Diversified miner Rio Tinto has signed a joint development agreement (JDA) with Australian environmental technology firm Calix to support the proposed Zesty green iron demonstration plant in Kwinana, Western Australia, while placing further design work on its BioIron furnace on hold pending additional technical development.

If approved, the Zesty demonstration plant will be built at the site previously earmarked for Rio Tinto’s BioIron research and development (R&D) facility.

Rio Tinto said on Monday that its assessment of the current BioIron furnace design showed that more work was needed to minimise technical risks and improve performance, though it remained committed to the long-term potential of the technology.

BioIron, developed by Rio Tinto’s steel decarbonisation team over the past decade, uses raw biomass, such as wheat straw, bagasse and rice stalks, as the reducing agent, and consumes about one-third of the electricity required by hydrogen-based steelmaking routes.

Research continued with the University of Nottingham and Metso.

For the Zesty project, Rio Tinto will contribute about A$35-million in funding and in-kind support to advance the project, which is also backed by the Australian Renewable Energy Agency (ARENA).

Calix holds a separate ARENA grant of up to A$44.9-million, subject to matched funding.

Zesty uses electric heating and hydrogen reduction to produce lower-emissions iron and is compatible with Pilbara ores, including lower-grade material.

The demonstration plant is designed to produce up to 30 000 t/y of hydrogen direct-reduced iron or hot-briquetted iron.

Rio Tinto Iron Ore CE Matthew Holcz said the agreement would help progress a potential pathway for Pilbara ores in low-emissions steelmaking, adding that work on BioIron would continue in parallel.

Under the JDA, Rio Tinto will provide engineering and technical services to support the project to a final investment decision, expected in 2026.

Subject to approval and construction, the miner will supply up to 10 000 t of Pilbara ore for commissioning and initial testing and will introduce potential downstream customers.

The partnership gives Rio Tinto a non-exclusive global and perpetual licence for potential commercial use of the Zesty technology, with rights to sub-license to affiliates and customers and act as a nonexclusive global marketing agent.

The Kwinana site offers access to existing utilities and port infrastructure and is located near the NeoSmelt facility, where Rio Tinto and four other partners are developing downstream processing options with ARENA support.

Calix CEO Phil Hodgson said the JDA provided both funding and strategic backing from a major industry player as the Zesty project enters detailed engineering ahead of FID.