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A very common argument is that carbon removal will be in short supply, and therefore must be carefully allocated. For example, a recent paper by Grubert & Talati likened CDR to “conventional depletable resources”, to be used scarcely by governments, not by companies. But as I will show in this post, although a number of real-world factors constrain CDR, it is not a finite resource in the way for example land is. The main constraint for CDR isn’t depletable resources, but willingness to pay. If we wanted to, we could deploy orders of magnitude more CDR than we will ever need.
Using CDR today builds future capacity, it does not deplete it.
There are three different questions at play here. Is using CDR now depleting future CDR capacity? Is there a limit to how much CDR we can deploy? And what should the CDR capacity we have built at a certain stage best be used for?
For the first question, the answer is a resounding no. Using CDR today builds future capacity, it does not deplete it. For example, making biochar out of biomass waste that otherwise would have decomposed or been burnt saves zero CDR capacity for future needs. It uses a resource that otherwise would have gone to waste, not eating away from a limited pot of CDR. The same is true for almost all removal solutions aside from forestation. Demand for CDR removes carbon today, and creates the necessary capacity for later usage.
For the second question, we need to divide it into two. What's the theoretical limit for CDR, and what's the practical limit in the near-term? The theoretical limit is very high. We could deploy enormous amounts of CDR if we were willing to pay the costs. For example, imagine large fleets of nuclear power plants just running Direct Air Capture plants on top of geological storage in the desert of Oman, and other sparsely populated places with good storage capabilities. Storage of captured CO₂ underground is not a limiting factor either. In the long term, we have room for thousands of gigatonnes, one estimate puts it to 8000-55 000 Gt worldwide1. More than we will ever need.
What sets the practical limit? Mainly the number of actors that want to pay for removals. The main reason we would fail to deploy meaningful amounts of CDR is if too few entities were compelled to pay for it (in the short to medium-term supply chains, permitting, a trained workforce, etc also sets limits, but demand is the main thing that helps solve these hurdles). During the ramp-up phase of CDR, restricting the use of CDR will restrict its deployment.
During the ramp-up phase of CDR, restricting the use of CDR will restrict its deployment.
The third question, what CDR should be used for in the future, does not necessarily need to be answered now. When sufficient CDR capacity has been built, states could restrict the use of CDR for any form of offsetting, and force companies to reduce emissions closer to zero. For example, by limiting the amount of CDR allowed in a cap and trade program like the EU ETS. The point is that paying for CDR today builds the capacity that governments could allocate for whatever is deemed to be the best possible uses tomorrow.
