Carbon sequestration is broadly considered a necessary tool for slowing climate change, but it comes with real trade-offs depending on the method, the scale, and where it happens. No single form of carbon sequestration is purely good or purely bad. Nature-based approaches like forests and soil offer co-benefits but store carbon temporarily. Geological and technological approaches can lock away CO2 for millennia but are expensive and carry their own environmental risks.
What Carbon Sequestration Actually Does
Carbon sequestration is the process of capturing CO2, either from the atmosphere or from industrial sources, and storing it somewhere it won’t contribute to warming. The idea is straightforward: if we can pull carbon out of the air and keep it locked away, we reduce the concentration of greenhouse gases driving climate change.
There are two broad categories. Biological sequestration uses natural systems: trees absorb CO2 through photosynthesis and store it in wood, roots, and soil. Oceans hold dissolved CO2 in water and in carbonate sediments on the seafloor. Wetlands, bogs, and permafrost trap carbon by keeping it away from oxygen or slowing decomposition. Agricultural soils can also accumulate carbon when managed in certain ways, with scientists estimating that farmland alone could sequester over a billion additional tons of carbon per year.
Geological sequestration takes a more engineered approach. CO2 is compressed into a liquid-like state and injected deep underground into porous rock formations, where it fills tiny spaces in the rock, dissolves into surrounding fluids, and over centuries reacts to form stable minerals. One newer method dissolves CO2 into water before injecting it into basalt formations, where it mineralizes more quickly. About 45 commercial capture facilities operate globally today, with a combined capacity of more than 50 million tonnes of CO2 per year.
The Case for It
The strongest argument is simple math. Even with aggressive emissions cuts, many climate models show that the world will need to actively remove CO2 from the atmosphere to limit warming to safe levels. Carbon sequestration is one of the few tools that can do this at scale.
Nature-based sequestration comes with bonus benefits. Reforestation improves biodiversity, stabilizes soil, reduces flooding, and can improve local air quality. Healthy soils store more water and produce better crop yields. Coastal wetlands and mangroves protect shorelines from storms while pulling carbon from the atmosphere. These aren’t just climate solutions; they make ecosystems more resilient in ways people can see and feel.
Geological storage, meanwhile, offers something biological methods can’t: permanence. When CO2 dissolves into underground rock formations, it stays put for thousands of years. The process of solubility trapping, where CO2 dissolves into brine deep underground, unfolds over hundreds of years and becomes more secure with time as the CO2 eventually mineralizes into solid rock. For industries like cement and steel manufacturing that can’t easily eliminate emissions, capturing CO2 at the source and storing it underground may be one of the only viable paths to decarbonization.
The Risks Are Real
Biological sequestration has a fundamental vulnerability: it’s reversible. A forest that took decades to grow can burn in a wildfire and release its stored carbon in days. Droughts, disease, and land-use changes can do the same. Permafrost is already thawing as the planet warms, releasing carbon that had been locked away for thousands of years. Soil carbon can be lost quickly if farming practices change. So while nature-based methods are valuable, they don’t guarantee long-term storage the way geological methods can.
Geological storage carries different concerns. The degree of potential leakage from an underground reservoir depends on a long list of factors: the density and depth of any cracks or pathways in the rock above, the pressure inside the reservoir, the permeability of surrounding formations, and temperature conditions. Pipelines transporting compressed CO2 to storage sites also pose risks to nearby communities if they rupture. Research published in Nature Communications has examined how to quantify the security of geological storage, and while well-chosen sites appear very stable, the technology requires careful site selection and long-term monitoring.
Then there’s the ocean. The ocean already absorbs enormous amounts of CO2 naturally, but this has come at a cost. Since the industrial revolution, surface ocean water has become about 30 percent more acidic. That shift is already dissolving the shells of tiny sea snails called pteropods, an important food source for species ranging from krill to whales. Coral and oyster shells are weakening as fewer carbonate ions remain available for shell-building organisms. Even fish behavior changes in more acidic water: clownfish, for example, lose their ability to detect predators. Any sequestration strategy that adds more CO2 to ocean systems risks accelerating these problems, though some approaches like growing seaweed may actually help by absorbing CO2 locally.
Cost and Scale Challenges
Direct air capture, the technology that pulls CO2 straight from ambient air, currently costs between $500 and $1,900 per tonne of CO2 removed, according to the International Energy Agency. For context, global CO2 emissions are roughly 37 billion tonnes per year. The 50 million tonnes captured annually by all existing facilities represents a tiny fraction of what’s needed. Nature-based approaches are far cheaper per tonne but face limits on available land and long-term reliability.
Cost is expected to fall as the technology matures, similar to how solar panel prices dropped dramatically over two decades. But right now, carbon sequestration is expensive enough that it only makes economic sense with government subsidies, carbon pricing, or corporate commitments to offset emissions. Critics worry that high costs mean resources get diverted from proven, cheaper strategies like renewable energy deployment and energy efficiency improvements.
The Environmental Justice Dimension
Where carbon capture facilities get built matters. Industrial capture equipment is typically installed at fossil fuel power plants and factories, which are disproportionately located near low-income communities and communities of color. If those facilities extend the operational life of polluting plants, the local health burden continues even as global emissions may decrease. Air pollution, noise, and the risk of pipeline leaks are concentrated in specific neighborhoods rather than spread evenly.
Research on CCUS through a health equity lens has found that these technologies have the potential to both improve and worsen health disparities. Poorly planned projects in vulnerable communities could deepen environmental injustice while doing little to reduce net emissions. One alternative gaining attention is reactive carbon capture, which converts CO2 into useful chemicals on-site at industrial plants, eliminating the need for pipelines and distant storage sites entirely. This keeps the environmental footprint contained to existing industrial locations rather than spreading it across new communities.
So Is It Worth Pursuing?
Carbon sequestration is not a replacement for cutting emissions. That distinction matters because the biggest criticism of the technology is that it gives fossil fuel industries a reason to delay the transition to clean energy. If a coal plant can capture its CO2, the argument goes, why shut it down? This concern is legitimate, and some sequestration projects have been tied directly to enhanced oil recovery, where liquid CO2 is injected into oil fields to extract more petroleum, effectively using a climate tool to produce more fossil fuels.
But dismissing sequestration entirely ignores the reality that some emissions are extremely difficult to eliminate. Aviation, shipping, agriculture, and heavy industry will produce CO2 for decades even under the most optimistic transition scenarios. For those sectors, carbon capture and storage fills a gap that renewables alone cannot. And for the CO2 already in the atmosphere, some form of removal will likely be necessary to bring concentrations back to safer levels.
The honest answer is that carbon sequestration is good when it supplements emissions reductions, when storage sites are chosen and monitored carefully, when affected communities have a say in project siting, and when costs come down enough to operate at meaningful scale. It becomes problematic when it’s used to justify continued fossil fuel dependence, when risks are pushed onto vulnerable populations, or when it distracts from faster, cheaper climate solutions that are already available.