Carbon removal is any process that pulls carbon dioxide (CO2) out of the atmosphere and locks it away in long-term storage, whether in soil, rock, the ocean, or underground geological formations. It’s different from simply reducing emissions: carbon removal actively reverses some of the CO2 already accumulated in the air. Most climate models agree that cutting emissions alone won’t be enough to meet global temperature targets, making carbon removal a necessary complement to decarbonization.
How Carbon Removal Differs From Carbon Capture
The two terms sound interchangeable but describe different things. Carbon capture and storage (CCS) typically refers to grabbing CO2 at the source, such as the smokestack of a power plant or cement factory, before it ever reaches the open atmosphere. In those flue gases, CO2 makes up 4 to 30 percent of the mixture, which makes it relatively straightforward to separate.
Carbon removal, by contrast, targets CO2 that is already dispersed in the atmosphere, where it accounts for just 0.04 percent of the gas mixture. That massive dilution makes capture far more technically challenging and energy-intensive. The key distinction: CCS prevents new CO2 from entering the atmosphere, while carbon removal subtracts CO2 that’s already there. Only removal can achieve what scientists call “net-negative” emissions.
Nature-Based Approaches
The simplest forms of carbon removal rely on biology. Trees, grasses, and agricultural soils absorb CO2 through photosynthesis and store it as organic carbon. Reforestation and improved land management are the most widely deployed methods today, largely because they’re inexpensive and provide co-benefits like habitat restoration and flood control.
Coastal ecosystems are especially powerful. Mangroves and salt marshes pull carbon from the atmosphere at a rate roughly 10 times greater than tropical forests, and they store three to five times more carbon per acre. These “blue carbon” habitats lock carbon into waterlogged soils where decomposition is slow, keeping it sequestered for centuries under the right conditions. The catch is that nature-based storage is vulnerable: wildfires, drought, pest outbreaks, or land-use changes can release stored carbon back into the air in a matter of days.
Engineered and Geochemical Methods
Direct Air Capture
Direct air capture (DAC) uses large industrial facilities to chemically extract CO2 from ambient air. Fans draw air across materials that react with CO2, either solid sorbents that bond with it on their surface or liquid solutions (typically strong bases) that absorb it. Once the sorbent is saturated, heat or a vacuum is applied to release a concentrated stream of pure CO2, which can then be compressed and injected deep underground into geological formations for permanent storage. The regeneration step, heating the materials back up so they can capture more CO2, accounts for roughly 63 percent of the energy a DAC plant consumes. That energy demand is the technology’s biggest hurdle.
Enhanced Rock Weathering
When certain volcanic rocks like basalt dissolve naturally in rainwater, they react with CO2 and convert it into stable bicarbonates that wash into groundwater and eventually the ocean, where the carbon can remain locked away for thousands of years. Enhanced rock weathering speeds this process up by grinding the rock into a fine powder and spreading it on farmland, where warm temperatures and rainfall accelerate the chemical reactions.
Field experiments in Costa Rica using crushed basaltic andesite applied at 50 tons per hectare showed sequestration rates of 2.4 to 4.5 tons of CO2 per hectare per year. After subtracting the emissions from mining, grinding, and transporting the rock, the net removal rate came to about 3.2 tons per hectare annually. Scaled across half the country’s lowland agricultural soils, that single approach could offset 25 to 50 percent of Costa Rica’s annual CO2 emissions.
Bioenergy With Carbon Capture
This approach, often abbreviated BECCS, works in three stages. First, fast-growing plants or trees absorb CO2 as they grow. Then the biomass is burned to generate electricity. Finally, the CO2 released during combustion is captured and injected underground rather than vented to the atmosphere. Because the plants already pulled that carbon from the air during photosynthesis, and the combustion emissions are then stored permanently, the entire cycle produces energy while removing more CO2 than it emits.
Ocean-Based Techniques
Ocean alkalinity enhancement (OAE) involves adding dissolved minerals to seawater to increase its capacity to absorb and hold CO2. The ocean already absorbs about a quarter of human-caused CO2 emissions, and raising alkalinity could amplify that uptake. However, research published in Environmental Science & Technology highlights a fundamental tension: the more efficiently OAE draws down atmospheric CO2, the less it helps counteract ocean acidification for marine life. The biological benefits turn out to be species-specific and are only meaningful when the added alkalinity doesn’t trigger additional CO2 absorption. There is also concern about unforeseen ecological side effects, particularly near the point of alkaline addition, where mineral concentrations are highest. In short, ocean-based removal holds large theoretical potential but carries real ecological uncertainty.
How Long Does Storage Last?
Not all carbon removal is equally durable, and permanence is one of the most important distinctions between methods. Geological storage, where CO2 is injected into deep rock formations or converted into stable minerals, can keep carbon locked away for millennia. This is the kind of storage paired with DAC and BECCS.
Biological storage is far less predictable. Typical afforestation contracts for carbon credits require just 40 years of storage. Biochar (charcoal mixed into soil) degrades slowly but still decomposes over decades to centuries. A 2024 study in Nature’s Communications Earth & Environment argued that neutralizing fossil CO2 emissions, which persist in the atmosphere for thousands of years, requires storage on a comparable timescale. By that standard, planting trees alone cannot truly “cancel out” fossil fuel emissions, because the carbon in a forest is always at risk of re-release through fire, disease, or future deforestation. The researchers concluded that claims of carbon neutrality based on short-lived storage are fundamentally inconsistent with net-zero goals.
This doesn’t mean nature-based removal is useless. It means the climate benefit depends heavily on how long the carbon actually stays stored, and that biological and geological methods shouldn’t be treated as interchangeable.
What It Costs Today
Price varies enormously depending on the method. Nature-based solutions like reforestation and soil carbon management are the cheapest, often well under $50 per ton of CO2, though their permanence limitations apply. BECCS projects currently range from $75 to $300 per ton, with costs dropping significantly when paired with facilities that already produce concentrated CO2 streams, such as biorefineries, where removal runs $40 to $50 per ton.
Direct air capture is the most expensive. Current projects cost an estimated $500 to $1,900 per ton of CO2. Advances in capture materials and economies of scale could bring that down to around $300 per ton by mid-century, and some next-generation designs are targeting $100 per ton. For context, global CO2 emissions total roughly 37 billion tons per year. Even at $100 per ton, removing a meaningful fraction of that would represent an enormous financial commitment, which is why most experts view carbon removal as a supplement to emissions cuts rather than a replacement.
The Scale Challenge
Current carbon removal capacity is a tiny fraction of what climate models say is needed. Most pathways to limiting warming to 1.5°C or 2°C require billions of tons of CO2 removal per year by mid-century. Today, engineered removal operates at a scale of thousands of tons per year. That gap, roughly a factor of a million, represents the central challenge for the field: bringing costs down while scaling up infrastructure fast enough to matter within the next few decades. Nature-based methods already operate at larger scale but face limits in land availability and storage permanence. Closing the gap will likely require a portfolio of approaches rather than any single technology.