Using renewable energy rather than fossil fuel electricity in the smelting process to produce green aluminium is an easy technology requiring no changes in the aluminium production process. Aluminium, a very large industry, is known for its high demand of electricity to smelter the aluminium bauxite. Existing technology could immediately save over 50% without any technology changes. The change needs to be taken in various stages. Emissions could be reduced in very simple steps. Additional reductions may require some changes in production methods. Some smelters globally use hydro power, but most rely on fossil fuel energy sources. With the reduction in CO2 emissions and the move to renewable energy as fast as possible, owners of aluminium smelters have changed their messaging. The aluminium owners not only resisted any change, they lobbied Governments hard against accepting any changes. (E.g. Comalco New Zealand Tiwai Smelter). With a change in a political perspective, aluminium smelter owners are now seeking to reduce emissions using renewable energy as the first step.
Rio Tinto said in June its Boyne aluminium smelter, Yarwun alumina refinery and Queensland Alumina refinery need a combined 1,140 megawatts (MW) of reliable renewable power, and was seeking offers to build at least 4,000 MW, or 4 GW, of wind and solar power backed up by energy storage which would be required to supply steady power so they could manufacture green aluminium.
Industry Has Resisted Green Aluminium
As far back as the late 1990s, it was known the aluminium smelting industry accounted for 16% of Australia’s carbon emissions from the electricity sector and 6.5% of Australia’s total emissions (excluding land-use change). (Australian Institute). Furthermore, they had large subsidies in electricity, estimated at $0.8 billion in 1999, despite 59% of the output of the aluminium smelting industry in Australia foreign owned, with Japan (17%), British (14%) and US (12%) interests dominant. Nothing much has changed in the past 2 decades.
Aluminum Manufacturing Processes
In “Impacts of aluminum production: A cradle to gate investigation using life-cycle assessment” (Science Direct), Farjana describes 4 steps:
- Mining of bauxite.
- Alumina production – using the Bayer process of refining the bauxite ore to obtain aluminium oxide
- Smelting – the Hall-Heroult process of smelting the aluminium oxide to release pure aluminium
- Ingot casting of the aluminium.
Green Aluminium Already Cost Competitive
In Australia, about 16% of the electricity used is for aluminium smelters. Life Cycle Analysis demonstrates replacing fossil fuel energy at both the mining stage and at smelting process will make the biggest and simplest changes.
A Renew Economy article in mid 2021 reports on BloombergNEF that the current average cost of producing aluminium using fossil fuels currently sits at US$1,680 per ton (A$2,156), while the combination of renewable energy sources and new “inert anode” technologies can already see production costs cut to just US$1,590 per ton (A$2,040), and avoiding virtually all emissions from the aluminium smelting process.
Two Simple Steps to Green Aluminium
- Use Renewable Energy in the Mining process. There are multiple existing technologies
- Change to renewable Energy in the refining, smelting and casting processes
More Difficult – Inert Anode in Aluminum Process
A more difficult process step is to replace the active anode with an inert anode. (See process from UN Climate Center) but Rio Tinto is already working on that as well in a pilot plant in Canada. (Press release Rio Tinto). The inert anode prototype cells will operate on a commercial scale typical for large modern aluminium smelters, using an electrical current of 450 kiloamperes (kA).
Aluminium Process Diagram