An illustrated guide to carbon removal  

Posted: April 04, 2025

Carbon dioxide removal—the practice of removing and permanently storing CO2 from the atmosphere—has been gaining traction as a promising fix for the climate crisis. The Intergovernmental Panel on Climate Change now says it is unavoidable to achieve net zero emissions, alongside deep emissions cuts, and it could become a trillion-dollar industry by 2050.

Carbon removal differs significantly from carbon capture, which traps emissions from factories or power plants and thus avoids emitting more greenhouse gases into the air. But even carbon removal contains a wide range of vastly different approaches, from restoring forests to burying biomass and giant vacuums that suck CO2 out of the air. Here are some of the most prominent nature-based and technological solutions that companies and scientists are researching and trialing around the world.

Afforestation and reforestation

Establishing new forests or restoring original forest cover where it has been lost—due to natural disasters or logging, for example—stores carbon the old-fashioned way: through photosynthesis. Agroforestry practices such as planting native trees on agricultural lands, as well as improved forest management, can also help remove carbon from the atmosphere.

Peatland and wetland restoration/coastal revegetation

Similar to tree planting, rewetting natural carbon stores such as peat bogs or replanting coastal mangroves can help lock away carbon for decades to centuries. Peatlands, in particular, have a big impact: despite only covering a tiny share of the world’s landmass, they contain almost half of all soil carbon and more CO₂ than is stored in all other vegetation types combined. 

Direct air capture

One of the most prominent technological approaches to carbon removal, direct air capture involves purpose-built industrial facilities that use solvents to filter carbon out of the air like giant vacuums. For maximum impact, the captured carbon is buried in geological stores, but it can also be used in various industries.

Biochar

Using pyrolysis, biomass, such as residual wood or crop waste, is converted at high heat into a more stable form. This highly porous material can help improve water retention and nutrient availability when added to soils, but may also be mixed into construction materials, such as biochar cements.

Bioenergy with carbon capture and storage

This process involves capturing and permanently storing CO₂ from processes where sustainable biomass is converted into fuels or directly burned to generate energy. Examples include process emissions from biofuel and biohydrogen production, or capturing emissions directly at the smokestack of heat and power plants that run on biomass. 

Enhanced rock weathering

Pulverized carbonate or silicate rock can be spread on land, typically crop fields, where it reacts with carbon dioxide to form stable bicarbonates. The bicarbonates are washed out into streams and rivers over time and eventually settle as ocean sediments, providing long-term storage. The process on land has the beneficial side effect of lowering soil acidity, which can improve plant health and boost nutrient availability.

Soil carbon sequestration

Adopting more sustainable agricultural practices and pasture management can help reverse a major source of emissions: turning natural ecosystems into farmland. For example, farmers can add more carbon to agricultural soils by planting certain perennial crops that grow deep roots and store more carbon. Cover crops, planted after harvest, can also take in carbon dioxide year-round and even add the stored carbon to the soil once they’re plowed under. 

Ocean alkalinity enhancement

Adding alkaline materials such as carbonate or silicate rock to the sea could supercharge the—very slow—natural process by which the oceans already absorb carbon dioxide from the air through air-sea gas exchange. Raising the water’s alkalinity means more CO₂ from the atmosphere is converted into stable bicarbonate and carbonate molecules, which in turn causes the ocean to absorb more CO₂ from the air to restore equilibrium. 

Direct ocean capture

Direct ocean capture operates on the same principles as ocean alkalinity enhancement but instead involves removing dissolved carbon directly from seawater using a range of electrochemical processes, such as electrolysis or electrodialysis. After removing the carbon in special facilities, the alkaline water is released back into the ocean where it naturally absorbs more CO₂ from the atmosphere.

Ocean fertilization

Adding nutrients such as iron or nitrogen to the upper, sunlit layers of the ocean can stimulate the growth of phytoplankton, tiny marine plants that perform photosynthesis and form the base of the marine food web. Phytoplankton stimulation can also be achieved by a technique known as artificial upwelling and downwelling whereby deep and relatively nutrient-rich waters are churned up to the surface ocean, and biomass-rich water is in turn pumped down.

Macroalgae cultivation

Macroalgae, or, as it's more commonly known, seaweed, can be used in several ways to store carbon in the sea or on land. Farmed or wild algae can take sequestered carbon with them when they sink, be harvested to create biochar, or be compressed and intentionally sunk to the deep ocean for permanent sequestration—a process known as intentional biomass sinking. For a similar effect, the seaweed can even be buried in landfills or in the desert.