Ethylene has the largest production volume of any organic compound, at more than 150 million metric tons annually worldwide. A simple hydrocarbon gas that is extremely flammable and has a faint sweet and musky smell, it is produced by separation from the mixture of gasses that is obtained by heating natural gas or petroleum components to high temperatures.
Ethylene is also produced naturally by plants as an essential hormone that regulates processes such as seed germination, root and shoot growth, leaf growth, sex determination, flowering, fruit ripening, and the shedding of leaves and damaged parts. It additionally provides responses to environmental stresses, such as flooding, drought, and pathogen attacks. However, the amount of ethylene produced by plants is extremely small and has never been used commercially.
More than half of the world's industrially produced ethylene is used to make polyethylene, the most widely produced plastic. Ethylene is also a precursor to many important chemical products including solvents, detergents, synthetic fibers, paints, adhesives, coatings, ethylene oxide (used in sterilizing medical devices), ethylene glycol (used in antifreeze and polyester fibers) and vinyl chloride.
Both the industrial production of ethylene and the plastics and other products made from it are extremely harmful to the environment. The former is because it is produced using a highly energy-intensive process that emits large amounts of carbon dioxide. In fact, ethylene production is one of the biggest sources of industrial greenhouse gases worldwide, generating more than 260 million tons of carbon dioxide annually, accounting for nearly 13 percent of the petrochemical industry's total emissions of carbon dioxide and about 0.8 percent of total worldwide carbon dioxide emissions.
Moreover, ethylene-derived plastics release ethylene, itself a greenhouse gas, and other greenhouse gases, including methane, when exposed to sunlight. Additionally, the microplastics and chemicals that leach out of them cause substantial pollution to both the soil and water bodies.
Consequently, there has been much research into producing ethylene from renewable resources such as biomass (referred to as bioethylene) and from captured carbon dioxide using renewable energy. However, such processes are a long way from adoption because of still high costs compared to production from fossil fuels and large energy requirements. Also, production from plant sources such as corn ethanol can add to soil and water pollution due to the heavy use of synthetic fertilizers and pesticides as well as increase competition with food crops for land and other resources.