Rio Tinto has turned a steady half-year profit, with copper and aluminium offsetting weaker iron ore production, but warns of challenges in decarbonising mines and refineries.

Chief executive Jakob Stausholm told investors on Wednesday he was finding ways to cut emissions including locking in competitively priced renewable energy but there was “a long way to go” to find better ways to provide the materials the world needed.

Shares in the mining giant rose $3.33 or 2.9 per cent to $117.99 in afternoon trade as earnings for the six months to June 30 met market expectations.

The company reported a flat net profit of $US5.8 billion ($A8.9 billion), while underlying EBITDA (earnings before interest, taxes, depreciation and amortisation) rose three per cent to $US12.1 billion ($A18.5 billion).

Rio Tinto also announced it would spend about $US1 billion ($A1.5 billion) annually on closure activities at the Argyle diamond mine in Western Australia, ERA’s Ranger mine, the Gove alumina refinery in the Northern Territory and legacy sites.

Mr Stausholm said technology and partnerships, such as renewable power for Australia’s largest aluminium smelter Boyne, in central Queensland, were solving complex problems.

Quizzed about replacing the power source for the Tomago aluminium smelter in NSW, he said that was much more difficult unless there was a hydro or nuclear plant next door.

But he dismissed efforts to resume uranium mining in the Northern Territory, saying it was “noise” from minority shareholders in subsidiary Energy Resources of Australia (ERA).

The recent rejection of a lease renewal for mining Jabiluka ended a bitter, decades-long campaign by traditional owners although nuclear proponents said the decision stopped the development of one of the world’s best undeveloped uranium reserves.

“Jabiluka will never be a mine,” he said, but insisted there was a future for uranium.

Mr Stausholm said Rio Tinto was “totally open” to more nuclear energy but greater consumption might be two or three decades away, while renewable energy was available now.

“We need to decarbonise – that means we use all sources … that can be solar, wind, hydro or it could be nuclear,” he said.

Unlike iron ore rival BHP, Rio Tinto has bought into lithium and might add more critical mineral assets to meet demand for batteries and electrification.

“If we might also add in a few other assets, then suddenly we have something of scale, something that is sizeable at the group level – maybe not as big as our iron ore business, but it’s difficult to match that one,” Mr Stausholm said.

Pilbara iron ore was on track for up to 360 million tonnes a year, with “comfortable” production growth of three per cent a year to 2028 and a focus on safety, he said.

An overnight autonomous train hit wagons and derailed near Karratha in May, with the mining and energy union saying the “catastrophic failure of safety systems” could have killed workers and put the region’s drinking water at risk.

Chief financial officer Peter Cunningham said the market had underestimated demand for iron ore, partly due to China’s steel production outperforming expectations.

But stockpiles have been built up, including about $US900 million in the Pilbara supply chain and $US400 million port-side in China.

Rio Tinto declared an interim dividend of $US1.77 per share, the same as a year earlier.