They are not showing up in mine electrification economic studies or even mine safety reports, but diesel exhaust nanoparticles shape increasingly as a key driver of hundreds of millions, if not billions of dollars of underground mine electrification investment over the next decade.
The invisible molecules were “the elephant in the room” at the world’s major gathering of mine electrification leaders and technologists, The Electric Mine, in Perth, according to former Newcrest Mining innovation manager, Tony Sprague.
“DPM [diesel particulate matter] has been classified as a class one carcinogen by the majority of major global health advisory bodies. We know it’s a toxin. We know it’s a cancer-causing agent,” Sprague, CEO of consulting firm MasterMined, said at the conference attended by more than 900 people from over 30 countries.
“I think we’re all pretty aligned here on the need to electrify mining for GHG [greenhouse gas] reasons.
“But to me these distant GHG reduction targets are not resulting in the urgency we need to eradicate diesel from our underground mines, from an employee health perspective.
“This lack of attention given to DPM means that we may not be pushing our mining companies hard enough to develop more rapid electrification roadmaps.
“I think it’s also a huge missed opportunity for the industry to really drive more rapid decarbonisation of our underground mines in particular.”
While the major driver of mine electrification highlighted at the conference is economics – with the momentum of a seemingly inevitable shift dictated by how fast accountants and engineers can plug real, competitive costings into final investment decision, or FID, calculations – miners and key service providers such as contractors are increasingly mindful of a changing regulatory environment.
Sprague used data from an Australian gold major showing the potential economic stranding impact of new Safe Work Australia (SWA) DPM exposure limits on otherwise mineable metal, suggesting the data “should be a massive wake-up call for all mining companies that are responsible for putting people into underground mines”.
Northern Star Resources underground group mining engineer, David Trembath, later took ownership of the data.
Participating in a discussion about emerging underground electric vehicle dynamic charging technology being developed in Australia with support from a dozen mining companies, including Northern Star, Trembath said compliance with proposed SWA DPM exposure limits would present significant challenges for the company and its peers.
“We think we’re pretty representative of the industry in Australia,” said Trembath, referring to DPM measurements taken over 18 months at the company’s operations and comparisons between current and future worker exposure levels.
“You can see that would have a massive effect on our mines to comply with that [new] regulation.
“We’re looking [at technologies] that can help us fix the renewable energy mix … and we want a pathway with the regulator.
“The regulator is getting more and more involved in the operation of mines and we want a technology that can have a good, clear pathway through to fruition.
“We need to introduce something that is going to enhance safety not introduce new risks into our mines.
“We want better ventilating air which will be a product of the electrification of our mines.
“If we can get the productivity, low risk, safety and regulator approval, we’re on a winner.”
SWA says diesel diesel fuel combustion generates a complex mix of gases, vapours, liquid aerosols and particulate substances. Fine particles, or DPM, include fine carbon particles.
“Hazardous chemicals known as poly aromatic hydrocarbons adhere to the surface of carbon particles,” the Australian government agency says.
“DPM can act like a gas and stay airborne for long periods of time.
“DPM can penetrate deep into the lungs because of its small size.
“Exposure to diesel exhaust can cause both short-term [acute] and long term [chronic] health effects.”
SWA’s proposed workplace exposure standard of 0.015 milligrams per cubic metre, a time-weighted average over a nominal eight-hour work period, compares with the current 0.1mg/cu.m “accepted” by the mining industry. It has emphasised that recommended exposure standards should not be seen as representing acceptable levels of exposure for workers.
The recent 2024 International Mine Health and Safety Conference in Western Australia heard advanced scanning and analysis technology for micron and submicron-sized particles was also opening up new opportunities to better understand airborne threats to people working around heavy machinery and where mineral and rock dusts were being generated.
“While characterisation studies were attempted in the 1970s and 1980s the step-change in technology now allows a more meaningful level of detail,” University of Queensland research fellow Nikky LaBranche said at the international safety conference.
The new technology was demonstrating that, among other things, traditional exposure monitoring methods were no longer adequate to determine the “full health hazards” presented by ambient particulate matter.
The proposed Australian DPM exposure standard will set a new benchmark that will put pressure on other jurisdictions to follow suit. Canada, another major underground mining country, and the USA have been pursuing stricter exposure limits.
Danie Burger, chief advisor underground technology for Rio Tinto, said at The Electric Mine 2024 heavily diesel-dependent industries such as mining were expecting lower global worker exposure limits for DPM.
“Once we get those limits there’s no way that we can use diesel underground anymore,” he said.
Gavin Mann, principal mining technology at diversified mid-tier miner South32, said: “We expect mines of the future will electrify to meet our industry decarbonisation goals and to realise the health and safety benefits from eliminating diesel emissions underground.”
Like Northern Star, Newcrest (now Newmont), BHP and other miners, South32 is funding R&D on the BluVein dynamic vehicle charging concept for underground and surface mines.
Mann said the technology was exhibiting capital and operating cost advantages vis-à-vis alternatives being developed to improve the economics of battery-electric vehicles versus the diesel incumbents. The benefits were being seen in holistic implementation studies, not just discrete technology comparisons.
He said South32 was investing collaboratively in BluVein “because we can influence dynamic charging infrastructure that is inherently designed for installation in our current excavation profiles”.
“We pay for every cubic metre of rock that we move from underground to create space for our services.
“So to be able to implement technology that can share space in an underground mine, without affecting access to our other services, is going to be a key to successful implementation.
“Also with respect to productivity we believe that electrification is a key enabler for automation.
“It’s a logical progression for dynamic charging to be an enabler for continuous operation … creating a foundational technology for a heavy underground operating model where vehicles only have to stop for planned servicing intervals.”
BluVein CEO James Oliver said the collaborative funding and development model, and wide-ranging technology evaluation approaches, were crucial to faster adoption in mining.
“Diesel is a strong competitor,” he said.
“We’re trying to eliminate a product that’s extremely convenient to use yet creates so much damage in so many ways … to the environment [and] health and safety.
“There is no chance with the technology at this point in time [that] we will compete on a capital like-for-like basis.
“There is an imperative around safety; there is absolutely an environmental consideration here. But at what cost?
“We still need to remain financially viable.
“We need to increase performance to the point where we maintain an ROI. We need to offset higher capex with increased productivity.
“We have worked extremely hard on design to be minimal impact on the additional capital that’s required to move to electrification.
“In this war against diesel we’re all searching for new technologies and BluVein, a dynamic connector of, hopefully, green electrons to moving vehicles in the heavy haulage space, is one.”
Gold Fields strategic project superintendent Tom Murdock said the company was also evaluating newer technologies to complement BEVs and demonstrate an investment case for removing diesel trucks and other equipment.
The world gold major has invested hundreds of millions of dollars already in renewable energy generation in Western Australia and South Africa.
Prefeasibility studies on underground Railveyor and conventional conveyor systems had started to look holistically at the economics of adoption.
“From an economic standpoint, they’re in the realms of breakeven – very similar to what’s been presented by IGO for Cosmos [nickel project in WA],” Murdock said.
“They do however provide significant ESG and OHS benefits, which is something we don’t evaluate well as an industry.
“The triple bottom line evaluation approach is something Gold Fields really should pursue to assign a value to those things and make these investments potentially more attractive.
“I think that’s an important next step.
“The challenge is these projects compete for capital, which is not an unlimited bucket.”
Acting chief operating officer of IGO, Chris Carr, said at the conference the company’s study on the economic feasibility of switching from diesel equipment to BE, which “presented a compelling case to us” for electrification, highlighted current challenges and opportunities in the industry’s push to transition to new generation mobile equipment.
The study could not put any economic weight on safety or environmental factors.
In parallel with the electrification study by mining contractor Perenti and engineering major ABB, IGO completed a project review that cut Cosmos’ expected mine life and pushed up capital and operating costs.
Lower nickel prices have negatively impacted most WA sulphide nickel mines.
IGO put Cosmos into care and maintenance at the start of 2024.
“Electrification was not a factor in that decision,” Carr said at The Electric Mine.
A whitepaper summarising the study results, “Making electrified underground mining a reality: Lessons from the Cosmos Electrification Study”, concluded replacing diesel underground mining vehicles with a battery electric fleet was now “technically feasible and will increasingly be a key technological enabler for mining companies to achieve their decarbonisation goals”.
Perenti and ABB said a combination of actual and projected battery electric vehicle cost and performance data indicated BEV fleet available to the Australian market could match the productivity of mature diesel equipment.
They also found estimated costs to electrify Cosmos’ modest underground fleet were not prohibitive over the planned mine life, “even based on conservative productivity and cost assumptions”.
IGO wasn’t going to obtain full benefits from optimised ventilation and other infrastructure design due to sunk investment in the mine prior to its acquisition of the asset in 2022, Carr said.
The study identified gaps in available BEV operating and maintenance direct and indirect cost data due to the formative stage of equipment, battery, charging and support system development relative to entrenched diesel models.
It also highlighted significantly longer delivery times for battery-electric equipment than diesel models.
“We hope this is not prioritising diesel units to make more money,” Carr said.
“This is slowing adoption.”
However, Carr said at the conference none of this would stop the march of EVs into traditional diesel territory.
The improving cost profile of EVs and the market pull created by industry decarbonisation goals were not the only drivers.
“In five-to-10 years we’ll all be electric and be wondering what all the fuss was about,” he said.
“The cost differential of an all-electric mine presented a compelling case to us.
“We also believe the decision to electrify should include the safety case and the harder to quantify but nevertheless real benefits of the ESG case.
“The decision to electrify should be made on the combined basis of safety, ESG and economics.
“The economics is the hardest one right now.
“But safety ought to be enough on its own.
“We are already convinced of the safety case of eliminating DPM and reducing noise and vibration, and the ESG case of reduced carbon emissions.”
