Rio Tinto has completely switched heavy machinery at its Boron mine in California from petroleum-derived diesel to renewable diesel, or hydrotreated vegetable oil (HVO), making it the first open pit mine in the world to reach this milestone. Rolls-Royce is supporting the mining company in its endeavor and has been testing mtu engines on HVO in haul trucks and wheel loaders since 2022. During the 2,000 hours of operation to date, Rio Tinto found that the engines running on renewable diesel deliver similar performance and reliability to traditional diesel.

The switch to renewable diesel at the Boron mine is expected to reduce CO2 by up to 45,000 metric tons per year, equivalent to annual emissions from about 9,600 cars.

Close cooperation between Rio Tinto, Rolls-Royce and Neste led to the success, explained Sinead Kaufman, CEO, Rio Tinto Minerals. “This is an excellent example of what happens when internal and external partners collaborate toward a carbon reduction goal,” Kaufman said. “Support from the state of California has also been incredibly important, as without their vision, this would not have been possible.”

“The conversion of the first open pit mine to HVO is an important milestone,” said Cobus van Schalkwyk, director global mining for Rolls-Royce Power Systems. “With further sustainable offerings, such as reman or re-motorization solutions for vehicles or microgrids for energy supply, we are ready for the further future decarbonization at the mines.”

The initial trial to convert a Borax haul truck to renewable diesel was conducted in collaboration with fuel manufacturer Neste. Rio Tinto U.S. Borax used Neste MY Renewable Diesel during the trial. Neste MY Renewable Diesel is made from sustainably sourced, 100% renewable raw materials such as waste cooking oil and animal fat waste and can reduce greenhouse gas emissions by up to 75% over the lifecycle of the fuel compared to conventional diesel. The results of the trial showed that a haul truck powered by mtu engines running on renewable diesel had similar performance and reliability to haul trucks running on conventional diesel.

Other benefits of renewable diesel include clean combustion with a reduction in particulate emissions of up to 40% in mobile applications and a reduction in NOx emissions by an average of 8%. HVO is a drop-in fuel, according to Rolls-Royce, which means that the existing diesel plant infrastructure can be used unchanged for its use, and no engine hardware or software modifications are required.