The International Energy Agency(IEA) recently said that if the world hopes to meet the targets set out in the Paris climate Agreement then, the deployment of carbon capture and storage(CCS) technology is necessary.
Fatih Birol, the IEA executive director, wrote in the foreword to 20 Years of Carbon Capture and Storage: Accelerating Future Deployment that “IEA scenario analysis has consistently highlighted that CCS will be important in limiting future temperature increases to two degrees Celsius, and we anticipate that this role for CCS will become increasingly significant if we are to move towards well below two degrees Celsius.”
Currently, Canada has 3 large-scale CCS projects in commercial operation, which includes SaskPower’s CCS facility at the Boundary Dam Power Station near Estevan, Saskatchewan, the Shell Quest project at the Scotford oilsands upgrader near Edmonton, and the Weyburn-Midale enhanced oil recovery projects operated by Cenovus Energy and Apache Canada.
Although CCS operators around the globe look to improve the existing technologies in the laboratory, scientists are constantly looking for the new wave of technology. Here are some of the technologies used for CCS.
1. Metal-organic frameworks
In the past few years, a class of highly absorbent, nanoporous materials called metal-organic frameworks (MOFs) have emerged as a promising material for carbon capture in power plants.
“People are really excited about these materials because we can make a huge variety and really tune them,” says Northwestern University’s Randall Snurr. “But there’s a flip side to that. If you have an application in mind, there are thousands of existing MOFs and millions of potential MOFs you could make. How do you find the best one for a given application?”
Snurr alongside his group have discovered a new way to rapidly identify top candidates for carbon capture by using just one per cent of the computational effort that was previously required. They achieved this by applying a genetic algorithm, they rapidly searched through a database of 55,000 MOFs.
One of the identified top candidates, a variant of NOTT-101, has a higher capacity for CO2 than any MOF reported in scientific literature for the relevant conditions.
“The percentage of carbon dioxide that the MOF can absorb depends on the process,” Snurr says. “The United States Department of Energy target is to remove 90 per cent of carbon dioxide from a power plant; it’s likely that a process using this material could meet that target.”
With their nanoscopic pores and incredibly high surface areas, MOFs are excellent materials for gas storage. MOFs’ vast internal surface areas allow them to hold remarkably high volumes of gas. The volume of some MOF crystals might be the size of a grain of salt, for example, but the internal surface area, if unfolded, could cover an entire football field.
Snurr says, “In places like China, where they are still building a lot of power plants, this would make a lot of sense.”
Cornell University materials scientists have invented low-toxicity, highly effective carbon-trapping “sponges” that could improve carbon capture economics.
A research team led by Emmanuel Giannelis, claims that they have invented a powder that performs as well as or better than industry benchmarks for carbon capture.
Today, the most common method to capture carbon is amine scrubbing, in which post-combustion, CO2-containing flue gas passes through liquid vats of amino compounds, or amines, which absorb most of the CO2. Then carbon-rich gas is pumped away—sequestered—or reused. The amine solution requires capital-intensive containment and is extremely corrosive.
Giannelis said solid amine sorbents are used in carbon capture but the supports are usually only physically impregnated with the amines. Slowly, over a long period of time, some of the amines are lost, decreasing effectiveness and increasing cost.
The researchers instead grew their amine onto the sorbent surface, leading cause the amine to chemically bond to the sorbents, meaning very little amine loss over time.
3. Hybrid membranes
The scientists at the Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a new highly permeable carbon capture membrane which could lead to more efficient ways of separating CO2 from power plant exhaust.
a graduate student in the chemical and biomolecular engineering department at the University of California, Berkeley and a user at the Molecular Foundry, Norman Su says, “In our membrane, some CO2 molecules get an express ride through the highways formed by metal-organic frameworks, while others take the polymer pathway. This new approach will enable the design of higher performing gas separation membranes.”
The scientists at Berkeley Lab have developed a hybrid membrane where MOFs account for 50 percent of its weight, which is about 20 percent more than other hybrid membranes. Previously, the mechanical stability of a hybrid membrane limited the amount of MOFs that could be packed in it.
“This is the first hybrid polymer-MOF membrane to have these dual transport pathways, and it could be a big step toward more competitive carbon capture processes,” says Su.
The Swedish scientists a new method of creating crystals that capture CO2 much more efficiently than previously known materials, even in the presence of water.
“As far as I know, this is the first material that captures CO2 in an efficient way in the presence of humidity. In other cases, there is a competition between water and CO2, and water usually wins. This material adsorbs both, but the CO2 uptake is enormous,” says Osamu Terasaki, a professor in the department of materials and environmental chemistry at Stockholm University.
The new material is known as SGU-29, which is named after Sogang University in South Korea and is the result of international cooperation. It is a copper silicate crystal. The material could be used for capturing CO2 from the atmosphere and especially to clean emissions.
“CO2 is always produced with moisture, and now we can capture CO2 from humid gases. Combined with other systems that are being developed, the waste carbon can be used for new valuable compounds. People are working very hard, and I think we will be able to do this within five years. The most difficult part is to capture CO2, and we have a solution for that now,” says Terasaki.
5. Turning carbon to rock
We might have found a permanent way of removing CO2 emissions from the atmosphere by turning it into the rock as reported by an international team of scientists.
The study has shown for the first time that CO2 can be permanently and rapidly locked away from the atmosphere by injecting it into volcanic bedrock. The CO2 reacts with the surrounding rock, forming environmentally benign minerals.
Until now, it was thought that this process would take several hundred or thousands of years and is therefore not a practical option. But the current study—led by Columbia University, the University of Iceland, the University of Toulouse, and Reykjavik Energy—has demonstrated that it can take as little as two years.
Juerg Matter, the lead author and associate professor in geoengineering at the University of Southampton, says: “Our results show that between 95 and 98 percent of the injected CO2 was mineralized over the period of fewer than two years, which is amazingly fast.”
“Carbonate minerals do not leak out of the ground, thus our newly developed method results in permanent and environmentally friendly storage of CO2 emissions,” says Matter, who also happens to be a member of the University’s Southampton Marine and Maritime Institute and an adjunct senior research scientist at Lamont-Doherty Earth Observatory at Columbia. “On the other hand, basalt is one of the most common rock types on Earth, potentially providing one of the largest CO2 storage capacity.
“The overall scale of our study was relatively small. So, the obvious next step for CarbFix is to upscale CO2 storage in basalt. This is currently happening at Reykjavik Energy’s Hellisheiđi geothermal power plant, where up to 5,000 tonnes of CO2 per year are captured and stored in a basaltic reservoir.”
6. Turning carbon into fuel
At the University of Southern California’s Loker Hydrocarbon Research Institute, they’re making fuel out of thin air. For the first time in history, researchers have directly converted CO2 from the air into methanol at relatively low temperatures.
The work led by G.K. Surya Prakash and George Olah from the chemistry department at USC Dornsife is a part of an effort to stabilize the amount of CO2 in the atmosphere by using renewable energy to transform the greenhouse gas into its combustible cousin, attacking global warming from two angles simultaneously. Methanol, which also happens to be a clean-burning fuel for internal combustion engines, a fuel for fuel cells, and a raw material used to produce many petrochemical products.
“We need to learn to manage carbon. That is the future,” says Prakash, the director of the Loker Hydrocarbon Research Institute, followed by, “The researchers bubbled air through an aqueous solution of pentaethylenehexamine, adding a catalyst to encourage hydrogen to latch onto the CO2 under pressure. They then heated the solution, converting 79 percent of the CO2 into methanol. Though mixed with water, the resulting methanol can be easily distilled.”
7. Turning carbon into fibres
Scientists have dreamt of finding a technology to shift CO2 from a climate change problem to a valuable commodity for a long period of time. Now, a team of chemists claims that they have developed a technology to economically convert atmospheric CO2 directly into highly valued carbon nanofibres for industrial and consumer products.
“We have found a way to use atmospheric CO2 to produce high-yield carbon nanofibres,” says Stuart Licht, who leads a research team at George Washington University. “Such nanofibers are used to make strong carbon composites, such as those used in the Boeing 787 Dreamliner, as well as in high-end sports equipment, wind turbine blades, and a host of other products.”
Licht calls his approach “diamonds from the sky”, which refers to carbon being the material that diamonds are made of and also hints at the high value of the products, such as the carbon nanofibres, that can be made from atmospheric carbon and oxygen.
At this time, the system is experimental, and Licht’s biggest challenge will be to ramp up the process and gain experience to make consistently sized nanofibres. “We are scaling up quickly,” he adds, “and soon should be in the range of making tens of grams of nanofibers an hour.”
Licht explains that one advance the group has recently achieved is the ability to synthesize carbon fibers using even less energy than when the process was initially developed. “Carbon nanofibre growth can occur at less than one volt at 750 degrees Celsius, which for example, is much less than the three to five volts used in the 1,000-degree-Celsius industrial formation of aluminum,” he says.
With Elon Musk announcing that he will be donating a prize of $100 million, we can surely lookout for more new techniques in the advancement of Carbon Capturing Technologies.