Ozone Depleting Substances: How Did We Get Here?

31 August, 2022

Ozone Depleting Substances: How Did We Get Here?


This week I want to talk more about the ozone layer and its depletion. We have taken some time to look through the kinds of substances that led to ozone layer depletion, but over the past decade, the hole in the ozone layer has also healed significantly. The purpose of today’s blog is to understand what we’ve done right, and how to keep this trajectory going.



The ozone layer was discovered to be thinning in the 1970s, and certain chemicals were linked to the depletion of ozone in the atmosphere, specifically CFCs used in industrial and consumer applications. The need to limit our use of CFCs came with the need to find suitable environmentally friendly substitutes for the same, given its wide variety of necessary functions and utility in things like fire extinguishers and refrigerators.


The urgency of the need to stop the depletion of the ozone layer resulted in countries around the world coming together to sign the Montreal Protocol and the Vienna Convention in the 1980s, the first treaties in UN history to ever achieve full ratification.


Three decades later, in 2016, reports from scientists claimed that the hole in the ozone layer has finally seen tangible self-repair and improvement. There is visible indication that the rollback of CFCs as decided per the Montreal Protocol is having a positive effect on the ozone layer, though there is still a long way to go. The ozone hole is not expected to be completely repaired before the mid-21st century.


Hydrofluorocarbons, an alternative?


The path towards this has not been straightforward, because the process of finding alternatives to CFCs has posed hurdles that have not yet been overcome. Further, existing stocks of CFCs and Halon gases continue to be used in pre-existing devices. Until recently, the use of Halon gases in fire extinguishers and fire fighting was extremely widespread. Therefore, it became important that any alternative to CFCs and halon gases be as environmentally friendly as possible.


In this light, the use of hydrochloroflurocarbons (HCFCs) and hydrofluorocarbons (HFCs) became common post the signing of the Montreal Protocol. However, it has since then been discovered that HCFCs do contribute to the depletion of the ozone layer as well, albeit to a lesser extent than CFCs. Further, HFCs also contribute significantly to the greenhouse gas effect, i.e. the overall warming of the earth’s atmosphere and temperatures rising all over. Hence, in 2016, the Montreal protocol was revised to phase out the use of both, while finding suitable alternatives to these remains a top priority.


Further Research Into Alternatives


The European Union Climate Commission lists several environment-friendly alternatives to CFCs, for different sectors, such as commercial refrigeration, centralised systems, industrial refrigeration and domestic air conditioning. Some of these alternatives include — Natural refrigerants, HFCs with lower global warming potential, Hydrofluoroolefins (HFOs), and HFC-HFO blends. The research into alternatives is ongoing, and has resulted in several industry-specific changes in the production process. Some of these are listed below:


  • Dry cleaning — while the traditionally used chemicals in dry cleaning contributed to ozone depletion, there are now several solvents that can perform the same function with much less of a negative environmental effect. Petroleum solvents are often used in this field, and require appropriate safety precautions in place due to their highly flammable nature. They include white spirit, Stoddard solvent, hydrocarbon solvents, isoparaffins, and n-paraffin.
  • Air-conditioning and heat pumps — While a specific variant of HCFCs, HCFC-22 is traditionally used in this category of devices, there are other alternatives under investigation, including non-toxic and non-flammable HCFC compounds and propane (HFC), which has a low net of global warming potential and energy efficiency capacity.
  • Metal cleaning — Before processing metal for further production processes, cleaning of metal is an essential step that usually involves solvents that include chemicals that are ozone depleting. Alternatives to ozone-depleting solvents that have been developed include solvent blends, aqueous cleaners, emulsion cleaners, mechanical cleaning, thermal vacuum deoiling, and noclean alternatives.
  • Crop fumigation — The process of crop fumigation involves CFCs and HFCs that have a tremendous negative environmental effect. Both chemical and non-chemical alternatives have been developed to this, including phosphyl and carbonyl sulfide, as well as irradiation.

This industry specific research on alternatives has been ongoing and has yielded significant results on substitutes with low global warming potential and low ozone depletion capacity.


Analysing Progress


The use of ozone depleting substances has reduced by several hundreds of thousands of tonnes in each industry, since the implementation of the Montreal Protocol, which is widely regarded as the most successful environmental agreement.


Over the course of development and implementation of new alternatives, new ways of business also develop, as seen in how many electronics companies have now converted their manufacturing plants to “no-clean” technology, as a result of which the manufacturers have saved costs in chemicals and disposal costs, and energy consumption.


For instance, the foam plastics industry, despite seeing a 45% increase in the size of the industry itself, reduced its use of CFCs by 50% between 1989 and 1993. The biggest impact on the strategic phase-out of ozone depleting substances has been through changes in commercial and industrial production policies and therefore, demand. Manufacturers which make a solid commitment to reduced use of polluting substances are also found to be encouraged by consumers who seem to tangibly care about the environmental effect of the products they consume more and more in recent decades.

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