Planning for the Reuse of Abandoned Mines—From the Perspective of Value Evaluation and Sustainable Development

Abstract

The reuse of abandoned mines is not a pure ecological project but a complex social public project. While it is unsustainable to reuse abandoned mines without ecological restoration, such restoration without comprehensive resource utilization will cause a serious waste of resources. Therefore, to reduce the contradiction between ecological restoration and resource utilization in the process of reusing abandoned mines, there is an urgent need to research the classification, grading development, and utilization evaluation index system of abandoned mine resources. Based on the concept of “energy, resource and functionalization” three-dimensional coordinated development and utilization, this paper analyzes the value connotation of abandoned mine reuse and constructs an evaluation index system for the reuse value of abandoned mine resources, including resource conditions, ecological conditions, and development conditions. Secondly, according to the priority needs of abandoned mine reuse, the minimum factor method is used to design a development sequence that can take into account the reuse of abandoned mines and the coordinated development of the ecological environment and the region. On this basis, the value of abandoned mine reuse is divided into four grades and three development stages. Taking the Jingxi Mining Area as an example, corresponding development and utilization suggestions are proposed, and the guiding value of the evaluation index system in assessing resource potential and optimizing of development paths is verified. The research results can provide scientific decision support for planning the development and utilization of abandoned mine resources. They also have practical significance for constructing green development technology standards and promoting ecological restoration and industrial transformation and upgrading in mining areas.

1. Introduction

Due to reasons related to resource depletion, unsafe mining, and policy, the number of abandoned coal mines in China has increased dramatically, especially of abandoned underground coal [1]. According to incomplete statistics, 7100 coal mines were eliminated in China during the 12th Five-Year Plan period, and by 2020, there were fewer than 4000 coal mines with a productive capacity in China. The number of abandoned mines in China is estimated to reach 15,000 by 2030 [2]. Faced with the emergence of a large number of abandoned mines, the coal industry must address the following problems: abandoned mine resources need to be reused, repairing seriously degraded ecosystems, and reemploying many miners. This is true for all coal-producing countries, but China has the most serious problems. Taking Shanxi as an example, the coal and coalbed methane resources left in abandoned mines account for 20.59% and 50% of the whole country, respectively, and the mined-out area of the whole province is nearly 5000 km² (accounting for about 3% of the whole province’s land area), of which 2052 km² (accounting for 41% of the mined-out area) has development value; furthermore, the affected population is as large as 2.3 million [3]. Abandoned mine resources are abundant in China, which have good potential for resource conservation, recycling, and substitution. Every closed mine has its own serviceability and strategy for rebirth. Recycling abandoned mines provides the following public benefits: The first benefit is negating or reducing the safety risks and environmental impacts of post-mining areas. The second advantage is turning waste areas into those with the potential for sustainable development of resource-exhausted cities [4]. With the decrease in resource abundance, economic transition and changes in development mode have become an important and inevitable subject for resource-dependent cities. The most important motivation is the considerable resources derived from these closed mines. These facts indicate the huge potential surrounding abandoned mine utilization and the significance of incorporating sustainable ecological balance into mine closure plans.

The reuse of abandoned mines should be carried out based on ecological restoration. However, the reuse of abandoned mines is not a pure ecological project, but a complex social public project. Therefore, the core problem of abandoned mine reuse is coordinating and uniting ecological restoration and abandoned mine resources reuse. With differences in resource endowment, environmental and social needs will differ, among other factors, leading to significant differences in the reuse of abandoned mines. In recent years, the reuse of abandoned mines has become a research hotspot in major coal-producing countries. Abandoned mines have been reutilized at home and abroad, but there are more foreign cases. At present, the worldwide utilization of closed mines is presently dominated by demonstration projects. The choice of utilization method is mainly based on subjective judgment due to the lack of a scientific decision-making framework. Indeed, a unified classification standard for abandoned mine resources has not been formed, and there is still uncertainty regarding reuse project site selection, reuse depth, and reuse mode. Therefore, to ensure a stage and goal-oriented abandoned mine re-planning process, we must study the basic problem of abandoned mine reuse values.

By reviewing and analyzing previous studies, we found that the research on the reuse planning of abandoned mines mainly presents the following characteristics: 1. At present, the overall research on abandoned mine reuse is insufficient. Rather, most research has focused on the reuse of individual resource elements in abandoned mines and their potential evaluation, such as mining wastelands [5], underground space of coal mines [6], mine water [7], coalbed methane [8], industrial tourism [9], and so on. Failure to plan and use resources leads to a waste of resources and a lack of coordination between systems. 2. The existing research often directly determines a reuse mode for abandoned mines or some of their resources [10]. Due to a lack of reuse value analysis, the rationality of reuse mode selection may be questionable. 3. A mature and complete evaluation system of reuse value has not been established. Scholars at home and abroad have focused more on the ecological value of abandoned mine reuse, rather than the social and economic value [11]. The one-sided reuse of abandoned mines causes a deviation in the comprehensive benefits, potentially even project failure. Although some studies have considered the ecological restoration of abandoned mining areas and the coordinated development of economy and society, they do not consider the development and utilization of abandoned mine resources as regional economic and social development. No systematic study has identified or comprehensively evaluated the reuse value of abandoned mines. The one-sided reuse of abandoned mines is also the reason why demonstration projects cannot be fully promoted. Therefore, it is of great significance to construct an abandoned mine reuse value evaluation index system and carry out abandoned mine reuse planning from the perspective of value evaluation.

2. Materials and Methods

2.1. Reuse Value of Abandoned Mines

From the perspective of the driving forces and benefits of reuse, the reuse value of abandoned mines includes three aspects: economic value, social value, and ecological value (as shown in Figure 1). Economic value refers to the comparison between various inputs and outputs in the resource development and utilization process. When inputs are greater than outputs, the economic value is negative, and vice versa. The social value of reusing abandoned mines lies in the complete transformation from “eliminating negative externalities” to “creating positive externalities”. It is a comprehensive social project that integrates safety guarantees, economic revitalization, cultural inheritance, and technological innovation. The greater the satisfaction degree, the greater the social benefits, and vice versa. Ecological value is the impact of resource development and utilization activities on the natural ecosystem. When the activities improve the ecosystem, the ecological benefit is positive; otherwise, it is negative. Ecological value forms the basis of economic and social values. A development model with negative ecological value will fall short due to ecosystem degradation. On the contrary, restoring the ecological environment will support social and economic development, thus forming a virtuous circle [12]. The analysis of driving factors indicates that restoring and maintaining natural ecology, the harmonious coexistence of society, and sustainable economic development are the motivations and goals of reusing abandoned mine resources. The priority order of the reuse value of abandoned mines must be analyzed with respect to a single mine or a small-scale mining area. With the tightening of resource and environmental constraints and the continuous advancement of de-capacity, identifying the relationship between abandoned mine ecological restoration and resource reuse addresses the current environmental governance of abandoned mining areas but also addresses the sustainability of their transformation and development. According to the guidance on establishing a responsibility mechanism for mine environment management and ecological environment restoration carrying out pilot work on reclaiming and utilizing industrial and mining wastelands, technically specifying mine ecological environment protection and restoration management (for trial purposes), and referring to the theory of ecological service value, the reuse of abandoned mines should focused on ecological restoration management; that is, it should highlight the priority of the ecological service value of abandoned mine reuse. To clarify the relationship between abandoned mine ecological construction and reuse, the essence of “reuse value of abandoned mines” is to evaluate the value of transforming and developing a single mine or mining area under the comprehensive effects of resource endowment, ecological bearing, and development conditions of abandoned mines, giving priority to ecological value. From the perspective of comprehensively evaluating ecological service value, this study determines the reuse value of abandoned mines and considers problems such as dividing the reuse stages of abandoned mines and project site selection.

2.2. Construction of an Evaluation System for Abandoned Mine Reuse Value

An operable evaluation index system for the reuse value of abandoned mines cannot include all influencing factors. According to the above analysis of abandoned mine reuse values, the factors affecting the reuse value of abandoned mines were mainly divided into three aspects: namely, resource conditions, ecological conditions, and development conditions. Following the systematic, hierarchical, and operable principles of system construction, a reuse value evaluation index system was established, including four levels from three aspects (as shown in Figure 2). The sub-indicators are presented in

Table 1. Evaluation indicators and criteria for resource utilization classification of abandoned mines.

Factor Layer		Indicator Layer	Classification Standard			Reference
			Excellent	Medium	Poor
Energization utilization $E$	Coal $E_1$	Remaining reserves $E_1^1$	>3.5 million tons	Minimum economic resources	<Minimum economic resources	[14]
		Buried depth $E_1^2$	300–2000 m	100–300 m	<100 m/>2000 m
		Coal quality characteristics $E_1^3$	Lignite	Sub-bituminous coal	High-rank coal
		Thickness $E_1^4$	>1.5 m	0.5–1.5 m	<0.5 m
	Coalbed methane $E_2$	Coalbed methane abundance $E_2^1$	Gas content > 20 m3/t, resource abundance > 3 × 108 m3/km2	The gas content is 8~20 m3/t, and the resource abundance is 1 × 108–3 × 108 m3/km2	Gas content < 8 m3/t; resource abundance < 1 × 108/km2	Ref. [15], Coalbed Methane Resources/Reserves Specification (DZ/T 0216-2002) [16]
		Storage condition $E_2^2$	The coal body structure is complete and simple, the pressure coefficient of coal reservoir is ≥1, the ratio of temporary reservoir is ≥0.8, the permeability of coal seam is ≥5 × 10−3 μm2, and the adsorption time is ≤1 day	The coal reservoir pressure coefficient is 0.4–1, the temporary reservoir ratio is 0.2–0.8, the permeability of the coal seam is 0.1–5 × 10−3 μm2, and the adsorption time is 1–10 days	The coal reservoir pressure coefficient is less than 0.4, the temporary reservoir ratio is less than 0.2, the permeability of the coal seam is less than 0.1 × 10−3 μm2, and the adsorption time is more than 10 days
Resource utilization $R$	Mine water $R_1$	Mine water inflow $R_1^1$	>2100 m3/h (>1200 in Northwest China)	180–2100 (NW 90–1200)	≤180 (≤90 in Northwest China)	(AQ20612018) [17]
		Mine water quality $R_1^2$	Clean mine water	Mine water containing suspended solids	Mine water with high salinity, acidity, or special pollution	Classification of Coal Mine Water (GB/T 19223-2015) [18]
	Geothermal $R_2$	Geothermal scale $R_2^1$	Ensure that the electric energy of high-temperature geothermal fields with a mining life of 30 years is more than 50 MWe, and that of medium- and low-temperature geothermal fields with a mining life of 100 years is more than 50 MWe	10~50 MWe for high-temperature geothermal fields and 10~50 MWe for medium- and low-temperature geothermal fields with a mining life of 30 years and 100 years, respectively	Ensure that the electric energy of high-temperature geothermal field with 30 years of mining life is less than 10 MWe, and that the electric energy of medium- and low-temperature geothermal field with 100 years of mining life is less than 10 MWe	Code for Geological Exploration of Geothermal Resources (GB11615-89) [19]
		Well completion depth $R_2^2$	<1000 m	1000~3000 m	>3000 m,	Evaluation standard of geothermal resources development
Functional utilization $F$	Land $F_1$	Occupied land area $F_1^1$	Occupied area of a large mine	Occupied area of a medium-sized mine	Occupied area of a small mine	Coal Mine Design Specifications (GB50215-2015) [20]
		Degree of land destruction $F_1^2$	Mild damage	Moderate damage	Severe damage	Technical Specifica-tions for Assessment of Ecological Environment (HJ/T192-2015) [21]
	Underground space $F_2$	Underground space capacity $F_2^1$	>600,000 m3	300,000–600,000 m3	<300,000 m3	[6]
		Stability of surrounding rock $F_2^2$	The rock is hard, the structure is complete, and the geological structure is simple	The rock is relatively hard, the structure is relatively complete, and the geological structure is moderately complex	The rock is broken, the structure is incomplete, or the rock and soil mass is incomplete, and the geological structure is complex	[6]
	Tourism resources $F_3$	Resource influence $F_3^1$	Suitable for visiting more than 300 days per year, or suitable for all tourists to use and participate in	Suitable for visiting more than 150 days per year, or suitable for 60% of tourists to use and participate	Suitable for visiting more than 100 days per year, or suitable for 40% of tourists to use and participate	(GB/T18972-2003) [22]
		Value of resource elements $F_3^2$	Ornamental recreation value, cultural value, and peculiarity are high	The ornamental recreation value, cultural value, and peculiarity are high	Ornamental recreation value, cultural value, and peculiarity are average

,

Table 2. Evaluation indicators and criteria for ecological conditions.

Factor Layer	Indicator Layer	Classification Standard			Reference
		Excellent	Medium	Poor
Ecological pollution situation $EP$	Degree of land destruction $E{P}_1$	Mild damage	Moderate damage	Severe damage	Technical Specifications for Assessment of Ecological Environment (HJ/T192-2015)
	Soil pollution degree $E{P}_2$	I	II	III	Soil Environmental Quality Standard (GB15618-2008)
	Aquifer destruction $E{P}_3$	<50 m	50–200 m	>200 m	[23]
	Water-quality grade $E{P}_4$	I, II	III	IV, V	(DZT0290-2015) Groundwater Quality Standard [24]
	Vegetation coverage $E{P}_5$	>6%	3–6%	<3%	Code for Compilation of Mine Ecological Environment Protection and Restoration Scheme (Planning) (Trial) (HJ 652-2013) [25]
Ecological management $EM$	Governance investment ratio $E{M}_1$	>0.6%	0.4–0.6%	<0.4%	[26]
	Treatment area ratio $E{M}_2$	>6%	4–6%	<4%	[3]
	Utilization rate of three wastes $E{M}_3$	>60%	20–60%	<20%	[26]

and

Table 3. Evaluation indicators and criteria for development condition indexes.

Factor Layer	Indicator Layer	Classification Standard			Reference
		Excellent	Medium	Poor
Internal development conditions $ID$	Distance from residential area $I{D}_1$	<2000 m	2000–2500 m	>2500 m	[27]
	Well size $I{D}_2$	≥900,000 t/a	600,000–900,000 t/a	≤600,000 t/a	[6]
	Security risk level $I{D}_3$	Low	Medium	High	[6]
	Mine location $I{D}_4$	Urban or suburban type	Outer suburb type	Remote type	[12]
	Accessibility of mining area $I{D}_5$	The transportation convenience inside and outside the region is high	High accessibility within the region	Low accessibility within the region	[6,23]
	Employed population $I{D}_6$	≥2000	1000–2000	≤1000	[12,23]
External development conditions $ED$	Location condition $E{D}_1$	East	Middle	West and Northeast	[6]
	City hierarchy $E{D}_2$	One, two, three lines	Four lines	Four lines	[26]
	Urban population size $E{D}_3$	≥3 million	100–300 million	<1 million	Notice on Adjusting the Standard of City Scale Division
	Planning and policy $E{D}_4$	National priority planning has been supported by relevant policies	City (district)-level development planning is planning the utilization policy of abandoned mines	Other district- and town-level development plans are seriously lacking in development policies	[15]

. Considering the obvious differences in the dimensions of each index in the evaluation system, the selection and quantification standards and individual indices could not be unified easily. Therefore, grade evaluation was selected for the unified quantification of indices. The resource conditions, ecological conditions, and development conditions were classified into three categories: namely, excellent, medium, and poor. The classification of the energy index and grade threshold mainly referred to relevant data in national industry planning and the published literature. It is important to note that the classification of some indicators was based on national authoritative standards. Taking soil pollution degree indicators as an example, the judgment process was as follows: the measured concentrations of heavy metals in our soil samples were operationalized by comparing them with the limit values stipulated in the GB15618-2008 standard [13]. Specifically, for agricultural land use (Grade II), the standard defines thresholds for elements including cadmium (0.3 mg/kg) and mercury (0.5 mg/kg). The samples were then classified (e.g., “Excellent”, “Medium”, “Poor”) based on the threshold ranges their values fell into. For the indicators that could not be quantified, the text description was used to classify them.

2.2.1. Abandoned Mine Resource Conditions

By identifying the size and distribution of abandoned mine resources, we can accurately evaluate the endowment value of resources, determine the developmental feasibility, and avoid the loss caused by blindly developing single mines. Considering the variety of abandoned mine resources and lack of classification standards, in this paper, abandoned mine resources are divided into three categories (see Table 1) according to their utilization: energization utilization, resource utilization, and functional utilization. As listed in Table 1, energy utilization includes underground gasification of surplus coal and extraction and utilization of coalbed methane; resource utilization includes mine water and geothermal energy utilization; and functional utilization includes the development and utilization of land resources, underground space resources, and tourism resources. Referring to existing international and national standards, combined with abandoned coal mine characteristics, the resource value of abandoned coal mines was measured from two dimensions: “quantity” and “quality”. It should be noted that the reuse mode must be clarified before identifying resource characteristics. For example, the surplus coal utilization mode in abandoned mines referred to in this paper is underground gasification; therefore, the evaluation index of coal resources was analyzed with reference to the resource conditions in underground gasification site selection.

2.2.2. Ecological Conditions

Ecological condition indicators reflect the direct and indirect impacts of mining activities on the regional environment. The indicators measuring ecological conditions were mainly selected based on two aspects: damage and restoration of the ecological environment (see Table 2). The degree of damage to the ecological environment reflects the present situation of regional ecological damage. Ecological governance indicators reflect the regional investment in ecological environment governance. From the perspective of reuse suitability, if the ecological damage is lighter and the treatment is better in an area, then it is more suitable for project development. From the perspective of ecological restoration, the more serious the ecological damage and the worse the governance, the higher the ecological value of reuse.

2.2.3. Development Conditions

Development conditions were divided into internal development conditions and external development conditions according to the size of the affected areas (as shown in Table 3). The evaluation of internal development conditions mainly considered the urgency of mine reuse demand and the feasibility of reuse conditions. External conditions determine the competitiveness and sustainable development of reuse. From a suitability perspective, the better the external development conditions, the higher the economic value of an abandoned mine reuse project. From a value perspective, if regional economic and social development is poor, more abandoned mines need to be reused to achieve regional balanced development. Therefore, the worse the regional economic conditions, the higher the social value of reuse.

2.3. Index Integration Method

Some studies that analyze the potential and carrying capacity of resources have used a simple weighted summation method to integrate impact factors and evaluation indicators, which indicates that there is mutual compensation or substitution among the impact factors. However, some indices in the evaluation of abandoned mine reuse value, such as resource endowment conditions and mine location, are generally absolute limit values, making it difficult to compensate for them. It is also difficult to characterize the internal scientific logic among indices using the weighted sum rule. When the contribution of each participating factor to the reuse value and the relative and absolute restrictions of each influencing factor are unknown, the weighting method should not be used to weigh the index because it is too subjective. Therefore, the comprehensive index method is not suitable for evaluating the reuse value of abandoned mines. In this paper, the minimum factor method, that is, the short board effect, is selected for index integration, which fully emphasizes the effect of key indicators. The core idea of the minimum factor method is the fact that the overall level of a system is not determined by its advantageous factors but is limited by its weakest and lowest-level key factor. Its uniqueness lies in its “cask effect” logic, emphasizing the importance of the weak points. The minimum factor method has many advantages over other methods, such as identifying risks and simplifying decisions. The expression of the minimum factor method is shown in Formula (1)

$$Y=\min (Y_i)$$

(1)

The minimum factor method is an integration approach based on Liebig’s Law of the Minimum, which posits that system performance is constrained by the most limiting factor. The method is applied through the following step-wise procedure:

Step 1: Indicator Selection and Normalization.

A set of n key indicators (I₁, I₂, ..., I_n) relevant to the system’s evaluation is selected.

Step 2: Identification of the Minimum Factor.

The normalized values of all indicators are scanned to identify the single smallest value, which represents the most limiting factor constraining the entire system.

Minimum Factor = min(I₁, I₂, …, I_n)

where the minimum grade of each index grade in the index layer is the final grade. The integration of indicators in Table 1, Table 2, and Table 3 is expressed by the following Formulas (2)–(4):

$$\left\{\begin{array}{l}E=\min \left(E_1,E_2\right)=(E_1^1\cap E_1^2\cap E_1^3\cap E_1^4)\cap (E_2^1\cap E_2^2)\\ R=\min \left(R_1,R_2\right)=(R_1^1\cap R_1^2)\cap (R_2^1\cap E_2^2)\\ F=\min \left(F_1,F_2,F_3\right)=(F_1^1\cap F_1^2)\cap (F_2^1\cap F_2^2)\cap (F_3^1\cap F_3^2)\end{array}\right.$$

(2)

$$\left\{\begin{array}{l}EP=\min \left(E{P}_1,E{P}_2,E{P}_3,E{P}_4,E{P}_5\right)=E{P}_1\cap E{P}_2\cap E{P}_3\cap E{P}_4\cap E{P}_5\\ EM=\min \left(E{M}_1,E{M}_2,E{M}_3\right)=E{M}_1\cap E{M}_2\cap E{M}_3\end{array}\right.$$

(3)

$$\left\{\begin{array}{l}ID=\min \left(I{D}_1,I{D}_2,I{D}_3,I{D}_4,I{D}_5,I{D}_6\right)=I{D}_1\cap I{D}_2\cap I{D}_3\cap I{D}_4\cap I{D}_5\cap I{D}_6\\ ED=\min \left(E{D}_1,E{D}_2,E{D}_3,E{D}_4\right)=E{D}_1\cap E{D}_2\cap E{D}_3\cap E{D}_4\end{array}\right.$$

(4)

According to Formula (2), the “three-oriented” resources of abandoned mines can be classified into three categories: namely, high-quality resources, individual high-quality resources, and general resources (as detailed in

Table 4. Classification criteria of development condition indexes.

Category	$\mathit{E}$	$\mathit{R}$	$\mathit{F}$
Quality resources	$E_1$ and $E_2$ are both excellent	$R_1$ and $R_2$ are both excellent	$F_1$, $F_2$, and $F_3$ are excellent
Individual quality resources	$E_1$ or $E_2$ is excellent	$R_1$ Or $R_2$ is excellent	$F_1$, $F_2$, or $F_3$ is excellent
General resources	$E_1$ and $E_2$ are not excellent	$R_1$ and $R_2$ are not excellent	Neither $F_1$, $F_2$, or $F_3$ is excellent

).

2.4. Integrated Evaluation of Abandoned Mine Reuse Value

When reusing abandoned mines, comprehensive high-quality resources should be given priority first, and specific resources with outstanding advantages should also be considered. This forms the “resource sequence”. According to the ecological service value theory of abandoned mine reuse, reuse should reflect ecological value priority, considering social and economic values. In this paper, we propose the “value sequence” of ecological value priority, followed by social value and economic value. It should be noted that value evaluation is different from suitability evaluation (as shown in the suitability column in

Table 5. Reuse value grade of abandoned mines.

No.	Value Sequence	Value Embodiment	Resource Conditions			Ecological Conditions		Development Conditions		Development Phase	Suitability	Region
			Quality	Individual Quality	General	$\mathit{E}\mathit{P}$	$\mathit{E}\mathit{M}$	$\mathit{I}\mathit{D}$	$\mathit{E}\mathit{D}$
1	Highest	Comprehensive value	✔			●	●	●	●	Primary	Inappropriate	Large mines in western and northern China
2	Higher	Ecological value + economic value	✔			●	●	●	●	Primary	Inappropriate	Large mines in central and eastern China
3	Higher	Economic value + social value	✔			●	●	●	●	Intermediate	General suitability	Large mine in central China
4	Higher	Economic value	✔			●	●	●	●	Advanced	Optimal	Large mines in eastern China
5	High	Comprehensive value		✔		●	●	●	●	Primary	Inappropriate	Large and medium-sized mines in western and northern China
6	High	Ecological value + economic value		✔		●	●	●	●	Primary	Inappropriate	Large and medium-sized mines in central and eastern China
7	High	Economic value + social value		✔		●	●	●	●	Intermediate	General suitability	Large and medium-sized mines in central China
8	High	Economic value		✔		●	●	●	●	Advanced	More suitable	Large and medium-sized mines in eastern China
9	General	Average value			✔	●/●	●/●	●/●	●/●	Primary	Inappropriate	Part of the southern mine

Grade: excellent ●, medium ●, poor ●.

). Suitability evaluation aims to obtain the best economy of a project; that is, prioritization of economic value. However, we aim to determine the comprehensive value of reuse, not only the economic value. For example, the higher the degree of ecological damage, the worse the governance, and the more backward the regional development conditions, the higher the ecological and social benefits, and the higher the reuse value level. According to the resource order and value order proposed in this paper, an integrated evaluation system for determining the reuse value grade of abandoned mine resources is developed (as shown in Table 5) and applied to the Beijing West Mining Area (

Table 6. Evaluation results of resource conditions in the Beijing West Mining Area.

Factor Layer	Indicator Layer	Basic Data	Quality	Quantity	Results	Category
Energy conversion	Coal	About 238 million tons/anthracite	poor	excellent	poor	General resources
	Coalbed methane	Low gas mine	poor	poor	poor
Resource utilization	Mine water	3 m3/min, mine water containing suspended solids	poor	poor	poor	Individual quality resources
	Geothermal	More than 160 wells have been completed	excellent	excellent	excellent
Functionalization	Land	Large mine, the degree of land damage is light	excellent	excellent	excellent	Quality resources
	Underground space	The roof and floor are hard rock, and the underground space is stable/71,000 m3	excellent	excellent	excellent
	Tourism	It is suitable for all tourists to use and participate and has high value	excellent	excellent	excellent

,

Table 7. Evaluation results of ecological conditions in the Beijing West Mining Area.

Factor Layer	Indicator Layer	Basic Data	Rank	Results
Ecological pollution situation	Degree of land destruction	mild	excellent	excellent
	Soil pollution degree	I	excellent
	Aquifer destruction	<50 m (obtained by the literature investigation)	excellent
	Water-quality grade	II	excellent
	Vegetation coverage	60%	excellent
Ecological management	Governance investment ratio	0.79%	excellent	excellent
	Treatment area ratio	14%	excellent
	Utilization rate of three wastes	75%	excellent

and

Table 8. Evaluation results of development conditions in the Beijing West Mining Area.

Factor Layer	Indicator Layer	Basic Data	Rank	Results
Internal conditions	Distance from residential area	1500 m	excellent	excellent
	Well type	All of them are large mines (≥1 million t/a)	excellent
	Security risk level	low	excellent
	Mine location	46 Km from the city center	excellent
	Accessibility of mining area	The roads are connected and the transportation is convenient	excellent
	Employed population	10,385 people	excellent
External conditions	Location	East	excellent	excellent
	City hierarchy	First-tier cities		excellent
	Urban population size	21.54 million people		excellent
	Planning and policy	National priority development	excellent

). The Beijing West Mining Area was selected as the case study object because of its natural historical landscapes and coal mining cultural heritage. It has a superior geographical location, a developed transportation network, and complete functions of a modern mining area. Due to the relatively short closure period of the entire mining area, the data related to its resources, ecology, and development conditions are relatively complete. The main reason for selecting this area was that the reuse plan for its remaining resources was incorporated into the urban development plan, as shown in

Table 9. Reutilization projects of closed mines in the Beijing West Mining Area.

Resources	Reuse Patterns	Project Progress	Development Body
Land	Ecological restoration	Under planning	Government
Land	Real estate	Under planning	Jingmei GROUP
Land and roadway	Big data storage base	Under planning	ingmei
Land	National mountain park	Under planning	Government
Land	Nursing home	Completed the plans	Jingmei GROUP and Longfor GROUP
Anthropogenic wastes	Industrial tourism	Under planning	Jingmei GROUP
Roadways and land	Skiing industrial park	Under planning	Jingmei GROUP

. The planning results can provide sufficient evidence for the credibility of this study’s conclusion. According to the classification of abandoned mine reuse value, the reuse stages are divided into three stages: primary utilization, intermediate utilization, and advanced utilization. See the Discussion Section for specific analyses.

3. Results and Discussion

3.1. Division of Abandoned Mine Reuse Value

Combined with the dual utilization criteria of resource order and value order, the reuse value grades of abandoned mines have nine combinations. These combinations are divided into four categories, from high to low, and the value of each category is described.

(1) As shown in Table 5, the condition corresponding to the highest redevelopment value of abandoned mines is the presence of comprehensive high-quality resources, high ecological damage, a poor restoration effect, and a severe lack of external development conditions. These types of coal mines are mainly located in the western and northern parts of China due to their large production volume (with the coal output of Shanxi, Shaanxi, Inner Mongolia, and Xinjiang accounting for 81.3% of the national total) and the fragile ecological carrying capacity, especially the severe shortage of per capita water resources (only 20% of the national average). Due to location and economic development, its external development conditions are poor. The effect of mine closure on the natural economic and social systems will be the strongest endogenous demand in the process of regional transformation and development. Compared with other regions, the ecological and social benefits of mine reuse are obvious. Considering the priority order of abandoned mine reuse value, this type of abandoned mine has great ecological and social value compared with other abandoned mines. Ecological restoration should be considered first when reusing this kind of abandoned mine, accounting for social and economic benefit, such as using abandoned mines to build underground reservoirs, ecological development (including new energy sources, such as solar energy) and industrial tourism. Gu Dazhao’s model of transforming abandoned mines into underground reservoirs was verified in the western mining areas of China and achieved good ecological benefits [28].

(2) Ranking 2–4 indicates a high grade of reuse value, which mainly refers to the abandoned large-scale mines with a long coal mining time, high population density, and weak ecological carrying capacity in the central and eastern regions. According to the 13th Five-Year Plan of Coal, the abandoned mines in the central and eastern parts of China will be closed quickly. The closure rate of the eastern mines is estimated to reach 70% in the next 10 years. Therefore, these areas will have many abandoned mines that need to be reused and developed. Integrating the development of these abandoned mine resources into social and economic development is expected to address issues, such as declining social, economic, and ecological conditions in mining areas, from the perspective of suitability and demonstration project selections (mainly considering economy).

The fourth type of abandoned mine has good resource endowment conditions, superior location conditions, strong demand for economic and social development, and excellent external development conditions. Therefore, it is necessary to prioritize these abandoned mines for demonstration projects and promote their role in improving the ecological system and meeting the sustainable development of the social economy. The Beijing West Mining Area, a typical suburban abandoned mining site, was used as an example to illustrate how the fourth type of abandoned mine was analyzed in the demonstration project. Using the basic data collected from the abandoned mines in the Beijing West Mining Area as presented in Table 6, Table 7 and Table 8, the final evaluation results of the mining area in terms of resource conditions, ecological conditions, development conditions, and each of the three-level indicators were obtained according to the classification standards in Table 1, Table 2 and Table 3. The surplus resources of the abandoned mines in the Beijing West Mining Area belong to general resources in terms of energy utilization, individual high-quality resources (geothermal) in terms of resource utilization, and “compound” high-quality resources, in terms of functional utilization (land, underground space, and tourism) (as shown in Table 6). Therefore, the resource reuse of abandoned mines in the Beijing West Mining Area must be functional utilization and geothermal energy development. Based on the ecological and development conditions in the Beijing West Mining Area, it is excellent in ecological pollution, treatment, and internal and external development conditions (see Table 7 and Table 8) [29]. Therefore, the reuse suitability of abandoned mines in this area was the highest. Based on the functional orientation of an “ecological conservation area”, the region has started ecological restoration and industrial transformation in a comprehensive manner. The Beijing West Mining Area is part of an ecological conservation area and has many ecological advantages. Many mining relics from the closure of coal mines can be used as tourism resources. The advantages of the Beijing Mining Area include external development conditions, such as location and economy, and a development mode based on eco-industrial parks and integrating various utilization modes (as shown in Table 9).

(3) Ranking 5–8 is a higher grade of reuse value, and this kind of abandoned mine has some high-quality resources. The types and quantities of resources should be determined before a mine is shut down. Only when the resource endowment reaches a certain scale can it be considered for development. Therefore, resource factors should be considered in each utilization model. In addition, market demand also needs to be considered before development. Generally speaking, the feasibility of development only exists when the profit is higher than the investment. Therefore, from the perspective of resource conservation, abandoned mines with some high-quality resources should be reused first. The reuse value of some abandoned mines in the south, northeast, and parts of the middle is limited because of small well types and complex geological conditions. Therefore, this kind of abandoned mine should be properly utilized according to the actual situation. For other abandoned mines, reuse treatment is not currently performed, and primary utilization such as ecological restoration is conducted.

(4) The most important objective of this paper is to provide a reference for selecting abandoned mine reuse projects and demonstration project sites. Table 5 shows that the common feature of all abandoned mines that can be reused is excellent internal development conditions. Based on the analysis of the internal condition index system, this mainly refers to large-scale mines (>900,000 t/a) of the suburban/urban type, with convenient traffic conditions and low safety risks, whose closure has a great impact on the life of the surrounding population. This criterion can provide a reference for selecting abandoned mine reuse projects in China, thus addressing the problem of “which abandoned mines can be reused”. From a suitability perspective, the abandoned mines of types 4 and 8 can be popularized because of their good resource conditions, high ecological carrying capacity, and excellent external development conditions. The economic benefits of reusing them are obvious, as they can easily form demonstration projects and provide a reference and standard for selecting abandoned mine reuse demonstration project sites.

3.2. Division of Abandoned Mine Reuse Stages

The process of abandoned mine resources utilization is an issue of secondary mine exploration. It is particularly important to note that the reuse of abandoned mines plays a crucial role in building sustainable cities and communities in resource-depleted areas (SDG 11), as well as in responding to climate change and its impacts (SDG 13). Traditional coal exploitation denotes coal mines from cradle to grave, while the cradle-to-cradle (C2C) solution is usually employed in material reutilization. When the C2C concept is developed in coal mine construction, the second cradle is the new beginning of abandoned mines. According to the reuse value evaluation of abandoned mines, the reuse stages of abandoned mines are divided into three levels: primary stage, intermediate stage, and advanced stage. More detailed explanations for each stage can be found in the following text. Based on this, a set of 5R principles for the reuse of abandoned mines is designed, including recovery, remining, recycling, redevelopment, and reutilization. The 5R principles for comprehensively utilizing abandoned mine resources are detailed in

Table 10. Connections between utilization stages and the 5R principles.

Utilization Stage	Principle	Main Value	Key Points of Reuse
Primary stage	Recovery	Ecological value	Ecological restoration and management
		Safety value	Engineering safety treatment
Intermediate stage	Re-mining	Economic value	Underground coal gasification Coalbed methane extraction
	Redevelopment	Economic value and ecological value Economic value	Mine water utilization Geothermal energy development
		Ecological value and economic value	Ecological agriculture and tourism
	Reuse	Economic value	Ground land use Underground space utilization
Advanced stage	Recycle	Comprehensive value	Cultivation of new industries

, demonstrating the connections between the 5R principles and their utilization modes. The 5R principles form a level-by-level gradual strategy for making decisions on the reutilization stage.

(1) The primary stage of abandoned mine reuse refers to ecological development in a narrow sense; that is, only ecological recovery has been carried out, including serial numbers 1, 2, 5, 6, and 9. At this stage, the corresponding conditions are a high degree of ecological damage to abandoned mines and poor ecological management conditions. This stage focuses on dealing with pollutants from abandoned mines, restoring vegetation, and controlling engineering risks to meet the needs of ecological carrying capacity for life and economic development. Due to poor ecological conditions, the utilization rate of various resources is low at this stage, and abandoned mines exist in the form of individual “points”, which are not planned as a whole within and outside of the region, highlighting the ecological value of reuse. It should be noted that the ecological conditions in serial number 9 are not the worst, but the main reason why they are also in the primary stage is that the resource endowment is poor, leading to low economic and social value, and focus is often placed on simple ecological restoration.

(2) Based on ecological restoration in the primary stage, combined with the resource order of abandoned mines, the abandoned mines with compound high-quality resources are prioritized, and the abandoned mines with single high-quality resources are considered again as pilot projects. This phase includes serial numbers 3 and 7. At this stage, the corresponding conditions are good ecological conditions and at least some superior resources, while the external development conditions are poor. The reuse of abandoned mines does not include external conditions that can be integrated into large-scale social development planning (city and region). However, preliminary economic and social value development planning can be carried out in a small area, mainly focusing on resource and economic factors.

(3) The advanced stage refers to the utilization mode of combining the reuse of abandoned mines with the development planning of the whole city or a large area to form multiple industrial chains and emerging industries. This phase includes serial numbers 4 and 8. The corresponding conditions in this stage are excellent ecological conditions, internal and external development conditions, and at least some superior resources. This stage includes the available abandoned mines in the whole area, thus forming a “surface”. The reuse of abandoned mines in the Beijing West Mining Area has formed a variety of industrial models, which belong to the advanced stage of development.

4. Main Conclusions

(1) The reuse value of abandoned mines is divided into economic value, social value, and ecological value, among which ecological value is the foundation. Unlike suitability evaluation, the reuse of abandoned mines must follow the “value order” principle of prioritizing ecological value, followed by social value, and finally, economic value. Only by prioritizing ecological governance and restoration can the carrying capacity be provided for the subsequent development of abandoned mines. In terms of the theoretical contributions, this paper uses abandoned mines as the research object and, by constructing a universal framework for analyzing the reuse value, systematically analyzes the classification and hierarchical development of abandoned mine resources. This system comprehensively considers the coordination relationship between the reuse of abandoned mine resources and the ecological environment, as well as the regional economy balance. This method not only highlights the fundamental position of ecological value but also accounts for the role of other values in further dividing the development sequence. This research has significant theoretical value and practical significance in gradually activating the idle resources of abandoned mines, improving the ecological environment, and achieving the transformation and upgrading of resource-based cities.

(2) The evaluation of abandoned mine reuse value is influenced by three dimensions of indicators: resource conditions, ecological conditions, and development conditions. When reusing resources, priority should be given to comprehensive high-quality resources, while also accounting for specific resources with outstanding advantages. Given that this model is still at the theoretical stage and has not been applied in actual planning, in the future, this model can be integrated into a platform such as a GIS-based decision support system to enhance its guiding role in the practice of reusing abandoned mines.

(3) Based on the classification of abandoned mine reuse value, the reuse stage of abandoned mines can be divided into three stages, namely, the primary, intermediate, and advanced stage, forming the utilization type of “point-line-surface”.

The core contribution of our valuation model lies in its inherent design that prioritizes ecological restoration as a non-negotiable prerequisite for subsequent development. This approach fundamentally shifts the decision-making paradigm from a short-term, purely economic perspective to one that inherently fosters long-term ecological balance. By quantitatively linking the value of a mine to its restored state, the model ensures that the most sustainable pathway—which harmonizes ecological health with socio-economic benefits—is systematically identified and promoted, thereby securing a resilient and balanced ecological future for post-mining regions.