carbon dioxide from the air is used to produce glucose and other  compounds.
Blood Filtration in the Kidney. The kidneys filter about one-quarter (750-1000 pints) of the blood that is output by the heart daily. This blood is sent to the body's filter treatment plant, where it is purified by the kidneys and circulated on to the rest of the body. Some of the blood flow becomes fluid waste (1/1000th to 2/1000th) and is sent into the bladder for storage until it can be conveniently expelled. This toxic waste is called urine.
This is where the blood is filtered through the kidney tubules (the nephron) where the constituents of the blood are excreted or reabsorbed. The majority of the Na and water reabsorption occurs in the part of the tubules that are located in the renal medulla. Whatever is reabsorbed during this filtration body is taken back up into the blood and transported back into the body.