Background and links - sustainability in natural resources
Introduction to Sustainability
Sustainability was defined in the 1987 Brundtlant report as "development which meets the needs of the present without compromising the ability of future generations to meet their own needs". Sustainability principles incorporate triple bottom line thinking - economics, environmental and social aspects. The shift to more sustainable practices has been aided by development of reporting standard such as Global Reporting Initiative (GRI), and risk management frameworks such as the Equator Principles.
At Resourceful Paths, we focus on sustainability issues relating to natural resources, particularly environmental and economic aspects of producing and using mineral and metal products. Relevant issues in mining include: social license to operate; water consumption and pollution management; tailings management and minimizing disturbance footprint; and climate change.
Climate change 101
Certain gases in the atmosphere absorb and trap heat radiated from the Earth, a phenomenon known as the greenhouse effect. These greenhouse gases (GHGs) include water vapour, carbon dioxide, methane and nitrous oxide. Human activities have greatly elevated carbon dioxide, methane and nitrous oxide atmospheric concentrations, contributing to climate change. The primary causes of the increases are: burning of fossil fuels (coal, oil and natural gas) for electricity generation, transportation and industrial use; and agricultural practices. GHG emissions can be reduced by reducing energy consumption, developing low carbon sources of energy such as renewable (e.g. solar, wind, hydro) electricity, and in some cases, carbon capture and storage. Efforts to reduce greenhouse gases vary by region depending on the sources and uses of energy. Resourceful Paths contributed to an ARENA handbook on Hybrid power generation for Australian off-grid mines to reduce greenhouse gas emissions.
The IPCC has completed comprehensive analysis on climate change fundamentals and mitigation strategies. At times, climate change generates debate, however, the vast majority of climate change scientists agree that climate is happening, and information has been compiled to explain many of the perceived controversies.
Major fossil fuel exporting countries are closely connected to climate change even though these fuels are burnt in the countries that import them. Here is a presentation that explains some of these links, in relation to coal mines in Queensland that export to Asia, currently or potentially in the future: The role of Queensland coal in climate change.
Sustainability in mining
Sustainability goals in mining include minimizing climate change impacts from energy consumption; minimizing water consumption and potential contamination (e.g. from acid rock drainage), and the safe and environmentally acceptable disposal and management of tailings. Here, I explain some key issues regarding water in mining. Many of the world's mines are facing challenges of falling ore grades, which means more material needs to be processed to produce a given tonnage of metal or mineral. This in turn increases the production of tailings, and increases water and energy consumption. In addition, many ores are becoming more complex to treat, requiring more capital intensive and higher operating cost processes. In recent years, there have been catastrophic failures of tailings storage embankments (e.g. Mount Polley, BC, Canada and Bento Rodriguez, Minas Gerias, Brazil). These factors put pressure on mining companies economically and environmentally, and are driving needs for innovation to develop more energy and water efficient and lower risk processing and tailings management alternatives. A key method of reducing water consumption and tailings failure risks for many mines is through more intensive tailings dewatering (e.g. high density thickening or filtration).
For metals, one of the most obvious ways to reduce energy and water consumption is to expand recycling. For example, the energy required to make a tonne of recycled steel consumes less than 20% of that from iron ore. For aluminium, the energy consumption for recycled material is only about 5% of that from bauxite ores. Other metals that are heavily recycled include copper and lead. By understanding the stocks and flows of metals, resource recovery, and water and energy inputs, we can quantify the economic and environmental impacts of recycling. Another key area is reducing the energy used in breaking ores to enable separation. This process, called comminution, includes blasting, crushing, grinding and attrition, and usually accounts for the majority of energy consumed in mineral processing. Comminution energy can be reduced through minimizing ore dilution, separating coarse waste particles out of the ore as early as possible (e.g. ore sorting), selecting the most efficient breakage machine for an ore type and avoiding breaking particles finer than needed to achieve the required separation. Two organizations that are promoting and researching such improvements are CEEC and CRC ORE. In this article, I explain how processing plants can optimize energy use and mineral recovery in comminution and separation circuits. It is also important to understand the interaction between comminution and separation processes such as flotation.
The Sustainable Mining Institute (SMI) has various research programs and industry collaborations to reduce environmental impacts and support social license to operate. Mining Association of Canada also has an initiative, Towards Sustainable Mining, which defines key tools and indicators to manage mining risks in social, environmental, safety and health areas.