Until recently, net zero mining was considered an impossibility. What a difference innovative engineering makes.
The challenges of decarbonising the mining sector, currently responsible for four to seven per cent of the world’s carbon footprint, have long been considered too technically difficult to solve.
But as engineers have thrown themselves at the task, solutions have started to appear. Some are now being implemented, others are in testing and more are in design. Most experts now agree that net zero mining is not just possible but inevitable.
Some in the industry are leading the way with bold claims. Bellevue Gold, with a mine powered by wind, solar and thermal and firmed up with battery storage, is looking to produce net zero gold by 2026. Fortescue is targeting net zero emissions by 2030.
Mining engineer Clare Larkin-Sykes, Managing Director of Forelight Advisory, said while green mining is ambitious and costly, it is the future.
“From a purely commercial perspective, a current existing mining operation already has capital sunk into it,” Sykes said. “So, what is required is a rethink about how those structures already in operation can be repurposed to accommodate a net zero future.”
That involves better understanding the ore body in the ground, so miners only extract what they need to, minimising waste. It also requires renewable energy to power mining processes.
Mineral processing practices and technologies will need to change, and diesel use in machinery must be phased out through electrifying equipment and vehicles.
And that’s all before the sector develops ways to help mitigate scope 3 emissions, previously considered outside its control.
Mining in Australia, according to the Renewable Energy in the Mining Sector paper from the Australian Renewable Energy Agency (ARENA), consumes around 500 PJ annually, or 10 per cent of Australia’s total energy use.
That energy comes from:
Diesel
Natural gas
Grid electricity
Other
In coal mines, the most energy-intensive processes are comminution, or crushing and grinding, as well as vehicles and machinery. Mine ventilation also requires a significant energy feed.
This energy will continue to be required, renewable or not. To meet Paris Agreement deadlines, copper alone must be mined at a previously unimagined rate. According to Professor Michael Goodsite CPEng EngExec, that decarbonisation goal will only be achieved if we mine more copper in the next 25 years than has been mined in the history of mankind.
Other environmentally critical minerals, including lithium, cobalt, manganese, nickel and graphite, are also required in greater volumes than ever by green technology manufacturers.
The greening of mining will require what was once considered an engineering miracle and, with leading miners already making bold claims about their net zero goals, that’s just what engineers are set to deliver.
Electric vehicles
Numerous EV options are being tested in mines across Australia for everything from people movers to mining trains.
Fortescue’s iron ore hauler, the Infinity Train, is famously being designed to charge its batteries via regenerative braking on the way downhill and under heavy load, to the port. It will then return empty, powering itself back uphill and never requiring external power.
This all requires research, investment and innovative engineering. For example, battery-electric vehicles (BEVs) set to work underground have faced extra challenges around safety, according to engineer Murray Timpson, Director of Slam Engineering.
“It’s about making sure the battery doesn’t create a spark or a fire, or heat that can result in a fire,” Timpson told create.
Timpson references the Ampcontrol Intrinsically Safe battery management system used by DRIFTEX, the world’s first IECEx (International Electrotechnical Commission System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres) Group I-certified electric vehicle. The DRIFTEX vehicle boasts a methane monitor shutdown system, data logging, lower sound levels, and battery charging flat-to-full in 10 minutes, and will run in conditions from -35°C to more than 50°C.
“Diesel engines that operate underground are explosive-protected and flameproofed, and have been designed over decades,” Timpson said. “Batteries are a new technology and unknowns cause concern.”
Engineer Ben McGarry, Principal Decarbonisation at Aurecon, said the technical challenge around getting energy on board is enormous.
“One of the ways you can deliver energy to a moving vehicle is via an overhead powerline system, providing dynamic charging to an onboard battery,” McGarry says. “But blanketing an entire mine with fixed overhead infrastructure is impractical and costly, so you have to plan carefully.”
In the Pilbara, Rio Tinto and BHP are collaborating on the testing of large, battery-electric haul trucks using various static and dynamic charging systems.
Some mines are utilising vehicles with batteries that last a full eight-hour shift, such as Komatsu’s first-generation lithium iron phosphate hauler battery, a 240 V, 160 kWh, 7500 kg system that operates for eight hours on a single, two-hour charge.
Others are opting for a “mosquito fleet” of more nimble trucks that are simpler to maintain and require less road infrastructure. There are also EVs that utilise battery swapping stations, which enable instant refuelling but require greater external infrastructure.
A study by Perenti, IGO and ABB confirmed the technical feasibility, at non-prohibitive CAPEX and OPEX, of an all-electric underground mine fleet on the Cosmos Nickel Project in Western Australia.
It also found that “a BEV fleet would enable a significant reduction in cooling and ventilation demands, which would offset the additional power required by BEVs”.
Energy solution
Within the next couple of months, Bellevue Gold will have the ability to run its entire operation on renewables alone. In doing so, it will become the first Australian mine to boast true engines-off capacity, according to Darren Stralow, Bellevue Gold’s Managing Director and CEO.
As well as striving to have the lowest total Scope 1 emissions of any major Australian mine, the goal for Bellevue is to be able to sell its green gold for a significant price premium.
Stralow faced a choice of a high-thermal solution, which has lower capital costs but higher operating costs over the life of the mine, or an energy solution that costs more up front but provides lower operating costs.
“With our long mine life, we have gone for the second option and built a high-renewable energy power station,” he said. “It’s going to be over 80 per cent renewable energy penetration into the mine grid when measured over a 12-month period. That’s solar, wind, thermal and batteries.”
This has been achieved through a power purchase agreement with Zenith Energy Operations, which has constructed the power station.
Larkin-Sykes said such a partnership is usually essential for the success of net zero mining.
“Most mines don’t have the luxury of access to grid power,” she said. “At the same time, miners typically are not in the business of power generation. Collaboration and partnership are key.
“Then, the challenge for miners is to explore different models of operation where those power demands can be managed more effectively to match renewable energy supply.”
Bellevue Gold is doing just that – adjusting its operations to maximise electrification by matching renewable energy generation periods. This includes conducting regular maintenance on their oversized crusher during shoulder periods – dawn and dusk – when there is less wind and solar.
McGarry said this operational flexibility will become increasingly relevant as more renewable generation is introduced to mining.
“When the wind is blowing and the sun is shining, you can get away with extremely low energy costs,” he explained. “Conversely, when it’s still and dark, energy could be eye-wateringly expensive.
“So, whoever decides to simply not have to use energy for those 10 hours a year when it’s expensive, and who therefore doesn’t need to build the infrastructure to serve that peak 10 hours, can save material amounts of money.”
Ventilation
The Perenti/IGO/ABB study, Making electrified underground mining a reality, analysed the ventilation design changes enabled by an underground electric fleet as opposed to a diesel fleet at IGO’s brownfield Cosmos nickel mine.
“Cosmos is unique in the Australian underground mining scene because it actually has a shaft,” Darren Kwok, Perenti’s Head of Mining Electrification and Technology, said. “The number of trucks was a lot lower at Cosmos than at another decline mine.”
The mine’s total power consumption with a fully electrified fleet was less than that of the equivalent diesel operation due to the substantial power savings in cooling and ventilation.
“The health and safety benefits of an electric mine also shouldn’t be undersold,” Kwok said. “We are seeing vast benefits when it comes to electrification underground related to vibration, heat and tailpipe emissions as a health and safety consideration.”
Interoperability
Electrification is also set to deliver further sustainability by enabling new control and automation systems that optimise operations in ways never before possible.
Since 2019, the University of Western Australia’s ERDi I4.0 Testlab has been coordinating efforts by more than 20 miners, technology partners, government entities and training organisations to help validate open-process control systems using international standards. The effort has already been instrumental in major advances, such as helping Gold Fields’ Granny Smith mine become one of the most digitally connected mines in the world. The Western Australia gold mine’s new ISA-95-aligned operations management system allows real-time connectivity between workers, fleet and plant, significantly boosting efficiency.
Key findings from the Making electrified underground mining a reality study:
- Significant cooling requirement reductions, with bulk-air cooling plant capacity reduced from six MW to 4.5 MW
- Cooling required over two months annually, instead of five
- Smaller 45 kW auxiliary fans could be used for secondary ventilation, compared to 55 kW fans, increasing blast fume clearance times by just two to five minutes.
- For a greenfield mine, the implementation of an underground electric fleet represented CAPEX and OPEX savings, including savings to primary airflow volume.
Hoists and conveyers
ABB Global Head of Mining Max Luedtke said their daily focus is on electrification and automation.
Vehicles are the low-hanging fruit, he said, as is the other machinery required to move things, particularly hoists and conveyers.
“There are now more energy-efficient motors and ways to design a mine,” Luedtke said. “A lot of mines in the past were over-designed because miners were not looking at electrification.”
But the electric mine won’t just make deep ore extraction more sustainable, it will also enable automation, optimisation and remote management of machinery.
Remote management capabilities, in turn, help to solve the talent challenge being faced by the mining sector globally.
“We developed a plant in Chile, at nearly 5000 m altitude and 1000 km from Santiago,” Luedtke said. “But they manage much of it from an office building in the city, where engineers are happier to work and, in this office, 50 per cent of the engineers are female.
“That sustainability and diversity is only possible if you design the mine the right way.”
Case Study: BHP’s Prominent Hill mine
Cost of operation at the Prominent Hill copper, gold and silver mine was rising fast as trucks hauled ore from deeper underground. The mine was set to become uneconomical by 2033.
A major part of the solution is a powerful electric hoist capable of lifting almost 40 t up a 1300 m shaft in just 90 seconds. Expected to be operational by late 2025, the hoist is the largest and most powerful in the country, and will enable double-digit increases in productivity and similar decreases in operating costs and emissions.
Large sections of the plant are also being engineered and fabricated in Australia.
The savings come not only from the efficiency of electric motors compared to diesel engines (>90 per cent compared to 35 per cent), but also the fact that, while haul trucks must generally traverse at least seven horizontal metres for every vertical metre climbed, hoists pull straight up.
Hoists can also operate autonomously, according to Aaron Trueman, ABB’s Business Line Manager for Hoisting in Australia. When powered by renewable sources, they emit zero emissions, and can provide a dual purpose as a ventilation shaft. Adding to their sustainability CV, hoists are also the safest and most efficient way to transport people, equipment and materials underground.
The engineering has not been without challenges, chiefly the sinking of the shaft. That shaft provides access to new areas of mineral reserves unserved by the current trucking plan, boosting production by 30 per cent, to 6.5 million t a year.