Rio Tinto has scrapped a $215 million research centre touted last year as a key staging ground for the world's net zero transition.

The site in Rockingham, south of Perth, will be handed instead to Australian technology company Calix for a green iron pilot plant, along with a $35 million investment in its zero-emission steelmaking technology.

The pivot sends plans for BioIron, a branded product the mining giant has spent more than a decade developing, back to the drawing board.

BioIron sought to harness biomass and microwave energy to convert Pilbara iron ore into raw iron, spruiked as reducing the carbon emissions of steelmaking by 95 per cent.

But Rio Tinto acknowledged on Monday its furnace designs needed "additional development" to minimise risks and optimise performance.

In a sta

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