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Rio Tinto targets low-carbon steel production with new technology; biomass and microwaves

Rio Tinto is progressing new technology to deliver low-carbon steel, using sustainable biomass in place of coking coal in the steelmaking process, in a potentially cost-effective option to cut industry carbon emissions.

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 patent-pending process, one of a number of avenues the company is pursuing to try to lower emissions in the steel value chain, is now being further tested in a small-scale pilot plant.

If this and larger-scale tests are successful, there is the 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.

More than 70% of Rio Tinto’s Scope 3 emissions are generated as customers process our iron ore into steel, which is critical for urbanization and infrastructure development as the world’s economies decarbonize. 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 Iron Ore Chief Executive Simon Trott

Rio Tinto’s process uses 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 the multi-disciplinary team in the University of Nottingham’s Microwave Process Engineering Group to further develop the process.

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 decarbonizing key parts of the steel production process.

—University of Nottingham’s Head of Department, Chemical and Environmental Engineering, Professor Chris Dodds

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 (i.e. wheat straw, corn stover, barley straw, sugar cane bagasse) and purpose-grown crops, which would be sustainable sources for the process.

Importantly, the process cannot use foods such as sugar or corn, and Rio Tinto would 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. We will continue working with others to understand more about these concerns and the availability of sustainable biomass.

—Simon Trott

If developed further, the technology would be accompanied by a robust and independently accredited certification process for sustainable sources of biomass.



It is not really low-carbon. It is fossil-fuel and especially coal free. They are making coke from bio-mass instead of coal. You actually need a small amount of carbon in steel for strengthening and hardening.

I think that Boston Metals has a better idea for energy efficient production of clean iron from iron ore. They use electricity for direct electrolysis of molten iron ore. The only outputs are high-purity molten iron and oxygen. I suppose that Rio Tinto could claim that they use less electric power although they probably need to convert the molten iron to steel in an electric arc furnace while I believe that the Boston Metals process only needs to have the alloying agents added before being rolled into the desired products. We will have to see if the Boston Metals process scales up as well as they expect.

Anyway see:


Ironically, biomass used to power the production of pig iron in Michigan's upper peninsula.  The ghost town of Fayette was a major center of iron reduction, turning trees into charcoal and reducing iron ore with the charcoal; the pig iron was moved out on sailing ships.  When the process for turning metallurgical coal into coke was perfected, the need for wood was eliminated and Fayette was abandoned.

Going back to biomass for the carbon source almost brings us full circle.  It's not a repeat of history, but it rhymes.


In the late 19th century, enough trees were cut down to make charcoal for the production of iron that it lead to deforestation of vast areas of England and some of the eastern US. I know that it was a problem in Brazil as late as 20 or 30 years ago with small scale artisan iron production. Anyway, Rio Tinto is supposedly only using waste biomass.

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