Carbon dioxide utilization: a review of technologies, barriers, and policies for its deployment

1 Introduction

Carbon dioxide (CO₂) emissions by anthropogenic activities into the atmosphere are believed to be the main cause of global warming and a major contributor to the climate crisis (Ghommem et al., 2012). A substantial portion of these emissions can be attributed to the consumption of fossil fuels in power generation (e.g., electrical power, heating, or cooling), industry (particularly in goods manufacturing), and the transportation sector. CO₂ emissions have increased from 20.5 Gt in 1990 to 37.9 Gt in 2023. If no immediate actions are adopted, forecasts estimate that CO₂ emissions could increase to approximately 50 Gt in 2050 [Valluri et al., 2022; Lu et al., 2022; International Energy Agency (IEA), 2024a; International Energy Agency (IEA), 2020a].

Since the United Nations Conference of the Parties (COP) in Paris 2015, part of the United Nations Framework Convention on Climate Change, several countries have committed to reducing their dependence on fossil fuels and decreasing GHG emissions (Amanatidis, 2019). Various initiatives followed the 2015 Paris Agreement, aiming at limiting the increase in global temperatures below 2 °C by 2050 and further decreasing the dependence on fossil fuels (Amanatidis, 2019; United Nations, n.d.). Within this framework, as a part of the European Green Deal, the European Union (EU) plans to reduce CO₂ emissions by 55% by 2030, leading to carbon neutrality by 2050 (European Commission, n.d.; European Commission, n.d.).

However, despite these international targets, current global policies and commitments remain insufficient. Recent assessments by the Climate Action Tracker (CAT) estimate that existing policies could result in approximately 2.6 °C warming above pre-industrial levels by 2,100, substantially exceeding the Paris Agreement objectives (Climate Action Tracker, 2025).

From a technological perspective, one effective approach to reducing GHG emissions and achieving carbon neutrality is via Carbon Capture and Utilization (CCU) (Cuéllar-Franca and Azapagic, 2015; Huang and Tan, 2014). In recent years, CCU has gathered significant attention and is recognized as an important solution as part of the European Strategic Energy Technology (SET) Plan (Priority 9) (Chauvy and De Weireld, 2020; European Commission, n.d.).

CCU involves capturing high-purity carbon dioxide from various sources, including direct air capture or fossil fuel/biofuel-combustion processes (Zhang et al., 2020; Mikulčić et al., 2019). The captured CO₂ is then transported and utilized in ways that positively impact the environment and/or the economy, such as in fuel synthesis, chemical industries, or by injection in hydrocarbon reservoir formations for enhanced oil recovery (EOR) (Alberici et al., 2017; Osman et al., 2021). Additionally, CCU can also be incorporated with Renewable Energy Systems (RES) to create value-added products (Mikulčić et al., 2019). CCU can also act as a “spark plug” for the development of infrastructures that can be later scaled up for permanent storage of carbon (i.e., carbon capture and storage (CCS)) or it is attractive alternative for regions where CCS is not possible (Mikulčić et al., 2019; Hepburn et al., 2019). The advantages of CCU include generating revenue, reducing CO₂ emissions from the industrial sector, and decreasing dependence on fossil fuels (Chauvy and De Weireld, 2020; Hepburn et al., 2019). In the case the process is powered by biofuels, Bioenergy with Carbon Capture and Utilization (BECCU) and Bioenergy with Carbon Capture and Storage (BECCS) can result in carbon-neutral or carbon-negative emissions (Moreira et al., 2016; Kuparinen et al., 2019). The current global CO₂ utilization is estimated to be around 250 Mt./y in 2023, with urea manufacturing accounting for approximately 130 Mt./y (~52%) and EOR 80 Mt./y (~32%) (International Energy Agency (IEA), 2024b; Boston Consulting Group (BCG), 2024). Despite the various potential CO₂ applications, the amounts required by these industries are still negligible compared to current carbon emission levels. On the contrary, the IPCC optimistically estimates that capture and storage will account for 5,000-10000 Mt./y by the middle of this century (Osman et al., 2021; Intergovernmental Panel on Climate Change (IPCC). Climate Change, 2014). To achieve these ambitious targets, numerous CCU projects are operating globally, jointly with funding of research and development (R&D) programs to promote CCU technological pathways. Most of these projects are dominated by EOR applications considering their significant CO₂ utilization capacity (Table 1).

Table 1. CCU Projects around the globe (Yusuf and Ibrahim, 2023; Global CCS Institute, 2024; Liquid Wind, n.d.; Dziejarski et al., 2023; Basque Hydrogen Corridor (BH2C), 2024; Interfax, 2023; Datong Foreign Investment Promotion Bureau, 2023; Petronor, n.d.; NTPC, n.d.; Synhelion, n.d.; CO₂Value Europe, n.d.).

*trial, potential, pilot-scale, * experiment/lab-scale.

We review below the most cited works that cover CCU technology on different conversion and/or utilization pathways, new innovative ways to convert CO₂, and the status of the current technology. The review covers carbon utilization via fuels and chemicals and highlights the significantly high-energy demand from renewable sources required to obtain an environmentally sustainable product. It also covers mineralization, concrete materials/carbon curing, EOR, and Enhanced Coal Bed Methane (ECBM), biological conversion using algae, and horticulture. From these utilization pathways, EOR is the only alternative that has achieved commercial-level maturity [International Energy Agency (IEA), 2024b].

Although our work primarily focuses on CCU technologies, several pathways discussed herein overlap with Carbon Dioxide Removal (CDR) strategies when CO₂ is permanently or durably stored, such as mineralization and long-lived construction materials (Digulla and Bringezu, 2023; de Kleijne et al., 2022). Therefore, this review also discusses the potential contribution of selected CCU pathways to net-negative emissions and long-term carbon management.

Moreover, the current literature also examines the pathways from techno-economic, emission reduction, and social perspectives, life cycle assessment (LCA), and the current market. It addresses the current developments, research efforts, and projects worldwide while addressing the challenges, limitations, opportunities, and future direction for successfully deploying CCU technologies. However, despite the numerous studies on CO₂ application, much of the literature lacks a holistic perspective as it concentrates either on an overview or on a few conversion pathways. Additionally, these works do not address the economic aspects of the technology, current developments and projects within the respective pathways, the market potential of CO₂, or the details of a favorable policy that can accelerate the deployment of carbon utilization technologies.

Thus, our work aims to address these gaps comprehensively by: (1) assessing the current state and advancements in CCU technologies; (2) identifying the technological and market barriers to commercialization, and (3) proposing strategies for accelerating the adoption of these technologies through effective policymaking. Furthermore, we evaluate the environmental and economic performance of different CCU pathways, highlight their respective Technology Readiness Levels (TRL) and barriers to commercial adoption, and outline the essential elements of policies needed to support the widespread deployment of CCU technologies.

To facilitate a systematic understanding, we organized our work into sections that address the main aspects of CCU analysis. The next section briefly describes the CO₂ conversion from a thermodynamic perspective and helps understand the CO₂ application, where it is chemically converted into another useful product or used directly in a process (section 4). This section is followed by purity requirements (section 5) for each application, which sets the tone for analyzing the current impact of CCU products via conducted LCA studies (section 6), the current TRL of each application, and barriers hindering the commercial deployment of each technology (section 7). Finally, the projected market for CCU products is overviewed in section 8. Favorable policies for deploying this technology are discussed in section 9. These policies should address raising awareness in both the public and private sectors, providing mandates and economic incentives, and promoting R&D for CCU pathways.

2 Bibliographic analysis

Bibliographic surveys have allowed us to identify current research trends in CO₂ utilization. By examining the volume of publications across various scientific fields, we have outlined both recent and emerging research directions in CO₂ utilization based on published research articles.

We employed the Scopus search engine¹ to identify relevant studies on CO₂ utilization. The following keywords were used with OR function: “CO₂ utilization,” “CO₂ to fuels”, “CO₂ to chemicals”, “CO₂ to polymers”, “CO₂ to cement”, “CO₂ mineralization/carbonation”, “CO₂ for Enhanced Oil Recovery”, “CO₂ for enhanced gas recovery”, “CO₂ to bioproducts”, “CO₂ for horticulture”, “CO₂ utilization policy”, “CO₂ utilization market”, “CO₂ utilization barriers”, and “CO₂ utilization opportunities”.

The search was restricted to original English-language papers published from 2015 to 2024, as shown in Figure 1. There was a total of 2,860 works published, out of which 2,116 were research articles, 374 were review papers, and 194 were conference proceedings. The literature predominantly focused on CO₂ to fuels and CO₂ to chemicals, incorporating keywords such as catalysis, catalyst, hydrogenation, CO₂ reduction, and electrochemical reduction. This was followed by studies on direct injection for EOR and carbonation for cement and aggregates.

For this review, references that had low relevance to CO₂ utilization, focused solely on in-depth analysis of a specific pathway, or presented findings that duplicated those in higher-quality sources were excluded. This approach was taken to streamline the review process and avoid redundancy. The selected subset of references concentrates on CO₂ utilization in fuels and chemicals, which are the dominant topics in the literature. Following this, discussions on EOR and mineralization, such as cement and aggregates, are included. These references provide a balanced representation of technological advancements, economic and environmental assessments, market trends, and policy insights, forming a comprehensive foundation for the analysis in this review.

3 Fundamental thermodynamics of CO₂ utilization

The CO₂ molecule is thermodynamically stable compared to most CO₂-derived products (Aresta et al., 2014; Yousaf et al., 2022). Generally, converting CO₂ into other products requires significant energy input, viable reaction pathways, and the use of catalysts (Figure 2; Song, 2002; Song, 2006).

The Gibbs free energy (ΔG), shown in Figure 2, is the thermodynamic potential that indicates if the CO₂ conversion reaction into various products is spontaneous or not (Song, 2002; Song, 2006). As can be seen, the CO₂ conversion into products that can be later used as fuels is unfavorable. This means that the conversion requires either energy input or reaction with other compounds with higher Gibbs free energy (Song, 2002; Song, 2006). However, the conversion into higher oxidation state mineral products, such as carbonates or oxalates, requires less energy.

While the ΔG represents the theoretical minimum energy required for these reactions, actual processes consume significantly more energy. In practice, the total energy demand depends on factors like reaction rates, mass transfer, and operating conditions. To reduce these energy penalties, advanced catalysts and specialized solvents can be used to modify reaction pathways and stabilize intermediate products, without changing the fundamental thermodynamic limits of the reaction. For example, transition-metal–nitrogen–carbon single-atom catalysts provide well-defined active sites that can facilitate CO₂ electroreduction by promoting CO₂ activation and stabilizing key reaction intermediates, thereby improving catalytic activity and product selectivity (Ji et al., 2025a). Similarly, applying ionic-liquid and deep eutectic solvents enhances overall conversion efficiency by facilitating CO₂ activation, accelerating reaction kinetics, and stabilizing key reaction intermediates (Ji et al., 2025b).

Therefore, the quantitative energy requirements, detailed in Section 7, must be interpreted as process-level demands rather than the thermodynamic potential shown in Figure 2. These values represent a progression from the theoretical minimum ΔG, through additional kinetic requirements like activation barriers, to the actual energy consumed by process operations.

Understanding this thermodynamic perspective is essential when considering CCU pathways in terms of energy, which is one main indicator of techno-economic feasibility of different CCU pathways.

4 Current application landscape of CO₂

CCU is a broad concept incorporating various pathways to utilize captured CO₂ and to produce economically viable products. CO₂ can be converted into different commercial products such as fuels, building materials, and polymers (Figure 3; Do et al., 2022). Otto et al. (2015) evaluated 123 reaction pathways to convert CO₂ into different chemicals (100 for fine chemicals and 23 for bulk chemicals). These conversions are possible with different technological routes such as electrochemical, thermochemical, mineralizing, biological, and other catalytic conversions (i.e., photo, plasma, and piezoelectric) (Zhu, 2019).

According to the International Energy Agency (IEA), CO₂-derived products and services are classified into five categories for carbon utilization (International Energy Agency (IEA), 2019a):

• CO₂-derived fuels
• CO₂-derived chemicals
• Building materials from minerals and CO₂
• Building materials from waste and CO₂
• Crop yield boosting via CO₂

From a carbon-accounting perspective, these pathways may further be classified into the following categories (Bobeck et al., 2019; Bui et al., 2018):

• Carbon-negative products: producing solid inorganic carbonate from captured CO₂ through direct air capture (DAC), BECCS, or emitted CO₂ through biomass, for long-term storage
• Carbon-neutral products: producing a CO₂-based product by capturing atmospheric CO₂ or by mineralizing CO₂ from fossil fuel emissions
• Carbon-reducing products: replacing an existing product with another product with a lower GHG emission factor (e.g., the replacement of polyether polyols by polyether carbonate polyols)
• Temporary carbon storage: producing chemicals or fuels from CO₂ offering temporary storage

The global market for CO₂ products is estimated at 0.8-1.1 trillion dollars, assuming a consumption of 3.7 Gt per year and reducing around 10% of annual global CO₂ emissions (Koytsoumpa et al., 2018). However, the commercialization potential varies significantly across pathways. Geological utilization pathways such as CO₂-EOR benefit from existing industrial value chains, whereas non-geological pathways (fuels, chemicals, polymers, and construction materials) still face challenges as their respective markets are not in line with the investment strategy of industrial and power sectors or regulatory requirements (National Coal Council, 2016).

Several countries and international organizations have identified promising pathways for future CCU deployment. For example, the Ministry of Science and Technology of China highlighted CO₂-EOR, enhanced coal-bed methane recovery, mineralization, and microalgae cultivation as strategic utilization pathways (Yan, 2013). Similarly, the European Commission emphasized CCU to mitigate climatic impacts by reducing the consumption of fossil fuel, and the importance of policies and funding to promote CCU (European Commission, 2018). The EU’s progress in the field is monitored through the SET plan (European Commission, n.d.).

The Global CO₂ Initiative published in 2016 A Roadmap for the Global Implementation of Carbon Utilization Technologies (CO₂ Sciences, The Global CO₂ Initiative, 2016). The report estimates a potential market size of ~$200 billion and emissions reduction of ~0.5 billion tons by 2025. The emissions reductions are associated with the Carbon-Based Products Industry, which is essentially non-geologic carbon utilization (CO₂ Sciences, The Global CO₂ Initiative, 2016).

In the subsequent sub-sections, we discuss the use of CO₂ in fuels, chemicals, mineralization, EOR, ECBM, bio-products, and horticulture.

4.1 Fuel

CO₂ can be used to produce a variety of fuels, such as methane, methanol, dimethyl ether (DME) [International Energy Agency (IEA), 2019a; Abanades et al., 2017], gasoline, diesel, and aviation fuels by the Fisher-Tropsch synthesis (FTS) [Figure 4; Zhang et al., 2020; International Energy Agency (IEA), 2019a]. The conversion of CO₂ into a sustainable fuel is an energy-intensive process that requires electrical and/or thermal energy and low-carbon energy carriers (e.g., hydrogen) [International Energy Agency (IEA), 2019a; Kamkeng et al., 2021]. Chemical storage (PtX), Power-to-gas (PtG), or Power-to-Fuel (PtF) systems can store excess electricity from RES systems by forming a carbon-derived fuel (e-fuel) which can later be utilized to produce electricity, heat, or for other applications [Mikulčić et al., 2019; International Energy Agency (IEA), 2019a]. Wind/solar RES systems, although intermittent, can be used to power water electrolysers to produce hydrogen and utilize CO₂ to produce a given fuel or chemical (Mikulčić et al., 2019). This approach has the advantage of easier handling and use than pure hydrogen because of the low storage density and high energy input, coupled with the high flammability of hydrogen, making this conversion to other fuels economically and environmentally attractive (Valera-Medina et al., 2018; Andersson and Grönkvist, 2019).

In the European Union, the Renewable Energy Directive (RED), amended in 2023, establishes binding targets requiring at least 1% of transport energy to come from advanced biofuels, biogas and renewable fuels of non-biological origin by 2025, rising to 5.5% by 2030 (Vella et al., 2026). Furthermore, the expansion of the EU Emissions Trading System (ETS) to the transport sectors mandates emission intensity reductions of at least 14.5% by 2030 or that the share of renewable energy in transport is at least 29% by 2030 (Vella et al., 2026).

One versatile chemical that can be synthesized from fuel generation, used as a fuel for heating in the chemical industry and for ammonia production, is methane (Alberici et al., 2017). Reacting CO₂ with hydrogen produces synthetic methane or synthetic natural gas (SNG) through either catalytic or biological methanation (Chauvy and De Weireld, 2020; Alberici et al., 2017). In catalytic methanation, CO₂ and hydrogen are reacted in a reactor in the presence of a catalyst to produce methane (Equation 1; Alberici et al., 2017; Mondal and Dalai, 2017). Catalytic methanation is a technologically mature process and is commonly used in commercial ammonia plants (Alberici et al., 2017; Mondal and Dalai, 2017):

CO 2 + 4 H 2 ⇌ CH 4 + 2 H 2 O ; Δ H 298 ° = − 165 kJ / mol (1)

Similarly, methanol synthesis from CO₂ and H₂ offers the benefit of the integration of renewable energy sources and the production of sustainable fuels. CO₂ can be directly hydrogenated to produce methanol, a fuel with a relatively high energy content of 726.3 kJ/mol (Osman et al., 2021). Its combustion features combined with the absence of C-C bonds and sulphur make it a very interesting alternative fuel (Osman et al., 2021; Ghiat and Al-Ansari, 2021). Methanol can also be used as a fuel additive, hydrogen carrier (i.e., energy storage), or solvent to produce other chemicals, such as DME, acetic acid, or methylamines (Osman et al., 2021; Ghiat and Al-Ansari, 2021).

Methanol is produced via an exothermic reaction by chemically combining CO₂ and hydrogen (Equation 2; Osman et al., 2021).

CO 2 + 3 H 2 ⇌ CH 3 OH + H 2 O ; Δ H 298 ° = − 49 kJ / mol (2)

The thermal energy demand for a commercial methanol production facility (i.e., 50,000 to 100,000 tons/year) is estimated to be 1.01 MWh/ton of methanol, and the electric energy demand is 9.89 MWh/ton of methanol based on an alkaline electrolyser system (Koytsoumpa et al., 2018). This production energy consumption can be lower and could achieve commercial production of e-fuels in areas with RES and CO₂ availability at a low cost [International Energy Agency (IEA), 2019a]. An example of a power-to-methanol (PtM) facility is the George Olah plant in Iceland (Hepburn et al., 2019), where ~5,600 tons of CO₂ are converted ~4,000 tons of methanol, annually, using green hydrogen [International Energy Agency (IEA), 2019a; Koytsoumpa et al., 2018]. This process can mitigate carbon emissions if the energy source is renewable or is a low-carbon energy system [International Energy Agency (IEA), 2019a; Intergovernmental Panel on Climate Change (IPCC), 2005]. Similarly, the HySCALE100 project in Germany under development (Heide, 2022) is expected to convert ~1 MtCO₂ from petrochemical and cement industries, to methanol by integrating wind-powered hydrogen production [International Energy Agency (IEA), 2024b; Heide, 2022]. Recently, Maersk ordered 24 container ships that will have dual-fuel engines that can run on methanol, biodiesel, and regular bunker fuel. This strategy is supported by a recent agreement between Maersk and Goldwind, a Chinese wind turbine manufacturer, for procuring 500,000 tons of green and bio-methanol annually (Collins, 2024).

CO₂ can also be indirectly transformed into long-chain hydrocarbons that can act as an energy storage medium or transportation fuel (i.e., gasoline, diesel, and aviation fuels) (Osman et al., 2021; Do et al., 2022). CO₂ is made chemically active by converting it into CO using a reverse water gas shift (RWGS) reaction (Equation 3; Bobeck et al., 2019; Kamkeng et al., 2021; Grim et al., 2020). After, CO reacts with hydrogen to produce liquid hydrocarbons in the presence of a catalyst using FTS (Equation 4; Bobeck et al., 2019):

CO 2 + H 2 ⇌ CO + H 2 O ; Δ H 298 ° = 41.2 kJ / mol (3)

n CO + 2 nH 2 ⇌ ( − CH 2 − ) n + nH 2 O ; Δ H 298 ° = − n ∗ 152 kJ / mol (4)

These two processes can be integrated in direct hydrogenation to the Fischer-Tropsch fuel reactor to produce long-chain hydrocarbons (Do et al., 2022). Hydrocarbons can then be further processed through hydrocracking and isomerization to achieve the desired product (Osman et al., 2021).

The deployment of CO₂-derived fuels increases grid flexibility by integrating intermittent renewable energy sources and provides potential for interseason energy storage (Alberici et al., 2017). It also reduces the emissions levels by 54-87% for methane production and 74-93% for methanol production compared to conventional fossil fuel production pathways [International Energy Agency (IEA), 2019a]. If renewable sources of synthetic methane production become economically viable, it has the potential to reduce dependency on imported natural gas and contribute to a more sustainable gas supply (Alberici et al., 2017). The absence of sulfur and other elements that produce toxic gases makes CO₂-derived fuels environmentally appealing, reducing the risk of poor air quality and meeting sustainable transport goals (Alberici et al., 2017; Koytsoumpa et al., 2018).

Apart from the thermochemical conversion, there is a complementary approach for forming e-fuels/e-chemicals via electrochemical, photo-catalytic, photoelectrocatalytic (PEC), piezoelectric, and plasma catalysis. While research focuses on new approaches to develop or integrate these pathways, significant scientific and engineering progress is required to overcome important barriers to the commercialization of these pathways due to economic costs (Bobeck et al., 2019).

4.2 Chemical

CO₂ can be transformed into a wide variety of chemicals, such as polymers, food, and urea. For instance, methanol can be further processed to produce olefins and aromatics [International Energy Agency (IEA), 2019a]. These chemicals may be used in the plastic or food industries. Methanol-to-aromatics is less technologically mature compared to Methanol-to-olefins (MTO) technology, which has achieved a commercial-scale production of 9 Mt./yr. in China [International Energy Agency (IEA), 2019a].

In the plastic industry, CO₂-derived polymers are produced by copolymerization of CO₂ and conventional fossil fuels [Figure 5; Zhu, 2019; International Energy Agency (IEA), 2019a]. This process is less energy-intensive compared to the production of olefins and paraffins and, from an environmental perspective, are also interesting because can consume 50% CO₂ by weight [International Energy Agency (IEA), 2019a]. Polycarbonates are the most mature CO₂-based polymers with the potential for CO₂ utilization of about 0.173 tons per ton of polycarbonate [International Energy Agency (IEA), 2019a]. They are currently manufactured (150 kt/yr) by the Chimei Asia facility in China [International Energy Agency (IEA), 2019a; Ruiz Martínez and Sánchez Hervás, 2022]. However, the potential commercialization market of CO₂-based polymers is still relatively small [International Energy Agency (IEA), 2019a; Intergovernmental Panel on Climate Change (IPCC), 2005]. The current global production capacity is over 850 kt/yr., mostly for polycarbonates and polyols used in the production of polyurethanes, with an average weighted CO₂-based carbon content of around 5% (Renewable Carbon News, 2021).

R&D of CO₂-based plastics started in the 1960s when CO₂ was copolymerized with epoxides to form polycarbonates (Alberici et al., 2017; Inoue et al., 1969). The technologies for producing polycarbonates, such as polypropylene carbonate (PPC) and polyethylene carbonate (PEC), have matured, allowing for copolymerization involving propylene oxide and ethylene oxide in the presence of suitable catalysts (Alberici et al., 2017; Inoue et al., 1969; Bazzanella, 2019).

The copolymerization process takes place at low pressures (5-10 bars) and room temperature [Equation 5; Figure 5; Alberici et al., 2017; International Energy Agency (IEA), 2019a]. This pathway has a similar energy requirement as fossil fuel-based feedstock but results in lower CO₂ emissions and lower use of toxic epoxides. CO₂-based polymerization is challenging due to the low reactivity of CO₂, and the dependence of suitable catalysts and co-reagents (Osman et al., 2021). However, some highly selective and non-toxic catalysts have been recently made commercially available (Osman et al., 2021):

n ( CH 3 CHCH 2 O ) + nCO 2 → n ( CH 3 CHCH 2 CO 3 ) (5)

The main consumption of CO₂ by the chemical industry is to manufacture urea. Urea is a nitrogen-rich compound (46%) that can be used as a feedstock for different industries but is mainly used as a neutral and synthetic fertilizer (Zhang et al., 2020; Osman et al., 2021). Urea is synthesized through the reaction between CO₂ from steam reforming of natural gas and ammonia from the Haber-Bosch process (Equations 6, 7; Habib et al., 2018; Hong, 2022). The global production of urea is approximately 180 Mt./yr., which requires 132 Mt./yr. of CO₂ (Koohestanian et al., 2018):

N 2 + 3 H 2 ⇌ 2 NH 3 ; Δ H 298 ° = − 46 kJ / mol (6)

CO 2 + 2 NH 3 ⇌ NH 2 CONH 2 + H 2 O ; Δ H 298 ° = − 133 kJ / mol (7)

Production heavily relies on fossil fuels, and any disruption in their supply, price, or changes in carbon tax policies impact the fertilizer industry (International Energy Agency (IEA), 2019b; Institute for Sustainable Process Technology, 2017). To alleviate this dependence, urea can be synthesized using biomass gasification, resulting in a 65% reduction in GHG emissions (Gilbert et al., 2014). Alternatively, the production powered by RES provides a conversion pathway for captured CO₂ (Driver et al., 2019; Barzagli et al., 2011). In this process, hydrogen and nitrogen are produced using RES, which are then reacted to create ammonia (Driver et al., 2019). The synthesized ammonia is subsequently reacted with CO₂ to produce ammonium carbamate, an intermediate product, and later urea is synthesized in the presence of catalysts (Barzagli et al., 2011). However, these technologies have low maturity and complex scale-up (Zhang et al., 2020).

Other minor applications can finally be mentioned. CO₂ is also used in the manufacturing of carbonated drinks, food preservation, deoxygenated water, and milk products (Puligundla et al., 2012; Alsarhan et al., 2021). CO₂ acts as an acidifying agent restricting the growth of bacteria and mold (Kaliyan et al., 2007). In food refrigeration, CO₂ is used in freeze drying (i.e., dehydration), liquid carbon dioxide, and dry ice (i.e., the solid form of CO₂) (Osman et al., 2021). Similarly, it can be used with nitrogen for antioxidative food packaging (Zhang et al., 2020).

4.3 Mineralization

CO₂ can be incorporated in the manufacturing of concrete-based materials via mineralization/carbonation, which is a thermodynamically stable reaction between CO₂ and minerals (e.g., alkaline solid wastes or natural ores, occurring calcium and magnesium compounds) [International Energy Agency (IEA), 2019a; Gerdemann et al., 2007]. CO₂ can also be used as raw material for filler of cement or to cure concrete by replacing water [International Energy Agency (IEA), 2019a; Intergovernmental Panel on Climate Change (IPCC), 2005].

The carbonation pathway is the addition of CO₂ to calcium oxide, magnesium oxide, or silicate to form stable carbonate minerals [Equation 8; International Energy Agency (IEA), 2019a; Intergovernmental Panel on Climate Change (IPCC), 2005]. These alkaline solids are either naturally occurring (e.g., serpentine, olivine, and wollastonite), or solid waste found in iron, steel, power, cement, mining, and paper industries [Figure 6; International Energy Agency (IEA), 2019a; Georgakopoulos et al., 2016; Rahmanihanzaki and Hemmati, 2022]. The heat release depends on the specific alkaline metal/mineral [Intergovernmental Panel on Climate Change (IPCC), 2005].

Carbonation occurs naturally due to favorable thermodynamic characteristics of the reaction, but the conversion kinetics are slow [Chauvy and De Weireld, 2020; Intergovernmental Panel on Climate Change (IPCC), 2005]. Thus, a synthetic pathway is employed. First, impurities, such as silicon and iron, are removed. Second, CO₂ is injected to produce a pure carbonate compound [Intergovernmental Panel on Climate Change (IPCC), 2005]. There are two pathways, direct and indirect, to convert CO₂ into carbonate products (Cuéllar-Franca and Azapagic, 2015; Zhang et al., 2020). The direct carbonation occurs in a single-step reactor between extracted mineral or alkaline slurry with CO₂, this can involve a pre-treatment step to increase the carbonation rate (Rahmanihanzaki and Hemmati, 2022; Sanna et al., 2014). Indirect carbonation takes place in three main steps (Zhang et al., 2020; Ghiat and Al-Ansari, 2021): (1) separation of metal from the mineral, (2) the formation of metal hydroxides via hydration, and (3) reaction between CO₂ and metal hydroxides to produce carbonates (Cuéllar-Franca and Azapagic, 2015; Ghiat and Al-Ansari, 2021).

MO + CO 2 → MCO 3 + heat (8)

Carbonation pathway not only produces useful carbonates but also permanently stores CO₂ (Chauvy and De Weireld, 2020; International Energy Agency (IEA), 2019a). It can potentially store around 3.3 Gt CO₂/yr., which will be around 5-12% of the total predicted GHG emission (Ghiat and Al-Ansari, 2021; Di Maria et al., 2020). One ton of CO₂ can be stored from 1.6-3.7 tons of rock and a ton of coal fly ash, cement kiln dust, or blast furnace slag can store 0.07-0.25, 0.08-0.25 and 0.26-0.38 tons of CO₂, respectively (International Energy Agency (IEA), 2019a; Ghiat and Al-Ansari, 2021). In the case of industrial waste, this pathway can avoid environmental hazards as normally waste deposits are stockpiled or landfilled (Alberici et al., 2017), generating dust and disperse or contaminate groundwater (Alberici et al., 2017). Another advantage is that CO₂ with a purity degree between 50-60% can be used (Alberici et al., 2017; Huijgen, 2007). In fact, CO₂ captured from flue gases can be used directly for carbonation, as impurities from oxides of nitrogen and sulfur do not have an impact on the carbonation reaction (Cuéllar-Franca and Azapagic, 2015; Alberici et al., 2017), thereby reducing energy consumption on the purification of CO₂ (Alberici et al., 2017; International Energy Agency (IEA), 2019a).

The carbon removal efficiency depends on the type of material, pre-treatment process, carbonation pathway, and operating conditions (International Energy Agency (IEA), 2019a; Zhang et al., 2024). For mineral ores, efficiency ranges from 10-60%. This percentage can be increased to 40-90% with pre-treatment (Alberici et al., 2017). Natural ores are less efficient than industrial waste streams. For example, serpentine reacts slowly with CO₂ during carbonation, which requires increasing the surface area of the rock by grinding it to small particle size, reacting in salt solutions, and having pressures around 10 MPa (Zhang et al., 2020).

Similarly, untreated artificial materials can remove CO₂ by more than 70% (Alberici et al., 2017). Pei et al. (2017) observed a 96% CO₂ removal efficiency by using fly ash from the petrochemical industry. However, synthetic materials are less abundant, and most waste materials need pre-treatment or high temperature and pressure, followed by a separation process after carbonation (Alberici et al., 2017; International Energy Agency (IEA), 2019a). These steps increase the cost of carbonation and energy supply (International Energy Agency (IEA), 2019a). Thus, R&D is required to increase the rate of carbonation at low temperatures and pressures, recover and reuse the energy from exothermic carbonation, and scale up the processes at an industrial level (Alberici et al., 2017; International Energy Agency Greenhouse Gas (IEAGHG), 2013).

There are different industrial projects around the globe in this domain. Carbon8 systems (United Kingdom) produce around 60,000 t/yr. lightweight aggregates using waste material (Zhu, 2019; International Energy Agency (IEA), 2019a). The process uses around 5,000 t/yr. of CO₂ and is considered carbon-negative as no heat and electricity are required to move the materials through the industry (Zhu, 2019; International Energy Agency (IEA), 2019a). Researchers from the University of California, Los Angeles (USA), developed a near-carbon-neutral novel binder based on calcium hydroxide, known as CO2NCRETE (Do et al., 2022), that forms a construction material by reacting with CO₂ via a carbonation reaction (Zhu, 2019).

An alternative mineralization pathway is an electrochemical process using NaOH to absorb CO₂ and produce NaHCO₃/sodium bicarbonate (a marketable product) (Zhang et al., 2020; Xie et al., 2014). CarbonFree Chemicals (USA) developed and patented the SkyMine process based on the electrochemical pathway (Alberici et al., 2017; Zhu, 2019). The SkyMine process can be used to remove CO₂, NO_X, SO_X, and even heavy metals (Alberici et al., 2017; Zhu, 2019). The electrochemical route uses salt and water to form low-concentration NaOH solution, hydrogen, and chlorine (Alberici et al., 2017; Zhu, 2019). CarbonFree Chemicals estimated an 83,000 t/yr. decrease of CO₂ from the plant (Alberici et al., 2017; Zhu, 2019). Similarly, Carbon Cycle, a UK-based company, plans to use natural or industrial gypsum with ammonia to produce calcium carbonate and ammonium sulphate (Alberici et al., 2017).

Considering alternative approaches, concrete curing is one of the most viable. Concrete curing is a process that involves water, cement, and aggregate mixing to produce calcium hydroxide giving strength to concrete (Alberici et al., 2017; International Energy Agency (IEA), 2019a). Concrete can also be cured by injecting CO₂, as this process occurs very slowly (few mm/yr) in nature between CO₂ in the air and regular cement (Alberici et al., 2017; International Energy Agency (IEA), 2019a). The rate at which this process occurs can be increased for example in pre-cast concrete by having curing chambers with high concentrations of CO₂ (Alberici et al., 2017; Zhu, 2019). Injected CO₂ leads to the production of calcium carbonate during the carbonation process as shown in Figure 7 (Equations 9, 10; Alberici et al., 2017; International Energy Agency (IEA), 2019a):

CaO + CO 2 → CaCO 3 ; Δ H 298 ° = − 178 kJ / mol (9)

Ca ( OH ) 2 + CO 2 → CaCO 3 + H 2 O ; Δ H 298 ° = − 113 kJ / mol (10)

Benefits of carbon-cured concrete include increased strength, faster curing time, reduced cement requirement manufacturing costs and CO₂ emissions (around 80%), and permanent storage of CO₂ (Zhu, 2019; International Energy Agency (IEA), 2019a; Bobeck et al., 2019). Concrete curing is technologically more mature than carbon cement application (International Energy Agency (IEA), 2019a). CarbonCure Technology, a Canadian company, is leading the development and usage of this technology with 150 operating facilities (International Energy Agency (IEA), 2019a), with a CO₂ absorption efficiency of around 50-80%, and a capacity of around 3.5 kg of CO₂ per cubic meter of concrete (Zhu, 2019). Solidia Technology, an American-based company, is commercializing its technology using CO₂-curing chambers to produce Solidia Concrete (Zhu, 2019). This reduces carbon emission by 70% (i.e., 300 kg of CO₂) is absorbed by each ton of Solidia Cement (Zhu, 2019).

4.4 Enhanced oil recovery

EOR is a tertiary oil production method to improve oil production (Hong, 2022; Lake et al., 2014). Primary oil extraction allows recovery of 5-40%; water flooding during the secondary extraction allows 10-20% of recovery; and finally, tertiary extraction via EOR allows 7-23% (average of 13.2%) of recovery (Intergovernmental Panel on Climate Change (IPCC), 2005; Hong, 2022). EOR includes chemicals, thermal, and gas injection methods, with CO₂ being mainly applied to EOR since the 1970s (Zhang et al., 2020). CO₂-EOR is a mature technology, as shown in Figure 8, with the potential to be deployed in over 90% of global oil reserves, potentially recovering 190-430 billion barrels of oil, while storing 61-123 Gt of CO₂ (Zhang et al., 2020; Vishal and Singh, 2016).

EOR makes the CO₂ utilization pathway economically and environmentally favorable by storing part of the injected CO₂ stream permanently and increasing the production of oil. For example, an increase in at least 250,000 barrels of oil per day using the CO₂-EOR pathway was reported in the USA (Leung et al., 2014). Thus, one of the main markets for CO₂ utilization is EOR (Zhang et al., 2020; Ghiat and Al-Ansari, 2021). Moreover, CO₂-EOR technology can reach neutral (or negative) GHG emissions during oil extraction, processing, transportation, and utilization (Ghiat and Al-Ansari, 2021; Stewart et al., 2018).

The key factors should be considered before the deployment of CO₂-EOR in a given reservoir (Aminu et al., 2017):

• Detailed characterization of the reservoir formation;
• Detailed integrity studies about the cap rock;
• Emissions from surface processing facilities should be monitored;
• Risk assessment and monitoring for any leakage;
• Maintenance/retrofitting of abandoned wells.

Table 2 summarizes the most well-known CO₂-EOR projects, including one of the largest situated in Weyburn oilfield, Canada. The CO₂ is supplied from a pipeline (approximately 320 km) from a gasification plant in North Dakota, USA (Leung et al., 2014). CO₂-EOR has extended the life of oilfields by 20-35 years (Aminu et al., 2017). However, social and public concerns pose a barrier to the widespread implementation of CO₂-EOR because of potential environmental issues and the long-term safety of injected CO₂ (Zhang et al., 2020; Meylan et al., 2015). Moreover, it should be noted that less than 30% of the CO₂ comes from non-geological sources for CO₂-EOR because there are not any anthropogenic CO₂ sources close to oilfields (International Energy Agency (IEA), 2020b). This is among the key barriers to the wider adoption of CO₂-EOR among other barriers mentioned in section 7.

Table 2. CO₂-EOR projects around the globe (Ghiat and Al-Ansari, 2021; Leung et al., 2014).

A similar pathway to EOR is injecting CO₂ to improve gas recovery and store CO₂ (Sun et al., 2020). Enhanced Shale Gas Recovery (ESGR) can increase the production of gas by 26% after primary extraction and store around 60% of injected CO₂ (Iddphonce et al., 2020). The nanopores in shaly formations have a stronger affinity for CO₂ than the in-situ methane, so the injection of CO₂ replaces methane (Sun et al., 2020; Sheng, 2015). Reservoir gas pressure, CO₂ injection pressure, injection time, production time, and physical properties of the reservoir can have an impact on ESGR, and the technology is still in the experimental stage (Zhang et al., 2020). More R&D needs to be conducted to commercialize ESGR, including the impacts of moisture, the kinetics and flow dynamics of gases, and the impact of CO₂ injection on shale (Zhang et al., 2020; Iddphonce et al., 2020).

4.5 Coalbed methane recovery

CO₂ can also be stored in deep coal seams (Figure 9; Su et al., 2019; Cao et al., 2020). In ECBM, CO₂ is injected into deep, un-mineable coal beds to recover methane (Zhang et al., 2020; Aminu et al., 2017). The presence of micropores and cleats allows the adsorption of gases (Intergovernmental Panel on Climate Change (IPCC), 2005; Aminu et al., 2017). Coal has a higher affinity for CO₂ compared to methane, so injected CO₂ replaces methane in the coal beds (Intergovernmental Panel on Climate Change (IPCC), 2005; Aminu et al., 2017). Low-grade coal has more affinity for CO₂ than high-grade coal as per the adsorptive volumetric ratio of CO₂ to CH₄ is 10 for coals such as lignite and 1 for coals such as anthracite (Intergovernmental Panel on Climate Change (IPCC), 2005).

ECBM pathway provides the potential to store large amounts of CO₂ and increase methane production by 90% when compared to 50% extraction by conventional approaches (Yusuf and Ibrahim, 2023; Ghiat and Al-Ansari, 2021). The global potential is estimated to increase methane production by 50 × 10¹² m³ and store around 488 Gt of CO₂ (Godec et al., 2014). Injected CO₂ leads to the softening of the coal to a rubber/plastic-like structure and coal swells, reducing the efficiency of coalbed methane (CBM) recovery (Intergovernmental Panel on Climate Change (IPCC), 2005; Su et al., 2019). Several research studies and pilot-scale plants have been carried out in the domain of ECBM. During the field tests, CO₂ injection capacity was lower than that predetermined due to the permeability reduction of coal (Su et al., 2019). For example, CO₂ injection was reduced by 40 and 70% in initial operations at Allison Unit (USA) and Ishikari Basin (Japan) (Reeves, 2003; Fujioka et al., 2010).

The permeability reduction along with safety and environmental issues, and the decision to mine or store CO₂ in a coal mine, are key barriers to the development of this technology (Leung et al., 2014; Cao et al., 2020). Currently, CBM is carried out by decreasing the pressure by removing water, which allows methane desorption from the coal seams (Zhang et al., 2020). R&D efforts are required to understand the adsorptive characteristics of CO₂ in coalbeds before commercializing and making the pathway economically beneficial (Zhang et al., 2020; Su et al., 2019).

4.6 Bioproducts

The biological fixation of CO₂ via algae is a relatively novel pathway to produce carbohydrate/petroleum products (Osman et al., 2021; International Energy Agency (IEA), 2019a). Algae use photosynthesis to convert CO₂ into organic carbons (Zhang et al., 2020; Lam et al., 2012) and can grow in open or closed systems (Bobeck et al., 2019; Bhatia et al., 2019). Open systems include ponds and lagoons, while closed systems involve photobioreactors (Bobeck et al., 2019; Bhatia et al., 2019). Algae have the benefit of not requiring a high-purity CO₂ gas stream, and only 10-20% CO₂ concentration is considered sufficient for algae growth (Meylan et al., 2015; Miyachi et al., 2003). Moreover, algae have the following advantages:

• Flue gas can be directly fed into the conversion process, and some combustion products such as NO_X or SO_X can be used as nutrients for algae growth (Bobeck et al., 2019; Lam et al., 2012);
• The higher photosynthetic rate allows higher CO₂ fixation (almost 50%) rate than terrestrial crops (Ghiat and Al-Ansari, 2021);
• Algae can be grown in fresh, sea, or wastewater (Bobeck et al., 2019; Ghiat and Al-Ansari, 2021);
• This pathway produces high-value, bio-degradable, and carbon-neutral marketable products (Bobeck et al., 2019; Ghiat and Al-Ansari, 2021);
• 1.83 kg of CO₂ is absorbed and converted by 1 kg of algal biomass (Chisti, 2007).

One of the target markets of algae products can be non-toxic, carbon-neutral fuels. Fuels can be produced by algal biomass conversion techniques, through fermentation of carbohydrates or extraction of lipids, followed by transesterification production of biodiesel (Lam et al., 2012; Seyed Hosseini et al., 2018; Chai et al., 2022).

Recent research has pivoted toward synthetic biology and fourth-generation microalgal technology, specifically targeting genetic expression and catalytic activity to significantly enhance CO₂ fixation rates (Sun et al., 2026; Pérez-de la Cruz et al., 2024). By changing the metabolic pathways of cyanobacteria and microalgae, researchers are creating specialized cells (Singh et al., 2024). For instance, cyanobacteria fix CO₂ using Rubisco, followed by the synthesis of organic carbon compounds in the presence of light using the Calvin-Benson cycle (Zhang et al., 2020; Bobeck et al., 2019). These bacteria later excrete fuel or fuel precursors (Bobeck et al., 2019). This pathway has the potential to produce more ethanol (5 L/m²) than corn (0.3 L/m²) and sugarcane (0.6 L/m²) (Ghiat and Al-Ansari, 2021). The lifecycle assessment of algae-based fuels by the Environment Protection Agency (EPA) shows that GHG emissions will be reduced by 69-85% for petroleum fuels and at least 50% for diesel (Bobeck et al., 2019).

However, algal-based pathways are at an early stage of development (International Energy Agency (IEA), 2019a). Several pilot-scale plants use algae in a closed system and CO₂ from power plants or other industries. An example of a pilot plant is the usage of microalgae at a gas facility in Hazara, India. The system is under anaerobic conditions to capture CO₂ from vent gas and was observed to reduce CO₂ concentration from 34% by volume to 15% by volume (Yadav et al., 2016). Another example of a pilot plant is in Novara, Italy, where CO₂ was absorbed by algae with the help of photobioreactors. At an industrial scale, this system could use 1,000 t/y of CO₂ to produce 500 tons of biomass (Ente Nazionale Idrocarbur (ENI), n.d.). However, low production rates were observed for most of the pilot projects. The impact of physiochemical parameters and impurities in algae culture, high energy requirement, capital costs and large-scale open-pond systems, require expansive footprints in regions with high solar radiation, are the main barriers to the scaling up of this technology (Zhang et al., 2020; International Energy Agency (IEA), 2019a; Li and Yao, 2024). Moreover, the fixation rate of 1.83 kg of CO₂ by 1 kg of algal biomass vary significantly with the species, light intensity, and nutrient availability (Pérez-de la Cruz et al., 2024).

The conversion and utilization of CO₂ can be increased via enzymes, like carbonic anhydrase and carboxylases (Bierbaumer et al., 2023; Turakulov et al., 2024). Enzymes can reduce the energy requirement of the system by operating at low temperatures and pressure. However, enzymes are highly specific for target reactions with precise molecules which can raise problems to widespread technology (Turakulov et al., 2024; Villa et al., 2023). Additionally, variations in physiochemical parameters can have a significant impact on the conversion rate. This poses a barrier for systems using bio-catalysis via enzymes, especially with high operating costs and scale-up problems (Turakulov et al., 2024). Continued R&D in this field can help to enhance the yield rates and conversion efficiency and reduce the costs of bioreactors (International Energy Agency (IEA), 2019a).

4.7 Horticulture

CO₂ applications in greenhouses can greatly increase agricultural productivity (International Energy Agency (IEA), 2019a; Hong, 2022). The optimal concentration depends on crop type and greenhouse operating conditions, with a range between 600–1200 ppm to improve productivity by 25-30% (Alberici et al., 2017; Becker and Kläring, 2016). An additional benefit can be a 40% reduction in water consumption (Sánchez-Guerrero et al., 2009).

A study conducted by Marchi et al. (2018) estimated a revenues increase by 0.68 - 1.6 million €/year when CO₂ is used in horticulture. The study considered three scenarios (without CO₂ enrichment, CO₂ enrichment by using heaters and CO₂ supplied from industrial processes), and assumed two production cycles for tomatoes, cucumbers, and strawberries. Another study by Climeworks in Hinwil, Switzerland, has demonstrated the CO₂ application to enhance crops (Climeworks, n.d.; Nagireddi et al., 2024) emploing DAC to capture 900 t/y of CO₂ with energy supplied from a nearby waste incineration plant (Nagireddi et al., 2024). The project was, however, focused on the feasibility of DAC rather than the study the CO₂ application.

For this type of application, CO₂ needs to be pure, as impurities can damage crops (Alberici et al., 2017; Ghiat and Al-Ansari, 2021). This is the reason why direct flue gases from biomass, coal, or oil combustion are not considered suitable, and the CO₂ stream needs to be cleaned, increasing energy usage and costs (Alberici et al., 2017). The CO₂ stream from the combustion of natural gas, production of ammonia, conversion of biogas to biomethane, fermentation, and production of ethanol are considered suitable for horticulture (Alberici et al., 2017). Current practice includes the procurement of pure liquid CO₂ or operating a natural gas combined heat and power (CHP) or a natural gas boiler in the proximity of the farmland (Alberici et al., 2017; International Energy Agency (IEA), 2019a). The CHP plant or boiler is run only during the daytime so plants can take up CO₂ (Alberici et al., 2017). The electricity produced from CHP is either consumed locally or supplied to the grid, while heat is stored in thermal tanks using water to be released at night-time to maintain the temperature of the horticulture system (Alberici et al., 2017; International Energy Agency (IEA), 2019a). The installed capacity of CHP is around 0.75-1 MW_el/ha (Alberici et al., 2017). The replacement of these on-site systems will result in the reduction of GHG emissions (International Energy Agency (IEA), 2019a). Presently, in the Netherlands, external CO₂ is used with a demand of 500kt/year of CO₂ (International Energy Agency (IEA), 2019a; Ghiat and Al-Ansari, 2021). CO₂ is supplied to around 600 greenhouses spreading over an area of 1900 hectares resulting in an annual saving of 140 million m³ of natural gas (International Energy Agency (IEA), 2019a). This saving in natural gas consumption amounts to around 250kt CO₂ of emission avoided annually (International Energy Agency (IEA), 2019a; Organic CO₂ for Assimilation by Plants, 2019).

Still, CO₂ enrichment in greenhouses is not widely used and hence the demand for CO₂ in this sector and its impact on emission reduction are unknown (International Energy Agency (IEA), 2019a). The challenge of providing pure CO₂ at a low cost and the lack of CO₂ infrastructures reduce the interest in this sector, as industrial stakeholders found that emitting CO₂ is cheaper than using this pathway (Alberici et al., 2017; International Energy Agency (IEA), 2019a).

5 Purity requirement

CO₂ needs to be purified for most of the utilization pathways mentioned above. The purity level and presence of certain types of impurity depend on the (Yousaf et al., 2022) carbon utilization pathway (Table 3). CO₂ emissions from power-generating industries include water, H₂S, SO_X, NO_X, CO, O₂, hydrocarbons, N₂, ammonia/amines, and trace elements/compounds (e.g., mercury and cyanides) (Mikulčić et al., 2019). The presence of water along with H₂S, SO_X, NO_X, and CO₂ can form acids that can corrode the equipment (e.g., pipelines) and form precipitates impacting mass flow (Murugan et al., 2020). Moreover, NO_X, SO_X, CO, hydrocarbons, H₂S, ammonia/amines, mercury, and cyanides are toxic, and their release can adversely impact the environment (Murugan et al., 2020). Similarly, oxygen increases microbial activity, which can block the pipelines and the reaction of O₂ with hydrocarbons (in oil fields) may lead to combustion (Murugan et al., 2020). These impurities also increase the compression power required to push CO₂ through the process pathway. Moreover, in the case of the geological utilization pathway (EOR), non-condensable impurities reduce the storage capacity of CO₂ by increasing the buoyancy effect of the gas mixture because of the low density of the overall gas mixture (Murugan et al., 2019). Only 15% impurity of non-condensable gases in the mixture can increase the buoyant forces by 50% and decrease CO₂ storage capacity by 40% (Murugan et al., 2019). Moreover, the presence of H₂S and SO_X blocks the pore in the geological sites by depositing sulfur impacting underground CO₂ storage (Murugan et al., 2019). Similarly, in the case of non-geological utilization pathways involving catalysts, the impurities can irreversibly block the active sites of catalysts, thereby slowing down the reaction(s) in the conversion pathway and leading to the loss of expensive catalysts (Nieß et al., 2022). A summary of the purity requirements for each utilization pathway is presented in Table 3.

Table 3. Carbon dioxide quality requirements for carbon utilization pathway.

6 Life cycle analysis

The LCA studies cover various CCU technologies, some of which include mineral carbonation, chemical production, EOR, biodiesel production from microalgae, PtG methodology, and the integration of CCU in municipal solid waste incineration (MSWI).

One extensively researched CCU technology is mineral carbonation, which has the potential to reduce emissions by 4 to 48% when compared to non-CCU scenarios (Cuéllar-Franca and Azapagic, 2015). A global warming potential (GWP) of 524–1,073 kg CO₂ equivalent per ton of CO₂ removed, for example, was reported by Khoo and Tan (2006), Khoo et al. (2011), and Nduagu et al. (2012). Mineralization removes 0.26-0.36 tCO₂-eq/tCO₂ removed; this range/variance is dependent on the capture methods, energy recovery, and allocation techniques (Cuéllar-Franca and Azapagic, 2015).

Pulverized coal (PC) power plants report a GWP of 0.75 t CO₂-eq per ton of CO₂ removed, while integrated gasification combined cycle (IGCC) plants with EOR report 0.53 t CO₂-eq and combined-cycle gas turbine (CCGT) plants exhibit a GWP of 0.83 tCO₂-eq (Cuéllar-Franca and Azapagic, 2015).

Chemical and fuel production from CO₂, such as dimethyl carbonate (DMC) and formic acid, also appears promising. Traditional DMC synthesis, which uses ammonia and naphtha, has a higher GWP, whereas urea-based synthesis reduces GWP by a factor of 4.3 (31 vs. 132 kg CO₂ eq./kg DMC) (Cuéllar-Franca and Azapagic, 2015; Aresta and Galatola, 1999). Similarly, Formic acid production via hydrogenation has a significantly lower GWP of 4.52 kg CO₂-eq per kg of captured CO₂ than other methods, which frequently require more energy (Thonemann and Pizzol, 2019). CO₂-derived methanol and propene reduce emissions, with a net GWP of -0.325 t CO₂-eq per ton produced and 1.89 t CO₂-eq per t of propene, respectively (Nie et al., 2023; Garcia-Garcia et al., 2021). This environmental benefit on fuels and chemicals was further confirmed by Artz et al. (2018) and Hoppe et al. (2018). The latter demonstrated significant GHG reduction potentials for both methane and methanol while emphasizing that the net impact depends heavily on utilizing low-carbon hydrogen from renewable energy sources. Rosental et al. (2020) expanded on this analysis by reporting that the GWP of producing large volumes of organic chemicals through CCU is approximately 50-540 kg CO₂-eq per ton of product. This represents an 88-97% reduction compared to the GWP of fossil fuel-based synthesis, which is around 2002-4648 kg CO₂-eq per ton. Sadok et al. (2020) demonstrated that utilizing high-temperature co-electrolysis (co-SOEC) to process industrial flue gas offers significant climate benefits when supported by low-carbon energy. Specifically, when integrated into a coal-fired cement plant in France, the framework achieves annual CO₂ savings of up to 2.39×10⁵ tons CO₂-eq (utilizing a portion of solar PV), while integration into a biomass gasification plant reduces emissions by 2.40 × 10⁴ tons CO₂-eq.

Moreover, the operational integration of PtG and PtX technologies presents a viable avenue for long-term energy storage and CO₂ mitigation (Ince et al., 2021; Koj et al., 2019; Sillman et al., 2024). Fózer et al. (2020) investigated the GWP by using the bio-synthetic PtG approach combines bioenergy and CCUS to store energy as methane. PtG reduces emissions by 11.9 times compared with brown coal and 4.9 times compared with natural gas, with a GWP of less than 100 g CO₂-eq/kWh and a round-trip efficiency of 42.3%. The carbon conversion ratio of 71.23% highlights its potential for long-term energy storage and CO₂ mitigation. Supporting this potential, Sillman et al. (2024) demonstrated that the direct use of hydrogen to produce steel, biogas upgrading, protein, or ammonia resulted in over 10 kg CO₂/kg H₂ reductions on average when using low-carbon energy sources. However, Koj et al. (2019) reviewed 32 LCA studies on Power-to-X systems and concluded that the electricity source and framework for CO₂ accounting are the most critical factors influencing environmental performance. The authors emphasized that integrating renewable electricity is essential to achieve substantial GHG reductions and highlighted the lack of transparency and standardization in current PtX life cycle methodologies.

The manufacturing of polymers also benefits from emission reduction potential (Hoppe et al., 2018). Polymers derived from CO₂, such as polyethylene and polypropylene, show a GWP ranging from approximately 0.006 to 6 kg CO₂-eq, significantly lower than fossil-fuel-based polymers (~0.02-9 kg CO₂-eq) (Kaiser et al., 2022). High-density polyethylene demonstrates a 73% emissions reduction, while polyvinyl chloride achieves a 61% reduction (Kaiser et al., 2022).

CCU via CO₂-EOR removes 0.59-0.66 tCO₂eq./tCO₂ removed and has mixed results in terms of reducing emissions (Cuéllar-Franca and Azapagic, 2015). On average, EOR reduces GWP by 2.3 times that of CO₂ emissions (Hertwich et al., 2008). Similarly, Jaramillo et al. (2009) show that EOR can produce net-negative emissions under favorable conditions. The study covers different fields and estimates net EOR emissions of 7 to 220 Mt. CO₂-eq. (Jaramillo et al., 2009). However, the environmental impact of CO₂ capture options and EOR practices varies significantly.

Microalgae-based biodiesel production provides a renewable pathway for CO₂ utilization, with GWP ranging from 19 to 534 g CO₂-eq per megajoule (MJ) of biodiesel (Cuéllar-Franca and Azapagic, 2015). Cultivation methods have a significant impact on GWP. For example, GWP with open raceway ponds achieved 50-70 g CO₂-eq/MJ, while for the air-lift tubular bioreactor, it was reported to be 366 g CO₂-eq/MJ (Cuéllar-Franca and Azapagic, 2015; Stephenson et al., 2010). Only two studies suggest that microalgae biodiesel is more sustainable than fossil diesel, which has a GWP of 85 g CO₂-eq/MJ (Cuéllar-Franca and Azapagic, 2015). Stephenson et al. (2010) report the lowest GWP (with 19 g) from anaerobic digestion of waste to generate electricity, whereas Brentner et al. (2011) report 80.5 g CO₂ eq./MJ from landfilling waste biomass. Furthermore, MEA-captured CO₂ increases GWP by 30-60%, whereas direct injection of flue gases results in lower GWP values, such as 160 g CO₂-eq versus 230 g CO₂-eq with MEA capture (Borkowski et al., 2012; Zaimes and Khanna, 2013).

Additionally, CCU can be integrated into MSWI plants, enabling significant CO₂ capture, with up to 823 kg of CO₂ captured per ton of municipal solid waste (Christensen and Bisinella, 2021). However, environmental benefits are dependent on energy system configurations and utilization pathways. For example, one scenario exhibits a net load of 221 kg CO₂-eq/ton of MSW, while another scenario achieves a much lower net load of 65 kg CO₂-eq/ton (Christensen and Bisinella, 2021).

Improving the environmental performance of CCU technologies requires the incorporation of renewable energy. For instance, compared to traditional methods, using renewable energy in the production of formic acid can reduce emissions by as much as 50% (Aldaco et al., 2019). Maximizing CCU’s climate benefits requires the transition from fossil fuel-based energy to renewable sources.

Current LCA studies, while useful, often fail to fully account for indirect emissions, resulting in potentially inaccurate environmental impact assessments (Gowd et al., 2023). The lack of standardized guidelines for LCA in CCU technologies contributes to the inconsistency (Gowd et al., 2023; Wang et al., 2024). For example, many technologies are still in the early stages of development, resulting in high uncertainties in environmental assessments (Wang et al., 2024; Zimmermann et al., 2022). Developing uniform LCA frameworks can help to ensure consistent and fair comparisons of CCU options. Furthermore, GWP is the most commonly used metric in the LCA studies (Cuéllar-Franca and Azapagic, 2015; Khoo and Tan, 2006; Khoo et al., 2011; Nduagu et al., 2012; Aresta and Galatola, 1999; Thonemann and Pizzol, 2019; Nie et al., 2023; Rosental et al., 2020; Fózer et al., 2020; Kaiser et al., 2022; Hertwich et al., 2008; Jaramillo et al., 2009; Stephenson et al., 2010; Brentner et al., 2011; Borkowski et al., 2012; Zaimes and Khanna, 2013; Christensen and Bisinella, 2021; Gowd et al., 2023). A more comprehensive LCA should consider acidification potential (AP), eutrophication potential (EP), and photochemical ozone creation potential (POCP) (Christensen and Bisinella, 2021). This comprehensive approach would clarify trade-offs and provide a more accurate assessment of CCU technologies’ environmental footprints (Garcia-Garcia et al., 2021; Christensen and Bisinella, 2021).

However, reported GWP values across these studies should not be interpreted as directly comparable without considering their underlying methodological assumptions. Insufficient emphasis is often placed on methodological uncertainties arising from system boundary definitions (e.g., cradle-to-gate or cradle-to-grave), co-product allocation rules (e.g., mass, energy, or economic allocation), and the assumed background energy mix. Furthermore, the net climate benefits of almost all CCU pathways strongly rely on renewable energy input; utilizing fossil-dominated grid electricity can easily negate potential GHG reductions.

7 Barriers and Hinderance in CCU

There are significant barriers that are delaying the deployment of carbon utilization technologies. We highlight briefly the most significant ones in the next paragraphs.

Apart from direct and conversion pathways of CO₂ utilization, they can be further bifurcated into geological CCU and material-based CCU. These two categories face fundamentally different bottlenecks. Geological CCU is highly mature but heavily scrutinized for its long-term site safety, CO₂ injectivity, and net climate impacts. Conversely, material-based CCU is primarily constrained by technological immaturity, high energy requirements for conversion, and economic competitiveness against conventional products. However, the supply chain of CO₂ is common between these pathways.

7.1 Technological maturity

Many technological pathways involved in CCU are in TRL stages as shown in Table 4. Despite advances, most CCU technologies have not been tested at commercial scales. For example, while certain carbon capture technologies have been implemented at pilot scales, their widespread deployment is hindered by lengthy implementation timelines and high costs (United States Government Accountability Office, 2022). This situation presents a significant commercial risk, making investments less attractive. The investors are reluctant to fund technologies that have not been proven on a large scale, and without funding, these technologies cannot reach the necessary scale for testing.

Table 4. Summary of emission reduction impact of selected CCU pathways using LCA.

7.2 High costs for CO₂ transport

Transporting CO₂ remains among the biggest financial hurdles in CCU deployment (Gonzales et al., 2020). New pipelines are to be laid as existing pipelines of oil and gas are not suitable for CO₂ transport (Gonzales et al., 2020). The transportation system must deliver pure and pressurized CO₂, which further increases the infrastructure costs (Gonzales et al., 2020). Moreover, these factors coupled with regions where CO₂ sources are distant from utilization sites can reduce the feasibility of a CCU project (Gonzales et al., 2020; Sillman et al., 2023).

7.3 Lack of clarity around CO₂ utilization

There is a lack of clarity regarding the prioritization of CO₂ utilization among different carbon sinks (Mikulčić et al., 2019; Kamkeng et al., 2021). Determining whether the focus should be on proximity to carbon sources or specific carbon utilization pathways remains uncertain, creating challenges in decision-making and resource allocation (Mikulčić et al., 2019). A unified prioritization strategy and framework would enable industries and governments to place resources where they are most effective and economically feasible.

7.4 Safety

The risk of CO₂ leakage, and storage safety for the long term is still a concern for EOR and ECBM (Salvi and Jindal, 2019). However, proper risk methods and reservoir management are in place to inject CO₂ into the subsurface in a safe manner (EOR).

From PtX perspective, hydrogen is a very small molecule that has high diffusivity and buoyancy coupled with a wide flammability range, low ignition energy, and material embrittlement, which results in storage issues that lead to very high costs for safe storage (Carluccio et al., 2025; Mekonnin et al., 2025; Li Q. et al., 2024; Calabrese et al., 2024).

7.5 Insufficient policies and lack of incentives

The lack of policies to give incentives and promote CCU technologies adds another barrier to the scaling-up of CCU technologies (Song, 2006). For example, low-carbon aggregates are economically not feasible, selling for $70-100/ton while current aggregate costs are around $50/ton (Sandalow et al., 2017). This can be attributed to the absence of supportive policies such as subsidies, carbon pricing, and incentives for green products to compete in the market. Furthermore, there are significant regulatory-related barriers to the implementation of PtX technologies and uncertainties regarding additionality rules, as highlighted by Sillman et al. (2023) in a Delphi survey.

7.6 Shortcomings of LCA studies

Without comprehensive and verified LCA methodologies for CCU products, the environmental impact of these technologies remains uncertain. The absence of methodologies makes it difficult to quantify the net reduction in CO₂ emissions and evaluate the effectiveness of CCU solutions (Chauvy and De Weireld, 2020; CO₂ Sciences, The Global CO₂ Initiative, 2016). A comprehensive assessment of the overall environmental footprint beyond CO₂ reduction is often lacking for most of the technologies.

An example is that of CO₂-EOR, where CO₂, sequestered in the geological reservoir, facilitates the extraction of additional fossil fuels. The subsequent combustion of this produced oil releases substantial greenhouse gases, which can severely diminish or entirely negate the net climate benefits of the initial CO₂ storage. The additional oil produced is subsequently transported, refined, and combusted, generating downstream CO₂ emissions. Therefore, the climate benefit of CO₂-EOR cannot be determined solely from the quantity of CO₂ injected or retained underground. Instead, the net climate impact depends on the balance between CO₂ retained in the reservoir and emissions associated with downstream processing of additional oil produced. Consequently, life-cycle assessment of CO₂-EOR should explicitly account for the fate and combustion of the additional oil produced.

7.7 Public opinion

Uncertainty around public opinion in the deployment of CCU technology, and lack of social acceptance of some CCU products is a significant obstacle for clear political decisions (Gonzales et al., 2020). Moreover, there is a risk that products may be perceived as greenwashing by end users due to a lack of studies/rules on the utilization products pathway, which may not effectively reduce or remove CO₂ in practice (Boston Consulting Group (BCG), 2024).

7.8 High costs and energy requirements

The high energy and cost requirements remain a major barrier to carbon capture and utilization/storage widespread adoption (Chauvy and De Weireld, 2020; Song, 2006). Technological pathways like CO₂-to-fuels and CO₂-to-chemicals, especially in PtX context, require significant energy input, especially in the form of renewable electricity, to operate within low-emission pathways (Tables 5, 6; Song, 2006; Kamkeng et al., 2021; Sillman et al., 2023). The conversion via PtF requires carbon feedstock, which can be supplied from carbon capture or DAC facilities, while hydrogen can be sourced via a water electrolysis plant. However, the economic gap between synthetic and conventional fuels remains the primary hurdle. The production cost of these e-fuels is higher than fossil-based fuels (International Energy Agency (IEA), 2019a), due to high capital expenditure for electrolyzers and high energy requirements. Besides, the production of these fuels can be influenced by regulations related to the fuel market, electricity market, electrolyser market, and carbon tax (International Energy Agency (IEA), 2019a; Koytsoumpa et al., 2018). For these technologies to be commercially viable, the energy required must be sustainable and cost-effective.

Table 5. Challenges for different carbon utilization pathways (Alberici et al., 2017; Boston Consulting Group (BCG), 2024; Dziejarski et al., 2023; CO₂ Sciences, The Global CO₂ Initiative, 2016; Zhang et al., 2024; Turakulov et al., 2024; Nagireddi et al., 2024; Pieri et al., 2018; Gowd et al., 2023; Parsons Brinckerhoff, Global CCS Institute, 2011; Al-Mamoori et al., 2017).

Table 6. Comparison of CO₂-derived products (Kamkeng et al., 2021; Bazzanella, 2019; Gerdemann et al., 2007; Sanna et al., 2014; Damen et al., 2005).

Conversion rate for £1 is taken as $1.27, while for 1€ is $1.2.

The need to overcome these barriers is of paramount importance for the transition to a low-carbon future. However, this will not be achieved through technological innovation alone. CCU deployment will require policy changes, significant investments, and public support as discussed in section 9.

8 Market

The current global market of CO₂ is estimated to be around $10.69 billion, and it is projected to reach $800 billion in 2030 with a potential to use 7 billion tons of CO₂ (15% of current global emissions) (CO₂ Sciences, The Global CO₂ Initiative, 2016; Fortune Business Insights, 2021). Currently, urea manufacturing and EOR account for approximately 130 Mt./y and 80 Mt./y, respectively, as mentioned earlier. The current carbon utilization is negligible compared to global carbon emission levels of 37.9 Gt in 2023, but the potential deployment of CCU can decrease this gap (Tiseo, 2021).

Each sector’s market is different and does not necessarily correspond with its ability to reduce greenhouse gas emissions (Table 7). The potential of every pathway is based on current market research and projections based on analysis of barriers and drivers (Bobeck et al., 2019; CO₂ Sciences, The Global CO₂ Initiative, 2016).

Table 7. Potential market trends and GHG reduction capacity of different CO₂ products (Bobeck et al., 2019).

Low-carbon concrete, for example, has a higher present market value than all other sectors (Bobeck et al., 2019). This is also reflected in Table 7 which illustrates the expected expansion of concrete to remain the largest CCU industry in terms of market value, while other sectors, such as low-carbon fuels, algae-based fuels and products, and aggregates will become significant but at a lower market size (Bobeck et al., 2019). However, CO₂ concrete has a low utilization potential when compared to aggregates and e-fuels (Boston Consulting Group (BCG), 2024; Bobeck et al., 2019). Aggregates and e-fuels may exceed concrete by 2030 in terms of potential greenhouse gas reduction by approximately 2 billion tons and 1 billion tons, respectively (Bobeck et al., 2019).

Additionally, the market forecast, as shown in Table 7, will grow by two-fold. This can be achieved with the right regulations that involve sector-specific market enablers, research and development, and provision of incentives and economy-wide climate policies (section 9) (Bobeck et al., 2019). Reaching these optimistic market forecasts and mitigation targets relies heavily on specific favorable conditions, particularly developed carbon infrastructure, favorable carbon policy, low-carbon energy, constant supply of raw materials, and inexpensive CO₂ sources (International Energy Agency (IEA), 2019a).

For energy-intensive pathways, as discussed in previous sections, particularly CO₂-derived fuels and chemicals, the availability and cost of renewable electricity and low-carbon hydrogen are main drivers of market competitiveness (International Energy Agency (IEA), 2019a). Hence, for these projections to be realized, it is assumed that significant cost reductions in renewable electricity and electrolyzers alongside a supportive regulatory framework are required (International Energy Agency (IEA), 2019a).

In addition to policy and energy requirements, CCU products must compete with established fossil-derived products. This competition is particularly important for CO₂-derived fuels, chemicals, and polymers, which must compete with mature production technologies, established supply chains, existing infrastructure, and relatively low-cost fossil feedstocks (International Energy Agency (IEA), 2019a). For instance, as discussed in the previous section, CO₂-based fuels and basic chemicals currently incur higher production costs than conventional petroleum-based fuels or chemicals (International Energy Agency (IEA), 2019a). Unless strict regulatory penalties are imposed on fossil carbon and/or substantial incentives are provided to green products, CO₂-derived products will struggle to achieve price parity (International Energy Agency (IEA), 2019a).

Therefore, the market projections in Table 7 should be viewed as potential trajectories that are dependent on energy costs, technological development, policy support, and the ability of CCU products to compete with conventional alternatives.

9 Policies

CCU technologies can drive towards a green and sustainable future by reducing global CO₂ emissions and marketable products. However, CCU technological pathways are relatively immature when compared to conventional technology or the products are not techno-economically feasible against existing marketable products (International Energy Agency (IEA), 2019a; Kamkeng et al., 2021). Moreover, Current policies hardly give incentives to investors in CCU technology and are revised slowly compared to the fast-changing nature of technology and markets (Zhang et al., 2020; International Energy Agency (IEA), 2019a).

These challenges are not uniform across countries. Developed countries generally have better financial and institutional capacity to support CCU deployment through subsidies, tax credits, funding, and regulatory frameworks, while developing countries face additional constraints related to access to finance, higher financing costs, limited domestic capital markets, and institutional capacity, which can complicate CCUS deployment (International Energy Agency (IEA), 2021; International Energy Agency (IEA), 2023; Kulichenko and ECharlotte, 2012; International Energy Agency (IEA), 2026).

Regulatory fragmentation between countries hampers CCU adoption and emerging economies hesitate to enforce strict mandates due to concerns about industrial competitiveness and energy security (Reed et al., 2024; United Nations Framework Convention on Climate Change (UNFCC), 2023; van der Hoeven, 2023). Even in the EU, policies need revision for effective CCU technology deployment. Ensuring consistency by revising Trans-European Networks for Energy (TEN-E) and other legislation, such as the EU Taxonomy and the EU Emissions Trading System (ETS) Directive, is crucial (CCUS SET-Plan, 2021).

Policies can promote the CCU pathways at local and international levels and aid in developing frameworks that promote industrial innovation, commercialization of technological pathways, financial investments, and opening of new markets (Zhang et al., 2020; International Energy Agency (IEA), 2019a; Kamkeng et al., 2021). Governments will play a vital role in disseminating information to the public and setting up standards with concerned authorities pre-emptively for CCU products (Zhang et al., 2020; International Energy Agency (IEA), 2019a). This allows fast public engagement with CCU products (Zhang et al., 2020). A range of different policies can be used to drive the deployment of CCU technology.

9.1 Raising awareness between the public and the private sectors

9.1.1 Conducting LCA and techno-economic analyses

A recognized LCA methodology is essential to demonstrate the emission reduction potential of CCU products during the whole lifecycle of the product (Alberici et al., 2017; Bobeck et al., 2019). Moreover, a detailed LCA and techno-economic assessment of different CCU products will help businesses (both public and private) to understand the current state of the different technologies, the timeframe of costs and revenues, the business feasibility, and the pathway with higher returns (Alberici et al., 2017).

This could aid especially the products that are relatively close to commercialization. For example, The Government of Ontario, Canada, is investigating ways to include emission reduction in CO₂-derived cement and aggregates in public procurement rules (Environmental Commissioner of Ontario, 2017).

In addition to environmental and economic factors, integrating social impact assessments into these evaluations is critical for a more comprehensive understanding of CCU technologies (Gowd et al., 2023). Such assessments begin by identifying key stakeholders, typically plant workers, consumers, and nearby communities, and evaluating how they are affected by various impact categories (Gowd et al., 2023; Hossain et al., 2018; Foolmaun and Ramjeeawon, 2012). These include workplace conditions (e.g., fair salary, equal opportunities), consumer rights (e.g., product transparency, end-of-life responsibility), and community well-being (e.g., secure living conditions, local employment) (Gowd et al., 2023; United Nations Environment Programme, 2009). Including these social indicators can guide responsible decision-making and align CCU development with broader sustainability development goals (SDGs), such as SDGs 3 (Good Health and Well-being) and 8 (Decent Work and Economic Growth) (Gowd et al., 2023).

For emerging economies should also focus on developing local expertise, regionally representative LCA datasets, and standardized procedures for environmental assessment and verification. This will improve the ability of domestic institutions to evaluate CCU technologies and generate credible environmental information for low-carbon products (UNEP, 2020). This information will reduce the risk of barriers to international trade (UNEP, 2020).

9.1.2 Product labelling and certification

Labelling provides information regarding the sustainability of manufacturing a product by indicating the emission reductions observed (International Energy Agency (IEA), 2019a). This can aid individuals, governments, and private industries to decrease their respective carbon footprint by opting for products that have a more sustainable supply chain (Alberici et al., 2017; International Energy Agency (IEA), 2019a). Similarly, certifications are required to know whether the product complies with the standards defined by competent organizations (International Energy Agency (IEA), 2019a). This compliance is especially important for building materials and fuels against the respective standards (International Energy Agency (IEA), 2019a). The EU energy label scheme and the US Energy Star program are two examples of product labelling.

9.2 Mandates

The regulatory requirements set by governments for products to meet certain criteria (e.g., emission criteria) will allow CCU products to enter the market (International Energy Agency (IEA), 2019a; Bobeck, 2019). This law will also allow the avoidance of products with high carbon emissions to enter the market (International Energy Agency (IEA), 2019a). For example, Renewable Energy Directive (RED), in the EU, sets the emission criteria for transport fuels and targets at least 14% renewable energy penetration by 2030 in the road and rail transport sector (International Energy Agency (IEA), 2019a; Vella et al., 2026). Moreover, RED allows the use of fuels obtained from the CCU pathway if they reduce the emissions by 70% and all the underlying energy stream is renewable (International Energy Agency (IEA), 2019a). Furthermore, the expansion of the EU Emissions Trading System (ETS) to the transport sectors, mandating emission intensity reductions of at least 14.5% by 2030 or the share of renewable energy in transport is at least 29% by 2030 (Vella et al., 2026). Besides this, the ReFuelEU Aviation Initiative proposed the use of sustainable fuels by 63% with synthetic aviation fuels by at least 28% by 2050 (European Commission, 2021). Similarly, The Low Carbon Fuel Standard (LCFS) in California, USA, corroborates the decrease in the GHG intensity of fuels supplied by CO₂-EOR (International Energy Agency (IEA), 2019a). Moreover, an alternate approach is to use blending of CCU products with conventional fossil fuel-based products can create a market share (Gowd et al., 2023; Becattini et al., 2021). An example is the use of the E10 fuel blend in India (10% biofuel and 90% conventional fuel) and the E27 fuel blend in Brazil (27% biofuel and 73% conventional fuel) (Gowd et al., 2023). The blending of ethanol with gasoline contributed to a reduction of 31.8 million tons and 1.32 billion tons of CO₂ in India and Brazil, respectively (Gowd et al., 2023).

9.3 Economic incentives

Economic incentives can make CCU technology more viable by providing guarantees and allowing the products to compete in the marketplace (Bobeck, 2019; Ghazzawi and Khowaiter, 2022). Economic incentives reduce the risk of investment by lowering or sharing costs between public and private sectors and by providing revenue streams (International Energy Agency (IEA), 2019a; Ghazzawi and Khowaiter, 2022). This is possible by the provision of capital for projects or tax incentives (International Energy Agency (IEA), 2019a; Ghazzawi and Khowaiter, 2022). CCU technology is advancing in different countries using tax incentives.

Another important financial tool is carbon credit markets, where CCU industries can sell their emission reductions as tradeable credits. The EU-ETS and California’s LCFS have included CCU-based credits, offering between $50 and $70 per ton of CO₂ reduction, depending on the type of project (California Air Resource Board, n.d.; BloombergNEF, 2024). Additionally, the World Bank’s Green Bond Program and other climate funds have started to support CCU projects, reflecting growing investor confidence in the long-term potential of carbon utilization markets (World Bank, 2024).

The USA introduced 45Q tax credits in 2018 to promote the deployment of CCU technology. 45Q tax credit is applicable for 12 years from the start of production/operation with the tax credit ranging from $12-50 per ton of CO2 captured and stored (International Energy Agency (IEA), 2019a; McMahon, 2021). The government of the UK supported the design and construction of sustainable aviation fuels with funding of £180 million (International Energy Agency (IEA), 2024b).

9.4 Research and development

R&D will play a vital role in designing and techno-economically comparing innovative ways to store CO₂. These will lead to further planning of CCU technologies that can scale up technologies, making the CO₂ pathways efficient, and aiding in commercialization of the technologies (International Energy Agency (IEA), 2019a; Gowd et al., 2023; Bobeck, 2019; McMahon, 2021).

Emerging research and development efforts are employing Artificial Intelligence (AI)-driven process optimization to improve the efficiency of CCU pathways (European Commission, n.d.). AI algorithms are employed to identify cost-effective strategies for resource allocation, energy management, and overall process optimization. These advancements help to lower operational costs and enhance the scalability of Carbon Dioxide Removal (CDR) technology (European Commission, n.d.). By increasing both the efficiency and effectiveness of CDR technology in reducing carbon emissions, these methods contribute to the development of sustainable energy systems (European Commission, n.d.). The integration of AI with CDR technology has positive effects on the environment, the economy, and energy consumption by minimizing energy use, optimizing costs, and enhancing energy efficiency (European Commission, n.d.). The European Commission (EC) funded around $273 million in 61 projects on CCU technologies in the last decade (International Energy Agency (IEA), 2019a). Moreover, the EC will fund € 38 million in small and large-scale projects under the Innovation Fund from 2020 to 2030. This investment will target low-carbon technologies, CCU, CCS, innovative renewable energy generation, and energy storage (International Energy Agency (IEA), 2009). Furthermore, the US Department of Energy Carbon Use and Reuse R&D portfolio and the Chinese 13th Five-Year Plan sector strategies are some examples to aid in the R&D of carbon utilization pathways (International Energy Agency (IEA), 2024b). This can also include the American Recovery and Reinvestment Act, the CCUS Hubs and Technologies Program in Australia, and the CCS Funding program in Canada funded $3,000 million, AUD 250 million, and $ 248 million, respectively to promote R&D and CCUS deployment (Dziejarski et al., 2023; Minister for Resources and Water, 2021; Center for Strategic and International Studies, 2022; Itul et al., 2023).

The investment is not restricted to public funding for R&D. The majority of venture capital (VC) businesses are based in the US, UK, and Canada; together, they make up 67% of all active VC firms worldwide (World Bank, 2023). With 38% of active venture capital firms and half of the top 30 businesses with the most funds raised, the US leads the world. Just ahead of the UK and Canada, the EU accounts for 18% of the recognized venture capital firms, with a third of them situated in Germany (World Bank, 2023). Detailed data on private sector R&D spending remains limited.

In 2023, global VC investment in CO₂ utilization reached nearly $500 million, making up almost half of all VC investment in CCUS (International Energy Agency (IEA), 2024b; Boston Consulting Group (BCG), 2024). While fuel and chemical production dominate utilization applications in large-scale capture facilities, investments are well-distributed, with fuels receiving 33%, chemicals 40%, and building materials 25% (International Energy Agency (IEA), 2024b; Boston Consulting Group (BCG), 2024). Since 2017, utilization, focused on CO₂-to-fuels and chemicals, has attracted about half the investment in capture and storage, reflecting its recognized potential (International Energy Agency (IEA), 2024b; Boston Consulting Group (BCG), 2024).

However, the ability of emerging economies to provide subsidies, tax credits, and other fiscal incentives can be constrained as mentioned previously. Access to private capital is also more limited in many emerging economies, where financing costs can be higher or riskier than in developed economies. Therefore, international concessional finance, development-finance institutions, public-private partnerships, and risk-sharing mechanisms can be particularly important for enabling CCU investment in emerging economies (International Energy Agency (IEA), 2026; Li G. et al., 2024).

10 Conclusion

The race towards a carbon-neutral economy, which will further be translated to a net-zero carbon economy in the future, possesses different barriers and opportunities. RES systems are essential to decarbonize the power industry. However, considering the intermittent nature of power generation via RES, fossil fuel consumption in power generation, chemical, and fuel industries (to mention a few) still dominate the market globally. CO₂ emissions from these industries need to be captured and utilized (or stored) as there is a significant difference between the CO₂ consumed in industries (250 Mt. in 2023) and the CO₂ emitted from different industries (37.9 Gt in 2023). The decarbonizing strategy via CCU will play a vital role in reducing the impact of GHG on the environment and maintaining the global temperature increase below the required threshold of 1.5 °C. Considering CCU technologies selected pathways such as mineralization, EOR, ECBM, and construction materials support long-term carbon sequestration and complement broader CDR strategies.

A comprehensive set of technologies with different statuses for each CO₂ utilization pathway, i.e., fuels, chemicals, polymers, aggregates, concrete, curing, EOR, ECBM, bio-products, and horticulture, is emerging. The conversion pathways can yield potential economic benefits and high emission reduction potential, but there are significant challenges and barriers to overcome in commercial deployment. These include the high cost of transporting CO₂, the ambiguity surrounding the prioritization of CO₂ utilization, safety concerns at the site, lack of social acceptance, a lack of policies, and the requirement for lifecycle analysis studies. Overcoming these challenges requires a collaborative effort from governments, industry, and research sectors that will not only drive innovation but also create investment opportunities and a supportive regulatory framework.

Furthermore, the development of robust policies is essential to incentivize the adoption of CCU technologies and create a conducive environment for their deployment. Policies should focus on raising awareness, implementing product labelling and certification schemes, setting mandates, providing economic incentives, and supporting research and development initiatives. Therefore, a collaborative effort is imperative to unlock the potential of a future CO₂ market by advancing these innovations toward commercial viability, thereby accelerating the transition to a low-carbon economy.

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Footnotes

Edited by: Aage Stangeland, The Research Council of Norway, Norway

Reviewed by: Celso Da Silveira Cachola, Serviço Nacional de Aprendizagem Industrial, Brazil

Youan Ji, Hebei University of Science and Technology, China

Footnotes

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