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The world's energy consumption has been increasing progressively since the industrial revolution (SEP, 2009). Global population is continuing to dramatically rise and the increase in economic development, particularly in China and India, over recent decades has contributed to increases in energy consumption (Hillstrom & Hillstrom, 2003). Currently, nearly 45 percent of Australia's total energy consumption is accounted for by coal, with oil providing approximately 35 percent, natural gas supplying around 15 percent and 'green' power providing just over 5 percent (Hillstrom & Hillstrom, 2003). Alternative fuels are stated to be a potentially viable alternative to the use of fossil fuels. Fossil fuels contribute to almost eighty percent of the total energy used in the world (Evans, 2007; International Energy Agency (IEA) Bioenergy, 2005). Fossil fuels are non-renewable resources that are limited in their supply and the burning of fossil fuels on a global scale can produce air pollution, such as nitrogen oxides (NOx), release significant amounts of greenhouse gases, such as carbon dioxide (CO2), and contribute to global warming (Evans, 2007; Shahid & Jamal, 2008; Hill, et al., 2006; SEP, 2009). Alternative fuels are considered to have a less adverse effect on the environment, and are stated to be a solution to the problems created by fossil fuels (SEP, 2009). Alternative fuels, such as ethanol, methanol, and biodiesel may prospectively provide an alternative for global fuel requirements. The main difference between fossil derived fuels and alternative fuels is the oxygen content, with alternative fuels having 10-45 wt% oxygen compared to fossil fuels which contain almost none (Gupta & Demirbas, 2010). There are however, a number of drawbacks related to alternative fuels which may inhibit them from completely replacing fossil fuels without technological or genetic advancements (U.S. Congress, Office of Technology Assessment, 1990).
This paper aims to examine the advantages and disadvantages of alternative fuels. The discussion will commence by defining a number of relevant terms. The analysis will then consider ethanol and methanol as alternative fuels, including their production. Subsequently, biodiesels and their production will be examined. Following this, the advantages and disadvantages of alternative fuels will be considered. The use and manufacturing of alternative fuels in Australia will then be assessed. Lastly, the main arguments of this account will be summarised.
Alternative fuels are a sustainable form of energy, are fuels that have not derived from petroleum and can include alcohols, biofuels, hydrogen, natural gas and propane (Saddleback Educational Publishing, 2009). They are commonly solid, liquid or gas biofuels acquired from biomass, vegetable oil, or generated from agricultural food crops (Demirbas, 2008; Hill, et al., 2006). A viable alternative fuel must be economical, supply a net energy gain, be beneficial to the environment, and be able to be produced in considerable volumes with limited detrimental impacts (Hill, et al., 2006). The alternative fuels that are currently prevalent throughout the world are ethanol and biodiesel (Vadas, Barnett & Undersander, 2008; Groom, Gray & Townsend, 2008; Gupta & Demirbas, 2010). Ethanol also referred to as ethyl alcohol, and methanol, methyl alcohol, are colourless liquid alcohols, less dense than water, with the chemical formulas C2H5OH and CH3OH respectivley (Baird & Cann, 2008). Biodiesel is a carbon-neutral fuel that is a mixture of fatty acid methyl esters (Baird & Cann, 2008; Kemp, 2006).
Alcohols: Ethanol and Methanol
Ethanol is one of the most widely utilized liquid biofuels that can be combined with gasoline to create an ethanol blend fuel, or it can be used in pure form (Gupta & Demirbas, 2010; Baird & Cann, 2008). It may be derived by fermenting carbohydrates obtained from natural sugars, starches or cellulosic biomass in plants including sugar cane, corn or straw (Gupta & Demirbas, 2010; Larkin, Ramage & Scurlock, 2004). Generally, this process The USA and Brazil are presently the two major producers of bioethanol (Ragauskas, et al., 2006). In the US, corn is the major primary base for ethanol production while in Brazil, sugar cane is dominant (Brown, 2003). Groom, Gray and Townsend (2008) showed that current fuel yield for corn ethanol was between 1135 - 1900 L/hectare and that the necessary area of land to meet even 50% of US transport fuel needs was over 157% of US cropland.
Biodiesel is obtained from the oil in a variety of seed plants, a large majority being developed from soybean (Larkin, Ramage & Scurlock, 2004; Demirbas, 2008). Biodiesel is currently manufactured around the world in countries such as the USA, Germany and Malaysia (Larkin, Ramage & Scurlock, 2004; Groom, Gray & Townsend, 2008). Globally, approximately 1.5 million tonnes of biodiesel per year is produced (Larkin, Ramage & Scurlock, 2004). In Table 4, it can be seen that current fuel yield for soybean biodiesel was between 225-350 L/hectare and that the necessary area of land to meet even 50% of US transport fuel needs was over 180% of US cropland.
Advantages and Disadvantages of Alternative Fuels
Alternative fuels such as methanol, ethanol and biodiesel have numerous advantages and disadvantages regarding environmental and societal impacts. The replacement of fossil fuels with alternative fuels could result in a decrease of CO2 emissions, decrease air pollution and reduce acid rain (Evans, 2007). Additional benefits include sustainability, fuel security, regional development and a decrease in rural poverty (Gupta & Demirbas, 2010). The land area required to generate sufficient alternative fuel to meet demands however, may compete directly with agriculture requirements, water use, may cause pollution from the use of herbicides and pesticides, and could result in the destruction of natural habitats and a decrease in biodiversity (Evans, 2007; Giampietro & Ulgiati, 2005). In developing countries, the expansion of the alternative fuel industry could increase deforestation, decreasing the removal of CO2 from the atmosphere through photosynthesis (Groom, Gray & Townsend, 2008).
Methanol and Ethanol
There are several advantages concerning the use of methanol and ethanol as alternative fuels. Carbon dioxide in the atmosphere is removed by the crop used for ethanol generation, resulting in the process being carbon neutral (Larkin, Ramage & Scurlock, 2004). Using ethanol over fossil derived fuels can result in a reduction of CO2 up to 75 percent (Howard & Olszack, 2004). Higher densities of ethanol fuel and air can be combusted in an engine compared to petroleum due to ethanol's constricted boiling point range and higher latent heat of vaporization (Brown, 2003; Demirbas, 2008). Additionally, higher energy density can be achieved in the engine due to a lower stoichiometric air to fuel ratio (Brown, 2003; Demirbas, 2008).This may produce enhanced engine efficiency and elevated power outputs in ethanol fuelled vehicles when contrasted to petroleum fuelled vehicles. The use of ethanol as an alternative fuel can result in lower pollution emissions compared to fossil fuels, particularly regarding particulates, alkenes, aromatics and carbon monoxide (Baird & Cann, 2008).
Table 2: Alternative fuel properties compared to fossil derived fuels
(Adapted from: Borman & Ragland, 1998, pp. 37).
There are numerous economic drawbacks to the use of ethanol as a substitute for petroleum-based fuels. Ethanol is still far from being economically competitive when compared to fuels derived from fossil fuels (Larkin, Ramage & Scurlock, 2004; Howard & Olszack, 2004). Expensive direct costs required for the production of ethanol can include fertilisers, pesticides, irrigation, fuels and electricity as well as machine or equipment maintenance (Vadas, Barnett & Undersander, 2008). Fixed costs tend to include land charges, wages for labourers, insurance and depreciation of assets such as equipment and buildings (Vadas, Barnett & Undersander, 2008). The economics of ethanol production are very uncertain; its viability depends on the price of crude oil and the world prices of the raw material, for example, sugar (Larkin, Ramage & Scurlock, 2004). The production and use of ethanol is not economically competitive at present, suggesting that it is not a viable alternative.
There are disadvantages linked to the use of methanol and ethanol as alternative fuels. Ethanol has a lower amount of energy generated per litre combusted than gasoline (Baird & Cann, 2008). The use of pure ethanol and methanol is limited in colder climates by their low vapour pressures (Baird & Cann, 2008). A disadvantage in using methanol is that it is more toxic than gasoline (U.S. Congress, Office of Technology Assessment, 1990). Erosion, nitrogen leaching and denitrification are also other significant problems related to corn produced alcohols (Vadas, Barnett & Undersander, 2008). Environmental degradation is an issue related to ethanol production from crops, which leads to the concern of whether biofuel generation is indeed sustainable for certain crops (Vadas, Barnett & Undersander, 2008). Ethanol yield from various crops can vary significantly, and are usually inefficient (Larkin, Ramage & Scurlock, 2004; Ragauskas, et al., 2006). The production and use of ethanol does not always provide a sufficient net energy gain and there are adverse environmental effects, indicating that it is not a viable alternative.
There are a number of positive factors when considering biodiesel over petroleum-based diesel. Biodiesel production is deemed renewable (Shahid & Jamal, 2008). The fuel itself is generally non toxic and biodegradable (Demirbas, 2008; Shahid & Jamal, 2008). The fuel properties of biodiesel are similar to petroleum-based diesel, revealed in Table 2, allowing it to be used in unmodified indirect injection diesel engines with only minor drawbacks (Brown, 2003; Shahid & Jamal, 2008). Biodiesel has a higher flash point, also seen in Table 2, meaning that it is safer to transport and store than diesel (Brown, 2003; Demirbas, 2008).The exhaust emissions from the fuel contain considerably less nitrogen and sulphur oxides (Shahid & Jamal, 2008). These factors support the idea that biodiesel is an alternative form of fuel; however this does not make it a viable alternative to petroleum-based diesel.
There are many limitations related to the use of biodiesel as a substitute for petroleum-based fuels. Biodiesel can achieve an energy ratio as low as three to one (Larkin, Ramage & Scurlock, 2004). The production of biodiesel from crops, such as soybean, can result in adverse environmental effects. These can include nitrogen and phosphorus leaching that can lead to the loss of biodiversity and the release of nitrous oxide, a greenhouse gas (Hill, et al., 2006). In some countries, such as Indonesia, Malaysia and Thailand, vast expanses of forests are being cleared to produce oil-palm plantations for biodiesel (Groom, Gray & Townsend, 2008). Biodiesel, compared to fossil fuel derived diesel, tends to produce lower power and torque as well as higher fuel consumption (Demirbas, 2008). Biodiesels are not cost competitive when compared to petroleum-based fuels (Hill, et al., 2006). The cost of biofuel tends to vary on a number of factors including the price of crude petroleum, the variability in the crop and the cost of the feedstock used (Demirbas, 2008). The production and use of biodiesel is associated with some adverse environmental effects and it is not economically competitive at present, indicating that it is not a viable alternative.
Alternatives Fuels - Use and Manufacturing in Australia
-sugar cane??? (ethanol)
Alternative fuels such as methanol, ethanol and biodiesel have both advantages and disadvantages regarding impacts on the environment and society. At present, commercial biofuel production is a controversial issue that is still relatively new. It is conceivable that biofuels will become a selective alternative to fossil fuels as a source for transportation fuels but not a complete substitute. As oil prices become increasingly more expensive, biofuels do become more economically viable. Biofuels are effective on a small scale basis, but not on a large scale. There are numerous problems currently associated with the manufacturing of biofuels such as the vast amount of land, labour and water required. The development of better second and third generation biofuels would be more effective as they potentially use less land and have a greater chance of being a viable alternative for fossil fuels. Great improvements in current technology, genetic advancements for biomass crops and reduced environmental and societal effects could see biofuels become a selective substitute but not a replacement for global energy demands.