Urine is a liquid waste secreted as a byproduct of digestion and metabolism in animals and humans. It is produced by the kidneys and excreted out of the body by the urethra. The chemical composition of the urine includes the salts, sugars, excess water, albumin (protein), and bile pigments.
The excess amount of salts which are either produced by the process of metabolism or through digestion like ammonia, urea are secreted out from the body through urine.
These fuels are nonrenewable because they are limited substances which cannot be produced at the same rate at which it is used. Also, they cannot be REused, hence the wording non-REnewable. Hope this answers your question.
