ARENA maps out pathways towards zero emissions alumina

The Australian Renewable Energy Agency has released a roadmap to decarbonise Australia’s alumina sector – crucial for net zero goals as the country is the world’s largest alumina exporter.

Worth $7.5 billion to the national economy every year, the Roadmap for Decarbonising Australian Alumina Refining, outlines technologies that could reduce emissions from Australia’s six alumina refineries by up to 98 percent.

Alumina refining is energy and emissions intensive, and is responsible for up to three per cent of Australia’s annual emissions.

Commissioned by ARENA with input from Australia’s three alumina producers, Alcoa, Rio Tinto and South32, and prepared by Deloitte, the roadmap said: “Four Key Decarbonisation Technologies have the potential to almost entirely eliminate alumina refining emissions in Australia.”

ARENA CEO Darren Miller described the roadmap as ‘an important call to action’.

Miller said: “Decarbonising the alumina refining sector can further improve Australia’s international competitiveness, strengthen its position as a leading producer of low emissions alumina and aluminium and secure the jobs and economic benefits from the sector.”

Of the three stages of the alumina value chain, bauxite mining is by far the least energy intensive while aluminium smelting is the most, relying heavily on electricity.

Emissions from aluminium smelting are expected to fall as Australia’s electricity grid transitions to renewable energy, but refining itself still relies on fossil fuels to provide both heat and electricity.

The roadmap identifies four key technologies to reduce emissions.

Mechanical vapour recompression (MVR) can replace natural gas boilers for steam production in alumina refineries.

This process captures, recompresses and recycles waste steam that would otherwise vent to the atmosphere.

Renewable electricity powered MVR could reduce emissions in alumina refining by up to 70 per cent.

In May 2021, ARENA announced $11.3 million in funding to Alcoa to demonstrate the MVR technology at its Wagerup alumina refinery.

This $28.2 million project is a first-of-its-kind demonstration of MVR technology in Australia. If proven feasible, Alcoa will deliver a 3 MW MVR module, powered using renewable energy.

Powered by renewable energy, electric boilers can also replace coal or gas fired boilers for steam production.

Low temperature electric boilers are a mature technology that could be deployed at some refineries before 2030.

However, there is a caveat. According to the roadmap: “Electric boilers have higher operating costs than current fossil fuel fired boilers.

“Access to low-cost renewable electricity or other financial support mechanisms are required to make this technology economically viable.”

The third technology path, hydrogen calcination replaces the combustion of natural gas in the calcination process with the combustion of hydrogen.

Combusting hydrogen with a stream of oxygen produces a pure steam exhaust. The Bayer process can capture and reuse that steam when combined with MVR.

ARENA is providing $580,000 funding towards a feasibility study at Rio Tinto’s Yarwun alumina refinery in Gladstone. Launched in 2021, the study is examining the case for constructing a hydrogen pilot plant and the potential use of hydrogen at the refinery.

Rio Tinto is investigating replacing natural gas with hydrogen in the calcination process, and retrofitting hydrogen burners in its existing calciners.

Finally electric calcination can replace coal or gas powered calciners with electric calciners powered by renewable electricity.

Removing chemically bound water from the alumina crystals also produces pure steam. In combination with MVR, a refinery can capture and reuse that steam.

However, electric calcination is at a low level of technical maturity and will require significant support to commercialise with potential deployment from 2035 onwards.

In April 2022, Alcoa announced it will demonstrate electric calcination technology at its Pinjarra Alumina Refinery. ARENA is providing $8.6 million funding support to the $19.7 million project. The Western Australian Government is also contributing $1.7 million through its Clean Energy Future Fund.

This project is a world-first demonstration of electric calcination.

Alcoa’s main objective for the project is to demonstrate the technical and commercial feasibility of using electric calcination technology powered by renewable energy.

Miller said the roadmap provides a clear vision for decarbonising one of Australia’s most emissions intensive industries.

“Alumina refining has always been considered a hard-to-abate sector with significant barriers to reducing emissions.

“Now, we have Australia’s biggest alumina producers coming together with ARENA to develop a clear and credible pathway to reducing emissions in the industry.

“With just four key decarbonisation technologies currently in development to reduce nearly all emissions from Australian alumina refineries, what we need now is coordinated investment to accelerate the commercialisation of these technologies.”

Picture: ARENA/alumina