• MIT Professor Angela Belcher and graduate student Roberto Barbero are working on a way to convert carbon dioxide gas to carbonates that could be used as building materials.

    Photo: Patrick Gillooly

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  • Carbon dioxide is bubbled into a solution of mineral ions.

    Photo: Patrick Gillooly

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  • Carbon dioxide combines with the mineral ions to form solid carbonates.

    Photo: Patrick Gillooly

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Putting carbon dioxide to good use

MIT biological engineers have found a way to convert carbon-dioxide emissions to useful building materials, using genetically altered yeast.


Every year, about 30 billion metric tons of carbon dioxide are pumped into the Earth’s atmosphere from power plants, cars and other industrial sources that rely on fossil fuels. Scientists who want to mitigate carbon dioxide’s effects on global climate have started experimenting with storing the gas underground, a process known as carbon sequestration. However, there are still many unknowns surrounding the safety and effectiveness of that strategy.

MIT engineer Angela Belcher is now taking a new approach that would not only remove carbon dioxide from the environment, but also turn it into something useful: solid carbonates that could be used for building construction.

“We want to capture carbon dioxide and not put it underground, but turn it into something that will be stable for hundreds of thousands of years,” says Belcher, the W.M. Keck Professor of Energy.

By genetically engineering ordinary baker’s yeast, Belcher and two of her graduate students, Roberto Barbero and Elizabeth Wood, have created a process that can convert carbon dioxide into carbonates that could be used as building materials. Their process, which has been tested in the lab, can produce about two pounds of carbonate for every pound of carbon dioxide captured. Next, they hope to scale up the process so it could be used in a power plant or industrial factory.

Biological inspiration

To create the yeast-powered process, Belcher drew inspiration from marine animals that build their own rock-solid shells from carbon dioxide and mineral ions dissolved in seawater. (Her 1997 PhD thesis focused on the abalone, a sea snail that produces exceptionally strong shells made of calcium carbonate.)

Funded by the Italian energy company Eni, the new MIT process for turning carbon dioxide into carbonates requires two steps. The first step is capturing carbon dioxide in water. Second, the dissolved carbon dioxide is combined with mineral ions to form solid carbonates.

Yeast don’t normally do any of those reactions on their own, so Belcher and her students had to engineer them to express genes found in organisms such as the abalone. Those genes code for enzymes and other proteins that help move carbon dioxide through the mineralization process. The researchers also used computer modeling and other methods to identify novel proteins that can aid in the mineralization process.

“We’re trying to mimic natural biological processes,” says Belcher. But, “we don’t necessarily want to make the exact same structure that an abalone does.”

Some companies have commercialized a process that captures carbon dioxide and converts it to solid material, but those efforts rely on a chemical process to capture carbon dioxide. The MIT team’s biological system captures carbon dioxide at a higher rate, says Barbero. Another advantage of the biological system is that it requires no heating or cooling, and no toxic chemicals.

Next, the team plans to try scaling up the process to handle the huge volumes of carbon dioxide produced at fossil-fuel-burning power plants. If the process is successfully industrialized, a potential source for the mineral ions needed for the reaction could be the briny water produced as a byproduct of desalination, says Barbero.


Topics: Bioengineering and biotechnology, Carbon dioxide, Carbon sequestration, Chemistry and chemical engineering, Materials science, Eni, MIT Energy Initiative (MITEI)

Comments

Count me as unconvinced. Klaus Lackner, now of Columbia University, tried for years to perfect mineral carbonation. While using a biocatalytic approach to encourage the carbonation reaction seems like a step in the right direction, this article leaves several unanswered questions. --To my knowledge, water is a poor chemical for absorption of CO2. This is why liquids such as MEA or chilled ammonia are commonly used to capture CO2 from a plant's flue gas. --The energy balance for this process is unclear: the mining and milling of rare earth metals (such as magnesium and calcium), thermal activation of the biochemical process, and the heat necessary for dewatering the carbonate could all be substantial. Typically, these costs make carbonation even less economically competitive than other sequestration options. --The logistics of the carbonate production are a nightmare. A common coal plant emits >100,000 tons of CO2 per year. To capture ~80% of this CO2, >150,000 tons of carbon material would have to be produced and stored each year.
Speaking as an experienced chemical engineer, the energy usage of this would have to be looked at on a larger scale. It is likely a very good candidate for some of the energy efficiency approaches that are becoming more in vogue. For example, waste heat recovery from a power plant (e.g., via stack economizer or other approaches) might be used to drive cooling of the water solution (absortion cooling, adsorption cooling, or steam jet cooling) in order to improve the ability to capture more CO2. Careful energy integration will likely be needed to make this viable. In a nutshell, just because something works in a laboratory beaker does not mean that it is economically viable on a large industrial scale. A pilot plant scale version of this would be a great next step.
Where does the calcium to make billions of tons of calcium carbonate come from?
Any balanced chemical reaction for production of carbonate ion (whether as a solid, or in solution) from CO2 involves production of acid. What would be the fate of the acid produced from this process at a commercial scale?
Im thinking along the lines of reforming CO2 into useful products (refinery). Strip it out of the atmosphere with membrane techology. Then reform in to useful products. The energy reqired could come from many sources. Whereas there are massive reserves of CO2 just waiting to be picked out of the air we breath. Simple! Also thinking alone the lines of doing this on a massive scale. This would be a low pressure system. Do not trouble yourselves with with material heat balance aslong has you put the spent energy recovery to good benifical use. No aged 51 years I commission some of the worlds largest projects. However I do like the way people are thinking on this blog. Kind Regards GT Look up Refinery Reforming Gas!
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