Abstract - With constantly increasing gas prices and the inevitable depletion of subterranean oil fields, it is crucial the world looks to a new source of fuel in order to maintain today’s transportation demands. Our paper will explore transesterification, a rapidly growing method of producing fuel where diesel is generated from vegetable oil. Through extensive research, we will depict how this process of using vegetable oil, mainly from soybeans, in combination with an alcohol and a catalyst produces methyl esters, commonly known as biodiesel. Our research will include a comprehensive study of the chemical mechanisms involved with the transesterification process. Innovative professional journals, such as Chemical & Engineering News, along with recent experimental data from biodiesel plants will be consulted throughout our analysis. In addition to the biodiesel, transesterification also produces a very small percentage (approximately 1%) of glycerin and other residue. These byproducts are then utilized in the pharmaceutical and cosmetic industries, ensuring that nothing is wasted. The actual process of biodiesel production is simple and clean. The reaction is completed at low temperature and pressure with no intermediate compounds, fast reaction times and a high conversion rate of methyl esters (nearly 99%). Producing fuel from vegetable oils provides an infinite resource, which is economically and environmentally beneficial. Unlike the waning resource of underground oil, soybeans, the primary ingredient in biodiesel, prove to be an unbounded natural resource. Also, soybeans are readily grown in many different climates, making the market more available, thus decreasing the cost of production. This decrease in cost will positively influence the consumer by lowering the cost per gallon of gasoline. Along with these economic benefits, biodiesel is much more environmentally friendly than traditional fuels. Biodiesel reduces harmful emissions, which are damaging to the ozone and to the health of those exposed to them. In our paper, we will prove the production of biodiesel will provide the economy with a stable fuel market, which is friendly to the environment and to the consumer. Biodiesel plants are becoming more numerous across the United States, which provides a firm foundation for this growing industry.

Index Terms — biodiesel, transesterification, methyl esters, soy oil, fuel, glycerin.

BIODIESEL TO THE RESCUE

“The use of vegetable oils for engine fuels may seem insignificant today, but such oils may become, in the course of time, as important as petroleum and the coal-tar products of the present time” – Rudolf Diesel, 1912

In the early 1900s, diesel fuel was a new and innovative idea with seemingly limitless bounds. Natural resources, such as oil, were abundant and readily available for man to refine and use for fuel. However, Rudolf Diesel, the man responsible for introducing the world to diesel, predicted a certain, unthinkable fate: the depletion of natural resources. Even as early as 1912, in the midst of the diesel craze, Diesel recognized the potential of vegetable oils as engine fuel. Now, in the year 2006, Diesel’s vegetable oil prediction is particularly relevant as the complete depletion of subterranean oil is in sight.

Today, oil is our primary energy source, accounting for nearly 40% of all energy use worldwide [1]. Unfortunately, it is of a finite amount, meaning it will eventually run out. Although nobody is certain as to exactly how much oil is available, predictions have been made that estimate the world will reach its peak year around 2010. The peak year relates to the highest part of the bell curve that describes oil production over time.

Graph 1

The bell curve depicts how oil is increasingly plentiful on the up-slope and decreasingly plentiful on the down-slope. The years following the peak year will consequently have a continually decreasing oil supply. From this estimated peak year, scientists have been able to predict roughly how much oil is left for us to ‘discover’ [2].

With this daunting reality being presented to us, it is easy to understand the urgency of alternative fuel research. Alternative fuels will inevitably be needed as primary fuel sources to help sustain the economy. Developing these alternative fuels is not as easily said as done. There are countless factors involved in considering an alternative fuel. These concerns include the resources used, production process, environmental and public welfare hazards, economics and overall reliability. Transesterification, an innovative method of turning vegetable oils into fuel is proving to be one of the most efficient alternative fuel sources yet. The transesterification process is a clear solution to the problem of oil depletion, which ethically considers the environment, public welfare and economic factors involved.

THE TRANSESTERIFICATION PROCESS

The transesterification process is the primary focus of biodiesel production. The method in which this process is carried out determines many aspects of production, including how many gallons of biodiesel are produced per day, the chemical properties of the newly constructed fuel, and the amount and composition of the byproducts. For these reasons, plant engineers pay close attention to the details of the transesterification process to ensure they are producing the exact substance they set out to make.

Resources

Manufacturing biodiesel requires few but important resources, which give the fuel many unique properties. These main resources include some type of oil or fat, an alcohol, and a catalyst. All three of these reactants play distinct roles in the formation of biodiesel. The oil provides a template for the reaction, which is disassociated by the alcohol to produce the biodiesel and other byproducts. The catalyst is present to ensure a fast reaction time in order for the process to be feasible.

Therefore, biodiesel is actually composed of oil which has been chemically restructured in order to produce an efficient energy source. This oil can come from a number of different sources, depicted in Graph 2. As the graphical data shows, soybeans are the main resource for the fabrication of biodiesel. Many companies choose soybeans as the primary input for the transesterification process since they are the most abundant resource of vegetable oil and have a low average cost per year of about $1.80 per gallon of oil [3]. Soybeans are not actually put in the chemical process of making biodiesel, but the oil from the soybeans is entered into solution with an alcohol in order to begin the transesterification reaction. To obtain the soy oil, manufacturers must filter the oil out of the bean. This is a straightforward process, which involves neither expensive machinery nor groundbreaking technology. In this process, the soybeans are merely smashed against a permeable membrane, such as a metal screen with small holes, to drain them of their oil. This processed oil can then be implemented into the transesterification reaction.

Graph 2 [4]

Yet, soy oil alone cannot produce biodiesel. In addition to the oil, an alcohol is needed to begin the process. The main alcohol used in industry is methanol since it incurs only a $1.00 cost per gallon, which is actually only $.10 per gallon of biodiesel produced because the reaction requires only 10% alcohol by weight [5]. Also, methanol is readily obtainable from wood, coal, or natural gas and easily stored with low safety issues for industrial use.

The last piece of the biodiesel puzzle is a kinetic factor in the reaction, meaning it does not affect any part of the reaction other than the rate at which it is completed. The most common catalyst utilized in the biodiesel industry is sodium hydroxide (NaOH), also called lye. Another common catalyst is potassium hydroxide (KOH), but it is less commonly used because a greater amount of potassium hydroxide is needed to produce the same affect as sodium hydroxide.

The resources, oil, alcohol and the basic catalyst, are all three brought together in the transesterification process in order to fabricate an efficient fuel for everyday use.

Chemical Process

The transesterification process is the chemical exchange of the alkoxy group of one compound by another alcohol [6]. In biodiesel production, the transesterification process is the process in which free fatty acids are split by the alcohol and catalyst mixture to produce methyl esters, which are called biodiesel [6].

Free fatty acids are what all fats and oils are composed of, and are made mainly from four chains of acids called palmiti, stearic, oleic, and linoleic [7]. These acids appear, as depicted in Figure A, in the form of an upper case letter E, called a triglyceride, which is held together by a carbon backbone, called glycerol. In the transesterification reaction for the production of biodiesel, soy oil is the source of these triglyceride molecules. These free fatty acid molecules are added to a solution of methanol (CH3OH) and sodium hydroxide (NaOH). Once the fatty acids are exposed to the alcohol and catalyst solution they are split apart at the backbone of the triglyceride to form glycerin and methyl esters [5].

Figure A

One of the major benefits of the transesterification process is that it can be performed at any scale and at ordinary conditions. Production at any scale means biodiesel can be made in something as small as a “kitchen blender, which makes a few liters on up to a large industrial facility capable of producing millions of gallons per year” [4]. Even more important is the fact that biodiesel can be produced at normal conditions, which are room temperature and normal atmospheric pressure. This benefits the industry greatly because there is much lower risk of combustion when working at lower temperatures and pressures. Also, no high tech machinery is needed to keep the process at a high pressure or temperature [8].

Not only does this process occur under normal conditions, but also it is a spontaneous reaction, meaning once the reactants are in solution nothing else needs to be done except to wait for the reaction to move to completion. Completion of the transesterification reaction, in biodiesel production, occurs after a very short period, sometimes only one hour. During this quick reaction, many important changes are happening to the reactants. This systematic industrial process is outlined in Figure B. Exactly what happens in the transesterification process can be summarized in a few simple steps.

The first of these steps is the incorporation of the soy oil feedstock into a reactor where the methanol alcohol has been pumped. The reaction requires that 10% by weight alcohol be used in ratio to the oil. Therefore, if 100 pounds of soy oil are used, then ten pounds of methanol will be utilized.

Figure B

The reactants are then heated until they vaporize. Yet, some of the methanol does not go into reaction so it must be removed and condensed back into a liquid to be recycled and reused in the next reaction. The heating process is traditionally done by passing heated water through pipes, which wrap around the reactor, but a more efficient source of heat can be produced by the unused methanol. The excess methanol that must be condensed and recycled is already at a high temperature. One way to conserve more energy in the system is to use this methanol to heat the reactor contents. As the methanol gives off energy in the form of heat, it cools and condenses itself; hence, two tasks are accomplished at once [3]. One priority when working with an alcohol at high heat is to ensure no oxygen leaks into the system because of the risk of combustion. Yet, more advanced ways of heating the alcohol-oil mixture are now being implemented in the industry, such as using microwaves to speed up the process without heating to as high of a temperature. Some companies decide not to heat the process at all, which is also a perfectly fine way to create biodiesel.

Once the reactants are vaporized, they are passed into a large holding reactor. In this tank the transesterification of the free fatty acids occurs, also it is where the basic (having a high pH) catalyst is applied. While all three of these resources are in the reactor, the splitting of the free fatty acids begins to take place at a rapid rate. For every one mole of triglyceride split, three moles of alcohol are consumed, as the three chains of fatty acids on the triglyceride are replaced by the hydroxide ion of the alcohol. Therefore, as in Figure C, three hydroxide ions are needed to split one triglyceride. From the breaking of this triglyceride, methyl esters are formed. Esters are a type of compound consisting of carbon and oxygen which are grouped in a certain way, shown in Figure C, and represented by COO. A methyl ester therefore is part of the chain of the free fatty acid chemically bonded to the CH3 of the methanol (CH3OH) [5].

Figure C

1 FFA + 3 methanol --> 1 methyl esters + 1 glycerin

After about one hour of processing in the large reactor, the products are sent to a centrifuge. A centrifuge is a piece of equipment that is able to separate substances according to their densities. The centrifuge spins at very high speeds in a circle forcing the less dense molecules, the methyl esters, toward the outer edges of the machine where they can then be drawn off and transported to a holding tank. The more dense molecules, glycerin compounds, stay near the inside of the machine and can be drained and pumped to a separate holding tank. The transesterification process in biodiesel production yields a conversion of approximately 98%, meaning for every 100 pounds of oil reacted, about ten pounds of glycerin and 100 pounds of biodiesel are produced [5].

Overall, this process is a more efficient way to make a feasible alternative fuel. The process takes place at low temperature and pressure, reducing safety and health hazards. “It yields a high conversion with minimal reaction time” allowing a larger amount of fuel to be produced faster [5]. Transesterification directly converts soy oil to biodiesel with no intermediate compounds or side reactions and no high maintenance machinery or exotic materials.

Products

Methyl esters are the main products of the transesterification process. These esters can be utilized by many different industries. Most importantly, they are produced in order to provide an alternate fuel source for automotive transportation [8]. Yet, they are also applied in other industries, such as home heating, and lubricants [4].

In the automotive industry, biodiesel can be used in different percentages of the total fuel. This means methyl esters have the ability to be mixed with normal diesel fuel to produce various blends of fuel. The most common biodiesel fuel is a blend of diesel fuel and biodiesel in the ratio eighty to twenty respectively. This fuel is called B20, meaning it is 20% biodiesel. Other blends range from B40 to B100. Although pure biodiesel can be used as a fuel, B20 is more commonly put to use in automobile engines. B20 fuel has enough biodiesel in it to reduce toxic emissions and instill a longer engine life. This longer engine life is due to the higher lubricity of the biodiesel [9]. Biodiesel acts as a lubricating agent in the engine and keeps the engine moving smoothly with less friction and corrosion than traditional diesel fuel.

Blends of biodiesel in the range of B4 to about B6 are used not for automotive fuel, but as machine lubricant due to the high lubricity of the methyl esters [4]. Biodiesel is also used in the home heating industry. Biodiesel mixes with heating oil the same way it does with automotive fuel to produce different blends of fuels. This is method, already being implemented in many European countries, is beginning to be introduced to the United States.

The methyl ester product of transesterification is the motive for the entire process. Yet, the byproduct glycerin is inevitably created with the methyl esters of biodiesel. Soap is also often produced as a byproduct of the transesterification process. Both of these byproducts have important roles in alternative industries, ensuring that neither goes to waste. Glycerin is not just some useless byproduct to be tossed away or dumped into a river somewhere. Glycerin is an important additive in the soap and cosmetic industries. The chemical properties of glycerin allow it to be used as a moisturizing agent, which is used by many cosmetic companies when fabricating lotions or makeup. Along with the cosmetic value, there is a demand for glycerin in every grocery store. Glycerin is applied to fruits and vegetables in grocery stores in order to keep them from biodegrading. The coat of glycerin on the surface keeps the O2 in the air from forming an electrode with the surface of the fruit, such as when O2 and water vapor cause the rusting of iron. There are many other important uses for glycerin, but mainly this nontoxic byproduct is sold to the cosmetic industry for use in lotions [4].

On the whole, the products of the transesterification process are widely used by a plethora of industries. Each product has many different uses, all of which are profitable goods for the biodiesel producing company. Therefore, no product of the transesterification reaction is wasted.

ETHICS OF BIODIESEL

Considering the ethics involved in biodiesel is extremely important in understanding its value to society. When compared to traditional petroleum fuel used today, biodiesel is found to be safer for the environment and public, more economically beneficial and provides direct benefits to the consumer; all of which make it an ethical and desirable alternative.

Environmentally Friendly

Contemporary science and environmental studies indicate the fragile status of the ozone layer and the negative implications of its damage. Fuel emissions are notorious offenders of the ozone layer and lead to acid rain and air pollution. Harmful emissions such as carbon dioxide (CO2), sulphur dioxide (SO2), particulates, hydrocarbons (HC) and carbon monoxide (CO) are caused by the incomplete combustions that take place when burning fuel. Incomplete combustions form solid fractions of particulate matter (i.e. solid carbon and sulfur fractions).
Biodiesel however, has a decreased amount of carbon and no sulfur, therefore preventing these solid fractions from forming. The absence of these fractions increases the amount of oxygen present, generating a more complete combustion [10]. This more complete combustion reduces the harmful emissions, making biodiesel nontoxic and therefore harmless to the public’s health. Graph 3 shows the percentage of emission reduction of B100 biodiesel compared to petroleum-based diesel.

Graph 3 [8]

As shown, the transesterification process reduces SO2, soot, CO, CO2, HC, particulates and aroma emissions by up to 100%, 60%, 60%, 50%, 50%, 75% and 18% respectively [10]. Another environmentally friendly aspect of biodiesel is in its organic nature. Unlike petroleum-based diesel, the organic properties of biodiesel make it more manageable to deal with if spilled. Biodiesel degrades four times as fast as petroleum diesel, preventing it from causing much of the long-term damage oil spills can cause to the environment.

Public Safety

In addition to being safer for the environment, the organic components of biodiesel further increase public welfare by increasing safety in terms of transportation, storage and handling. Transporting fuel is a dangerous, but necessary task. Whether by road or sea, moving large quantities of combustible material has the potential of causing an explosion, especially if an accident occurs. Compared to petroleum-based diesel, biodiesel is significantly less dangerous to transport. The main reason for this is due to its increased flash point. The flash point of fuel is simply “the temperature at which the fuel becomes a mixture that will ignite when exposed to a spark or flame” [10]. The higher flash point of approximately 150º C (compared to around 70º C for petroleum-based diesel) makes biodiesel less hazardous than any other diesel fuel. Even when exposed to a lit match, biodiesel will not ignite, meaning that accidents during transportation or at gas stations will no longer be a safety concern [10].

The overall safety of biodiesel is unlike anything the fuel industry has created. “100% biodiesel is as biodegradable as sugar and up to ten times less toxic than table salt” [4]. When in contact with skin, studies show that biodiesel is “less irritating than a 4% water and soap solution” [4]. The ability to compare the abrasiveness of fuel to that of sugar, table salt and soap illustrates its truly benign nature, proving that making the switch to biodiesel will increase safety and therefore protect the welfare of the public.

Economically Beneficial

The economics of fuel is a large topic of concern today. Fuel prices in the United States are the highest they have ever been, with an average cost of $2.25 and $2.47 for gasoline and diesel respectively [11]. When compared to petroleum-based diesel, biodiesel is cheaper to produce (after government incentives), lowers pump prices and gives the United States a much-needed sense of economic independence.

Table 1 shows the current Pennsylvania production costs for biodiesel. The table breaks down the production costs into three main expenses: soy oil, methanol and production. It also includes the two major incentives involved: glycerin sales and government subsidies.

Table 1 [3]

Costs and Incentives	Price (per gallon)
Feedstock: Soy Oil	+ $1.80
Methanol ($1.00/gal)	+ $0.10
Process	+ $0.12
Glycerin Sale (10% of production)	- $0.30
US Fed Government Subsidy	- $0.85
Total:	$0.87
Prices refer to wholesale selling

As the figure shows, the cost of biodiesel production begins at roughly $2.02 per gallon however, government incentives lower that cost to only $0.87 per gallon (compared to the average production cost of diesel being $1.73).

The incentives provided for biodiesel production are beneficial to the manufacturer as well as the consumer by keeping production costs down and therefore making the sale price lower as well. The Commodity Credit Corp, a corporation that helps support industries that purchase excess crops, such as soybeans, is one of the primary sources of government incentives for biodiesel manufacturers. In biodiesel production, the Commodity Credit Corp provides $0.30 to $1.00 per gallon of biodiesel made from US feed. Other government incentives for biodiesel include a Federal Excise Tax (roughly $0.01 per percentage of biodiesel used in the fuel mixture, up to B20) and the Pennsylvania State Excise Tax (roughly $0.05 per gallon). Incentives such as these illustrate the government’s growing support for biodiesel as an alternative fuel source.

This government support for biodiesel stems from many areas. Primarily, the government recognizes biodiesel as a potential solution the urgent concern regarding fuel. Currently, the United States relies on overseas nations for approximately 56% (and rising) of its oil. By the year 2025, that dependency is estimated to be closer to 70% [12]. This foreign dependency is largely responsible for the constantly fluctuating gas prices here in the states. Not only does it cause price fluctuation, it also prevents the United States from obtaining full control over this important commodity. Biodiesel production would allow farmers within the United States to grow the soybeans necessary for the reaction. This would benefit the country in several ways. First, it would allow the government to regulate production directly through its own farms, ensuring that an adequate amount of biodiesel is produced at all times. Second, it would boost the American farming industry, in turn boosting the nation’s economy overall. Finally, it would give the United States a sense of freedom and independence from foreign nations for fuel imports. The ability to produce biodiesel within the country would decrease the potential threat of foreign nations withholding oil from the United States.

Consumer Benefits

The most direct consumer benefit of using biodiesel is the potential decreased price of fuel. Using biodiesel, in any combination with gasoline, has the potential to be significantly less expensive than using 100% gasoline or petroleum-based diesel. Current biodiesel production costs are slightly higher than petroleum based diesel. As technology increases and new methods of producing this fuel are developed, the production cost will decrease, thus decreasing the ‘pump price’.

Transitioning from petroleum-based diesel to biodiesel requires very little change. Unlike many other alterative fuel sources, such as electric and hydrogen, biodiesel is able to operate in conventional automotive engines without altering horsepower, torque or mileage. This eliminates the hassle of consumers needing to purchase a new vehicle in order to use biodiesel fuel. Not only is biodiesel capable of running in current automotive engines, it has proven to increase the engine life. Research shows that 1%-2% blends of biodiesel and petroleum diesel increases lubricity, reducing engine wear by nearly 60% [13].

CURRENT AND FUTURE APPLICATIONS

The concept of biodiesel may seem somewhat abstract, however with the severe depletion of subterranean oil, it is urgent that we seek alternative fuel sources. Europe has lead the way in biodiesel production with the United States catching on quickly. Several areas in the United States have adopted biodiesel as an alternative fuel source and are currently benefiting from the switch. Several states, including California, Texas, Iowa and Hawaii are home to many production plants, which are producing considerable amounts of biodiesel. Through their production, the transesterification process has been improved and refined; making it the most efficient it has ever been [4].

Biodiesel Today

In the United States, major biodiesel production is relatively new, having begun only in the late 1990s. As government funding and support continues to grow, so does production. Advances in technology and research regarding alternative fuels have also helped boost biodiesel production through improving the transesterification process, producing more fuel faster and easier.

Currently in the United States, there are forty-five active biodiesel plants and fifty-four additional plants in the making [14]. These plants, scattered across the country, are working to produce fuel that is used for a number of different purposes. The most common use of biodiesel is as an automotive fuel. As previously discussed, biodiesel is being used in place of and in combination with traditional diesel to fuel automobiles, fleets, mass transit, farm equipment, boats, trains, aircrafts and other vehicles. Some other practical uses of biodiesel include machine lubrication and heating. In addition, Cytosol, a commercial bio-solvent containing the veggie-oil methyl esters found in biodiesel, has proven to be helpful in oil spill cleanup. Its organic properties make it “effective in coagulating crude oil and allowing it to float to the surface of the water, where it can be collected” [4]. Additional uses of biodiesel are constantly being discovered and therefore, the demand for this fuel continues to rise.

From 1997 to 2004, biodiesel production rose from around one to over thirty million gallons per year [4]. Today, the production capacity is even greater and estimated to be at over seventy-five million gallons this year [15]. This exemplifies the industry’s ability to increase production in order to meet higher demands. It also supports the industry in their ability to continue to increase production as the demand grows in the future.

The Future of Biodiesel

With the complete depletion of subterranean oil in sight, it is extremely important that the world look to an alternative fuel source that is plentiful and renewable, making biodiesel a prime candidate. The future of biodiesel is promising and expected to gain much popularity and support. Rather than competing with current diesel fuels, the biodiesel industry intends to merge the two fuels, providing an outcome that is economically favorable on both ends. The industry’s ability to expand over the past few years is expected to continue as the range of products and uses of biodiesel also expands and diversifies.

THE FACTS

Producing biodiesel through the transesterification process will bring forth many beneficial changes to the world. The transesterification process allows for a renewable source of fuel to be prepared in a short amount of time and under normal conditions. This reduces the numerous plant safety implications of most oil refining plants, as well as permits the production of a cleaner fuel at lower costs [5].
In addition, through the transesterification process a fuel is created that can be mixed with present fuels to form other beneficial blends of fuel. These blends can be used in any automobile and even in home heating, or as machinery lubricants. The blends of biodiesel produced cause great reductions in the toxic emissions that cars normally give off due to the burning of gasoline.

Not only does transesterification produce an environmentally beneficial fuel, but also it makes a fuel that is economically beneficial. Fabricating biodiesel through the transesterification process reduces the dependence on the limited supply of oil fields. In addition, the use of soybeans for an input into the transesterification reaction allows for a very low cost of biodiesel production; hence, reducing the consumers cost for fuel.

Overall, the constant use of oil for fuel is nearing an end in the world, and a new fuel source desperately needs to be developed. Biodiesel through transesterification will be that new fuel source, which will bring about a cleaner environment, and an improved economy.

ACKNOWLEDGMENT

We would like to thank Ed Vescovi for his help in understanding the chemical and plant processes of producing biodiesel. In addition, we thank the librarians for their aid in finding research materials. We thank Len Kogut for his help in chemistry. We thank the Carnegie Mellon Center for Advanced Fuel Technology for providing information about the new research being performed on biodiesel production. This work was partly supported by Biology: Seventh Edition, by Raven, Johnson, Losos, and Singer.

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