Researchers have devised a new ‘greener’ method to make a key compound in fertilizer, and that may pave the way to a more sustainable agricultural practice as global food demand rises.

Devised by NTU researchers, the method produces a compound known as ‘urea’, which is a natural product found in the urine of mammals, and an essential compound for fertilisers that is mass-produced industrially to increase crop yields.

However, the current Haber-Bosch process used to make urea is energy-intensive, requiring temperatures of 500 degrees Celsius and pressures of two hundred times sea-level atmospheric pressure. It creates significant CO₂ emissions, contributing to approximately 2 per cent of global energy annually.

Seeking a more sustainable and energy-efficient method, the team found a way to greatly improve an existing alternative approach to urea production known as electrocatalysis — using electricity to drive chemical reactions in a solution.

Using the nanomaterial indium hydroxide as a catalyst, the researchers reacted nitrate and carbon dioxide and found that the process formed urea five times more efficiently than previously reported attempts using electrocatalysis, specifically by causing the chemical reaction to take place in a ‘highly selective’ manner.

Co-lead author of the study, Professor Alex Yan from the NTU School of Materials Science and Engineering (MSE) said, «Our method essentially manipulates the chemical reaction process to become ‘highly selective’. By picking a better catalyst, we helped the nitrate ions and carbon dioxide molecules to optimally position themselves to facilitate urea formation, while suppressing the creation of unnecessary by-products like hydrogen, leading to higher efficiency and better urea yields.»

The study findings are published in the peer-reviewed scientific journal Nature Sustainability in July, and the alternative urea production method has been patented by NTU.

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