Sequestering means capturing, isolating, or storing a substance so it can’t move freely or cause harm. The term shows up across very different fields, from climate science to medicine to chemistry, but the core idea is always the same: something is removed from circulation and locked away. How that works in practice depends entirely on the context.
Carbon Sequestration and Climate
The most common use of “sequestering” today refers to pulling carbon dioxide out of the atmosphere and storing it somewhere long-term. Carbon dioxide is the most commonly produced greenhouse gas, and carbon sequestration is one strategy for slowing climate change by reducing how much of it remains in the air.
There are two broad approaches. Biological sequestration relies on living systems: forests, peat marshes, coastal wetlands, and soils. Plants absorb carbon dioxide during photosynthesis and store carbon in their tissues, from long-lived tree bark to deep root systems. Cropland soils alone can sequester roughly 0.25 to 1.0 metric tons of carbon per hectare each year, depending on farming practices. Pastures store less (0.10 to 0.175 metric tons), while permanent crops and urban green spaces can match cropland rates. The ocean is an even larger player, sequestering an estimated 5 to 10 gigatons of carbon annually through a mix of physical absorption and biological processes.
Geological sequestration takes a more engineered approach. Carbon dioxide is pressurized into liquid form and injected into porous rock formations deep underground. This is sometimes paired with oil recovery: the liquid CO2 reduces the thickness of oil in aging wells, making it flow more easily while simultaneously storing the carbon below the surface. The Intergovernmental Panel on Climate Change stipulates that a properly chosen storage site should retain 99% of its CO2 over a 1,000-year period. For a site holding 200 million metric tons, that translates to a maximum acceptable leak of roughly 5.5 tons per day. Every injection project is required by the EPA to include monitoring of both the deep reservoir and the near-surface environment (water, air, and soil) to catch any leaks early.
How Your Body Sequesters Metals
Your body uses sequestration constantly, though you’d never call it that. Iron is essential for survival, but free-floating iron generates harmful molecules called free radicals that damage cells and organs. A protein called ferritin solves this problem by trapping iron atoms inside a shell-like structure, converting them into a stable, stored form. This keeps iron available when your body needs it while preventing oxidative damage in the meantime.
Ferritin also plays a role in fighting infection. When bacteria invade, they need iron to grow and reproduce. One of your body’s defense strategies is to pull iron out of circulation and lock it away inside cells, starving the invaders. This broader strategy is called nutritional immunity, and it goes well beyond iron.
Your immune system sequesters zinc and manganese the same way. When immune cells detect bacteria, they actively pump zinc and manganese out of the compartments where pathogens are trapped. A protein called calprotectin, released by white blood cells, binds manganese and zinc in the tissue surrounding an infection site. Imaging studies of staph infections have shown that abscesses are essentially devoid of detectable manganese, while the healthy tissue around them is full of it. The bacteria are effectively starved of the metals they need to survive. Adding excess manganese or zinc back reverses the growth inhibition, confirming that metal starvation is the mechanism at work.
Chemical Sequestration in Industry
In chemistry, sequestering usually involves chelating agents: molecules that grab onto metal ions and hold them in a stable complex, effectively removing those metals from whatever reaction or process they’d otherwise participate in. The most familiar example is EDTA, a compound used in everything from water softening and food processing to medical detoxification and household detergents.
EDTA works against bacteria by stripping away the calcium and magnesium ions that hold bacterial cell walls together, weakening the outer membrane. This principle has practical applications in wound care, where chelating agents can be combined with antibiotics to break down bacterial biofilms. The same basic chemistry applies in industrial settings: paper manufacturing, textile production, soil remediation, and wastewater treatment all rely on chelating agents to sequester unwanted metal ions.
Pulmonary Sequestration as a Medical Condition
In medicine, the word takes on a more anatomical meaning. Pulmonary sequestration is a condition where a mass of lung tissue develops with its own blood supply but no connection to the airways. Because it can’t exchange air, the tissue is nonfunctional. It receives blood from an abnormal artery rather than from the normal pulmonary circulation.
There are two types. Intralobar sequestration sits inside the lining of the normal lung, most often in the lower left lobe. It accounts for 75% to 86% of all cases. Extralobar sequestration has its own separate lining and its own venous drainage into systemic veins rather than the pulmonary veins. Intralobar sequestration typically shows up as recurrent pneumonia or lung infections in the same spot, since the trapped tissue can become a breeding ground for bacteria. Extralobar sequestration is more often detected in infants, sometimes even before birth when ultrasound reveals a lung mass, excess amniotic fluid, or fluid around the lungs.
Diagnosis requires confirming that the abnormal tissue has its own arterial blood supply, which is typically done through imaging. Recurrent pneumonia in the same area of the lung, especially the left lower lobe, is one of the key clinical clues.
The Common Thread
Whether the context is a forest absorbing atmospheric carbon, your immune cells starving bacteria of zinc, a chelating agent grabbing calcium ions in a water treatment plant, or a segment of lung tissue walled off from the airway, the underlying concept is isolation. Sequestering always means taking something out of play: removing it from its usual environment and holding it in a contained state. The purpose varies (protecting the climate, fighting infection, purifying water, describing an anatomical anomaly), but the mechanism is fundamentally about separation and storage.