Tuesday, 16 December 2014
Dr. Friedemann Call, Jan Felinks, and Dr. Matthias Lange share a vision: they plan to produce ammonia, the basic material of 90% of all fertilisers, from solar energy, air, and water. In their process, solar energy will replace natural gas which is presently used in industrial production.
The vision: fertiliser production based on solar energy
In the decades to come, the production of fertiliser will need to grow because the demand for food will rise as the global population expands.
At the same time, it is becoming increasingly difficult to step up the production of food crops because, for one thing, arable land is limited, which necessarily leads to a further increase in the use of fertilisers.
In 2013, about 2 billion kWh, or 1.6% of the total amount of fossil energy carriers used worldwide went into the production of fertilisers. If we consider in this context the imminent scarcity of fossil energy carriers we see clearly what challenges confront global food supply.
The solar researchers' vision is to produce fertilisers with the aid of solar energy in a CO2-free process. This method would contribute considerably towards the reduction of CO2 emissions worldwide and permit increasing the production of fertiliser even as fossil energy carriers become scarcer.
The key process is solar-thermal nitrogen production
The basic material of 90% of all fertilisers is ammonia, which is made from hydrogen and nitrogen by the Haber-Bosch process. The industrial production of these two substances consumes large quantities of natural gas.
The solar researchers plan to produce hydrogen and nitrogen in a thermochemical cycle in which the required energy is provided by solar radiation. While scientists at DLR and elsewhere are already working on methods of solar hydrogen production, solar nitrogen production will break entirely new ground.
Should Call, Felinks and Lange succeed in developing this process and tying it in with the Haber-Bosch method, it will be possible to produce fertiliser by a process that is regenerative and CO2-free.
How does the thermochemical cycle work?
The basic principle is to employ a so-called redox material, an auxiliary material that is capable of absorbing oxygen and releasing it again. In this case, the redox material is a metal oxide (MO). To produce nitrogen, the researchers bring the metal oxide into contact with ambient air in a reactor. The metal oxide absorbs oxygen from the air, leaving behind the nitrogen contained in the air inside the reactor.
In the next step, the metal oxide is heated in a second reactor which makes it release the oxygen it has absorbed previously. This completes the cycle.
Solar hydrogen production works by the same principle, the difference being that it is water instead of air from which oxygen is transferred to the metal oxide, leaving hydrogen behind.
In both cases, it is concentrated solar radiation that supplies the energy required for the thermal reduction process by which oxygen is withdrawn from the metal oxide, which gives it the potential of playing a key part in the global energy mix of the future.
DLR has extensive knowhow and concrete research results concerning the choice of suitable redox materials, reactor technology, the utilisation of solar energy, and overall process management. The chances of the key step, the solar-thermal production of nitrogen, proving technically feasible are rated very highly by the visionaries at the Institute of Solar Research.
Contest of Visions:
The DLR contest of visions is held every two years. Through it, the DLR Board aims to provide a hotbed for the development of creative and forward-looking ideas.
The contest is to motivate scientists to give voice to new, innovative and disruptive ideas and to develop them at DLR facilities with our financial support. Entries are welcome from all DLR employees. Selection criteria include scientific and economic relevance, feasibility of the intended technology and/or application, and benefit to DLR.
The first prize is endowed with a total funding of €240,000 extending over two years; the winners of the second and third prize receive €180,000 each. Funding for the 2015-2016 competition will be available from January 2015.