Ammonia is a colourless gas that is produced worldwide in such large quantities as hardly any other chemical. An international industrial consortium now wants to give it a color: Green it shall become.
The US gas producer Air Products and the power plant operator ACWA Power from Saudi Arabia as well as the royal family there plan to produce climate-neutral ammonia in the Saudi desert from 2025. Ammonia is often overlooked when it comes to climate protection – even though it contributes significantly to global warming. Its production is responsible for about three percent of global CO2 emissions. Today, ammonia is primarily produced on the basis of natural gas, but also with coal and oil,” says Florian Nigbur from the University of Duisburg-Essen. Manufacturers extract hydrogen (chemical symbol: H) from the fossil fuels. They then let the hydrogen react with nitrogen (N) from the air in the so-called Haber-Bosch process to form ammonia (NH3).
The Saudi-American consortium, on the other hand, wants to produce the necessary hydrogen climate-neutrally by electrolysis with wind and solar power. In the process, water is placed under electricity so that the acid and hydrogen molecules separate from each other.ammonia as fuel for shippingThe green ammonia from the desert is not to be used for the production of fertilisers for the time being, however, but is intended to replace fossil fuels in transport.Researchers from industry and science are pursuing a similar approach in the “Campfire” project, which is being led by the Leibniz Institute for Plasma Research and Technology in Greifswald. Among other things, they are currently working on a small-scale ammonia production plant that is tailored to the decentralised use of green electricity.
The ammonia will initially be used as a fuel in shipping. “We are developing ammonia drives for a sports yacht, a small inland ferry and a cruise ship,” explains project spokeswoman Angela Kruth. The drive system includes a so-called cracker, which separates the hydrogen and nitrogen molecules of the ammonia from each other on board. The hydrogen is then used in a gas engine or fuel cell to generate energy for the ships.
The ammonia-powered sports yacht is to be launched in 2022, the inland ferry is to be converted by 2025. Ammonia-powered cruise ships are to be built from 2030.
Great advantage for storage and transportBut why the detour via ammonia – why not use molecular hydrogen throughout? “Because ammonia is much easier, more efficient and cheaper to store and transport than hydrogen,” says Kruth. This happens at minus 33 degrees. Hydrogen, on the other hand, only becomes liquid at minus 253°C. In addition, less space is needed to transport ammonia than hydrogen, since the energy density is higher in relation to volume. In addition: Ammonia can be stored in large, thin-walled metal containers. Hydrogen, on the other hand, requires smaller containers that can withstand particularly high pressures and are therefore much more expensive.
The additional energy required for the detour via ammonia is low compared to the electricity required for electrolysis, says Kruth – “especially since, on the other hand, energy is saved because ammonia does not need such low temperatures for liquefaction.”The University of Duisburg-Essen is also working together with the Centre for Fuel Cell Technology (ZBT) on technologies for the production and use of green ammonia, including for the energy supply of regions without electricity grids, but ammonia has a special charm with regard to the import of CO2-neutral energy into Germany, says Florian Nigbur from the University of Duisburg-Essen. Such imports are indispensable to meet Germany’s climate targets, and politicians and industry are counting on the import of large quantities of hydrogen produced with green electricity. It is to be supplied by countries that offer better conditions for wind and solar energy – for example in Africa.
Image source: https://bit.ly/3lyc36d