Extracting fertiliser from ‘liquid gold’ urine in wastewater

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Photo by Fulvio Ciccolo on Unsplash
Photo by Fulvio Ciccolo on Unsplash

Researchers have developed a way of purifying urban wastewater and extracting a valuable product from urine — which could be used to fertilise crops, among other applications, according to the team. They say their findings present a new, potentially scalable and cost-effective approach to large-scale wastewater treatment with economic and environmental value. The new process involves using an electrochemical reaction to remove a chemical called urea from wastewater and transform it into nearly 100% pure percarbamide, which could have various useful applications, including environmental water treatment, disinfection, and improved crop growth.

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From: Springer Nature

Chemistry: Extracting fertilizer from ‘liquid gold’ urine

A mechanism to purify urban wastewater and extract a valuable product from urine — which could be used to fertilize crops, among other applications — is reported in Nature Catalysis. The findings present a novel and potentially scalable and cost-effective approach to large-scale wastewater treatment with economic and environmental value.

Urine contains the chemical urea, which is rich in nitrogen, an important component of fertilizer. Urine is referred to as ‘liquid gold’ in certain contexts, owing to its potential use in agriculture, however it is commonly considered as a waste product. Storing vast amounts of urine, and the mechanisms to process urea into useful chemicals, have been a challenge for wastewater treatment engineering.

Xinjian Shi and colleagues used an electrochemical reaction to remove urea from wastewater and transform it into nearly 100% pure percarbamide, a useful solid derivative of urea, bypassing the need for complex purification steps. The collected percarbamide could have various useful applications, including environmental water treatment, disinfection, and to improve crop growth. The reaction utilised a carbon-based electrode to serve as a catalyst and atmospheric oxygen to generate the percarbamide under temperatures and pressures lower than traditional reactions. The system was found to work with both human and mammalian urine, is cheaper and produces a purer and more valuable final product, compared to other methods. Following an economic analysis, Shi and colleagues calculate that daily production of one metric ton of percarbamide would require only 100 square meters of land, and the urine collection from about 6,382 houses or a farm of 3,800 cows, highlighting the feasibility of this method.

The findings lay the foundations for future studies to focus on improving the efficiency and scalability of this process. Further advancements could lead to more sustainable urban wastewater management practices and innovative uses of recovered materials.

Journal/
conference:
Nature Catalysis
Research:Paper
Organisation/s: Henan University, China
Funder: X.S. acknowledges the National Natural Science Foundation of China (52202229), International Postdoctoral Exchange Fellowship Program (YJ20220090), the China Postdoctoral Science Foundation (2022M721011) and Department of Human Resources and Social Security of Henan Province for Preferential Funding for Overseas Researchers and Zhongyuan Talent Plan project. X.S. also acknowledges the fund supported by Henan University, PeroPure and Wison Offshore & Marine Ltd. Y. Jiang acknowledges the support from the National Natural Science Foundation of China. B.Z. acknowledges S. Chen for electron microscopy tests and analysis, and X. Li for drawing and enhancing images. P.L. acknowledges support from the National Natural Science Foundation of China (12204151) and the Open Project Program of Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices, Huizhou University (EFMD2022009M). Y. Jia acknowledges support from the National Natural Science Foundation of China (12074099).
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