Impact of Automobile Exhaust on Global Warming
Global warming phenomenon has various adverse effects such as severe storms, prolonged periods of drought. GHG increase, primarily carbon dioxide is attributed to the phenomenon of global warming. In elucidating the role of automobile exhaust in global warming, this article evaluates the components of the automobile exhaust gas that comprise of GHG. Carbon dioxide, nitric oxide, methane and black soot were found to be key components of automobile exhaust emissions. Evaluation of previous literature also shows that these components of automobile exhaust are the primary GHG components. Therefore, the role of automobile exhaust in global warming is by its role in increasing the concentration of these components.
Climate and weather have an indispensable role in ensuring conducive environmental conditions for living organisms on earth. The life of organisms is dependent on climate. Changes in the climatic conditions resulting from global warming have jeopardized living conditions organisms. According to Beliveau (2010), climatic conditions have progressively been changing and has attracted the attention of the world in formulating ways of reducing such changes from human activities. The occurrence of such as momentous shrinking of mountain glaciers and polar ice caps, prolonged drought period in arid areas and frequent severe storms indicate some of the adverse effects of the progressive increase in global warming. Moreover, volcanic spots and geothermal vents are adverse effects resulting from global warming due to human activities. Changes in climatic conditions cause corresponding changes in the ecological systems and may be disastrous to organisms (Wallington et al., 2004).
Climatic changes occur due to enhancement of the greenhouse effect resulting from emission of greenhouse gases. Greenhouse effect refers to a phenomenon by which heat is trapped in the lower parts of the atmosphere. Various sectors emit greenhouse gases (GHG). Such sectors include and not limited to electricity, transportation, industry, commercial and residential and the agricultural sector (EPA, 2015). The transportation sector is the second leading emitter of greenhouse gases after electricity. However, the transportation sector emission is expected to increase with the rise in the number of automobiles. EPA (2013) explains that emission of GHG by automobiles has had the highest increase compared to other sectors. There are three types of emission of greenhouse gases by the automobiles. These include the crankcase, evaporation and exhaust emissions (Bhandarkar, 2013). Crankcase emission refers to the escape of partially of fully unburnt components of fuel that enters the crankcase resulting in the emission of hydrocarbons. Evaporative emission refers to the constant release of hydrocarbon vapor due to the volatile nature of the fuel. The exhaust emission results from the combustion process of the fuel.
The exhaust emission is the primary emitter of automobile greenhouse gases. Bhandarkar (2013) explains that exhaust emissions account for about 60% of the total emissions by automobiles. This paper seeks to explore the role of exhaust emissions in global warming. In achieving this, the paper considers the various greenhouse gases that are associated with enhancement of the greenhouse effect. Moreover, the paper gives a summary of the initiatives that can be implemented to reduce the emission of greenhouse gases.
Global Warming: Evaluation of constituents of automobile exhaust and their role in global warming
According to EPA (2013), greenhouse emission from automobile exhaust accounts for 27% of all the GHG emitted. The largest automobile emitters were the light-duty vehicles that account for 61% of all the emissions. Medium and the heavy-duty emission of the GHG account for 22% of all the emissions from the transportation sector. The various primary GHGs emitted from automobile exhausts include carbon dioxide, nitrous oxide and methane. Moreover, particulate matter and traces of sulphur dioxide, and chlorofluorocarbons, water vapor are also emitted in automobile exhaust (Beliveau, 2010; Bhandarkar, 2013). In 2013, Bhandarkar explained that hydrocarbons and carbon dioxide result due to incomplete combustion of fuel. Nitrogen oxides occur due to a reaction of oxygen and nitrogen at high temperatures in the combustion air. The following sections explore the various GHG automobile exhaust emissions.
Carbon Dioxide and Carbon Monoxide
According to EPA (2015b), carbon dioxide is the primary GHG. Carbon dioxide is naturally present in the atmosphere and plays a role in the carbon cycle. However, there has been a drastic increase of carbon dioxide concentration due to automobile exhaust emissions. An average of 96% of all the exhaust emissions by automobiles comprise of carbon dioxide. Motor Vehicle Exhaust Emissions (2005) explains that carbon dioxide results from combustion of fossil fuels. Carbon in the fuel combines with oxygen in the engine to produce carbon dioxide. Moreover, carbon monoxide is also emitted from automobile exhaust. It results due to incomplete combustion of fuel. Carbon monoxide is oxidized to carbon dioxide immediately after its release.
Carbon dioxide plays a critical factor in absorbing heat in the atmosphere and hence heating it (Lu, 2011). An increase of carbon dioxide in the atmosphere will hence result in a rise in the heating effect due to its heat absorption capabilities (EPA, 2015b). Consequently, there is a corresponding increase in temperature characterized by such as polar ice and glaciers melting. Moreover, carbon dioxide causes depletion of the ozone layer (Motor Vehicle Exhaust Emissions, 2005). Depletion of the ozone layer causes penetration of the ultraviolet rays from the sun that is then absorbed by the increased carbon dioxide to causing heating.
Methane is the second most prevalent GHG emitted by automobile exhausts after carbon dioxide. As mentioned earlier, it results from combustion of fossil fuels in the automobile engines. The reaction ability of the hydroxyl group (OH) in methane is the most critical aspect of its effect on global warming (Wallington et al., 2004). An increase in methane results in decreased OH and hence increasing the lifetime of other GHG and hence prolonged global warming effect (EPA, 2015b). Moreover, methane plays a role in the production of more ozone layer that contributes to global warming. Methane also has extremely effective capabilities of absorbing radiation (Anonymous, n.d.). Therefore, an increase in its concentration would result in higher absorption of radiation causing increase in temperature.
During combustion in automobile engines, high temperatures and pressure in the presence of surplus oxygen causes oxidation of natural nitrogen from the atmosphere forming nitrogen oxides. These oxides include nitric oxide and nitric dioxide. Nitric oxide is oxidized to form nitric dioxide (EPA, 2015b; Lu, 2011). Nitrogen oxides are often hard to control due to an increase in their emission with progressive improvement of combustion process as an attempt to reduce GHG produced (Motor Vehicle Exhaust Emissions, 2005). This increase in the nitrogen oxides produced is due to increase in temperatures in the improved combustion processes. Higher temperatures imply an increase of nitrogen oxide produced.
Nitric dioxide is the third most prevalent GHG (Wallington et al., 2004). According to Suddick et al. (2013), nitric acid is 300 times more potent than carbon dioxide. Moreover, this GHG is of concern due to its long resilience time of about 130 years (Lu, 2011: Suddick et al., 2013). Nitric acid results in a modest cooling effect for a short period of about 20 years and long-term warming effect of about 100 years. The effect of nitric acid is mainly through its effect on the concentration of ozone and methane that are responsible for the maintenance of temperature.
Black Carbon (Soot)
Automobiles often produce soot that results from the lack of combustion of carbon producing it as an element (McCarthy & Yacobucci, 2014). Soot can absorb solar radiation and reduces the reflectivity of ice and snow. Consequently, there is increased global warming due to the resulting heating effect of the two factors.
The various GHGs considered contribute to enhanced greenhouse effect through their ability to affect radiation reaching the earth’s surface and their absorptive capabilities. The net radiation that reaches the earth’s surface determines the amount of energy that is available for the atmospheric heating (Wallington et al., 2004). GHG increase in the atmosphere alters the radioactive balance on earth. These gases are transparent to incoming radiation from the sun while absorbing the earth’s longwave radiations. The resulting radioactive forcing contributes to increased atmospheric temperature and hence global warming.
Due to the emission of GHG in the atmosphere by automobile exhausts, it would be prudent to reduce the emission rate. Such reduction of GHG emission rates can be achieved by such as fuel switching to that that causes less carbon dioxide emission. Technology can also be improved to ensure efficient combustion process (EPA, 2015c). Moreover, McCarthy and Yacobucci explain that eliminating aerodynamic drag, rolling resistance reduction and addressing operational factors would help to reduce GHG emission by automobile exhausts.
The burning of fossil fuel by automobile has been shown to result in the emission of gases that have a global warming effect. The gas component of the automobile exhaust has been shown to comprise carbon dioxide, nitric dioxide, methane and black soot. Automobiles result in a progressive increase in the concentration of these gases in the atmosphere. These gases comprise the primary greenhouse gases that have been attributed to climatic changes due to global warming. Carbon dioxide has been highlighted as the primary gas emitted by automobile exhausts. Moreover, carbon dioxide has been shown as the primary GHG.
Therefore, as mentioned above, automobile exhausts emissions result in an increase in GHG concentration in the atmosphere. Consequently, the heating effect resulting from the increased GHG concentration hence causes an increase in temperature causing the global warming phenomenon. Moreover, automobile exhaust emissions such as methane cause depletion of the ozone layer causing more radiation to reach the earth causing more heating. Ozone depletion also causes faster cooling of the atmosphere as the longwave radiations from the earth’s surface escape. However, this phenomenon of cooling only occurs for a short-term period as more carbon dioxide, and ozone is formed compared to that which is depleted. Therefore, automobile exhaust causes global warming by emitting gases that are the primary constituents of GHG.
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