BINGHAM CANYON — Over the last decade, Rio Tinto Kennecott — home to the world's deepest open-pit mine — has made tremendous progress in reducing its carbon footprint.

Kennecott shut down its last coal-fired power plant in 2019, removing 6,000 tons of pollutants from the air shed in the Salt Lake Valley.

To continue this momentum, the mining giant announced on Tuesday a complete conversion from conventional to renewable diesel for the mine's entire fleet of 97 transport vehicles and heavy machinery equipment across the mine, concentrator, smelter, refinery and tailings sites.

After a seven-month trial period, the full switch is expected to reduce the mine's emissions by 450,000 tonnes – the same reduction as eliminating the annual emissions of over 100,000 cars.

The switch will also reduce PM2.5 emissions (particles less than 2.5 microns) from the tailpipes of the company's truck fleet by 40%.

With the decommissioning of the coal-fired power plant and the recent switch to renewable diesel – along with the installation of a 5-megawatt solar farm and the use of electric vehicles for underground copper mining – Kennecott has reduced its overall carbon footprint by more than 80% compared to Levels 2018.

“This is a big change,” said Clayton Walker, chief operating officer of Rio Tinto Copper. “I think this is just another step in showing our commitment to making the environment the best it can be and showing how we can do that in a responsible way.”

During the test run of the renewable diesel program, the company compared the acceleration, cycle time, fuel consumption and engine inspection reports of dump trucks and found that renewable diesel is a good replacement for conventional diesel.

The vans aren't small either, often weighing over a million pounds and featuring 1,400-gallon fuel tanks.

“It’s like moving a house,” said Aaron Clement, a Kennecott handyman and truck driver. “You don’t have a lot of visibility. It’s definitely an experience.”

Clement said the switch to renewable diesel has not resulted in any loss of performance in the operation of the dump trucks.

“It’s pretty much identical. Maybe smoke a little less,” Clement said.

Utah Gov. Spencer Cox was present for the announcement and said his trips to Kennecott typically coincide with big announcements like Tuesday's.

“This is a great model. Companies are doing things like this all over the valley and state,” Cox said. “We will never be able to solve some of our (environmental) problems through regulation, but we can certainly free ourselves through innovation, and these are the types of innovations that make sense. “It saves money and improves the environment.”

He said Utah residents can expect more announcements before the upcoming legislative session about how to produce more energy while “treating the environment in a way that is good for everyone who lives here.”

Renewable diesel is made from soybeans, animal fats and cooking oil, making it much cleaner than traditional fuel sources. It is also sourced from the United States, which Walker said is important to the company.

“There was no source of renewable diesel locally here, so our question was, 'How do we get it?'” Walker said.

Steven Ledbetter, executive vice president of HF Sinclair – the company that supplies Kennecott with renewable diesel – said the transportation is via pipeline, further reducing emissions associated with transportation by trucks carrying the fuel .

With further emissions reductions on the horizon, Rio Tinto Kennecott is aiming to achieve net zero by 2050.