South32 deal will redraw Alcoa’s – and Australia’s – energy map

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Alcoa’s acquisition of South32’s Western Australia (WA) assets will move it closer to the heart of Australia’s industrial transformation. 

The deal, announced as part of a buyout of South32’s global aluminium portfolio, enhances both the corporate and regulatory imperatives to transform one of Australia’s most energy- and emissions-intensive sectors.

Industry consolidation concentrates vast energy use and emissions

Alcoa announced last month it would acquire South32’s controlling interest in WA’s Worsley alumina refinery and integrated Boddington bauxite mine as part of a global deal worth up to US$5.6 billion (AU$8.1b).

Shareholder and regulator approval would raise Alcoa’s approximate production shares of Australian bauxite from 30% to 50% and alumina from 40% to 60%, respectively, along with control of all related interests in WA, according to Australian Aluminium Council (AAC) and company figures.

Alcoa will also assume a much larger share of Australia’s energy and climate task. Alumina refining consumes about 3% of national energy, and generates a similar share of greenhouse gases, according to AAC, Australian Energy Statistics and National Greenhouse Gas Accounts figures.

While electricity provides 80% of aluminium smelting’s energy and emissions, fossil-derived thermal energy provides 90% of these figures for alumina refining. This has implications for corporate responsibility – where electricity falls under Scope 2 emissions if externally purchased, thermal energy is a direct Scope 1 concern.

Worsley brings unique challenges

Industry analyst Wood Mackenzie noted the Alcoa deal “removes a significant decarbonisation burden”  for South32. As a corollary, Alcoa will assume this burden.

Where Alcoa’s existing Pinjarra and Wagerup refineries use gas for co-generated thermal energy and electricity, coal contributes 40% of the energy mix at Worsley, which also sources minimal grid electricity (see figure below).

^{Source: South32 Sustainability Databook 2025.}

This profile helps to give Worsley the seventh-highest emissions under Australia’s (solely Scope 1-focused) Safeguard Mechanism, at 3.2 million tonnes of CO2 equivalent (MTCO2 e) a year, while Wagerup and Pinjarra rank 22nd and 24th,respectively.

Integrating Worsley into Alcoa’s portfolio could invite energy use-impacting operational changes. But continuing to run the facility anywhere near business-as-usual (BAU) would dramatically alter Alcoa’s – and Australia’s – energy and emissions landscape.

Adding a BAU Worsley could almost double Alcoa’sannual Safeguard emissions of 3.3MTCO2e, with greater impact if its now shuttered Kwinana refinery is excluded. (Note: These figures attribute all the Safeguard-covered emissions from the Portland Aluminium Smelter to Alcoa, although the company owns only 55% of the facility.)

Further, a BAU Worsley would put Alcoa firmly in the top 10 corporate emitters in Australia’s National Greenhouse and Energy Reporting (NGER) Scheme. It would climb from 15th to 8th for Scope 1 –  just above leading fossil fuel producer Woodside – and from 9th to 7th  for combined Scope 1 and 2 emissions. 

^{Source: Calculated from NGER Corporate emissions and energy data 2024-25, with Worsley emissions and energy contributions taken from South32 Sustainability Databook 2025.} 

Alcoa would also have the second-highest NGER net energy consumption, trailing only electricity generating giant AGL.

Future energy choices will be fateful

In announcing the South32 deal, Alcoa CEO William Oplinger noted Worsley’s lower cost, more profitable production base. But the facility’s energy and emissions implications bring significant complications.

Firstly, with energy accounting for 25–30% of alumina refining costs, margins are highly sensitive to shifting consumption trends.

And Worsley must change tack here. It has already reduced its heavy coal use, partly in response to the sunsetting of WA coalmining, which forced it to temporarily import coal. But the job must be completed by 2031, in line with WA’s revised coal exit date.

Worsley’s near- to mid-term climate plans largely depend on substituting gas for coal, alongside energy efficiency and, if needed, carbon offsets.

However, gas is no guarantee of cost competitiveness. Major producers have as much as doubled prices for domestic users since 2020. Domestic shortfalls are forecast from 2029, and improved reservation will likely be required to guarantee sufficient affordable supply stays in WA.

Growing government and/or consumer demand for legitimately clean alumina is also a threat to competitiveness.

Australian alumina refineries have faced relatively minor emissions constraints thus far. In lieu of demonstrating clear progress towards fossil-free production, South32 surrendered more than 130,000 combined offsets and credits to meet Worsley’s FY2024-25 Safeguard baseline.

Nonetheless, the federal government’s Net Zero Plan for the sector anticipates the Safeguard – backed by incentives such as A Future Made in Australia subsidies – will begin inviting investment to clean up alumina’s emissions-intensive digestion and calcination processes. This suggests policy will tighten in future.

Corporate mandates and global policy developments, such as carbon border adjustments, are also making emissions-intensive production a competitive liability.

Alcoa regularly celebrates its alternative advantage as “the world’s lowest carbon intensity alumina producer”, with a global average below 0.6 tonnes of CO₂e(Scope 1+2) per tonne of product. Acquiring Worsley threatens this claim – its current intensity is 0.8t CO2e/t.

Keeping pace with consumer preferences can, moreover, only be assured if gas entrenchment is also avoided, both at Worsley and the remaining Alcoa facilities.

Alcoa should future-proof its expanded portfolio

Transitioning alumina refining to cleaner, and potentially more secure, energy requires greater industry and policymaker ambition.

Alcoa, South32 and remaining Australian alumina refiner Rio Tinto have committed to tackle the sector’s emissions challenges, in concert with government.

Alcoa tested mechanical vapour recompression (MVR) at Wagerup with Australian Renewable Energy Agency (ARENA) support, but determined it unviable in 2023. Taxpayers have also subsidised trials of electric calcination at Pinjarra, and steam electrification at Worsley.

The path to commercialising breakthrough technologies remains uncertain. So far, WA’s refineries have been unable to even meet their existing electricity needs through onsite renewables or the South-West Interconnected System’s growing share of firmed wind and solar. Energy efficiency is also an underutilised option.

The enabling environment for alumina decarbonisation, including continued growth in grid capacity and access, certainly needs improvement.

Alcoa could contribute directly to the task.

Rio Tinto has taken the lead at its Queensland alumina and aluminium operations, by signing landmark renewable power purchase agreements, including Australia’s largest-ever such deal, helping to make massive new generating projects commercially viable.

Taking on South32’s considerable energy and emissions obligations should accelerate Alcoa’s appetite for transformation.

Worsley could turn from laggard to lighthouse project by successfully leapfrogging from coal to fossil-free energy, ideally renewables-powered electrification. This, in turn, could inform the elimination of gas elsewhere.

The South32 deal could also enhance Alcoa’s ability to achieve grander decarbonisation ambitions. An expanded industry presence would increase its ability to direct sector-wide investment, access energy and technology, and develop consumer markets.

Consolidation would also increase policymakers’ ability to tailor both carrots and sticks towards more ambitious decarbonisation.