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Mining Sustainability: A Reality in Arid Zones

Elizabeth J. Lam1, Italo L. Montofré2,3, and Fernando A. Alvarez4

1 Chemical Engineering Department, Universidad Católica del Norte, Antofagasta, Chile

2 Mining Business School, ENM, Universidad Católica del Norte, Antofagasta, Chile

3 Mining and Metallurgical Engineering Department, Universidad Católica del Norte, Antofagasta, Chile

4 Administration Department, Universidad Católica del Norte, Antofagasta, Chile

1.1 Introduction

Mining, one of man's oldest and most important activities (Dubinski 2013; Candeias et al. 2018), has depended on extracted products since the beginning of civilization. Due to the crucial need for materials for industrial and human development, its participation in the economic structure of mining countries and the global economy has greatly increased in the last few decades, currently being one of the world's main economic activities (Lodhia 2018; Lam et al. 2021).

The mining process is based on the extraction and processing of materials of interest (Whitworth et al. 2022). It consists of consecutive operational stages: prospection; exploration; project assessment, development, and construction; resource production and exploitation; and operational closing. These stages may cause environmental and social impacts (Haddaway et al. 2019).

Ore extraction processes have changed with time, forcing the generation of more efficient processes environmentally and community-friendly. In addition, current trends in the extraction of ore with an increasingly lower grade pose new challenges for waste management, considering the increased number of wastes from mining units. This decreased ore grade is accompanied by a tendency to make new explorations and start new mining operations to balance decreased production, by further extracting and processing ore. This results in increased ore drilling, loading, and transport, thus increasing concentrator capacity and leaching processes. Also, low-grade ore makes it necessary to transform it into smaller particles, therefore increasing grinding and its associated energy requirements (Lagos et al. 2018).

Analogically, the production and exploitation stages cause environmental impacts such as industrial emission of sulfur dioxide and nitrogen oxides, high water consumption for industrial processes, and massive mining wastes (MMWs) such as tailings, residues, slags, sterile material, and solid wastes, among others (Lam et al. 2017, 2020a; Zhou et al. 2021). In addition, mine closing has become one of the most important stages on a global basis since a plan is needed from mining companies to mitigate the negative effects of the extractive mining industry, ensuring the physical and chemical stability of installations and mining wastes, according to the legislation on a country basis. In Chile, the closing plan must safeguard people's lives, health, safety, and the environment, according to law 20.551, regulating the closing and post-closing phases of mining sites (Lam et al. 2018).

Impacts from mining processes can be classified into six main groups: (i) soil quality, (ii) flora and fauna, (iii) air quality, (iv) water resources, (v) socioeconomic conditions, and (vi) climate change. These impacts make it necessary to face a series of challenges, even more so when the demand for most minerals may increase in the next few years. In addition, considering sustainable energy transition, the mining industry must create new technological developments to exploit increasingly complex ore bodies, accept the requirement to decrease water and energy resources, optimize waste management in the context of a circular economy (CE), and respond to climate change effects due to increased greenhouse gas emissions (Valenta et al. 2019).

Owing to the spatial distribution of resources, mining activity can be developed in different geographic regions, each of them with particular challenges depending on environmental conditions and the nature of mining activity, considering the type of ore and the processing method. These challenges are particularly relevant in arid zones, where impacts are notorious, considering ecosystem fragility and water scarcity (Liu et al. 2019). For these reasons, the mining industry in arid zones faces different challenges to make production sustainable, particularly the supply of critical agents such as water and energy, along with ecosystem preservation. This challenge is faced by using and controlling sustainability indicators for arid zone mining. At present, many factors could be considered sustainability indicators, such as water consumption, electric and fossil energy consumption, greenhouse gas emissions, land distribution, waste management, and finally, environmental and social impact.

In a different ambit, mining activity evolution has caused an impact on the economic development of many countries such as Chile, where, apart from contributing to the economic development of mining regions, it also influences the development of human beings, who are constantly requiring various mining raw materials and input for creating products and technology for man's progress (Qi 2020). Among mining countries, Chile is a world leader in the production of copper, iodine, rhenium, lithium, molybdenum, boron, silver, and gold (Ministerio de Minería 2022). This brings about great economic benefits, but, on the other hand, it produces a negative environmental impact associated with risks affecting the environment and the population (Castro and Sánchez 2003).

In Chile, mining production became massive in 2001-2015. At the same time, mines aged owing to a decreased ore grade. So, mining activity increased by starting new operations mainly in the country's northern zone, characterized by arid environmental conditions. These zones show scarce rainfall and vegetation, a dry climate, and high differences in temperature between day and night, making it particularly difficult to obtain resources such as water and energy, thus putting ecosystem stability at risk. Hence, sustainable mining must be developed, involving rational natural resource consumption so that annual production cannot jeopardize resources for future generations (Lagos et al. 2018).

1.2 Mining in Chile

1.2.1 Economic Benefits of Chilean Mining

Most Chilean mining industries are located in the northern zone, characterized by extreme climatic conditions. Exploitation, apart from economic benefits, has important impacts on the environment and ecosystems. So, it is essential to address future mining by focusing on sustainability, considering three basic pillars: economic, environmental, and social. Therefore, efforts must be directed to actions for maximizing profits, according to available resources, and preserving natural resources for proper ecosystem functioning and equilibrium. Both aspects must be in agreement with the demands and needs of local and surrounding populations, fostering citizen dialog, commitment, and participation in fair and equitable decision-making (Aznar-Sánchez et al. 2019).

1.2.2 Negative Impacts of Chilean Mining

Chilean mining produces great volumes of waste, by extracting, using, and processing ore, which is discarded or accumulated, occupying big spaces. It is estimated that more than one million tons of waste from ore concentration and more than two million tons of sterile material are generated daily. The decreased grade of ore deposits currently exploited and those projected requires treating increasingly higher amounts of ore tonnages to keep or increase production levels. In this context, the amount of waste to be disposed of either as sterile material or tailings will increase. Tailings are estimated to increase twice by 2035. According to Art. 23 D.S 148, 2003 (Sanitary Rules for Dangerous Waste Management), from the Ministry of Health, sterile material, low-grade ore, leaching wastes, tailings, and debris make up the so-called MMWs, which result from mining operations (Pérez et al. 2021). Tailings are deposited near mining sites. They can be defined as finely ground material piles consisting of a mixture of gangue, rock fragments, sediments, etc. Tailings are not originally considered "toxic"; however, they can acquire this characteristic when combined with water. Examples of this are arsenic, copper, zinc, lead, etc. (Adiansyah et al. 2015; Peña-Ortega et al. 2019).

1.2.3 New Mining Process Redefinition

On a country's basis, four technological challenges are defined: facing increasing water and surface scarcity, minimizing infiltration impact and ensuring ore deposit stability; promoting the change of wastes into assets; and fostering community inclusion and agreement. By facing these challenges, new mining is expected to not only be concerned about economic benefits from mineral production and exploitation but also committed to incorporating these sustainability elements in their processes and become an industry more friendly with the environment and the different habitats sharing the territory intervened.

In this new view of mining processes, another great concern is the responsible management of materials with low economic value, which are not of great interest for...