Carbon dioxide is not used and has to be removed by the lungs through the nose and mouth
Urea is one of the liquids produced by the liver when it breaks down amino acids. It is soluble and is carried in the blood to the kidneys. Where it is removed. It then is filtered and carried to the bladder.
Faeces are the leftover of food which conists of fibre and bacteria. The faeces pass out through the anus