Ecological replacements of ozone-depleting substances

Halogenated aliphatic hydrocarbons have appeared in the natural environment in steadily increasing amounts over several decades as a consequence of th eir growing use, chiefly as refrigerant, foam blowing agent and solvent, pr ompted by their unique properties and low cost. It is recognised that anthr opogenic emissions of the above compounds, which are referred to as ozone-d epleting substances (ODS's), are partly responsible for depletion of the st ratospheric ozone layer and the so-called greenhouse effect. The photo decomposition of halogenomethanes in the stratosphere produces si gnificant amounts of chlorine atoms, leading to the decay of atmospheric oz one, which allows increased levels of biologically damaging UV radiation to reach the Earth's surface. The discovery of the above phenomenon has initiated efforts towards the wit hdrawal of ODS. Nowadays, it is accepted that fully halogenated chlorofluorocarbons (CFC's) are the main source of the chlorine that is eroding Earth's protecting ozo ne, and their role is of great Global concern. In spite of the fact production CFCs has been banned since 01.01.1995 and t heir use prohibited since 01.01.1996, the depletion of stratospheric ozone will continue because large amounts of these class compounds are still in u se. Therefore, the recovery and subsequent destruction of the CFCs still in use is a logical next step, in particular the conversion of the CFC's into useful products is a challenging task. At present CFCs are being replaced by hydrochlorofluorocarbons (HCFC's) and in perspective by hydrofluorocarbons (HFC's), before better replacements a re found. The environmental impact of CFC replacements is considered in ter ms of their ozone depletion potential (ODP), global warming potential (GWP) and ability to form noxious degradation products.