Despite first-half profits plunging 80 per cent, Rio Tinto's chief executive Sam Walsh says coal will be the backbone of energy production for many years to come.

Mr Walsh believes renewables will not fill the gap.

“Coal's going to be required as an energy source for a long, long time,” he said.

‘There are alternatives being developed but it's going to be a slow and gradual process as research and technology provides a gateway for them.

“I'm talking specifically about wind power, or solar power, wave power.

“These show promise but it's a long way down the track, and the same for there nuclear industry in Australia.

“Coal does provide the foundation for energy production and power and electricity and that's going to be the case for some time.”

Mr Walsh said global divestment campaigns and pressure from green groups and the gas industry would not be enough to topple coal.

“I think everybody's feeling the pressure of commodity prices being down and I suspect the oil and gas guys are feeling it just as much as the mining industry is and I think people are trying to position themselves,” he said.

Rio's latest six-month results showed an increase in coal production was up, but that gross revenue had dropped considerably.

The company said prices had fallen while cost cutting across the industry led to greater supply.

Mr Walsh said the company was doing something about greenhouse gas intensity.

“So we're not sitting on our hands, we are committed to continuing to further improve our greenhouse gas performance,” he said.

“And clearly the Australian coal product actually provides a cleaner alternative than many of the coals that are being used overseas.

“That's an important element in this equation as well.”