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Bio-diesel - Diesel Fuel, Made from vegetable oil, in a process called transesterification.
Background Information on Biodiesel
What is Biodiesel?
Biodiesel is a diesel fuel substitute produced from renewable sources such as vegetable oils, animal fats, and recycled cooking oils. Chemically, it 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 or ethanol in the presence of a catalyst to yield glycerin and biodiesel (chemically called methyl or ethyl esters). Biodiesel can be used in neat form, or blended with petroleum diesel for use in diesel engines. Its physical and chemical properties as it relates to operation of diesel engines are similar to petroleum based diesel fuel.
Biodiesel’s Attributes
Across the globe environmental concerns and energy security issues have prompted legislation and regulatory actions spurring demand for alternative fuels such as biodiesel. However, the greatest driving force for the use of biodiesel and biodiesel blends is the need to have a fuel that fulfills all of the environmental and energy security needs previously mentioned which does not sacrifice operating performance. One of the largest roadblocks to the use of alternative fuels is the change of performance noticed by users. Biodiesel has many positive attributes associated with its use, but by far the most noted attribute highlighted by fleet managers is the similar operating performance to conventional diesel fuel and the lack of changes required in facilities and maintenance procedures. Other attributes of biodiesel and biodiesel blends are detailed below:
Biodegradability
Biodiesel has desirable degradation attributes which make it the fuel of choice by environmentally conscious boaters. Studies at the University of Idaho compared the biodegradation of biodiesel in an aqueous solution to diesel fuel and dextrose (sugar). Biodiesel samples degraded more rapidly than dextrose, and were 95 percent degraded at the end of 28 days. The diesel fuel was approximately 40 percent degraded after 28 days.
It should also be noted that blending biodiesel with diesel fuel accelerates its biodegradability. For example blends of 20% biodiesel and 80% diesel fuel degrade twice as fast as No. 2 diesel. Thus, biodiesel use has demonstrated biodegradability benefits at levels lower than 100%. Simply stated, neat biodiesel degrades as fast as sugar and a B20 blend will degrade twice as fast as petroleum based diesel fuel.
Flash Point
The flash point of a fuel is defined as the temperature at which the fuel becomes a mixture that will ignite when exposed to a spark or flame. The flash point of biodiesel has been tested and reported by various sources. Specific testing at Southwest Research Institute concluded that the flash point of biodiesel blends increases as the percentage of biodiesel increases. Therefore pure biodiesel and blends of biodiesel with petroleum diesel are safer to store, handle, and use than conventional diesel fuel. Neat biodiesel has a flash point over 300 Fahrenheit, well above the flash point of petroleum based diesel fuel.
Toxicity
The impact on human health is a significant criteria when considering the suitability of a fuel for commercial applications. Health effects can be measured in terms lie the fuel's toxicity to the human body or 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 B20 in a single-dose study on rats. The median lethal dose (LD50) of pure biodiesel, as well as B20, was found to be greater than 5000 mg/kg. 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. There were no deaths, remarkable body weight changes or gross necropsy findings for the LD50 dose levels for each of the studies.
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), 1.43 ppm for diesel fuel. and for biodiesel it ranged from 23 ppm to 332 ppm. Therefore, biodiesel is less toxic than diesel fuel and table salt.
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 of the engine and testing methods employed.
Particulate emissions from conventional diesel engines are generally divided into three components. Each component is present in varying degrees depending on fuel properties, engine design and operating parameters. The first component, and the one most closely related to the visible smoke often associated with diesel exhaust, is the carbonanceous material. This material is composed of sub-micron sized carbon particles which are formed during the diesel combustion process. Is especially prevalent under conditions when the fuel-air ratio is overly rich. The second component is hydrocarbon material which is absorbed on the carbon particles, commonly referred to as the soluble fraction. A portion of this material results from incomplete combustion of the fuel. The remainder is derived from engine lube oil that passes by the piston oil rings. The third particulate component is comprised of sulfates and bound water. The amount of this material is directly related to the fuel sulfur content.
The use of biodiesel decreases the solid carbon fraction of particulate matter (since the oxygen in biodiesel enables more complete combustion to CO2), eliminates the sulfate fraction (as there is no sulfur in the fuel), while the soluble, or hydrocarbon, fraction stays the same or is increased. Therefore, biodiesel works well with new technologies such as catalysts (which reduces the soluble fraction of diesel particulate but not the solid carbon fraction), particulate traps, and exhaust gas recirculation.
Health Effects
Evidence does exist which indicates that diesel particulate matter is a potential carcinogen. In 1988, the National Institute for Occupational Safety and Health (NIOSH) recommended that whole diesel exhaust be regarded as "a potential occupational carcinogen," as defined in the Cancer Policy of the Occupational Safety and Health Administration. The use of biodiesel decreases most regulated emissions. Research results indicate that particulate matter (specifically the carbon or insoluble fraction), hydrocarbons, and carbon monoxide are significantly reduced.
In addition to reducing the overall levels of pollutants and carbon, the compounds that are prevalent in biodiesel and diesel fuel exhaust are different. Research conducted by Southwest Research Institute on a Cummins N14 engine indicates that biodiesel exhaust has a less harmful impact on human health than petrodiesel. Biodiesel emissions have decreased levels of all target polycyclic aromatic hydrocarbons (PAH) and nitrited PAH compounds, as compared to petroleum diesel exhaust. PAH and nPAH compounds have been identified as potential cancer causing co mpounds. All of the PAH compounds were reduced by 75 to 85 percent, with the exception of benzo(a)anthracene, which was reduced by roughly 50 percent. The target nPAH compounds were also reduced dramatically with biodiesel fuel, with 2-nitrofluorene and 1-nitropyrene reduced by 90 percent, and the rest of the nPAH compounds reduced to only trace levels. All of these reductions are due to the fact the biodiesel fuel contains no aromatic compounds of any kind, including PAHs.
In addition, the total speciated hydrocarbon mass of biodiesel is nearly 50 percent less than that measured for conventional diesel fuel, and the associated ozone potential is reduced by the same amount. Significant reductions in most aldehyde compounds were also observed with biodiesel, with formaldehyde and acetaldehyde 30 percent lower than the levels observed for conventional diesel fuel.
Lubricity
In the United States the sulfur level of diesel fuel that is used for on-road purposes is limited to 0.05% by weight. This limit was mandated in October 1993 as a method to decrease particulate matter emitted from diesel powered vehicles. With the introduction of mandated Environmental Protection Agency (EPA) low-sulfur diesel fuel, fleet operators began to encounter premature wear and/or failure of injector pumps in increasing numbers. Pump manufacturers such as Stanadyne and Bosch began recommending the use of lubricity additives to alleviate the serious damage that the reduced sulphur content of low sulfur diesel was causing to their injection pumps.
Many petroleum distributors are only marketing low-sulfur diesel even though it remains legal to sell high-sulfur diesel in off-road markets. Testing at labs such as Southwest Research Institute, Stanadyne Automotive, and Engineering Testing Services have demonstrated that biodiesel provides significant lubricity improvement over petroleum diesel fuel. Lubricity results of biodiesel and petroleum diesel using the High Frequency Reciprocating Rig test indicat that there is a marked improvements in lubricity when biodiesel is added to conventional diesel fuel, even at blend levels below 1%.
Infrastructure
In general, the standard storage and handling procedures used for petroleum diesel can be used for biodiesel. The fuel should be stored in a clean, dry, dark environment. Temperature extremes should be avoided. Acceptable storage tank materials include stainless steel, fluorinated polyethylene, and fluorinated polypropylene. Biodiesel has a solvent effect which may release deposits accumulated on tank walls and pipes from previous fuel storage. The release of deposits may clog filters initially and precautions should be taken .
Macroeconomic Impacts of Biodiesel Utilization
An important factor that is not usually considered when calculating the costs and benefits of industrial feedstock materials is the macroeconomic effect associated with domestically produced, renewable energy sources. Economic benefits of a biodiesel industry would include
value added to the feedstock (oilseeds, fats, or yellow grease), an increased number of jobs, an increased tax base from plant operations and income taxes, and investments in plant and equipment.
Dr. Dermot Hayes, an agricultural economist with Iowa State University, concluded that there are three possible benefits that would accrue to the state from a biodiesel industry;
By expanding demand for soybean oil, biodiesel allows soybean processors to pay more for soybeans,
soybean farmers near the biodiesel plant would receive slightly higher prices for soybeans, and
the presence of a facility that creates energy from soybean would add value to the state's industrial and income base.
Previous economic work demonstrated that for each $1 generated in the state's soybean processing industry an additional $1.50 is generated in the service sector. Of the total amount generated a portion of those revenues is received by the state's treasury in the form of income, sales, and corporate taxes.
Dr. Hayes concluded that, "If the state of Iowa were to mandate the use of a 20% biodiesel blend in its state vehicle fleet where feasible, the total additional cost of this policy would range from $400,000 to $500,000. In this eventuality, the Department of Transportation would use a biodiesel blend in about 1/6 of its fleet. If it could be shown that this policy would result in a new five million gallon biodiesel plant in the state, then the policy would create more new tax revenues than it would cost and would clearly be in the best interest of the state".
Biodiesel plant production economics are highly dependent upon the cost associated with feedstock procurement. Feedstock costs represent approximately 75 to 80% of the overall costs of biodiesel production. Therefore, capital expenditures do not have a significant impact on the overall cost of producing biodiesel. Biodiesel production facilities tend to be more scale neutral than other technologies. Economic studies suggest plants can be sized according to regional conditions.
Economic work conducted in 1993 (Weber, 1993) indicated that biodiesel produced in a community based system has the potential to be economically competitive with industrial scale plants. Generally speaking, this statement can only be true for specific locations where a large spread exists between the price that farmers receive for their oilseed and the price paid for their protein meal. More specifically, in order for this concept to be implemented a large number of producers must be in one community and have protein needs as well as the capacity to produce oilseed crops. Although the results of this work are encouraging, these conditions may or may not be prevalent in rural communities.