CO2-free aluminum production

TRIMET is the largest German primary aluminium producer. In 3 smelter plants in Germany and 1 in France, TRIMET produces approx. 540,000 t of primary aluminium per year. Aluminium is produced by electrolysis using the so-called Hall-Héroult process, an energy-intensive electrochemical process.

Since the beginning, the process is based on carbon anodes and cathodes. CO₂ is emitted by consuming carbon anodes. The goal of this project is to develop a new process with new anode and cathode materials allowing the process to emit only O₂ instead of CO₂ and lowering the carbon footprint significantly thereby.

Political and industrial context

About 70 Mio. tons of aluminium are produced worldwide each year. The amount is steadily increasing as modern economies rely more on the lightweight metal. The carbon footprint of the aluminium sector is dominated by the energy-intensive electrolysis process. Because most aluminium is produced with electricity generated by coal power plants, energy generation is the biggest contributor to CO₂ emission. When supplied with renewable energy the footprint is much lower. Still the process emissions by burning the carbon anodes in the smelting process remain, which account for almost 100 Mio. tons of CO₂-equivalents worldwide per year. These direct process emissions can only be abated by implementing an inert anode technology. Here the carbon is replaced by an inert material, which can act as an anode but is not consumed and produces O₂ instead of CO₂. By this technology aluminium with a very low carbon footprint can be produced. The customer requires green aluminium and the industries goal is to achieve the complex inert anode technology in the future.

Project draft

TRIMET Aluminium SE, in collaboration with an international project consortium, is developing an innovative process for aluminum production using multiple vertical inert (non-consumable) anodes and cathodes in a low-temperature electrolyte (800°C) according to the formula:

2 Al2O3 + Energy = 4 Al + 3 O_v.

Since no carbon anodes are used, oxygen is released instead of CO2. The inert anode material is being developed in collaboration with the University of Saarland (USAAR). The project aims to scale up the round laboratory cells to 10,000 A for operation in a pilot plant at the TRIMET smelter in Essen, Germany. This project is funded by the state of North Rhine-Westphalia. Following the successful operation of the pilot plant in Essen, the project is expected to be expanded.

Following the successful operation of the pilot plant, the project will be expanded from January 2025. In the following years, TRIMET will set up a demonstration plant at its smelter in Essen, where the cells will be scaled up to the industrial level of up to 40,000 A of electricity. The project is being funded by the German Federal Ministry for Economic Affairs and Climate Protection as part of the "Decarbonization in Industry" funding programme. Funds from the European Union's "NextGenerationEU" fund are also being used.