Sustainable management of water and tailings in the mining industry

Abstract

The mining industry consumes water and energy to produce a metal or mineral product from mineral resources on the earth’s crust, leaving enormous waste. The main waste produced by the mining industry is mine tailings, which generally consist of a slurry containing water and reagents used in the processes and crushed ore. Tailings are usually stored in dams that can threaten the environment since they can pollute soil, water bodies and nearby communities. Water is used in most mining processes, as well as in the management of tailings. Since most mines are located in arid zones, reducing water consumption is crucial for the efficient use of water resources. The mining industry has improved water and energy efficiency and strengthened tailings disposal. Nevertheless, considerable effort is still needed to ensure the sustainable development of the mining sector.

This dissertation aims to develop methods and tools to advance sustainable development in mining, focusing on water and tailings management. The strategies and tools proposed can be applied in mining processes to mitigate environmental impacts and enable the sustainable development of this industry. Methods used in this dissertation include mathematical optimisation, economic valuation methods and sensitivity and uncertainty analyses.

To improve water management for mining companies, we proposed a method to supply water to several mine sites with the option of producing energy in the network. Another contribution was a framework to improve the water-energy nexus in mine sites, focusing on tailings disposal technologies. The methods used to accomplish this goal were a water reduction model, real options approach, and sensitivity and uncertainty analyses. Results show that an integrated system to supply water for mining companies, including energy production in the network, can be cheaper than an independent supply for each company. Moreover, dewatering technologies for tailings will reduce the water requirement to the mine site, reducing overall costs and reducing energy consumption in water transport and treatment.

To improve mine tailings management, besides the use of dewatering technologies to recover water, the reprocessing of tailings is proposed to recover critical raw materials (CRMs) since some tailings contain quantities of them. A framework is applied, that includes quantifying CRMs in tailings, economic assessment using the discounted cash flow (DCF) method, and a real options approach with sensitivity and uncertainty analyses. Results show that tailings have quantities of CRMs. Tailings can be a secondary source of these materials in the future, under the right conditions of capital expenditure, operating expenditure and prices.

This dissertation provides a collection of methods to improve tailings and water management in mining. This study’s novelty consists of considering both water and tailings to enhance the management of tailings and water supply to mine companies by considering the energy component of water treatment, transport and water used in tailings disposal. In addition, the possibility of obtaining CRMs from tailings is studied using an economic approach that introduces real options analysis to complement traditional valuation tools. The importance of this dissertation relies on proposing methods and tools to guide mining towards more sustainable water and tailings management that includes recovery of water and CRMs from tailings.