1 Ozone Depletion and Refrigerant Environmental Impacts
Learn how ozone depletion and climate warming differ, how refrigerant groups affect each, and why leaks and system energy use both matter.
The ozone layer and its protective role
About 90% of atmospheric ozone is in the stratosphere. This ozone layer absorbs much of the Sun’s harmful ultraviolet (UV) radiation, helping protect people and ecosystems.
The is a region of unusually low ozone, most pronounced over Antarctica in spring; it is not an empty hole. When stratospheric ozone decreases, more UV-B radiation reaches Earth’s surface. Increased exposure can raise the risks of skin cancer and cataracts and can harm some plants, marine organisms, and materials.
How chlorine-containing refrigerants deplete ozone
Some refrigerants contain chlorine. Many and persist in the lower atmosphere long enough to reach the stratosphere. There, ultraviolet light breaks them down and releases chlorine atoms, which participate in reactions that destroy ozone. A chlorine atom can take part in repeated reactions, so its effect is not limited to one ozone molecule.
CFC-11 and CFC-12 are examples of with substantial ozone-depletion potential. HCFC-22 is an example of an HCFC. generally have lower ozone-depletion potential than because their hydrogen makes them more likely to break down in the lower atmosphere before reaching the stratosphere. This does not make their ozone impact zero.
Refrigerant emissions can occur during manufacture, through leaks while equipment operates, during servicing, and when equipment is disposed of. Releasing refrigerant can cause environmental harm even when the equipment is working as intended overall.
Ozone depletion and climate warming are distinct
and measure different effects. ODP compares a chemical’s ozone-depleting effect with CFC-11, assigned an ODP of 1; a value of zero means the substance does not deplete stratospheric ozone.
GWP compares the warming effect of a given mass of a gas with the same mass of carbon dioxide over a specified time period. Carbon dioxide is assigned a GWP of 1. A refrigerant can have zero ODP and still have a high GWP, so the two measures are not interchangeable. Published GWP values can differ depending on the assessment and time horizon; the figures below are approximate and use a 100-year basis where indicated.
Environmental effects of refrigerant groups
Environmental performance varies by chemical and equipment. The groups below differ in ozone effects and climate impacts.
: High ODP; CFC-11 has an ODP of 1. Many are also powerful greenhouse gases. In the cited EPA table using the IPCC Fifth Assessment Report, the approximate 100-year GWP is 4,660 for CFC-11 and 10,200 for CFC-12.
: Nonzero ODP, generally lower than . HCFC-22 has an ODP of about 0.055 and an approximate 100-year GWP of 1,760 in the same EPA table.
HFCs: Zero ODP because they contain no chlorine or bromine that depletes ozone. Their GWPs differ considerably, and some are high. HFC-134a has an approximate 100-year GWP of 1,470 in the cited assessment. Releases, including leaks from refrigeration and air-conditioning equipment, add to climate forcing.
HFOs: Generally zero ODP. They break down more readily in the lower atmosphere than many conventional HFCs, so some have very low GWPs. HFO-1234yf is an example.
Natural refrigerants: Ammonia, hydrocarbons, and carbon dioxide do not deplete stratospheric ozone. Their direct climate effects are generally low compared with many high-GWP fluorinated refrigerants. A system’s full climate impact also depends on leakage and the energy used to operate it.
Direct and indirect climate impacts
occur when refrigerant escapes into the atmosphere. Their warming effect depends on both the amount released and the refrigerant’s GWP.
arise from the energy used to operate the system and depend partly on the electricity source and system efficiency. Choosing a refrigerant therefore involves more than comparing GWP: leakage and energy performance also matter. Evaluate refrigerants by considering ozone effects as well as climate effects, including direct leaks and energy-related emissions.