Ammonia from renewable energies: Colorless, but green. Like hydrogen, ammonia is a colorless gas, but it has a pungent odor and is referred to as "green" depending on the manufacturing process and the energy used to produce it: "At the moment, ammonia is mainly produced from natural gas, but green ammonia requires no fossil resources at all, " explains Thore Lohmann, Executive Director Fertilizer & Methanol at thyssenkrupp Uhde. "All you really need is green electricity, air, water, and the right expertise. More precisely, you extract nitrogen from the atmosphere (N2), hydrogen from water electrolysis (H2), and combine the two to make green ammonia. (NH3)"
In everyday life, some of us have encountered ammonia while baking gingerbread. This is because the baking agent used for the gingerbread dough, staghorn salt, smells faintly of the chemical. However, pure ammonia in large quantities is not for the end consumer and is intended exclusively for industrial use with appropriate safety standards. In industry, ammonia performs many different tasks and is used primarily in fertilizers. The so-called nitrogen fertilizers are important in many parts of the world to keep soils fertile. But ammonia is also used as a refrigerant, for example in indoor ice skating venues.
A glimpse into the future: Green ammonia holds great potential
In the future, ammonia will take on another important function - as a means of transporting green hydrogen. To meet the growing demand for green hydrogen to transform high-emission industries into more sustainable ones, Europe and Germany in particular, need to import green hydrogen from other countries. There is just one problem: Transporting hydrogen over long distances is extremely costly, explains Lohmann: "For transport in large quantities, the gas has to be liquefied at -253 °C." This cooling requires an extremely high amount of energy. In addition, some of it is constantly evaporating, so losses occur.
"Ammonia can be used to transport much larger amounts of energy in less space because, relative to volume, the energy density of ammonia is much greater than that of liquid hydrogen," explains Lohmann. Ammonia already liquefies at -33 °C and can be stored and transported more easily. Liquid hydrogen, on the other hand, consumes up to an additional 40% of the energy content to be transported in this way due to the extreme cooling.
Another advantage of ammonia: "Many millions of tons of ammonia are already transported by ship every year. The necessary infrastructure is already in place and safe handling has been established and practiced worldwide for decades," says Lohmann.
Energy in chemical form: That is Power-to-Ammonia
The transport of green ammonia is therefore not only easier, but also safer and more cost-effective than that of green hydrogen. How transport works with the so-called power-to-ammonia process? Hydrogen is produced from renewable energies by means of electrolysis.
In parallel, nitrogen is simply extracted from ambient air using an air separator. This process is carbon-free and green ammonia is produced - a climate-neutral energy carrier.
In other words, the renewable energy is stored in chemical form as ammonia. After transport, the green ammonia is easily converted back to green hydrogen and can be used as a climate-neutral energy carrier in numerous industrial processes. For example, in the steel, cement and chemical industries. Direct use is also possible, for example as a climate-neutral marine fuel, or in the turbines of gas-fired power plants. Proper combustion of ammonia produces only water and nitrogen.
Prerequisites for a successful energy transition
thyssenkrupp Uhde already builds many of the world's largest plants for the production of green ammonia, more than 130 in total. "We can currently produce up to 5,000 metric tons of green ammonia per day in a single plant," says Lohmann. Looking to the future and the chemical's new role, however, these capacities are not yet enough to meet the rapidly growing demand for ammonia in the future. That is because, in addition to hydrogen transport, ammonia remains important for fertilizer production.
Therefore, thyssenkrupp is constantly working to expand production capacities. In addition to the construction of new plants and the conversion of existing ones, however, in the future there must above all be a great deal of renewable energy, more ships and terminals so that green ammonia can develop its full potential for the energy transition, says Lohmann.