Big decisions for heavy vehicle fuel

It must be green. But it also needs to be lean. That’s the challenge facing Australia’s mining industry when weaning its enormous iron-ore hauling trucks off diesel.

BHP spokesman Brandon Craig says the fossil fuel contributes about 40% of the multinational mining company’s greenhouse gas emissions. And that’s a significant hurdle to the company’s net-zero ambitions by 30% before 2030.

Alternatives are available. But industry analysts say not all green fuels are created equal.

BHP doesn’t think hydrogen fuel cells or electric battery systems are up to powering its hauling fleet. Yet.

“Ultimately, our aim is to have fully electric trucking fleets at our sites, but alternative fuels like HVO (Hydrotreated Vegetable Oil) may help us reduce our emissions while the electrification transition takes place,” Craig says.

HVO is a liquid biofuel made from processed vegetable material, such as rapeseed, sunflower, soybean, and palm oil. Animal fats can also be added to the mix.

It can be blended with diesel or used in its pure form.

That’s why BHP is experimenting with HVO at its Western Australia Yandi iron ore mine. The BP-produced biofuel is undergoing a three-month trial period powering haul trucks and mining equipment.

But the use of biodiesel as a stop-gap green fuel by BHP is indicative of a broader problem facing heavy machinery operators.

Market forces

The passenger and light commercial markets appear to be voting with their feet.

The world’s second-largest passenger car manufacturer, Volkswagen, announced earlier this month that it was abandoning hydrogen and would instead focus on all-electric vehicles (EVs).

Sales of EVs already far outstrip the hydrogen competition. About 3000 hydrogen fuel cell cars were sold in the United States last year, compared to 807,000 fully electric cars.

But the future of the heavy commercial and industrial market remains less clear.

Andrew (Twiggy) Forrest, the Executive Chairman of Fortescue Metals Group, has been a vocal advocate for building a new global hydrogen fuel network.

In 2021, the company’s research arm began the conversion of an older 221-tonne hauler truck into a hydrogen fuel cell prototype. The 180kW system and its 300 kWh battery will undergo testing in WA’s Pilbara region this year.

The company has also just taken delivery of a new all-electric vehicle battery system that will be used to power a 240-tonne mine truck also operating in the Pilbara.

“It is a massive achievement that has been completed in record time and marks several firsts for an electric mining haul truck battery, with energy storage of 1.4MWh, the ability to fast-charge in 30 minutes and capacity to regenerate power as it drives downhill,” a company statement reads.

“This system is the first of many technologies that can help enable Fortescue to realise its industry-leading 2030 net-zero target.”

But hydrogen’s hopes haven’t evaporated.

An Australian Renewable Energy Agency (ARENA) renewable hydrogen demonstration project is testing the cost-effectiveness and energy efficiency of hydrogen fuel cell heavy vehicles in Townsville.

The $12 million project supplies five 140-tonne hydrogen-electric trucks to operate alongside their diesel-powered cousins at the Korean-owned Sun Metals zinc refinery to haul zinc concentrate and ingots between the refinery and the port.

ARENA estimates this will eliminate 1300 tonnes of carbon dioxide emissions for each of the two years of the experiment. But the fuel cell vehicles’ performance, maintenance and logistics will also need to be commercially competitive.

And that, analysts argue, is where the true value of all-electric drive systems lies.

By the numbers

When it comes to heavy industry, finding replacement green fuels has turned into a two-horse race. On one side is the effort to improve hydrogen efficiencies and reduce associated infrastructure costs. The other is finding cheaper battery materials that hold more charge for longer than lithium-ion.

Biodiesel

This is the most powerful fuel source once inside a vehicle’s fuel tank, carrying about 10 kWh of energy in every litre.

That’s roughly seven times that stored in an equivalent weight of lithium-ion batteries.

But more than two-thirds of diesel’s output is wasted as heat and noise.

While the source of much excitement in the early 2000s, biofuels have recently taken a back seat in the green energy race. Global debate over whether source crops would be better used as foods has taken much of the shine off its carbon-balancing credentials.

And it still needs the same energy-intensive – and therefore expensive – global storage and distribution network as its fossil fuel cousin.

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Also in Cosmos: No simple fix for mining companies searching for renewable energy

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Hydrogen

While 1kg of compressed hydrogen gas contains about the same energy as 3kg of diesel, it requires about four times more storage volume and needs significantly larger and heavier reinforced fuel tanks.

About 50% of its energy output is lost during combustion. But it also needs four times more wind and solar to produce than an energy equivalent in electricity. The hydrogen must first be separated from water, cooled, pressurised, transported and stored via a wholly new and specialised distribution network.

Liquefied hydrogen has the highest raw energy density. But it must be stored and maintained at below -253C over and above its compressed form.

Batteries

Recharging a battery needs only a nearby renewable electricity source. And electric motors convert about 85% of the energy they consume into productive motion.

But battery packs carry the least energy for their size and weight once in a vehicle. As a ballpark example, it takes a 20 tonne lithium-ion battery to deliver the same energy as a 1000-litre diesel fuel tank.

The equation is made more complicated by the need to manufacture and transport dead battery replacements.