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To capture carbon from the environment, we need to first decarbonize the grid

Daniel Morton — Thu, 14 May 2026 16:50:20 +0000

To capture carbon from the environment, we need to first decarbonize the grid Daniel Morton Thu, 05/14/2026 - 10:50

Daniel Morton

Most carbon capture research focuses on the chemistry. A new study from CU 91��Ҹ� takes a big-picture look and asks hard questions about the whole system: what does it cost, at scale, and under real-world conditions?

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In 2024, global average temperatures exceeded 1.5 ^oC above pre-industrial levels for the first time. This threshold was set as an aspirational limit by the 2015 Paris Agreement and was considered a line beyond which the impacts of climate change on ecosystem and human vulnerability become stark. Crossing this threshold is a signal that reducing emissions alone will not be enough. Increasingly, scientists, engineers, and policymakers around the globe agree that we will need to actively pull carbon dioxide (CO₂) out of the atmosphere to help reduce the impacts of this pollutant. The scale of this task is vast. The International Energy Agency projections suggest that reaching net-zero emissions by 2050 will require removing around one billion tonnes of CO₂ from the atmosphere every year. A billion tonnes of CO₂ is roughly equivalent to the annual CO₂ output of the entire global aviation industry. This vast amount needs to not only be offset from the system but fully removed from it.

This is the problem that has inspired a collaborative team of researchers at RASEI, including RASEI Fellows Prof. Wilson Smith and Prof. Bri-Mathias Hodge, and is the subject of a recent collaborative report published in Joule.

Two ways to catch carbon

91��Ҹ�ers are exploring a number of ways to pull CO₂ directly from the environment, and this comparative study looks at two of them side-by-side. The first, direct air capture (DAC), draws air from the atmosphere through a liquid solution that absorbs CO₂, analogous to a large-scale filter. It is the more established of the two approaches, with the world’s largest DAC facility currently under construction, a plant in Texas designed to remove 500,000 tonnes of CO₂ per year. The second approach examined in this study, direct ocean capture (DOC), is less developed but works with a natural advantage: it is estimated that the oceans absorb around 30% of the CO₂ that human activity produces each year, meaning seawater is already rich in dissolved carbon that originated in the atmosphere. By extracting that carbon directly from seawater, DOC bypasses the need to process enormous volumes of air. In fact, this advantage is one of the main reasons why many researchers are evaluating the feasibility of DOC as a CO₂ removal solution.

Both approaches share a common challenge: once you have captured the CO₂ from air, you need to do something with it. The regeneration process releases concentrated CO₂ in a usable form, while also recovering the capture solvent. In most current DAC systems, this process requires heating the captured material up to around 900 ^oC, typically by burning natural gas. This process is energy-intensive and creates its own greenhouse gas emissions, somewhat undermining the overall carbon capture process.

To try and understand the impacts of this overall process, the RASEI team modeled what happens when you substitute the heat-based regeneration setup with an electricity-driven alternative called bipolar membrane electrodialysis, or BPMED. Instead of using heat to release the CO₂, BPMED uses electricity to shift the chemistry of the captured solution, enabling the release of CO₂ at ambient temperatures. The key question the team sought to answer was whether this substitution makes economic sense when integrated with DAC and DOC, and under what kinds of conditions.

Building the model

To assess the DAC and DOC pathways, the team built a portfolio of connected 91��Ҹ�, starting from the physics of how CO₂ is captured and released, moving through the energy demands of each step, all the way up to a full cost analysis. This kind of approach, known as a techno-economic analysis (TEA for short), links the technical performance of a process directly to its economics. A TEA allows you to not just explore whether something works but also gain insight into whether it is viable at scale and under real-world conditions.

A particular strength of this study is the level at which the 91��Ҹ� connect these dots. As lead author Dr. Hussain Almajed (who started an ORISE Postdoctoral fellowship at the National Energy Technology Laboratory in July of 2025 shortly after graduating with his PhD from CU 91��Ҹ�) puts it, the goal was to compare the two approaches “not to say which one is the winner, which one is the loser, but to highlight the trade-offs.” The team pulled data from the California electricity grid, modeled different power supply scenarios, and ran both the DAC-BPMED and DOC-BPMED systems through the same framework. This provided a side-by-side comparison, one that had not previously been explored, that produced some unanticipated observations.

Two technologies, two cost profiles

The comparative study revealed a foundational trade-off rooted in a fundamental difference between DAC and DOC: Concentration. Air contains about 120 times less carbon than seawater, requiring large volumes of air to be processed at every iteration. However, once the CO₂ is captured via a liquid solvent, typically a hydroxide, the comparison reverses. A typical liter of DAC solution contains 0.5 to 1.0 moles of dissolved carbon, which is roughly 160 to 320 times higher than the dissolved carbon in a liter of seawater. That means a DAC plant needs to process far less liquid to recover a given amount of CO₂ compared to DOC, but extracting carbon from such a concentrated solution requires running the BPMED part of the system at high intensity, at high electrical current, which consumes significant energy. The equipment footprint is relatively small, but the electricity bill is high.

DOC works the other way around. Because seawater holds less dissolved carbon compared to a DAC solution, a DOC plant must process vast amounts of seawater to recover the same amount of CO₂. The 91��Ҹ� estimate that DOC-BPMED would need roughly 20 times more membrane area than the equivalent DAC-BPMED system, representing a significant upfront investment. On the other hand, the electrically driven process can run at a much lower current when handling dilute seawater, using considerably less energy per tonne of CO₂ captured.

These differences are obvious in the cost estimates. For a plant capturing 100,000 tonnes of CO₂ per year, and connected to the current California electricity grid, the modeled cost of capture via DAC-BPMED came in at around $470 per tonne of CO₂ in the baseline case. For DOC-BPMED, the equivalent figure was around $1,500 per tonne, roughly three times higher. This is driven largely by the upfront cost of all the additional equipment, and not the energy use.

The authors are careful to state that these modeled estimates have a meaningful level of uncertainty built in, and they will shift as the underlying technologies mature. But the overall trends are clear. At present, and with the current equipment costs, DAC-BPMED has a significant cost advantage over DOC-BPMED under this electrically driven regeneration approach.

Unexpected potential routes to profitability

A finding that stood out from these 91��Ҹ� was an often overlooked commodity side product. The BPMED process works by using electricity to split a salt solution into an acidic stream, which is used to release CO₂, and a basic stream which produces sodium hydroxide (NaOH). Sodium hydroxide is a widely used industrial chemical, a commodity found in a range of industries such as paper manufacturing, water treatment, and chemical synthesis, with an established market value, averaged at around $450 per tonne.

In the DOC model, because the plant is processing such large volumes of seawater, it produces considerably more sodium hydroxide than it needs for its operation. The 91��Ҹ� show that selling that surplus could reduce the cost of the overall CO₂ capture process substantially. In a scenario projecting a largely decarbonized electricity grid by 2050, the revenue generated from sodium hydroxide sales was enough to fully offset the costs of the CO₂ capture process, and in the most optimistic scenario, the process showed a net profit.

The authors were candid about the limits of this finding. The global sodium hydroxide market, even accounting for projected growth, is not large enough to absorb the products from carbon capture at the scale required to make a meaningful dent in atmospheric CO₂ “Our brief market analysis showed that even if DOC-BPMED supplied 20% of the projected 2050 sodium hydroxide demand, it would still offset less than 0.1% of today’s global energy emissions.” Dr. Almajed said. But the principle illustrated by this finding has broader implications. Coupling carbon capture with the production of a valuable commodity, either carbon-based, or as a side-product, could be a viable route to improving the economics of the whole process. It is an approach that is already being pursued commercially, including by Travertine Tech, a company based in 91��Ҹ�, Colorado, which captures CO₂ while producing and selling phosphoric acid, gypsum, and cementitious materials.

The electricity issue

Because the BPMED regeneration process is driven entirely by electricity, the source of that electricity matters enormously. This impacts both the cost of the process, and whether it actually delivers a net reduction in atmospheric CO₂. A carbon capture plant powered by fossil-fuel generated electricity that itself emits CO₂ is self-defeating.

To explore how different electricity generation modes impact the overall process, the team modeled four power supply scenarios. The current California grid, a projected 2050 California grid operating at 95% decarbonization, and two off-grid options: dedicated wind and dedicated solar. Interestingly, the team found that connecting to the grid outperformed both off-grid renewable options on cost, in both the current and the projected scenarios. The authors suggest that in the model this is down to a matter of reliability, a grid-connected plant can essentially run continuously, spreading its capital costs across more operating hours. A plant running on dedicated solar or wind is constrained by intermittency, which can drive up the cost per tonne of CO₂ captured. Dr. Almajed highlights that this is an area of the model that could be expanded, “We just looked at solar or wind each by itself, we didn’t optimize the off-grid scenarios to include energy storage and batteries.”

The policy implication built from the observations across the model is clear, explains Dr. Almajed, “We need to really pursue grid decarbonization. We need cleaner energy to power technologies that are going to help address climate change.” Technologies, such as DAC- and DOC-BPMED do not operate in isolation from the broader energy system. The effectiveness of these technologies to help combat atmospheric pollution, both economically and technically, is critically dependent on the grid they are plugged into. Decarbonizing that grid is not a separate problem, it is a prerequisite.

The future of carbon capture

While there are a lot of valuable observations and ideas that have come out of this TEA, no model is perfect. The team was quick to clarify areas where their model could be refined as technologies and ideas evolve. “When technologies are in such a nascent stage, the analysis of these 91��Ҹ� should focus on qualitative, rather than quantitative, insights” explains Prof. Bri-Mathias Hodge. “While there are a number of areas where the model can be improved, it also suggests where efforts for improvements are best focused, particularly the aspect that have the largest impact on results.” This includes more detailed modeling of the membranes, better data on equipment costs as the technology matures and is more widely deployed, and a more complete optimization of how these carbon capture plants might interact with energy storage or hybrid power systems. Many of these are manageable problems, and work is already underway at RASEI to address some of these areas.

Sometimes, the real value in this kind of analysis is in what it reveals before such refinements are made. By mapping the full system, from the technical fundamentals through the macroscale economics, this study helps to identify where research effort is best directed. Enhancing the concentration of the dissolved carbon in the seawater fed into a DOC plant, for example, could reduce costs by 40-50% according to the study’s sensitivity analysis. As a technology that is beginning to be deployed and scaled, identifying areas where large improvements in process efficiency can be made could have significant energy, and cost savings. As Dr. Almajed notes, “The study generated a lot of insights that we didn’t even consider at the start of the project.”

Removing carbon from the atmosphere at the scale required to significantly impact global emissions is an interdisciplinary problem that spans chemistry, engineering, economics, and energy policy. Analyses such as this don’t necessarily resolve that complexity, but they do help to make it understandable, and act as a roadmap to focus efforts. Knowing where the bottlenecks are, and insights into what it would take to impact them, is a great way to start solving the problem.

May 2026

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Watching Carbon Capture in Action

Daniel Morton — Wed, 13 May 2026 21:00:48 +0000

Watching Carbon Capture in Action Daniel Morton Wed, 05/13/2026 - 15:00

Daniel Morton

Removing carbon dioxide (CO₂) directly from the air, a process called direct air capture (or DAC), is one of several approaches being developed to help reduce the concentration of this greenhouse gas in the atmosphere.

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Among the methods being scaled up, one of the more established involves exposing air to a strongly alkaline liquid, typically a solution of potassium hydroxide (KOH), commonly known as lye. The liquid chemically binds the CO₂, converting it into dissolved salts called carbonates and bicarbonates. Large facilities using this principle are already operating or under construction, with one plant in Texas that is currently under construction, designed to remove 500,000 tons of CO₂ per year.

Despite the maturity of the underlying chemistry, there has been a fundamental limitation in how well researchers can study it. Until now, the process has been something of a black box. Scientists could measure what went into a capture system and what came out, but the detailed chemistry happening inside, specifically in the thin zone where the air and liquid meet, was very difficult to observe directly. This is a meaningful gap, because what happens in that zone determines how efficiently the system works, and how it should be designed, especially for novel DAC liquids. As Jason Pfeilsticker (a Graduate Student in the group of RASEI Fellow Wilson Smith, and lead researcher on this project), explains, “This really is a case of if you want to know about something, just look at, really carefully, and in this case there was some work to do before we could take a detailed look”.

Think of it like medicine before medical imaging. For centuries, doctors understood that the body had internal structures and processes, but could only examine them indirectly, through symptoms, pulses, and what came out of the body. The development of X-rays and later MRI scanning did not change human biology, but it transformed what could be understood and acted upon. A diagnosis that once required guesswork could suddenly be made based on the information gained from mapping out the internal structures of the body. This study, just published in ACS Energy Letters, represents a similar shift for CO₂ capture: rather than inferring what is happening at the gas-liquid interface from indirect measurements, researchers in the group led by Wilson Smith at the 91��Ҹ� 91��Ҹ� have built an instrument that lets them watch it directly.

The instrument at the center of this work is a custom-designed laboratory flow cell. This device was designed and built specifically for this purpose and, to the teams’ knowledge, is the only one of its kind. “There were so many different variables that we wanted to explore, but in order to design a better process and or screen novel DAC solvents, we needed to have a better picture of what was going on” explains Pfeilsticker, “You can change the solvent, the pressures, the flow, the reactor design, all of which affect the microenvironment and thus the DAC performance ”. To get a clearer picture they set out to build a flow cell with built in features that enabled accurate spatial mapping of the kinetics of the reaction, in real time. Designing and building it required solving a series of practical problems. The cell needed to bring CO₂ gas into contact with flowing KOH liquid through a porous membrane, closely mimicking the interface in a real capture system. It needed to be optically clear and stable enough to allow laser-based measurements without bubbles, vibrations, or chemical interference disrupting the readings. The flow inside needed to be smooth and predictable, what scientists call laminar flow, so that the measurements could be interpreted meaningfully. Each of these requirements shaped the final design, from the choice of materials to the geometry of the flow channels. However, this oversimplifies the actual process, these lessons were learned as part of an extensive prototyping process.

“We made at least 60 or 70 iterations of this cell during the project” explains Jason. “I was drawn to this project because I really like to make things, and this looked like a challenge that would use a great combination of scientific investigation, detailed design and hands-on building”. Jason, who spends much of his free time working on motorcycles, or building electronics and musical instruments, knew he was going to need to iterate on the cell design. Early on the team considered getting design iterations professionally machined. But each of these would cost thousands of dollars to produce, and when you are learning what is important as you are designing, a small tweak here and there can become very expensive. A typical filament-based 3D printer would not be suitable for working with the chemicals involved in DAC. “We identified a resin that was chemically compatible with the base reagents we were using, and we found a cheap resin 3D printer online, that let us do some initial proof-of-principle work, then we upgraded to a better 3D printer for the project, and now we could print iterations for less than a dollar,” said Jason. This not only made the process cheaper but sped-up design development as well. The team identified three big challenges as they worked through the designs: good seals, bubbles, and smooth flow of the liquid. The solutions for these came from a number of inspirations, including sealing mechanisms borrowed from drumheads, reactor geometry angles to reduce bubble formation to enable effective laser probing, shaping of the flow inlets and outlets to ensure laminar flow, and flow dampener design.

To explore the reaction and map out the kinetics of the process the team used a technique called confocal Raman spectroscopy to make their measurements. This works by shining a laser at a point in the liquid and reading the light that scatters back; different chemical species produce distinct signatures, making it possible to identify and quantify them. By scanning the laser across the cell in a grid pattern while the process was running, the team built up two-dimensional chemical maps, essentially pictures showing where carbonates and bicarbonates were forming and accumulating across the contact zone, at the scale of fractions of a millimeter, in real time.

What those maps revealed was not what simple intuition would predict. “We saw that the equilibrium reaction is in effect going backwards near the surface” explained Pfeilsticker. When fresh KOH first contacts CO₂, the highly reactive hydroxide ions in the liquid rapidly consume the incoming CO₂, converting it to carbonate near the membrane. But this rapid reaction locally depletes the hydroxide supply right at the interface. As the liquid flows further through the channel and more CO₂ is absorbed, there are fewer hydroxide ions available near the membrane to drive the reaction forward. “Because it is laminar flow, there is no turbulent mixing” said Jason. The result is that a thin layer of bicarbonate, an intermediate chemical species in the conversion process, forms immediately next to the membrane, nestled between the membrane surface and the main hydroxide and carbonate-rich zone further into the liquid. This pattern becomes more pronounced further along the flow channel and represents a direct, spatial record of the chemistry unfolding in real time.

The team also found that operating conditions matter. Higher flow rates altered the shape and extent of the reactive zone, and doubling the concentration of KOH shifted the balance of products and appeared to reduce the hydroxide depletion effect near the membrane, potentially useful information for future system designs.

A key part of this work was the development of a computational model mirroring, and interpreting, what is going on inside the cell. Using the experimental observations to provide a framework to build the theoretical model allowed the team to effectively bound the scope and validate the model, in ways that would have been essentially impossible without the experimental data. The hope is that this model, which has now been validated with experimental data, in conjunction with flow cell maps can be used by future researchers as an initial screening tool in designing new DAC systems.

This work has the potential for significant impact. DAC Facilities using alkaline liquids are being built at the industrial scale. 91��Ҹ�ers are actively developing new and improved capture liquids to make the process more efficient, cheaper, and use less energy. With a cell design that enables accurate mapping, and a computational model that enables faster screening, the process of optimizing the carbon capture reactions can be accelerated. On an industrial scale even small improvements in reaction efficiency and cost can have huge savings on the system scale. Current approaches just look at the input and corresponding output of the cell, like judging a medical treatment by whether the patient recovered, without being able to examine what really happened inside the body.

This research describes a detailed, data-driven approach to answering the questions about what is really happening at the reactive center of DAC: how does a given liquid behave, what is happening at the interface where the chemistry is happening, how does varying the conditions impact the reaction? The combination of the experimental and theoretical tools disclosed by this work provides insight into how these processes work, and the key variables that can be used to optimize it.

The application of these tools can potentially extend beyond DAC. Wherever chemistry and transport interact at an interface, such as electrochemical systems that convert CO₂ into fuels or commodity chemicals, or in the separation of critical minerals. The design of this device was around one specific challenge, but has the potential for broad utility.

The transition from black box to observable system does not, by itself, solve the engineering challenges ahead. Models still need refinement, and scaling to industrial practice requires substantial research. But the ability to directly observe what is happening is a critical step in that process. What was previously assumed can now be tested. The reaction black box now has a window, that enables researchers to gain valuable insights into the inner workings of this critical process.

May 2026

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Assessing the Long-Term Stability of Anion Exchange Membranes for Electrochemical CO2 Reduction

Daniel Morton — Wed, 24 Dec 2025 00:06:34 +0000

Assessing the Long-Term Stability of Anion Exchange Membranes for Electrochemical CO2 Reduction Daniel Morton Tue, 12/23/2025 - 17:06

ACS APPLIED ENERGY MATERIALS, 2025, 9, 1, 359-371

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Cooperative effects associated with high electrolyte concentrations in driving the conversion of CO2 to C2H4 on copper

Daniel Morton — Thu, 19 Jun 2025 19:22:57 +0000

Cooperative effects associated with high electrolyte concentrations in driving the conversion of CO2 to C2H4 on copper Daniel Morton Thu, 06/19/2025 - 13:22

CHEM CATALYSIS, 2025, 5, 6, 101338

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Rapid Deactivation Convolutes Electrochemical CO2 Reduction Selectivity Measurements on Gold Rotating Ring Disk Electrodes

Daniel Morton — Wed, 09 Apr 2025 18:26:59 +0000

Rapid Deactivation Convolutes Electrochemical CO2 Reduction Selectivity Measurements on Gold Rotating Ring Disk Electrodes Daniel Morton Wed, 04/09/2025 - 12:26

JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 2025, 172, 046503

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Cation Crossover Limits Accessible Current Densities for Zero-Gap Alkaline CO2 Reduction to Ethylene

Daniel Morton — Wed, 08 Jan 2025 17:13:53 +0000

Cation Crossover Limits Accessible Current Densities for Zero-Gap Alkaline CO2 Reduction to Ethylene Daniel Morton Wed, 01/08/2025 - 10:13

ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 2025, 13, 2, 823-833

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Bulk Layering Effects of Ag and Cu for Tandem CO2 Electrolysis

Daniel Morton — Tue, 26 Nov 2024 03:31:02 +0000

Bulk Layering Effects of Ag and Cu for Tandem CO2 Electrolysis Daniel Morton Mon, 11/25/2024 - 20:31

CHEMSUSCHEM, 2024, e202401769

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Electrolyte–Electrocatalyst Interfacial Effects of Polymeric Materials for Tandem CO2 Capture and Conversion Elucidated Using In Situ Electrochemical AFM

Anonymous — Thu, 01 Aug 2024 06:00:00 +0000

Electrolyte–Electrocatalyst Interfacial Effects of Polymeric Materials for Tandem CO2 Capture and Conversion Elucidated Using In Situ Electrochemical AFM Anonymous (not verified) Thu, 08/01/2024 - 00:00

ACS APPLIED MATERIALS & INTERFACES, 2024, 16, 32, 42021-42033

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Converting captured carbon to fuel: Study assesses what’s practical and what’s not

Anonymous — Mon, 22 Jul 2024 06:00:00 +0000

Converting captured carbon to fuel: Study assesses what’s practical and what’s not Anonymous (not verified) Mon, 07/22/2024 - 00:00

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Insights into Electrochemical CO2 Reduction on Metallic and Oxidized Tin Using Grand-Canonical DFT and In Situ ATR-SEIRA Spectroscopy

Anonymous — Tue, 14 May 2024 06:00:00 +0000

Insights into Electrochemical CO2 Reduction on Metallic and Oxidized Tin Using Grand-Canonical DFT and In Situ ATR-SEIRA Spectroscopy Anonymous (not verified) Tue, 05/14/2024 - 00:00

ACS CATALYSIS, 2024, 14, 8353-8365

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