Why invest in both long and short term carbon removal solutions?

Short-term carbon removal methods, which are often nature-based, offer immediate scalability and provide co-benefits for society and the environment. At the same time, highly permanent carbon storage solutions, such as geologic storage, require immediate funding for scaling. Which to choose? We recommend responsibly investing in both types of solutions, thereby aligning with the Oxford Offsetting Principles.

What is the difference between short-term and long-term carbon storage?

The concept of permanence, or durability, is central to effective carbon removal. Durability denotes the longevity of carbon sequestration within a carbon sink. Yet, this is influenced by the risk of reversal—the potential for disruption and subsequent release of carbon dioxide into the atmosphere.

For instance, carbon stored in mineral form within rock is durable with minimal risk of reversal, unlike carbon dioxide pumped into rock as a gas that could be disturbed. Trees are fairly durable, storing carbon for decades to hundreds of years, but are at a higher risk of reversal in the event of something like a forest fire.

Different carbon removal methods have different levels of durability (how long the carbon is expected to be stored for) and different levels of reversal risk (how likely is the carbon to slowly or abruptly leak back to the atmosphere).

Nature-Based Solutions Hybrid Solutions Engineered Solutions
Storage duration: 50-100 years Storage duration: 100s-1,00s of years Storage Duration: >10,000 years
Trees store carbon in their leaves and woody biomass. When they eventually die and decompose, this carbon is sequestered in the soil. Some solutions utilise natural processes in tandem with human intervention, e.g., trapping carbon in biomass via pyrolysis—the process of creating biochar. Technology has made it possible to capture carbon directly from the air and store it deep underground, through methods like direct air capture and storage.
There is typically a high risk of reversal for nature-based solutions. For example, forest fires cause the carbon stored in biomass to be immediately returned to the atmosphere. For hybrid solutions, such as biochar or biomass burial, there is typically a small but tangible reversal risk, as a portion of the carbon stored in the material will eventually return to the atmosphere. The reversal risk for engineered solutions depend on storage location. For CO2 stored underground as gas or liquid, there is a low but not negligible risk of leakage, whereas CO2 in mineralised form has no risk of leakage.
Nature-based solutions operate on timescales of 50-100 years. This is a long time as compared to person’s lifetime, but carbon dioxide can remain in the atmosphere for up to 10,000 years. These solutions can store carbon for hundreds to thousands of years. This is long-term carbon storage on a geological time scale (from thousands of years to over 10,000 years).

Combining methods is necessary to combat climate change

Engineered CDR solutions hold enormous potential to reach our global climate targets by amplifying long-term geological reservoirs. However, these solutions require a long-term outlook. The technologies behind them are still nascent and require significant research and investment to reach gigaton scale, which will take decades.

Nature-based carbon storage acts as a very effective buffer in the meantime. Forests already store vast amounts of CO2 and forestation has the capacity to be scaled massively, although land is a finite resource, so it is important to consider where and how to reforest. In addition, forestry is a well-established carbon removal method with proven results and a high degree of knowledge about risk factors and limitations. But, it requires large amounts of land, a major constraint to scale–especially in the face of climate change.

Canyon Waterfall

The case for scaling nature-based carbon removals

It is possible to link nature-based solutions and tech-driven CDR solutions in sequence to maximise overall climate impact and socio-environmental benefits. This mix-methods approach can also diversify risk and balance cost.

This strategy, termed 'horizontal stacking', helps account for the delay in permanent carbon credit availability, while making sure investment still reaches tech-driven carbon removal projects.

By the time carbon stored in less permanent sinks like forests is about to be re-released, the more energy-intensive engineered solutions will be sufficiently scaled to be able to absorb this CO2 once again.

There is evidence to show that nature-based removals has the potential to reduce peak warming in the shorter term, as long as they are employed alongside strong emissions reduction efforts [1].

Taking the long view:
Investing in carbon removals for maximum climate impact

It’s important to strike the right balance between climate impact and important co-benefits in every portfolio. After all, sequestering carbon is important but carbon tunnel vision—i.e., ignoring all other factors—is not feasible, as carbon removal does not occur in a closed system. You can simultaneously invest in long-term removal, supporting the development of the future market, while deploying methods that are readily available at present.

Scaling and diversifying the market through increased investment and commitment from governments and companies are crucial steps toward achieving global net zero, but they aren’t the whole picture. Upholding our common climate goals of the Paris Agreement demands a comprehensive approach that extends beyond carbon removal to tackle the underlying causes of climate change.

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