New electrochemical technology helps produce ammonia-based fertilizer from urea

Self-sufficiency in waste management and food cultivation is very important from the perspective of upcoming societies, particularly in highly closed surroundings, like a space station. However, there is still a dearth of technology to realize this dream.

Fertilizer

Fertilizer. Image Credit: oticki/Shutterstock.com

In a recent study, Japanese scientists have provided a better understanding of their latest breakthrough—an efficient and economical technique to make liquid fertilizers (such as ammonia) from streamlined artificial urine, providing an ideal dual-purpose method for growing food and also for treating waste.

In adverse surroundings, even the most routine jobs can appear to be insurmountable challenges. Due to these challenges, humans have largely settled on grounds that were conducive for building shelters, herding cattle, and harvesting crops.

However, as humans look for ways to widen the limits of their exploration, both in space and on the Earth, the people who pioneered this quest will certainly encounter conditions that, in effect, are not favorable to human habitation.

But one of the major difficulties facing any proposed long-term settlement—be it on Mars (maybe in the near future) or in the Antarctic—is achieving some level of autonomy to allow the survival of isolated colonies even during a disastrous failure in provisioning. And this level of autonomy can be achieved by ensuring self-sustenance and food sufficiency.

Therefore, it is no wonder that space agricultural technology is one of the many research topics that are presently being handled by the Research Center for Space Colony at Tokyo University of Science.

The investigators at this center are hoping to drive the technological advancement to ensure safe and sustainable space agriculture, with the goal of sustaining human beings in highly closed surroundings, like a space station, for a long time.

As such, a novel study was carried by a group of Japanese investigators headed by Norihiro Suzuki, a Junior Associate Professor from the Tokyo University of Science. Published in the form of a “Letter,” the study featured on the front cover of the leading New Journal of Chemistry of the Royal Society of Chemistry.

In the latest study, Dr. Suzuki and his group aimed to deal with the issue of food production in closed surroundings, like those found in a space station.

When Dr. Suzuki and his team realized that farmers have been using animal waste as fertilizer, which serves as a rich source of nitrogen, for many years, they started to investigate the feasibility of producing this animal waste from urea (the key component of urine), to create a liquid fertilizer. This approach would also help overcome the issue of human waste management or treatment in space.

This process is of interest from the perspective of making a useful product, i.e., ammonia, from a waste product, i.e., urine, using common equipment at atmospheric pressure and room temperature.”

Dr Norihiro Suzuki, Junior Associate Professor, Tokyo University of Science

The team, which also included Akihiro Okazaki, Kai Takagi, and Izumi Serizawa from ORC Manufacturing Co. Ltd in Japan, developed a new “electrochemical” process to extract ammonium ions (generally found in typical fertilizers) from a sample \of artificial urine.

The researchers created a simple experimental setup—one side had a “reaction” cell, with a “boron-doped diamond” (BDD) electrode and a “photocatalyst” material composed of titanium dioxide or light-inducible catalyst, while the other side had a “counter” cell with a basic platinum electrode. When current flows into the reaction cell, the urea gets oxidized and forms ammonium ions.

Dr. Suzuki has explained this innovation as follows, “I joined the 'Space Agriteam' involved in food production, and my research specialization is in physical chemistry; therefore, I came up with the idea of 'electrochemically' making a liquid fertilizer.”

The team subsequently investigated whether the cell would perform more efficiently in the presence of the photocatalyst, and they achieved this by comparing the cell reaction both with and without the photocatalyst.

The researchers observed that while the preliminary depletion of urea almost remained the same, the resultant nitrogen-based ions varied both in terms of distribution and time, in the presence of the photocatalyst.

Most significantly, the level of nitrate and nitrite ions was not as high in the presence of the photocatalyst. This indicates that the presence of the photocatalyst supported the formation of ammonium ions.

We are planning to perform the experiment with actual urine samples, because it contains not only primary elements (phosphorus, nitrogen, potassium) but also secondary elements (sulfur, calcium, magnesium) that are vital for plant nutrition!”

Dr Norihiro Suzuki, Junior Associate Professor, Tokyo University of Science

Dr. Suzuki and his group are, therefore, optimistic that the new technique offers a strong basis for producing liquid fertilizer in enclosed environments, and, as observed by Dr. Suzuki, “It will turn out to be useful for sustaining long-term stay in extremely closed spaces such as space stations.”

Human beings inhabiting the Mars planet may still be a remote reality, but the new study certainly appears to indicate that they might be closer to ensuring sustainability in space, even before they actually reach there.

Source:
Journal reference:

Suzuki, N., et al. (2020) Formation of ammonium ions by electrochemical oxidation of urea with a boron-doped diamond electrode. New Journal of Chemistry. doi.org/10.1039/d0nj03347b.

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