In the fight against climate change, CO2 removal (CDR) has been heralded by some as a technological panacea—a way to erase the damage wrought by fossil fuel emissions and stabilize the climate without fundamentally altering our dependence on carbon-intensive industries. If we can capture and store CO₂ at its source, why not simply extend that logic to remove carbon already lingering in the atmosphere? A new report by the American Physical Society (APS), led by an MIT physicist, delivers a sobering reality check: the physical constraints of large-scale CO₂ removal make it neither a viable nor scalable solution to global warming.
Unlike carbon capture at industrial sites, CDR focuses on extracting CO₂ that has already dispersed into the atmosphere—a vastly more difficult task. The APS report examines various CDR strategies, all of which are bound by immutable physical laws. One such method, direct air capture (DAC), operates like a giant sponge, pulling CO₂ from the air and then releasing it for permanent storage. But the second law of thermodynamics imposes an unavoidable cost: the lower the concentration of CO₂ in the air, the more energy is required to extract it. At the scale necessary to make a meaningful impact—removing billions of tons of CO₂ each year—a single DAC system would demand as much energy as an entire mid-sized U.S. state consumes annually. The few existing DAC prototypes already require three to ten times that amount of energy per ton of CO₂ removed, and they capture only minuscule quantities compared to what is needed.
Other proposed solutions, such as enhanced rock weathering, attempt to accelerate natural carbon-absorbing processes by grinding up enormous quantities of rock and spreading it across landscapes. While this method avoids some of the energy pitfalls of DAC, it runs into another unavoidable obstacle: mass. To remove one gigaton of CO₂, the process would require roughly an equivalent mass of finely crushed rock—demanding mining and material handling operations on a scale comparable to today's global fossil fuel infrastructure. This is not a realistic or sustainable approach.
For those who champion reforestation as a natural and scalable solution, the numbers paint a similarly daunting picture. One proposal suggests that each American could offset their carbon footprint by planting a quarter-acre of trees per year. While this sounds reasonable at first, simple arithmetic exposes its flaws: with 345 million people in the U.S., that would require planting 86 million acres of forest every year. Even if every viable acre of land in the U.S. that isn’t a desert, city, or farm were dedicated to tree planting, the available space would be exhausted in just 16 years. The hard truth is that we do not have enough land to rely on trees alone for carbon removal at the scale required.
Point-source carbon capture at industrial facilities—which prevents CO₂ from entering the atmosphere in the first place—fares slightly better in terms of feasibility, but it, too, faces severe constraints. The process of filtering emissions from power plants and factories requires a significant proportion of the energy outputs which diminishes its overall effectiveness. Even in an ideal scenario, where fully developed capture and sequester systems become operational, they are projected to capture and sequester only about 25% of emissions —a fraction of what is needed to mitigate global warming.
These are not minor technical hurdles; they are fundamental physical and economic constraints that expose the limitations of CDR as a large-scale climate solution. And yet, billions of dollars continue to be funneled into these technologies under the assumption that we can engineer our way out of the crisis we have created. This is magical thinking—the comforting but false belief that we can continue burning fossil fuels indefinitely because we will eventually invent a way to undo the damage.
Even the most optimistic projections for carbon removal acknowledge that these methods will require extraordinary amounts of energy, raw materials, and financial resources. And even if such technologies were perfected, they would be viable only in wealthy, industrialized nations. Developing countries—many of which are striving for the energy-intensive lifestyles long enjoyed in the West—will not have the means, nor likely the political will, to invest in these prohibitively expensive efforts. Expecting them to do so is not only unrealistic but profoundly unjust.
The conclusion is inescapable: there is no shortcut to solving global warming. No technological fix will allow us to continue pumping greenhouse gases into the atmosphere without consequence. Carbon removal may play a small supporting role in climate mitigation, but it cannot replace the urgent need to reduce emissions at their source.
It is time to abandon the illusion that we can clean up the mess we have made without changing our behavior. The only viable path forward is the one we have resisted for too long: adoption of policies that prioritize long-term planetary stability over short-term economic gains. We must abandon magical thinking and face the reality of what it truly takes to combat climate change.
