Carbon dioxide (CO2) is a chemical compound made up of one carbon atom covalently double bonded to two oxygen atoms. It is a natural greenhouse gas that is harmless in small quantities, but as levels rise, it can affect productivity, sleep, and infectious disease transmission. Carbon dioxide is one of the most important gases on Earth because plants use it to produce carbohydrates in a process called photosynthesis, which is necessary for the survival of life on Earth.
Carbon dioxide is found in the gas phase at standard temperature and pressure conditions. It is a by-product of the fermentation of sugar in the brewing of beer, whisky, and other alcoholic beverages, and in the production of bioethanol. Carbon dioxide is also a byproduct of the industrial production of hydrogen by steam reforming and the water gas shift reaction in ammonia production. These processes are a major source of food-grade carbon dioxide for use in carbonation of beer and soft drinks and are also used for stunning animals such as poultry.
Carbon dioxide is an important heat-trapping gas, also known as a greenhouse gas, that comes from the extraction and burning of fossil fuels (such as coal, oil, and natural gas) and from wildfires. Less than 1% of Earths atmosphere is carbon dioxide gas.
