The three pathways of carbon capture and removal

Buying emission allowances through the Compliance Carbon Markets (CCMs) is an immediate step to reduce atmospheric carbon in a quantifiable, verifiable way. However, this action alone is not sufficient to achieve corporate sustainability or reach the collective goal of limiting global warming to 1.5 degrees Celsius above pre-industrial levels, as outlined in the Paris Agreement. For an enduring impact, carbon dioxide removal (CDR) strategies hold the key.

All CDR projects have, at their core, the same goal of removing historical carbon emissions from the atmosphere and sequestering the carbon long-term so that it cannot continue to exacerbate climate change. Innovative carbon removal technologies are in development and show promise for massive environmental upside.

As CDR gathers increasing political and financial support, organizational leaders need to understand the landscape of emerging solutions and how they can inform and complement their own sustainability initiatives. Yet unlike some tangible-yet-problematic voluntary offset programs, CDR is tough to imagine. Carbon removal technologies are so varied; what can we expect CDR to look like? How can we expect CDR to function?

Each project is, of course, distinct. Yet it helps to categorize different approaches. At Climate Vault, we conceptualize three pathways for understanding different forms of CDR implementation: terrestrial, technological, and oceanic.

The terrestrial pathway

CDR projects in the terrestrial pathway take place on land and utilize natural geologic, ecologic, or biologic processes. These projects often focus on agricultural systems, as plants are fantastic at grabbing atmospheric carbon via photosynthesis and storing it in their biomass and in soil.

Incredibly, carbon that plants store in the soil will be held there until the soil is disturbed or the plant ultimately dies and decays, releasing its stored carbon back into the atmosphere. To this end, some terrestrial CDR projects emphasize low- or no-till agricultural practices and educate farmers on the carbon benefits of this approach. Other approaches include cultivating plants that are more efficient at absorbing and retaining carbon in their biomass and root systems.

The CDR projects that make the largest impacts take these issues into account in development, closely evaluating the permanence and the social & ecological impacts of the technology and developing monitoring practices to trace the long-term removal of carbon.

As additional benefits, these projects often improve soil quality and water quality and can help restore ecosystems that have been damaged as a result of overfarming or deforestation.

These secondary benefits create immediate, tangible value for surrounding communities, which are often at the receiving end of the negative impacts of climate change.

The oceanic pathway

Projects within the oceanic pathway utilize or enhance our planet’s largest natural carbon sink. This pathway offers many different promising projects, like ocean alkalinity enhancement (OAE) and macro algae (kelp) growth and sinking. OAE projects seek to change the acidity of the water so that it can absorb more CO2, and projects with algae seek to use the fast-growing aquatic plants to absorb and ultimately store carbon on the ocean floor.

As with many CDR technologies, a major drawback to oceanic projects is their nascency—there is still much work to be done to confirm that the projects achieve net carbon removal and do not have unintended negative impacts on the surrounding ecosystem. However, oceanic projects also show perhaps the greatest promise—the ocean is capable of absorbing so much carbon that projects on this pathway may have the deepest untapped potential.

Oceanic projects can also aid in ecosystem rehabilitation. Enhancing the ocean’s alkalinity through OAE projects could help to address the ecological effects of acidification, like coral reef loss and calcifier (shellfish and the like) population decline. Just as with the terrestrial pathway, pursuing projects in the ocean would not only address the global climate crisis, but also confront immediate issues of ecosystem collapse.

The technological pathway

The technological CDR pathway includes, essentially, all engineered solutions that don’t rely on natural environmental processes. Two frequently discussed technological CDR strategies are direct air capture with carbon storage (DACCS) and bio-energy with carbon capture and storage (BECCS).

DACCS involves—at the risk of upsetting swaths of engineers with a giant oversimplification—giant vacuums that suck in air, separate the CO2 from other molecules in the air, and stash the CO2 deep underground. BECCS involves converting biomass into heat, electricity, or fuel, capturing the carbon emissions that result from the biofuel combustion, and storing the CO2 deep underground or in long-lived products.

A common criticism of engineered solutions is that these CDR technologies may actually emit more carbon (in the form of the energy required to run the machines) than they sequester. This question regarding a project’s lifecycle emissions matters when evaluating any CDR project’s net carbon impact, but is especially pertinent with technological pathways.

Many such projects are not yet carbon negative at the moment, but that target is inherently part of their mission. Any innovative CDR program not yet beyond carbon neutral will have to justify its feasibility and outlook as part of attracting investors, grants, and other funding sources.

Projects like bio-based construction materials walk the line between technologic and terrestrial: such programs sustainably grow and manage forests and then harvest and process the wood to be used as structural building materials. The wood takes the place of conventional concrete and steel, which are more carbon-intensive to produce.

CDR is the future

Although CDR solutions can be more challenging to grasp conceptually than carbon offset programs such as tree planting, there are an array of CDR solutions that offer significant potential for addressing the climate crisis.

In our view, the most successful CDR strategies do not simply remove atmospheric carbon effectively; they also focus on the permanence of carbon removal (how long the carbon is stored), which is often measured in decades or centuries; additionality, which means that the project would not have taken place without a market for carbon removal credits; and leakage, meaning the extent to which the project causes emissions to occur elsewhere, often as a result of displacing existing markets, products or resources.

Advancing CDR projects across all three pathways can make a serious dent in climate change. We need multiple reliable and quantifiable approaches to remove and store carbon at scale. All three pathways are important, as we’ll need a mosaic of scalable approaches to solve the global climate crisis, not just a single static solution.


To learn more about how you & your company can leverage immediate carbon allowances into long-term CDR strategies, reach out to the team here at Climate Vault. We’re here to help you reduce & remove your carbon and meet your sustainability goals—for good.

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