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Biodiesel is not a new fuel in North America. In fact, biodiesel activities date back to the
late 70's and early 80's. Since the oil embargo of 1973 by the Organization of Petroleum Exporting
Countries (OPEC), a significant amount of research on biodiesel and other domestically produced fuel
has been conducted by various universities, government agencies, and research organizations. The
general conclusion is that biodiesel is a technically acceptable blending stock for conventional
petroleum diesel. The cost of using biodiesel is quite economical when compared to the total cost
to use other alternative fuels.
Biodiesel is defined as the mono alkyl esters of long chain fatty acids derived from renewable
lipid sources. Biodiesel is typically produced through the reaction of a vegetable oil or animal
fat with methanol in the presence of a catalyst to yield glycerin and biodiesel (chemically called
methyl esters). Biodiesel is registered with the US Environmental Protection Agency as a pure fuel
or as a fuel additive and is a legal fuel for commerce. Biodiesel is an alternative fuel which is
typically blended with petroleum diesel for use in compression ignition (diesel) engines. Its physical
and chemical properties as it relates to operation of diesel engines are similar to petroleum based diesel fuel.
Emissions Reductions
The use of biodiesel in a conventional diesel engine results in substantial reduction of unburned hydrocarbons, carbon monoxide,
and particulate matter. Emissions of nitrogen oxides are either slightly reduced or slightly increased depending on the duty cycle
and testing methods. Particulate emissions from conventional diesel engines can be divided into three components. Each component is
present in varying degrees depending on fuel properties, engine design and operating parameters. Also, the use of biodiesel reduces CO2
in the atmosphere, since growing soybeans consumes nearly four times as much CO2 as the amount of CO2 produced from biodiesel exhaust.
Lubricity
With the lubricity of conventional diesel fuel being scrutinized due to processing changes required to reduce the sulfur and aromatic
content of diesel fuel, biodiesel use can be demonstrated to be a benefit. Lubricity test utilizing both the High Frequency Reciprocating
Rig (HFRR) and the Ball on Cylinder Lubricity Evaluator (BOCLE) have demonstrated the lubricity advantage of biodiesel.
Biodegradability
Biodiesel also has desirable degradation attributes. Studies at the University of Idaho have been conducted to determine the biodegradation
of biodiesel in an aqueous solution. Biodiesel was compared to diesel fuel and dextrose. Biodiesel samples degraded more rapidly than the dextrose
control and were 95 percent degraded at the end of 28 days. The diesel fuel was approximately 40 percent degraded after 28 days.
Another study conducted at the University of Idaho tested the "Biodegradability of Biodiesel in the Aquatic Environment" by the CO2 evolution method
and gas chromatography (GC), comparing the results with regular diesel. According to the University of Idaho's report, under aerobic conditions and
nutrient supply (N, P), microorganisms will metabolize a substance to two final products, CO2 and water. Therefore, CO2 is presumed to be the prevalent
indicator of organic substance breakdown. If the substrate is the only carbon source, the amount of CO2 evolved will be proportional to the carbons
consumed by microorganisms from the test substrate. Thus, the percentage of CO2 evolution is proportional to the percentage of substrate degradation.
The maximum percent CO2 evolution from several samples of biodiesel produced were between 85.54-88.49 percent in 28 days, the same as that of dextrose,
indicating there is no difference in their biodegradability. Yet, the CO2 evolution from the diesel flasks was only 26.24 percent. It should also be noted
that biodiesel blends accelerate the biodegradability of No. 2 diesel. For example a 20% biodiesel blend degrades twice as fast as No. 2 diesel.
This illustrates that biodiesel use has demonstrated biodegradability benefits at levels lower than 100%.
Toxicity
Impacts on human health represent a significant criteria as to the suitability of a fuel for commercial applications. Health effects can be measure in
terms of fuel toxicity to the human body as well as health impacts due to exhaust emissions. Tests conducted by Wil Research Laboratories, Inc.
investigated the acute oral toxicity of pure biodiesel fuel as well as a 20% blend of biodiesel with No. 2 diesel (B20) in a single-dose study on
rats. the LD50 of pure biodiesel, as well as B20, was found to be greater than 5000 mg/kg, although hair loss was noted on one sample in the B20 group.
The acute dermal toxicity of neat biodiesel was evaluated in a single dose study involving rabbits. The LD50 of biodiesel was found to be greater than
2000 mg/kg and the 2000 mg/kg dose level was found to be a No Observable Effect Level (NOEL) for systemic toxicity.
Acute aquatic toxicity tests with Daphnia Magna have also been conducted. Table salt (NaCl), diesel and biodiesel were compared to each other. The LC50
count (the concentration where 50 percent of the Daphnia Magna have died and 50 percent were still alive) for table salt was 3.7 parts per million (ppm).
Fifty percent of the Daphnia Magna were dead at 1.43 ppm for diesel fuel. The LC50 number varied for biodiesel from 23 ppm to 332 ppm. There biodiesel
is less toxic than diesel fuel.
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