Deep beneath parts of Western Australia, a new study suggests that injecting CO₂-rich water into iron-rich rocks could potentially produce clean energy in the form of hydrogen while also storing carbon dioxide underground. This method, known as "orange hydrogen," relies on a natural geological process called serpentinization, where water reacts with iron-containing minerals in the rocks, producing hydrogen gas. The name "orange hydrogen" comes from the oxidized iron involved in the process. The research, published in the International Journal of Hydrogen Energy, was led by Dr. Lingping Zeng, an energy research scientist, and focused on the Yilgarn Craton, one of Earth’s oldest and most intact geological regions located in Western Australia. Australia is uniquely suited for this kind of research because large parts of the country contain the specific types of rocks needed for these reactions. The Yilgarn Craton, which spans much of south-central Western Australia, is rich in iron- and magnesium-bearing rocks that could support hydrogen generation. These rocks have remained largely undisturbed for billions of years, preserving some of the oldest parts of Earth’s crust, including zircon crystals over 4 billion years old. The study also explored the potential for these rocks to help store carbon dioxide, a critical challenge in reducing greenhouse gas emissions. When CO₂ dissolved in water flows through these rocks, it can react with minerals and become permanently trapped as solid carbonate minerals in a process called carbon mineralization. However, the conditions that maximize hydrogen production and carbon storage are not always the same. Researchers, including Dr. Regina Sander, an expert in reservoir engineering and economic modeling, stress the importance of understanding these trade-offs to develop practical energy solutions. Using advanced geochemical modeling, researchers from CSIRO simulated how underground fluids interact with mafic-ultramafic rocks in the Yilgarn Craton. Their findings showed that temperature significantly affects both hydrogen production and carbon storage. Higher temperatures increase hydrogen generation but may not always improve carbon storage. Carbon mineralization was most effective at moderate temperatures, around 150°C to 200°C. The chemistry of the underground fluids also played a role: lower salinity and alkaline (higher pH) conditions generally supported greater hydrogen production. These insights help identify the underground conditions most likely to support successful orange hydrogen systems. The Yilgarn Craton’s potential for orange hydrogen is particularly significant for Western Australia, which is planning several major renewable energy and hydrogen projects in the region. Although the area lacks large underground gas storage reservoirs, other parts of the state have sufficient depleted gas fields to store hydrogen produced in the Yilgarn. This could help balance supply and demand in a renewable energy system. While commercial orange hydrogen projects are not yet in place in Australia, the study marks an important first step. Future research will focus on laboratory experiments, field trials, and identifying the best geological settings for combining hydrogen generation with long-term carbon storage. Researchers believe that, given Australia’s vast resources of hydrogen-producing and carbon-storing rocks, this possibility is well worth pursuing.