| Carbonaceous biochemical oxygen demand (CBOD) | (Environmental Engineering) The amount of oxygen required to oxidize any carbon containing matter present in a water. |
| Carbonyl | (Environmental Engineering) A functional group with an oxygen atom double bonded to a carbon atom. |
| Catabolism | (Environmental Engineering) The production of energy by the degradation of organic compounds. |
| Cell | (Environmental Engineering) A unit of varying dimensions in a landfill which is isolated from the environment by 6 to 12 inches of soil cover. A cell is one day's waste or less. A cell is covered with soil at the end of each day. |
| CFCs | (Environmental Engineering) Chlorofluorocarbons, chemicals which result in a depletion of the ozone layer in the upper atmosphere. |
| Chemical fixation (or stabilization/solidification) | (Environmental Engineering) A term for several different methods of chemically immobilizing hazardous materials into a cement, plastic, or other matrix. |
| Chemical oxygen demand (COD) | (Environmental Engineering) The amount of oxygen required to oxidize any organic matter in the water using harsh chemical conditions. |
| Chemoautotrophic | (Environmental Engineering) Organisms which utilize inorganic carbon (carbon dioxide or carbonates) for synthesis and inorganic chemicals for energy. See autotrophic and photoautotrophic. |
| Chemotroph | (Environmental Engineering) Organisms which obtain energy from the metabolism of chemicals, either organic or inorganic. |
| Chlorofluorocarbons | (Environmental Engineering) Synthetic organic compounds used for refrigerants, aerosol propellants (prohibited in the U.S.), and blowing agents in plastic foams. CFCs migrate to the upper atmosphere destroying ozone and increasing global warming. Typical atmospheric residence times are 50 to 200 years. |