steel furnace

Rio Tinto investigating low-carbon sustainable steel production

Metals producer Rio Tinto has said it is developing a new way to deliver low-carbon steel by using sustainable biomass in place of coking coal in the steelmaking process.

The production of steel is typically very energy and carbon intensive; in 2019 it was responsible for 2.7 per cent of all UK emissions.

Rio Tinto has developed a new process that combines sustainable biomass with microwave technology to convert iron ore to metallic iron during the steelmaking process.

The process is currently undergoing further testing in a small-scale pilot plant, with the potential to be scaled up commercially to process Rio Tinto’s iron ore fines if successful.

“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,” Rio Tinto’s iron ore chief executive Simon Trott said.

“More than 70 per cent 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.”

The new process uses plant matter known as lignocellulosic biomass, instead of coal, primarily as a chemical reductant. The biomass is blended with iron ore and heated by a combination of gas released by the biomass and high efficiency microwaves that can be powered by renewable energy.

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

The University’s Professor Chris Dodds said: “It is really exciting to have the opportunity to be part of a great team working on a technology that, if developed to commercial scale, has the potential to have a global impact through decarbonising key parts of the steel production process.”

The use of raw biomass in Rio Tinto’s process could also avoid the inefficiencies and associated costs of other biomass-based technologies that first convert the biomass into charcoal or biogas.

Lignocellulosic biomass includes agriculture by-products such as wheat straw, corn stover, barley straw and sugar cane bagasse, alongside purpose-grown crops. The process cannot use foods such as sugar or corn and Rio Tinto has said it will not use biomass sources that support logging of old-growth forests.

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

The UK government was recently urged to accelerate investment in lowering the carbon impact of the steel industry through the development of new processes.

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