Demand for copper is at an all-time high and looks set to continue because of increasing demand for hi-tech lifestyles and the growth of urbanization. The global focus on switching to renewable energy sources and electric vehicles to meet 2015 Paris Climate Agreement targets also increases demand for copper. Pressure is simultaneously mounting on the copper mining industry to move towards more sustainable methods of extraction and change how waste is processed. Solar energy is being investigated to produce power and heat for copper mining processes to lower the industry’s carbon footprint.
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Copper Use and Environmental Consequences of Copper Mining
Copper is one of the most abundant nonferrous metals in the Earth’s crust. It is attractive to use across a vast range of industries because of its properties; workability and durability, electrical and heat conductivity. It is also anti-bacterial and recyclable.
Applications for copper include renewable energies; solar and wind turbines, electric vehicles and batteries, as well as industries such as manufacturing, electronics, engineering, plumbing and heating, jewellery and other decorative purposes.
High amounts of water and fossil fuels are consumed for mining and processing ore, which also generates huge amounts of waste.
Dam and pond systems called tailings store wastewater and acid mine drainage (AMD), which frequently creates pollution and human health hazards by poisoning rivers, streams, and agricultural land, when damn systems fail or overflow.
Chile Copper Mines Energy Use and Solar Energy Potential
Chile is the highest copper-producing country in the world. The Atacama Desert in Northern Chile also receives the most solar radiation in the world, so is ideal for solar farm projects.
Copper mining is energy-intensive. Crushing and grinding processes produce the most carbon emissions. The falling copper grade of ore as resources are depleted means more fossil fuels are burned as more ore is extracted in search of copper. Demand for copper is growing six times faster than production, and that requires even more energy.
High Demand for Water Requires Innovative Technology
Mining uses a lot of water for plant machinery and drills, and in refining processes.
Wastewater is continuously pumped out of excavated spaces, which are sometimes vulnerable to flooding. Mining usually occurs beneath ground, which is lower than the water table. Water that seeps from sulfur-bearing rocks oxidizes in the presence of air and produces sulfuric acid and dissolved iron. This chemical process is accelerated by certain types of bacteria found in the mine shafts. The acidic run-off, AMD, contains heavy metals, including copper, lead, and mercury.
Wastewater and AMD are traditionally stored in tailings. However, there is now increasing interest in re-using this water as mining in Chile has depleted natural aquifers and water is becoming scarcer, made worse by a drier climate caused by climate change.
Economic Cost for Transitioning to Solar Technology
Energy for copper mining is required using electricity, heat, and fuel, the cost of which is high, representing around 25% to 30% of total operating costs.
Electricity demand is anticipated to increase by 60% by 2025. Urgent actions are needed because the rises in demand also mean a rise in burning fossil fuels, and therefore the exact opposite of tackling climate change.
Research has shown that replacing fossil fuel energy from the grid with Concentrating Solar Power (CSP) in mining’s future energy mix, when combined with Solar Photovoltaic (PV) has a significant impact on lowering greenhouse gas emissions.
A drop in price has been seen in solar technologies as more are developed and invested in. In turn, this means further investment in solar power projects for mining use, particularly in the Atacama Desert, makes economic sense for private investors.
Water Crisis Solved Through Investment in Solar Technology
Investment in solar power for copper mining lowers greenhouse gas emissions and could tackle water scarcity.
Seawater is being increasingly used as a solution to meet water demands, but desalination plants are expensive to run and transportation costs are high because of elevated altitude mine locations.
Solar energy offers a practical solution for both desalination and transport. Researchers have calculated water could be transported over distances of 100 km to 200 km, to altitude differences of more than 1500 m.
Solar pumping could also be designed to maximize efficiency centered on intensified use during the day.
Copper Ore Hydrometallurgy Process using Solar Technology
Hydrometallurgy processes treat copper ore using dilute solutions of sulfuric acid to produce copper sulfate. The copper is then recovered through electrolysis.
The processing of copper ores requires electricity, fuel, heat, water and oxygen and other chemical agents.
Solar technologies such as PV, are useful for creating electricity and heat for processing copper ore and can be installed for small- or large-scale mining operations.
There are also solar thermal collectors, which use flat plate and parabolic trough collectors to concentrate solar rays. These can be used to create solar furnaces, capable of reaching temperatures of 300 ˚C, providing all the heat required for processing copper ore.
Hybrid solar-PV-Thermal (PV-T) technologies combine thermal and PV collector technology, which individually are commonly used for domestic use. When combined, they have high potential for the copper mining industry.
Off-the-shelf PV technology is low cost and provides a simple solution for mining and mineral processing.
However, there are also further opportunities to provide PV energy which can be integrated into different mining processes cost effectively, and more efficiently.
Electrolysis based on PV electro-refining and electro-winning, are high-energy processes in copper production, whereby the currents generated rely on large transformers and high-power rectifiers.
If PV is incorporated into existing electro-refineries, it becomes more efficient to feed PV energy directly into a renewable energy plant using a single DC-DC conversion stage, reducing the number of converter and conversion stages.
This technology is not yet available commercially, but it has been tested and developed for use when required.
PV can also be used for pumping water, either to extract wastewater or transporting seawater.
PV might also provide an opportunity to improve tailings management and water recovery by pumping it from tailings dams to copper refineries. Because it can be placed on the dam’s surface, it may reduce engineering costs.
In conclusion, all solar-powered copper mining can be achieved using innovative and adaptable technologies that can be fully integrated into existing ones.
Solar technology comes with high economic benefits, as well as environmental ones. It can contribute to greenhouse gas reductions in the longer term for the mining industry, which will need to happen if the global drive to solve the climate crisis is to be realized.
References and Further Reading
The use of solar energy in the copper mining process: A comprehensive review (oct 2021) Behar.O, Pena.R, Kouro.S, Kracht.W, Fuentealba.E, Moran.L, Sbarbaro.D in Elsevier Cleaner Engineering and Technology Volume 4 Journal in Science Direct online https://www.sciencedirect.com/science/article/pii/S2666790821002196
The Paris Agreement (2015/16) in UNFCCC online https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement
C4. Biotechnical tools for Remediation of Acid Mine Drainage (removal of metals from wastewater and leachate) (2018) B.Dhir in Elsevier online in Science Direct https://www.sciencedirect.com/science/article/pii/B978012812986900004X