Carbon Capture, Utilization and Storage (CCUS) Technology
Carbon capture, utilization and storage — or CCUS — technologies capture CO2 produced during industrial processes before it escapes into the atmosphere, helping meet climate goals more effectively. They play a pivotal role in energy mixes designed to reach environmental sustainability objectives.
Today, CCUS is predominantly used to extract carbon dioxide from flue gases at power plants and factories that make materials like concrete and steel, before storing them underground.
Post-Combustion Capture
Global warming is driven primarily by an accumulation of carbon dioxide (CO2) released into the atmosphere from fossil fuel combustion. Carbon capture and storage technology seeks to limit global warming effects by sequestering CO2 in deep geologic formations.
Post-combustion carbon capture is an advanced method for extracting CO2 from fossil fuel exhaust gases. The process starts by treating flue gas composed of carbon dioxide, nitrogen and oxygen to eliminate any species that might interfere with its operation; after which it comes in contact with a solvent–usually an aqueous amine solution–which absorbs only CO2, leaving other gases behind to be released back into the environment.
CO2 captured through post-combustion carbon capture is compressed for transport to its geologic storage site. Two large power plants with post-combustion carbon capture systems currently operational include Boundary Dam and Petra Nova.
Direct Air Capture
DAC technologies use carbon dioxide capture technologies to directly remove it from the atmosphere, prepare it for storage or utilization and make use of its stored or generated CO2. There are currently 27 operational DAC plants around the world with another 130 in various stages of development.
Earth’s natural ecosystems have already removed much of the carbon from its atmosphere through processes such as photosynthesis. Unfortunately, human activity has added carbon faster than natural systems can absorb it; experts are therefore exploring ways to augment nature by speeding up carbon removal from both air and ocean environments through planting trees or developing larger-scale capture methods.
Direct air capture differs significantly from post-combustion and oxyfuel capture by using solid or liquid sorbent materials to remove carbon from ambient air directly, rather than by taking CO2 from flue gasses. Though energy-intensive, direct air capture can still be located on non-arable land so as to avoid competition with food crops for agricultural production while decreasing water usage; and further avoiding carbon emissions associated with power and industrial facilities construction projects.
Oxyfuel Capture
This technology captures CO2 at its source: fossil fuel power plants, natural gas- and coal-powered factories that produce steel and concrete products, ethanol plants. CO2 from such facilities are then stored permanently underground rather than being released back into the atmosphere.
Under the oxyfuel process, most of the nitrogen in flue gas is extracted via air separation, leaving behind carbon monoxide (CO) and hydrogen (H2). A chemical solvent then binds CO2 for near pure CO2, while H2 can then be used to power a steam turbine that generates electricity.
CO2 is compressed and chilled down into a liquid for transport. This liquid form can then be injected into oil wells where it helps extract more crude from underground. Alternatively, it could be stored underground geological structures. CCS technology of this nature has already been successfully deployed at some industrial projects.
Enhanced Oil Recovery
Carbon dioxide capture and storage technologies can help enhance the efficiency of fossil fuel energy plants as well as decrease emissions from cement and steel production facilities.
EOR is an oil recovery method using captured CO2 to increase oil recovery from existing wells. Carbon dioxide is injected into geologic reservoirs under certain conditions and interacts with oil residue to displace it from rock pores – similar to how solvents might displace grease on bicycle chains.
Once captured, CO2 is compressed and deep chilled before being transported through pipelines or ship, rail, or road tanker for permanent underground storage. At present, over 30 projects using CO2 for EOR exist globally with another 153 underway or planned – projects which play an essential part in meeting climate targets.
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