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Rio Tinto develops unique biomass technology for steelmaking

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Rio Tinto, a multinational metals and mining corporation, is developing innovative new technology to deliver low-carbon steel using sustainable biomass in place of coal.

Over the past decade, Rio Tinto has developed a laboratory-proven process that combines the use of raw, sustainable biomass with microwave technology to convert iron ore to metallic iron during the steelmaking process.

The use of raw biomass in the firm’s process - which includes agriculture by-products such as wheat straw, corn stover, barley straw, sugar cane and bagasse – could also avoid the inefficiencies and associated costs of other biomass-based technologies that first convert the biomass into charcoal or biogas.

The patent-pending process, one of several avenues the company is exploring to lower emissions in the steel value chain, is now being further tested in a small-scale pilot plant. If successful, there is potential over time for this technology to be scaled commercially to process Rio Tinto’s iron ore fines.

“We are encouraged by early testing results of this new process, which could provide a cost-efficient way to produce low-carbon steel from our Pilbara iron ore,” said Rio Tinto Iron Ore chief executive, Simon Trott.

“More than 70% of Rio Tinto’s Scope 3 emissions are generated as customers process our iron ore into steel, which is critical for urbanisation and infrastructure development as the world’s economies decarbonise. So, while it’s still early days and there is a lot more research and other work to do, we are keen to explore further development of this technology.”

Rio Tinto’s process uses lignocellulosic biomass, instead of coal, primarily as a chemical reactant. The biomass is blended with iron ore by a combination of gas released by the biomass and high-efficiency microwaves that can be powered by renewable energy.

The firm is adamant that the process cannot use foods such as sugar or corn and that it would not use biomass sources that support the logging of old-growth forests.

Trott added: “We know there are complex issues related to biomass sourcing and use and there is a lot more work to do for this to be a genuinely sustainable solution for steelmaking.

“We will continue working with others to understand more about these concerns and the availability of sustainable biomass.”

Rio Tinto’s researchers are working with the University of Nottingham’s Microwave Process Engineering Group to further develop the process.