November 14, 2018 | Solar researcher Dorottya Gubán is developing a carbon-neutral production process for fertilisers

Combating a hidden climate foe

Dorottya Gubán's fingers move swiftly and unerringly across her test station. She sets a few more parameters, then starts the infrared furnace and heats the redox material that she has developed to 800 degrees Celsius. This is one of countless series of experiments that the Doctor in Chemical Engineering has performed in the course of developing a suitable method for the sustainable production of fertiliser from the Sun, air and water.

Two to three percent of the global energy demand, and the correspondingly high level of carbon dioxide emissions, can be attributed to the production of nitrogen fertilisers. Dorottya Gubán's work as part of the DüSol project is aimed at the sustainable production of just this type of fertiliser. "Over 90 percent of fertilisers used worldwide contain nitrogen. By generating the base substance – ammonia – in a sustainable way, we can significantly reduce the emission of polluting greenhouse gases into the atmosphere," says the scientist. If it were up to her, organic fertilisers with a plant or animal origin would be predominantly used in agriculture. But she is realistic: “On a global scale, we simply cannot ignore industrially produced chemical fertilisers." Even today, around a third of the world's population eats food produced using artificial fertilisers, especially in densely populated countries where agricultural land is scarce. Experts believe that they are set to become even more important for food security in the future. "The development of a carbon-neutral production process for such fertilisers could greatly contribute towards solving our climate problems."

Nitrogen and hydrogen from solar energy

The base substance for all nitrogen-based fertilisers is ammonia (NH3), which is composed of hydrogen and nitrogen atoms. The two elements have been combined for more than a decade using the Haber-Bosch process. Gubán and her team are looking to produce the necessary elements of hydrogen and nitrogen using solar energy. There is vast potential for cutting back on climate-damaging gases, as the fertiliser industry has long used huge quantities of natural gas (mainly CH4) for this process. While scientists are working on producing hydrogen sustainably in a number of research endeavours, such as the four HYDROSOL projects, the solar-thermal process for producing nitrogen is in its very early stages of research. The DüSol project pursues the idea of using solar energy to extract nitrogen from the air, which is made up of over 78 percent nitrogen. In the process, oxygen molecules, which make up almost 21 percent of our atmosphere, are separated from the nitrogen in a thermochemical process.

The Hungarian chemical engineer clarifies that her commitment to renewable energies can be traced back to where she grew up – a suburb in Budapest surrounded by lignite mines. "That really made its mark on me. I think it is one of the reasons why I am now working on environmentally-friendly processes." She is undeterred by the fact that the sustainable production of nitrogen is still in its infancy – she is perseverant and patient. She is now working on the basic principles for such a production process and is looking for the right material. It should be able to absorb as much oxygen as possible from the air when exposed to thermal energy. This is achieved through the redox process, which is reversible in a solar energy-powered reactor. The first step is the oxidation of the material, in which the oxygen molecules are removed and the nitrogen molecules remain as a gas. In the second step, the material is reduced again, the oxygen is released and the reactor is thus 'recharged' so that the process can be repeated.

A meat grinder for material production

The decisive factor for the success of a process is not only the chemical composition of the redox material; the material structure also plays a major role in its reactivity. The scientist achieves her best results when she shapes the kneadable redox material into a granulate made up of small spheres about three millimetres across. This allows the material to offer a large surface area for the reaction. "You cannot buy this kind of granulate, so we had to find a way to produce it ourselves." Purchasing an expensive special machine would have put the project budget under too much strain. Together with her colleague Sebastian Richter, Gubán preferred to devise an in-house solution, and simply converted a meat grinder. "We worked with the DLR workshop to develop a suitable attachment and made it using a 3D printer, which allowed us to give the kneadable paste the right granulation for the production of our test materials."

"Time flies when I am working in the lab," says Gubán. She followed her Chemical Engineering degree in Budapest with a stint at the Institute of Material and Environmental Chemistry, working at the Scientific Research Centre. When she helped prepare the international Hydrogen Europe Research Annual General Meeting, she seized the opportunity to set up a Europe-wide network. She joined the company Hydrogen Research Europe, one of the three members of the private-public partnership Fuel Cell and Hydrogen Joint Undertaking (FCH-JU) in Brussels.

English translation for a yoga school

She left the lab for a year for a stint as an expert consultant. "That period was of huge benefit to me, as I learned a lot about hydrogen research in Europe and the way in which funding is granted." Gubán's doctorate formed the perfect footing for her international research work, as did her UN translation certificate for Hungarian and English: "I'm glad to have this back-up skill, even if only for translating the website of my friend’s yoga school in Budapest into English at the moment."

With the DüSol project, the scientist has made the switch back from science management to researcher, and in recent months she has discovered some promising materials by testing small samples in the infrared furnace, over many measuring cycles. Building on these endeavours, she has gone one step further and tested large quantities of samples in the solar furnace in Cologne. Her aim is to determine whether her samples can absorb the required quantities of oxygen from the atmosphere even in scaled-up, somewhat larger experiments. Bit by bit, the scientist is coming closer to achieving the optimal process. Dorottya Gubán is geared up to play the long game. She hopes that fertiliser production will gradually become more environmentally friendly. "We cannot go from 0 to 100 percent in an instant. At the moment, the most important thing is developing production processes and technologies that work, and putting them to use. That is the only way that they can spread and be further developed."

Funded by North Rhine-Westphalia federal state investment in growth and employment, with funding from the European Regional Development Fund (ERDF). Project partners are GTT-Technologies (Gesellschaft für Technische Thermochemie und -physik mbH) and aixprocess GmbH. The duration of the project is three years.


Dorothee Bürkle

German Aerospace Center (DLR)
Media Relations, Energy and Transport Research

Dorottya Gúban

German Aerospace Center (DLR)
Institute of Solar Research
Solar Chemical Engineering
Linder Höhe, 51147 Cologne