Advances, challenges, and perspectives for CCUS source-sink matching models under carbon neutrality target

With the widespread popularity of carbon neutrality, the decarbonization approach using carbon capture, utilization, and storage (CCUS) has grown from a low-carbon utilization technology to an indispensable technology for the entire global carbon-neutral technology system. As a primary method to support CCUS research, source-sink matching models face several new demand-oriented challenges. Comprehensive research and in-depth insights are needed to guide targeted capability upgrades. This review evaluates the advances, challenges, and perspectives of various CCUS source-sink matching models developed in the past 10 years. We provide an integrated conceptual framework from six key attributes relating to mitigation targets, carbon sources, carbon sinks, transportation networks, utilization, and integration (synergy). The results indicate that previous models have effectively deepened our understanding of the matching process by targeting various CCUS-related issues and provided a solid foundation for more robust models to be developed. Six perspectives are put forward to outline research and development prospects for future models, which may have meaningful effects for advancement under emerging carbon neutrality targets.


Introduction
Carbon capture, utilization, and storage (CCUS) refers to the technology of capturing and separating CO 2 from energy use, industrial production, and other sources, or even directly from the air, and then transporting the CO 2 to suitable sites for further utilization or geologic sequestration, ultimately achieving CO 2 emissions reduction. In addition to improving energy efficiency, adjusting the energy mix, and upgrading industrial structure, CCUS is widely recognized as playing an essential role in different mitigation scenarios of various integrated assessment models (IAMs) [1]. For example, the Intergovernmental Panel on Climate Change (IPCC) proposes that without CCUS participation, the total cost of climate mitigation toward 2°C futures will increase by an average of 138% [2]. A recent report proposed by the International Energy Agency (IEA) indicates that CCUS can provide a cumulative mitigation contribution of 15% in the 2070 Sustainable Development Scenario (SDS) [3].
The global community has been actively promoting cooperation to address climate change. So far, more than 130 countries have proposed respective climate mitigation goals associated with "net-zero emissions", "zerocarbon" or "carbon neutrality," of which about 30 economies have adopted relevant legislation or issued official policy announcements on carbon neutrality [4]. This builds toward a new momentum in global climate governance targeted at limiting the temperature increase below 2°C or even 1.5°C. Recently, nearly 200 participating countries adopted the Glasgow Climate Pact at the end of the 26th session of the Conference of the Parties (COP26) to the United Nations Framework Convention on Climate Change. They have reached a consensus on crucial actions towards low-emission energy systems, especially in incentivizing the energy sector to invest in CCUS solutions via calling upon the phase-out of unabated coal power. In addition, according to the China-US Joint Climate Declaration, CCUS has been listed as one of the most important cooperation directions for both sides. The prospect of future CCUS is a subject of global interest, whose implication and positioning should be deepened and expanded [5]. CCUS has undergone a new technological positioning upgrade, transforming from a low-carbon utilization technology of fossil energies to an indispensable technology for carbon neutrality [6][7][8]. Moreover, from the perspective of its mitigation contribution, CCUS extends from assisting decarbonization of a single energy sector to three core carbon-neutral development paths: promoting the construction of a zero-carbon energy system, driving the recreation of a zero-carbon production process, and guiding the way of a carbon-negative technology system. Source-sink matching is a major approach to effectively support CCUS research. A series of model developments and applied research on the CCUS source-sink matching process is crucial for a deep understanding of CCUS implementation under different external conditions, supporting core research issues in other fields, and improving the feasibility and economy of project engineering plans. Most of the existing research regarding CCUS source-sink matching models have emphasized the theoretical modelling of CO 2 capture, transportation, and storage, which is associated with the corresponding technological cost estimation at the project and regional levels. The CO 2 pipeline network design, which is typical of graph theory and can be solved by mixed integer linear programming (MILP) combined with a geographic information system (GIS), has infrastructure constructions that have been planned towards achieving the optimum cost-effective CCUS layout in various models. In addition, some models have exerted their effectiveness on frontiers, including more solid datasets of carbon sources and sinks that can solve a CCUS problem for an entire country like the United States or China, or even a continent like Europe [9][10][11][12][13][14].
Consequently, some important elements or limitations should be carefully considered, such as the industrywide carbon sources, the grid-level CO 2 injection rate capacity, the high-profit utilization option of enhanced oil recovery (EOR), the real geographic conditions, and the growing network in response to the changing mitigation demand over time [11][12][13][15][16][17]. Furthermore, the following two important aspects may have been overlooked: (i) an explicit mitigation target of CCUS driven by carbon neutrality, i.e., there is still a lack of indepth insights on how existing models can better connect demand-oriented source-sink matching to guide emerging capability targets; and (ii) the integration of models, such as the uncertainty of deployment led by technology competition, policies, public acceptance, risk assessment, negative-carbon technology system, and so on. Therefore, it is critical to optimally integrate all the above-mentioned properties to design large-scale CCUS implications.
On this basis, this review has investigated various typical CCUS source-sink matching models developed by different scholars in the past 10 years from the macroperspective of integrating multiple new capabilities concentrating on a clearer target orientation, especially with the widespread popularity of carbon neutrality. As highlighted in Fig. 1, this review proposed an integrated conceptual framework described by six key attributes: mitigation targets, carbon sources, carbon sinks (sequestration), transportation networks, utilization, and integration (synergy). These were used to explore the characteristics and evolution of different models. Based on the overall evaluation, future model development perspectives are proposed to improve the advancement and adaptability in the coming decade.
2 Evaluation of CCUS source-sink matching model based on the integrated conceptual framework

Model selection and evaluation system
The authors of the present study reviewed past research on CCUS source-sink matching models in the past 10 years with the keywords "CCS," "CCUS," and "sourcesink matching" using the SCIE Web of Science Database and identified 16 types of models. Each model was renamed in the common format "MX_NAME" according to the time sequence of its publication (i.e., M1-M16) and its original name. When a model was not assigned an original name in the published literature, its name can be determined by combining the associated source-sink matching approach, network characteristics, or the author's name with the addition of the study area. Thus, 16 models were renamed as follows: M1_SimCCS [18]; M2_CCSPD [19,20]; M3_SimCCS_TIME [21]; M4_InfraCCS_EUR [22]; M5_ChinaCCS_DSS [23,24]; M6_PNS [25]; M7_SCN_US [12,13]; M8_MARKAL_ IND [26]; M9_MILP_EUR (d'Amore et al., [9,10]); M10_MINLP_KOR [27]; M11_MILP_ESP [28]; M12_ ITEAM_CHN [14,29]; M13_SSM_WANG_CHN [30]; M14_SSM_FAN_CHN [11,15]; M15_C3IAM/GCOP (Wei et al., [17]); and M16_ChinaCCUS_DSS_2.0 [16] (Please refer to Supplementary Table 1 and following List of Abbreviations for the detailed information of the 16 types of CCUS source-sink matching models). Table 1 shows the evaluation system of the CCUS source-sink matching models, which could be used to comprehensively evaluate one specific model based on the insight of the comprehensive conceptual framework. Moreover, detailed evaluation criteria were proposed in this study, i.e., various levels of capabilities of each key attribute could be expressed with a score of 0-10. This facilitates the integration of the respective evaluation results of the six different attributes into one comprehensive conceptual framework.

Analysis of model evaluation results
The evaluation results of the six key attributes from 16 CCUS source-sink matching models are shown in Fig. 2, with associated analyses from the following three perspectives: comprehensive capability, data processing, and core matching approach.

Perspective 1
The previous models show evolutionary characteristics from simple features to the overall enhancement of comprehensive capabilities. Given the trend in the total scores, it was found that the average score of the six models (M1-M6) was 22.8 ± 9.1 and increased from 2008 to 2014. The average score of the ten models (M7-M16) was 32.7 ± 3.7 and increased from 2015 to 2021, indicating that not only the average score has increased by nearly ten points, but the standard deviation has been significantly reduced. CCUS technology has attracted an increasing amount of attention from researchers in recent years. New models developed based on existing models generally have stronger comprehensive capabilities, contributing to the increase in the total score.
In addition, the models have gradually developed from early simple features to current multi-functional integration. Some early classical models, such as SimCCS, which started from the original design concept of the source-sink matching model that committed to the design and optimization of pipeline networks, have made a significant contribution to exploring a prominent issue of CCUS technologyhow to make a linkage between different sources and sinks. It should be noted that, limited by the recognition of the role of CCUS technology in the overall mitigation technology system at that time, early models generally lacked consideration of some relevant attributes, especially the mitigation targets, Fig. 1 The integrated conceptual framework of CCUS source-sink matching utilization, and integration (synergy). People's comprehensive recognition of CCUS technology has deepened afterwards, driven by a series of increasingly clear mitigation targets and several CCUS demonstration projects. Model innovation toward a multi-attribute framework of CCUS source-sink matching can demonstrate diversified development for promoting investment decisions, spreading influence to different industries, and driving the exploration of emerging commercial modes.

Perspective 2
Reliable, precise, and broad input items continuously improve model data processing capabilities. The emergence of "big data" related high resolution and great collection capability has accelerated various types of well-designed and freely-accessible information, such as databases covering a range of carbon sources, carbon storages, cost estimates, and geographic information, resulting in a corresponding increase in the attribute scores of carbon sources and carbon sinks. For example, the currently developed models generally have a plant-level list of carbon sources for an entire industry at a national scale and have refined the coarse-mesh-based basins into highresolution grid scales, greatly improving model capability to estimate the mitigation potential accurately. In addition, the accuracy and precision of cost estimates throughout the whole CCUS process have been greatly improved, highlighting the disaggregation of fixed costs Table 1 The evaluation system of the CCUS source-sink matching model Criterion 4 (7-8 points) Criterion 5 (9-10 points)

Mitigation targets
No temporal characteristics; local or regional scale A few simple temporal characteristics (e.g., demand-driven); local or regional scale Explicit temporal characteristics (e.g., dynamic evolution); regional or national scale A variety of temporal characteristics (e.g., demand-driven, dynamic evolution, etc.); national or intercontinental scale A variety of temporal characteristics (e.g., demand-driven, dynamic evolution, technological competition, capital changes, etc.); intercontinental or global scale

Perspective 3
The core matching approach and logical architecture become more sophisticated and complete. The MILP is the core optimization and solving method adopted by most models, whereas the pinch analysis or graphic processing methods are adopted by a few of the models (Supplementary Table 1). The pinch analysis or graphic processing methods can be introduced to address the CCUS planning problem. The graphical tool known as the CCUS planning composite curve could provide valuable insights and performance targets to facilitate the CCUS retrofit planning stage. For example, a minimum viable duration of connectivity could be specified for CCUS to be worthwhile. However, geographical distances and pipeline costs between various sources and sinks are neglected. All sources and sinks are assumed to be in close geographical proximity due to inherent simplifications and lower expandability of pinch approaches. The MILP method generally blends a direction-setting objective function and several constraints that the model needs to follow, thereby simplifying the CCUS sourcesink matching process into a typical linear programming problem. Early models tend to take the minimum cost as the final optimization goal, while multiple optimization goals that consider the trade-off between mitigation potential and total cost have been included in recent models. In addition, there are increased constraint terms incorporated in MILP over time, reflecting the continuous improvement of model capacity to better describe the CO 2 flow process in line with CCUS technology development. For example, early models seldom use injection capabilities as a key constraint to explore the impact of the actual injection rate, and rarely consider the role of economies of scale in reducing the total cost by introducing a pipeline thickness. However, these important constraints have now been incorporated into most models to different degrees.

The evolutionary characteristics of different attributes 2.3.1 Mitigation targets
In the absence of a clear mitigation goal of carbon neutrality, the mitigation contribution of CCUS provided by IAMs in the IPCC or IEA assessment reports could generally be regarded as a top-down target for overall mitigation potential. However, this approach has an oversimplified assumption about the underlying technology, which can easily cause CCUS development to deviate from real situations, further leading to significant uncertainties about its contribution to carbon neutrality.
Other approaches with a bottom-up account of mitigation potential can make relatively reasonable inferences based on existing technology and industrial conditions but fail to accurately carry out future potential assessments because of the incomplete information of carbon sources or carbon storages. Some models developed in recent years can better integrate with global or national mitigation targets. For example, the M15_C3IAM/GCOP model [17] proposed a global source-sink matching layout from the perspective of limiting the global temperature rise by 2°C, targeting the final optimization goal that achieves the 92 Gt mitigation contribution of CCUS at a minimal cost. The M16_ChinaCCUS_DSS_ 2.0 model [16] assessed the effect of CCUS in the overall realization of the optimal route for China's carbon neutrality by connecting the CCUS source-sink matching model with the China TIMES model. This coupling could also provide solutions for studying the impact of technological competition on the layout of CCUS at a national scale. The dynamic evolution of mitigation targets, particularly for the feasibility and technological competitiveness of CCUS retrofit, is now being valued by more models.
In addition, a dynamic mitigation target represents the process of introducing CCUS infrastructure construction that is consistent with the changing mitigation targets and capital investments over time. For example, the M3_ SimCCS_TIME model [21] focused on multiple periods of matching processes by introducing a time parameter that could index all model variables in the MILP formula. In this way, the amount of CO 2 that was captured, transported, or stored in different periods varied, thus creating a powerful capability for a dynamic design of CCUS infrastructure over time. The dynamic mitigation targets have also been included in models such as M4_ InfraCCS_EUR [22], M5_ChinaCCS_DSS [23,24], and M10_MINLP_KOR [27] in different ways. Overall, more models are attempting to break free from the previous static models associated with a one-time investment of all CCUS infrastructures, as well as a time-invariant way of CO 2 management by setting mitigation targets from a dynamic perspective. This is important for optimizing investment decisions with dynamic economic parameters (such as for discount rate and carbon price).

Carbon sources and carbon sinks
The temporal and spatial scale of carbon sources covered by CCUS source-sink matching models has widened in recent years. For example, early models were intended for the traditional thermal power industry as the carbon sources, whereas new models have taken a broader adoption of plant-level emission sources of steel, cement, and chemical industries. Early models usually selected basins or reservoirs as the candidate storage sites with a relatively coarse spatial resolution, insufficient considerations of injection capacity constraints, and the exclusion of offshore sequestration, resulting in a non-equivalent matching between carbon sources and sinks on relevant spatial scales [31]. In general, models developed in recent years are dedicated to enriching databases, providing a considerable amount of information for carbon sources and sinks. For example, the M7_ SCN_US model [12,13] designed a cost-effective CCUS supply chain network in the United States, fully considering 3317 industry-wide sources and 2489 sinks (highresolution grid for saline aquifers and oil/gas fields). The M15_C3IAM/GCOP model [14] collected 4220 industry-wide carbon clusters and 794 sinks from 85 countries and regions and was committed to the global 92 Gt emission reduction goal contributed by CCUS. The M14_SSM_FAN_CHN model [11,15] developed an optimization model that does not consider cost constraints to explore the emission reduction potential of 607 existing coal-fired power plants in China, using a total of 3853 high-resolution grids for saline aquifers and oil fields as the carbon sinks. The marine geological survey database has rarely been fully utilized to identify potential carbon sinks, although some exploration has been conducted by the M9_MILP_EUR [9, 10] and M10_MINLP_KOR [27] models.

Transportation networks
Network optimization is an additional upgrade process for the preliminary results provided by CCUS sourcesink matching models, helps make the transportation network more efficient and practical. Innovations in network optimization are considered more difficult than other attributes because of the complex network structures. Thus, a series of assumptions are needed to simplify the optimization process and ensure the model is tractable, such as a straight-line connection between a single source and a single sink and using a given distance constraint. However, too simple assumptions may cause the networks to be unrealistic and inefficient. It is worth mentioning that the M1_SimCCS model [18] was still one of the few models that could satisfactorily describe topographical conditions on the network layout. Specifically, the SimCCS model has established a rasterized-weighted cost surface to estimate the real cost of pipeline construction crossing through each grid by using a set of topographical factors including terrain, topography, land use, intersections, land ownership, the right-of-way of pipelines, and population density. Furthermore, the SimCCS model could determine the location, length, and size of different trunk pipelines and branch pipelines based on a vector-based candidate network combined with a pre-optimization algorithm. Similarly, the M10_MINLP_KOR model [27] followed the concept of cost surfaces to obtain the minimum cost path and applied several subdivided penalty factors to show dramatic changes in geographic conditions in a more generic way using ArcGIS software. Generally, the cost surface processing method demonstrates a strong ability to characterize the impact of topographic conditions on the costs and the optimization of CCUS infrastructures. However, other issues, such as an understanding of the aggregation benefits from having trunk pipelines with different thicknesses, and the definition and identification of CCUS clusters or hubs, still lack effective solutions.

Utilization
To offset the cost associated with CO 2 capture, transportation, and storage, there is growing interest in finding profitable end-use opportunities for the captured CO 2 . In this perspective, some studies focus on the potential contribution of carbon capture and utilization (CCU), instead of trapping CO 2 underground as a terminal destination [13,32,33]. However, some studies have also found that CCU could, at most, be seen as supplementing carbon capture and storage (CCS) to a small extent, and it is highly improbable to allow long-term sequestration owing to the limited scale and rate of utilization. Thus, even if the CO 2 utilization is analysed separately in this review, it is still considered a commercially viable method under the entire CCUS chain towards CO 2 sequestration. Apart from some EOR approaches, most existing models have insufficiently considered the CO 2 utilization process. The associated chemical, biological, and mineralization utilization still cannot be identified in previous models. Some models can identify early development opportunities of CCUS hubs combined with intensive EOR utilization from the spatial distribution of source-sink matching. For example, the M16_ChinaC-CUS_DSS_2.0 model [16] explored the differentiated layout of CCUS for China's power system at low, medium, and high deployment levels, and concluded that the northern regions with abundant oil and coal reserves should push forward with the implementation of EOR and ECBM in practical applications. The M12_ITEAM_ CHN model [14,29] evaluated the synergetic benefits of providing large-scale mitigation potential and additional water supply through EWR utilization to cope with the huge water consumption of China's coal chemical industry. It was found that EWR could be conducted at a relatively low cost and mitigate 269 Mt CO 2 from the separation process, as well as generate 404 Mt groundwater for further desalination and utilization.

Integration (synergy)
Recently, more consideration has been given to the integration and synergy capabilities of various models. In addition to the continuous enhancement of layout optimization capabilities related to the evolution of transportation networks, some models can also comprehensively consider investment decisions or social risks. However, the complementation and synergy between CCUS (fossil-based energy), hydrogen energy, and other renewable energy sources within an integrated carbon management framework are less studied. The M9_MILP_EUR model [9,10] proposed a spatially explicit MILP approach for the economic optimization of the European CCUS supply chain and explicitly incorporated a social risk assessment module in the modelling framework, as well as risk mitigation measures in the pipeline design. The M11_MILP_ESP model [28] also adopted the MILP method as the matching framework to explore the conditions and infrastructures for the large-scale deployment of CCUS in Spain by 2040. More importantly, this model investigated the CO 2 emission threshold that drives necessary investment decisions, combining the overall layout of multiple regional networks with spatial characteristics of the Spanish peninsula. The M12_ITEAM_CHN model [17,29] investigated the relationship between the standardized cost and CO 2 emission reductions by integrating CCUS source-sink matching and investment decisions, finding that 22-58% of coal-fired power plants are costcompetitive with onshore wind power.
3 Prospects of CCUS source-sink matching model under the carbon neutrality target As discussed in this review, multiple types of CCUS source-sink matching models have been developed by researchers targeting various CCUS-related issues. These effectively deepen the understanding of CCUS technology to advance climate goals and lay a solid foundation for the subsequent development of more robust models. Future models should make more effort to provide complete solutions for scientific research, policy decision-making, and industrial service, as well as avoid new systemic problems arising under the future carbon neutrality goal. Therefore, the following six perspectives are put forward to provide possible research and development directions following the comprehensive conceptual framework in Fig. 1.

Precise mitigation potential of CCUS conformed to carbon neutrality
The highest priority should be to accurately assess the mitigation potential of CCUS technology driven by carbon neutrality. A total mitigation demand based on national objectives for carbon neutrality should be decomposed into specific targets for various industries, which could avoid the underestimation of the mitigation potential caused by referring to simple top-down assessment models. This also avoids overestimating the mitigation potential caused by aggregating carbon sources in a bottom-up manner. In the future, the decomposition of mitigation demand and the combination of top-down and bottom-up approaches can help develop the overall CCUS layout and corresponding mitigation potential by obtaining better supply-demand curve relationships.

More comprehensive, broader, and dynamical carbon sources
The carbon neutrality goal accelerates the inclusion of various carbon sources into a broader temporal and spatial framework. From a spatial perspective, future models should cover carbon sources across major industries, including power, steel, cement, and chemicals. Moreover, some dispersed sources related to CO 2 captured from biomass or waste organics could also be incorporated into the models. Compared with national or regional capabilities linked to their respective carbon neutrality pathways, extending the global capability of carbon sources can better serve the global mitigation targets. From a temporal perspective, it is valuable to identify the feasibility and technological competitiveness of CCUS technology by tracking the evolution of carbon sources until the realization of carbon neutrality. In addition to the dynamic processing models, coupling with IAMs can also make the matching results achieve an increased degree of foresight and predictability.

Multi-type, high-resolution, and multi-constrained carbon sinks
The storage sites required by future models show several characteristics. First, an understanding of the potential trapping and storage mechanisms is required to provide confidence in the high availability of multi-type CO 2 geological sequestration, including those based on the physical entrapment of deep saline aquifers, oil and gas reservoirs, and coal seams, or forming new carbonate minerals via the mineralization of CO 2 in basalt formation [34]. A recent study shows that the conversion of injected CO 2 to methane (CH 4 ) via microbial methanogenesis may be an important subsurface sink [35]. Second, the decomposition of current basins or reservoirs into high-resolution onshore and offshore storage sites through grid processing can effectively ensure spatial equivalence matching, and the inclusion of multiple constraints, such as storage potential, injection rate capacity, and storage security, will significantly improve the integrity and reliability of entire networks [31]. Third, a time and cost-efficient way of advancing CCUS is through the application of machine learning, which has been used for gauging the security and integrity of geological reservoirs. Several machine learning algorithms have been used to predict and monitor CO 2 leaking to ensure the safe and long-term storage of injected CO 2 and create surrogate models for optimizing the EOR process and uncertainty analysis. Applying machine learning in CCUS shows great potential in identifying links between data or results that are not readily identifiable, and it also provides alternative lower computing cost pathways [36].

Network optimization with a multi-factor trade-off
The design and optimization of transportation networks need trade-off economics, industrial clusters, pipeline hubs, and practical feasibilities to maximize benefits. The first is to improve the economic performance and the design feasibility of the network through the effective combination of global and local optimization, as well as trade-off mitigation potential and total cost. The second is to highlight the role of industrial clusters and pipeline hubs in infrastructure sharing, resource recycling, and industrial linkages, as well as introduce trunk pipelines to promote economies of scale [37]. The third is to consider the realistic factors to a reasonable degree. The topography, traffic, and socio-economic conditions impact pipeline construction costs and their optimal paths. Not considering these factors may cause an underestimation of the total cost, whereas over consideration may lead to operational and engineering redundancy. In addition, it has become an important optimization option to construct new pipelines alongside the existing natural gas pipeline network. Still, adjustments should be made according to the location of carbon sources and sinks. The fourth is to explore the feasibility of constructing cross-border and transregional transportation networks. The future large-scale implementation of CCUS requires global cooperation in fundraising and technology transfer to jointly solve the problem of source and sink mismatch.

New forms of CCUS industries based on the utilization process
The carbon neutrality goal puts forward requirements for the extension of new forms of CCUS industries and the full-chain integration based on the essential links of the utilization process. Future models need to compensate for the widespread lack of utilization. EOR has become the most economical utilization approach adopted by most models. However, considering that the total storage potential of oil fields is relatively limited, it is necessary to extract greater benefits by creating a green carbon supply chain under new forms of CCUS industries with important utilization approaches, including chemical, biological, and mineralization utilization.

Integration and synergy with the entire carbonneutral technology system
There will increasingly be a variety of possible application scenarios for CCUS technology, reflecting the importance of a comprehensive model to enhance integration and synergy with the entire carbon-neutral technology system. First, future models can play a critical role in decarbonizing traditional fossil energy systems and industrial processes under low-carbon scenarios, coordinating renewable energies under the zero-carbon scenario, and providing basic support for BECCS and DACCS under the negative-carbon scenario [38]. Second, more integration and synergy are needed in the research and production of CCUS technology, combined with the carbon trading market, incentive policies, and social investment and financing. Future models will better support investment decisions via accurate cost accounting throughout the full-chain process, especially combined with technological competition. Third, the integration of energy security, environmental impacts, and social risk assessments are helpful with overcoming relatively limited public acceptance. Public concerns need to be addressed, such as the assessment of CO 2 leakage risk during pipeline transportation or geological storage, as well as the excessive land occupation involved in BECCS. Proper consideration of these risks in future models can provide decision-makers and the public with more objective, fair, and effective decision-making information. Finally, the increase in model elements poses a challenge to the inclusiveness of the original system. Thus, it is necessary to have the capability to address those uncertainties inherent in planning CCUS networks for multi-decade timescales and those from external boundary conditions, including those such as changing policies/regulations, increased technology maturity, and environmental risk, to ensure the overall robustness and resilience of future models.

Conclusions
An integrated conceptual framework described by six key attributesmitigation targets, carbon sources, carbon sinks (sequestration), transportation networks, utilization, and integration (synergy)could be used to review the characteristics and evolution of different CCUS source-sink matching models. The findings indicate that most previous models could show evolutionary characteristics from simple features to the overall enhancement of comprehensive capabilities, especially at the greater data processing capabilities led by broad input items and a more complete matching approach, thereby effectively deepening our understanding of CCUS source-sink matching and laying a solid foundation for more robust models to be developed. Moreover, future model development perspectives are proposed to improve the advancement and adaptability in the coming decade. Further models are suggested to focus on a clearer target mitigation potential of CCUS conformed to carbon neutrality and integrate multiple new capabilities relating to carbon sources, carbon sinks, network optimization, utilization process, and integration with the entire carbon-neutral technology system.