Rio Tinto’s BioIron success in low carbon ironmaking

Rio Tinto has proven the effectiveness of its low-carbon iron-making process using ores from its mines in Australia in a small-scale pilot plant, and is now planning a larger-scale pilot plant to further assess its potential to help decarbonise the steel value chain.

The company’s BioIron process uses raw biomass – wheat straw, canola stalks, barley straw, sugar cane bagasse or purpose-grown crops – instead of metallurgical coal as a reductant and microwave energy to convert Pilbara iron ore to metallic iron.

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.

Over the past 18 months, the process has been tested in Germany by a project team from Rio Tinto, sustainable technology company Metso Outotec, and the University of Nottingham’s Microwave Process Engineering Group.

Work was conducted in a small-scale pilot plant using batches of 1,000 golf ball-sized iron ore and biomass briquettes (pictured), with the results suggesting the process had the potential to support near-zero CO2 steel-making, and could result in net negative emissions if linked with carbon capture and storage.

Rio Tinto Chief Commercial Officer Alf Barrios said: “Finding low-carbon solutions for iron 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 decarbonisation.

“The results from this initial testing phase show great promise and demonstrate that the BioIron process is well suited to Pilbara iron ore fines.”

BioIron’s potential was confirmed in an independent technical review by engineering firm Hatch.

The BioIron process will now be tested in a continuous pilot plant with a capacity of one tonne per hour – design of the pilot plant is underway and Rio Tinto is considering suitable locations for its construction.

Rio Tinto said in a statement it was aware of the complexities around the use of biomass supply and was working to ensure only sustainable sources of biomass are used.

Initially, the company has ruled out sources that support the logging of old growth and High Conservation Value forests.

Picture: Rio Tinto