CCS most commonly stands for carbon capture and storage, a set of technologies designed to trap carbon dioxide emissions at their source and lock them away underground before they reach the atmosphere. The term also appears in medicine, where it can refer to chronic coronary syndrome or central cord syndrome, and in cardiology grading systems. This guide covers all the major meanings so you can find the one you’re looking for.
Carbon Capture and Storage
Carbon capture and storage is a three-step process: capture CO₂ from industrial exhaust or power plant flue gas, transport it (usually by pipeline), and inject it deep underground into geological formations where it stays permanently. The goal is to prevent large volumes of CO₂ from entering the atmosphere, particularly from sources that are difficult to decarbonize any other way.
The International Energy Agency identifies four major sectors that depend on CCS for deep emissions cuts: heavy industry like cement and steel production, power generation, low-emissions hydrogen production, and direct air capture. By 2030, the global project pipeline could reach roughly 95 million tonnes of CO₂ captured annually from hydrogen production, 90 million tonnes from power plants, 50 million tonnes from industrial facilities, and 65 million tonnes from direct air capture plants.
How CO₂ Is Captured
There are three main approaches to capturing CO₂, and each one works at a different point in the fuel-burning process.
- Post-combustion capture pulls CO₂ out of exhaust gases after fuel has been burned. This is the most common approach for existing coal and natural gas plants, but it’s also the most challenging because CO₂ makes up only 3 to 15 percent of the exhaust stream. Treating that large volume of gas is expensive. Analysis from the National Energy Technology Laboratory found that adding 90% capture to a new coal-fired power plant would raise the cost of electricity by about 66 percent, from roughly 6.5 cents per kilowatt-hour to nearly 10.7 cents.
- Pre-combustion capture converts fuel into a mixture of hydrogen and CO₂ before burning it. Because the CO₂ concentration in this mixture reaches around 40 percent at high pressure, it’s easier and potentially cheaper to separate than in post-combustion flue gas.
- Oxyfuel combustion burns fuel in nearly pure oxygen instead of regular air. The resulting exhaust is mostly CO₂ and water vapor, making capture simpler since there’s far less nitrogen to deal with.
Where the CO₂ Goes
Once captured, CO₂ is compressed and transported, typically through pipelines, to a storage site. The U.S. Department of Energy is investigating five types of underground formations for permanent storage:
- Saline formations: deep, porous rock layers filled with brine. These span large volumes underground and represent the biggest potential storage capacity.
- Depleted oil and gas reservoirs: formations that already held hydrocarbons for thousands to millions of years, which means the geology is naturally suited to trapping fluids.
- Unmineable coal seams
- Organic-rich shales
- Basalt formations
Depleted oil and gas reservoirs are particularly appealing because their geology is already well-mapped from decades of extraction, and they’ve proven they can hold pressurized fluids over geological timescales.
Chronic Coronary Syndrome (Cardiology)
In cardiology, CCS can refer to chronic coronary syndrome, a term that replaced “stable angina” or “stable coronary artery disease” in recent European guidelines. The 2024 European Society of Cardiology definition describes CCS as a range of clinical presentations caused by structural or functional problems in the coronary arteries or the tiny blood vessels of the heart muscle. These problems create a mismatch between how much blood the heart muscle needs and how much it actually receives, typically during physical or emotional stress.
The guidelines identify five patient groups under the CCS umbrella:
- People who previously had a heart attack or stent procedure and are now stable
- People with heart failure linked to reduced blood flow or metabolic disease
- People who experience predictable chest pain or reduced blood flow during exertion, caused by a narrowed coronary artery
- People with chest pain caused by spasms or tiny-vessel dysfunction, even though their main coronary arteries look clear on imaging
- People with no symptoms whose coronary artery disease is discovered incidentally on an imaging scan
CCS Angina Classification Scale
CCS also stands for the Canadian Cardiovascular Society classification system, a widely used scale that grades chest pain (angina) severity from Class I to Class IV based on how much physical activity it takes to trigger symptoms.
- Class I: Angina only during strenuous, rapid, or prolonged exertion. Normal daily activities like walking and climbing stairs cause no symptoms.
- Class II: Slight limitation. Symptoms occur when walking rapidly, walking uphill, climbing stairs quickly, or during physical activity after meals, in cold weather, wind, or emotional stress.
- Class III: Marked limitation. Even walking one or two blocks at a normal pace on flat ground or climbing a single flight of stairs triggers symptoms.
- Class IV: Inability to perform any physical activity without discomfort. Symptoms can occur at rest.
This scale helps clinicians track whether a person’s condition is worsening or improving over time, and it’s commonly referenced in medical records and research studies.
Central Cord Syndrome (Spinal Cord Injury)
Central cord syndrome is the most common type of incomplete spinal cord injury, affecting roughly 11,000 people per year in the United States. It typically results from a hyperextension injury to the neck, where the head is forced backward sharply. This motion compresses the spinal cord from both the front (by bone spurs or disc material) and the back (by a ligament that lines the spinal canal).
The hallmark of central cord syndrome is a distinctive pattern of weakness: the arms and hands are affected far more severely than the legs. A person may struggle to grip objects or use fine motor skills in the hands while still retaining significant leg strength. Bladder function is also commonly affected, typically causing urinary retention. Earlier theories attributed the damage to bleeding inside the central spinal cord, but more recent studies point to disruption of nerve fibers in the outer white matter tracts that carry movement signals from the brain, particularly those controlling the upper limbs.
Because this is an incomplete injury, meaning the spinal cord is damaged but not fully severed, many people retain some function and have the potential for meaningful recovery. Lower limb function tends to return first, followed by bladder control, and then upper extremity strength. Fine hand movements are typically the slowest to recover and may remain partially impaired long term.