PERTH (miningweekly.com) – Mining major Rio Tinto is pilot testing a 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, the miner 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, Rio said this week.

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,” said Rio Tinto iron-ore CEO 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’s 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.

The use of raw biomass in Rio’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, sugar cane bagasse, along with purpose-grown crops, which would be sustainable sources for the process. Rio noted that the process cannot use foods such as sugar or corn, and added that the company 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,” Trott said.

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