In cellular respiration the main goal is the production of energy in the mainly in the form of ATP. The reaction of the oxidation of glucose in cellular respiration the by products produced are Carbon Dioxide and Water.
The equation for cellular respiration below
As far as the cell is concerned both Carbon Dioxide and Water are waste products. Carbon Dioxide is poisonous to the cell and must be removed for the cell to survive. Therefore Carbon Dioxide is a waste product.
However Carbon Dioxide is a valuable resource for the planet. Plants need Carbon Dioxide in order to undergo photosynthesis which produces the glucose and oxygen necessary for cellular respiration. Carbon Dioxide is also important to hold the solar energy from the sun making the earth warm enough for life to survive.