Ever since it became fashionable to care about the planet, we have been focusing on reducing emissions, when we should be focusing on eliminating them. Even a small amount of greenhouse gases released by a very large number of people becomes a large amount of greenhouse gases. If we are going to “save” the planet we are going to have to return to a preindustrial level of greenhouse emissions. This means that technologies and measures which merely reduce our emissions will merely delay the destruction of our environment. While “solutions” such as alternative fuels may seem like a good idea because they require only minor modifications to existing technologies, they don’t bring us any closer to a real solution. That is because any meaningful solution would require a re-engineering of current technologies to eliminate the use of combusted fuels, or invention of new ones which don’t use them. The same thing applies to systems of filtration, recapturing gases, and cleaner burning. They all reduce emissions to various degrees, but none of them will eliminate them. Although reducing emissions may seem like a good idea, we should be trying to eliminate them through the use of non-combustion technologies because we need to eliminate emissions to stop global warming, even small emissions multiplied by billions of people is results in a substantial effect, and reducing emissions doesn’t bring us any closer to technologies which eliminate emissions.
According to Thomas (2009), “The transportation sector accounts for 28% of all US greenhouse gas emissions, 34% of all carbon dioxide emissions, 36%–78% of the main ingredients of urban air pollution, and 68% of all oil consumption”. Attempts to reduce greenhouse gas emissions from transportation in recent years have focused primarily on increasing fuel efficiency, emissions control technologies, and alternative fuels. Increasing the fuel efficiency of vehicles has a relatively small effect on total greenhouse gas emissions. According to Schewel (2008) a 10% decrease in automobile weight can lead to a 5% to 7% increase in fuel efficiency (p. 2). However, there is a correlation between cost of fuel and annual distances driven. Schipper (2011) shows that a 10% increase in fuel prices leads to a 5% to 7% increase in fuel economy and annual distances driven increase as fuel prices decline. Schipper (2011) also states that driving distances increase as the GDP increases. From this one can infer that vehicle use will increase as improved fuel efficiency results in a lower cost of operation. This would result in a mitigating effect on any potential fuel savings. Simply improving the fuel efficiency of vehicles therefore will likely have a minor effect. It is also worth noting that the EPA (2006) reports that most technological improvements in the U.S. have been used to improve power and weight of vehicles, with only limited improvements to the fuel efficiency (p. 17). It is interesting to note that in a model produced by Thomas (2009), hydrogen-combustion hybrid electric vehicles, fuel cell electric vehicles, and battery electric vehicles all offered the greatest reductions to greenhouse gas emissions over a 100 year period. Thomas (2009) showed that scenarios involving these three types could potentially reduce emissions to an estimated .15 billion metric tons of carbon dioxide-equivalent emissions per year in the U.S. by 2100, compared to a best case scenario of .75 billion metric tons of carbon dioxide equivalent emissions per year for scenarios involving improving existing fossil fuel and biofuel hybrids. Note that this model assumed that some portion of electrical generation would still use fossil fuels (Thomas, 2009). Hydrogen-electric hybrids, hydrogen fuel cell-electric hybrids, and full electric vehicles produce no greenhouse gases during operation. The model was based on a gradual phasing in of various transportation technologies in different combinations (Thomas, 2009). Thomas further (2009) states that even if hydrogen is initially made from natural gas, it would result in an immediate 50% decrease in greenhouse gases emitted for fuel cell electric vehicles compared to burning gasoline in a regular car of similar size. Thomas (2009) further states, however, that further reductions would be required to reduce emissions to even 20% of 1990 levels by 2100.
Greenhouse gases in the industrial sector are controlled using carbon capture and storage. Olajire (2010) discussed the three primary carbon capture techniques: pre-combustion decarbonization, post-combustion, and oxy-fuel combustion. Post-combustion uses chemical solvents, membranes, or low temperature distillation to separate carbon dioxide and other pollutants from the flue gas after combustion of the fuel. Post-combustion carbon capture typically requires large amounts of energy to regeneration the solvents once they have been used. Pre-combustion uses air and steam to produce hydrogen and carbon dioxide from carbon-based fuels. The carbon dioxide is then separated from the hydrogen and captured, and the hydrogen is used for fuel. Pre-combustion carbon capture has lower energy requirements than post-combustion, does not require the use of chemical solvents, and is more efficient at capturing carbon dioxide. Oxyfuel combustion is a post-combustion technique which uses pure oxygen in the combustion process. According to Olajire (2010) this creates a high concentration of carbon dioxide in the flue gas, which simplifies the separation and capture of the carbon dioxide and eliminates NOx emissions. Oxyfuel combustion does not require the use of chemical solvents, but has a large energy cost and oxygen is difficult to aquire. The carbon dioxide separation techniques used to collect carbon dioxide from the gas stream include absorption, adsorption, membranes, and cryogenics. In chemical absorption a solvent is used to absorb carbon dioxidefrom the gas stream, and then heat is applied to separate the carbon dioxidefrom the other gases and create a pure carbon dioxidestream. According to Olajire (2010), Amine absorbtion is capable of filtering carbon dioxidewith 98% efficiency. Adsorption passes a gas through a solid material, and the desired pollutants attach themselves to its surface. Cryogenic methods involve cooling the carbon dioxide until it liquifies, separating it from the gas stream. Membrane methods rely on semi-permeable membranes to filter out the desired gases. Note that Olajire (2010) indicates that because of the relatively small quantities of non-carbon dioxide greenhouse gases, emission reduction efforts are primarily concerned with the capture of carbon dioxide.
Because of the widespread infrastructure for combustion produced power, alternative fuel sources are a popular target for reducing green house gas emissions. The types of alternative fuels include biomass, organic oils, biofuels, and hydrogen. Of these, hydrogen is the cleanest. Hydrogen fuel cells are a method of producing power without combustion. They operate by combining oxygen and hydrogen to produce electricity and water. Busby and Altork (2010) claim that more than 99% of the by product from hydrogen fuel cells is heat and clean water, and no greenhouse gases are produced (p. 24). This provides the potential to either generate more power from the steam, or to use it to provide a clean water source. Busby and Altork (2010) also maintain that hydrogen can be produced almost anywhere on the planet with few restrictions (p. 24). Yet, despite the obvious benefits, fuel cells have been slow to evolve. According to Busby and Altork (2010) the first hydrogen fuel cell was created in 1838, but the first modern fuel cell was not created until 1989, and they are only now becoming viable technologies (pp. 22 – 23). Presently there is little infrastructure in place for hydrogen production or use as a fuel source. Busby and Altork (2010) believe that it will take about 40 years to build a hydrogen fuel infrastructure (p. 26). Adapting existing technologies is therefore generally preferred. Biomass, biofuels, and organic oils are ideal for this purpose. Biomass is raw plant matter including wood. Biomass can be converted to energy either by burning, or by a process called gasification. It can also be converted to other fuels such as biomass oil or methanol (Yoshida et al., 2003, p. 258). Biomass oils can be used for heating, and methanol can be used to produce heat, electricity or hydrogen (Yoshida et al., 2003, p. 258). Organic oils are oils made from plants such as soybean or peanut oil. They are popular for diesel modifications since individuals can collect leftover frying oil from restaurants. Biofuels are gasoline and diesel fuels derived from plant matter. The plant matter has to undergo a costly and energy intensive process to be turned into biofuel, but it can be used in gasoline or diesel engines. Thomas (2009) states that max biofuel production in the U.S. could be anywhere from 45 to 140 billion gallons per year. Thomas (2009) also states that water resources may become an issue with increased biofuel production. The emissions savings from the use of plant derived fuels is questionable. The argument is that the emissions released from combusting these fuels came from the atmosphere and will eventually be reabsorbed by the next generation of plants, creating a closed loop. It is important to keep in mind that this process only works if we are able to grow as much fuel as we use in a given year. In reality, it takes far longer to grow a tree than to burn one, resulting in a short term inundation of the atmosphere with carbon dioxide and a long term recovery period.
In order to better understand the effect of global emissions, it is necessary to understand the biocapacity of the Earth. Biocapacity is the volume of pollutants which a system is able to process. The major contributers to the greenhouse effect are carbon dioxide, methane, nitrous oxide, ozone, and water vapor . Due to the relative lack of information on nitrous oxide and ozone sources and sinks, they will not be discussed here. Also, the amount of water vapor in the air is not directly affected by human activity and will not be covered here. It will be discussed with feedback loops, however. According to Jansson, Wullschleger, Kalluri, and Tuskan (2010), a total of 3 gigatons of carbon is sequestered annually by terrestrial systems (p. 685). Jansson et al. (2010) also estimated that 2 gigatons is sequestered annually by oceanic systems (p. 685). This provides a total of almost 16.5 gigatons of carbon dioxide sequestered annually world wide. Carbon dioxide in the atmosphere can remain there for hundreds of years. Living plants and other organisms provide only short term sequestration of carbon dioxide. Once the plant or organism dies, the carbon dioxide will be released back into the atmosphere. Thus, living organisms mostly represent a static storage of carbon. If the number of plants increases, then more carbon will come out of the air, and if the number decrease, more carbon will make it into the air. Because of this, they can change the short term levels of carbon dioxide, but will not greatly affect the long term levels. The soil, on the other hand, is capable of long term storage of carbon dioxide. Jansson et al. (2010) state that inorganic carbon stored in the soil may remain there for millennia (p. 687). This capacity for soil to store carbon for long periods represents an effective way to reduce total atmospheric carbon dioxide levels.Plants transfer some of the carbon dioxide in the air to the soil through their roots. Because of this, and their potential to moderate short term carbon dioxide levels, plants are instrumental in managing carbon dioxide in the atmosphere. According to Jansson et al. (2010) estimates for the total capacity for organic carbon sequestration in soil ranges from 44 to 537 gigatons of carbon (p. 687). Jansson et al. (2010) believe that 80 to 130 gigatons of organic carbon may be sequestered in the soil over a 100 year period through improved land management practices (p. 687). Methane exists in much smaller quantities than carbon dioxide, but it is a powerful greenhouse gas. According to an article in the NY times (2009) methane is 33 times more effective at trapping greenhouse gases than carbon dioxide (Henderson, np). Because of this, methane is also an important factor in global warming. According to Reay (2003), about 540 million tons per year is broken down by methane oxidation in the atmosphere (p. 16). Reay (2003) also states that about 30 million tons are removed by bacteria in the soil , and chemical reactions with chlorine in the atmosphere and the oceans has a relatively minor effect (p. 16). The hydroxyl radical (OH) is the primary contributor to the breakdown of methane and other pollutants in the atmosphere, such as carbon monoxide (Reay, 2003, p. 16). An increase in any of these pollutants would therefore increase the effects from the others by reducing the OH levels, and thus require an extended time to remove the pollutants from the atmosphere. A longer life span in the atmosphere means more time for pollutants to accumulate. Additionally, hydrogen oxides and ozone are usually consumed in the reactions which break down methane (Reay, 2003, p. 16).
Schmidt (2010) points out that virtually all scientists agree that there has been a warming trend since the beginning of the industrial era (p. 538). It would seem, then that human activities since the beginning of the industrial era are responsible for global warming. One of the characteristics of the industrial era was the widespread use of fossil fuels as a source of energy. Fossil fuels release large amounts of greenhouse gases when burned, including carbon dioxide, methane, and nitrous oxide. Furthermore, the warming trend has been accelerating in recent years (needs support). Klimenko, Tereshin, and Mikushina (2009) show an increasing consumption of fossil fuels since the middle of the 20th century (p. 2471). There has also been an increase in anthropogenic emissions of carbon dioxide. According to Princiotta (2009) approximately 25 billion tons of carbon dioxide were emitted in 2004, up from 18 billion tons in 1980 (p. 1195). Furthermore, the growth rate of emissions is increasing. Princiotta (2009) shows that there has been an average annual growth rate of 1.4% since 1990, but 3.5% since 2000 (pp. 1194-1195). Princiotta (2009) also states that emissions are projected to reach almost 60 billion tons per year by 2050 (p. 1197). Carbon dioxide is the most prominent greenhouse gas, and has the largest effect on global warming. Carbon dioxide per unit volume has the weakest effect on global warming of all the identified greenhouse gases, with a greenhouse warming potential (GWP) of 1. However, due to the much larger quantities of carbon dioxide in our atmosphere, it is the most important factor of global warming today. Most scientist agree that just under 50% percent of global warming is the result of Carbon dioxide in our atmosphere (Schmidt, 2010, p. 538). Carbon is found in almost every living creature and plant, as well as their remains. The primary method of removing carbon dioxide from the atmosphere is through photosequestration by plants (Jansson, 2010, p. 685). As a result, plants and organisms contain a sizable portion of global carbon reserves. According to Jansson et al. (2010) they contain around 670 gigatons of carbon, compared to 760 gigatons of carbon existing in the air (p. 685). Because of this, there are a great many sources of carbon dioxide. When a plant or animal dies, its remains release carbon dioxide as they decay. Similarly, when they are burned they release carbon dioxide among other pollutants. As a plant grows, it takes in carbon from the atmosphere in the form of carbon dioxide. Much of this is returned to the atmosphere, but the remaining carbon is stored in the plant material. According to Jansson et al. (2010), of the 123 gigatons of carbon which are sequestered annually, 113 are returned to the atmosphere through plant and microbial respiration (p. 685). During the combustion process, all of the carbon stored in the plant over its lifetime is released. Therefore, forest fires can represent a significant factor in carbon dioxide emissions because the carbon content is released rapidly, and the regrowth of new trees to reclaim it takes many years. Jansson et al. (2010) estimate that 90% of the world’s terrestrial carbon is stored in forest ecosystems (p. 687). Human use of wood for fuel also represents a significant contribution of carbon dioxide. Because of the slow growth rate of trees, it would take many years to re-sequester the carbon emitted. Meanwhile, carbon dioxide would be building up in the atmosphere. Deforestation can also be a significant source of carbon dioxide emissions through both the decay of biomass, and the loss of trees which act as a carbon sink. According to a study by Powlson (2011), the estimated carbon dioxide emissions from deforestation are 25% of that from fossil fuel use. Human and animal respiration also contributes carbon dioxide. Ocean-atmosphere exchange may contribute carbon dioxide (need information). Volcanic emissions represent a small source of carbon dioxide (need information). Fossil fuel use is by far the worst contributor to carbon dioxide emissions. Since fossil fuels represent carbon which has been removed from the natural cycle, any fossil fuels we burn represent a net increase in the amount of carbon dioxide in our atmosphere. Not only does it represent an addition of carbon dioxide beyond the natural balance, but it is responsible for the greatest share of carbon dioxide emissions globally. According to Olajire (2010), fossil fuel power plants produce more than a third of global carbon dioxide emissions. In the same article, Olajire (2010) states that a 1000MW power plant produces between 6 and 8 million tons of carbon dioxide every year when powered with coal, between 4 and 6 million tons when powered with oil, and between 3 and 4 million tons when powered with natural gas. A report published be the IEA (2009) shows that the transportation sector accounts for 23% global carbon dioxide emissions from energy (p. 29). The same report by the IEA (2009) claims that 95% of transportation energy comes from fossil fuels (p. 48). There are additional emissions from fossil fuel uses not related to the production of energy. This excess carbon will eventually be returned to the soil, but it is a very slow process. Archer et al (2009) believe that effects from carbon dioxide in our atmosphere could persist for tens of thousands of years (p. 131). Carbon dioxide may also be release by chemical reactions during industrial process not related to the combustion of fossil fuels. Describe the amount of carbon dioxide released by industrial processes.
After carbon dioxide, methane is the second most important contributer to global warming. Conversion of forests to agricultural land increases the levels of methane in the air by reducing the ability of the soil to act as a methane sink. This is because conversion to agricultural land increases the nitrogen levels in the soil, and high nitrogen levels inhibit methane oxidation. Methane comes from livestock and other animals. One cow can produce a volume of methane which would require 2.5 acres of methanotrophic bacteria to remove (needs support). Rice produces a significant amount of methane (more info). Waste water treatment. Landfills. Combustion of plant matter. Natural gas distribution. Wetlands. Methanogens. Plants? Permafrost (more info). Methane Clathrates may be a source of global warming from a feedback loop. If the temperature of water rises enough, then the methane trapped in the sediments would be released into the atmosphere (more info)
Over the history of the planet, levels of carbon dioxide in the atmosphere have fluctuated between x and y (need information). The low end of the scale marks glacial periods, and the upper end marks interglacial periods (needs support). This shows that relatively small changes in the levels of atmospheric carbon dioxide can have a large effect. Our current levels of atmospheric carbon dioxide are x (needs info). At the beginning of the industrial revolution it was x (need info). Or almost x times the largest concentration at any preindustrial point in measured history. Also, there has been a trend of increasing emissions which continues today (more info).
Over the history of the planet, levels of atmospheric methane have also been relatively steady. An article by Loulergue et al. (2008) states that atmospheric methane levels have varied between 350 and 800 parts per billion over the last 650,000 years. (p. 383). As with carbon dioxide, the lowest levels coincided with glacial periods in our history, and the highest levels coincided with interglacial periods (Loulergue, 2008, p. 383). There seems to be an obvious correlation between atmospheric carbon dioxide and methane levels and global temperature. According to Loulergue et al. (2008) Present day levels of atmospheric methane have been measured at 1770 parts per billion, which is over twice the highest preindustrial concentration (p. 383). This has been steadily rising since the beginning of the industrial era, when it was only x (need info). Today the annual emissions of methane into the atmosphere are x (need info).
One of the most dangerous and insidious aspects of global warming is the feedback loop. It is widely considered that human activity is solely responsible for global warming. To a degree, this is true. However, to some degree we are merely instigators. This is because global temperature is regulated by extremely complicated interactions in the natural world. When increased temperatures change the balance in some ecological system, causing it to either release more greenhouse gases or to no longer remove them, then global warming will increase as a result. This is what is known as a feedback loop. As these even higher temperatures further upset ecological balances, it will eventually result in a runaway global warming process wherein humans no longer have control.
One of these feedback loops results from massive stores of methane frozen in the arctic permafrost (needs support). As temperatures rise and the permafrost begins to melt, the methane is released into the atmosphere. Further warming created by the extra methane causes further melting of the permafrost and so forth. There is estimated to be X amount of methane stored in the arctic permafrost (more info). The impact on global warming if all this methane were to be released would be (more info).
Another feedback loop results from deforestation. As photo sequestration by trees is the primary means of removing carbon dioxide from the atmosphere, the loss of forest acreage results in decreased removal of carbon dioxide. Humans account for one source of deforestation, but global warming can cause it as well (needs support). The current rate of temperature change can alter the climates around the world artificially fast. The native species may be unable to adapt so quickly and will die out, resulting in a loss of forest. Warmer temperatures may also result in reduced soil moisture leading to an increase in forest fires. The reduced forest acreage will then contribute to increased warming.
Water vapor is one of the most powerful greenhouse gases. With a GWP of x, it is x times more effective than carbon dioxide in trapping the sun’s heat (need info). Directly, human activities cannot put more water vapor into the air, so releasing water vapor by any means would have no effect on global warming. This is because the air can only hold a specific amount of water vapor. The volume of water vapor that can be stored in the air is directly related to the air temperature, however. As the temperatures increase, the air will be able to hold more water vapor. The high GWP of water vapor makes it one of the more dangerous feedback loops. (support this paragraph)
Receding ice cover represents another feedback loop. As the ice on the surface melts, less sunlight is reflected back into space. More of the surface is therefore warmed by the sun resulting in a higher temperature which results in further recession of ice.
Ocean absorption of carbon dioxide decreases as warmer water temperatures halt the exchange of carbon dioxide between surface waters and deeper waters.
Methane clathrates in the ocean sediment layer are a potential feedback. These are solid methane compounds which are only stable under high pressure and low temperatures. As higher temperatures penetrate the deeper ocean waters, the methane in these compounds may be released.
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