Some of the most damaging substances we have spewed into the air are chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and bromine. These chemicals destroy stratospheric ozone, which protects us and the animals from solar ultraviolet radiation. This dilemma was created by the solution to a problem for the refrigeration and air-conditioning industry.
Before CFCs were developed in the 1920s, dangerous chemicals such as sulfur dioxide and ammonia were used as refrigerants. After Thomas Midgeley developed CFCs, many uses were found for the new chemicals. These uses, such as refrigerants in refrigeration chillers and air-conditioning equipment, and propellant in aerosol cans, generally allowed the CFCs to escape into the air at some point during use. The chemicals end up in the stratosphere where they can destroy ozone, which allows more ultraviolet radiation to strike the Earth's surface.
The Earth's atmosphere is composed of several layers. The lower layer is called the troposphere and extends to an altitude of approximately 36,000 feet. The next layer extends to 30 miles and is called the stratosphere. The part of the atmosphere referred to as the ozone layer exists in the stratosphere. The ozone layer starts at approximately 15 miles and extends to 30 miles. In this region is the highest concentration of ozone. Even though the concentration is high, the ozone only constitutes one-millionth of the atmosphere (Somerville, 1996). While ozone is rare, it has the important function of shielding the Earth from solar ultraviolet radiation. This shielding protects all the living organisms that inhabit the planet, including all animals and humans.
Ozone Formation and Destruction
Ozone is the triatomic form of oxygen, meaning it consists of three oxygen atoms, and is identified chemically as O3. In the troposphere, where we live, ozone is a form of pollution. Ground level ozone is an end product of private and industrial energy consumption. Stratospheric ozone is formed naturally. Ozone is formed when single oxygen atoms combine with the diatomic, or normal, form of oxygen (O2). Single atoms are formed when diatomic oxygen absorbs solar ultraviolet radiation (Somerville, 1996). This process is called dissociation, and the chemical equation is written:
O2 + UV => O + O
The free oxygen atoms then combine with diatomic oxygen:
O + O2 => O3
Ozone is destroyed naturally by two different processes. The first is when a free oxygen atom combines with an ozone molecule to produce two diatomic oxygen molecules:
O + O3 => 2O2
The other process in which ozone is destroyed is when ozone molecules absorb ultraviolet radiation and form one diatomic oxygen molecule and one free oxygen atom:
O3 + UV => O2 + O
The time interval between the formation and natural destruction of ozone varies greatly. Ozone molecules can have a lifetime of only a few minutes, or they can survive for several months. The average life of ozone is eleven days (Rowland, 1997).
In 1928, Thomas Midgeley, Jr. was trying to develop a refrigerant that was non-toxic, non-corrosive, non-flammable, and chemically inert. Prior to Midgeley's research, substances such as sulfur dioxide and ammonia were used in domestic refrigerators. These refrigerants were toxic and/or flammable, creating a safety concern (Cox and Miro, 1997). Midgeley used the characteristics of the elements in the periodic table to create a new class of refrigerants. These new refrigerants were called chlorofluorocarbons (CFCs). CFCs made ideal refrigerants, and over time they have been used as propellants in aerosol cans and solvents in the electronics industry, as well as refrigerants for domestic, industrial, and automotive air-conditioning systems.
As CFCs were used, they were eventually discharged into the atmosphere. Whenever refrigeration systems were drained, the refrigerant was allowed to escape. The CFCs in aerosol cans were dispelled with the product. The production of CFCs during the mid-1960s had reached a level of 300,000 tons per year (Rowland, 1997).
Most molecules that are propelled into the atmosphere are removed within a few hours to a few weeks by three general processes (Rowland, 1997). The first process is called photolysis, which is when the molecule absorbs sunlight. The second process is dissolution in water, or rainout. The final way molecules are removed is through a reaction with the hydroxyl radical (HO) and ozone, a process called oxidation. CFC molecules differ from most molecules in that they are transparent to sunlight, are insoluble in water, and are chemically inert to oxidizing agents. Therefore the aforementioned processes will not remove them from the atmosphere. The molecules can remain in the lower atmosphere for a long time before being pushed into the stratosphere by powerful storms at the equator.
CFCs and Ozone
In the stratosphere, CFC molecules absorb an intense, highly energetic solar ultraviolet radiation called UV-C (Rowland, 1997). UV-C is not present near the Earth's surface because it is absorbed by the ozone layer in the stratosphere. The CFC molecule is destroyed as it absorbs the UV-C. The chemical equation for the reaction with CFC-11, commonly referred to as R-11, is:
CCl3F + UV => Cl + CCl2F
The free chlorine atom then attacks an ozone molecule, and the reaction yields a chlorine monoxide molecule (ClO) and a diatomic oxygen molecule:
Cl + O3 => ClO + O2
After destroying the ozone molecule, the chlorine monoxide molecule will react with a free oxygen atom to form a free chlorine atom and one diatomic oxygen molecule:
ClO + O => Cl + O2
These last two chemical processes can take place 100,000 times for each chlorine atom that is freed from a CFC molecule. Given the natural destruction of ozone, coupled with the destruction from man-made compounds, the average lifetime of an ozone molecule is reduced from eleven days to nine or ten days. Bromine atoms carried into the stratosphere in halon molecules go through the same type of process as chlorine atoms. The difference is that bromine is ten times more powerful an ozone destroyer than chlorine.
The Earth is a very dynamic planet. The interaction of so many dynamic processes make it extremely difficult to forecast how a small change in one process will affect the entire planet. This is why environmental damage predictions are so controversial. While the relationship between CFCs and ozone has been accepted by most people, and a solution enacted, the relationship between GHGs and global warming is not as clear.
Some scientists hypothesize that the amount of CO2 in the atmosphere is cyclical and has been changing since the atmosphere came into existence. The CO2 content was high until grasses started to grow on the planet. These grasses lowered the CO2 level until herbivores evolved. The herbivores raised the CO2 level through respiration and eating the grass that was removing CO2. The evolution of carnivores and flowering plants caused the level to lower again. Man, by killing plants through deforestation and land development, has caused the CO2 level to rise once more. Therefore, the rise in CO2 is considered by some to be a natural phenomenon.
Few people dispute the fact that the average temperature of the planet has increased 0.9 to 2.7°F in the last 100 years (Brower 1990, p. 11). What is disputed is why the temperature has risen. The last ice age ended 8,000 years ago, and the warming could be a result of this ending. Researchers have found temperature changes of up to 25°F in 30 to 40 years occurring in the past (Roleff 1997, p. 50). These findings are from examinations of sediment deep in the ocean and polar ice core samples. The slight warming we have experienced is small when compared to the much larger changes in the past.
Another problem with the temperature rise experienced are the cooling effects that my have mitigated some of the warming. Suspended particulates such as sulfur dioxide form what is referred to as the "aerosol parasol" over population centers. These particles cause UV radiation to turn into heat in the upper atmosphere, causing the planet to cool. Computer models of global climate predicted a larger temperature rise until aerosols were taken into account (Roleff 1997, p. 50).
The predicted results of global warming are even controversial. The United Nation’s Intergovernmental Panel on Climate Change has made predictions of what could happen due to global warming (Roleff 1997, p. 34). Rainfall patterns could shift dramatically, causing arid places to become drier and wet areas to become even wetter, or vice versa. Areas that are prone to flooding could experience worse flooding. Storms and hurricanes could become more severe in the future. Winters could become warmer, causing the polar caps to melt, thus raising the water level in the oceans. Although the estimates of temperature rise vary from 0 to 6°F in the next century, some people believe this warming would be beneficial. Warmer weather in the regions closer to the poles would be welcome by the inhabitants. This would also lengthen the growing season, allowing more food to be produced.
The opinions on what is actually happening to the climate vary widely. If these changes are natural, we can all relax and see what happens. If humans are causing these changes, though, we need to curb our emissions by modifying our behavior and developing alternative fuel sources. Hopefully further research will determine which scenario is taking place before it is too late.
Alternative Fuel Sources
There exist several alternative fuels that can be used instead of fossil fuels. These fuels have characteristics that make them more desirable because they are more friendly to the environment. Each is renewable and non-polluting.
Every day enough sunlight falls on the United States to provide all of the country’s energy needs for an entire year (Brower 1990, p. 28). Solar power can be used in three ways: Solar buildings, solar collectors, and photovoltaic cells. Solar buildings are built to catch as much sunlight as possible. Rooms with large amounts of glass and masonry floors are positioned on the south side of the building. The glass allows sunlight in and the masonry holds the heat. At night the heat is released to provide space heating.
Solar collectors are built on roofs and also collect sunlight. The top of a solar collector is covered with glass and the inside is painted black. Piping inside the collector heat up and a refrigerant flowing through the pipes collects the heat and transports it to a storage bin. The bin contains rocks or salt that can hold the heat for later use.
Photovoltaic cells are used to turn sunlight directly into electricity. The cells contain semiconductor material that can lose electrons to set up an electric current. The power generated can be stored in batteries until needed.
The wind blowing across the country could provide forty times the energy needed each year if harnessed properly (Brower 1990, p. 46). Generators can be mounted on towers in areas away from cities. A propeller attached to the generator turns as the wind blows past. Any electricity not used immediately can be stored in batteries.
Biomass is material from plants that can be used for energy. Plants can be converted to gases and liquids that can be used instead of natural gas and petroleum (Brower 1990, p. 53). Biomass can come from several sources, such as waste from forestry operations and farming, or energy farms that grow plants specifically for energy usage.
Several processes can be used to obtain usable fuels. The simplest method is to burn the biomass. While this will release CO2, the same amount of gas will be absorbed when new crops are grown. One drawback is the pollution that is also emitted. This technology is being put to use already. A recent news story told of a plan to burn genetically altered artichoke plants to generate electricity in Europe.
Another process to convert biomass is thermochemical conversion. This process involves heating the mass in different atmospheres to obtain fuel. The fuels produced using thermochemical conversion include methanol, syngas, low-Btu gas, and medium-Btu gas. Modern boilers can be converted to use these gases.
Biochemical conversion will create methane or ethanol. Ethanol is mixed with gasoline to make gasohol. Also, oils can be obtained from plants such as sunflowers, soybeans, and winter rapeseed. These oils can be used as a cleaner burning fuel for diesel engines (Brower 1990, p. 63).
Other Alternative Fuels
Hydroelectic dams can be built on many rivers to provide electricity. However, there are many problems with hydroelectric dams. The dams change the river ecosystems by blocking sediments, changing river flow rates, and blocking fish migration (Brower 1990, p. 70). Technologies exist to mitigate these problems, but not all can be overcome.
Tidal power can also be used to generate electricity. Vertical pipes housing propellers are placed in the ocean with the bottom in the water. As the water rises air is forced up through the pipe. When the water falls again, air is pulled back in. The propeller is designed so it will turn the same direction no matter which way the air flows.
Third part of The Industrial Revolution: An Environmental catastrophe?
Written May 30, 2000
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