A novel technological conception of integrated large-scale CO2 storage, water recovery, geothermal extraction, hydrogen production, and energy storage
Abstract
Carbon capture, utilization, and storage (CCUS) is widely recognized as a technological system capable of achieving large-scale carbon dioxide emission reductions. However, its high costs and potential risks have limited its large-scale implementation. This study focuses on enhancing the economic viability of traditional CCUS by proposing a novel technological concept and system that integrates CCUS with water extraction, geothermal energy harvesting, hydrogen production, and energy storage. The system comprises three interconnected modules: (1) upstream CO2-enhanced water recovery (CO2-EWR), (2) midstream green hydrogen synthesis, and (3) downstream energy utilization. Through detailed explanations of the fundamental concept and related technological systems, its feasibility is demonstrated. Preliminary estimates indicate that under current conditions, the system lacks economic advantages. However, significant reductions in hydrogen production costs could enable the system to yield a profit of nearly 1000 Chinese Yuan (approximately 145 US dollars) per ton of CO2 in the future. Following an in-depth investigation, priority implementation in China's Tarim Basin and Ordos Basin is recommended. This technological system could significantly extend the industrial chain of traditional CCUS projects, promising additional social and ecnomic benefits. Furthermore, the involved gas–water displacement technology can help manage formation pressure and reduce leakage risks in large-scale carbon storage projects.
Highlights
A novel technological conception of a integrated utilization system that combines large-scale CO2 storage, water recovery, heat extraction, hydrogen production, and energy storage.
An extended industrial chain of carbon capture, utilization, and storage projects with economic and social benefits, as well as the promotion of application value.
Potential of earning a profit of 1000 Chinese Yuan (145 US dollars) per ton of CO2 as technology matures and costs decrease in the future.
A suggestion is to prioritize implementations in China's Tarim Basin and Ordos Basins.
1 INTRODUCTION
The accelerating pace of global industrialization has driven a persistent surge in atmospheric carbon dioxide (CO₂) concentrations. Heightened awareness of climate change impacts and greenhouse gas dynamics has propelled carbon regulation to the forefront of international policy agendas. In response to this environmental imperative, nations worldwide have ratified carbon neutrality agreements through multilateral cooperation (Ji & Zhang, 2016). Notably, China formally committed to achieving carbon peak emissions by 2030 and carbon neutrality by 2060 in the general debate of the 75th United Nations General Assembly (Xi, 2020). Addressing the dual challenge of meeting escalating energy demands while achieving decarbonization objectives requires multidimensional strategies, including (a) optimization of energy efficiency; (b) development of low-carbon alternative fuels; (c) large-scale deployment of renewable energy systems including solar, wind, and bioenergy; (d) implementation of ecological restoration initiatives such as strategic afforestation programs; and (e) CO2 capture and storage (Leung et al., 2014; Zou et al., 2021). Among them, carbon capture, utilization, and storage (CCUS) technologies have emerged as particularly critical solutions. Modern CCUS systems employ innovative physicochemical processes to capture CO₂ emissions from diverse industrial sources and energy generation facilities. The captured CO₂ undergoes transportation via specialized pipelines or maritime vessels to designated utilization sites or geological storage formations. Besides, contemporary applications extend beyond enhanced oil recovery to include emerging fields such as biofuel production (Figure 1). As a pivotal climate mitigation technology, CCUS is projected to contribute approximately 20% of the required global CO₂ emission reductions by mid-century (Zhang et al., 2018).
Decarbonization persists as an existential priority for global climate governance, with the next decade being a critical implementation window for scaling CCUS technologies to meet mid-century emission reduction targets (Zoback & Smit, 2023). Nevertheless, the significant financial cost and energy penalty associated with CCUS projects seriously restrict their commercial development and industrialization process (Liu et al., 2017; Sang et al., 2022; Zhang et al., 2018; Zhang, Li, et al., 2021). This has precipitated an urgent research and innovation imperative: the development of integrated CCUS solutions or pathways that simultaneously achieve large-scale deployment capacity, cost-competitive economics, and operational risk mitigation.
To address these challenges, innovative mitigation strategies and hybrid technical solutions are proposed. Since carbon capture accounts for 70%–80% of the total expenditures in the CCS system (Leung et al., 2014; Zhang et al., 2018), some academics have proposed several carbon capture technologies in conjunction with renewable energy to minimize energy consumption. Zhao et al. systematically analyzed solar-assisted carbon capture technologies across postcombustion, precombustion, and oxy-fuel combustion configurations, evaluating separation techniques and technological advancements (Zhao et al., 2016). Xing et al. developed a comprehensive utilization technique of concentrated photovoltaic power generation and carbon capture with residual heat-driven carbon capture, achieving efficient cascade utilization of solar energy for simultaneous power generation and emission reduction (Xing et al., 2020). Additionally, low-to-medium temperature geothermal energy has been proposed as a sustainable heat source for postcombustion carbon capture processes (Wang et al., 2017). Furthermore, wind turbine units can also be integrated with carbon capture systems to participate in power dispatch as hybrid energy assets. Research demonstrates that such virtual power plants exhibit dual advantages in economic efficiency and environmental sustainability (Zhou et al., 2018). Zhang et al. pioneered a novel energy storage technology utilizing captured CO2 as the energy storage medium in renewable energy power plants (Zhang et al., 2021). Through CO2 compression or its conversion into high-energy-density compounds, surplus energy generated during peak renewable production periods is stored and subsequently released during energy deficits. These synergistic technologies enhance renewable energy utilization efficiency while partially offsetting the negative effects of renewable energy's instability.
Along with reducing energy consumption in the early stages, enhancing the long-term economic returns of CCS projects presents a viable strategy to improve their economic viability. A prominent application exemplifying this approach is CO2-enhanced oil recovery (CO2-EOR), where injected CO₂ serves dual functions: (1) providing driving force to extract residual oil from depleted formations, and (2) achieving permanent geological storage of CO2 in the subsurface reservoirs (Dai et al., 2013; Farajzadeh et al., 2020; Ren et al., 2022; Wang et al., 2018). This synergistic process partially offsets the high expense associated with the CCS operations. Similar methodologies have been applied to other subsurface systems: CO2-enhanced gas recovery (CO2-EGR) targets natural gas reservoirs, while CO2-enhanced coal bed methane (CO2-ECBM) focuses on deep coal seams (Ezekiel et al., 2020; Song et al., 2024). A parallel innovation, CO2-enhanced water recovery (CO2-EWR), removes formation water to the surface to increase CO2 storage capacity (Ziemkiewicz et al., 2016). The produced water is then purified for beneficial use, such as agricultural utilization and industrial processing (Li et al., 2013a). Special treatments are frequently required because the produced water usually has a rather high degree of mineralization (Li et al., 2013b). Saline aquifers offer distinct advantages over conventional reservoirs: (1) broader geographical distribution (Kumar et al., 2020); (2) estimated CO2 storage capacity in China's deep saline aquifers reaches 2420 billion tons (Chinese Academy of Environmental Planning et al., 2021), which is almost equal to 223 times the national CO2 emissions in 2021 (10.87 billion tons [BP p.l.c., 2022]); (3) mitigate the excessive build-up of reservoir pressure due to CO2 injection, thus lowering the risks of induced earthquakes and gas leakage. These attributes position CO₂-EWR as a pivotal deep decarbonization solution (Li et al., 2013a).
However, the following critical challenges constrain the implementations. First, when ignoring factors such as the deformation of the rock and the difference in the adsorption of water and CO2 by the rock mass, the volume of the fluid in space before and after displacement should be consistent. Thus, one cubic meter of water occupies the same volume as one cubic meter of CO2. In the context of large-scale CO2-EWR projects, the disposal of large-scale saline water not only poses a new challenge but also introduces an additional cost to the whole CO2-EWR system. Additionally, CO2-EWR is less understood than CO2-EOR or CO2-ECBM, resulting in a relatively limited scale of implementation (CO2 injection capacity
As previously discussed, numerous obstacles persist in developing large-scale CCUS projects, which have inspired innovative solutions from researchers and practitioners. Addressing the challenges through expanding comprehensive integration, boosting storage capacity, and enhancing additional benefits is a potential breakthrough path. The key objective of this paper is to propose a holistic utilization technology that integrates large-scale CO2 storage, EWR, geothermal energy extraction, green hydrogen production as well as energy storage. The structure of this paper is as follows. Section 2 details the conceptual framework and technical underpinnings of the proposed holistic CCUS system, including process design and integration mechanisms. Section 3 examines the benefits of the proposed approach and provides preliminary economic assessments. Section 4 identifies priority deployment regions through geospatial analysis tailored to China's specific national conditions. Finally, some conclusions are reached as illustrated in Section 5.
2 BASIC PRINCIPLES AND TECHNICAL SYSTEMS
2.1 Theoretical systems
Building upon the conceptual framework, the proposed system integrates three synergistic components as illustrated in Figure 2. The holistic system integrates CO2 storage, EWR, green hydrogen production, and multi-energy utilization. It extends the CCUS industry chain, striving to maximize the extraction of diverse resources for enhanced social and economic gains, and offers a novel paradigm for large-scale CCUS initiatives. Depending on its connotation, it is structured into upstream, midstream, and downstream industries (Figure 2). In the upstream industries, the brine in the saline aquifers flows under the driving force of injected CO2 and is eventually collected from the production wells for further processing. The produced water is recognized as an energy carrier in the midstream industries. Meanwhile, green hydrogen is prepared with the support of renewable energy, including solar energy and biomass energy. Through technologies including hydrogen fuel cells and energy storage, downstream industries are able to extract and harness diverse resources, such as geothermal energy, mineral resources, and hydrogen energy. The detailed substance and guiding conceptions of the merged system are as follows.
2.1.1 Upstream industries: CO2-EWR
There are four main mechanisms for CO2 trapping in deep saline formations during geological sequestration, as shown in Figure 3a (Bello et al., 2023). (i) Structural and stratigraphic trapping. Upon injection, CO2 migrates upward due to buoyancy, but is immobilized beneath impermeable caprocks, forming a structural trap. (ii) Residual trapping. During CO₂ migration through a porous medium, a portion of the CO₂ becomes immobilized within the pore spaces due to capillary forces and interfacial tension between the CO₂ and formation water. (iii) Mineral trapping. Over extended periods, the direct or indirect interaction between injected CO2 and minerals in host rocks precipitates secondary carbonate minerals, permanently sequestering carbon. (iv) Dissolution or solubility trapping. It refers to the dissolution of CO2 into formation water, which is influenced by the formation's pressure, temperature, salinity, and so on.
The relative contributions of various trapping mechanisms, as well as the associated storage security, evolve significantly across different postinjection periods (Figure 3b) (IPCC, 2005). These dynamics are governed by various factors, such as geological properties and formation brine composition. For a given saline aquifer reservoir, CO2 storage capacity mostly derives from the pore space of unsaturated water, the dissolution of CO2 into formation water, and the storage of residual CO2. However, in fully saturated formations, the volume of CO2 trapped in the tectonics is extremely constrained, while the solubility of CO2 in formation water is also minimal, resulting in suboptimal storage potential. Given that structural trapping is the most vital mechanism of CO2 storage, the concept of extracting formation water to allocate pore space for CO2 storage presents a significant capacity enhancement. This principle provides critical scientific justification for CO2-EWR. The holistic system proposed in this study is also an application of such a principle. In the upstream industries, formation brine displaced by injected CO₂ migrates toward production wells. The extraction of saline water creates room for CO2, considerably increasing the CO2 storage capacity. This behavior corresponds to the structural trapping in Figure 3. Simultaneously, the extraction of brine alleviates formation overpressure associated with continuous CO2 injection, demonstrating superior storage security over traditional CCUS operations.
The directly obtained resource in the upstream industries of the proposed holistic utilization system is the mineralized brine extracted from production wells. The produced water may contain dissolved CO2, which undergoes separation processes for reinjection into the CO2-EWR system. The midstream and downstream industries of the holistic utilization system will utilize the processed brine for subsequent applications.
2.1.2 Midstream industries: Production of green hydrogen
The midstream industries of the integrated utilization system focuses on green hydrogen production via two primary pathways: photocatalytic water splitting and electrolytic water splitting, both powered by renewable energy (Figure 4). These technologies address distinct technical and economic considerations for sustainable and large-scale hydrogen generation.
The essence of photocatalytic water decomposition for hydrogen production lies in the photoelectric effect of semiconductor materials, also known as photocatalysts (Xu & Weng, 2023). When the energy of the incident light equals or exceeds the bandgap energy of the semiconductor, valence band electrons are excited to the conduction band, generating photogenerated electron-hole pairs. These charge carriers migrate to the material surface, driving redox reactions with water to yield oxygen and hydrogen. In water electrolysis, hydrogen production methods are classified by electrolyte type: alkaline water electrolysis (AWE), proton exchange membrane (PEM) fuel cells, and solid oxide electrolysis cells (SOEC) (Cavaliere et al., 2021). Despite variations in electrolysis materials and operating conditions, all methods follow identical electrochemical principles, that is, oxygen evolution at the anode and hydrogen evolution at the cathode.
As depicted in Figure 4, the first activity in the midstream industries of the proposed system is renewable energy generation. The produced water with low salinity then serves as an energy carrier, enabling hydrogen production via electrolysis. Alternatively, hydrogen can be generated through photolysis by direct solar energy utilization or electrically powered light energy. The resultant hydrogen and oxygen by-products are transported to downstream industries for high-value applications.
2.1.3 Downstream industries: Energy utilization
The downstream industries of the proposed system focus on high-value resource utilization across multiple scenarios, including industrial, agricultural, commercial construction, transportation, and energy storage applications (Figure 5). It can be further divided into two halves: A and B, as shown in Figure 2. Part A involves the direct utilization of produced water extracted from deep saline aquifers. Due to the reservoir depth, the produced water exhibits elevated temperatures, containing significant geothermal energy reserves. This geothermal energy can be harnessed for geothermal power generation, geothermal heating, and so on (Wang et al., 2023). Additionally, the brine produced contains substantial liquid mineral resources due to its high level of mineralization. These mineral resources can be extracted through multiple processes. Furthermore, a variety of sectors can make extensive use of these resources. For instance, bromine can be used to produce photosensitive materials.
Part B focuses on maximizing the utilization of hydrogen energy derived from midstream industries to improve the economic viability of CCUS projects. Hydrogen functions as a versatile energy carrier with multiple high-value applications, including hydrogen power generation, hydrogen fuel cells, and underground hydrogen storage. Concurrently, hydrogen oxidation generates high-purity water as a byproduct. These freshwater resources, characterized by low total dissolved solids, can be used for industry, agriculture, and residential life to alleviate the current situation of regional water scarcity.
Additionally, water can also serve as an effective thermal energy storage medium, enabling the integration of intermittent renewable energy sources. Excess photovoltaic or electrical energy can be converted into thermal energy via resistive heating or heat pump systems, producing high-temperature water. This thermal energy carrier can then be injected into geological formations for strategic energy storage. It is worth noting that target formations are not limited to deep aquifers. Thermal energy from geothermal water can be extracted and utilized during periods of high energy demand. From the standpoint of downstream industries, the CCUS value chain has been greatly expanded, with resource utilization rates substantially improved.
Some information and research progress about these technologies can be referred to Bacquart et al. (2024), Durkin et al. (2024), Fan et al. (2020), Ji et al. (2024), Kalam et al. (2023), Pai et al. (2024), and US National Clean Hytrogen Strategy and Roadmap (2023).
2.2 Assessment of the maturity of critical technologies
The proposed conceptual framework demonstrates the theoretical feasibility, as previously outlined. However, its practical implementation hinges critically on the maturity of constituent technologies. The core technologies include carbon capture, CO2 storage in deep saline aquifers, geothermal energy extraction, mining valuable minerals from produced water, green hydrogen production with renewable energy, and water desalination. Preliminary data indicate that these technologies have achieved varying degrees of engineering application, establishing a technical foundation for system implementation. For example, the chemical absorption method, one of carbon capture technologies, has been deployed in China's Guohua Jinjie CCS project (with an annual capture capacity of 150 000 tons of CO2) and Shidongkou CCS project (with an annual capture capacity of 120 000 tons of CO2) (Survey, 2018; Zhang & Wang, 2019).
However, several existing technologies remain insufficiently mature to fully enable the implementation of the proposed system. For instance, deep geothermal energy project has a high degree of risk and is still in the research stage (Zhao & Wan, 2014), despite substantial advancements in low- to medium-temperature geothermal systems. While low- to medium-temperature geothermal extraction technologies provide foundational insights for deep geothermal applications, further scientific breakthroughs are required.
Detailed information on some representative engineering projects is provided in Appendix A. Overall, the core technologies within the proposed integrated utilization system have a certain level of maturity in technique and technology and have the potential for large-scale development. But there are still a series of challenges that need to be overcome.
3 EVALUATIONS OF THE BENEFITS
3.1 Benefit analysis
1.
A new integration scheme of CCUS and hydrogen energy.
In contrast to the traditional hydrogen production routes that use fossil fuels as raw materials and reduce carbon emissions by equipping CCUS facilities, this paper introduces a new collaborative solution between CCUS and hydrogen energy. This solution can simultaneously resolve the disposal problem of produced water in CO2-EWR projects and the challenge of acquiring water resources in the hydrogen production. The cooperative approach will have significant value in promoting the large-scale implementation of CCUS as well as in facilitating the reform of the energy structure.
2.
A green hydrogen production process that fully utilizes renewable energy.
The midstream industries of the newly proposed system seek to produce green hydrogen energy. “Green” here has two distinct meanings. First, the production method of hydrogen energy (water photolysis or water electrolysis) is environmentally friendly and emits little CO2 during the process. Second, the energy consumption is green since the light or electricity consumed in hydrogen energy production is sourced from clean, renewable energy.
3.
An indirect desalination scheme for saline water.
The system utilizes brine as a feedstock, with high-purity hydrogen as the principal product. The byproduct of the hydrogen utilization process is fresh water, which can be further utilized for agricultural irrigation, domestic water supply, and other application scenarios to address the challenges of regional water scarcity.
4.
Maximizing the utilization of various resources.
The rich resources in the produced brine, including geothermal energy and mineral resources, are recovered to the greatest extent feasible by combining different strategies. Moreover, the green hydrogen produced can be effectively utilized in various situations. Additionally, freshwater resources—a byproduct of hydrogen energy utilization—are also effectively exploited. More crucially, surplus resources can also be stored within the presented holistic system to achieve energy storage. Compared to conventional approaches, the downstream industries of the proposed system is expected to achieve a marked improvement in both the extraction and utilization rates of valuable resources.
1.
Significantly increasing the CCUS storage capacity.
2.
Thoroughly resolving the disposal problem of extracted saline water.
3.
Opening up a new pathway for the development of new green hydrogen energy.
4.
Opening up a new approach for ecological governance in arid areas.
5.
Additional economic and social advantages.
3.2 Economic analysis
In this section, the costs and benefits of the full-process project will be estimated (Table 1). Wei et al. conducted an economic assessment of the full-chain CO2-EWR projects, in which CO2 is captured from China's coal chemical factories (Wei et al., 2021). Assessing the actual production of coal chemical factories in 2018, the annual cumulative CO2 emission reduction was 160 Mt with a levelized cost of less than 200 Chinese Yuan (CNY; approximately 28.94 US Dollars, USD) per ton of CO2, and the corresponding saline water production was 241 Mt. It is estimated that the cost of the CO2-EWR operations is close to 32 billion CNY (4.63 billion USD) per year.
| Link | Current situation (2024) | Future vision (2050) | References | ||
|---|---|---|---|---|---|
| Cost (billion CNY/year) | Benefits (billion CNY/year) | Cost (billion CNY/year) | Benefits (billion CNY/year) | ||
| Full chains CO2-EWR projects | 32.00 | — | 32.00 | — | Wei et al. (2021) |
| Geothermal energy | — | 13.55 | — | 13.55 | |
| Special treatments for production water with high salinity | 1.45 | — | 1.45 | — | Li et al. (2015); Wu et al. (2021) |
| Renewable energy-based green hydrogen production | 449.87 – 1365.67 | — | 146.21 – 168.70 | — | Guo et al. (2021); Wang et al. (2021) |
| Gaseous hydrogen refueling station | 198.31 | 482.00 | 198.31 | 482.00 | CEIC (2023) |
| Comprehensive utilization of oxygen | — | 61.31 | — | 61.31 | Average market prices of oxygen, nitrogen, and argon (2023) |
| Utilization of water | — | 0.51–0.94 | — | 0.51 – 0.94 | Price H2O-China (2024) |
| Total (billion CNY/year) | 681.62 – 1597.42 | 557.37 – 557.80 | 377.96 – 400.45 | 557.37 – 557.80 | |
| Net profit (billion CNY/year) | −1039.84 to −124.04 | 156.91 – 179.84 | |||
| Net profit (billion USD/year) | −150.48 to −17.95 | 22.71 – 26.03 | |||
Abbreviations: CNY, Chinese Yuan; EWR, enhanced water recovery; USD, US Dollars.
Although the extracted saline water undergoes temperature reduction during geothermal energy extraction, its high mineralization level necessitates specialized treatment processes. Advanced desalination technologies such as membrane distillation and electrodialysis are recommended (Li et al., 2015). Drawing on established seawater desalination cost benchmarks, the unit treatment cost for saline water is approximately 6 CNY/ton (Wu et al., 2021). Based on this, the total cost of treating 241 Mt of produced saline water is 1.446 billion CNY (0.21 billion USD).
The extracted saline water can also be used for the extraction of valuable mineral resources such as bromine and potassium. The corresponding technology is similar to engineering techniques such as bromine extraction from seawater. However, the total dissolved solids in extracted saline water range from 3 to 50 g/L while the concentration of Cl− in seawater is only 19.1 g/L (Li et al., 2013b). This means that the extraction of valuable mineral resources from saline water is more promising than that from seawater. It also implies that further development is needed in related technologies. Due to limited research on the reserves of valuable minerals in saline water, no benefit calculations are provided in this regard.
The treated water with low mineralization is used for hydrogen production. The cost of manufacturing hydrogen from renewable energy electricity varies depending on the source of electricity, ranging from 28 to 85 CNY/kg H2 (Wang et al., 2021). Assuming a renewable energy-to-hydrogen conversion efficiency of 60% (Guo et al., 2021), it results in an annual hydrogen production of 16.07 Mt, with the corresponding oxygen generation amounting to 128.53 Mt. Following this, the cost of hydrogen production is estimated at 449.87 to 1365.67 billion CNY (65.10 to 197.64 billion USD).
In the designed economic scenario, all hydrogen produced is allocated to hydrogen supply stations. The cost of this link includes project construction, equipment depreciation, maintenance costs, and so on. The annual operating expenses of a typical gaseous hydrogen refueling station with a daily refueling capacity of 500 kg, considering the aforementioned factors, reach 2.16 billion CNY (0.31 billion USD). To absorb 16.07 Mt of hydrogen gas, it is necessary to build 9.18 × 104 stations of such a scale. The total investment amounts to 198.3 billion CNY (28.70 billion USD). The benefits stem from the sale of hydrogen gas. In Beijing, China, the selling price of hydrogen is 30 CNY/kg H2 (CEIC, 2023). Therefore, the estimated revenue from hydrogen sales reaches 482 billion CNY (69.75 billion USD).
The oxygen generated as a byproduct of water electrolysis for hydrogen production presents significant economic opportunities across multiple sectors, including industrial steelmaking, healthcare, and chemical manufacturing. According to market data from BAIINFO-China and Longzhong Chemical, the average price of oxygen in China is 477 CNY/ton (Average market prices of oxygen, nitrogen, and argon, 2023). Therefore, the full utilization of oxygen brings an economic benefit of 61.31 billion CNY (8.87 billion USD).
The hydrogen purchased by consumers is used for heating, power supply, transportation, and so on. In these processes, the product of hydrogen utilization is water, which could be further collected and utilized. Taking hydrogen fuel cells as an example, the product of hydrogen combustion—water—will be fully collected in an ideal scenario, that is, 144.6 Mt. The market value of this recovered water varies by application sector, with average selling prices of 3.54 CNY/ton for residential use and 6.5 CNY/ton for nonresidential use (Price H2O-China, 2024). Therefore, the portion of water can generate profits of 0.51 to 0.94 billion CNY (0.07 to 0.14 billion USD).
The cost–benefit data for the current technological framework are summarized in Table 1. However, under baseline conditions, the system incurs annual total costs of 681.62 to 1597.42 billion CNY (i.e., 98.64 to 231.18 billion USD), while generating comprehensive revenues of 557.37 to 557.80 billion CNY (i.e., 80.66 to 80.72 billion USD). This results in a significant cost overrun that hinders market viability. Cost structure decomposition reveals that green hydrogen production—integrated with renewable energy and deep saline water—accounts for 65% of total expenses, emerging as the principal constraint on industrial chain profitability.
According to the International Energy Agency (IEA), green hydrogen production costs in regions with abundant solar and wind resources are projected to range from 1.3 to 1.5 USD/kg H2, that is, 9.1 to 10.5 CNY/kg H2 (IEA, 2021; IEA, 2022). In this manner, the comprehensive utilization system costs approximately 377.96 billion to 400.45 billion CNY annually for the entire process, that is, 54.40 to 57.95 billion/year. The net profit is almost 981 to 1124 CNY/ton of CO2 (141.97 to 162.66 USD/ton CO2). In addition, the critical cost threshold for green hydrogen production is identified at 20.27 CNY/kg H2 (2.93 USD/kg H2).
Beyond quantifiable economic returns, the proposed comprehensive utilization system delivers broad advantages in carbon reduction, ecological environment, and other aspects. These benefits, while challenging to monetize, will contribute significantly to global sustainability goals and regional development priorities.
4 APPLICATION POTENTIAL
1.
The region boasts the strongest carbon reduction capability and superior solar radiation.
2.
On the other hand, this region is vast and sparsely populated, making it feasible for the corresponding project to serve as a demonstration base for research.
3.
Due to the reasonable levels of solar radiation and wind energy in the region, photovoltaic power generation and wind energy production can work together for hydrogen production. Utilizing hydrogen locally will reduce expenses and resource waste.
4.
However, transportation costs would increase to ensure optimal consumption of hydrogen energy. It is possible to consider developing the proposed system in slightly more densely populated regions like the Sichuan Basin once the technology matures and the holistic usage system gains widespread public acceptance.
It is also suggested to build related projects in China's Ordos Basin. Although its CO2 storage capacity is not the largest, the Ordos Basin has relatively complete infrastructure due to China's first CO2-EWR project being built there (IEE, 2021), which will effectively reduce construction costs in the later stage.
5 CONCLUSIONS
1.
The proposed system incorporates CO2 and renewable energy as inputs, while its output includes but is not limited to geothermal energy, mineral resources, hydrogen energy, oxygen, and water resources. It can also be combined with subsurface energy storage. The system is, therefore, an integrated utilization system.
2.
This paper provides a novel approach for coupling CCUS projects with hydrogen production. The comprehensive utilization system has simultaneously resolved the disposal problem of saline water extracted from large-scale CO2-EWR projects and the water supply issue in large-scale green hydrogen production projects. This coupling pathway can contribute to carbon neutrality in multiple ways.
3.
Some of component technologies in the newly proposed system, such as renewable energy generation, water electrolysis/photolysis for hydrogen production, and desalination of saline water, have achieved varying degrees of technical maturity, demonstrating that the system is technically feasible. However, a series of breakthroughs is still required to more effectively address the practical needs of scale, risk, and cost.
4.
A preliminary economic analysis reveals that the cost of green hydrogen production seriously restricts the benefits of the proposed system. The envisioned vision achieves economic breakeven when green hydrogen production costs decline below 20.27 CNY/kg (2.93 USD/kg) H2. Additionally, the net profit of the full utilization system has the potential to yield a profit of nearly 1000 CNY/ton (145 USD/ton) CO2 in regions with abundant wind and solar power resources.
5.
Based on careful deliberation, it is recommended that demonstration bases and pilot studies be established first in China's Tarim Basin or Ordos Basin. As relevant technologies mature and become more widely accepted, the comprehensive system can gradually be implemented in other areas like the Sichuan Basin.
The integrated framework presented in this study provides a new paradigm in carbon neutrality strategies, delivering specific financial and substantial social benefits while aligning with national decarbonization objectives. However, the content of this manuscript is still lacking. To promote the implementation of the project, a more detailed economic report and feasibility analysis report are required. In addition, it is also necessary to consider the impact of political factors and other factors on the project. This is the work to be carried out in the future.
AUTHOR CONTRIBUTIONS
Huiling Ci: Methodology; investigation; formal analysis; data curation; visualization; writing—original draft. Bing Bai: Original idea and conceptualization; project administration; funding acquisition; methodology; supervision; writing—review and editing. Tiancheng Zhang: Methodology; data curation; writing—review and editing. Hongwu Lei: Resources; writing—review and editing.
ACKNOWLEDGMENTS
This study is supported by the Joint Funds of the National Natural Science Foundation of China (No. U2344226), which is gratefully acknowledged. We thank the reviewers and editors for the valuable comments and warm work on our manuscript. We also appreciate the contribution of the royalty-free content in Pixabay to the illustrations in the manuscript.
CONFLICT OF INTEREST STATEMENT
The authors declare no conflicts of interests.
APPENDIX
| Continental sedimentary basin | Population density (people/km2) | Wind power density at a height of 70 m (kW·h) | Annual total solar radiation (W/m2) | Capacity of CO2 storage (billion tons) | Potential capacity of driven water (billion tons) |
|---|---|---|---|---|---|
| Junggar Basin | 13.95 | 207.20 | 1588.60 | 4.436 | 0.202 |
| Tarim Basin | 13.95 | 207.20 | 1588.60 | 44.688 | 1.320 |
| Turfan Basin | 13.95 | 207.20 | 1588.60 | 1.542 | 0.051 |
| Ordos Basin | 108.47 | 182.74 | 1611.00 | 4.331 | 0.171 |
| Qaidam Basin | 8.50 | 197.22 | 1747.20 | 10.483 | 0.238 |
| Jiuquan Basin et al. | 54.65 | 205.52 | 1627.70 | 0.559 | 0.017 |
| Qinshui Basin et al. | 222.82 | 160.36 | 1536.00 | 0.113 | 0.004 |
| Hailaer Basin | 20.22 | 284.44 | 1571.60 | 0.670 | 0.039 |
| Songliao Basin | 162.17 | 233.69 | 1384.33 | 2.075 | 0.167 |
| Erlian Basin | 20.22 | 284.44 | 1571.60 | 1.147 | 0.071 |
| Bohai Bay Basin | 739.82 | 164.78 | 1496.85 | 6.552 | 0.220 |
| North Jiangsu Basin | 828.85 | 144.90 | 1458.50 | 1.691 | 0.059 |
| Nanxiang Basin | 618.39 | 135.91 | 1470.10 | 0.536 | 0.017 |
| Sichuan Basin | 170.26 | 127.47 | 1499.90 | 9.072 | 0.289 |
| Jianghan Basin | 310.22 | 102.33 | 1416.50 | 0.953 | 0.034 |
| Dongtinghu Basin | 310.22 | 102.33 | 1416.50 | 0.504 | 0.016 |
| Key technology | Engineering | Description | References |
|---|---|---|---|
| Carbon capture technology | Guohua Jinjie CCS project | An annual capture capacity of 150 000 tons of CO2 | Wang et al. (2023) |
| Shidongkou CCS project | An annual capture capacity of 120 000 tons of CO2 | Fan et al. (2020) | |
| CO2 storage in deep saline aquifers | Sleipner, Norway | The first CCS project in the global region to target saline aquifers started in 1996 | Jiang (2022) |
| Guohua Jinjie CCS project | CO2 capture by 150 000 tons per year | Leung et al. (2014); Sang et al. (2022) | |
| Geothermal energy extraction | Geothermal heat pumps in China | A total installed capacity of 20 000 MW | CG Survey (2018) |
| Yangbajing Geothermal Energy Power Station | The installed capacity reaches 25.18 MW | CG Survey (2018) | |
| Mining valuable minerals from the production water | — | The extraction stages complement one another to maximize element recovery, with a minimum recovery rate of 78% | Institute of Mineral Resources CAoGS, China (2013); Li et al. (2015) |
| Green hydrogen production with renewable energy resources | Zhangjiakou, Hebei Province, China | During the Winter Olympics, over 600 transportation support vehicles in Zhangjiakou all used zero-pollution and zero-emission hydrogen fuel cell vehicles | Ma (2022) |
| Global | The total installed capacity of planned green hydrogen projects worldwide has surpassed 250 GW | National Enery Administration (2018) | |
| Water desalination | Beijiang project in Tianjin province, China | A production capacity of 200 000 ton/day | China NOBoPsRo (2022) |
| Dongjiakou project in Shandong Province, China | A production capacity of 100 000 ton/day | China NOBoPsRo (2022) |
Biography
Bing Bai, is a professor of the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. He obtained his bachelor's degree from Central South University and his PhD degree from the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. His research interests involve carbon neutrality-related fields such as CO2 geological storage, deep geothermal resource development, geological energy storage, and bulk solid waste disposal.
附件【Deep Underground Science and Engineering - 2025 - Ci - A novel technological conception of integrated large‐scale CO2.pdf】