Dhe fear of rust unites proud motorists, regardless of whether they are traveling by car, moped or bicycle. An idea from Dutch researchers is surprising: in the future, breweries should allow iron powder to rust in order to generate heat for beer production. Ultimately, it is about using solar and wind energy, albeit in a roundabout way.
Researchers from the Technical University of Eindhoven started a first attempt to brew beer using iron powder in 2020. They equipped the “Bavaria” brewery in Lieshout in the Netherlands with an iron burner. Iron reacts with the oxygen in the air and rusts. A spark accelerates this process, similar to lighting a sparkler. The metal releases heat during oxidation, which can be used directly in industrial processes or to generate electricity using a steam turbine.
According to the researchers’ vision, the resulting rust will be taken to a region where there is plenty of solar or wind energy. The green electricity generated in this way splits water using an electrolyser, and the resulting hydrogen in turn snatches the oxygen atoms from the grate, which is why engineers speak of a redox reaction. Apart from the water, all that remains is iron powder, which is transported in the holds of ordinary freighters to where it is supposed to generate electricity and heat – the cycle closes.
Between 60 and 100 degrees Celsius
In a project called “Clean Circles”, researchers from the Johannes Gutenberg University in Mainz, the Technical University of Darmstadt and three other scientific institutions are taking up the idea from Eindhoven. The aim is to convert coal-fired power plants to run on iron powder.
Aluminum powder might be even more attractive, at least for power generation. At temperatures between 60 and 100 degrees Celsius, it reacts with water to form aluminum hydroxide and hydrogen. The hydrogen is used in fuel cells to produce electricity and heat, for example for heating and for heating service water. This technology has already been developed to some extent at the Eastern Swiss University of Applied Sciences in Rapperswil. In a European research project, partners from seven countries want to perfect this process and the reconversion of the hydroxide into aluminum using electricity from renewable sources. If this works, an emission-free cycle will also be created in this way.
Researchers at the University of Reykjavik and the Technological Institute of Iceland have already realized zero-emission reverse conversion. They use an electrolysis process, which in itself is nothing new. Normally, however, the greenhouse gas carbon dioxide is produced because the graphite electrodes react with the oxygen in the hydroxide. The Icelanders have now developed electrodes that are inert, i.e. cannot react with the components of the aluminum hydroxide. Since Iceland’s electricity comes exclusively from renewable sources, mainly geothermal energy, aluminum production is completely climate-neutral.
The light metal is also attractive as an energy source. With an energy density of 15 megawatt hours per cubic meter, it contains at least 50 percent more energy by volume than heating oil. Like iron powder and rust, aluminum and its hydroxide can be stored for any length of time and transported over long distances without overly complex protective measures.