According to the Intergovernmental Panel on Climate Change (IPCC), carbon dioxide removal (CDR) refers to “technologies, practices and approaches that remove and durably store carbon dioxide (CO2) from the atmosphere.” CDR is now recognized in the climate science and policy communities as an essential component of efforts to meet the temperature targets of the Paris Agreement. Recent research projects that the world may need to remove a whopping ten gigatons of carbon dioxide annually by 2050 and up to 20 gigatons by 2100, in addition to rapid decarbonization of the world economy. 

Graphyte is a carbon dioxide removal start-up company backed by Breakthrough Energy Ventures, which Bill Gates helms. The company seeks to prevent biomass waste's rapid decomposition and associated carbon dioxide release, including from crops and forests. The company’s approach uses a process called “carbon casting” to dry and compress biomass waste into blocks, which, when buried underground, can lock up carbon dioxide for 1000 years. This approach is one of several options categorized in the field of carbon dioxide removal as “Biomass Carbon Removal and Storage,” or BiCRS. BiCRS’ approaches achieve carbon removal “when the carbon in plant biomass—which would otherwise be re-released to the air through natural decomposition processes—is captured and stored in materials or through geologic storage of CO2.”

Graphyte’s CEO penned a blog recently entitled "The Need for Speed.” The post amplified a critical theme in CDR policymaking: the need to accelerate the deployment of carbon removal substantially approaches if they are to prove fit for purpose to meet the vision for the sector outlined in the IPCC's Sixth Assessment Report. I do not, however, concur with one of the blog’s overarching premises, that “[w]e need to prioritize investment in CDR approaches that are ready to deliver now. Because if we don’t scale fast, we are going to fail slow.” 

I believe that the author’s conclusion that this counsels in favor of focusing on investment in biomass burial rather than purportedly “early-stage approaches like direct air capture” seems highly questionable on several grounds. 

First, given the highly imposing amounts of carbon removal that are required by 2050 and 2100, I think society’s focus in terms of investment and policy has to be on approaches that can realistically result in multi-gigaton removals over this century and which require substantial infusions of investments to drive demand. I think this necessarily counsels in favor of prioritization of investment in approaches such as direct air capture, an option that can remove carbon dioxide from ambient air, which can then be stored geologically or converted into products. While the Graphyte blog post argues that its BiCRS approach could, in 2025, “deliver 50,000 tCO2e and be one of the largest carbon removal projects in the world,” this is dwarfed by the potential for direct air capture in the next few years. 

Moreover, in the longer term, as the National Academies of Sciences, Engineering, and Medicine concluded, direct air capture is one of the few technical approaches that “could be scaled up to remove very large amounts of carbon.” Again, this strongly counsels in favor of concentrating more investment in this sector, as well as others that have far higher scaling potential than biomass burial the in the long-term. 

The International Energy Agency, for example, recently projected that if all direct air capture facilities now in various stages of development, ranging from planning through construction, were to advance to deployment, “DAC deployment would nearly reach the level required in 2030 under the Net Zero Emissions by 2050 (NZE) Scenario, or around 65 MtCO2/year.” Indeed, a single planned facility, Carbon Capture’s Project Bison in Wyoming, could be capturing 5 million tons of carbon dioxide annually in 2030. Moreover, 1PointFive’s Stratus facility in Texas could be capturing 500,000 tons of carbon dioxide annually as soon as next year.

So, while Graphyte has emphasized that its approach could sequester far more carbon dioxide than the direct air capture company Climeworks’ Orca facility in Iceland, this seems like a bit of a straw man, as Orca was always contemplated to be an early-stage prototype. Moreover, it strikes me as unfair for Graphyte to invoke the ongoing failure of nuclear fusion to become a viable source of energy production as a reason to cast doubt upon large investments in direct capture, given the fact that direct air capture has already been proven fit for purpose as a carbon removal option on a commercial scale. By contrast, nuclear fusion has not yet reached that point and may never.

Ultimately, the potential of direct air capture facilities dwarfs the potential of the Graphyte approach by 2030 and beyond. However, as the IEA has emphasized, effectuating direct air capture’s potential in 2050 and beyond will require an immediate and robust focus on market and policy mechanisms to bring this potential to fruition. This is because investment in novel carbon dioxide removal approaches, such as direct air capture, in their “formative phase” can drive “a positive feedback cycle of growth and investment [providing] a platform for rapid scaleup.”

By contrast, if Graphyte’s figures are correct, and its levelized cost of production is already below $100, then its approach is already very economically viable in both voluntary and, potentially, compliance markets. Thus, it presumably does not require massive infusions of capital to effectuate economies of scale for this approach. As a consequence, it strikes me as far more sensible to focus our investment in approaches such as direct air capture, where economies of scale and learning-by-doing can help move us toward the “sweet spot” for prices that can help to scale the technology up substantially over the course of the next few decades.

Moreover, while direct air capture has the potential to reach the gigaton stage of sequestration by 2050 and perhaps as much as 15 gigatons annually by 2100, biomass burial approaches may have far more limited potential. While Graphyte contends that its approach could “permanently remove billions of tons of carbon dioxide,” a number of recent analyses indicated that burying biomass may ultimately not prove to be the optimal use of biomass, which could ultimately severely curtail the potential of this approach. 

Notably, recent studies cite potentially superior alternative uses for this resource from a climate policy perspective, such as the use of biomass to produce sustainable aviation fuels, hydrogen production, or biochar. Moreover, some commentators have suggested that it might be injudicious to bury substantial amounts of one major source of biomass, crop residues, given the fact that such residues provide a critical source of nutrients for crop production. 

Of course, this analysis does not militate against encouraging the scale-up of biomass burial approaches. The reality is that we’re likely going to need a robust portfolio of CDR approaches to achieve massive carbon removal by the end of this century. However, from a policy perspective, focusing on short- and medium-term investments in an approach that is likely to find ready markets without said support and may ultimately be limited in terms of long-term sequestration potential does not sound like the optimal approach to drive carbon removal.