A Comparative Review on Dry Ice Production Methods: Challenges, Sustainability and Future Directions

Abstract

Dry ice, the solid form of carbon dioxide (CO₂), is widely used in cold chain logistics, industrial cleaning, and biomedical preservation. Its production, however, is closely linked to carbon capture, energy-intensive liquefaction, and solidification processes. This review critically evaluates and compares the existing methods of CO₂ capture, including chemical absorption, physical absorption, adsorption, and membrane-based separation as they pertain to dry ice production. This study further assesses liquefaction cycles using refrigerants such as ammonia and R744, highlighting thermodynamic and environmental trade-offs. Solidification techniques are examined in the context of energy consumption, process integration, and product quality. The comparative analysis is supported by extensive tabulated data on operating conditions, CO₂ purity, and sustainability metrics. This review identifies key technical and environmental challenges, such as solvent regeneration, CO₂ leakage, and energy recovery. Thus, it also explores emerging innovations, including hybrid cycles and renewable energy integration, to advance the sustainability of dry ice production. This, in turn, offers strategic insight for optimizing dry ice manufacturing in alignment with low-carbon industrial goals.

1. Introduction

Carbon dioxide (CO₂) is a naturally occurring greenhouse gas that plays a vital role in regulating the Earth’s carbon cycle and maintaining temperature balance [1]. However, since the Industrial Revolution, excessive anthropogenic emissions have significantly increased the atmospheric concentration of CO₂, contributing substantially to global warming and climate instability [2]. In response to the urgent need to reduce greenhouse gas emissions, innovative strategies have emerged that focus on both emission mitigation and carbon management. One such approach is carbon capture and storage (CCS), a process that captures CO₂ from point sources such as fossil fuel power plants, industrial operations, or natural gas processing facilities and either reuses or stores it in geological formations to prevent its release into the atmosphere [3].

Beyond storage, CO₂ can be turned into value-added products, a concept known as carbon utilization [4]. Among the most practical and widely adopted CO₂ utilization methods is its transformation into dry ice [5]. Dry ice, the solid form of CO₂, has long been employed in a wide range of industries due to its unique thermophysical properties. Thus, it is produced by compressing and cooling gaseous CO₂ to form liquid CO₂, which is then rapidly expanded and depressurized to yield solid CO₂ [6]. This solid is subsequently shaped into blocks, pellets, or slices depending on the intended application [6]. A key characteristic of dry ice is its sublimation behavior, as it transitions directly from solid to gas at –78.5 °C without passing through a liquid phase [6]. This eliminates the complications associated with melting and makes it advantageous for cooling and preservation in sensitive environments [7]. In recent years, the global demand for dry ice has grown rapidly due to its versatility and non-toxic, residue-free nature [8]. Hence, its role became particularly prominent during the COVID-19 pandemic, where it was extensively used in the logistics and cold chain management of temperature-sensitive vaccines and biopharmaceuticals [8,9]. The healthcare and pharmaceutical industries rely heavily on dry ice for shipping biologics, reagents, and clinical samples that require consistent ultra-low temperatures [7,8]. Similarly, in the food and beverage sector, dry ice is used to maintain freshness and prevent spoilage during long-haul transport of meat, seafood, and dairy products [10]. Moreover, its application extends to industrial cleaning, where dry ice blasting has become an environmentally friendly and effective alternative to solvent-based methods, particularly in precision manufacturing, aerospace, and restoration services [5,6].

The production of dry ice, however, is not without complexity. Its upstream supply chain begins with the selection of an appropriate CO₂ source [11]. Notably, several industrial processes emit CO₂ with varying levels of purity, pressure, and flowrate, all of which affect the viability of capture and conversion [12]. Major CO₂ sources include power plants, natural gas treatment facilities, cement and steel plants, and, to a lesser extent, bioenergy and fermentation industries [13,14]. These sources differ in terms of CO₂ concentration and impurities, which influence the selection of suitable capture technologies. Common CO₂ capture methods include absorption using chemical solvents, adsorption using solid sorbents, and membrane separation, each offering trade-offs in terms of energy demand, recovery efficiency, and operational stability [11,12]. Following capture, the next step involves liquefaction, a critical phase in preparing CO₂ for solidification [15]. Thus, liquefaction can be achieved using either external cooling systems or internal thermodynamic cycles [16]. External liquefaction relies on refrigeration units to reduce CO₂ temperature below its condensation point, whereas internal liquefaction exploits system pressure and heat exchange dynamics to enable phase change with reduced external energy input [11,12]. The final step is solidification, typically carried out by depressurizing liquid CO₂ in a controlled chamber, causing it to instantly freeze into a snow-like solid, which is then compressed into usable shapes [15]. Despite its environmental benefits as a CO₂ utilization pathway, dry ice production faces several challenges. These include high electricity and cooling demands, large capital expenditures for cryogenic infrastructure, and the need for continuous CO₂ supply [17]. Operational safety is another concern, as CO₂ can pose asphyxiation risks in poorly ventilated areas [18]. From a sustainability standpoint, reliance on fossil-derived CO₂ and grid electricity for production undercuts the climate benefits of dry ice unless renewable energy and circular economy strategies are integrated into the process [17].

The primary objective of this review is to critically evaluate the end-to-end process of dry ice production with a focus on sustainability, energy efficiency, and process innovation. While numerous technical studies have explored individual aspects such as CO₂ capture or dry ice handling, a review that connects upstream sourcing with downstream application, framed within environmental and economic contexts, remains lacking [19]. Therefore, this review aims to fill that gap by presenting a unified analysis that bridges technology, sustainability, and industrial relevance. The structure of this review is as follows: Section 2 provides a detailed overview of dry ice applications, global market dynamics, and the importance of selecting suitable CO₂ sources. Section 3 outlines the production pathway, including CO₂ capture, liquefaction, and solidification, and compares competing technologies. Section 4 discusses the key technical, economic, and environmental challenges. Section 5 highlights sustainability strategies such as renewable energy integration and policy support. Finally, Section 6 explores innovations and future perspectives for advancing scalable and environmentally responsible dry ice production.

2. Overview of Dry Ice and Its Applications

Dry ice, the solid form of carbon dioxide (CO₂), is widely utilized across multiple sectors due to its unique properties, including its non-toxic nature, ability to sublimate directly into gas, and capacity to provide intense cooling without leaving any residue [20]. These characteristics make it highly valuable for temperature-sensitive applications and clean handling environments [21].

2.1. Properties of Dry Ice

Understanding the properties of dry ice is essential for evaluating its behavior and suitability across various settings, including industrial processes, food processing facilities, and refrigeration systems [22]. Unlike most materials, dry ice transitions directly from a solid to a gas without passing through a liquid phase, hereby eliminating any residual moisture during use [16,17]. Thus, this unique sublimation process absorbs a substantial amount of heat from the surrounding environment, making dry ice an extremely effective cooling agent [23,24]. In its solid form, dry ice is dense and compact, offering a powerful and portable cooling source [22]. Additionally, dry ice has low thermal conductivity, which slows the transfer of heat through its mass [25]. As a result, when properly insulated, it can maintain cooling effectiveness over extended periods, despite being in contact with warmer surroundings [26].

Table 1. Properties of dry ice.

Property	Value	Implications
Sublimation Point	−78.5 °C at 1 atm	Allows for direct solid-to-gas transition.
Latent Heat of Sublimation	571 kJ/kg	High energy absorption for effective cooling.
Density (Solid)	1560 kg/m3	Compact cooling material.
Specific Heat (Solid)	0.85 J/(g·K)	Limited heat absorption in solid form.
Triple Point	−56.6 °C, 5.18 atm	Only above this pressure can CO2 be liquid.
Vapor Pressure	5.1 atm at −56.6 °C	Requires high pressure to stay liquid.
Thermal Conductivity	0.16 W/(m·K)	Low conductivity, allowing for prolonged cooling.

summarizes the key physical and thermodynamic properties of dry ice, along with their practical implications across different operational contexts [27].

2.2. Applications Across Industries

Due to its unique physicochemical properties and wide-ranging functionality, dry ice serves as a highly versatile and indispensable resource across numerous industrial and commercial sectors [28]. Its ability to sublimate directly into gas without leaving residue, combined with its extremely low temperature, makes it ideal for applications requiring clean, efficient, and powerful cooling [29].

In the transport and cold chain logistics field, dry ice plays a critical role in temperature-sensitive logistics, particularly for the transportation and storage of vaccines, clinical samples, biologics, and reagents [8]. It is also routinely used for laboratory cooling and cryogenic preservation of biological specimens, where maintaining a sterile, moisture-free environment is essential [20,21]. These applications have gained heightened relevance during global health emergencies such as the COVID-19 pandemic, which required robust cold chain systems [9]. In the food preservation and processing field, dry ice is employed for preserving perishable goods, flash freezing meat and seafood, and extending shelf life without chemical preservatives [10]. It also plays a pivotal role in maintaining cold chain integrity during long-distance transport of frozen or chilled products [22,23,24]. Hence, its sublimation characteristics prevent the accumulation of water, making it ideal for packaging that requires cleanliness and moisture control.

In the cleaning, packaging, and cryogenic processing field, dry ice is widely utilized for non-abrasive surface cleaning via dry ice blasting [28]. This method is especially valuable in sectors such as aerospace, automotive, and electronics, where traditional cleaning techniques may damage sensitive components [28]. Additionally, dry ice is used for degassing, shrink fitting, and safe transport of temperature-sensitive equipment or materials [25,26]. Figure 1 illustrates the wide variety of dry ice applications across key industries.

2.2.1. Dry Ice in Transport and Cold Chain Logistics

In transport and cold chain logistics, dry ice is essential for maintaining significantly low temperatures and supporting numerous applications [30,31]. For instance, dry ice ensures safe transportation of vaccines, organs and tissues, as well as it enables the cryopreservation of biological samples and provides continuous cooling for laboratory use [30,32]. Moreover, dry ice is crucial for sterile equipment cleaning, which extends its adaptability in emergency cases and field clinics, making it vitally important in the medical sector [20,21].

Table 2. Functional applications of dry ice in transport and cold chain logistics.

Application	Purpose	Description
Vaccines Transportation	Control temperature during transport	Maintains extremely low temperatures for sensitive vaccines, such as mRNA vaccines, ensuring effectiveness during shipping [30].
Organ Preservation	Viability conservation during transport	Keeps tissues, organs and blood samples at low temperatures to avoid degradation during transport for transplant or medical analysis [30].
Cryosurgery	Long-term storage of biological samples	Freezes and stores biological samples like tissues, cells and DNA, preserving them for medical use or research [20,21].

represents the various key uses and benefits of dry ice in transport and cold chain logistics.

2.2.2. Dry Ice for Food Preservation and Processing

In the food preservation and processing industry, dry ice plays a vital role in improving product quality, safety, and operational efficiency [32]. Thus, its extremely low temperature (–78.5 °C) is essential for rapid freezing processes, where it helps preserve the freshness, texture, and nutritional value of food products [32,33]. Furthermore, dry ice is extensively used in refrigerated shipping to maintain appropriate temperatures and ensure that perishable goods remain frozen or chilled throughout transit [33]. It also has an important function in beverage carbonation, where it enables the controlled infusion of carbon dioxide to achieve the desired level of effervescence [34]. These applications underscore the importance of dry ice in preserving quality, extending shelf life, and maintaining product functionality across the food supply chain.

Table 3. Applications of dry ice for food preservation and processing.

Application	Purpose	Description
Cold Storage	Rapid freezing	-Used for flash freezing perishable items like meats and seafood to preserve freshness, texture, and nutrition [32,33]. -Helps prevent large ice crystals, inhibits microbial growth, preserves flavor, and supports IQF systems [22,28].
Preservation During Transit	Refrigeration in shipping	-Maintains appropriate temperatures during transport for items like meat and dairy [23]. -Avoids residue, works without power, and reduces spoilage [23,29].
Carbonation	Beverage carbonation	-Creates carbonation by sublimating CO2 into the liquid, increasing dissolved CO2 content and forming fizziness [34]. -Displaces oxygen in the beverage, preserving flavor and preventing oxidation, producing visual fog for sensory appeal [34].

represents the various key uses and benefits of dry ice in food preservation and processing.

2.2.3. Dry Ice for Cleaning, Packaging, and Cryogenic Processing

Dry ice plays a critical role in functional processes such as cleaning, packaging, and cryogenic treatment, contributing to improved efficiency, precision, and sustainability across multiple industrial applications. One of the most prominent uses is dry ice blasting, a non-abrasive cleaning method that removes contaminants from machinery, equipment, and surfaces without leaving any residue [35,36,37,38,39,40,41]. This technique is especially valuable in environments where moisture or chemical solvents could damage sensitive components [41]. In addition to cleaning, dry ice is employed in packaging processes, particularly in the production of expanded foam materials [38,39]. Its cooling effect supports structural stability and insulation performance, ensuring product protection and durability during storage and transport [40,42,43]. Moreover, dry ice is used in cryogenic processing, where its extremely low temperature is applied to harden materials such as metals and plastics, enhancing their machinability and dimensional stability [44]. These diverse applications of dry ice contribute significantly to improving productivity, maintaining quality, and enabling advanced manufacturing techniques across the industrial sector.

Table 4. Applications of dry ice for cleaning, packaging, and cryogenic processing.

Application	Purpose	Description
Blasting	Non-abrasive surface cleaning	-Removes contaminants from machinery, equipment, and surfaces without leaving any residue [36]. -Pellets sublimate on contact, embrittling and detaching contaminants [25,26].
Foaming and packaging	Expanded-foam production and cold packaging	-Employed in the production of expanded foam materials. -Ensures structural stability and insulation performance and creates inert packaging environments for sensitive goods [45].
Shrink fitting (Cryogenic Processing)	Material hardening and precise assembly	Hardens materials like metals and plastics and enables shrink fitting by cooling components for tighter tolerances [15].

represents the various key uses and benefits of dry ice in cleaning, packaging, and cryogenic processing applications.

2.3. Global Market and Trends

The dry ice market is experiencing significant growth, driven by its versatility and critical applications across healthcare, food processing, logistics, and manufacturing sectors [46]. Thus, its ability to maintain ultra-low temperatures without the need for mechanical refrigeration makes it indispensable for the transport of temperature-sensitive goods, including vaccines, biological materials, and perishable foods [31,32]. In industrial contexts, dry ice also plays a vital role in non-abrasive equipment cleaning, offering a residue-free and environmentally friendly alternative to chemical-based methods [36]. As sustainability and operational efficiency become increasingly prioritized within global supply chains, the demand for eco-friendly cooling and preservation technologies continues to rise [47,48]. This market evolution reflects not only the adaptability of dry ice but also its growing economic significance in enabling critical operations and driving technological innovation across key sectors.

Economic Relevance

The dry ice market has grown significantly, due to its increasing use in cold chain logistics, healthcare, and the food industry [49]. As customer demand for fresh and high-quality products grows worldwide, the market is likely to increase alongside businesses that require precise temperature control [49]. Market reports have predicted the growth of the cold chain market size. It was estimated to be valued at USD 233.8 billion in 2020 and is projected to reach USD 340.3 billion by 2026, exhibiting a Compound Annual Growth Rate (CAGR) of 7.8% [34,35]. In addition, food and beverage’s e-commerce market size is expected to grow to USD 109.23 billion in 2026 at a CAGR of 17.6%, and the cell and gene therapy market will reach USD 35.67 billion by 2026, exhibiting a CAGR of 33.6% during the forecast period 2019–2026 [50]. Furthermore, dry ice provides economic value by enhancing the efficiency and sustainability of global supply systems. Hence, its temperature-controlled transportation solutions are cost-effective and adaptable, allowing firms to sustain product integrity over great distances, which is especially important in industries dealing with perishable or fragile goods [34,35]. As global supply chains become more integrated, dry ice reduces product losses and improves logistics efficiency, contributing significantly to the economy [50]. Moreover, the environmental benefits of dry ice, including direct sublimation from solid to gas and being manufactured from recycled CO₂, interact with sustainability goals and the growing commitment to minimizing carbon footprints [34,35]. These aspects contribute to the importance of dry ice, not just in operational terms but also in promoting good business practices across industries [34,35].

For instance, in 2024, Asia Pacific dominated the worldwide dry ice market, accounting for 32.64% share, primarily due to increased industrialization and the growing food and beverage industry, which promotes demand for effective cooling systems [34,35]. Additionally, North America experiences an increasing need for dry ice, which is driven by its solid healthcare infrastructure and expansion in the entertainment industry, both of which rely on dry ice for medical logistics and special effects [34,35]. Meanwhile, Europe is expected to see a significant market expansion in the future years, driven by strict food safety standards and a rising pharmaceutical sector that relies more on dry ice for cold chain logistics [50]. Figure 2 represents the growth in dry ice’s market in Asia Pacific from 2019 till 2032 [50].

2.4. Carbon Dioxide Sources for Dry Ice Production

Dry ice has diverse applications as discussed previously, creating a growing demand for sustainable and efficient production methods [51]. To meet this demand, identifying reliable sources of CO₂ emissions is essential, as it is the primary feedstock for dry ice production. Thus, carbon dioxide (CO₂) is one of the greenhouse gases that are among the greatest contributors to global emissions and climate change [52,53]. CO₂ emissions primarily originate from various anthropogenic and natural sources such as power plants, natural gas reserves, transportation, agriculture and many more [54]. Across these different sources, the fraction and flow of CO₂ vary significantly [52]. As seen in the diagram below (Figure 3), power plants (electricity) are the biggest contributors to CO₂ emissions among all other anthropogenic sources [52].

Additionally, natural gas reserves, which are concentrated underground deposits, are known as an abundant and unique natural source of CO₂ [54]. They are distributed across various regions globally and each reserve has its own characteristics especially in terms of the amount and flow of CO₂ in the extracted gas [54].

Consequently, power plants and natural gas reserves emerge as two of the largest sources of CO₂. Due to fossil fuel combustion, power plants are responsible for approximately 40% of global CO₂ emissions [53]. Notably, the CO₂ concentrations of natural gas reserves can range from 5 to 50%, depending on each reserve and its characteristics [53]. Both sources will be analyzed separately followed by a comparison to determine the most suitable option for CO₂ capture and dry ice production later.

Table 5. Comparative table between CO₂ emitted from power plants and natural gas reserves.

Parameters	Coal Power Plants	Natural Gas Reserves
CO2 Flow Rate	High, depending on plant capacity (1–3 Mt CO2/year, 70% of global flow) [58].	High, depending on the reserve (0.5–10+ Mt CO2/year, 25% of global flow) [58].
CO2 Fraction in Stream	10–15% [58].	Can reach up to 50% in sour gas reserves [58].
CO2 Concentration	Low (10–15% due to mixing with nitrogen, oxygen, and trace gases) [58].	High (20–50%, especially in sour gas reserves) [58].
Pressure	Low (near atmospheric in flue gas, 0.1 MPa) [54].	High (>10 MPa, particularly in sour gas reserves) [54].
Impurities	Includes nitrogen (75–80%), sulfur oxides (SOx), and particulates (10–15%) [54].	H2S (up to 20%), hydrocarbons (10–30%), and water vapor (5–10%) [54].
Yield	Moderate to high with post-combustion capture system (50–85% recovery) [54].	High, specifically in sour gas reserves (90–95% recovery) [54].

compares coal power plants and natural gas reserves as potential sources for CO₂ capture, which will be discussed in the upcoming section, highlighting key parameters such as flow rate, CO₂ concentration, pressure and impurities. As a matter of fact, contributing significantly to global CO₂ emissions, coal power plants particularly produce flue gas containing low CO₂ concentrations and at atmospheric pressure, thus presenting challenges in the capture process [55]. In contrast, natural gas reserves, particularly sour gas, offer higher CO₂ concentrations and pressures, making them an attractive source for capture [56]. In addition, the presence of impurities and the recovery yield also vary significantly between the two sources, influencing the selection of the optimal source of CO₂ [57].

From the analyzed data in Table 5, the significantly higher CO₂ concentrations (up to 50%) and pressures (>10 MPa) of natural gas reserves, specifically sour gas, simplify the capture process and reduce energy requirements. On the other hand, flue gas produced from coal power plants has a low CO₂ concentration (10–15%) and approximately atmospheric pressure, thus making the separation process more challenging and less efficient. Moreover, offering a higher recovery yield (90–95%) compared to coal power plants (50–85%), sour gas reserves further support their selection. Although sour gas reserves contain impurities such as H₂S and hydrocarbons, these can often be handled effectively with separation technologies [54]. Accordingly, natural gas reserves, particularly sour gas, may be one of the best sources for dry ice production.

In summary, dry ice’s unique physicochemical characteristics, namely its ability to sublimate directly from solid to gas, its extremely low temperature of −78.5 °C, and its inert, non-toxic nature, form the foundation for its widespread industrial applications [50]. These properties enable its use in functions that demand high-performance cooling, residue-free cleaning, sterile conditions, and moisture control, making it indispensable across sectors including medical logistics, food preservation, manufacturing, and electronics [50]. Beyond its functionality, dry ice offers substantial convenience due to its ease of storage, portability, and compatibility with existing supply chains [50]. Thus, it is also regarded as environmentally friendly, particularly when produced from captured CO₂ emissions, as this contributes to circular carbon usage rather than increasing atmospheric concentrations [51]. Furthermore, dry ice eliminates the need for chemical preservatives and water-based cleaning agents, offering sustainable alternatives to traditional practices [50]. Among various CO₂ sources, sour natural gas represents one of the most promising feedstocks due to its high CO₂ content, natural pressurization, and global abundance, especially in regions like the Middle East and North America [54,58]. As industries seek low-carbon and economically viable solutions for CO₂ utilization, the dry ice pathway stands out for its commercial readiness, minimal infrastructure requirements, and alignment with global decarbonization goals [51,53]. This underscores the growing strategic importance of the dry ice industry as a key pillar in the physical utilization of captured carbon.

3. Dry Ice Production Pathways

Dry ice production is fundamentally dependent on the upstream characteristics of the CO₂ feed stream, making CO₂ capture a critical part of the overall value chain. This section outlines the key methods involved in the production of dry ice from captured carbon dioxide (CO₂). It begins by examining and comparing the main CO₂ capture techniques including absorption, adsorption, and membrane separation. Following the capture stage, the liquefaction process is discussed, focusing on both external and internal liquefaction systems, with attention to energy efficiency, process complexity, and environmental impact. In the context of external liquefaction, commonly used refrigerants are compared based on cooling performance and sustainability. The final method involves the solidification of liquid CO₂ into dry ice through depressurization and expansion. Figure 4 illustrates the methods covered in this section.

3.1. Carbon Dioxide Capture Methods

Once a suitable carbon dioxide (CO₂) source has been identified, the next step in dry ice production involves selecting an appropriate capture method [59,60,61]. Among the widely adopted industrial techniques for CO₂ separation are adsorption, absorption, and membrane separation, as illustrated in Figure 5 [40,41,60].

Adsorption captures CO₂ molecules on the surface of solid materials, such as activated carbon or zeolites [40,41,60]. Absorption, on the other hand, uses either chemical solvents like amines or physical solvents such as Selexol to dissolve CO₂ from gas mixtures [40,41,61]. Meanwhile, other methods, such as membrane separation, employ selectively permeable membranes that separate CO₂ based on differences in molecular size or solubility [40,41]. A comparative assessment of these methods is necessary to identify the potentially most effective option based on energy consumption, process scalability, separation efficiency, and compatibility with varying gas compositions [60,61]. While many of these capture technologies are also used in other CO₂ capture and utilization processes, the focus here is on their applicability and optimization for their subsequent use in dry ice production.

3.1.1. Adsorption

Adsorption is a widely used and effective method for capturing CO₂ due to its high efficiency, scalability, and cost-effectiveness [62,63]. In this process, CO₂ molecules are selectively removed from gas mixtures using solid materials known as adsorbents [42,43,63]. Common adsorbents include zeolites, activated carbon, and metal–organic frameworks (MOFs), each offering different performance characteristics depending on surface area, selectivity, regeneration capacity, and operating conditions [42,43]. In dry ice production, adsorption offers a distinct advantage by providing CO₂ streams with high purity and low moisture content, which are essential for ensuring dry ice structural integrity, minimizing sublimation loss, and optimizing crystallization during depressurization [42,43].

This section compares these materials to identify the most suitable adsorbent for efficient CO₂ capture. The adsorption mechanism is described by the interaction of CO₂ molecules with the surface of the solid medium, followed by a desorption step in which the captured gas is released for storage or further processing [64].

Types of Adsorbents

In any adsorption process, adsorbate molecules are separated from a gas mixture either by forming a bond with the sorbent or by attaching to the solid matrix through weak intermolecular forces [42,43]. CO₂ adsorption can be achieved using several adsorbents such as zeolites, activated carbon, and MOFs [63]. The most important property of an adsorbent is its CO₂ adsorption capacity, which depends strongly on pore structure, surface area, and the degree and type of functionalization [63].

Zeolites, especially 13X and 5A, are microporous crystalline aluminosilicates with surface areas of 700–900 m²/g and high CO₂ selectivity due to cation exchange sites and defined pore structures [65]. Zeolite 13X offers excellent capacity and selectivity, while 5A is more effective under high pressure [66]. These materials also exhibit thermal and chemical stability and can be regenerated through TSA and PSA techniques [65]. However, their sensitivity to moisture can reduce capture efficiency, requiring pretreatment steps that add complexity [67,68].

Activated carbon is another widely used adsorbent with surface areas ranging from 500–2000 m²/g. It captures CO₂ via van der Waals forces and is effective under high pressures and moderate temperatures [46,47]. Furthermore, it is chemically inert, cost-effective, and resistant to degradation [69]. Unlike zeolites, it maintains performance in humid conditions, though it has lower CO₂ selectivity and capacity, making it less suited for high-purity applications [70,71,72,73].

MOFs are advanced porous materials with surface areas exceeding 6000 m²/g and customizable pore sizes and chemistry [51,52,53]. Their tunable structure makes them highly selective and capable of operating under pressure, especially for CO₂/CH₄ separation [74,75,76,77]. Despite their high performance, MOFs face challenges in cost, moisture sensitivity, and scalability, although recent advances have begun addressing these issues [53,54,76].

Recent advances have addressed the moisture sensitivity of traditional MOFs and zeolites by developing hydrophobic metal–organic frameworks (MOFs) and composite materials that perform reliably under humid conditions [78,79,80]. Zeolitic imidazolate frameworks like ZIF-8 exhibit strong hydrophobicity due to their nonpolar pore walls and have shown high CO₂ uptake in the presence of water vapor [77]. Similarly, modified UiO-66-NH₂ structures, incorporating fluorinated functional groups or hydrophobic ligands, have demonstrated enhanced stability and selectivity in humid environments [78]. Moreover, composite MOFs featuring polymer coatings (e.g., polydimethylsiloxane) or surface fluorination have been developed to prevent pore blockage and improve performance under real gas stream conditions [79]. While these strategies improve moisture tolerance, they often introduce trade-offs such as increased synthesis complexity, reduced surface area, and higher material costs [80]. Nonetheless, such materials show strong potential for industrial CO₂ capture applications where exposure to humidity is unavoidable [79].

Emerging porous hybrid materials, such as amine-functionalized MOFs and porous organic polymers, are gaining traction for their improved moisture tolerance and tunable CO₂ capture performance [81]. Diamine-appended frameworks maintain stable adsorption capacity under humid air and exhibit cooperative CO₂ uptake even as humidity increases, thanks to water-influenced adsorption behavior [81]. Amine-modified MOFs such as MOF-808/NH₂ composites (e.g., with graphene oxide) also show enhanced CO₂ capacity and resilience through multiple adsorption–desorption cycles under moist conditions [82]. Meanwhile, amine-functionalized porous organic polymers including hyper-crosslinked polymers, covalent organic frameworks, and POPs demonstrate strong CO₂ selectivity, sustained uptake in humid environments, and structural tunability via grafted or impregnated amines [83]. Although these materials often involve more complex synthesis and higher cost, they offer promising pathways for practical CO₂ capture in moisture-rich industrial gas streams [79].

Comparison of Common Adsorbents for CO₂ Capture

The performance of CO₂ adsorbents depends heavily on operating conditions [80]. Thus, zeolites (e.g., 13X) are optimal for dry gas streams with high CO₂ concentration and flow rate but lose efficiency in humid environments due to moisture sensitivity [84]. Furthermore, activated carbon performs well under humid conditions and moderate flow rates, offering durability and lower cost, though with lower selectivity [85]. MOFs provide high CO₂ capacity and tunability, especially under dry, low-temperature, and high-pressure conditions, but remain costly and less stable in moist environments [73].

Zeolites, activated carbon, and MOFs each present distinct advantages and limitations for CO₂ capture applications. Zeolites offer excellent selectivity and thermal stability but are sensitive to moisture and impurities, which can hinder performance in humid environments [55,56,86]. Activated carbon, while highly durable and effective in moist conditions, generally exhibits lower CO₂ adsorption capacity and selectivity compared to zeolites and MOFs [70]. MOFs, although providing high tunability and adsorption capacity, are limited by high production costs and sensitivity to water exposure [52,53].

While zeolites, particularly type 13X, are widely used due to their high adsorption capacity, industrial maturity, and favorable cost-to-performance ratio, activated carbon remains popular for its moisture tolerance and affordability [87,88,89]. MOFs are being actively researched for advanced applications requiring high precision, despite their current limitations in large-scale deployment [49,51,57]. Current industrial use reflects these trends, with approximately 60% of adsorption-based CO₂ capture systems employing zeolites 13X, followed by 30–40% using activated carbon, and 5–10% using MOFs [49,51,57].

Table 6. Comparison of zeolites, activated carbon and MOFs for CO₂ capture.

Property	Zeolites (13X)	Activated Carbon	MOFs
CO2 Selectivity	High (80–90%) [86].	Moderate (60–70%) [56,57].	High (tunable, 85–95%) [61,62].
CO2 Adsorption Capacity	High (5–6 mmol/g) [86].	Moderate to high (3–5 mmol/g) [56,57].	Very high (8–10 mmol/g) [74].
Operating Pressure	High pressure (30–70 bar) [66,67].	Flexible (10–50 bar) [70].	High pressure (20–50 bar) [61,63].
Thermal Stability	Excellent (>600 °C) [65,67].	Moderate to high (400–500 °C) [57,58].	Moderate (300–400 °C) [61,63].
Chemical Stability	Excellent [77,78,80].	Moderate [57,58].	Moderate to poor [61,63].
Regeneration Energy	Moderate (500–800 kJ/kg) [87].	Low (300–500 kJ/kg) [71].	Moderate to high (800–1000 kJ/kg) [76].
Cost	Low to Moderate (5–10 $/kg) [66,67].	Low (3–7 $/kg) [71].	High (20–50 $/kg) [75,76].
Industrial Maturity	Well-established [89].	Well-established [58,59,60].	Emerging [62,63,64].
Suitability for Natural Gas	Excellent [65,66,67].	Good [57,58,59].	Limited (due to stability) [61,62,63].
Environmental Impact	Low (Reusable, minimal waste) [65,67].	Low (Widely available, renewable potential) [57,59].	Moderate (Complex disposal and energy intensive synthesis) [74,75].
Optimal Operating Conditions	Dry gas streams, high CO2 concentration, high flow rate [84].	Humid environments, moderate pressure, low to moderate flow rate [85].	Dry, low-temperature, high-pressure systems; best under controlled conditions [73].

summarizes the key characteristics of these adsorbents, including surface area, selectivity, regeneration efficiency, cost, and sensitivity to environmental conditions. The choice of a suitable adsorbent depends on multiple factors, including operating pressure, CO₂ concentration, humidity tolerance, and process economics [47,48,49,51].

Adsorption and Desorption

The capture of CO₂ using adsorbents follows a cyclic and efficient adsorption–desorption process. Initially, a gas stream containing a mixture of CO₂ and other gases is introduced at high pressure into a column packed with the selected adsorbent [90]. CO₂ molecules are selectively adsorbed onto the surface of the material due to van der Waals forces, dipole interactions, and size-exclusion effects [91]. This enables the separation of CO₂ from accompanying gases such as methane, nitrogen, or oxygen [90]. When the adsorbent reaches saturation, it must undergo regeneration through a desorption process to restore its capacity [91]. The two principal desorption methods are pressure swing adsorption (PSA) and temperature swing adsorption (TSA) [59,60]. In PSA, the pressure within the column is rapidly reduced to atmospheric or sub-atmospheric levels, weakening the adsorptive forces and allowing the release of CO₂, which is then collected for storage, utilization, or sequestration [91]. PSA is considered energy-efficient, as it minimizes the need for thermal input [59,60]. In contrast, TSA involves heating the adsorbent bed using steam or an external heat source to break the physical bonds between CO₂ molecules and the adsorption sites [59,60]. While effective, TSA typically consumes more energy than PSA due to the additional thermal requirements. Several operational factors influence adsorption performance. Zeolite 13X, for example, achieves optimal results under high pressure and low temperature, enhancing CO₂ uptake [58,59]. However, its sensitivity to moisture can reduce adsorption efficiency, requiring pre-treatment or drying steps [59,60]. Further optimization of cycle duration, energy consumption, and regeneration strategies may be necessary to ensure consistent and effective system performance [91,92].

3.1.2. Absorption

Absorption is one of the most extensively applied methods for CO₂ capture, primarily due to its high efficiency and operational versatility [93]. This process involves the dissolution of CO₂ into a liquid solvent, typically classified into two main categories: chemical solvents and physical solvents [93]. These two solvent types are examined and compared based on multiple performance criteria to determine the most suitable option for CO₂ capture. Detailed consideration is also given to the mechanisms governing both the absorption phase and the subsequent desorption (regeneration) stage. Notably, absorption methods influence dry ice production primarily through variations in CO₂ purity and solvent characteristics, which affect regeneration energy requirements and the thermodynamic efficiency of the overall process [93].

In this section, the absorption method is analyzed for its critical role in dry ice production, with particular emphasis on solvent type, energy consumption, and the achievable CO₂ purity, all of which impact the process efficiency, product quality, and environmental implications.

Types of Absorbents

The chemical absorption process relies on the reactions of CO₂ with the solvent to form weakly bonded intermediate compounds, and these reactions can be reversed by the application of heat to release the CO₂ and regenerate the solvent [61,62]. However, physical solvents selectively absorb CO₂ from the natural gas feed according to Henry’s law so that the absorption capacity increases at high pressure and low temperature [61,62].

Absorbents used in CO₂ capture are broadly categorized into chemical and physical absorbents, each offering distinct mechanisms and performance characteristics [94,95]. Common chemical absorbents include aqueous amine solutions such as monoethanolamine (MEA), diethanolamine (DEA), and methyl diethanolamine (MDEA), which react reversibly with CO₂ to form carbamates or bicarbonates [94,95]. These amines are widely adopted in post-combustion systems due to their high selectivity and regenerability [96]. In contrast, physical absorbents such as Selexol (a dimethyl ether of polyethylene glycol), Rectisol (cold methanol), and propylene carbonate rely on physical solubility without chemical bonding and are effective for high-pressure gas streams like syngas or natural gas [97].

• Comparison of Common Chemical Solvents for CO₂ Capture

To begin with, chemical solvents are widely employed for CO₂ capture due to their strong reactivity with carbon dioxide, thus enabling efficient separation, even at low CO₂ concentrations, which can occur in some reserves [62,63]. The most used chemical solvents include monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA) and blended amines [61,62,63]. MEA is a primary amine that has a fast reaction rate with CO₂ to form carbamates, which makes it very effective for CO₂ capture at low concentration [62,63]. Nevertheless, this solvent requires a significantly high energy to regenerate and is also prone to degradation and corrosion 62,6]. Moreover, DEA is a secondary amine with a moderate reactivity toward CO₂, and it is more degradation-resistant than MEA [98]. This solvent has a slower reaction rate than MEA, making it less efficient in high-capacity systems [98,99]. On the other hand, MDEA, a tertiary amine, is commonly employed in high-pressure processes including natural gas sweetening [63,64]. Although it is more CO₂-selective and requires less energy for regeneration, blending it with activators such as piperazine enhances its reaction kinetics, thus combining efficiency with lower operational cost [63,64]. Therefore, MDEA blended with piperazine may be one of the best blended amines that improves absorption rates and reduces regeneration energy [100,101].

Table 7. Comparative table of chemical solvents for CO₂ capture.

Parameter	MEA	DEA	MDEA	Blended Amines (MDEA + Piperazine)
Reaction Rate with CO2	High (1.2–1.5 kmol/m3. S) [62,63].	Moderate (0.6–0.8 kmol/m3. S) [62,63].	Low (0.2–0.3 kmol/m3. S) [62,63].	Moderate to High (0.8–1.2 kmol/m3. S) [61,62,63].
CO2 Loading Capacity	Moderate (0.4–0.5 mol CO2/mol MEA) [62,63].	Moderate (0.4–0.5 mol CO2/mol DEA) [94].	High (0.8–1 mol CO2/mol MDEA) [61,62,63].	High (1–1.2 mol CO2/mol blended amine) [62,63].
Energy for Regeneration	High (4–4.5 MJ/kg CO2) [98].	Moderate (3–3.5 MJ/kg CO2) [61,62].	Low (2–2.5 MJ/kg CO2) [94].	Low to Moderate (2.5–3 MJ/kg CO2) [98].
Resistance to Degradation	Low (30%) [94].	Moderate (60–70%) [94].	High (85–90%) [62,63].	High (85–90%) [62,63].
Corrosion Risk	High (70–80%) [94].	Moderate (50–60%) [94].	Low (20–30%) [94].	Low to Moderate (25–35%) [62,63].
Cost	Low (1–2 $/kg) [101].	Moderate (2–4 $/kg) [101].	Moderate (2–5 $/kg) [63,64].	Moderate to High (4–6 $/kg) [63,64].
Industrial Application	Suitable for low-pressure gas [63,64].	Suitable for moderate loads [101].	Ideal for high-pressure gas [101].	Suitable for most scenarios [63,64,102].
Environmental Impact	Moderate (High regeneration energy and potential waste) [101].	Moderate (Improved stability over MEA) [62,63].	Low (Minimal degradation, lower waste disposal) [63,64].	Moderate (Might require solvent management) [62,63].

summarizes and compares the diverse parameters of the chemical solvents.

Among the chemical solvents listed in Table 7, MDEA blended with piperazine has been reported as one of the most effective combinations for CO₂ capture when using chemical absorption [103]. This is attributed to its high CO₂ selectivity, favorable energy efficiency, and effectiveness under a wide range of operating conditions [103]. Additionally, it exhibits resistance to thermal degradation and corrosion and has a relatively low environmental footprint [48,49,50]. Multiple studies have identified a mixture of 5% piperazine and 40% MDEA as particularly promising in terms of both CO₂ capture performance and energy requirements [93]. A study conducted by Abd and Naji (2020) showed that the addition of piperazine as an activator increased CO₂ capture efficiency by up to 92.1%, compared to a plant using only 45% MDEA, where efficiency was significantly lower [93]. Nevertheless, Li et al. (2020) reported that while MDEA/PZ systems reduce energy use, their increased viscosity can hinder mass transfer [102].

• Comparison of Common Physical Solvents for CO₂ Capture

Physical solvents are mostly employed when the feed gas is available at high pressure (>20 bar), or when the acid gas partial pressure is 10 bar or greater [104,105]. For CO₂ capture from natural gas reserves, Selexol, Rectisol, and Sulfinol-D are mainly used for bulk removal of CO₂ [104,105]. Selexol is a mixture of dimethyl ethers of polyethylene glycol and is widely employed due to its ability to capture several acid gases like CO₂ and hydrogen sulfide (H₂S) [65,66,106]. This physical solvent also exhibits a low vapor pressure, minimizing solvent loss, and offers a simple regeneration process by pressure reduction or moderate heating [66,67]. Rectisol, a methanol-based solvent, is mainly effective in cold, high-pressure conditions, achieving high CO₂ and impurity removal efficiency [68,69,107,108]. Sulfinol-D is a hybrid solvent combining MDEA for chemical absorption, Sulfolane for physical absorption, and water as a carrier [104,105]. It is particularly effective for high-pressure streams and simultaneous removal of acid gases, although it may be less cost-effective than Selexol due to heat-based regeneration and is more prone to corrosion [67,68].

The selection among these solvents depends on factors such as temperature, pressure, and impurity levels. Each physical solvent has characteristics that make it suitable for specific operating conditions and CO₂ purity targets [109]. Sulfinol-D offers a balance between CO₂ selectivity, energy efficiency, and operational flexibility [110]. Selexol is more cost-effective, especially at high pressures, although it may co-absorb hydrocarbons, potentially lowering CO₂ purity. Rectisol, while offering high-purity CO₂, operates at cryogenic conditions, which increases system complexity and energy use [111].

As shown in

Table 8. Comparative table between Sulfinol-D, Selexol and Rectisol for CO₂ capture.

Criteria	Sulfinol-D	Selexol	Rectisol
CO2 Selectivity	High (90–95%) -Selective chemical and physical interaction with CO2 [65,66].	Moderate (70–80%) -May absorb impurities [104].	High (85–90%) [107].
CO2 Capture Efficiency	High (85–90%) -Effective for acid gas removal [65,66].	Moderate to High (75–85%) -Efficient at high pressures [104].	Moderate to High (75–85%) -Effective for high-pressure, low-temperature streams [68,69].
Operating Pressure	Moderate to High (10–60 bar) -Versatile under natural gas conditions [106].	High (20–70 bar) -Performs best at high pressures [66,67].	High (20–70 bar) -Designed for high-pressure and cryogenic conditions [108].
Operating Temperature	Ambient (25–50 °C) -Limited cooling required [66,67].	Ambient to moderate cooling (10–40 °C) [66,67].	Low -Requires cryogenic conditions (−40 to −70 °C) [108].
Regeneration Process	Thermal regeneration (1.8–2.5 MJ/kg CO2) -Heat required for CO2 release [105].	Pressure swing (1.5–2 MJ/kg CO2) -Reducing pressure to release CO2 [106].	Pressure and temperature swing -Cryogenic heating needed (4–5 MJ/kg CO2) [112].
Energy Requirements	Moderate Due to mix of chemical and physical interactions (1.8–2.5 MJ/kg CO2) [65,66].	Low to Moderate (1.5–2.5 MJ/kg CO2) [105].	High Due to cryogenic cooling and heating (4–5 MJ/kg CO2) [69,70].
Hydrocarbon Co-Adsorption	Moderate (10–15%) [106].	Potentially high (20–30%) -Hydrocarbons may dissolve in the solvent [65,66].	Low (5–10%) [107].
Purity of Captured CO2	High (90–95%) -Reliable for pure CO2 streams [66,67].	Moderate (70–85%) -Impurities may need further purification [65,66,67].	Moderate to High (85–95%) [68,69].
Operating Cost	Moderate (40–55 $/ton CO2) -Balanced performance and maintenance costs [67,68].	Low to Moderate (30–50 $/ton CO2) -May require post-treatment [106].	High (60–100 $/ton CO2) -Expensive cryogenic setup and energy demand [68,70].
Solvent Stability	High (85–90%) -Effective for repeated cycles, minimal degradation [104].	High (90–95%) [65,66].	High (90–95%) [108].
Suitability for Low CO2 Concentration	High -Effective across a range of CO2 concentrations [105].	Moderate -Best at higher CO2 concentrations [104].	Moderate -Best at higher CO2 concentrations [69,70].

, Selexol appears to be a potentially suitable physical solvent, if physical absorption is selected for CO₂ capture, since it performs efficiently at elevated pressures and requires moderate energy for regeneration. Although it may co-absorb hydrocarbons, its ability to handle high CO₂ concentrations and relatively low operating costs make it an optimal choice for processes where high-purity CO₂ is not the main target.

Evaluating Chemical and Physical Solvents for CO₂ Capture

Chemical and physical solvents each offer specific advantages and limitations, depending on factors such as operating pressure, CO₂ concentration, and the required purity of the captured gas [113]. Chemical solvents like MDEA blended with piperazine are widely recognized for their high selectivity and ability to produce high-purity CO₂ streams [101]. In contrast, physical solvents such as Selexol provide a more cost-effective solution, with lower energy demands for regeneration, although they may not achieve comparable levels of CO₂ purity [68,69]. As a matter of fact, strong chemical interactions with CO₂ ensure excellent selectivity and minimal hydrocarbon co-absorption [63,64]. Among chemical solvents, MDEA blended with piperazine is particularly versatile, performing effectively across a wide range of CO₂ concentrations and under moderate operating pressures [64,65]. In contrast, physical solvents offer advantages in high-pressure applications due to their low energy requirements, as regeneration is typically achieved through pressure swing rather than thermal heating, Selexol being a key example [68,69]. However, Selexol and similar physical solvents often exhibit lower CO₂ purity because they co-absorb impurities, necessitating additional purification steps [106]. Therefore, given the objective of achieving high-purity CO₂, chemical solvents, especially MDEA blended with piperazine, may be one of the most suitable options when absorption is selected for CO₂ capture, offering an optimal balance of performance, selectivity, and cost.

Table 9. Advantages and disadvantages of chemical and physical solvents for CO₂ capture.

Criteria	Chemical Solvents	Physical Solvents
Advantages	- High CO2 selectivity, ensuring high purity CO2 (specially with MDEA + piperazine) [48,49]. - Effective across a wide range of CO2 concentrations [49]. - High CO2 loading capacity (specifically with MDEA + piperazine) [47,48]. - Proven scalability and industrial maturity [48]. - Efficient under moderate pressures and temperatures (specifically with MDEA + piperazine) [49,50].	- Cost-effective for high-pressure, high CO2 streams (specifically with Selexol) [51,54]. - Energy efficient regeneration process (specifically with Selexol) [52,53]. - Minimal degradation and corrosion risk [54]. - Can be adapted in various natural gas conditions [52,53,54].
Disadvantages	- Moderate energy requirements for regeneration [47,48]. - Potential solvent degradation over time (specifically MEA) [48,49]. - Higher operating costs compared to physical solvents [49,50].	- Moderate CO2 selectivity, requiring post-treatment (specifically Selexol) [51]. - Can absorb hydrocarbons (specifically Selexol) [52]. - Limited suitability for low CO2 concentrations (Selexol) [54].

shows the benefits and drawbacks of chemical and physical solvents, illustrating their respective strengths and weaknesses in the context of CO₂ capture.

Adsorption and Desorption

The absorption process of CO₂ begins as the CO₂-rich feed gas enters the bottom of an absorber column and flows upward, while the absorbent is introduced at the top and flows downward in a countercurrent direction [71,72,73,114]. As the gas ascends through the column, CO₂ encounters the solvent, which selectively absorbs it [72,114,115]. The treated, CO₂-lean gas then exits from the top of the absorber [72,73,115], while the CO₂-rich solution collects at the bottom and is directed to the regeneration unit [72,73,74]. The next stage is desorption, or regeneration, where the absorbed CO₂ is separated from the solvent so that the latter can be reused [73]. This step occurs in a stripper (or regenerator) column [116,117]. First, the CO₂-rich solvent is preheated using a heat exchanger before entering the stripper [73,74]. Then, steam is introduced into the stripper to supply the heat required to break the chemical bonds between CO₂ and the solvent, thereby releasing CO₂ in its gaseous form and regenerating the solvent [73,74,114]. The desorbed CO₂ exits from the top of the stripper as a purified gas, while the regenerated solvent is cooled in the heat exchanger and recirculated back to the absorber column [73,74].

Figure 6 illustrates this absorption–desorption cycle, specifically using a chemical solvent system (a rich amine solution).

3.1.3. Membrane Separation

Membrane separation is an advanced and efficient technique for capturing CO₂ from natural gas reserves [118]. This method utilizes specialized membranes that selectively permit certain gases to permeate while retaining others, thereby enabling effective CO₂ separation from gas mixtures [119]. The most used membrane types include polymeric, inorganic, and mixed matrix membranes, each with distinct properties and performance characteristics [120]. Membrane-based CO₂ capture introduces unique trade-offs for dry ice production, as it yields variable purity levels and may require polishing stages to meet the stringent purity and pressure requirements needed for efficient liquefaction and solidification [120].

In this section, we examine the features of each membrane type and compare their suitability for CO₂ capture. These membranes are evaluated in this review with respect to their ability to deliver high-purity CO₂ required for downstream liquefaction and solidification into dry ice.

Types of Membranes

Membrane technologies are attractive for CO₂ capture due to their low energy requirements, compact footprint, and suitability for remote or unmanned sites [120,121,122]. Membranes fall into three categories: polymeric, inorganic, and mixed matrix membranes (MMMs) [119].

Polymeric membranes, made from materials like cellulose acetate and polyimides, are widely used due to their low cost and scalability [75,76,77]. They operate via the solution-diffusion mechanism, where CO₂ diffuses faster than CH₄ due to its higher solubility and smaller size [75,76,77]. However, their performance may degrade under high temperatures or in the presence of contaminants [76,77].

Inorganic membranes, such as zeolite and ceramic types, offer excellent thermal and chemical stability and are ideal for harsh conditions [123]. They function through molecular sieving or selective adsorption and diffusion, allowing CO₂ to pass due to its smaller size [79,80]. Their brittleness and high cost can be limiting factors [79,80].

Mixed matrix membranes (MMMs) combine polymeric matrices with inorganic fillers (e.g., MOFs, zeolites) to enhance selectivity and permeability [124,125,126]. MMMs balance cost and performance, showing promise for CO₂ capture despite ongoing development for commercial-scale use [82,83,127,128].

Comparison of Common Membranes for CO₂ Capture

In order to evaluate membranes for CO₂ capture, it is essential to compare their performance in terms of selectivity, permeability, operational stability, and cost-effectiveness [129]. Polymeric, inorganic, and mixed matrix membranes each offer distinct advantages and challenges, and understanding their characteristics is key to identifying the most suitable option for efficient and cost-effective CO₂ capture under varying operating conditions [130].

Table 10. Comparative table for the types of membranes for CO₂ capture.

Aspect	Polymeric Membranes	Inorganic Membranes	Mixed Matrix Membranes (MMMs)
Selectivity	Moderate (40–60%) [75,76,77].	High (80–95%) [124].	High (75–90%) [81,83].
Permeability	Moderate (100–500 Barrer) -Balance between diffusion and solubility [121].	High (500–2000 Barrer) -Depends on pore structure [78,79].	High (400–1500 Barrer) -Improved by embedded fillers [126].
Thermal Stability	Moderate (80–120 °C) -Sensitive to high temperatures [76,77].	High (200–600 °C) [124].	Moderate (120–200 °C) [127].
Chemical Stability	Prone to degradation (60–80%) [76,77].	High (90–95%) -Corrosion-resistant [124].	Improved (80–90%) -Depends on filler compatibility [128].
Cost	Low (50–100 $/m2) -Affordable and scalable [119].	High (200–500 $/m2) -Expensive materials and fabrication [125].	Moderate (100–250 $/m2) -Balance between polymeric and inorganic [82,83].
Operational Flexibility	High (85–95%) [75,77].	Low (50–70%) (brittle) [78,79].	Moderate (70–85%) [81,83].
Commercial Availability	Widely used (90–95% adoption in industry) [119].	Limited use (30–50% adoption) [125].	Under development for scale-up (10–30% adoption) [127].
Environmental Impact	Moderate -Prone to waste generation [76,77].	Low -Minimal waste but energy-intensive [124].	Moderate -High energy needs [128].

presents a comparative analysis of the three membrane types discussed previously. The selection of an appropriate membrane depends on balancing the factors outlined in the table. Polymeric membranes exhibit moderate selectivity and permeability but are widely used in industry due to their cost-effectiveness, scalability, ease of deployment, and moderate environmental impact [75,76,77]. In contrast, inorganic membranes offer high selectivity, excellent thermal stability, and low environmental impact, making them suitable for CO₂ capture under harsh conditions [78,79]. However, their high cost, limited scalability, and brittleness reduce their practicality for large-scale industrial applications [79,80]. Mixed matrix membranes combine features of both polymeric and inorganic membranes, offering improved selectivity and permeability while maintaining reasonable cost and environmental impact [81,83]. Despite these advantages, mixed matrix membranes remain under development and require further validation regarding their long-term stability and commercial readiness [82,83].

Considering current industrial demands, polymeric membranes remain among the most suitable for CO₂ capture due to their affordability, scalability, and established performance. Nevertheless, mixed matrix membranes present a promising alternative for future applications, particularly in cases where higher performance is desired and cost is less of a constraint [127].

Recent innovations in MMMs have focused on enhancing polymer–filler compatibility and scaling production for CO₂ capture [127,129,130]. New strategies, such as embedding graphene oxide-modified MOFs into polymer matrices, promote improved interfacial adhesion and enable higher permeability and selectivity in CO₂/N₂ separation [131]. Advanced fabrication methods like electrospinning and 3D printing are being explored to overcome manufacturing and scalability challenges [132]. For example, electrospinning allows for membrane production with fine-resolution control and increased throughput, while 3D printing offers flexible, customizable geometries suited to industrial-scale manufacturing [132].

3.1.4. Evaluation of Chemical, Physical, and Membrane Methods for CO₂ Capture

The three main methods for CO₂ capture are adsorption, absorption, and membrane separation [133]. Each technique was examined individually, with attention to commonly used materials and their reported performance in terms of efficiency, CO₂ purity, and practical applicability. In the case of adsorption, zeolites such as type 13X are frequently mentioned in the literature as effective adsorbents [134]. For absorption systems, blends of MDEA with piperazine have been widely studied for their favorable performance [108,135,136]. In membrane-based processes, polymeric membranes are often explored due to their balance of permeability, selectivity, and cost [137]. To provide a broader perspective, a comparative analysis of the three methods is presented based on various criteria such as selectivity, scalability, energy efficiency, and cost-effectiveness.

Table 11. Comparative table of CO₂ capture methods.

Criteria	Absorption	Membrane Separation	Adsorption
CO2 Purity	High -Can reach up to 99% with MDEA + piperazine [63,64].	Moderate (70–80%) -Requires further purification with polymeric membranes [77,78].	High (90–95%) with zeolite 13X [58,59].
Selectivity	High -Up to 95% (MDEA + piperazine) [64,65].	Between 40 and 60% with polymeric membranes (potential hydrocarbon co-separation) [77,78].	High (80–90%) with zeolite 13X [58,59].
Operating Pressure	Moderate to High with MDEA + piperazine (10–50 bar) [64,65].	Moderate to High with polymeric membranes (10–40 bar) [121].	High (30–70 bar) with zeolite 13X [87].
Energy Efficiency	Moderate (70–80%) MDEA + piperazine [65,66].	High (85–90%) No regeneration required with polymeric membranes [78,79].	Moderate (70–80%) High energy for regeneration with zeolite 13X [58,59].
Scalability	Highly scalable and industrially proven (MDEA + piperazine) [98].	Scalable but limited to specific setups (polymeric membranes) [121].	Scalable but less practical for large-scale applications (zeolite 13X) [58,59].
Cost Efficiency	Moderate (60–70%) for MDEA + piperazine [98].	High (75–90%) Low operational costs for polymeric membranes [122].	Moderate (65–75%) High regeneration costs for zeolite 13X [87].
Industrial Maturity	Widely used and well-established (MDEA + piperazine) [63,64,65].	Widely used (polymeric membranes) [78,79].	Well established (zeolite 13X) [58,59].
Adaptability	Effective across varying CO2 concentrations (particularly MDEA + piperazine) [63,64,65].	Best for moderate to high pressures and bulk CO2 removal (polymeric membranes) [77,79].	Effective for specific conditions (zeolite 13X) [57,59].
Environmental Impact	Moderate (solvent management required for MDEA + piperazine) [98].	Low for polymeric membranes [77,78].	Moderate (energy-intensive process with zeolite 13X) [87].

summarizes the main characteristics of each approach as reported in the literature. To evaluate methods for CO₂ capture with a focus on achieving high-purity CO₂, several studies have reported using MDEA blended with piperazine [64,65]. Thus, this chemical solvent has been shown to separate CO₂ effectively while minimizing the absorption of hydrocarbons and other impurities, indicating high selectivity [64,65]. Its ability to produce CO₂ with very high purity after regeneration has also been documented in various applications requiring strict purity specifications [63,64]. In addition, MDEA blended with piperazine has been studied under varying CO₂ concentrations and moderate pressures and temperatures, suggesting its adaptability to different operating conditions [64,65]. Polymeric membranes have been reported as efficient for bulk CO₂ separation and are often described as simple to operate [138]. However, their limited capacity to achieve high CO₂ purity without additional purification steps has been noted in the literature [77,78]. Similarly, zeolites such as type 13X have been investigated for their CO₂ selectivity and purity potential, though the energy-intensive nature of the process and challenges related to scalability for large operations have been identified as limiting factors [58,59].

3.2. Carbon Dioxide Liquefaction

CO₂ liquefaction is widely applied in industrial processes such as dry ice production and liquid CO₂ storage and transport. Unlike general CO₂ liquefaction used in storage or transportation, this review emphasizes liquefaction cycles that are suitable for integration with dry ice manufacturing systems. The process involves compressing and cooling CO₂ gas using compressors and heat exchangers to reach conditions under which it condenses into a liquid, typically just above the critical point [84,85,139]. Pre-cooling and dehydration steps are often included to prevent equipment clogging due to ice formation [140]. Among various methods, internal and external liquefaction are the most frequently employed, representing approximately 58% and 42% of industrial use, respectively, due to their operational flexibility [84,85].

Impurities such as hydrogen sulfide (H₂S), water vapor, and hydrocarbons present in CO₂-rich streams can pose significant challenges during the liquefaction and solidification stages of dry ice production [137,138,141]. At cryogenic temperatures, these impurities may condense or freeze, leading to equipment fouling, clogging of heat exchangers, or the formation of hydrates and solids that reduce overall process efficiency and dry ice purity [141]. For instance, H₂S can form corrosive acidic solutions upon condensation, while heavy hydrocarbons (e.g., C₅⁺) may freeze and obstruct valves or piping [142]. To mitigate these issues, pre-treatment steps such as amine scrubbing, physical absorption, or adsorption using activated alumina or molecular sieves are typically implemented prior to liquefaction [137,138,143,144]. These purification processes are essential to ensure process reliability, extend equipment lifespan, and meet product quality requirements.

3.2.1. External Liquefaction Cycle

The external CO₂ liquefaction process involves converting gaseous CO₂ into liquid form using an external refrigerant, which remains separate from the CO₂ stream [145,146]. Common refrigerants include ammonia (NH₃), propane (C₃H₈), and R-134a, each with distinct thermodynamic and environmental profiles [86,87,88,147]. The process typically begins with CO₂ entering a separator [148,149], where separation by boiling point is considered suitable due to the distinct boiling points of CO₂ and associated gases, such as the −78.5 °C boiling point of CO₂ [89,90]. At cryogenic temperatures, this allows CO₂ to exit from the bottom of the separator while lighter components are removed from the top, potentially achieving a purity of 99.99% [150]. Following separation, CO₂ is compressed to elevate pressure, which enhances heat exchange efficiency and phase transition during liquefaction [149]. The compressed gas is then cooled using intercoolers or water-cooled heat exchangers [149]. A second separator may be employed to eliminate any condensed impurities, including water or hydrocarbons [149]. The stream is subsequently directed to a cryogenic heat exchanger, where CO₂ condenses into liquid form under conditions around −56.4 °C and 5.18 bar, assisted by an external refrigerant that absorbs heat from the CO₂ stream [84,85,88]. The liquefied CO₂ may then be solidified to form dry ice or transferred to storage. The refrigerant is circulated by compression, cooling, and expansion within a closed-loop cycle [88,89,90].

Figure 7 illustrates the process flow of external CO₂ liquefaction using an indirect refrigerant cycle, including key stages such as separation, compression, cooling, condensation, and refrigerant recovery.

Comparison of Common Refrigerants Used in CO₂ External Liquefaction

Several types of refrigerants may be used as they play a crucial role in providing essential cooling to help liquefy CO₂ in the external liquefaction process. These refrigerants enable efficient heat transfer and are essential for achieving the low temperatures required for liquefaction [85,89]. The most used refrigerants globally are ammonia (NH₃), propane (C₃H₈), and R-134a (1,1,1,2-Tetrafluoroethane) [140]. Each of these refrigerants has unique properties such as thermodynamic efficiency, environmental impact, cost effectiveness, safety considerations, and others [86,87,91]. Comparing the three refrigerants based on these parameters is essential to support any selection and design decisions. Ammonia (NH₃) is a commonly used refrigerant in the CO₂ external liquefaction process because of its thermodynamic efficiency [146]. It has been considered energy-efficient for large-scale cooling due to its high latent heat of vaporization [146]. In addition, ammonia is described as environmentally favorable since it has negligible global warming potential (GWP) and zero ozone depletion potential (ODP), aligning with global sustainability goals [146]. It is also broadly available and cost-effective, contributing to its adoption in industrial environments (70% adoption in industries) [146]. However, its corrosive and toxic nature requires proper handling, adequate ventilation systems, safety measures, and corrosion-resistant equipment to minimize operational risks [146]. As for propane, which is also globally used as a refrigerant for CO₂ liquefaction, it has favorable cooling properties, moderate operating pressures, and thermodynamic efficiency, which support its application in industrial processes involving CO₂ [148]. Propane’s moderate availability in global markets (20% adoption in industrial applications) and affordability has been noted in relation to its large-scale use [148]. However, propane is highly flammable, which necessitates strict adherence to safety protocols and the implementation of safety systems to reduce hazards during handling and operation [148]. Regarding R-134a, it is known for its energy efficiency and non-flammability, enhancing its safety profile compared to other refrigerants [147]. It is also compatible with existing systems, reducing the need for retrofitting or specialized equipment [147]. Nevertheless, its relatively high global warming potential (GWP) has resulted in regulatory restrictions in several regions, limiting its use [147]. Despite this, R-134a continues to be used in some industrial setups due to its reliability and ease of integration [147].

Based on the comparative analysis of ammonia (NH₃), propane (C₃H₈), and R-134a (1,1,1,2-Tetrafluoroethane) as refrigerants for the external liquefaction of CO₂, several studies have highlighted ammonia’s favorable performance characteristics [134,135]. With a reported thermodynamic efficiency in the range of 90–95%, as shown in

Table 12. Comparative table of the most used refrigerants.

Parameter	Ammonia (NH3)	Propane (C3H8)	R-134a (1,1,1,2-Tetrafluoroethane)
Thermodynamic Efficiency	90–95% High cooling efficiency for liquefaction [146].	85–90% Effective in moderate setups [148].	75–85% [147].
Environmental Impact	ODP:0, GWP: <1 [146].	ODP:0, GWP: ~3 [148].	ODP:0, GWP: ~1430 [147].
Cost	0.2–0.5 $/kg [146].	1–1.5 $/kg [148].	6–10 $/kg [147].
Safety	Corrosive Requires ventilation systems [146].	Highly flammable Safety risks in operations [148].	Non-flammable [147].
Availability	~70% Globally used in industries [146].	~20% Moderately available in industries [148].	~10% Decreasing availability due to regulations [147].
Operating Pressure	High 200–300 psi [146].	Moderate 150–200 psi [148].	Low 100–200 psi [147].
Applications	Large scale liquefaction [146].	General industrial processes [148].	Small scale applications [147].
Durability/Compatibility	Requires corrosion-resistant systems [146].	Compatible with most setups [148].	Compatible with existing systems but requires frequent servicing [147].

ODP: Ozone Depletion Potential GWP: Global Warming Potential.

, ammonia is associated with high cooling capacity, which has been considered suitable for large-scale CO₂ liquefaction applications [146]. In addition, ammonia has zero ozone depletion potential (ODP) and a global warming potential (GWP) of less than 1 (Table 12), contributing to its classification as an environmentally preferable option [146]. Its low price range of 0.2–0.5 USD/kg and widespread industrial adoption (up to 90%, as indicated in Table 12) further support its economic viability [146]. However, the literature also notes safety concerns related to its corrosive and toxic nature, which may require appropriate system design, ventilation, and maintenance protocols to manage operational risks [146]. Table 12 summarizes the key characteristics and trade-offs associated with the three refrigerants under consideration for external CO₂ liquefaction.

3.2.2. Internal Liquefaction Cycle

The CO₂ internal liquefaction cycle involves the condensation of gaseous CO₂ into its liquid form [90,91]. Unlike external liquefaction systems, this process does not utilize external refrigerants but instead relies on controlling the existing pressure and temperature conditions of the feed components, along with the use of specialized equipment, to achieve liquefaction [90,91].

The process begins with the CO₂ stream entering a separation unit which serves to eliminate any remaining moisture in the gas stream. This step is critical, as the presence of water may lead to freezing during the cooling phase and cause blockages in the system [149]. The separated water is discharged from the bottom of the separator, as indicated in Figure 8 [149]. The dry CO₂ stream is then compressed, which raises its pressure and temperature, preparing it for the subsequent cooling steps [149].

After compression, the CO₂ passes through a heat exchanger or cooler where it is cooled to a temperature near its saturation point, at which liquefaction becomes possible [84,89]. The stream then flows through a throttling valve, where a sudden drop in pressure occurs, resulting in partial condensation and the transformation of CO₂ from gas to liquid [149]. The resulting mixture of gaseous and liquid CO₂ enters a second separator. In this unit, the denser liquid CO₂ collects at the bottom, while the uncondensed gaseous CO₂ remains at the top and may be redirected for further use (Figure 8) [149]. Finally, the liquefied CO₂ exiting from the separator is either solidified or sent to insulated storage tanks, where it is maintained under specific temperature and pressure conditions to preserve its liquid state [149].

3.2.3. Comparison of Common Refrigerants Used in CO₂ Internal Liquefaction

When evaluating CO₂ liquefaction processes, understanding their cost implications is crucial for determining the most efficient and economically viable approach. However, it can be challenging to offer exact estimates of costs for internal as well as external CO₂ liquefaction processes due to differences in equipment selection, size, region, and local energy prices [150]. Although, based on industry statistics and general hypotheses, estimated cost ranges for both systems may be given in terms of capital and maintenance costs, energy consumption, and other parameters mentioned in

Table 13. Comparative table of the two liquefaction processes.

Parameters	Internal Liquefaction	External Liquefaction
Capital Costs (Equipment + Installation)	27.74 mill. EURO [149].	22.31 mill. EURO [149].
Maintenance Cost	6.75 mill. EURO/yr [149].	3.96 mill. EURO/yr [149].
Duty	17,918 kW [149].	10,044 kW [149].
Refrigerant Cost	None	0.2–0.5 $/kg (for NH3) [146].
CO2 Liquefaction Prices	9.97 $/ton [150].	8.77 $/ton [150].
Global Warming Impacts	0.629 kg CO2 -eq kg LCO2−1 [150].	0.608 kg CO2 -eq kg LCO2−1 [150].
CO2 Yield	~85–90% [140].	~95–98% [140].
CO2 Purity	~99.5% [140].	~99.8% [140].
Ease of Operation	Requires specialized monitoring [151].	Simplified due to refrigerant use [151].
Flexibility	Less adaptable to varying operational needs [151].	Highly adaptable for different setups [151].

below. Although internal liquefaction avoids refrigerant costs, its higher capital cost (27.74 million EUR vs. 22.32 million EUR), maintenance cost (6.75 million EUR/yr vs. 3.96 million EUR/yr), and energy consumption (17,918 kW vs. 10,044 kW) make it less cost-effective than the external liquefaction process [86,89]. Despite having an additional refrigerant cost (0.2–0.5 USD/kg for NH₃), external liquefaction process offers a more economical solution due to its lower capital investment and energy usage [86,89]. Additionally, CO₂ liquefaction prices, which refer to the cost per ton of CO₂ processed through the liquefaction system, are lower for external liquefaction (8.77 USD/ton vs. 9.97 USD/ton), thus enhancing its overall cost-efficiency [150]. Furthermore, external liquefaction, for instance, demonstrates potential advantages such as a slightly reduced global warming impact [89,90]. In addition, it may achieve higher CO₂ yield (95–98%) and purity (99.8%), which are crucial for applications that require high-quality CO₂ [140]. While internal liquefaction is effective, it may require specialized monitoring and is less adaptable to varying operational needs [151]. This comparison highlights the importance of assessing the trade-offs between cost, environmental impact, and operational requirements when selecting a liquefaction process. In summary, external liquefaction uses indirect cooling with external refrigerants and generally offers lower costs, energy use, and environmental impact, while internal liquefaction relies on pressure reduction and internal heat exchange without a refrigerant loop but incurs higher costs and energy use.

3.3. Carbon Dioxide Solidification

The dry ice production process begins by rapidly depressurizing liquid CO₂ through a control valve [92,93,152]. This sudden pressure drop to atmospheric levels results in a temperature decrease due to the Joule-Thomson effect, which describes the cooling of a gas during expansion without heat transfer or work production [153,154,155]. As a result, a portion of the liquid CO₂ vaporizes, while the remaining part solidifies into a snow-like form [154,155]. Under these conditions, CO₂ reaches its sublimation point at atmospheric pressure (−78.5 °C, 1.013 bar), as illustrated in Figure 9 [92,93,156]. In cases where immediate solidification is not required, liquid CO₂ can be stored in specialized tanks at low temperatures and elevated pressures (−20 °C, 20 bar), either for future applications or for solidification at a later stage [154]. In addition, the snow-like CO₂ can be collected as residue or directed for further processing [154]. In various industries, mechanical presses are used to compress powdered CO₂ into blocks or pellets, which are among the most produced forms [92,93]. Dry ice blocks are large rectangular units weighing between 10 and 50 pounds, while dry ice pellets are small cylindrical shapes with typical diameters ranging from 3 to 16 mm [92,93]. These presses apply substantial force to ensure that the dry ice is densely compacted and suitable for a wide range of applications [92,93]. This process has been described as an efficient method for converting liquid CO₂ into solid CO₂ (dry ice), with relatively low energy input [154].

The solidification method plays a crucial role in determining dry ice morphology and directly affects its sublimation behavior and cooling performance [157]. Pelletized dry ice, whether compressed snow or small extruded cylinders, has a higher surface-area-to-volume ratio, resulting in significantly faster sublimation rates (often 3–8% mass loss per day) and more rapid cooling effects [150,151]. Such behavior is desirable for cleaning and blasting applications, where quick thermal shock enhances effectiveness [158]. In contrast, forming dense dry ice into blocks produces lower surface area per unit mass, resulting in slower sublimation and extended cold retention which is ideal for storage, transport, or preservation scenarios [157]. These fundamental differences in morphology and sublimation characteristics make it essential to select the appropriate dry ice form based on intended end use: fast-acting pellets for blasting versus long-lived blocks for sustained cooling.

4. Key Challenges in Dry Ice Production

Dry ice production faces numerous challenges that impact its efficiency and sustainability. These challenges fall into four main categories: technical, economic, environmental, and operational [158]. From a technical perspective, the process requires high energy input, and achieving high-purity CO₂ is complex [159]. Additionally, from an economic perspective, raw CO₂ sourcing and high capital investments make large-scale production costly [160]. Moreover, energy-intensive methods contribute to carbon emissions, and inefficient capture processes lead to waste, presenting significant environmental challenges [158]. From an operational perspective, handling high-pressure systems and integrating advanced technologies pose safety risks [161]. Therefore, discussing and addressing these challenges is crucial for improving the sustainability, scalability, and economic feasibility of dry ice production [159].

The choice of CO₂ capture method can impact the downstream quality of dry ice, particularly in terms of purity and residual gas content [162]. Impurities such as N₂, O₂, and methane which are common in streams from pre-combustion, post-combustion, or oxy-fuel capture systems can reduce the density of solid CO₂ and potentially alter its sublimation rate and structural hardness [162]. Porter et al. (2015) demonstrate that CO₂ purity varies significantly by capture technology and impurities may hamper downstream phase behavior and solid quality [163]. However, detailed studies correlating capture-derived purity differences to dry ice sublimation performance or mechanical properties remain scarce, underscoring a need for targeted research in this area.

4.1. Technical Challenges

The production of dry ice presents several technical challenges, primarily related to energy consumption and CO₂ purity requirements, which are critical for cost and efficiency [164]. The liquefaction stage alone accounts for up to 70% of total process energy, requiring approximately 190–700 MJ per ton of CO₂ (~53–194 kWh/t), depending on gas concentration and cooling system design [164]. Additionally, dry ice production efficiency drops significantly when CO₂ purity falls below 95%, as contaminants such as SOₓ, NOₓ, and hydrocarbons impair refrigeration performance and product quality, particularly in food-grade or pharmaceutical applications [165]. To achieve ≥99% purity, advanced separation systems (e.g., adsorption or cryogenic distillation) are necessary, which can increase capital and operating costs by 30–40% [100,101]. These quantified challenges clearly demonstrate the technical hurdles inherent in sustainable dry ice production.

4.2. Economic Barriers

Dry ice production faces several economic challenges that significantly affect its feasibility, particularly for small- and medium-scale operations [166,167]. The cost of capturing CO₂ varies widely depending on the source; high-purity sources like natural gas processing offer lower costs at around $15–25 per ton, while diluted flue gas streams may raise the cost to $40–120 per ton due to additional purification requirements [168]. Moreover, capital investment for setting up a liquefaction plant capable of producing 100,000 tons of dry ice per year can reach $10.6 million, with energy consumption during liquefaction averaging around 112 kWh per ton of CO₂ processed [169].

Table 14. Economic indicators impacting dry ice production.

Parameter	Value/Range	Reference
CO2 Capture Cost (natural gas)	$15–25 per ton	[168]
CO2 Capture Cost (flue gas)	$40–120 per ton	[168]
Capital Cost (100,000 tons/year plant)	$10.6 million	[169]
Energy Consumption (Liquefaction)	112 kWh per ton CO2	[169]
Cost Increase for >99% CO2 Purity	+30–40%	[170]

reveals the economic parameters affecting dry ice production.

4.3. Environmental Impact

The environmental footprint of dry ice production is significantly impacted by upstream CO₂ supply, capture technology, and energy consumption. Thus, emissions of methane (CH₄), particularly when CO₂ is absorbed during natural gas processing, are one of the main environmental issues [171]. If not adequately contained, methane’s global warming potential (GWP) over a 100-year period is 28–36 times more than that of CO₂, greatly increasing the impact on the climate [172]. Furthermore, amine-based solvents, which are frequently employed in CO₂ capture, might break down under heat or oxidative conditions to release toxic substances including recognized carcinogens N-nitrosamines and N-nitramines [173].

The carbon footprint of the dry ice production chain is another important concern. Significant CO₂ emissions per ton of dry ice generated can be caused by system inefficiencies and energy consumption, such as leaks, grids powered by fossil fuels, and a lack of gas recovery [174]. According to lifecycle estimates, production and refrigerant-related emissions alone account for about 0.15 t CO₂ per ton of dry ice produced, with the possibility of additional unmeasured losses [158]. Mitigation techniques that emphasize maximizing CO₂ collection efficiency, using renewable energy sources, and reducing solvent degradation through process optimization are required considering these issues.

Table 15. Environmental impacts and mitigation strategies in dry ice production.

Environmental Impact	Causes	Consequences	Mitigation Measures	Reference
Methane Emissions	Sweet gas escaping absorber units	High GWP (28–36x CO2), contributes to climate change	Install methane recovery systems; regular leak detection and repair (LDAR) programs	[172]
Chemical Degradation of Amine Solvent	Oxidative/thermal breakdown in absorber/regenerator	Formation of toxic by-products like N-nitrosamines (carcinogenic)	Use corrosion inhibitors, limit oxygen exposure, and regularly replace degraded amine	[173]
CO2 Emissions from Inefficiencies	Incomplete capture, energy-intensive liquefaction	Emission of 0.3–0.5 tons CO2 per ton dry ice; decreased process sustainability	Improve capture rate >90%, integrate renewables, recycle CO2 losses	[158]

highlights the environmental impacts and mitigation strategies, along with the causes and consequences, during the production of dry ice.

4.4. Operational and Safety Concerns

Operating a dry ice production plant involves unique safety risks due to the use of high-pressure CO₂ systems and cryogenic temperatures [175]. Dry ice is kept below –78.5 °C, and CO₂ is frequently stored and transported at pressures higher than 57 bar, both of which, if improperly managed, can cause explosions, frostbite, and equipment failure [176]. Yet, industry guidance from IIAR (2023) argues that with modern pressure relief systems and training programs, these risks are largely manageable, contradicting older studies which emphasize them as critical hazards [177]. Industry statistics indicate that human mistake or malfunctioning pressure equipment account for more than 35–46% of occurrences in gas-handling plants [178]. Furthermore, control failures or incompatibilities are frequently the result of integrating new automation technologies into older CO₂ collecting systems, particularly if staff members are not retrained [179]. For the plant to operate safely and continuously, these operational risks must be effectively mitigated.

Table 16. Key operational and safety concerns in dry ice production and mitigation strategies.

Concern	Cause	Consequences	Recommendations	Reference
Handling of high-pressure systems	CO2 compression and storage at ≥57 bar	Explosion risk, equipment rupture, injury	Install pressure relief valves, regular inspections, operator training	[176]
Low-temperature CO2 storage	Solid CO2 stored below −78.5 °C	Frostbite, material embrittlement, PPE failure	Use cryo-rated materials, enforce PPE use, thermal hazard protocols	[176]
Integration of new tech in outdated systems	Retrofitting modern systems into legacy plants	Control failure, inefficiencies, downtime	Perform compatibility audits, phased upgrades, retrain staff	[179]
Inadequate emergency protocols	No drills or safety systems	Delayed leak response, safety incidents	Conduct emergency drills, develop SOPs, install CO2 detectors	[178]

outlines the major risks, their causes and consequences, and appropriate mitigation strategies.

5. Sustainability Considerations

Building upon the previously discussed challenges in dry ice production, this section focuses on strategies and principles proposed in the literature to address these issues through sustainable practices. These approaches emphasize the importance of environmental sustainability, the adoption of circular economy concepts, and the implementation of green technologies aimed at reducing energy consumption and emissions [180,181]. In addition, the literature highlights the role of regulations and policies in guiding the industry toward more responsible and environmentally conscious operations [181]. Collectively, these efforts support the transition toward an environmentally, economically and socially sustainable dry ice

LCA evaluations highlight the fact that when dry ice is generated from captured CO₂ using energy-efficient liquefaction pathways, it can deliver a lower global warming potential (GWP) compared to conventional refrigeration technologies [182]. The inherent benefit lies in dry ice’s passive cooling mechanism, subliming at –78.5 °C, eliminating the need for electrically powered compressors and thereby reducing indirect emissions during distribution and storage [182]. Additionally, the absence of high-GWP refrigerants further minimizes the use-phase climate impact, aligning with LCA criteria for low-carbon cooling alternatives [182]. Quantitative assessments indicate that producing 1 ton of dry ice from captured CO₂ can avoid several hundred kilograms of CO₂-equivalent emissions compared to mechanical refrigeration, especially when renewable electricity powers the liquefaction units [182]. Moreover, LCA data show that the liquefaction and compression stages alone can account for more than 65–70% of the total energy footprint, making optimization of these stages critical for environmental performance [182]. From a life cycle perspective, the production phase is identified as the dominant contributor to overall environmental impact, and thus energy consumption efficiency here is critical for improving LCA outcomes [158]. EIGA’s environmental management guidance emphasizes maximizing thermal integration, reducing CO₂ bleed, and optimizing liquefaction cycles to lower energy demand per unit of dry ice produced [158]. Incorporating these LCA strategies enables a quantitatively optimized dry ice supply chain, minimizing emissions, enhancing resource utilization, and reinforcing its role as a sustainable CO₂ utilization pathway.

5.1. Environmental Sustainability and Circular Economy

By adopting practices that reduce greenhouse gas emissions and conserve natural resources, environmental sustainability aims to minimize the ecological footprint of the dry ice production process. Recycling CO₂ from industrial processes or power plants has been identified as a key strategy to convert a major pollutant into a valuable feedstock for dry ice production [183]. This approach not only reduces emissions but also supports the principles of a circular carbon economy, where waste is reimagined as a resource [183]. Furthermore, integrating renewable energy sources such as solar or wind into the production process further enhances sustainability by decreasing reliance on fossil fuels and reducing overall lifecycle emissions [184]. These strategies contribute directly to many Sustainable Development Goals (SDGs), specifically SDG 7 (Affordable and Clean Energy), SDG 12 (Responsible Consumption and Production), and SDG 13 (Climate Action), by fostering clean energy transitions, promoting efficient resource use, and supporting climate change mitigation efforts [181].

Adopting circular economy principles is considered essential not only for reducing environmental impact but also for creating regenerative production systems [183]. The approach emphasizes resource reuse, waste reduction, and the continuous circulation of CO₂ within the system [183]. Moreover, it supports industrial symbiosis, where by-products from one sector become valuable inputs for another, generating economic and environmental co-benefits.

Table 17. Circular economy strategies in dry ice production.

Strategy	Description	Benefits	Relevance to Circular Economy	Directly Targeted SDGs	Reference
Closed-Loop CO2 Production System	Recycle CO2 within the plant through recovery and reuse after sublimation	Minimizes resource consumption and reduces waste	Maintains CO2 in continuous operational cycle	SDG 12, SDG 13	[183]
Waste-to-Product CO2 Utilization	Capture CO2 from waste streams for use in dry ice production	Reduces overall emissions; valorizes waste	Enables upcycling of industrial emissions	SDG 12, SDG 9, SDG 13	[183]
Integration with Other Industries	Partner with nearby facilities for CO2 sourcing and reuse	Saves transport costs; improves efficiency	Encourages industrial symbiosis and resource sharing	SDG 9, SDG 12, SDG 13	[183]
Process Optimization and Monitoring	Use sensors and controls to track CO2 recovery and reuse rates	Enhances system reliability and conservation	Supports data-driven circular operation	SDG 12, SDG 9, SDG 13	[181]
Renewable Energy Integration	Power processes with solar, wind, or other renewables	Reduces fossil energy dependence and emissions	Enables clean, renewable-driven CO2 production	SDG 7, SDG 12, SDG 13	[184]
Enabling Policy and Regulation	Support via carbon pricing, carbon credits, and circular economy mandates	Strengthens business case; incentivizes action	Fosters institutional adoption of circular systems	SDG 12, SDG 13, SDG 17	[181]

outlines key circular economy strategies relevant to the dry ice production process.

5.2. Green Technologies

Adopting green solutions that maximize energy use and reduce emissions is crucial to lowering the environmental impact of dry ice production. Cascade refrigeration systems are one efficient technique that improves the overall coefficient of performance by easily reaching ultra-low temperatures (down to −170 °C) through the employment of numerous vapor-compression stages [185]. Cryogenic heat integration, which reuses cold streams from nitrogen removal or air separation units in CO₂ liquefaction systems, is another significant breakthrough that has been shown to save up to 5% of energy every cycle [186]. Additionally, integrating renewable energy considerably lowers lifecycle CO₂ emissions and supports SDGs 7 and 13 by using wind or solar electricity to power compression and cooling [187]. Implementing energy optimization technologies such advanced process control (APC) systems and variable-speed drives (VSDs) can increase plant efficiency by roughly 10% to 20%, leading to significant energy savings [188]. These smart technologies enable data-driven energy management, reduce energy waste, and promote long-term sustainability. These green innovations exemplify the principles of eco-efficiency, climate-smart engineering, and sustainable industrial transformation aligned with SDG 9 (Industry, Innovation and Infrastructure) and SDG 12 (Responsible Consumption and Production).

5.3. Policy Drivers and Regulation

Regulation and policy are essential for promoting the sustainability of dry ice manufacturing, especially when it comes to influencing the sourcing, capture, and use of CO₂. Carbon pricing, now roughly €90 per ton of CO₂, is enforced by the EU Emissions Trading System (ETS) in the EU, which promotes emitters, including those that supply CO₂ for dry ice, to make investments in carbon capture systems and lower-emission technologies [189]. The 45Q Tax Credit, which provides financial incentives of up to $85 per ton of CO₂ captured and either geologically preserved or repurposed, is comparable in the United States and provides economic justification for CO₂ utilization operations like dry ice manufacture [190]. Nevertheless, there are drawbacks to both regulatory systems: the EU ETS requires intricate emissions monitoring and allowance trading, which may be taxing for small companies, and the 45Q tax credit is frequently underutilized because of eligibility limitations, expensive upfront expenses, and complicated administration [119,120,191]. Enhancing industry-wide adoption of green technologies and promoting alignment with SDGs 9, 12, and 13 which are related to innovation, responsible production, and climate action would be made possible by improving access to these programs, such as by streamlining 45Q compliance [192].

6. Innovations and Future Perspectives

This section explores recent advancements that shape the future of dry ice production. As global demand for sustainable industrial solutions grows, innovation is playing a key role in improving efficiency, reducing emissions, and broadening the scope of applications [121,122,193]. Recent technological developments include the use of artificial intelligence (AI) for process optimization, the implementation of modular production systems, and the integration of renewable energy sources such as solar and wind power [121,123,194]. In addition, emerging applications of dry ice such as in additive manufacturing and carbon sequestration are attracting increasing interest [195]. The importance of academic–industry collaboration and strategies for scaling up production while maintaining environmental and economic viability are also being addressed in the current literature.

Emerging technologies such as metal–organic frameworks (MOFs) and mixed matrix membranes (MMMs) offer promising performance for CO₂ capture but face significant industrialization barriers [196]. Scalability issues, high synthesis costs, long fabrication times, and challenges in material stability under real gas stream conditions hinder their widespread deployment [196]. In addition, limited compatibility between fillers and polymer matrices in MMMs continues to affect membrane performance and manufacturability [197]. On a regional scale, while the Asia-Pacific market dominates in terms of dry ice demand and technological innovation, regions like Africa and South America remain underrepresented due to underdeveloped logistics networks, insufficient CO₂ sourcing infrastructure, and affordability constraints [198]. These gaps limit the adoption of advanced CO₂ capture and utilization technologies, including dry ice production, despite growing industrial and healthcare needs.

Technological Breakthroughs and Renewable Energy Integration

Technological developments are revolutionizing the production of dry ice by making systems more intelligent, effective, and adaptable. For instance, in experimental projects at coal-fired power plants, the incorporation of artificial intelligence (AI) has resulted in a 36.3% decrease in energy usage and a 16.7% improvement in CO₂ capture efficiency [199]. Simultaneously, local deployment of standardized systems (100–360 t/day capacity) is made possible by small, modular CO₂ liquefaction units, such those provided by Linde Engineering, significantly increasing scalability and lowering logistical challenges [200]. In addition, CO₂ operations powered by renewable energy are already feasible. For example, to produce climate-neutral dry ice, POET’s bio-CO₂ dry ice factories in the US use CO₂ made from corn ethanol and renewable power [201]. Moreover, AI-driven control systems have been deployed in coal-fired plants like Vistra’s Martin Lake facility, enhancing operational efficiency and reducing CO₂ emissions by over 2% thanks to real-time heat-rate optimization [202]. Additionally, standardized modular liquefaction units enable decentralized production, reducing transport-related CO₂ emissions and supporting rapid deployment near feedstock sources [203].

In parallel with these technological developments, dry ice is experiencing a transformation in its application landscape, expanding beyond conventional uses in cold chain logistics and food preservation [199]. Thus, emerging sectors now exploit its unique thermophysical properties for advanced manufacturing and environmental solutions [204]. In additive manufacturing, for example, dry ice is being used in 3D printing post-processing to improve surface precision and eliminate particulate residue without abrasive damage, thereby enhancing final product quality [178,179]. In the context of carbon management, solid CO₂ is being investigated as a transportable medium for injection into underground formations, supporting long-term geological carbon sequestration [205]. Additionally, in the semiconductor industry, dry ice plays a growing role in non-residual cleaning of sensitive components, offering a damage-free alternative to conventional chemical-based methods [206]. These applications not only demonstrate dry ice’s increasing relevance in high-tech and sustainability-oriented sectors but also reveal the material’s potential to contribute to cleaner and more efficient industrial practices.

Table 18. Innovative and emerging applications of dry ice.

Category	Innovation	Description	Benefits	Reference
Technological Breakthroughs	AI-Driven Optimization	Implementation of AI-based systems in pilot-scale carbon capture operations	Increases CO2 capture efficiency by 16.7% and reduces energy consumption by 36.3%	[199]
	Modular Liquefaction Units	Compact CO2 liquefaction plants designed for decentralized deployment, with 100–360 t/day capacity	Allow rapid installation, improved scalability, and reduced transport-related emissions	[200]
	Renewable-Powered CO2 Sourcing	Dry ice facilities powered by renewable electricity and fed with bio-CO2 from ethanol production	Enables carbon-neutral dry ice generation aligned with sustainability goals	[201]
	AI-Controlled Operations	AI-assisted heat-rate optimization systems used in industrial power plants	Enhances energy efficiency and lower CO2 emissions by over 2%	[202]
Emerging Applications	Additive Manufacturing	Usage of dry ice in 3D printing post-processing and thermal control	Enhances precision, avoids surface damage and improves cleaning methods	[205]
	Carbon Sequestration	Solid CO2 used for transportation and injection into storage formations	Supports long-term CO2 removal and mitigates climate change	[205]
	Semiconductor Manufacturing	Utilized for cleaning delicate electronic components with no residue	Reduces risk of damage and contamination during production	[206]

summarizes these technological breakthroughs and emerging applications, highlighting their benefits and alignment with future directions in dry ice production and utilization.

7. Conclusions

This review critically evaluated the entire dry ice production pathway from CO₂ sourcing and capture to liquefaction and solidification through the lens of energy efficiency, environmental sustainability, and industrial scalability. The findings clearly indicate that while dry ice offers a promising avenue for carbon utilization, its production is still highly dependent on fossil-based CO₂ sources and energy-intensive processes. Among the capture technologies, chemical absorption using MDEA blended with piperazine emerged as one of the most effective methods for high-purity CO₂ streams. External liquefaction, particularly with ammonia as a refrigerant, was identified as the most thermodynamically efficient and environmentally responsible option for large-scale operations. However, trade-offs related to safety, cost, and infrastructure requirements persist. Despite technological advancements, dry ice production remains challenged by high operational costs, CO₂ leakage risks, and the need for continuous cooling infrastructure. To address these issues, this review emphasized sustainability strategies including renewable energy integration, solvent recycling, and smart process control. Additionally, opportunities for future research lie in developing multifunctional capture membranes, exploring alternative refrigerants with ultra-low GWP, and integrating dry ice production with broader carbon management systems such as direct air capture and bioenergy with CCS (BECCS). In conclusion, achieving a sustainable dry ice supply chain demands a multi-pronged approach that combines technological innovation, environmental stewardship, and policy support. This review serves as a foundational reference for engineers, researchers, and policymakers working toward environmentally responsible carbon utilization and reinforces the role of dry ice production as a transitional yet critical component of a low-carbon future.