The Copper, Bronze and Iron Ages have each allowed humanity to develop and achieve new technological advancements and innovations like never before. The Iron Age developed into the Steel Age that continues today. With the growth in renewables demanding a lighter construction with recycling credentials, it may soon become the Age of Aluminium.

While alumina has seen a four per cent year-on-year growth, the last 12 years have been testing, with the industry largely in oversupply post-global financial crisis. Most recently, industry has had to contend with the aftermath of COVID-19.

Beyond the effects of COVID-19, another issue looms: the response to climate change. “Despite the current lower cost of hydrocarbons, we are amid the energy transition tipping point and investment dollars are accelerating towards low-carbon solutions,” says Jock Armstrong, Principal Consultant at Worley’s Bauxite and Alumina Centre of Excellence in Brisbane, Australia.

Energy transformation is an opportunity for the industry to show the way forward.

Aluminium’s light weight, corrosion resistance, and recyclability are its major assets in becoming a metal of choice in the energy transition.

“To meet emissions targets, the world is going to need a lot more aluminium,” says Armstrong. “As a recyclable metal, it’s a perfect foundation for electric vehicles, aeroplanes and electronics, paving the way towards a circular economy. This creates a compelling case to produce more. But to produce aluminium you need a lot of energy. Despite it being a metal of choice, as we transition to new energy systems, aluminium’s current carbon footprint is becoming incompatible with our climate change targets,” explains Armstrong.

The parameters are being set for the future of aluminium and megatrends are reshaping the aluminium industry. “The first megatrend to consider is geo-political influence on markets,” says Armstrong. “Government subsidies underpin energy projects, which help to support local production. However, the extent to which subsidies are applied varies from country to country.

“It’s a competitive industry, and extensive government subsidisation is distorting production geographies. Suddenly, there is an excess of alumina and smelting capacity where there wasn’t in the past. However, regulations and policies vary from one region to another, and some countries still produce most of their energy from coal. And where there’s cheap energy, there’s cheap aluminium.”

Aluminium operators can’t stick with coal to compete in a decarbonised future. And nor will they want to as new energy alternatives and technologies change the way alumina and aluminium is manufactured.

“Renewables will dominate the energy supply of the future,” says Armstrong. “The levelised cost of energy from photovoltaic and onshore wind already match coal and are on steep technology cost learning curves.  

“As prices drop, there are compelling economic and carbon footprint drivers to change energy sources. It’s just a matter of understanding how to store big amounts of energy.”

Finding solutions for storing energy

Armstrong comments that energy storage technology has already proven successful in other industries. It offers a more immediate solution because it takes technology that is ready now, supported by renewables, which can then be applied to the alumina industry.

For the alumina industry a steady supply of energy, day and night, is essential. One technology with the potential to supply this is molten salt. Molten salt can act as a large-scale thermal storage, allowing for the integration of renewables by smoothing out fluctuations in supply. Heat is initially generated by low-cost transient renewable power. Raising the molten salt temperature to 500-600°C provides the energy to raise steam for the refinery. Molten salt storage is something Worley is already successfully delivering in Concentrated Solar Power facilities.

“Costs can be minimised by reconfiguring a plant’s energy and steam supply,” explains Armstrong. “There are potential retrofitting opportunities for existing facilities to use molten salt to raise steam rather than having to build new assets. When we use molten salts, we can reduce the cost of the conversion by tapping into wind and solar technology.”

Molten salts are only one piece of a puzzle. Grid-based electrification paths exist, and technology-driven refining efficiencies always need to be progressed in a competitive market. Beyond COVID-19, the pressure to address climate change will remain. Energy transformation pathways need to be mapped and the journey will continue.

Green aluminium

While relatively new, green aluminium is already a differentiated product in the market. The London Metal Exchange, the world’s largest market for industrial metals, recently joined the green revolution by launching a platform to trade low-carbon aluminium. For the first time in its 140+ year history, a metal can now be traded based on its environmental footprint.

“Green aluminium is currently produced by hydro-powered smelters,” says Armstrong. “While there’s only a handful of partnerships between aluminium providers and consumer-goods companies, having this ‘green stamp’ is becoming a strong differentiator because there is a growing demand for ethical, low-carbon products.”

However, coming up with the best approach to produce green aluminium is keeping engineers on their toes. “There’s no bolt-on solution,” says Armstrong. “The right solution depends on local regulations and access to energy forms. Hydropower may work for some. But solar, wind, salt storage or hydrogen may work better for others.”

This means aluminium smelters will likely exist in more complex power networks. “There is potential to integrate electricity demand into stabilisation mechanisms, such as shell heat exchange for smelter power modulation. Pumped hydro storage is also a compelling option for large scale storage to facilitate high renewables uptake.

For alumina refineries, on-site thermal energy storage can enable the use of renewables during oversupply and reduce demand during peak loads. But this is only one option,” explains Armstrong.

“Imagine a refinery electrified through mechanical vapour recompression with a  solar powered calciner,” proposes Armstrong. “Imagine CO2 capture in residue being the new normal. Or perhaps as the cost of green hydrogen production falls, we will see it take its place as the link between transient renewables and base load refinery demand.” 

As demand increases, so will society’s expectations for ethical and sustainable practices. “Unless aluminium can truly become a green metal, operators will struggle with their social licence to operate,” says Armstrong. “Operators need to start paving their path to decarbonisation. And like any journey, timing is critical. The time is now to step up and take the lead. It’s the boldest, not the biggest, that will transform the aluminium industry of tomorrow.”