Biodiesel has several distinct advantages compared with petrodiesel in addition to being fully competitive with petrodiesel in most technical aspects:
・Derivation from a renewable domestic resource, thus reducing dependence onand preserving petroleum.
・Biodegradability.
・Reduction of most exhaust emissions (with the exception of nitrogen oxides,NOX).
・Higher flash point, leading to safer handling and storage.
・Excellent lubricity, a fact that is steadily gaining importance with the advent
of low-sulfur petrodiesel fuels, which have greatly reduced lubricity. Adding
biodiesel at low levels (1・%) restores the lubricity.

other advantages are
Biodiesel fuels perform just as well as regular diesel fuels. A 1998 DOE test confirmed that using low blends of biodiesel will provide an increase in fuel economy. Laboratory tests, as well as road tests, have proven that biodiesel fuels have the same horsepower and torque as regular petrodiesel engines.

Engines will last longer when using biofuels. Traditional diesel engines have a much higher rate of engine wear (lubricity). Lubricity levels are even improved at low bio concentration levels. New regulations require petrodiesel engines to lower sulfur emissions considerably, making biodiesel blends much more attractive as a practical fuel to use. Biodiesel also offers a higher cetane ignition rating, which means that there is less engine noise pollution (dieseling).

At the production level, biodiesel fuel is a clean and affordable fuel for trucks, buses, farm equipment and other forms of heavy transportation. Biofuel refineries are much more simplistic and environmentally friendly in design than typical petrochemical refineries. With the continued rise of international fuel prices, biodiesel is set to become much more popular as a fuel option in the farming and transportation industries.

some those article take from http://www.alternative-energy-news.info

The fact that vegetable oils, animal fats, and their derivatives such as alkyl esters are suitable as diesel fuel demonstrates that there must be some similarity to petrodiesel fuel or at least to some of its components. The fuel property that best shows this suitability is called the cetane number In addition to ignition quality as expressed by the cetane scale, several other properties are important for determining the suitability of biodiesel as a fuel. Heat of combustion, pour point, cloud point, (kinematic) viscosity, oxidative stability, and lubricity are among the most important of these properties.

Believe it or not, the original diesel engines were designed to run on peanut oil! Today's engines are designed with petro-diesel in mind and therefore require a fuel with similar physical properties. Vegetable oil will burn in a diesel engine but only if its viscosity (how thick a liquid is) can be brought down to a level similar to petro-diesel.

To do this you can mix it with another fuel such as kerosene or petro-diesel, but you can also do it by heating it to about 160 °F. This option can allow you to run on pure vegetable oil, including waste vegetable oil.

The major reason that vegetable oils and animal fats are transesterified to alkyl esters (biodiesel) is that the kinematic viscosity of the biodiesel is much closer to that of petrodiesel. The high viscosity of untransesterified oils and fats leads to operational problems in the diesel engine such as deposits on various engine parts. Although there are engines and burners that can use untransesterified oils, the vast majority of engines require the lower-viscosity fuel.

Rudolf Diesel
It is generally known that vegetable oils and animal fats were investigated as diesel fuels well before the energy crises of the 1970s and early 1980s sparked renewed interest in alternative fuels. It is also known that Rudolf Diesel (1858–1913), the
inventor of the engine that bears his name, had some interest in these fuels. However,the early history of vegetable oil-based diesel fuels is often presented inconsistently, and “facts” that are not compatible with Diesel’s own statements are encountered freq u e n t l y .
Therefore, it is appropriate to begin this history with the words of Diesel himselfin his book Die Entstehung des Dieselmotors (1) [The Development (or Creation or Rise o r C o m i n g) of the Diesel Engine] in which he describes when the first seed ofdeveloping what was to become the diesel engine was planted in his mind. In the first chapter of the book entitled “The Idea,” Diesel states: “When my highly respected teacher, Professor Linde, explained to his listeners during the lecture on thermodynamics in 1878 at the P o l y t e c h n i k u m in Munich (note: now the Technical University
of Munich) that the steam engine only converts 6–10% of the available heat content of the fuel into work, when he explained Carnot’s theorem and elaborated that during the isothermal change of state of a gas all transferred heat is converted into work, I wrote in the margin of my notebook: ‘Study, if it isn’t possible to practically realize the isotherm!’ At that time I challenged myself! That was not yet an invention, not even the idea for it. From then on, the desire to realize the ideal Carnot process determined my existence. I left the school, joined the practical side, had to achieve my standing in
life. The thought constantly pursued me.”
This statement by Diesel clearly shows that he approached the development of the diesel engine from a thermodynamic point of view. The objective was to develop an efficient engine. The relatively common assertion made today that Diesel developed
“his” engine specifically to use vegetable oils as fuel is therefore incorrect. In a later chapter of his book entitled “Liquid Fuels,” Diesel addresses the use of vegetable oils as a fuel: “For [the] sake of completeness it needs to be mentioned that already in the year 1900 plant oils were used successfully in a diesel engine. During the Paris Exposition in 1900, a small diesel engine was operated on arachide (peanut) oil by the French Otto Company. It worked so well that only a few insiders knew about this inconspicuous circumstance. The engine was built for petroleum and was used for the plant oil without any change. In this case also, the consumption experiments resulted in heat utilization identical to petroleum.” A total of five diesel engines,

Preface

The diesel engine has been the engine of choice for heavy-duty applications in agriculture, construction, industrial, and on-highway transport for more 50 yr. Its early popularity could be attributed to its ability to use the portion of the petroleum crude oil that had previously been considered a waste product from the refining of gasoline. Later, the diesel's durability, high torque capacity, and fuel efficiency ensured its role in the most demanding applications. Although diesels have not been widely used in passenger cars in the United States (1%), they have achieved widespread acceptance in Europe with 33% of the total market (1). In the United States, on-highway diesel engines now consume 30 billion gal- lons of diesel fuel per year, and virtually all of this is in trucks (2). At the present time, only a minute fraction of this fuel is biodiesel. However, as petroleum becomes more expensive to locate and extract, and environmental concerns about diesel exhaust emissions and global warming increase, “biodiesel” is likely to
emerge as one of several potential alternative diesel fuels.

Definition

Very often, a broad, general description is used to define biodiesel in a way that is easy to understand by the general public. However, when these broad descriptions are adopted by an authoritative body as a formal definition, they can include a wide range of experimental fuels that are not biodiesel. The term “biodiesel” has a specific, technical definition that has been agreed to through a painstaking process by members of industry and government which has received full approval by the American Society of Testing and Materials (ASTM), the premier standard setting organization for fuels and fuel additives. That definition is used for purposes such as alternative fuel designation, EPA registration, or other regulatory purposes. Nonetheless, this specific technical definition can be confusing to the general public. We have, therefore, chosen to adopt two definitions for biodiesel. The “general definition” is a simple description for the general public. The “technical definition” should be adopted for use by customers for bid specification purposes or government entities for regulatory purposes.

General Definition of Biodiesel:
Biodiesel is a domestic, renewable fuel for diesel engines derived from natural oils like soybean oil, and which meets the specifications of ASTM D 6751.

Clarifying language to general definition:
Biodiesel can be used in any concentration with petroleum based diesel fuel in existing diesel engines with little or no modification. Biodiesel is not the same thing as raw vegetable oil. It is produced by a chemical process which removes the glycerin from the oil.

Technical Definition for Biodiesel (ASTM D 6751) and Biodiesel Blend:
Biodiesel, n—a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, designated B100, and meeting the requirements of ASTM D 6751.

Biodiesel Blend, n—a blend of biodiesel fuel meeting ASTM D 6751 with petroleum-based diesel fuel, designated BXX, where XX represents the volume percentage of biodiesel fuel in the blend.


Clarifying language to technical definition:
Biodiesel, as defined in D 6751, is registered with the US EPA as a fuel and a fuel additive under Section 211(b) of the Clean Air Act.

Biodiesel is typically produced by a reaction of a vegetable oil or animal fat with an alcohol such as methanol or ethanol in the presence of a catalyst to yield mono-alkyl esters and glycerin, which is removed.


www.biodiesel.org