text: what is the chemical composition of human solid and liquid waste?   urine:  urine is the byproduct or fluid secreted by the kidneys, transported by the ureters to the urinary bladder where it is stored until it is voided through the urethra. it is a transparent solution that is clear to amber in colour, and usually is light yellow. urine is made up of a watery solution of metabolic wastes (such as urea), dissolved salts and organic materials. fluid and materials being filtered by the kidneys, destined to become urine, come from the blood or interstitial fluid. the composition of urine is adjusted in the process of reabsorption when essential molecules needed by the body, such as glucose, are reabsorbed back into the blood stream via carrier molecules. the remaining fluid contains high concentrations of urea and other excess or potentially toxic substances that will be released from the body via urination. urine flows through these structures: the kidney, ureter, bladder, and finally the urethra. urine is produced by a process of filtration, reabsorption, and tubular secretion.  urine contains large amounts of urea, an excellent source of nitrogen for plants. as such it is a useful accelerator for compost. urea is 10,000 times less toxic than ammonia and is a byproduct of deamination (2 nh3 molecules) and cellular respiration's (1 co2 molecule) products combining together. other components include various inorganic salts such as sodium chloride (the discharge of sodium through urine is known as "natriuresis".)  faeces:  approximately 75% of an ordinary sample of human feces is water. this percentage changes; diarrhea has more water than average and the longer the piece is in the bowels, the more water is taken out. of the remaining 25%, 1/3 (or about 1/12 of the whole) is dead bacteria. another 1/3 of the remaining quarter is undigestable food, such as cellulose.common undigested foods found in human feces are seeds, nuts, corn, and beans, mainly because of their high fiber content.