Mining heavyweights to build pilot plant

Rio Tinto and Sumitomo Corp. have teamed up to build a demonstration plant aimed at reducing greenhouse gas emissions from the production of aluminum.

The A$111.1 million (US$73.9 million) pilot project, the first of its kind deployment of hydrogen calcination in the world, will be built in Australia at the Yarwun Alumina Refinery in Gladstone, Queensland.

The project, co-sponsored by the Australian Renewable Energy Agency (ARENA), which contributed A$32.1 million (US$21.3 million) to the venture, is designed to reduce pollution from alumina refining, which accounts for roughly 3% of Australia's greenhouse gas emissions.

Australia is the world's largest exporter of alumina, the mineral feedstock for aluminum production, with the industry contributing about A$7.5 billion (US$5 billion) to the nation's annual gross domestic product.

The demonstration project follows a successful feasibility study conducted by Rio Tinto, which ARENA supported with an A$580,000 (US$386,000) grant in 2021.

ARENA CEO Darren Miller says the pilot is an important step in the development of hydrogen calcination and the decarbonization of the alumina production process.

"This world-first pilot looks to prove a promising technology for decarbonizing one of our most emissions intensive industries," he said.

ARENA's Alumina Decarbonisation Roadmap, or Alumina Roadmap, published in 2022, identified hydrogen calcination as one of four technologies that could reduce emissions from Australia's alumina refineries by up to 98%.

The renewable energy agency has been investing in projects to reduce emissions from the aluminum value chain since 2021. This includes providing funding to Alcoa to investigate electric calcination and trial mechanical vapor recompression, two further technologies identified in the Alumina Roadmap.

Potential game changer

At the Yarwun demo plant, Sumitomo will own and operate the electrolyzer at Rio Tinto's site and supply the hydrogen to Rio Tinto directly. The electrolyzer will have a production capacity of more than 250 metric tons of hydrogen annually.

Rio Tinto will conduct a series of tests of the hydrogen calciner under different operating conditions to validate suitability and performance.

Calciners, which use high temperatures to extract chemically bound water from alumina crystals, traditionally use fossil fuels for heat and contribute roughly 30% of the emissions from alumina refining.

Hydrogen calcination also produces high-purity steam, which, unlike contaminated steam from fossil fuel calcination, can be recycled for use in other stages of the refining process.

If successful, the project will demonstrate the viability of hydrogen calcination and pave the way for adoption at scale across other alumina refineries, according to ARENA.

"Having already backed an encouraging feasibility study, we're excited to be working with Rio Tinto and Sumitomo Corporation to build on that success and trial hydrogen calcination in the field," said Miller. "If this pilot project is successful, it could be a game changer for Australian alumina production, paving the way for deployment across the industry, and underscoring the importance of low-cost green hydrogen to decarbonize our largest industrial emitters. ARENA will continue to support projects at this scale as we develop other larger programs, such as Hydrogen Headstart."

Potential global impact

Because aluminum is a critical building block for everything from electric vehicles and energy-efficient buildings to a modernized electrical grid, the element has a significant role to play in global efforts to reduce greenhouse-gas emissions.

And unlike other basic materials such as steel and plastic, aluminum can be infinitely recycled with no loss of quality. About 75% of all the aluminum ever produced is still in use today, according to a report published in April by the Mission Possible Partnership with support from McKinsey & Co.

While the metal itself is sustainable, its production, however, usually is not. Although abundant in the Earth's soil and rocks, aluminum does not occur in its pure form and (must) be extracted from compounds, a complicated process of refining and smelting that requires a large and constant load of electricity.

This electricity has traditionally leaned heavily on coal-fired generation. Globally, about 55% of the electricity needed for aluminum smelters comes from coal-fired power plants, with 10% from natural gas and 30% from hydropower. As a result, the aluminum industry is among the highest-emitting sectors in the world, accounting for about 2% of global greenhouse gas (GHG) emissions.

According to the Mission Possible report, radical decarbonization is needed, an objective not easily accomplished.

"To achieve an emissions pathway consistent with 1.5°C of global warming (as envisioned by the Paris Agreement on climate change), the aluminum industry will need to slash emissions dramatically - from around 15.9 metric tons of carbon dioxide equivalent (CO2e) per metric ton of primary aluminum (non-recycled) today to lower than 0.5 tCO2e/t by 2050," according to the International Aluminum Institute.

Progress is already underway. In China, which produces nearly 60% of the world's primary aluminum, the nation's largest aluminum producer has shifted much of its capacity to the hydropower-rich Yunnan province. Many companies are also exploring green technologies, including carbon capture and storage; inert-anode technology, which avoids the formation of carbon dioxide; and mechanical vapor recompression (MVR), which recycles waste heat to improve efficiency. The industry's current pipeline of green projects, however, is likely not enough to achieve the ambitious 95% reduction target, according to the industry consultant.

Varied actions needed

To accelerate the pace of decarbonization, bold action is required on multiple fronts, as explored in the Mission Possible report. No easy answer exists.

"Producing greener aluminum isn't a simple matter of swapping out coal generation with renewable energy. Throughout each stage of aluminum production, large amounts of constant-load energy are required. Although the end goal is to make clean or renewable energy central to the production process, the most cost-efficient and effective way to get there is likely to involve a range of technologies and solutions," the report said.