A high-level study into mining energy use for the key mineral commodities of the future.
Marc Allen, Technical Director, engeco
Report commissioned by The Weir Group PLC
The mining industry plays a critical role at the heart of modern global economy, extracting and processing a wide range of minerals that are essential for economic development and human progress.
As a primary industry producing essential resources, mining supports some of the biggest structural trends in our world from population growth to urbanisation through to decarbonisation. Metals such as copper, nickel, steel, and lithium are core components of electricity transmission and storage, electric vehicles and renewable energy infrastructure. The industry therefore has a crucial role in supporting the transition to net zero emissions that is required to limit global temperatures in line with the Paris Agreement.
Mining faces a challenge however: how to provide the essential resources the world needs while reducing its own environmental impact? In essence, mining needs to become more sustainable and efficient. This report seeks to support a more comprehensive understanding of the scale of that challenge by focusing on where energy is consumed in mining and minerals processing. It identifies opportunities for innovation and improvement that will in turn make a significant contribution to the world’s carbon transition. Although 60% of total energy is estimated to be consumed in mining equipment, this category covers a very wide variety of different equipment. Comminution, consuming close to 40% of total energy contains a single piece of equipment—the grinding mill—that is typically the largest single consumer in a mining operation.
Noting that the comminution area also includes crushing, pumps and other equipment—the grinding mill(s) are normally the largest single energy consumer.
This report quantifies energy use in five commodities: copper, gold, iron ore, nickel and lithium. Bringing together mine energy use data from more than 40 published studies (each of which references dozens more studies and hundreds of mining operations) from 2007 to 2020 into a single narrative, the report aims to build a more comprehensive understanding of energy use in the mining industry. In order to obtain an understanding of the impact of energy use in the mining industry, a literature survey has been completed exploring energy usage in some key commodities. Information has been collected that examines total final energy consumption in copper, gold, nickel, lithium and iron ore. The study has focussed on minerals processing that involves comminution and either concentration through flotation or leaching. Pyrometallurgical processes such as smelting have been excluded from this study as the energy profiles of those industries are very different to the processes in this study. Both mining operations and processing have been explored with calculations that show the split of final energy consumption in mining vs. processing. These broad areas were then further split into energy used in mobile equipment and ventilation for mining, and into comminution and other processes for process plants.
Across the commodities in the study, an average energy intensity per commodity was calculated. As these were calculated in differing units (i.e. GJ/tonne of ore, GJ/t of product etc.), all intensities were converted to tonnes of copper equivalent. This metric is commonly used in the industry to provide a common measurement across different minerals. Tonnes of copper equivalent is determined from the ratio of market prices for each of the commodities.
From the breakdown of energy consumption, it was found that comminution accounts for 25% of final energy consumption of an “average” mine site. Diesel in mobile equipment accounts for 46%, electricity in mining (ventilation) 15% and other electricity 14%. These are averages based on the different splits of energy consumption that were calculated for each of the commodities and the total energy per commodity. That is, the absolute energy consumption in each area for each commodity was calculated and the percentage splits in the chart below were derived from that. Comminution is typically the single biggest user of energy in a mine site as diesel in mining operations is split across multiple different equipment types and comminution is only a small number of unit operations—this makes comminution a natural target for identification of energy savings opportunities able to have the largest impact.
Using the current production rates of the commodities in question, and the energy intensities for each of the commodities, a total of 1,68 EJ/a (1,680,000,000,000,000,000 joules per year) has been calculated. This is approximately 0.5% of total final energy consumption globally. Published information indicates that the entire mining industry consumes approximately 12 EJ per year—or 3.5% of total final energy consumption globally. Using the energy splits from the above chart, the process of comminution may use up to 1% of total final energy consumption globally—equivalent to the power consumed by 221 million typical UK homes1.
As comminution circuits have been shown to be largest single consumer of final energy for hard rock mining operations, using one quarter of the total final energy in mining, small improvements in comminution technologies can lead to relatively large savings in both energy consumption and GHG emissions. For example, a 5% incremental improvement in energy efficiency across comminution could result in greenhouse gas emissions reductions of more than 30M tonnes of CO2-e2. Primary energy, that is—energy that is combusted directly to drive mobile equipment or generate electricity—was also explored in this study by analysing different ways in which mine sites may generate or purchase electricity. Using a typical power generation efficiency of 35%, comminution may use up to 3% of primary energy globally.
This study has shown that the mining industry is a significant user of energy overall. To meet the challenge of decarbonisation it is clear the industry needs to evolve, and that this will require a transition from legacy systems and processes to new more efficient and sustainable technologies.
There are a number of significant opportunities available to the minerals industry to reduce its energy consumption. These involve optimisation, big data and artificial intelligence, replacement of traditional comminution equipment with new technology, preconcentration and others. In addition, if zero emissions energy sources are deployed for mobile and stationary equipment—e.g. renewable energy, energy storage and alternative fuels—then the mining industry may well be able to achieve zero emissions, or close to it. Leaving a relatively small role for offsets and carbon credits to play. Opportunities that are focused on comminution circuits, as the single biggest user of energy in a mining operation, are considered to be high priority as small improvements can have a large impact on overall site energy and emissions. Also of note are any opportunities that reduce or eliminate grinding media—the import of which into a mining operation carries with it embodied emissions to manufacture the steel balls. Although these are indirect emissions for a mining operation, they are important in terms of overall impact of the industry and increasingly the subject of study.
Against a background of robust demand fundamentals, the mining industry remains central to future economic development globally, with some critical minerals enabling the low-carbon transition required in the rest of the economy. But the environment in which it will operate in future will be very different from the past, requiring change and investment to preserve its licence to operate.
This report illustrates the globally significant scale of energy use across the industry and the potential for it to use new technologies to make improvements to its own environmental impact and the global effort to reduce carbon emissions. Based on average electricity consumption of 3,769 kWh/a for households in the UK in 2018 (statista.com) 2 Based on diesel combustion to produce electricity with an efficiency of 35% - actual emissions reductions vary depending on electricity source
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