Environmental Engineering Reference
In-Depth Information
Reducing Ozone Depletion
There are aggressive steps being taken to limit CFC production, to the point that CFCs have nearly vanished
from the industrialized world. Still, there is no room for complacency. The ozone layer is not safe yet, partly
because some developing countries continue to use chemicals that destroy ozone. One option is the use of safer
CFC alternatives:
•
Hydroclorofluorocarbons (HCFCs)
replace the destructive chlorine molecule with hydrogen. Because
HCFCs still contain chlorine, they have the potential to react with stratospheric ozone. However, they
have shorter atmospheric lifetimes and tend to break down in the troposphere before delivering reactive
chlorine to the stratosphere. Still, HCFCs are seen as a temporary fix.
•
Hydrofluorocarbons (HFCs)
are compounds containing carbon, hydrogen, and fluorine. Because HFCs
contain no chlorine, they do not directly affect stratospheric ozone, and certain chemicals within this
class of compounds are viewed as acceptable long-term alternatives to CFCs and HCFCs. However,
though it is believed that HFCs will not deplete stratospheric ozone, this class of compounds has other
adverse environmental effects, including potentially contributing to global warming.
•
Hydrocarbons,
such as butane and propane are other possible alternatives to CFCs because they do not
contain chlorine and are ozone safe. They are, however, flammable and poisonous.
Replacements for CFCs, HCFCs, and HFCs continue to be investigated in the search for environmentally safe
alternatives. In the meantime, alternative compounds that can be used as coolants include helium, ammonia,
propane, and butane. In particular, helium-cooled refrigerators show promise both due to design practicality
and to the fact that helium is a noble gas and, thus, nonreactive (meaning that it will not deplete the ozone lay-
er).
Amendments to the
Clean Air Act
include requirements for the disposal of old refrigerators and air-condition-
er units and may require that older units be modified to use newer, environmentally safer coolants. Home air
conditioners are designed to have a lifetime of 20 years or more, so many older units still use the ozone-deplet-
ing Freon (R12). New products continue to be developed that are less harmful to the stratospheric ozone layer
and less harmful to the environment.
