The European aluminium industry aims and needs to reach net zero by 2050. Manufacturers, fabricators and users of aluminium are united in support of this goal. How companies are directing their decarbonisation strategies is one of the focal points of the International Aluminium Exhibition in Düsseldorf, Germany.
Aluminium can be produced in two ways: In a primary process by smelting mined bauxite ore into raw aluminium or in a secondary process by recycling aluminium scrap. Recycling requires only 5% of the energy needed to produce primary aluminium. As a result, it finds itself on every aluminium company’s agenda.
Primary aluminium: Net-zero innovations approaching readiness for industrial application Norwegian company Norsk Hydro, the largest aluminium producer in Europe and one of the world’s technological leaders, plays a role throughout the aluminium supply chain – from ore to finished product. The aluminium production process begins with the mining of bauxite at the Paragominas mine in Brazil. From there, it is transported through a 244-kilometre-long bauxite ore pipeline to the Alunorte refinery in Barcarena. At this facility, using the Bayer process, it is processed into aluminium oxide, the raw material for producing primary aluminium via electrolysis in the company’s smelters.
Hydro has reduced CO₂ emissions at its Norwegian primary aluminium plants by 70% since 1990. Its climate strategy envisages a further 30% reduction in greenhouse gas emissions by 2030, with net zero to be reached by 2050. The decarbonisation roadmap includes increasing recycling, boosting use of renewable energy, converting natural gas to green hydrogen, reducing process emissions from primary aluminium production by utilising carbon capture and storage (CCS), and developing new production processes such as zero-emission smelting technology.
In this way, Hydro is developing CCS solutions that can be retrofitted to aluminium facilities that are already in operation. With its proprietary HalZero technology, Hydro is working on a development that promises to completely decarbonise aluminium smelting. Producing aluminium from aluminium oxide by electrolysis following the "Hall-Héroult process" is an energy-intensive electrochemical process involving anodes and cathodes made of carbon. Through the flow of electric current, aluminium oxide reacts with the carbon to form primary aluminium, which in turn releases CO₂. The company’s own HalZero technology is based on converting aluminium oxide to aluminium chloride before the electrolysis stage. Chlorine and carbon are kept in a closed loop, preventing CO₂ emissions and instead releasing oxygen. The company reports that this process has been successfully tested and modelled at Hydro’s research and development laboratory in Porsgrunn, Norway. Although there is still considerable research to be done, Hydro is confident that it will be able to produce the first zero-emission primary aluminium by 2025 and achieve industrial-scale pilot quantities by 2030.
Trimet Aluminium, the second-largest aluminium producer in Europe and the largest in Germany, is also pursuing ambitious decarbonisation goals. Trimet operates several production facilities spanning the entire aluminium supply chain, producing, recycling, casting and distributing lightweight metal products such as primary aluminium, wrought alloys for profiles, rolled bars for sheets and foils, and casting aluminium. The company is taking various measures to reduce CO₂ emissions. For example, at its Gelsenkirchen site, it is transitioning the process heat supply from natural gas to hydrogen-rich coke oven gas sourced from the nearby ArcelorMittal steelworks, with the long-term aim of using green hydrogen. It is also harnessing process heat for electricity generation and district heating as well as installing photovoltaic systems at its scrap storage facilities. Globally, the energy-intensive electrolysis process is a significant factor in the aluminium sector’s carbon footprint, as most aluminium production relies on electricity from coal-fired power plants. In contrast, sourcing renewable energy results in a substantially lower carbon footprint. Against this backdrop, Trimet has collaborated with Metrics to develop a process control system that can better respond to fluctuations in renewable energy sources on the grid. But even in an ideal scenario in which the power supply is fully sourced from wind and sunlight, there are still process-related emissions due to the combustion of carbon anodes during the smelting process, which Trimet estimates, contribute nearly 100 million metric tons of CO₂ equivalents annually within global aluminium production. These direct process emissions can only be reduced by adopting new technologies.
Trimet is engaged in research efforts on a form of inert anode technology. The carbon is replaced by an inert material that can act as an anode, although it is not consumed and produces oxygen instead of carbon dioxide. The company reports that aluminium can be produced with a very small carbon footprint using this technology. At its production plant in Essen, Germany, Trimet has commissioned a demo system to test out the technology for zero-carbon aluminium production on an industrial scale. Following the successful completion of the pilot phase, Trimet will now put the technology to the test in three electrolysis furnaces under production conditions.
Aluminium recycling: Both solution and problem
Aluminium recycling requires only 5% of the energy needed to produce primary aluminium. As a result, it plays a key role from the industry’s perspective. The European industry association, European Aluminium, has committed itself to the use of hydrogen to reduce CO₂ emissions via aluminium recycling.
For example, the EU-funded H2AL project includes testing the oxyfuel combustion of hydrogen as a combustion technology combined with low-NOx combustion techniques. This approach should make it possible to exploit the strengths of oxyfuel combustion while minimising emissions. The impacts of H₂ combustion on the refractory materials, the overall furnace structure and the aluminium product quality are also being investigated. However, the practical working of circular economy in aluminium still has its limits in terms of scrap quality. With the aim of extracting high-quality aluminium from scrap, pure and easily recyclable scrap has been and remains on the companies’ wish list. The heavily contaminated scrap constitutes a fraction that is difficult to recycle. Aluminium companies and thermal process technology specialists are working tirelessly to make it possible to recycle even the lesser grades and by-products.
Speira, with locations in Germany and Norway, recycles up to 650,000 metric tons of aluminium each year and produces around one million tonnes of rolled products. With the Alunorf joint venture in Neuss, Germany, the company owns the largest aluminium rolling mill in the world and the world’s largest advanced processing plant at its headquarters in Grevenbroich. At its Grevenbroich and Töging facilities, Speira is replacing the previous units with state-of-the-art systems. Installing four tiltable rotary kilns, the aluminium recycler is strengthening its capacity; especially for the recycling of “low grades”, i.e. heavily contaminated scrap, as well as residues that accrue during the melting process.
Novelis, the world’s largest aluminium recycler handling 2.2 million tons per year, aims to reduce its carbon footprint by 30% by 2026 and achieve net zero production by 2050. Over the past ten years, the company has invested more than $700 million in expanding its aluminium recycling facilities and reportedly increased the content of recycled material in its products to the highest level in the entire industry.
To further decarbonise, Novelis plans to replace a gas-fired batch furnace with an electric furnace, which is expected to save approximately 4,500 metric tons of CO₂ equivalent per year. The target at its R&D and production site in Sierre, Switzerland, is to achieve carbon neutrality for Scope 1 and Scope 2 emissions by 2030. Three decarbonisation projects are being funded by the Swiss government.
One project involves optimising furnace operations to reduce fuel consumption during heating, with the aim of determining ideal temperature profiles inside the furnaces. The second project includes efforts to investigate the availability of biomass and its optimum use as a renewable resource for decarbonising the aluminium melting process. The third project aims to forge ahead with the introduction of district heating in the local area. In establishing the Net Zero Lab Valais in Sierre, Novelis has initiated a systems study aimed at increasing energy efficiency in its process units, utilising waste heat from operations and improving the use of renewable energy sources available locally. Various key performance indicators, such as energy efficiency, CO₂ emissions, costs and technological availability, are being used to assess the suitability of different technologies. These metrics are being modelled in a software tool to simulate scenarios that take significant influential factors into account.
Source: Messe Düsseldorf, own research
