Advanced Carbon Capture, Utilization, and Storage Technologies: A Review for Sustainable Carbon Cycle Management

Removing CO₂ from a fuel stream prior to combustion is known as pre-combustion capture (Figure 1). In processes like Integrated Gasification Combined Cycle (IGCC) power plants or hydrogen production facilities, fuel (such as coal, natural gas, or biomass) is gasified or reformed to create a synthesis gas (syngas) that is high in subsequently transforms the carbon monoxide into CO₂ and additional hydrogen, enabling the separation of CO₂ from a concentrated, high-pressure stream hydrogen and carbon monoxide. A water-gas shift reaction [7]. Because of the stronger driving force for separation caused by this high partial pressure of CO₂, pre-combustion capture typically uses less energy than post-combustion techniques [8]. Pre-combustion mature technologies frequently use physical solvents (e.g., Rectisol, Selexol, Amine solvents) for absorption, which works well at high pressures [9]. Novel membranes and adsorbents are the focus of recent developments to further increase efficiency and lower costs [7].

The most established and extensively used carbon capture technology for current power plants and industrial facilities is post-combustion capture (Figure 2(a)) [10]. Following combustion, CO₂ is extracted from the flue gas using this method. Large gas volumes must be treated because the flue gas usually contains diluted CO₂ (e.g., 3-15% by volume) at low pressure [8]. The most popular and widely accessible post-combustion method is chemical absorption, which mostly uses aqueous amine solutions (such as monoethanolamine, or MEA). This process uses a lot of energy, especially for solvent regeneration, even though it is very effective and frequently achieves 85–95% CO₂ capture efficiency (Figure 2(b)) [11]-[14]. Research is being done to create new generations of chemical solvents, like biphasic solvents and advanced amine blends, that have better stability, lower regeneration energy requirements, and slower rates of degradation [7].

Burning a fuel in an atmosphere of almost pure oxygen as opposed to air is known as “oxy-fuel combustion.” As a result, the flue gas's composition is drastically changed, becoming mostly composed of CO₂ and water vapour with a much lower nitrogen content [15]. The downstream CO₂ separation is made easier by the lack of nitrogen because water vapour is readily extracted by cooling and compression, producing a high-purity CO₂ stream [8], [16]. The production of pure oxygen, usually through cryogenic air separation units (ASUs), has a high energy demand, which entails a significant capital and operating cost [8], [15], even though this method avoids the energy penalty associated with separating CO₂ from a diluted flue gas stream. In spite of this, research is looking into advanced oxy-combustion cycles like the Allam cycle and alternative oxygen production techniques to increase overall efficiency [7], [16]. Oxy-fuel combustion is still regarded as a promising approach for new builds and particular industrial applications.

Direct Air Capture (DAC) is a technology that takes CO₂ straight from the air, unlike point-source capture techniques [17]. In DAC systems, large fans are typically employed to draw air across sorbent materials that selectively bind to CO₂ (Figure 3). After reaching saturation, the concentrated CO₂ is extracted from the sorbents through heating or depressurization, facilitating its storage or utilization [18]. To address diffuse or historical emissions that cannot be tracked from specific industrial sources and may lead to net-negative emissions, direct air capture is crucial [17]. Recent developments in DAC technology feature the design of scalable and modular units, the introduction of advanced sorbents that significantly reduce energy requirements for regeneration, and better integration with renewable energy sources aimed at minimizing the overall carbon footprint of the capture process [18], [19]. Organizations like Clime works are developing third- generation technologies aimed at significantly reducing energy consumption and enhancing CO₂ capture capacity [19].

Since every carbon capture technology has advantages and disadvantages, selecting one can be challenging. The ideal choice is determined by the fuel type, target capture efficiency, economics, process technological maturity, and application (such as power generation or industrial processes). The key characteristics, advantages, drawbacks, and Technology Readiness Levels (TRLs) of carbon capture techniques according to NASA are contrasted in the Table 1.

Pipelines transporting significant amounts of CO₂ over long distances are the most cost-effective and energy-efficient (Figure 4) [20], [21]. Although dedicated new pipelines are desired to assure integrity and prevent contamination, existing natural gas pipeline infrastructure may be converted or reused for CO₂ transmission [22]. CO₂ is delivered in its dense phase (supercritical or liquid state) to increase density and decrease compression energy, which requires certain pipeline temperature and pressure parameters [20]. CO₂ pipelines for Enhanced Oil Recovery (EOR) projects have proved technological viability and dependability internationally for decades, providing a firm foundation for CCUS infrastructure [21], [22].

Ship transport of CO₂ is a potential alternative to pipelines across enormous bodies of water or to connect geographically spread sources to a central storage hub [23], [24]. Liquid CO₂ is transported by ships in L CO₂ carriers at moderate pressures (7–15 bar) and low temperatures (-50°C) [25]. This routing method can serve numerous smaller CO₂ sources without specialised pipeline connections. Although less developed than pipeline transport for large-scale CCUS, the concept draws inspiration from the LNG shipping sector, which has improved ship design and port infrastructure to increase efficiency and scalability [24], [25].

Every aspect of CO₂ transport infrastructure must be safe. CO₂ is neither flammable nor hazardous at atmospheric concentrations, but its higher density than air can dislodge oxygen and induce suffocating, especially in enclosed or low-lying environments [26]. Ship and pipeline designs must prioritise safety. Strict material standards to avoid brittle fracture, advanced leak detection systems, emergency shutdown processes, and detailed siting and operating risk assessments are examples [26], [27]. Emergency response planning and public awareness are essential for CO₂ transport network safety [27].

Building the CO₂ transit infrastructure needed for extensive CCUS implementation is difficult. Large-scale pipeline networks require a lot of money, land, and laws for where to put them, how to gain authorization, and how to run them [28]. Special loading and unloading terminals, liquefaction facilities at capture locations, and regasification units at storage and use stations are needed for transporting [24]. Governments, humankind mesh, and localus must work together to build a powerful and interconnected CO₂ transit network [29]. We require supportive policies, clear economic incentives, and strategic planning to overcome these issues and accelerate global CO₂ transport solutions [28]-[30].

Geological storage involves burying CO₂ in deep, porous rock formations with impenetrable layers. Two types of geological formations are predicted to store a lot of CO₂:

Monitoring and verification (M&V) systems are necessary to maintain geological storage sites, verify CO₂ confinement, and detect leaks [35]. Surface, shallow subsurface, and deep subsurface methods are used in M&V programs. Geochemical sampling of groundwater and soil gas, seismic surveys, boreholes with pressure and temperature sensors, and surface CO₂ flux measurements are examples [35], [36]. Satellite remote sensing is augmenting broad-area surveillance. M&V data is essential for regulatory compliance, public assurance, and adaptive storage management across decades to millennia [37].

Geological CO₂ storage relies on multiple trapping mechanisms and long-term geological stability that has persisted for thousands of years. Structural and residual trapping initially immobilize the injected CO₂, while solubility and mineral trapping ensure its retention over extended time scales [6], [33], [38]. Over hundreds to thousands of years, the injected CO₂ gradually dissolves into formation waters and reacts with host minerals to form stable carbonate phases, thereby enhancing the permanence of storage [33]. For long-term safety and effectiveness, suitable storage sites must exhibit stable geological conditions, low seismic activity, and thick, competent caprocks [33].

The most well-established commercial use of CO₂ is CO₂-Enhanced Oil Recovery (EOR) [39]. This method involves pumping collected CO₂ into mature oil reservoirs to mix with crude oil, reducing its viscosity and making it easier to extract (Figure 6). The injected CO₂ is trapped in the reservoir, providing geological storage and oil revenue [40]. Although CO₂-EOR can increase recovery factor and prolong oil field life, it also permits the production of fossil fuels; therefore, careful consideration is required to ensure the net climate benefit [39], [41].

The transformation of CO₂ into valuable chemicals, fuels, and materials is a highly promising approach for its utilization. A diverse array of chemicals can be produced with carbon dioxide (CO₂) as a carbon source, including:

The reaction of CO₂ with metal oxides (such as calcium or magnesium oxides, which are often found in naturally occurring minerals or industrial waste) forms stable carbonate minerals (Figure 8) [46]. Because they are environmentally friendly and thermodynamically stable, solid carbonates can safely and permanently sequester CO₂ [40]. Even though reaction kinetics and energy needs limit direct large-scale implementation, research is focused on generating new reaction routes, catalysts, and ex-situ procedures to make this process more effective and economically possible [40], [46].

CO₂ has numerous industrial applications beyond its role as a chemical feedstock. It is widely used in the food and beverage sector (carbonation and refrigeration), agriculture (enhancement of greenhouse plant growth), and manufacturing (metal fabrication and fire suppression). Although these applications consume smaller quantities of CO₂ compared with large-scale capture initiatives, they represent established markets capable of utilizing a portion of the captured CO₂ and thereby contributing to the reduction of overall CCUS costs [2], [47].

The capture source, technology, flue gas CO₂ concentration, and project scale all have a significant impact on CCUS costs. The majority of the CCUS chain is comprised of capture expenses (Figure 9) [48]. While pre-combustion and oxy-fuel combustion may be more integrated and economical for new power plants or industrial operations, post-combustion capture is more costly for existing facilities due to the diluted CO₂ in flue gases [6], [49]. Transport costs are determined by distance, volume, and mode (pipelines are less expensive for large volumes over long distances). Although storage is less expensive, it necessitates long-term monitoring and verification, drilling, injection, and site characterization [48]. The cost of capturing and storing CO₂ varies from 30 to 100 per ton, depending on the region and application. Efforts are being made to reduce these costs through economies of scale and technological advancements [48].

Strong market mechanisms and efficient carbon pricing are key to CCUS implementation. Carbon taxes and emissions trading systems (ETS) incentivize firms to reduce CO₂ emissions, making CCUS cheaper than paying for emissions [50]. Carbon prices boost CCUS investment. In addition to direct carbon pricing, low-carbon fuel standards, tax credits (like the U.S.'s 45Q tax credit), and carbon abatement contracts-for-difference (CfDs) can de-risk CCUS projects and accelerate their commercialization [51], [52].

Scaling CCUS to meet climate targets requires global investment. The construction of capture facilities, transportation networks, and storage sites will require billions of dollars in the upcoming decades [53]. Long lead times and high initial capital expenditures necessitate significant public funding, bank guarantees, and supporting policy frameworks in order to de-risk early projects and draw in capital, even though private investment is essential [54]. Large-scale CCUS infrastructure construction will also be financed through international cooperation and innovative financing techniques like climate funds and green bonds [53].

A constant stream of technology advancements will improve efficiency, lower prices, and expand applicability. This includes creating more durable and energy-dense materials, smarter control systems using AI and machine learning, and manufacturing process advancements that will speed up production and cut unit costs. Miniaturization and mobility may expand use cases.

The potential is huge, but scalability issues must be overcome to achieve widespread use. These hurdles include ensuring a reliable and sustainable raw material supply chain, building robust deployment and maintenance infrastructure, and navigating regional regulatory climates. Industry growth will also depend on workforce development and training.

One of its biggest prospects is seamless integration with renewable energy systems. This technology will stabilise, store, and provide on-demand energy for intermittent renewable sources including solar and wind power. This synergy will improve smart networks, reduce fossil fuel use, and optimize energy delivery.

We need this technology to reach net-zero emissions. It will aid the clean energy economic transition, decarbonizing power generation, transportation, and industry. It can store energy, balance systems, and offer cleaner options to meet ambitious climate targets and prevent climate change.

Several large-scale CCUS initiatives are operational or under development across sectors. Many initiatives aim to capture CO₂ from power stations, natural gas processing facilities, and industrial operations including cement and steel manufacture.