NEW DELHI: Twenty years after coming up with a new generation of chemicals to protect the ozone layer, the world is now confronted with the fact that these ozone-friendly substitutes for chlorofluorocarbons (CFCs) also happen to be greenhouse gases that contribute to global warming.

This has been revealed by a United Nations Environment Programme report, "Safeguarding the ozone layer and the global climate system: Issues related to hydroflourocarbons (HFCs) and perflourocarbons (PFCs)," brought out by the Intergovernmental Panel on Climate Change in collaboration with the Technology and Economic Assessment Panel.

Safer alternatives?

Under the Montreal Protocol, Governments are phasing out CFCs, halons and other destructive chemicals and replacing them with safer alternatives. However, some of them such as hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) are also powerful greenhouse gases, the report said.

For this reason, the HFCs and PFCs were included in the 1992 Climate Change Convention and the 1997 Kyoto Protocol, under which most developed countries have to reduce emissions from a basket of six greenhouse gases by 2008-2012.

According to the report, the emissions of CFCs and their replacements can be minimised by improving the containment of chemicals to prevent leaks, evaporation and emissions of unintended by-products, increasing the use of ammonia and other alternative substances with a lower or zero global warming potential and using various emerging technologies that avoid gases that deplete ozone or contribute to climate change.

The problem of ozone depletion arose from the wide-scale application of stable, non-flammable chemicals to refrigeration, air-conditioning, foams, aerosols, fire protection and solvents starting in the middle of the last century.

Though the HCFCs were successful in meeting the early CFC phase-out goals, they are generally considered undesirable for most new equipment because of their ozone-depleting potential. They will eventually be phased out under the Montreal Protocol.

As the HFCs and PFCs contain no chlorine or bromine (the main culprits in ozone depletion), they have been among the substitutes considered for the long-term. Unfortunately, they are also greenhouse gases.

Lower emission levels

Chemically, the CFCs and many of their replacements are more powerful greenhouse gases than carbon dioxide, but the emission levels are lower. The contribution of CFCs, their replacements and other ozone-depleting substances to global warming is estimated to be about 10 per cent of that of fossil fuel-related carbon dioxide emissions or around five per cent of humanity's total greenhouse gas emissions.

Since virtually all ozone-depleting substances and their replacements are now used in closed systems, they are generally not emitted until years or even decades after being produced. For instance, large amounts of CFCs still exist in current refrigeration and air-conditioning equipment and in insulating foams, from which they can leak or evaporate.

Later, when the equipment is decommissioned, they are often simply released into the atmosphere. There are no regulations for the CFCs and HCFCs under the Montreal or Kyoto Protocols to prevent such emissions.

About 65 per cent of the total emissions from this group of chemicals still come from CFCs, mainly from existing refrigeration and air-conditioning equipment.

Consequently, reducing leaks from these sources could substantially reduce greenhouse gas emissions, benefiting both the ozone layer and the climate system, the report suggests.

The HCFCs and HFCs are estimated to contribute 20 per cent and 15 per cent of emissions from this group of chemicals. By 2015, however, as much as 50 per cent may decline from HFCs, with 40 per cent from HCFCs, depending on which substitutes and technologies are used. The CFC emissions will likely decline to around 10 per cent due to the phase-out of new uses and reduced releases from stored amounts.

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