Durability - the length of time carbon is removed from the atmosphere - is for many market participants becoming the central factor when assessing the integrity of carbon dioxide removal (CDR). Frontier, the CDR fund spearheaded by Stripe, has a strict criteria that any recipient of funding must have at least 1,000 years of durability.
But why, I hear you ask, are we fixated on storage that lasts longer than the Bayeux Tapestry? Why an entire millenia? Why not 500 years, or 200 years?
It is worth saying: high durability removal is good. Where possible, it should be valued alongside other key measures of quality such as additionality, over-crediting risk, policy environment and leakage risk, all of which are assessed in the BeZero Carbon Rating.
But shorter term removals should not be overlooked. Temporarily sequestered carbon buys us time. Time in which our ability to mitigate and adapt to climate change will continue to evolve. We may be able to deal with the impacts of emissions much more easily in 40 years than we are today. There is logic in judging present day emissions from a present day perspective, but we should not preemptively judge future re-emissions by this same logic.
Internationally agreed upon climate targets recognize this fact. Our short term targets are in the next three decades and are based on current emission practices. The focus on 2030 targets is because current governments can actually do something about them, even if they choose not to.
If we do not hit the 2030 targets, the 2050 ones become even harder to hit and we will depend more on solutions that do not exist yet. There is some research that focuses on end-of-century targets, but we almost never look at time-horizons greater than 100 years. It is the medium term that both scientific communities and governing bodies prioritise.
The criteria being set by private sector players on very high durability (1,000 to 10,000 years) could even reduce the funding available to shorter durability CDR. Biochar producers, for instance, are being excluded from Frontier even though by historical standards they are of high durability (over 100 years).
This barrier to entry is also an environmental justice issue. Less durable methods, such as biochar and afforestation, are often favourable to nations with weaker institutional structures that are looking to enter carbon markets as a means of economic development and need capital to get CDR off the ground.
Shorter-term removal methods often have lower overall costs which allows for rapid and cheap deployment in the near future. Our desire for very high durability removal may mean perfect being the enemy of the good, especially given that the rest of the climate community is not thinking in such distant terms.
Putting the argument on shorter versus long-term durability aside, there is no evidence that 1000 or 10,000 years durability will even become a reality. The scientific framework for long-term removal lacks precedents that exist beyond 100-year timescales. Some gases have been stored underground successfully for almost 100 years, but there is no data suggesting these human managed reservoirs will last more than 1,000 years. Those claims come from naturally occurring gas deposits that have been there for milenia. It is true, their presence is a solid hypothetical basis for 1,000 years of durability, but this is not synonymous with observable fact.
Despite all of this, investing in long term removal is still crucial. Relying solely on shorter-term removal would just kick the emissions problem down the road for subsequent generations. Instead, we need to invest in and develop a combination of removal options that bring a variety of players to the CDR landscape and help the planet reach relevant medium-term climate targets.
So, yes we want solutions with 1,000 years or more of durability. But, we also desperately need solutions that are 500, 200, 100 and 50 years of carbon storage. In short, let's stop fixating on ultra-high durability and just start removing that carbon.
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