Rio Tinto said the decision follows 18 months of testing in Germany, where a project team that includes representatives from Metso Outotec and the University of Nottingham’s microwave process engineering group, have been developing the BioIron process in a small-scale pilot plant. 

The BioIron process uses raw biomass instead of metallurgical coal as a reductant and microwave energy to convert Pilbara iron ore to metallic iron. The biomass is from agricultural byproducts such as wheat straw or canola stalks, or purpose-grown crops.  

“The biomass is blended with iron ore and heated by a combination of combusting gases released by the biomass and high-efficiency microwaves that can be powered by renewable energy,” the company said. 

Rio Tinto chief commercial officer Alf Barrios said the results from the initial testing phase are promising and demonstrate that the process can work well with Pilbara iron ore fines.

“Finding low-carbon solutions for iron-making and steelmaking is critical for the world as we tackle the challenges of climate change. Proving BioIron works at this scale is an exciting development given the implications it could have for global decarbonization,” he said. 

“BioIron is just one of the pathways we are developing in our decarbonization work with our customers, universities and industry to reduce carbon emissions right across the steel value chain,” he added.

Tests at the small-scale plant have been conducted using batches of 1,000 golf ball-sized iron ore and biomass briquettes. But now the team intends to step up the scale, testing the process in a specially designed continuous pilot plant with a capacity of one metric ton per hour. 

The design of the pilot plant is underway, and Rio Tinto is evaluating locations, it said.