Interview: the skeptic's view on Carbon capture materials (sorbents, membranes) — what would change their mind

At £600–1,200 per tonne of CO₂ captured, direct air capture (DAC) remains one of the most expensive climate interventions available. For skeptics in the carbon capture materials space, this figure encapsulates the fundamental tension between technological promise and economic reality. While the UK government has committed £20 billion to carbon capture and storage infrastructure through 2035, materials scientists and industrial engineers continue to debate whether current sorbent and membrane technologies can ever achieve the cost reductions necessary for meaningful climate impact. This synthesised perspective draws from conversations with practitioners who maintain healthy skepticism about the field's trajectory—not because they doubt the science, but because they understand the gap between laboratory performance and industrial-scale deployment.

Why It Matters

The UK's legally binding commitment to net zero by 2050 depends critically on carbon capture technologies removing 20–50 million tonnes of CO₂ annually by mid-century. Current operational capacity stands at approximately 1.5 million tonnes per year across all UK installations—a mere 3–7.5% of the target. The materials that enable this capture—amine-based sorbents, solid sorbents, metal-organic frameworks (MOFs), and gas separation membranes—represent the technological bottleneck determining whether these ambitions remain aspirational or become achievable.

Recent data from the UK's Carbon Capture and Storage Association indicates that sorbent degradation rates have improved from 0.5–1% per regeneration cycle in 2020 to 0.1–0.3% in 2024 pilot installations. Membrane CO₂/N₂ selectivity has increased from 20:1 to 50:1 in commercial offerings, with laboratory demonstrations reaching 150:1. Yet these improvements occur against a backdrop of persistent challenges: the energy penalty for capture remains 15–30% of a power plant's output, and capital expenditure for a commercial-scale DAC facility ranges from £400–800 million.

The International Energy Agency projects that meeting net zero targets requires DAC costs to fall below £100 per tonne by 2050. Current first-generation sorbent systems operate at £400–600 per tonne, while emerging solid sorbent and electrochemical approaches target £150–250 per tonne by 2030. The skeptic's question is not whether these targets are technically possible, but whether the materials science can advance quickly enough—and whether the UK's industrial base can manufacture at the required scale.

Key Concepts

Amine Sorbents represent the most mature carbon capture technology, using liquid or solid-supported amine compounds that chemically bind CO₂. Monoethanolamine (MEA) solutions remain the industry standard for post-combustion capture, achieving 85–95% capture rates but requiring substantial thermal energy (3.5–4.0 GJ per tonne CO₂) for regeneration. The skeptic's concern centres on the energy penalty: parasitic loads of 25–40% effectively reduce power plant efficiency below economic viability without carbon pricing mechanisms exceeding £80 per tonne.

Solid Sorbents including zeolites, activated carbons, and functionalised silicas offer lower regeneration energy requirements (1.5–2.5 GJ per tonne) but face durability challenges in humid industrial environments. Temperature-swing adsorption cycles subject materials to mechanical and thermal stress, with current commercial sorbents degrading 30–50% over 2,000 cycles—far short of the 10,000+ cycles needed for economic operation.

Metal-Organic Frameworks (MOFs) represent the next frontier in sorbent design, offering tunable pore structures with theoretical CO₂ capacities exceeding 8 mmol/g—double that of conventional sorbents. However, MOF synthesis costs remain £500–2,000 per kilogram versus £10–50 for activated carbons, and water stability issues limit deployment in real-world flue gas conditions. The skeptic notes that a decade of MOF research has produced hundreds of promising laboratory materials but fewer than five commercial products.

Membrane Separation technology exploits differential permeation rates to separate CO₂ from mixed gas streams. Polymeric membranes dominate commercial applications, though mixed-matrix membranes incorporating MOFs or zeolites show enhanced selectivity. The fundamental trade-off between permeability and selectivity (the Robeson upper bound) constrains performance: membranes achieving 1,000 Barrers CO₂ permeability typically show selectivity below 30:1, insufficient for single-stage capture from dilute atmospheric sources.

Energy Penalty and Regeneration remain the central skeptical concerns. Whether using thermal swing (heating sorbents to 100–150°C), pressure swing (cycling between 1–10 bar), or electrochemical approaches, regeneration energy dominates operational costs. For DAC applications capturing CO₂ at 420 ppm concentration, thermodynamic minimum energy is 0.5 GJ per tonne, but practical systems require 5–10 GJ per tonne—a 10–20× efficiency gap that materials innovation must close.

Carbon Capture Materials: Key Performance Indicators

Metric	Current State (2025)	Target (2030)	Net Zero Target (2050)
Cost per tonne CO₂ (DAC)	£400–1,200	£150–250	<£100
Cost per tonne CO₂ (point source)	£40–80	£25–40	£15–25
Sorbent capacity (mmol CO₂/g)	2–4	4–6	>6
Regeneration energy (GJ/tonne)	3.5–6.0	2.0–3.0	1.0–1.5
Sorbent cycle lifetime	1,000–3,000	5,000–8,000	>10,000
Membrane CO₂/N₂ selectivity	30–50:1	80–100:1	>150:1
Membrane permeability (Barrers)	100–500	500–1,000	>1,500
Capture rate efficiency	85–90%	92–95%	>95%

What's Working

Improved Sorbent Durability

The UK's ACORN project at St Fergus, Scotland, has demonstrated amine sorbent systems maintaining 95% capacity after 4,000 cycles—a significant improvement over early deployments. Shell's Cansolv technology, deployed at the Peterhead site, shows degradation rates below 0.15% per cycle through improved solvent formulation and process optimisation. These incremental gains, while insufficient for DAC economics, are proving viable for point-source capture where CO₂ concentrations are 100–1,000× higher than atmospheric levels.

Membrane Selectivity Advances

UK-based researchers at Imperial College and the University of Edinburgh have pioneered facilitated transport membranes that exceed the Robeson upper bound by incorporating amine carriers within polymer matrices. Commercial trials with Membrane Technology and Research (MTR) demonstrate CO₂/N₂ selectivities of 80:1 at industrially relevant temperatures, enabling single-stage capture with 70–80% recovery rates. For natural gas sweetening and biogas upgrading applications, membrane systems now achieve cost parity with amine scrubbing at scales below 500 tonnes CO₂ per day.

Electrochemical Approaches

Verdox and similar startups have demonstrated electrochemical capture systems using quinone-based electrodes that bind CO₂ at low potential and release it upon oxidation. Laboratory demonstrations show regeneration energy requirements of 1.0–1.5 GJ per tonne—a 60–70% reduction versus thermal systems. UK trials at the Drax power station are evaluating hybrid electrochemical-membrane systems targeting £200 per tonne capture costs by 2028.

What's Not Working

Energy Requirements Remain Prohibitive

Despite two decades of optimisation, the thermodynamic realities of separating 420 ppm CO₂ from atmospheric nitrogen impose fundamental energy costs that current materials cannot circumvent. Skeptics point to the disconnect between reported laboratory efficiencies (often measured at ideal conditions: low humidity, pure CO₂ streams, room temperature) and field performance where contaminants, temperature fluctuations, and mechanical wear degrade performance by 30–50%. The UK's Net Zero Teesside project has documented energy penalties 40% higher than design specifications during the first operational year.

Material Degradation Accelerates at Scale

What works for 100 cycles in a university laboratory often fails at 1,000 cycles in an industrial setting. Oxygen exposure degrades amine sorbents through oxidative deamination; sulphur compounds irreversibly poison MOFs; thermal cycling induces micropore collapse in zeolites. The Tees Valley Cluster consortium reported that first-generation solid sorbent cartridges required replacement after 18 months rather than the projected 5-year lifetime, increasing operational expenditure by 300%. These degradation pathways were known from laboratory studies but their interaction effects at scale were systematically underestimated.

Cost per Tonne CO₂ Improvements Stall

The learning rate for carbon capture technologies has proven slower than for renewable energy, where solar PV costs fell 89% between 2010 and 2024. Carbon capture costs have declined approximately 30% over the same period, suggesting either that the technology is less amenable to manufacturing scale economies or that fundamental materials constraints limit improvement trajectories. Skeptics argue that comparing capture to solar panels ignores the thermodynamic floor: there is no minimum energy for solar conversion, but there is an irreducible energy cost for gas separation that approaches 0.5 GJ per tonne for DAC applications.

Key Players

Established Leaders

Climeworks operates the world's largest DAC facility in Iceland (4,000 tonnes CO₂/year) and is constructing the Mammoth plant targeting 36,000 tonnes annually. Their solid sorbent system uses proprietary amine-functionalised filters with demonstrated 3,000+ cycle durability.

Carbon Engineering (acquired by Occidental Petroleum) deploys potassium hydroxide liquid sorbent systems with reported costs of £400–500 per tonne. Their Strathmore facility in Texas represents the first commercial-scale DAC plant targeting 500,000 tonnes annually by 2025.

Svante specialises in point-source capture using solid sorbent rotary contactors, targeting cement and steel applications. Their technology achieves 95% capture rates at £50–70 per tonne for high-concentration industrial streams.

Aker Carbon Capture provides amine-based systems for industrial applications, with UK installations at the Acorn CCS project. Their Just Catch modular units enable deployment at scales from 40,000 to 400,000 tonnes CO₂ annually.

Emerging Startups

Heirloom employs limestone sorbents in an open-air calcination process, leveraging low-cost materials to target £150 per tonne DAC costs. Their passive contactor design reduces capital intensity but requires significant land area.

Sustaera develops electrochemically regenerated solid sorbents for DAC, claiming 50% energy reduction versus thermal systems. UK pilot testing is scheduled for 2026 at the Humber industrial cluster.

Verdox commercialises electroswing adsorption technology using conductive MOF electrodes. Their approach enables continuous operation without thermal cycling, potentially extending sorbent lifetimes beyond 20,000 cycles.

CarbonCapture Inc. has partnered with Storegga for UK deployment of modular DAC units using zeolite-based sorbents with solar-thermal regeneration.

Mission Zero Technologies (UK-based) develops electrochemical capture systems specifically designed for maritime and offshore applications, targeting integration with North Sea infrastructure.

Key Investors and Funders

The UK Department for Energy Security and Net Zero has allocated £2 billion for carbon capture projects through 2028, including the Track-1 and Track-2 cluster programmes. UK Research and Innovation (UKRI) funds academic research through the Engineering and Physical Sciences Research Council (EPSRC), with £50 million committed to next-generation capture materials. Private investors include Breakthrough Energy Ventures (backing Carbon Engineering), Lowercarbon Capital (backing Heirloom), and Amazon Climate Pledge Fund. The US Department of Energy's Carbon Negative Shot initiative provides £3.5 billion for DAC development with indirect technology transfer benefits for UK companies.

Examples

1. Drax Power Station Bioenergy Carbon Capture (UK) The Drax facility in North Yorkshire has piloted C-Capture's novel solvent technology, a non-amine liquid sorbent with 50% lower regeneration energy requirements. Initial trials captured 300 tonnes of CO₂ over 12 months, demonstrating 95% capture efficiency but revealing solvent degradation rates 20% higher than laboratory predictions. The project highlighted the gap between controlled testing and operational reality, with flue gas contaminants (particularly SOx and NOx) accelerating solvent breakdown. Drax has since transitioned to Mitsubishi Heavy Industries' advanced amine system for its full-scale deployment targeting 8 million tonnes annually by 2030.

2. Net Zero Teesside Point-Source Capture The Teesside industrial cluster in northeast England represents the UK's largest integrated carbon capture project, targeting 4 million tonnes CO₂ annually from multiple industrial sources. The project employs Shell Cansolv amine technology for refinery emissions and Svante solid sorbent rotary systems for hydrogen production off-gases. Early operations revealed that sorbent performance varied significantly across emission sources: capture from natural gas combustion achieved 94% efficiency, while capture from steel production reached only 78% due to trace contaminants. The consortium has invested £30 million in sorbent pre-treatment systems to address these integration challenges.

3. Climeworks Orca and Mammoth Facilities (Iceland) While located outside the UK, Climeworks' Icelandic operations provide the clearest data on DAC material performance at scale. The Orca facility's solid amine sorbents demonstrated 2,500 regeneration cycles before requiring replacement—60% of the projected lifetime—with capacity degradation following a non-linear pattern accelerating after 1,800 cycles. The Mammoth expansion incorporates second-generation sorbents with improved humidity tolerance and enhanced heat transfer characteristics. Climeworks reports cost reductions from £800 to £600 per tonne between 2022 and 2024, though critics note this partially reflects carbon credit pricing rather than fundamental technology improvement.

Action Checklist

• Conduct thermodynamic analysis of regeneration energy requirements for your specific CO₂ source concentration and contaminant profile before selecting capture technology
• Request independently verified cycle lifetime data from sorbent vendors, including degradation curves at 1,000, 2,500, and 5,000 cycles under operational conditions
• Evaluate membrane systems for applications with CO₂ concentrations above 10% where selectivity requirements are less stringent
• Include sorbent replacement costs in total cost of ownership calculations—assume 3-year rather than 5-year lifetimes for conservative planning
• Assess local renewable energy availability for regeneration power, as grid electricity costs dominate DAC operational expenditure
• Engage with UK Research and Innovation funding programmes supporting pilot-scale demonstrations of next-generation capture materials
• Monitor electrochemical capture developments, which may disrupt thermal regeneration economics within 5–10 years
• Develop contingency plans for regulatory changes to UK carbon pricing that could shift project economics significantly

FAQ

Q: Will sorbent and membrane costs ever reach parity with renewable energy for emissions reduction? A: Unlikely for absolute cost comparison—even at optimistic £100 per tonne capture costs, preventing a tonne of CO₂ through solar or wind electricity remains cheaper at £20–40 per tonne avoided. However, for hard-to-abate sectors (cement, steel, aviation) and for legacy atmospheric CO₂ removal, capture technologies address emissions that renewables cannot, making direct cost comparison misleading. The relevant question is whether capture costs fall below carbon prices, which at current UK ETS rates of £60–80 per tonne suggests point-source capture is approaching viability while DAC remains uneconomic without policy support.

Q: Are MOFs genuinely promising or perpetually "five years away" from commercialisation? A: Skepticism is warranted. Despite 25 years of MOF research and over 90,000 reported structures, commercial capture applications remain limited to Svante's temperature-vacuum swing systems and niche gas separation applications. The challenges—water stability, synthesis scalability, pelletisation without performance loss—have proven more intractable than initial research suggested. However, focused commercial development by companies like Nuada and MOF Technologies (UK-based) has produced industrially manufacturable materials at £100–200 per kilogram, approaching cost targets for niche applications.

Q: What would fundamentally change the skeptic's assessment? A: Three developments would signal genuine breakthrough: (1) demonstrated sorbent lifetimes exceeding 10,000 cycles at full scale with less than 20% capacity degradation; (2) regeneration energy requirements below 2.0 GJ per tonne for DAC applications confirmed by independent testing; and (3) manufacturing scale-up achieving sorbent costs below £20 per kilogram without compromising performance. Achievement of any two of these milestones would indicate the technology has crossed from laboratory curiosity to industrial readiness.

Q: Should UK investors prioritise point-source capture or DAC technologies? A: Near-term value lies in point-source capture, where CO₂ concentrations are 100–1,000× higher than atmospheric levels, reducing both thermodynamic energy requirements and materials performance demands. The UK's industrial clusters at Teesside, Humberside, and Scotland offer immediate deployment opportunities with existing infrastructure. DAC investment should focus on technology development rather than deployment at scale until costs fall below £200 per tonne—likely not before 2030–2035 based on current learning rates.

Q: How do UK regulatory frameworks affect carbon capture materials development? A: The UK Emissions Trading Scheme (UK ETS) provides carbon pricing signals, while the Contracts for Difference (CfD) mechanism offers revenue certainty for capture projects. However, materials R&D remains underfunded relative to deployment subsidies, creating a gap between laboratory innovation and commercial application. The skeptic notes that £20 billion committed to CCS infrastructure could have funded £2 billion in materials research that might have made the remaining £18 billion more effective.

Sources

• International Energy Agency. (2024). Carbon Capture, Utilisation and Storage: 2024 Update. IEA Publications, Paris.
• UK Carbon Capture and Storage Association. (2024). CCSA Annual Review: UK Carbon Capture Progress and Prospects. London.
• Fasihi, M., Efimova, O., & Breyer, C. (2019). "Techno-economic assessment of CO₂ direct air capture plants." Journal of Cleaner Production, 224, 957–980.
• National Audit Office. (2024). Carbon Capture, Usage and Storage: Government's Progress on Delivery. HC 1456, Session 2023–24.
• Sanz-Pérez, E. S., Murdock, C. R., Didas, S. A., & Jones, C. W. (2016). "Direct capture of CO₂ from ambient air." Chemical Reviews, 116(19), 11840–11876.
• Rochelle, G. T. (2009). "Amine scrubbing for CO₂ capture." Science, 325(5948), 1652–1654.
• Department for Energy Security and Net Zero. (2024). Carbon Capture, Usage and Storage: Net Zero Investment Roadmap. UK Government White Paper.