Reducing mining waste as Australia transitions to renewables

19 July 2022 Consultancy.com.au 4 min. read
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As Australia makes the transition from fossil fuels to renewables, demand for mined minerals will increase during the transition. This will trigger some short-term pain for sustainability objectives – although much of this pain could be mitigated by technology, writes Jan Kwak, Managing Director of Australia and Asia at engineering consultancy Hatch.

The demand for mined minerals is driven by the increased infrastructure needed to provide renewable energy. This includes solar panels, battery storage and wind turbines.

Essentially, the long-term gain of renewable energy will require some short-term pain in the shape of more intensive mining activity. This will have the added consequence of producing additional mining waste, known as tailings.

Estimated Global Tailings Production 2010-2018

Australia is one of the world’s largest producers of these six common commodities: copper, gold, nickel, iron ore, coal and bauxite. Copper, nickel and gold are critical for developing solar panels, wind turbines and battery storage, while iron ore, coal and bauxite are used to produce the steel and aluminium needed to build renewable energy infrastructure.

The International Energy Agency’s ‘Net Zero by 2050’ report forecasts that by 2030, the consumption of lithium and cobalt will rise by sixfold, nickel will increase fourfold, and copper twofold.

In the mining process, these minerals must be separated from waste rock (or ore), leaving crushed rock and fine particles in water, which has the potential to damage the environment by releasing toxic metals, causing erosion or sinkholes and/or contaminating soil or water supplies.

According to analysis by Hatch, between 2018 and 2010 tailings production of these six commoditiesincreased, on average, by 40% – from 6.7 billion metric tonnes to 9.4 billion metric tonnes. Iron ore tailings had the largest change, increasing 100%, while coal tailings only increased by 6%.

Global Nickel Mining

When looking at ore and deposit types, 65% of copper tailings is produced from chalcopyrite – the most common copper ore mineral – and 91% of porphyry deposits. Half (53%) of gold tailings is produced from sulfide deposits, and 37% of nickel tailings are from penlandite (an iron-nickel sulphide mineral) deposits.

The analysis also revealed that thermal coal produces 88% of coal tailings compared with 11% of metallurgical coal and less than 1% of pulverized coal injection.

Possible solutions

While this may seem alarming, solutions are available. The Hatch analysis revealed that the capability to reduce tailings by 20 to 30 percent is already available, using techniques such as spectral imagining, quantitative mineralogy and data analytics. The report also identified that in the next 10 to 20 years, by integrating these technologies in future projects or expansions, there is the opportunity to reduce tailings by more than 50 per cent.

'Today' and future potential tailings reduction by commodity

Minimisation of tailings is most effective further upstream in the mining process, with geological definition, fracturing, and mining technologies.

The next best approach is to reduce tailings in the concentrating and refining stage of processing. Once tailings are produced, it is incumbent on the industry to improve waste management practice and ensure safe storage.

By assessing when each technology can begin to be utilised, the potential gain with future development if it reaches a full commercialisation, and the tailings reduction potential of the technology at that advanced stage, Hatch’s report puts forward a roadmap for reducing tailings for those six commodities.

Technology development status and impact

The roadmap reveals that bulk ore sorting, advance particle sorting, fragmentation, and In Situ Recovery technologies have the highest potential impact on tailings reduction for base and precious metals, such as copper and gold. In relation to bulk materials, such as coal and bauxite, bulk ore sorting and continuous mining machines technologies present a higher impact in tailings reduction.

Understanding tailings

Identifying how tailings are produced is critical to establishing the right solutions to reduce and eliminate them. For example, in copper mining, 90 per cent of global activity is through open pit mining. As this is generally a less selective mining method, it produces a significant volume of tailings.

Global Nickel Mining

But by using the aforementioned available technologies, tailings from copper mining can be reduced by up to 30 per cent in the short term, and up to 70 percent in the longer term, once those technologies are incorporated into new mining sites at the outset.

While technology implementation requires a ‘site-by-site’ evaluation, and the effectiveness of tailings reduction processes and technology depends on the specific ore mineralogy, orebody characteristics, cutoff grade, mining method and other economic factors, it is imperative that the industry looks to incorporate more technologies to reduce mining waste as the transition to renewable energy ramps up and demand for resources increases exponentially.