Since the Industrial Revolution began in the mid-18th century, humanity has released more than 1.7 trillion tonnes of carbon dioxide into the atmosphere - a figure that continues to rise by roughly 37 billion tonnes every year. The atmospheric concentration of CO₂ has climbed from a pre-industrial 280 parts per million to over 420 ppm today, a level not seen on Earth in at least 3 million years.

The consequences are measurable and accelerating: average global temperatures have risen approximately 1.2°C above pre-industrial baselines, sea levels are climbing, extreme weather events are intensifying, and agricultural systems are facing disruption on every continent. The window to limit warming to 1.5°C - the threshold beyond which scientists warn of irreversible systemic impacts - is narrowing rapidly.

Against this backdrop, carbon capture has emerged not as a silver bullet, but as one of the most critical tools in the climate technology arsenal. Both the Intergovernmental Panel on Climate Change (IPCC) and the International Energy Agency (IEA) have concluded that achieving net-zero emissions by 2050 is essentially impossible without large-scale deployment of carbon capture technologies. This article explains what carbon capture is, why it matters, how it works, and where the technology stands today.

Carbon capture is the process of intercepting carbon dioxide (CO₂) before it reaches the atmosphere, or removing it directly from the air, and then storing or utilizing it so it cannot contribute to global warming. The broader term - Carbon Capture, Utilization, and Storage (CCUS) - reflects the full lifecycle: capture, then either storage underground or conversion into useful products.
The core logic is straightforward. When fossil fuels are burned in a power plant, cement kiln, steel furnace, or any industrial facility, CO₂ is produced as a combustion byproduct. Conventionally, that CO₂ exits through a flue stack and disperses into the atmosphere. Carbon capture intercepts the gas at the source - or, in more ambitious approaches, pulls it back out of the air after dispersal - and keeps it out of the climate system.
Carbon capture is not a single technology. It is a family of approaches, each suited to different source types, concentration levels, and industrial contexts. The three (3) broad categories are:

• Point-source capture — capturing CO₂ at the location where it is produced (power plants, cement factories, steel mills, refineries)
• Direct Air Capture (DAC) — extracting CO₂ directly from ambient atmospheric air regardless of emission source
• Nature-based and hybrid approaches — enhancing natural carbon sinks through biological processes, including afforestation, soil carbon, and bioenergy with carbon capture (BECCS)

The Math of Net Zero

The IEA's Net Zero Emissions by 2050 scenario requires removing approximately 7.6 billion tonnes of CO₂ per year by 2050 through CCUS technologies — nearly 20 times the capacity that exists today. That gap underscores both the urgency and the scale of the challenge.
But the more important question is: why can't renewable energy and electrification do the job on their own?
The answer lies in what climate scientists call hard-to-abate sectors — industries where CO₂ emissions are inherent to the chemical process itself, not just a byproduct of energy use. Cement production releases CO₂ when limestone (calcium carbonate) is heated — that reaction produces calcium oxide and CO₂ regardless of whether the kiln is powered by solar energy or coal. Steel production using the traditional blast furnace route is similarly locked. Hydrogen and ammonia production from natural gas, aviation fuel, shipping, and heavy chemicals all face similar physical constraints.

"Carbon capture is often the most feasible decarbonization technology for process industries such as cement, steel, and chemical production, where electrification alone cannot eliminate process emissions. — World Economic Forum, 2025"

Carbon capture doesn't just buy time - for these sectors, it is the decarbonization pathway.

The Scale of What's Already Happening

As of early 2025, just over 50 million tonnes of CO₂ capture and storage capacity was operational globally. That's significant, but compared to the 37 billion tonnes emitted annually, it represents roughly 0.14% of global emissions. The IEA projects this capacity must grow to 430 million tonnes by 2030 - nearly a nine-fold increase in five years.
The encouraging news: after a decade of pilot plants and stop-start financing, the number of commercial CCUS facilities and total capture capacity grew sharply in 2025. Several first-of-their-kind projects in cement and waste-to-energy - historically among the hardest sectors to decarbonize - began operations or entered construction during this period.

1. Post-Combustion Capture

This is the most commercially mature and widely deployed method. In post-combustion capture, fuel is burned normally, and CO₂ is separated from the resulting flue gas after combustion occurs. The process works by passing the flue gas through a liquid solvent - most commonly an amine solution - that selectively absorbs CO₂.
How it works:

1. Flue gas (containing typically 4–15% CO₂) enters an absorber tower and contacts the amine solvent.
2. The amine chemically binds to CO₂ molecules, forming a CO₂-rich 'loaded' solution.
3. The loaded solvent is pumped to a regenerator column and heated above 120°C, releasing concentrated CO₂.
4. The 'lean' solvent is recycled back to the absorber, and the concentrated CO₂ stream is compressed for transport.

The primary challenge is the enormous energy requirement of the regeneration step. Heating the solvent to release CO₂ consumes approximately 15–25% of a power plant's output — a significant 'energy penalty.' In late 2024, MIT researchers discovered that adding tris (tris(hydroxymethyl)aminomethane) to a potassium carbonate solution allows CO₂ release at just 60°C instead of 120°C, potentially cutting costs significantly and enabling operation on waste heat or even sunlight.

• Capture efficiency: Up to 95% CO₂ removal
• Best suited for: Retrofit of existing power plants, cement kilns, waste-to-energy facilities, pulp and paper mills

2. Pre-Combustion Capture

Rather than capturing CO₂ after burning fossil fuels, pre-combustion capture transforms the fuel before combustion into a mixture of hydrogen and CO₂ that can be easily separated. The fuel undergoes gasification or steam reforming to produce a synthesis gas (syngas) of carbon monoxide and hydrogen. The syngas passes through a water-gas shift reactor: CO + H₂O → CO₂ + H₂. The resulting CO₂ stream (at high concentration) is separated using physical solvents or membranes, and the remaining hydrogen is burned cleanly with water as the only combustion product.
Pre-combustion capture produces what's called blue hydrogen - hydrogen derived from natural gas with CO₂ emissions captured. This represents a lower-carbon stepping stone that can be produced at industrial scale today.

• Capture efficiency: Up to 90%
• Best suited for: New-build power plants, hydrogen production facilities, IGCC plants

3. Oxy-Fuel Combustion

In conventional combustion, fuel burns in air - which is 78% nitrogen. That nitrogen dilutes the flue gas, making CO₂ separation more energy-intensive. Oxy-fuel combustion eliminates this problem by burning fuel in nearly pure oxygen produced by a cryogenic air separation unit (ASU).
The result is a flue gas composed almost entirely of CO₂ and water vapor - the water is condensed out, leaving a highly concentrated CO₂ stream that requires minimal additional separation. The resulting flue gas can contain 80% to 90% CO₂ (versus 4% to 15% in conventional post-combustion). Technologies such as the Allam Cycle and LEILAC cement kilns exemplify this approach.

• Capture efficiency: 90% to 99%
• Best suited for: New-build power generation, cement kilns, high-temperature industrial processes

4. Direct Air Capture (DAC)

Direct Air Capture takes a fundamentally different approach: it removes CO₂ directly from ambient atmospheric air, regardless of where that CO₂ originated. Because atmospheric CO₂ is dilute (0.04%, or 420 ppm), the energy required to concentrate it is far greater than for industrial flue gases - making this the most powerful and most expensive approach.
Two main DAC pathways exist:

• Solid sorbent: Solid DAC: Air passes over solid sorbent material (amine-functionalized resins or zeolites) that binds CO₂. When saturated, the sorbent is heated or pressure-cycled, releasing concentrated CO₂ and regenerating the sorbent. Climeworks (Switzerland) is the leading commercial deployer.
• Liquid solvent: Liquid DAC: Air passes through a liquid hydroxide solution (potassium hydroxide) that chemically captures CO₂. The carbonate solution is processed through a calciner at very high temperatures to release concentrated CO₂. Carbon Engineering / Occidental's STRATOS facility in Texas is the world's largest DAC plant.

The CCUS industry continues to develop in 2025 as major projects become operational, including the world's largest DAC plant in the United States.

• Capture efficiency: High; however, current costs range from $400–$1,000 per tonne
• Best suited for: Carbon removal credits, net-negative emissions, locations with low-cost renewable energy

5. Bioenergy with Carbon Capture and Storage (BECCS)

BECCS is a hybrid approach with a uniquely powerful property: it can achieve net-negative emissions. The concept grows biomass (trees, crops, grasses) that absorbs CO₂ from the atmosphere during growth, burns that biomass for energy, captures the resulting CO₂ emissions, and stores them permanently underground. The result is atmospheric CO₂ removal - the biomass drew down CO₂ from the air, and that carbon is now sequestered geologically.
BECCS represents roughly 25% of projected CO₂ removal capacity by 2050 in most net-zero scenarios. Limitations include land use competition with food production, water demand, and the need for sustainable biomass supply chains.

6. Enhanced Weathering and Mineralization

Enhanced weathering leverages the natural process by which silicate rocks absorb CO₂ over geological timescales - accelerated by crushing rocks into fine particles and spreading them on agricultural land or ocean surfaces. The CO₂ reacts with the rock surface to form stable carbonates that are sequestered in marine sediments or geological formations.
Mineralization also occurs in basalt rock: when CO₂ is injected into basalt (as in Iceland's CarbFix project), it reacts with the rock's calcium and magnesium content to form stable carbonate minerals within years to decades - providing a permanent, solid form of storage that cannot leak.

Geological Storage

The most common destination for captured CO₂ is deep geological formations - typically at depths of 800 meters or more, where pressure and temperature conditions keep CO₂ in a dense 'supercritical' state that behaves more like a liquid than a gas. Three types of formations are used:

• Saline aquifers: Saline aquifers: Deep porous rock formations saturated with saltwater, offering enormous storage capacity. The Sleipner project in Norway has been injecting CO₂ into a saline aquifer beneath the North Sea since 1996.
• Depleted reservoirs: Depleted oil and gas fields: Existing reservoirs with proven containment capacity and well-characterized geology. Used in many early projects due to existing infrastructure.
• Basalt: Basalt formations: The CarbFix project in Iceland demonstrated that CO₂ injected into basalt mineralizes into stable carbonates within 2 years — far faster than previously believed.

Several US states — West Virginia, Texas, and Arizona — have recently advanced their EPA Class VI well primacy applications for permitting underground CO₂ storage, with West Virginia receiving final approval in early 2025.

CO₂ Utilization: Turning Waste into Value

Not all captured CO₂ needs to be stored — some can be converted into useful products, creating economic value that helps offset capture costs. Current and emerging utilization pathways include:

• Synthetic Fuels (e-fuels): CO₂ combined with green hydrogen to produce jet fuel, diesel, or methanol — creating a circular carbon economy for hard-to-electrify transport sectors.
• Construction Materials: CO₂ mineralized into calcium carbonate and incorporated into concrete aggregates, permanently locking carbon in building materials.
• Enhanced Oil Recovery (EOR): CO₂ injected into oil reservoirs to improve extraction efficiency, generating revenue that helps fund CCS infrastructure.
• Chemicals and Plastics: CO₂ as a feedstock for producing polycarbonates, polyols, and other polymers — replacing fossil feedstocks.
• Food and Beverage: CO₂ used for carbonation of beverages, food preservation, and controlled-atmosphere storage.

One of the most intriguing emerging intersections in carbon capture science involves nanobubble technology. Conventional CO₂ dissolution in water is limited by the inherent solubility of CO₂ at ambient conditions. When CO₂ is introduced into water as conventional bubbles, it rises rapidly and escapes before fully dissolving. Nanobubbles change this dynamic fundamentally.

CO₂ nanobubbles, due to their nanoscale dimensions (less than 200 nanometers in diameter) and unique hollow shell-core structure, exhibit a high surface-to-volume ratio and high internal pressure, resulting in a highly efficient mass transfer rate with swift dispersion in aqueous media.

"Nanobubble technology helps in dissolving high amounts of CO₂ at much lower operating pressure and in 10 times shorter time compared to conventional sparger systems. — ScienceDirect, 2024"

Key nanobubble advantages for carbon capture applications:

• Enhanced Dissolution: Enhanced dissolution: CO₂ nanobubbles dissolve into water far more completely than conventional bubbles, achieving supersaturation of aqueous solutions beyond the inherent CO₂ solubility limit.
• Geological Sequestration: Geological sequestration improvement: In deep saline aquifer or depleted reservoir injection, CO₂ nanobubble dispersions accelerate mineralization and improve the security of long-term storage by increasing contact between CO₂ and formation minerals.
• Algae Biocapture: Algae-based biocapture: CO₂ nanobubbles delivered to microalgae cultures improve photosynthetic efficiency by approximately 50%, dramatically accelerating biological carbon fixation and biofuel feedstock production simultaneously.
• Soil Carbon: Agricultural soil carbon: CO₂ nanobubble irrigation enhances plant root respiration and soil biology, potentially increasing the rate of carbon accumulation in agricultural soils — an underappreciated carbon sink.

The practical implication is significant: nanobubble generators like the NICO series are not merely water treatment devices - they are precision gas-liquid mass transfer systems capable of being configured with CO₂ gas to enhance dissolution, biological sequestration, and geological storage efficiency. For industrial facilities exploring on-site carbon sequestration, algae-integrated biogas systems, or agricultural carbon farming programs, NICO nanobubble technology represents a direct and scalable entry point into the carbon capture economy.

No technology review is complete without acknowledging constraints. Carbon capture faces real challenges that must be addressed for it to fulfill its potential:

• Energy: Energy penalty: Current technologies consume significant energy — post-combustion capture typically reduces net power plant output by 15% to 25%. Without clean energy to power the capture process itself, CCS can become a circular problem.
• Cost: Cost: Even for mature post-combustion technologies, capture costs of $40–$80 per tonne remain above the current carbon price in most markets without subsidy support.
• Storage: Storage permanence: Geological storage must be permanent on millennial timescales. Monitoring and verification infrastructure is still developing, and public acceptance of CO₂ injection near communities remains a challenge.
• Scale: Scale gap: The world currently captures approximately 50 million tonnes per year. Net-zero scenarios require 7+ billion tonnes per year — a 140-fold increase requiring enormous engineering, supply chain, and capital mobilization.
• Policy Context: Not a license to emit: Carbon capture must complement, not substitute for, deep emissions reductions across all sectors. The IPCC is clear: the technology cannot justify continued expansion of fossil fuel infrastructure.