Model for Assessing Efficiency of Processing Geo-Resources, Providing Full Cycle for Development—Case Study in Russia

Abstract

The environmental impact and occurrence of frequent ecological disasters have prompted a reassessment of societal values in the modern era. There has been a shift in the economic model, moving away from the pursuit of extensive growth towards a sustainable development model that prioritizes the preservation of the natural balance. This issue is of particular relevance in regions where mining activities are prevalent. In such regions, mining enterprises exert a considerable burden on the ecosystem, acting as significant sources of industrial waste. In light of the aforementioned considerations, the objective of this study is to develop a model for assessing the efficiency of industrial geo-resource recycling, taking into account both environmental and economic factors. The methodology is founded upon the principles of the efficient and comprehensive exploitation of natural and industrial geo-resources, in alignment with the tenets of sustainable development and the theoretical tenets of a cyclic economy. The methodology for assessing the efficiency of geo-resource recycling is based on the following three principal analytical approaches: economic and statistical, structural and logical, and comparative. The article examines the genesis of industrial waste, delineates the divergent patterns of the accumulation and utilization of mining waste, and classifies categories of industrial waste. The principal stages of the feasibility study are delineated, an algorithm is devised, and a model for evaluating the efficacy of industrial raw material recycling is proposed. The enumerated factors facilitate the recommendation of the model in the selection of the most optimal investment project in industrial geo-resource recycling.

1. Introduction

The minerals concentrated in the Earth’s crust are in an equilibrium state and do not have a significant impact on the environment and humans. They become mobile at the stage of geological exploration. After the start of mining operations, the minerals in the mining area are activated and begin to affect humans by entering their life environment [1]. In this case, there is a transformation of the life environment into an area of impact [2,3]. The greatest impact on humans and the environment is caused by waste [4].

The mining and processing industries account for the largest percentage of the total volume of stored waste [5]. Modern technologies do not present the possibility of extracting only useful components from the subsurface. Waste rock or substandard ore that are extracted are stockpiled on the Earth’s surface (Figure 1a). Waste rock is supplemented by tailings (Figure 1b) and waste from metallurgical processing (Figure 1c). Together, these wastes form industrial masses. The volumes of such masses are increasing exponentially every decade.

In Russia, more than 1 trillion tons of solid and liquid waste has accumulated in industrial masses from the mining and processing industries. The annual growth of industrial accumulations ranges from 2.5 to 4.8 billion tons [6].

The extraction of minerals and the storage of industrial waste on the surface require the removal of significant areas from economic and natural turnover [6]. Often, such territories exceed the area of the city serving the given enterprise (Figure 1d). The presence of finely dispersed fractions in industrial masses causes their drift and increased dust formation. All this leads to a deterioration in soil quality and its composition within a radius of up to 50 km [7].

When moisture enters industrial waste, some minerals present dissolve, acquire mobility, and are washed out [8]. This leads to the contamination of soil, the surface, and groundwaters. Often, these washed-out substances have radioactive, poisonous, or toxic properties [9]. Methods for controlling material composition and the instruments used are discussed in [10,11]. Currently, along with the instrumental control method [12], space monitoring is widely used [13].

The classification of wastes from mining and processing enterprises distinguishes the following categories: wastewater; waste air; mineralized suspensions; and solid wastes. All allocated categories of waste have a single criterion—they are by-products, but, at the same time, each of these products has its own peculiarity of formation.

The formation of wastewater occurs during the pumping of underground and surface water runoff from underground mine workings and the bottom of quarries, water used during the drilling of wells, and water formed during the hardening of artificial fill mass [14]. In addition, water from mining, processing, and metallurgical plants, as well as effluents from waste dumps, are discharged into wastewater. Wastewater includes processing reagents, suspended solids, petroleum products, and many other components [15].

Waste air is generated during the cleaning of mine air (the removal of contaminated air) in open pits and mine workings. Contaminated air is formed in the places of the main and auxiliary production processes of the mine excavation, where ore and/or rock mass are separated by blasting, caving, or mechanical means. Also, an air mixture requiring subsequent removal is formed when ventilating above-ground buildings and structures (processing plants, stowing complexes, metallurgical complexes, etc.). Exhaust air includes [16] products of combustion and blasting operations; mineralized dust; gaseous oxides and oxides formed during ore processing; electric smelting dust, etc.

Mineralized suspensions or suspended solids are formed by the discharge of waste from ore processing (tailings) or in the process of wastewater treatment through sedimentation and the removal of sedimented fractions [17].

Solid wastes are formed as a result of the selective nature of the human use of subsoil resources and due to the mismatch between the composition of minerals and needs. Solid wastes include mining wastes (waste rock from stripping and drivage operations, substandard ores, etc.) and processing wastes (metallurgical slags, dry fractions of tailings, etc.).

By-products are generated at each stage of deposit development. Different stages are characterized by different waste volumes and compositions. Figure 2 shows the scheme of the influence of each stage of deposit development on the formation of industrial wastes.

The volume, quality, and hazard level of industrial waste depend mainly on the specific mining enterprise and the characteristics of the deposit being developed, as follows: mining technique; mining methos; ore processing method and metallurgical processing technology; mining and geological conditions (structural dip, depth; thickness, etc.); content of useful components; and so on.

The placement of solid fractions of mineral waste is carried out in specialized industrial waste masses [18], such as waste rock dumps; tailing ponds; wastewater reservoirs; metallurgical slag dumps, etc.

An intensification in mineral extraction, increase in mining depth, and reduction in the useful components in a raw material lead to a sharp increase in the volume of industrial waste [19]. This entails increases in industrial masses in both the horizontal and vertical directions. In this regard, new problems are added to the previously known negative consequences of surface waste storage, as follows:

• Disturbance of the wind regime in the vicinity of the masses, which leads to climatic changes [5,6];
• Disturbance of the stress–strain state under the weight of the industrial mass, which causes changes in the hydrogeological regime [20].

The presented negative consequences of the placement of industrial masses can be reduced through the development of innovative technologies. Innovative technologies that reduce the volume of industrial waste through reuse, recycling, or disposal are a way to reduce the impact of mining on the ecosystem [21,22].

Previously, specialists from international groups producing consultation and recommendation documents [23,24] collected information on slag dumps of mining and processing enterprises, made a potential assessment and gave recommendations for involvement in a closed cycle of waste-free (low-waste) technology, and proposed a new multi-level governance framework for the extractive sector, entitled the Sustainable Development Licence to Operate (SDLO). They also outlined the vector of development of the mining and processing industries in the SDLO paradigm.

The document “Mineral resource governance in the 21st century. Gearing extractive industries towards sustainable development” [23] notes that mineral resources present major governance challenges for many countries, in particular for low- and middle-income countries. A detailed analysis of all 17 Goals for Sustainable Development is presented. Also, the documents describe the mining and processing industries’ development stages and the problems of accumulating environmental and social impacts. The problems of mineral resource management and the current management architecture are analyzed. The prerequisites for effective mineral resource management for sustainable development are outlined and an effective hierarchical management system is proposed.

The analytical paper [24] “Best Available Techniques (BAT) Reference Document for the Management of Waste from Extractive Industries” analyzes management techniques for tailings and waste rock in mining activity, also highlighting trends for selected targets within each of the Sustainable Development Goals and introducing concepts about how some SDGs are measured.

For the purpose of a uniform understanding and application of Extractive Waste Directive (EWD), the paper [25] “Study supporting the development of general guidance on the implementation of the Extractive Waste Directive” notes that the governance architecture of the extractive sector currently suffers from a range of shortcomings, which undermine its ability to deliver social, economic, environmental, and governance benefits. It also systematizes the sources of pollution, assesses them, and classifies pollutants.

The same work is presented in [26] “Guidelines for Mine Waste Management Facilities”, with the only exceptions of a limited scope (northwest Canada) and limited regulations.

There is a need to set out clear principles, policy options, and best practices that are intended to function as a common reference point, enabling all public, private, and other relevant actors in the extractive sector to make decisions compatible with sustainable development.

Previous studies, various recommendations, and analytical documents do not contain clear criteria for the involvement of industrial wastes in processing. There are no parameters allowing for dividing industrial wastes into classes according to their degree of involvement in processing, and there is no mechanism for ecological and economic assessments of the efficiency of comprehensive exploitation.

The difficulty in implementing this task lies in the lack of not only a mechanism and criteria for involving industrial waste in recycling, but also a model for environmental and economic assessments of the effectiveness of the comprehensive exploitation of industrial geo-resources [18,19,27,28]. Therefore, the creation of a mechanism and the justification of criteria for involving industrial waste in recycling, as well as the development of a model for environmental and economic assessments of the effectiveness of the comprehensive development of industrial geo-resources, seem to be tasks that should be addressed.

2. Materials and Methods

Measures for the partial or full return of withdrawn lands to environmental and economic turnover are one of the main ways of reducing the load on the environment of a mining region [29]. Thus, the reclamation of lands disturbed by mining and processing operations involves the following steps to bring the changed landscape back to its original form:

• The filling of quarries [30], wastewater reservoirs, and suspension storage facilities [8,14];
• The elimination of solid fraction masses [29,31];
• The application of a fertile layer on the restored surface [32];
• The planting of vegetation, etc. [33].

However, reclamation procedures do not exclude the subsequent impact of “buried” waste and do not solve the issue of sustainable environmental and economic development [34,35,36]. One of the main directions of sustainable development in mining regions is to increase the comprehensiveness of mineral extraction and complete the use of natural and industrial geo-resources [37]. In this regard, the inclusion of industrial waste in the closed cycle of main and auxiliary production will help to achieve this goal [38]. The contents of valuable and harmful components must be reduced to zero before using industrial waste in waste-free (low-waste) technology [39].

Sustainable development projects include the following measures:

• The utilization of substandard ores and rocks from stripping and drivage operations;
• The utilization of tailings and metallurgical slags;
• Wastewater treatment;
• Waste air treatment;
• The reuse of mine workings and pit space.

Increasing the comprehensiveness of mineral extraction and the complete use of natural and industrial geo-resources is seen in the following:

• The mining of out-of-balance or low-grade ores;
• The mining of ores located in the subsurface or dumps of complex material composition;
• The extraction of valuable components from industrial waste to a zero level;
• A reduction in harmful components in industrial waste to sanitary norms;
• The extraction of valuable components from wastewater;
• The extraction of valuable components from electromelting dust;
• The use of “cleaned” industrial waste in various industrial sectors;
• The use of “cleaned” industrial waste in a closed cycle of mining production.

The recycling of industrial waste in the closed cycle of the comprehensive exploitation of geo-resources is predetermined by the following natural sequential factors:

• An increase in the demand for mined mineral raw materials and in the consumption of raw material products;
• The depletion of the mineral resource base of the mining enterprise and mineral deposits;
• A sharp increase in industrial waste, which leads to an increase in the negative environmental impact of both the formations themselves and the mining industry as a whole.

Recently, the economic, technical, and social factors of the involvement of industrial wastes in the closed cycle of production with the comprehensiveness of their exploitation have become of great importance, as follows:

• The globalization of the economy and increased competition in the international market;
• Condition reduction through the introduction of innovative technologies for the extraction of valuable components;
• The need for workplaces during the closure of mining town-forming enterprises.

Consequently, the most rational way to implement waste-free (low-waste) technology in the comprehensive exploitation of industrial resources is to extract valuable components from them until reaching a zero level [40], with subsequent involvement in a closed cycle of production or application in other areas of industry [41,42].

Masses of solid waste and mineralized suspensions in large quantities are in the vicinity of mining enterprises. This fact predetermines the possibility of replacing traditional components of backfill with industrial waste [43,44]. Earlier studies have demonstrated the positive dynamics of using industrial waste not only as an aggregate, but also as a binder [45]. One of the key green technologies in underground mining is backfill, which solves a number of important tasks, as follows: it facilitates the utilization of accumulated industrial waste, prevents dangerous surface deformations, and creates favorable geomechanical conditions for mining in difficult geological conditions [46,47].

Acidic or alkaline media in wastewater make it possible to use them as solvents in physicochemical technologies. In this case, wastewater should be activated with modifying additives before use to improve the extraction of valuable components from industrial waste and depleted or substandard ores. The recycling of pregnant leach solution or wastewater will allow them to be cleaned prior to discharge or reuse while producing marketable products.

A decisive factor in the involvement of industrial raw materials for the purpose of the comprehensive exploitation of geo-resources is the totality of economic and environmental feasibility [48].

Solutions for the following tasks will allow for achieving the set goal:

• Considering industrial formations and systematizing them, preliminarily defining unified assessment criteria;
• Assessing the material and chemical–physical composition of industrial masses (the presence/absence of valuable, associated, and harmful components);
• Identifying possibilities for the commercial and economic utilization of industrial waste;
• Performing process mapping;
• Developing and implementing technology for the comprehensive exploitation of industrial geo-resources and the extraction of valuable components with subsequent involvement in a closed cycle or manufacturing;
• Developing technical and organizational schemes and logistic flows of the comprehensive exploitation of industrial resources;
• Identifying the main criteria for assessing the economic and environmental efficiency of the proposed technology, involving industrial waste in processing and utilization;
• Developing an economic and mathematical model for assessing the efficiency of the comprehensive exploitation of industrial waste;
• Proposing an option for the rational and effective use of “cleaned” industrial waste or a method for its utilization.

A scheme of the involvement of industrial waste in a closed cycle of production in the sustainable ecological and economic development of a mining region with the comprehensive exploitation of geo-resources is shown in Figure 3.

The comprehensive exploitation of the mineral resource base of an individual enterprise or the Earth as a whole is not possible without the systematization of knowledge and the clarification (classification) of the main categories of geo-resources. The systematization of knowledge about geo-resources will provide a unified approach to the problem of the comprehensive exploitation of minerals and the creation of conditions for the sustainable development of enterprises in particular and regions as a whole. One paper [38] highlights the classification features of geo-resources—the conditions of their formation, which allowed us to distinguish the following three main categories: natural (geogenic or congenital); artificial (technogenic or man-made); and combined (mixed or natural–technogenic). These unified classification features and the systematization of knowledge allow for creating a basis of the unifying idea, and subsequently, within the framework of the designed mining system, to solve the consistent problems related to the rational use of resources considering the complexity of their development. This research approach is the foundation for creating conditions for the sustainable development of geo-resources that meet the requirements and interests of various actors in interaction.

3. Results and Discussion

3.1. Factors for Assessing the Efficiency of Industrial Geo-Resource Recycling

The assessment of the efficiency of innovative technologies for the processing and subsequent use of industrial raw materials requires highlighting positive and negative factors.

Negative factors include the costs of implementing innovative technologies and the additional costs of extracting valuable components from industrial raw materials, as follows:

• The development and implementation of economically feasible technologies for the extraction of valuable components from industrial raw materials;
• The search for efficient solvents that will ensure the selective transformation and ion intensity of the valuable components in the pregnant leach solution;
• The creation of prototype installations that facilitate the extraction of valuable components from industrial geo-resources, their production testing, and their industrial implementation;
• The direct recycling of industrial raw materials and extraction of valuable components;
• Logistics costs regarding the storage location or shipment to the customer.

The following are factors with a positive economic effect:

• Profits from the sale of additional valuable raw materials;
• A reduction in or even the elimination of costs for the placement and maintenance of industrial masses;
• The elimination of reclamation costs;
• A reduction in rent payments (land seizure, etc.);
• A reduction in expenses for the purchase of backfill components, etc.

The efficiency of industrial waste exploitation can be formulated by the difference that defines the excess of the total profit from the sale of additional products over the total costs of the development and implementation of innovative technologies and direct extraction, as follows:

$$E={{\displaystyle \sum }}_{t=1}^T{P}_t-{{\displaystyle \sum }}_{t=1}^T{I}_t,$$

(1)

where $E$—total economic effect for the design period; $P_t$—cost estimate of the efficiency of the implemented technology in the t-th year; $I_t$—estimation of implementation costs in the t-th year; and $T$—design period.

Only a detailed ecological and economic assessment, considering the above factors, will make it possible to make a decision about the feasibility of industrial masses’ exploitation. It should be considered that the correct choice of assessment criteria determines the main role in the assessment methodology development.

The criterion characterizes the level of the set task and is the basic (fundamental) assessment indicator. If the selected criterion approaches the closest (optimal) value when solving a task or implementing a project, then the task solution can be considered as satisfactory (acceptable). At present, many criteria have now been developed to assess the effectiveness of production, technical, or environmental solutions.

The complex ecological and economic criteria for industrial geo-resources’ involvement in the closed cycle of waste-free (low-waste) production and their subsequent application after recycling should meet the following requirements:

• Minimal total costs of major capital investments and additional costs of the recycling and utilization of industrial geo-resources;
• Environmental requirements of production (minimum environmental impact);
• Obligatory positive economic effects.

The involvement of industrial geo-resources in the closed cycle of waste-free (low-waste) production is supposed to be carried out at the expense of mining and processing enterprises, which determines the existence of the last requirement.

The choice of industrial raw material recycling technology, a specific industrial object, and production decisions are carried out by a feasibility study. In this case, special attention is paid to the environmental impact and ecological consequences of the selected technology, especially when industrial waste is used as raw material. In this regard, it is necessary to develop a mechanism for analyzing the involvement of industrial geo-resources in a closed production cycle and the subsequent use of raw materials “cleaned” to a zero level for manufacturing. This predetermines the development of technology with such involvement and its evaluation.

The total volume of industrial mass decreases during recycling—the additional extraction of valuable components and manufacturing from “cleaned” industrial geo-resources or utilization. In this regard, there is a change in the impact (positive or negative) of the mass on other objects in the vicinity. Therefore, the assessment of recycling technology impact requires considering industrial object reduction.

The assessment of the economic efficiency of the implemented innovative technology includes the following factors:

• The total volume of industrial geo-resources stored in tailings ponds, dumps, etc.;
• The total volume of industrial geo-resources that is technically feasible to recycle and economically valuable;
• The availability and degree of operational readiness of industrial objects;
• The amounts of different types of valuable components expected to be recovered in the process of industrial geo-resource recycling;
• The total annual volume of industrial mass intended for recycling and utilization;
• The extraction ratios of separate valuable components;
• The need to remove harmful components;
• The possibility of the subsequent use of “cleaned” raw materials in a closed production cycle or the manufacturing of additional products.

A number of studies take the current degree of readiness of industrial raw materials through the use factor of industrial waste. The use factor is the ratio of the volume of industrial geo-resources to the volume of products obtained from it [6,23,24].

3.2. Assessment of Production Efficiency of Industrial Geo-Resources’ Involvement in a Closed Waste-Free (Low-Waste) Cycle

Comparative assessment is a priority and includes a comparison of the production indicators of the object under study with analogous indicators of a similar object. Economic indicators, as usual, characterize efficiency. The analysis compares the cost of implementing the proposed activity (in our case, the development and implementation of technology for involving industrial geo-resources in a closed circle of waste-free (low-waste) production) with the result obtained (in our case, the income from the sale of valuable components and products from “cleaned” industrial geo-resources). This result can be expressed in different units of efficiency (absolute or relative units). Relative efficiency is the ratio of cost to result (income), and absolute efficiency is their difference. Absolute efficiency cannot demonstrate production costs, but informs about the magnitude of the economic effect. Relative efficiency informs production costs.

Present costs; capital intensity, differential rent; labor productivity; production cost and production profitability; net economic effect; payback period of capital investments; and capital investment efficiency indicators—these are only a small number of indicators for assessing production efficiency used in Russian studies [44,49,50]. The most commonly used indicator for assessing production efficiency in foreign sources is Net Present Value (NPV) [27,28,38]. NPV most clearly determines the effectiveness of the technology used among the indicators listed above. NPV demonstrates the profit gained by adopting some innovative technology compared to the previously used technology in the industry.

Feasibility studies of industrial waste recycling projects allow for assessing the effectiveness of the subsequent exploitation of the industrial object. Technological and technical process mapping is the first step in assessing the recycling technology effectiveness. Process mapping implies the following:

• The assessment of the chemical and material composition of industrial raw materials;
• Analyzing the content of harmful components in industrial raw materials for their subsequent reduction to sanitary norms;
• Analyzing the content of valuable components in industrial raw materials for the assessment of the technical and economic feasibility of their extraction;
• The assessment of the possibility of the subsequent use of “cleaned” industrial raw materials or their safe utilization.

The second step is the justification of the possibility of industrial raw material recycling and the development of innovative technology for valuable component extraction from industrial raw materials.

The third step is the formation of the scheme of industrial waste recycling. Scheme formation implies the generalized and simplified placement of main and auxiliary production objects in space. The objects of auxiliary and main production are equipment for the main product (productive brines), for auxiliary products (materials for the construction sector, filling complexes, etc.), storage sites or premises, and production facilities for the utilization of industrial wastes “cleaned” up to sanitary norms. The location of production objects is analyzed in terms of their distance from each other, from industrial plants, warehouses, etc., for the purpose of transport and logistical accessibility. Particular attention is paid to distance from residential sites for civil safety. The final realization of this step is a project report. This project report describes all the processes of industrial mass recycling, systematizes the stages of industrial raw materials passing up to the main (marketable) product, and storage or shipment. The project report includes layouts of production facilities and/or sites, equipment, calculations of the required raw materials, logistics chains (schemes), staffing, and so on.

The fourth step is the assessment of innovative technology options. Its basis is the calculation of NPV for one industrial mass or for a group of objects located at different distances but included in a single system.

$$NP{V}_{\mathrm{E}\mathrm{C}}={{\displaystyle \sum }}_{t=i}^{T}NPVi,$$

(2)

where NPV_EC—Net Present Value of industrial masses in the single system; T—individual industrial mass; i—number of industrial masses in the single system; and NPV_i—Net Present Value of individual industrial mass.

The Net Present Value of individual industrial mass is as follows:

$$\begin{array}{ll}& NP{V}_{\mathrm{T}\mathrm{M}}={\displaystyle \sum }_{i=1}^m{\displaystyle \sum }_{j=1}^n{\displaystyle \sum }_{t=0}^{T_{TM}}{\displaystyle \frac{1}{{\left(1+E\right)}^t}}[(0,01A_{p_i{t}_i}{C}_{M{T}_i}{\epsilon }_i·P_i+V_{\mathrm{C}{\mathrm{M}}_j}·P_{\mathrm{C}{\mathrm{M}}_j}+A{M}_1+A{M}_2)-A_{p_i{t}_i}(C_{op}+C_{per}+C_{dp}+C_{adm}+\\ & C_{zp}+C_{tr}{l}_{tr})-H_t-Y_e+Y_t^n]-{\displaystyle \sum }_{t=0}^{T_c}{\displaystyle \frac{K_{str}}{{\left(1+E\right)}^t}}\end{array}$$

(3)

where $m$—number of extracted types of valuable components from industrial raw materials; $n$—number of types of additional products; $A_{p_i{t}_i}$—annual volume of recycled i-th industrial raw materials in the t-th year of operation, tons/year; $C_{M{T}_i}$—average content of the i-th valuable component in the t-th year, %; ${\epsilon }_i$—extraction ratio of the i-th valuable component during recycling, unit fraction; $P_i$—price of the i-th unit of the extracted valuable component, RUB/ton; $V_{\mathrm{C}{\mathrm{M}}_j}$—volume of the produced j-th type of product, pcs or m³; $P_{\mathrm{C}{\mathrm{M}}_j}$—price of the produced j-th type of product, RUB/pcs. or RUB/m³; $A{M}_1$, $A{M}_2$—depreciation expenses, respectively, for the operating mobile equipment and for the fixed assets of production, with service life being unrelated to the industrial object development period, RUB; $C_{op}$—operating costs for the extraction of industrial raw materials, RUB/ton; $C_{per}$—operating costs for the extraction of useful components from industrial raw materials, RUB/ton; C_dp—operating costs for additional products (manufacturing), RUB/ton; $C_{adm}$—administrative costs, RUB/ton; C_zp—labor costs, RUB; $C_{tr}$—costs of transporting 1 ton of extracted valuable component per 1 km, RUB/ton·kilometer; $H_t$—total tax for the t-th year, RUB; $l_{tr}$—transport distance, km; $K_{str}$—expenditure on major construction of the enterprise, RUB; $E$—internal rate; $T_{TM}$—useful life of industrial object (mass), year; $T_c$—period of enterprise construction for industrial object exploitation, year; $Y_e$—economic damage from industrial object exploitation on the environment, RUB; and $Y_t^n$—prevented damage, RUB.

$${\mathrm{y}}_e={\displaystyle \sum }_{n=1}^n{\displaystyle \sum }_{p=1}^P{\displaystyle \sum }_{c=1}^C{\displaystyle \sum }_{t=1}^T\left[(Q_{\mathrm{a}}+Q_g+Q_l\right)\times \left(P_z{C}_{\mathrm{K}}-P_o{C}_o\right)]K_Y{K}_T{K}_H$$

(4)

where $Y_e$—economic damage from industrial mass recycling on the ecosystem; Σ—sum of factors affecting the ecosystem; $T$—exposure time; $n$—number of factors affecting the ecosystem; $P$—volume of work to eliminate the consequences of environmental disasters; $Q_l$, $Q_g$, $Q_{\mathrm{a}}$—amount of pollutants in the lithosphere, hydrosphere, and atmosphere; $P_z$—volume of compensation work; $C_{\mathrm{K}}$—cost of compensation work; $P_o$—volume of ecosystem protection work; $C_o$—cost of ecosystem protection work; $K_Y$—time coefficient for greater impact on the system; $K_T$—coefficient of environmental disaster prediction; and $K_H$—coefficient of ecological disaster risk from unaccounted factors.

If variables such as exposure time $T$; the number of factors affecting the ecosystem $n$; the volume of work to eliminate the consequences of environmental disasters $P$; the volume of compensation work $P_z$; the cost of compensation work $C_{\mathrm{K}}$; the volume of ecosystem protection work $P_o$; and the cost of ecosystem protection work $C_o$ are used in many calculations, then the calculation of pollution indicators and coefficients require special attention.

The calculation of the amount of pollutants entering the atmosphere $Q_{\mathrm{a}}$ is carried out using approved methods [51,52]. There is no single method for calculating the overall air pollution indicator. Different methods are used for individual indicators [51]. Therefore, it is necessary to consider the total indicator for individual pollution sources adopted in the method [47], as follows: during blasting in open pits (method #1); the mechanical processing of metals (#17); from a blast furnace (#71), converter (#72), electric steelmaking (#74), rolling (#76) production equipment, and slag processing (#75); from area sources during blast furnace slag storage (#77); emissions into the atmosphere through mine ventilation shafts (#80); from the surface of tailings storage facilities and dumps (#107); and during fuel combustion in internal combustion engines (#115).

The total soil pollution index $Q_l$ is determined in accordance with the methodology [53].

The method for determining the amount of pollutants in the hydrosphere $Q_g$ is described in detail in document [54]. In accordance with this method, a set of formalized characteristics from intermediate and main indicators is calculated.

The essence of this method is to establish the level of water pollution and the frequency of regulatory requirements’ violation. The method determines complex characteristics corresponding to the ‘shares’ of pollution contributed by each pollution indicator to the overall water quality.

The level of water pollution at a specific observation point, determined through a relative characteristic calculated based on the actual concentrations of pollutants and relevant standards, is the first component of the comprehensive assessment method. The frequency of exceeding standards is an indirect assessment of the duration of water pollution. This value characterizes the extent of the impact of pollutants on water quality and is the next component of the recommended assessment method.

In addition to specific calculated values of pollution levels for individual indicators, the formula includes coefficients. Despite the precise calculation of the economic damage from industrial mass recycling on the ecosystem and correct “theoretical” calculations, in practice, there is often a deviation from the proposed calculated values, which leads to a decrease in the reliability assessment.

Thus, theoretical calculations can be interpreted as “standard”, i.e., not considering the significance of a separate factor (complex of factors). The theory of solving a complex problem based on the multicriterial efficiency method offers the integrative assessment method or the summed mean square weight deviation method [55]. Therefore, in order to correctly take into account a particular factor in a uniform evaluation system, it is necessary to introduce a relative importance coefficient. The relative importance coefficient is necessary to increase or decrease the influence of a given factor in the calculation methodology (algorithm).

The importance coefficient has an intuitive, estimated value for each expert. The importance coefficients of ecological and economic parameters can be determined by processing the obtained expert information with the opinion of a group of experts. Thus, the experts’ opinion and the function presented in [55] allow us to calculate importance coefficients or introduce individual indicators that affect the assessment of economic damage from industrial mass recycling on the ecosystem.

The time coefficient for a greater impact on the system $K_{\mathrm{y}}$ is calculated by the following three coefficients: $k_1$—recovery period (

Table 1. $k_1$—recovery period coefficient.

Recovery Period, Year	k1	Recovery Period, Year	k1
1	0.9	8–10	5.6
2	1.7	11–15	7
3	2.5	16–20	8.2
4	3.2	21–25	8.9
5	3.8	26–30	9.3
6–7	4.6	>31	10

); $k_2$—depth of pollution (

Table 2. $k_2$—depth of pollution coefficient.

Depth of Pollution, cm	k2
0–20	1
0–50	1.3
0–100	1.5
0–150	1.7
0->150	2

); and $k_3$—ecological significance of the territory (

Table 3. $k_{\mathrm{3}}$—ecological significance of the territory.

Economic Zoning of Russia	k3
Northern (N)	1.3
Northwestern (N/W)	1.4
Central (C)	1.8
Volga-Vyatka (V/V)	1.5
Central Black Earth (C/B)	2
Volga (V)	1.9
North Caucasian (N/K)	1.9
Ural (U)	1.7
West Siberian (W/N)	1.2
East Siberian (E/S)	1.1
Far Eastern (F/E)	1.1

).

The coefficient of environmental disaster prediction $K_T$ can be qualified as the probability of negative changes in the environment caused by various situations of a natural and anthropogenic nature at all levels (from point to global). However, there is still no strict definition of the concept ‘environmental disaster prediction’. This is primarily since environmental disaster prediction is a multifactorial system of causes and consequences. In brief, environmental disaster prediction is the degradation probability and consists of seven levels (

Table 4. $K_T$—environmental disaster prediction coefficient.

Level	Probability	${\mathit{K}}_{\mathit{T}}$
0	None	0
1	Unlikely	0.075
2	Acceptable	0.15
3	Weak	0.3
4	Moderate	0.6
5	Probable	1.5
6	Very likely	2

).

The coefficient of ecological disaster risk from unaccounted factors $K_H$ is the probability of causing harm to humans and nature over a certain period. From a safety point of view, the more frequent the hazardous situation and the higher the severity of the consequences, the higher the risk, i.e., the risk acts as a measure of the danger of an event.

The causes of environmental disasters may be different, and there are even more unaccounted factors. In most cases, researchers divide risks into the following two subgroups: human (anthropogenic) and natural. This position is not quite correct. Disaster risk and the environmental disaster itself is a chain that causes negative processes in the environment. The chain of interacting components and various hierarchical levels ‘live’ in spatial and temporal coordinates, e.g., risk, consequences of environmental risks, environmental disaster, consequences of the disaster, etc. In this regard, it is necessary to talk about two groups of risks, temporal and spatial.

The source of spatial risk is located in space and can be marked on a map. For example, phenomena such as sudden volcanic eruptions, earthquakes, avalanches, mudflows, etc., may cause damage to the protective dam of a tailings storage facility, leading to the destruction of pillars. Thus, the factors mentioned above refer to the unaccounted risks of an environmental disaster and the probability of the occurrence of these risks. Volcanoes and earthquakes occur in areas of tectonic activity at lithospheric plate boundaries, hence, they can be marked on a map. The proximity or remoteness characterizes the degree of risk. In the same way, the risk of debris flows, rockfalls, or avalanches can be assessed. These phenomena are more likely to occur in mountainous regions and less likely to occur in flat areas.

Phenomena that manifest or change over time are referred to as temporal factors. For example, the geopolitical situation changes over time and its aggravation may lead to armed conflict. As a result of military operations, the infrastructure facilities of mining enterprises may be damaged, such as tailings dams, the storage of reagents for concentrators, etc., which can lead to an environmental disaster. The service life of an enterprise is also a temporary factor. Increased plant life provides ‘fatigue’ in mining infrastructure (e.g., dams), supporting elements of mining methods (e.g., pillars), etc., which may lead to their destruction.

An assessment considering the importance of the time factor is not possible due to the lack of a common numerical competent opinion of specialists. Experts were enthusiastic about the life-of-mine factor, but the geopolitical situation did not lead to a consensus. It is not possible to calculate the time factor’s impact on the risk of a disaster considering [54]. It is also necessary to assess the risk of terrorist attacks as a time factor.

The risk coefficients of ecological catastrophe $K_H$ from unaccounted factors are presented in

Table 5. $K_H$—coefficient of ecological disaster risk from unaccounted factors.

Factor	N	N/W	C	V/V	C/B	V	N/K	U	W/N	E/S	F/E
Earthquake	1.0	1.1	1.0	1.0	1.0	1.1	1.4	1.2	1.3	1.4	1.6
Volcano	1.0	1.0	1.0	1.0	1.0	1.0	1.1	1.1	1.1	1.2	1.5
Relief	1.0	1.2	1.0	1.0	1.0	1.0	1.3	1.1	1.2	1.3	1.3

. Here, the economic zoning of Russia was used to determine the coefficient of the ecological significance of the territory k₃.

The zones of tectonic activity at the lithospheric plate boundaries in Russia are confined to three belts, Alpine–Himalayan, the Pacific geosyncline, and the Ural–Okhotsk geosyncline, as well as one rift zone (a deep fault in the Earth’s crust), Baikal. Near these zones, the risk of earthquakes (seismic risk) is increased, therefore, the risk coefficient of an environmental disaster is higher. It is also necessary to consider plate activity. While in the Ural Mountains (the most ancient Ural–Okhotsk geosynclinal belt), there is practically no plate movement, the activity in the Altai Mountains and Sayan Mountains is significantly higher. Consequently, the coefficients will differ. However, even in the low-activity Ural Mountains, the probability coefficient will be higher than that directly on the plates.

The map is quite wide and it is difficult to clearly define the coefficient for a specific enterprise. The Far Eastern zone is large. Its eastern part is in the active Pacific geosyncline, the southern part is in the low-active Ural–Okhotsk geosyncline, and the northern part is on a platform where activity is reduced to zero. The risk coefficient of an environmental disaster is determined by the average value. Therefore, in the following studies, it is necessary to make a clearer delineation of the zones to determine the exact values of the coefficients.

The risk of tsunamis, typhoons, hurricanes, and tornadoes is important for coastal areas. This is an important indicator, but it is not typical for Russia.

The final fifth step is the distribution of industrial objects (arrays) according to the NPV criterion. The following classes of industrial masses with a classification sign of recyclability are distinguished: highly valuable (first-priority recycling); valuable (prospective recycling); of medium value (near-term prospect); of low value (remote prospect); and non-valuable (no recyclability). The NPV is constantly being adjusted due to changes in the market value of products and capital expenditure. Consequently, the feasibility of a certain capital investment will change. The development of science and technology increases accessibility to underground resources and improves the quality of industrial raw material recycling. This factor also has a significant impact on the NPV. It follows that the NPV for each class changes over time, while the classification sign remains unchanged. Recycled industrial waste that is not suitable for future recycling is used for manufacturing or disposal. The fundamental factor in this case is the absence of harmful components, otherwise, industrial waste is cleaned to sanitary standards.

A model needs to be developed to choose between manufacturing, use in auxiliary production, and disposal. The economic criterion for a rational method of utilization is the minimum of discounted costs of DC.

$$\sum D{C}_i=K_i+E_i-A{Z}_{1i}-A{Z}_{2i}-A{Z}_{3i}\to min$$

(5)

where $D{C}_i$—total discounted costs for the i-th method of utilization, RUB; $K_i$—discounted costs of capital works, RUB; $E_i$—discounted costs of operating work, RUB; $A{Z}_{1i}$—discounted costs of depreciation expenses (main specialized production assets, where the service life is determined by the period of industrial raw material recycling), RUB.; $A{Z}_{2i}$—discounted costs of depreciation expenses (main specialized production assets, where the service life is not related to the period of industrial raw material recycling), RUB; and $A{Z}_{3i}$—discounted costs of depreciation expenses of mobile equipment, RUB.

3.3. Model of Environmental and Economic Assessment of Efficiency of Industrial Waste Recycling

The proposed model for the ecological and economic assessment of industrial waste recycling efficiency and its algorithm (Figure 4) are based on the difference in total cash flows brought to the present (NPV). The model considers all the features of industrial mass, as follows: the amount of valuable components; the presence/absence of harmful components; the annual volume of recycled materials; the volume of industrial mass; the possibility of using the recycled waste; the quantity of products produced, etc. The model calculates the following financial indicators: the price per unit of the produced goods; depreciation expenses (for mobile equipment and main assets of production); operating costs; administrative costs; logistics costs, etc. The main indicators of the project environmental stability are environmental damage from industrial object exploitation and prevented damage.

Based on the above, it can be stated that the developed model is quite variable, as it considers many factors of different industrial wastes. Consequently, the proposed model is applicable to the assessment of different types of industrial objects.

3.4. Economic Efficiency of Industrial Geo-Resources’ Exploitation in the Example of Tailings of the Ural Mining and Metallurgical Company

The feasibility of involving industrial waste in a closed cycle of waste-free (low-waste) production, considering a specific mining and processing enterprise and recycling technology, is determined by assessing the maximum efficiency and the greatest economic effect. Papers [56,57,58] have substantiated the multiplicative effect considering reductions in the consequences of environmental disasters and ecosystem degradation because of mining, processing, and metallurgical production, but the analysis showed that all methods are complicated in their calculations and there are a lot of different coefficients and assumptions, which does not allow for calculating the effect with an approximate accuracy [59].

The proposed model for industrial resource recycling not only allows for preventing negative impact on the environment, but also for gaining profit. In this context, the prevention of negative impact is paramount. In this regard, the economic effect of minimizing the impact of waste on the environment is considered unconditional [60]. Therefore, it is necessary to understand the profit from products derived from the recycling of industrial resources. The proposed technology may have a zero economic balance between the invested funds and the profit received (i.e., the absence of a direct economic effect). At the same time, the disposal of man-made waste allows us to assert the presence of an environmental effect. This indicates that the proposed model is operational and is necessary for implementation [61].

The proposed technologies are associated with significant and constantly increasing investment and operating costs. Therefore, the economic efficiency of the implementation of the proposed innovative technologies is equal to the difference between the cost of products obtained after industrial resources recycling and investment costs associated with the implementation of the proposed technology.

Previous research [62] presents a simplified assessment of industrial deposits with the example of tailings of the Ural Mining and Metallurgical Company.

Table 6. Summarized information on reserves in industrial masses and of possible extraction [64].

Tailing Dumps of the Processing Plant	Copper		Zinc		Iron		Gold		Silver
	Reserves [62]	Extraction [63]	Reserves [62]	Extraction [63]	Reserves [62]	Extraction [63]	Reserves [62]	Extraction [63]	Reserves [62]	Extraction [63]
	Thousand Tons						Tons
Sibay	34.5	33.637	90.0	88.92	5900.0	5811.5	13.9	11.0	344.0	305.5
Uchaly	90.0	87.75	257.0	253.9	8050.0	7929.2	16.5	13.1	232.0	206.0
Buribai	25.0	24.375	11.6	11.46	1280.0	1260.8	6.60	5.24	56.8	50.5
Guy	120.0	117.0	92.0	90.9	5550.0	5466.8	32.0	25.4	160.0	142.1

shows the possible volumes of the valuable component extraction upon the implementation of the proposed technology considering the results [63] of extractability from industrial waste. The table columns are reserves for each component and are taken from the study [62]. In the calculation, ideal conditions were assumed, where commercial extraction did not change relative to laboratory results [63].

The remaining products after industrial geo-resource recycling can be considered as alternative components for production, as follows:

• Backfill,
• Construction material,
• Pavement,
• Embankments for dams, roads, railways, etc.

In the assessment of economic efficiency, the proposed model does not include the profit from the use of the remaining products after recycling.

The project plan provides for the creation of a production facility for industrial waste processing with a capacity of 200 thousand tons per year and its implementation over two years (

Table 7. Project plan.

Steps	Quarter								Capital Investments, RUB Million
	I	II	II	IV	V	VI	VII	VIII
Geological mapping of tailing dump and study its raw materials. Feasibility study of investments.	X	X							350
Development of technical assignment and design-and-operational documents. Adaptation of technology.		X	X	X					550
Development of a production project. Experimental design works.			X	X	X				600
Production of non-standard technological equipment.				X	X	X			4000
Complete by standard equipment.						X	X		2800
Performing construction and installation work.							X	X	1700
Testing and commissioning.								X	1200
Total:									11,200

).

The capital investments presented in Table 7 are indicative. They were obtained by expert assessments through a survey of specialists and are subject to clarification at the design stage. On the day of writing the article (1 June 2024), the ruble–dollar exchange rate was 90.19, therefore, the cost of the project to implement the proposed technology is USD 124,182,281.8. The annual revenues of the enterprises were calculated on the basis of annual productivity, the valuable component percentage in industrial waste, the extractability of this component established by a laboratory method, and the metal prices on international exchanges on the day of writing the article. The costs per ton of metals contained in the studied industrial formations on the London Metal Exchange are as follows: copper—USD 10,069.00; zinc—USD 2914.53; and iron—USD 117.68; and per troy ounce of raw materials, silver—USD 30.54 (USD 0.982 per one gram) and gold—USD 2348.7 (USD 75.52 per one gram).

Table 8. Production indicators of the tailings processing enterprise.

Tailing Dumps of the Processing Plant	Waste Volumes [47], Million Tons	Productivity, Thousand Tons/Month	Annual Revenue, Million USD/Month	Payback, Month	IRR, %	Raw Material Class	Term of the Work, Year
Sibay	28.5	200	14.898	8.28	21.9	Highly valuable	142.5
Uchaly	40.8	200	15.264	8.13	22.3	Highly valuable	204
Buribai	5.5	200	14.815	8.38	21.4	Highly valuable	27.5
Guy	40	200	10.108	12.28	18.5	Valuable	200

presents the production indicators calculated on the basis of metal costs on international exchanges and the waste volume on the tailing dump determined in [62].

The analysis of the results shows that industrial waste recycling projects, namely, tailings, are effective. The payback period for investments in different tailing dumps ranges from 8.13 months to 12.28 months. Table 3 shows that it is possible to vary the production capacity and to achieve the most effective indicators in the processing enterprise.

The approximate assessment of project capital investments, unreliability, the inaccuracy of metal value forecasts (in our case, valuable components), and theunpredictability of geopolitical events lead to the impossibility of forecasting financial cycles and calculating the discount multiplier in a financial crisis. All these factors did not allow for the discounting of cash flows when making calculations and estimates. Also, the calculations did not consider VAT refunds and income from the use of “cleaned” industrial geo-resource as backfill in mining, in civil engineering, etc. The calculations did not consider the income from the use of “purified” industrial geo-resources. The benefits associated with a reduction in environmental damage were not assessed due to insufficient data.

The analysis of calculations and the assessment of the efficiency of industrial geo-resource recycling in the example of the Ural Mining and Metallurgical Company showed that all tailings are suitable for recycling and this raw material is highly valuable.

4. Conclusions

Modern society has undergone a colossal reassessment of values, so the fundamental development vector is the preservation of the natural balance and the greening of industrial production. The recognition and implementation of the global principles of environmental safety in the Russian economy will make it possible to move from a scheme of simple economic growth to a model of sustainable development. The principles of environmental safety imply the introduction of waste-free (low-waste) production with the following advantages: industrial waste recycling; the long-term use of production facilities; increase in the mineral resource base of the mining enterprise; increase in the life of the enterprise; additional workplaces; additional products; increase in the enterprise profit; financial stability and competitiveness of the enterprise; and improvement in the environmental situation. The introduction of waste-free (low-waste) production will gradually transform the vectoral-to-peak economy into an economy of the cyclic closed type.

The need for the greening of industrial production and a cyclic closed economy has created prerequisites for improving the methodology and developing a model for assessing the efficiency of industrial geo-resource recycling considering environmental and economic parameters. The proposed methodological approach to assess recycling efficiency is based on the difference between the total cash flows (outflows and inflows) brought to the present time (the moment of assessment of the proposed investment project). The assessment of project efficiency (NPV) considers all factors and demonstrates the overall picture of a project.

Project assessment by NPV is a multi-criteria decision, therefore, this methodology is recommended for the expertise of raw material recycling efficiency for all industrial formations.