Urine: Useless or useful "waste"?

Large volume of urine is continuously released into the environment by both humans and animals, and impacts negatively on the environment and ultimately on humans and animals' health. In this review, the negative impacts associated with the release of urine to the environment is highlighted. Instead of releasing urine into the environment, it has been used for several important applications. Various ways through which these waste discharge have been positively utilized such as in the synthesis of chemicals, evolution of hydrogen, power generation, source of raw materials, fertilizer application, diagnosis and treatment of diseases are comprehensively examined. Particularly, the use of urine in the synthesis of nanomaterials is emphasized. Since stabilization of urine is necessary for its application, several methods of treating and stabilizing urine are discussed. In addition, various analytical techniques used in the detection of substances present in the urine are presented. The aim of the present review is to explore different ways by which urine has been utilized so as to trigger more research findings on the other novel means of utilizing urine.