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Calcium Looping (CaL)


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An efficient and flexible carbon capture technology using a natural sorbent

Carbon capture is a valuable option in many emissions-generating industries. Calcium looping (CaL) makes use of the absorbent qualities in calcium to remove carbon from various flue gases. It also produces a useful by-product for the cement and lime industry.


CaL is an oxy-fuel-based post combustion capture technology and requires a dual Circulating Fluidized Bed (CFB) unit configuration. The flue gas from the emission source meets the sorbent, calcium oxide, in the first fluidized bed (carbonator), where it mineralizes into calcium carbonate and the flue gas exits clean of CO2 from the unit. The calcium carbonate is then directed to an oxy-fuel calciner, in which it’s regenerated back to calcium oxide, in the presence of fuel and oxygen.

The product CO2 from the calciner is of high purity, after drying suitable for storage or utilization. And the calcium oxide is circulated back to the carbonator to close the ‘loop’.

The process uses a nature-based sorbent, that’s not toxic or costly. And the existence of lime or calcium cycles in existing industrial infrastructure allows for integrated capture concepts, significantly reducing the carbon capture energy penalty compared to other post combustion solutions.

Not only CO2 is captured, but additional heat and power are generated as the system can be integrated with a subcritical steam cycle. And, as is typical with any post-combustion capture solution, a certain amount of the sorbent needs to be purged from the system to release any build-up of impurities. With CaL, the purged stream is calcined lime with ash and minerals, considered a by-product and renewable feedstock candidate for the cement and lime industry.

CaL has been piloted in MWth scale at several facilities with a wide range of bio-residues and waste-derived fuels. Similar our other CFB solutions, the technology is scalable and can take advantage of the oxygen synergy with green hydrogen installations.

Flexible and efficient

  • Calcium looping achieves high capture efficiency % with a low energy capture penalty.
  • CaL can accommodate challenging industrial flue gas conditions such as high temperature and presence of other impurities.
  • The solution can be delivered as stand-alone tail-end solution or integrated into various processes.

Clean and versatile

  • The technology uses a natural sorbent, sustainably sourced to capture CO2 and doesn’t involve producing, using or disposing of highly toxic materials or solvents.
  • As well as a high purity CO2 gas stream, CaL can produce a sorbent stream which could be used in cement plants.

With a broad range of applications across sectors, calcium looping is an extremely useful tool in the set of technologies that will help us get to net zero. Key synergies can be found in pulp and paper mills, waste-to-energy, cement and lime plants, as well as both blast and electric arc furnace plants in the steel industry.