU start-up Antecy. It plans to react waste CO2 with hydrogen generated from the photovoltaic-powered electrolysis of water to make methanol.

But if Antecy is to come close to matching the price of standard methanol, it will have to cut its electrolyzer costs by a factor of two or three, says Timo Roestenberg, the firm’s R&D manager. Antecy doesn’t yet have that technology. “If the cost doesn’t go down, then what are we going to do? I know that is not a good answer,” Roestenberg says.

CCU firms that plan to generate hydrogen face a formidable challenge, according to Mar Pérez-Fortes, a postdoctoral researcher for the Joint Research Centre, a research unit of the European Commission (EC).

Primarily as a result of energy costs associated with water electrolysis, CCU methanol would cost more than $1,500 per metric ton, she calculates, compared with about $400 via the standard natural-gas-based route. Similarly, producing a metric ton of formic acid via a CO2-based route would cost $2,900, versus $745 via the petrochemical route, she says.

“The only solution is to have electricity at price zero,” Pérez-Fortes says. “More R&D is required, coupled with renewable energy.”

Pictured is a methanol plant in Iceland.
Credit: CRI
CRI uses low-cost geothermal and hydro energy in Iceland to profitably turn waste CO2 into methanol.

CCU proponents point to Iceland’s Carbon Recycling International, a producer of CO2-based methanol that has developed a way to get hydrogen at low cost. CRI’s trick is to generate the 800 metric tons of hydrogen it needs per year by powering its three electrolyzers with the cheap geothermal and hydro energy that is available in Iceland.

CRI has developed an efficient, low-temperature catalyst that turns hydrogen and CO2 into water and methanol. The methanol is distilled, and the water is recycled.

CRI now wants to establish itself in mainland Europe. As a step toward this goal, it has joined a consortium funded by the Horizon 2020 research program to build a 400-metric-ton-per-year methanol plant in Lünen, Germany. The demonstration facility, which is slated to start up in 2017, will have access to CO2 and waste heat from a nearby coal-fired power plant.

It won’t have the low-cost energy of Iceland and it won’t be profitable, but on the basis of the wholesale price of energy in Germany in 2014, the Lünen plant would have broken even for 70% of the year, says Benedikt Stefánsson, CRI’s business development director. And when a European law comes into effect in 2020 that requires 10% of transport fuel to be derived from renewable sources, CRI expects to be in a strong competitive position.

Bedford, Mass.-based start-up Joule Unlimited has a radically different technology for making fuels and chemicals based on photosynthetic cyanobacteria. The process doesn’t require splitting water to generate hydrogen, yet Joule still expects to need government intervention if it is to bridge the gap from demonstration phase to commercial success.

Joule’s technology involves pumping engineered cyanobacteria in transparent tubes so they can convert sunlight, waste CO2, and nonpotable water directly into fuels such as ethanol and kerosene, or into C12 fatty acids similar to those derived from palm or coconut oil.

No sugars or chemical additives are used to make the fuels, which are separated from the water by distillation. “We are trying to industrialize photosynthesis,” says Kees van der Kerk, the firm’s director of business development.

U.S. academics’ solar mat aims to become the complete solution

Credit: Joint Center For Artificial Photosynthesis
Lewis’s experimental technology converts solar energy along with water vapor and CO2 from the air to generate useful chemicals.
Credit: Joint Center For Artificial Photosynthesis


Lewis’s experimental technology converts solar energy along with water vapor and CO2 from the air to generate useful chemicals.


Credit: Joint Center For Artificial Photosynthesis
Lewis’s experimental technology converts solar energy along with water vapor and CO2 from the air to generate useful chemicals.

A researcher at the Joint Center for Artificial Photosynthesis in Pasadena, Calif., is developing the ultimate solution to the problem of CO2: a solar-powered mat that takes CO2 and water vapor from the air and converts them directly into useful chemicals or fuels.

Credit: Joint Center For Artificial Photosynthesis
Lewis’s experimental technology converts solar energy along with water vapor and CO2 from the air to generate useful chemicals.

Nathan S. Lewis, principal investigator and a professor of chemistry at California Institute of Technology, has been working on the process for almost five years. “We need to do what nature does and use the biggest energy source—sunlight,” Lewis says.

Credit: Joint Center For Artificial Photosynthesis
Lewis’s experimental technology converts solar energy along with water vapor and CO2 from the air to generate useful chemicals.

Using lessons from photosynthesis, Lewis’s team has developed a polymer mat made of a silicone or a fluoropolymer into which is fixed a grasslike array of microwires made from silicon.

Credit: Joint Center For Artificial Photosynthesis
Lewis’s experimental technology converts solar energy along with water vapor and CO2 from the air to generate useful chemicals.

Applying a nanometer-thick layer of titanium dioxide onto the wires prevents them from oxidizing but still enables them to absorb light and lets electrons pass through. Applying nanometer-thick spots of a catalyst such as nickel to the surface of the TiO2 effectively splits water vapor from the air into hydrogen and oxygen, while still allowing light to reach the silicon wires. A membrane separates the oxygen from the hydrogen.

Credit: Joint Center For Artificial Photosynthesis
Lewis’s experimental technology converts solar energy along with water vapor and CO2 from the air to generate useful chemicals.

Initially, Lewis is developing a hydrogen-producing system. But by applying different catalysts, the system could split CO2 from air to form carbon monoxide and oxygen. The carbon monoxide could then be combined with the hydrogen to generate a target chemical or fuel.

Credit: Joint Center For Artificial Photosynthesis
Lewis’s experimental technology converts solar energy along with water vapor and CO2 from the air to generate useful chemicals.

“There is nothing else like it in the world,” says Lewis, whose team includes chemists, chemical engineers, and materials scientists. Subject to approval from Congress, the project is set to receive annual funding of $15 million for another five years.

Credit: Joint Center For Artificial Photosynthesis
Lewis’s experimental technology converts solar energy along with water vapor and CO2 from the air to generate useful chemicals.

Lewis is at an early stage of costing the prototype system but says the technology could generate hydrogen for as little as $2.50 per kg. This compares with $1.60 per kg for hydrogen generated by the steam reforming of methane, the current industrial approach. In contrast, a photovoltaic panel coupled with an electrolyzer produces hydrogen for more than $10 per kg, Lewis says.

Credit: Joint Center For Artificial Photosynthesis
Lewis’s experimental technology converts solar energy along with water vapor and CO2 from the air to generate useful chemicals.

“It feels like it has potential to be cost-effective,” he says.

Joule has a team of 135 employees and a demonstration facility in Hobbs, N.M., that consumes CO2 emissions from a cement factory. The firm plans to open a 1,000-acre facility in 2017. “We are very confident that we will be commercial in two years,” van der Kerk says.

Joule has raised $200 million in private equity and venture debt financing. At this point, however, the firm’s technology is uncompetitive. Joule estimates that its first commercial plant will produce fuels for $3.00 to $8.00 per gal, compared with $1.50 per gal via traditional routes. “So we need some kind of bridging finance,” van der Kerk acknowledges.

Down the road, chemistry can also provide cost-effective CCU technologies that avoid the need for hydrogen, argues Michael North, professor of chemistry at the University of York.

In North’s lab, the target molecules are CO2-based cyclic carbonates, which have applications in solvents, polymers, chemical intermediates, and electrolytes for lithium-ion batteries. They were commercialized in the 1950s by what is now Huntsman Corp.

Typically, cyclic carbonates are generated in the presence of halide-based catalysts under high pressure and temperature. In a bid to make the process cheaper and more user-friendly, North and his team have successfully made the carbonates in the lab at room temperature using aluminum catalysts complexed with a salen ligand.

North’s project is part of CyclicCO2R, a four-year research program funded by the EC. CyclicCO2R supports a team of 20 scientists with $4 million in funding from the commission and $1.5 million from industrial partners including Evonik Industries and Iceland’s CRI.


Although North’s chemistry may yet lead to economically viable products, the case for consuming enough waste CO2 to have a meaningful impact on global warming appears to be weak. More than 14 billion metric tons of waste CO2 is produced around the world just from coal-fired power stations. An entirely CO2-based chemical industry would need only 300 million metric tons of this, North says.

As a result, not everyone is bullish on CCU. One doubter is Niall Mac Dowell, a chemical engineer who leads the Clean Fossil & Bioenergy Research Group at Imperial College London.

“The only sensible thing to do with CO2 is sequester it” underground, a concept known as carbon capture and storage, or CCS, Mac Dowell says. “When it comes to investing in measures to prevent climate change, very possibly CCU could even be a distraction from the real task at hand of implementing CCS projects.”

CCS costs between $50 and $100 per ton of CO2, with large up-front capital costs. Unlike CCU, it makes no industrial chemical to offset its costs. But CCS’s lack of an end product should not make it less attractive than CCU, Mac Dowell says. After all, society’s goal should be to stop global warming, not make money from selling chemicals.

Others say CCU should be taken beyond chemicals and fuels. Large volumes of CO2, they claim, could be stored for long periods by locking it up in mineral blocks used in construction.

U.K. start-up Carbon8 Aggregates has already commercialized a method of making building aggregates using waste CO2. And the business is profitable, according to Managing Director Paula Carey.

Carbon8 combines CO2 with waste residues, including ash from municipal incinerators and energy plants. Under tightly controlled reaction conditions, the CO2 is rapidly absorbed by the residues in the presence of water to form calcium carbonate.

The calcium carbonate is then mixed with fillers and binders to produce pellets in a drum pelletizer where more CO2 is added to carbonate the binder. Most of these pellets end up in blocks used in building and construction.

In addition to generating sales from its final product, Carbon8 is able to charge suppliers of its waste residues up to $190 per metric ton, which is less than they would have to pay to put their material in landfills.

Carbon8 currently treats 25,000 metric tons of residues and consumes 2,000 metric tons of CO2 per year at a facility in Brandon, England. The CO2 is purified from the waste stream of a sugar beet factory 20 miles from the Carbon8 plant.

Ironically, CO2 represents 25% of Carbon8’s costs. “It is very expensive as we have to buy high-purity CO2. We cannot liquefy impure gas,” Carey says.

The firm is about to commission a new plant near Bristol, England, that will treat 40,000 metric tons of residues and consume 4,000 metric tons of CO2. Carbon8 is planning three more sites in the U.K. in the next two years. “We have also had a lot of interest from outside the U.K., including from the U.S.,” Carey adds.

Europe’s emissions trading system (ETS), which puts a value on CO2 emissions savings, could in theory give European CCU firms such as Carbon8 a leg up. But CO2 credits are in oversupply in the ETS market, and the price of the waste gas is not expected to rise above $20 per metric ton until 2020 at the earliest, analysts say.

More favorable European CCU policies are likely to crystallize in the next year or so, according to Andreas Pilzecker, a senior administrator in the EC’s transport policy unit. If UN member countries agree to stringent CO2 reduction targets at the Paris climate change summit starting later this month, policies and investment that support CCU could follow, Pilzecker says. The EU’s objective is to reduce CO2 emissions up to 40% by 2030.

Regardless of what happens in Paris, a range of public and private funding options will be available for CCU technology developers, particularly in the U.S. and Europe.

In addition to traditional project funding, the EC is offering $2.3 million to European companies that can demonstrate a CCU technology. In a similar competition, California-based XPrize Foundation is offering a $20 million prize for technologies that capture CO2 and turn it into high-value products.

Such prizes should help put waste CO2 in a new, more favorable light, says Peter Styring, director of the U.K. Centre for Carbon Dioxide Utilisation at the University of Sheffield. “It’s a good way of getting the idea out there and will get people thinking; $20 million is not to be sneezed at,” Styring says.

But not every technology can win a prize. And given the dearth of new commercially proven technologies, CCU developers have their work cut out convincing policy-makers, scientists, and the public that their approach to CO2 reduction is worthwhile. Mennicken of the German research ministry shouldn’t take his badge off quite yet. ◾


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