As the urgency to curb climate change intensifies globally, scientists and policymakers are continually exploring effective pathways to achieve net-zero emissions by mid-century. A pioneering study led by researchers at the University of Wisconsin–Madison sheds new light on this quest, revealing that the choices made in carbon dioxide removal (CDR) strategies could have profound implications for public health and environmental equity in the United States.

The research, published recently in Nature Climate Change, meticulously compares two contrasting scenarios to meet the net-zero emissions target by 2050. One scenario relies heavily on carbon dioxide removal technologies, while the other prioritizes direct reductions in fossil fuel emissions supplemented by lower CDR deployment. Intriguingly, the findings suggest that leaning too heavily on CDR may counterintuitively worsen air pollution-related health outcomes, particularly in vulnerable communities.

Carbon dioxide removal encompasses a suite of techniques aimed at extracting CO2 directly from the atmosphere and securely storing it for extended periods. Conventional methods include afforestation and enhanced soil carbon sequestration, which naturally lock carbon away. However, newer technological developments like direct air carbon capture and storage (DACCS) and bioenergy with carbon capture and storage (BECCS) offer engineered solutions by chemically or biologically capturing emissions from air or biomass energy processes. These technologies have gained traction as policymakers grapple with the ambitious goals mandated by the 2015 Paris Agreement to limit global warming to 1.5 degrees Celsius above pre-industrial levels.

Yet this promising approach is not without complications. By leveraging sophisticated integrated assessment models that simulate energy systems and atmospheric conditions, the research team carefully mapped out the consequences of each pathway. Their computational simulations incorporated air quality models alongside epidemiological data to estimate how changes in pollutant emissions would impact premature mortality rates across diverse U.S. communities.

Both scenarios, compared against a business-as-usual baseline, demonstrated substantial reductions in particulate matter pollution and associated premature deaths by 2050. However, the pathway with lower reliance on CDR outperformed the high-CDR scenario by preventing roughly 33,000 additional premature deaths annually. This difference stems primarily from the fact that certain CDR methods themselves entail residual emissions, as well as the continued use of fossil fuels that are harder to eliminate when depending heavily on removal strategies.

Significantly, the study also highlights the uneven distribution of pollution exposure and health benefits across socioeconomic and racial lines. The United States continues to grapple with entrenched environmental injustices: historically marginalized non-white and low-income communities disproportionately bear the brunt of air pollution’s harms. Encouragingly, the low-CDR pathway was found to reduce these disparities to a greater extent, achieving steeper reductions in pollution burdens for disadvantaged urban populations. In contrast, reliance on carbon removal technologies without comprehensive emissions cuts risks perpetuating or even exacerbating these inequalities.

Dr. Candelaria Bergero, the study’s lead author, emphasizes the multifaceted nature of the transition to net zero. “Our findings underscore that achieving climate mitigation goals is not a monolithic process. Each strategy carries distinct implications for public health and environmental equity,” she said. “Air pollution is an often overlooked but crucial dimension that must be accounted for in policy design.”

The study’s senior author, Assistant Professor Morgan Edwards of the La Follette School of Public Affairs, notes that while carbon removal technologies are indispensable tools in the climate mitigation arsenal, an overreliance may engender unintended consequences. Previous work by Edwards cautioned against inflated expectations surrounding CDR, advocating for a balanced policy portfolio that foregrounds direct emission reductions.

Environmental justice scholar and Stanford professor Steven J. Davis echoes this sentiment: “Addressing climate change will not automatically resolve air pollution challenges or their deep-rooted inequities. These require deliberate planning and targeted policy interventions.”

This research results from a growing body of work emerging from the Climate Action Lab at UW–Madison, where Dr. Edwards and colleagues harness data-driven modeling and policy analysis to craft solutions that prioritize fairness alongside climate goals. Their efforts extend to global assessments, exemplified by Edwards’ role as lead author of the authoritative third edition of The State of Carbon Dioxide Removal report, which systematically tracks CDR technologies’ progress worldwide.

By integrating sophisticated computational assessments with equity-focused evaluations, this study provides a critical lens through which national and international climate strategies can be scrutinized and refined. Its clear message: to optimize public health benefits and advance environmental justice, decarbonization pathways must carefully balance emissions reductions with judicious deployment of carbon removal technologies.

As the world races toward the halfway mark to 2050, these insights will prove invaluable for guiding sustainable, equitable climate policies. The path to net zero is complex, yet deliberate choices today can lay the foundation for cleaner air, longer lives, and a healthier planet for tomorrow.

Subject of Research: Not applicable

Article Title: Residual emissions may perpetuate community-scale inequalities in US air pollution

News Publication Date: 30-Jun-2026

Web References:

• Nature Climate Change DOI: 10.1038/s41558-026-02675-0
• University of Wisconsin–Madison – Climate Action Lab: https://www.climateactionlab.com/
• The State of Carbon Dioxide Removal Report: https://www.stateofcdr.org/

References:
Bergero, Candelaria et al. “Residual emissions may perpetuate community-scale inequalities in US air pollution.” Nature Climate Change, 2026.

Keywords: Carbon dioxide removal, CDR, net-zero emissions, air pollution, environmental justice, climate mitigation, particulate matter, premature death, direct air carbon capture and storage (DACCS), bioenergy with carbon capture and storage (BECCS), environmental equity, climate policy

A recent collaborative study led by researchers at the Renewable and Sustainable Energy Institute (RASEI), including Professors Wilson Smith and Bri-Mathias Hodge, presents an incisive techno-economic comparison of two frontier methods for atmospheric carbon removal: direct air capture (DAC) and direct ocean capture (DOC). This work, published in the journal Joule, leverages integrated modeling frameworks to assess both technologies under an innovative regeneration strategy powered by bipolar membrane electrodialysis (BPMED), a promising electricity-driven process.

Direct air capture, the more mature of the two approaches, employs liquid solvents to scrub CO₂ directly from ambient air. Facilities like the under-construction plant in Texas, capable of capturing half a million tonnes of CO₂ annually, showcase the scalability potentials of DAC technology. In contrast, direct ocean capture capitalizes on the ocean’s natural propensity to absorb a substantial fraction of anthropogenic CO₂ emissions—roughly 30% per year. By extracting dissolved inorganic carbon from seawater, DOC circumvents the energy-intensive need to process vast quantities of dilute atmospheric air, leveraging the ocean’s carbon reservoir as a more concentrated carbon source.

A critical obstacle shared by both techniques is the regeneration of the sorbent medium, which conventionally requires thermal input near 900°C to release concentrated CO₂. This step not only demands significant energy, often sourced from fossil fuels, but also emits greenhouse gases that compromise the net efficacy of CO₂ removal. Recognizing this challenge, the RASEI team simulated replacing thermal regeneration with BPMED, wherein electrical currents drive chemical shifts to release CO₂ under ambient temperature conditions, potentially reducing energy consumption and emissions.

The study’s integrated techno-economic analysis (TEA) bridges physical capture mechanisms, energy expenses, and full cost implications, enabling a holistic understanding of scale-up feasibility. Lead author Dr. Hussain Almajed emphasizes the study’s goal to elucidate trade-offs rather than declare a definitive winner, contextualizing the comparison within varying energy grid scenarios, including current and projected decarbonized states of the California electricity grid as well as off-grid renewable power supplies.

Fundamental disparities in carbon concentration between air and seawater define the operational and economic characteristics of DAC versus DOC. While atmospheric CO₂ is exceedingly dilute—approximately 120 times less concentrated than dissolved carbon in seawater—once captured, the typical DAC solvent solution exhibits carbon concentrations 160 to 320 times higher than that of seawater. This means DAC systems process smaller liquid volumes but operate BPMED under high electrical currents, resulting in high energy consumption despite a more compact equipment footprint.

Conversely, DOC systems must handle vast volumes of seawater with low carbon content, necessitating membrane areas roughly 20 times larger than DAC facilities. Although this significantly elevates capital costs, the BPMED process for DOC runs at lower current densities, translating to decreased energy per tonne of CO₂ captured. In modeled scenarios for a plant capturing 100,000 tonnes of CO₂ annually, DAC-BPMED’s cost approximated $470 per tonne under California’s existing grid, while DOC-BPMED was near $1,500 per tonne, predominantly due to capital expenditure rather than operational energy use.

An unexpected insight emerged regarding the economic role of sodium hydroxide (NaOH), a co-product generated during BPMED regeneration. NaOH is a globally traded industrial chemical, valued at around $450 per tonne, serving industries from paper manufacturing to water treatment. The DOC process, by processing expansive seawater volumes, produces surplus NaOH beyond its operational needs. Modeling suggests that in a decarbonized energy future circa 2050, revenue from NaOH sales could wholly offset the CO₂ capture costs, potentially resulting in net profitability for DOC-BPMED.

Despite these promising indications, the researchers caution about market scale limitations. The global NaOH market’s size constrains how much of the carbon capture industry’s output it can absorb without saturation effects. Even if DOC-BPMED supplied 20% of 2050 NaOH demand, it would offset less than 0.1% of today’s global energy emissions. Nonetheless, this finding highlights the broader strategic potential of integrating carbon capture with valuable commodity production, a synergy already pursued by companies like Travertine Tech, which simultaneously captures CO₂ and manufactures commercially valuable phosphoric acid and cementitious materials.

The source and nature of electricity powering BPMED regeneration is a paramount factor influencing the sustainability and cost profile of these capture systems. Through four electricity scenarios—California’s current grid, a highly decarbonized 2050 projection, and dedicated off-grid wind and solar installations—the study elucidates that grid-connected systems currently outperform standalone renewables on cost efficiency. The continuous operation enabled by grid reliability dilutes capital costs compared to intermittent renewables, which lack integrated energy storage optimizations in the model, elevating capture costs per tonne.

These findings underscore a vital policy message: achieving effective carbon removal at scale is intricately linked to grid decarbonization. Clean, reliable electricity supply is not ancillary but foundational to deploying next-generation carbon capture technologies sustainably and economically.

While the study offers rich insights, the authors acknowledge areas for refinement. Advanced membrane material characterization, updated equipment cost data, and integration of hybrid energy systems with storage promise to sharpen future model fidelity. These enhancements yield not only more precise cost predictions but also strategic direction on research investments—such as efforts to increase seawater carbon concentration for DOC, which the study’s sensitivity analysis indicates could slash capture costs by up to 50%.

Ultimately, removing atmospheric carbon on a scale commensurate with global emissions reduction targets demands interdisciplinary approaches spanning chemistry, engineering, economics, and policy. This study’s comprehensive techno-economic framework demystifies the complex trade-offs that define carbon removal technologies, presenting an informed roadmap for optimizing research and deployment strategies. Recognizing bottlenecks, evaluating synergies with commodity markets, and embedding the carbon capture systems in the context of a clean energy grid are pivotal steps en route to meaningful climate mitigation.

Subject of Research: Carbon dioxide removal technologies; direct air capture and direct ocean capture using bipolar membrane electrodialysis.

Article Title: Comparative Techno-Economic Analysis of Electrically Regenerated Direct Air and Ocean Carbon Capture Systems.

News Publication Date: 10-Apr-2026

Web References:

• https://climate.copernicus.eu/copernicus-2024-first-year-exceed-15degc-above-pre-industrial-level
• https://www.iea.org/reports/net-zero-by-2050
• https://www.colorado.edu/rasei/wilson-smith
• https://www.colorado.edu/rasei/bri-mathias-hodge
• https://doi.org/10.1016/j.joule.2026.102424
• https://doi.org/10.1038/s41467-020-18232-y
• https://travertinetech.com

References:
Almajed, H., Smith, W., Hodge, B.-M., et al. (2026). Comparative Techno-Economic Analysis of Electrically Regenerated Direct Air and Ocean Carbon Capture Systems. Joule. DOI: 10.1016/j.joule.2026.102424.

Keywords:
Carbon capture, Direct air capture, Direct ocean capture, Bipolar membrane electrodialysis, Carbon dioxide removal, Techno-economic analysis, Climate change mitigation, Renewable energy integration, Sodium hydroxide co-production, Grid decarbonization.