The Cost-Effectiveness of Carbon Dioxide Removal Methods

Peter Fiekowsky and Carole Douglis | October 12, 2023 | Leave a Comment Download as PDF

Costs determine scalability and vary by a factor of 30,000 


What is Carbon-Dioxide Removal For?

One purpose of carbon dioxide removal (CDR) is to provide “offsets” that legitimize continuing emissions. The other is to restore the pre-industrial climate by 2050 by removing legacy CO2

CDR tops the tech headlines with increasing frequency, leading to the impression that we are rapidly developing a multitude of mostly industrial options for creating a safe climate.  

What many miss is that the vast majority of “carbontech” CDR approaches are designed to develop the carbon offset market. By definition, offsets only compensate for continued emissions. They do not touch the 1,000 gigatons of legacy CO2 that is causing most of the climate havoc.

CDR today serves two distinct policy purposes. Each has merit, yet achieving the two goals requires quite different approaches and budgets and would create strikingly different results. 

The two goals of CDR are:

  1. Developing a CDR industry that underpins the carbon offset market—thus adhering literally to the 1992 United Nations goal to “stabilize” greenhouse gas (GHG) levels. Today, this means stabilizing at dangerous levels never before experienced by our species. This is of course now called “net zero emissions,” and
  2. Following what appears to be the original intent of the United Nations Framework Convention on Climate Change: to restore GHG levels proven safe for humanity and nature as we know it. Restoring historically safe GHG levels is commonly called “climate restoration.”

Toward Net Zero

The goal of stabilizing GHG levels was set in the early 1990s when the climate impacts of GHG were still imperceptible and global warming considered theoretical. If emissions had ceased at that time, the climate would still be safe.

Today, adhering only to the net zero goal is severely problematic. Reaching net zero by 2050 would push average atmospheric CO2 levels to around 460 parts per million (ppm)—more than 60 percent higher than the pre-industrial levels in which humanity thrived for thousands of years. CO2 at today’s 420 ppm level is already causing havoc. Nevertheless, net zero remains our official goal, and its pursuit has birthed a thriving carbon tech industry that offers “offsets” to corporations that continue to burn fossil fuels. 

While the offset market promises good business for emerging CDR tech and can counteract a small amount of continued emissions, it does nothing to reduce the concentrations of GHG in the atmosphere. By definition, each carbon offset only exists to negate a ton of CO2 emitted. Controlled emissions (mainly in the EU) will eventually stop. No emissions means no offsets, and the CDR business model collapses.

Toward Climate Restoration 

The second goal—restoring CO2 levels that have proven safe for humanity over thousands of years— requires more than stabilizing GHG levels. It requires reducing atmospheric CO2 by 40 percent— from today’s level to historically safe levels under 300 ppm. In practical terms, that means pulling a trillion tons of accumulated CO2 from the atmosphere in addition to negating future emissions.

Different goals, different costs and benefits. Each goal—stabilizing GHGs at today’s level, and restoring a pre-industrial climate—is justifiable and we can achieve both. However, it is important to remember that they are different and serve different needs. 

We have compared various CDR methods to cost and scalability. The results are striking: Direct-air-capture (DAC) and related carbontech methods cost $500 – $1000 per ton of CO2 captured.  

In contrast, climate restoration solutions, based on intentional biomimicry, cost only a few cents per ton of CO2 removed. DAC and iron fertilization of the ocean (OIF), for instance, differ by a factor of about 30,000. Even if DAC costs were to drop 90 percent overnight, industrial methods would still cost thousands of times more than CDR methods based on natural processes. 

Where Are We Now?

The more expensive, industrial CDR methods are well suited to the carbon offset market designed for net zero emissions. CDR approaches based on natural processes, on the other hand, have been demonstrated to be so inexpensive and effective that they could be deployed on a large enough scale to remove the legacy CO2 and restore a safe climate—with minimal investment.

At this point, funders favor paying for carbon offsets to meet net zero. Billions of public and private sector funds have poured into expensive carbon tech for this purpose. Meanwhile, large-scale climate-restoration solutions—while thousands of times more cost-effective and ready to go—remain less well-known and virtually unfunded. 

They will be implemented when the world returns to the original goal of giving future generations a livable planet by restoring and then stabilizing GHG levels.


To compare the methods by cost per ton of CO2 removed, we use data from the developers or implementers themselves when published, or projections from peer-reviewed studies or institutions such as the National Academies of Science, Engineering, and Medicine (NASEM).

We include current and expected future costs and separate capital and operational costs. This allows a comparison of methods that are self-financing (through sales of by-products such as seafood and building materials) with others that would require large sums of public financing to make a measurable impact. We provide the best estimates based on current data, neither optimistic nor conservative.


It turns out that the cost of CDR varies by a factor of 30,000—from a few cents to a thousand dollars to remove a ton of CO2 from the atmosphere. This enormous discrepancy makes sense when we consider that low-cost CDR, in particular OIF, duplicates and optimizes natural processes that have occurred for millions of years, and to which Earth systems are adapted.

At the other end of the expense spectrum, CDR methods, such as DAC, use industrial processes originally based on the technology of removing CO2 from submarines. These processes are designed to produce a pure CO2 product to sell for enhanced oil recovery and other commercial uses, or pumped and sequestered underground.

The startling variation — about 3 cents per ton vs $1,000 — also highlights very different reasons for pursuing CDR. Sequestering pure CO2 underground produces carbon offsets for businesses to purchase so they can “offset” their continued use of fossil fuel. While useful to help fossil fuels make a graceful exit from the economy, offsets do not reduce the level of CO2 in the atmosphere, as every ton removed is by definition counterbalanced by a new ton of emissions. This keeps them in conformance with the 1992 goal of stabilizing GHG levels.


The carbon market will participate in stabilizing GHG levels by 2050. Doing that will leave levels more than 50 percent higher than humans have ever seen long-term. The survival of human societies, and humanity itself, is frankly uncertain under the conditions of net zero without restoring pre-industrial levels of CO2, which requires CDR on a much grander scale.

Clearly, the 1992 UNFCCC climate goal to stabilize GHG levels is obsolete, with CO2 already 40 percent above historically safe levels and climate systems breaking down at alarming rates. A campaign to update the UN climate goal to “restore and stabilize GHG levels” has therefore begun. The premise that humanity has an obligation to future generations to intentionally restore a safe climate is attracting popular support. Climate restoration, defined as the goal and actions that restore historically safe CO2 levels below 300 ppm by 2050, appears to be achievable with already demonstrated CDR methods, for less than 1% of what we are (wisely) spending on the energy transition.

Intermediate solutions such as solar photovoltaics (PV) and synthetic limestone also have an important role in reducing future CO2 levels. Solar PV avoids emissions, while synthetic limestone sequesters CO2 in high-quality building materials. Each of these provides carbon-negating services as a side-benefit of what people pay for: energy and building materials.

Both solar photovoltaics and synthetic-limestone-based concrete can help achieve net zero emissions 100 times faster per dollar invested than new tech CDR.

In years past, climate restoration was often dismissed as “geoengineering” (intentionally interfering with the climate system) and research on it failed to secure government or academic funding. Thus, climate restoration approaches were advanced instead by independent scientists and entrepreneurs. Except for early work on OIF, these have rarely appeared in peer-reviewed literature. Yet, climate-restoration methods have indeed been tested and demonstrated, with safety and efficacy uppermost in mind. They are ready to deploy and to scale.

As more and more of the public clamors to restore a safe climate, the modest capital costs of climate-restoration solutions could be covered by public or philanthropic funds. Otherwise, they are likely to be funded by compassionate grandparents and future grandparents for whom a liveable planet for our children is paramount.

In the meantime, government, industry, and the carbon offset market can continue to fund expensive CDR projects that, while they have no hope of restoring the climate, are good for business and investors.

Download the working paper, including references, here or from the link above.

Peter Fiekowsky, author of Climate Restoration: The Only Future That Will Sustain the Human Race, is an MIT-educated physicist, philanthropist, and Silicon Valley entrepreneur with 27 patents. His interest in restoring a climate safe for humanity grew from 30 years of experience as a citizen lobbyist for poverty and climate issues. Fiekowsky’s mission is to leave a world we’re proud of to our children. To that end, he has founded a number of organizations including the Foundation for Climate Restoration, Methane Action, Stable Planet Alliance, which is working to restore a sustainable population, and the interim Climate Restoration Safety and Governance Board.

Carole Douglis, co-author of Climate Restoration: The Only Future That Will Sustain the Human Race, is an award-winning journalist specializing in environment, climate, and international development. Her work has been published by the Atlantic, Psychology Today, and National Geographic Books, as well as the United Nations Environment Programme (UNEP), UNICEF, USAID, NGOs, and numerous research institutes. Since 2019 she has focused on climate restoration as Peter Fiekowky’s writing partner and, more recently, as Director of Communications for the Foundation of Climate Restoration. Carole holds an A.B. from Harvard University and an M.A.L.D. from the Fletcher School of Law and Diplomacy.

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