Biodiesel is a term applied to diesel fuels manufactured of materials of biological origin (i.e. vegetable - bean, cottonseed, rapeseed etc. & animal fats - beef, pork and poultry, etc.) The process whereby these biologically originating oils are converted to biodiesel/biofuel is know as transesterfication.
In organic chemistry, an example of transesterification is the process of exchanging the alkoxy group of an ester compound by another alcohol. These reactions are often catalyzed by the addition of an acid or base. Transesterification: alcohol + ester → different alcohol + different ester.
Biodiesel is an alternative fuel to hydrocarbon (crude oil) based diesel. These BIO-fuels are utilized in diesel fuel applications and diesel engines.
Biodiesel is a renewable sustainable fuel that produces less CO2 than crude-oil-based conventional diesel. Blends of biodiesel and conventional hydrocarbon based diesel are products most commonly distributed for use in the retail diesel fuel marketplace.
Biodiesel is safe, biodegradable and reduces air pollutants, such as particulates, carbon monoxide and hydrocarbons. Blends of 20 percent biodiesel with 80 percent petroleum diesel (B20) can generally be used in unmodified diesel engines. Biodiesel can also be used in its pure form (B100), but may require certain engine modifications to avoid maintenance and performance problems.
Space-filling model of Methyl Linoleate, or Linoleic Acid Methyl Ester, a common Methyl Ester produced from Soybean or Canola oil and Methanol.
Space-filling model of Methyl Linoleate, or Linoleic Acid Methyl Ester, a common Methyl Ester produced from Soybean or Canola oil and Methanol.
Space-filling model of Ethyl Stearate, or Stearic Acid Ethyl Ester, an Ethyl Ester produced from Soybean or Canola oil and Ethanol.
Space-filling model of Ethyl Stearate, or Stearic Acid Ethyl Ester, an Ethyl Ester produced from Soybean or Canola oil and Ethanol.
Biodiesel has better lubricity than that of today's diesel fuels. During the manufacture of these, to comply with low SO2 engine emission limits set in modern standards, severe hydrotreatment is included. Biodiesel addition reduces wear increasing the life of the fuel injection equipment that relies on the fuel for its lubrication, such as high pressure injection pumps, pump injectors (also called unit injectors) and fuel injectors.
Older diesel Mercedes are popular for running on biodiesel.
The volumetric energy density of biodiesel is about 33 MJ/l. This is 9 % lower than regular Number 2 petrodiesel. Variations in biodiesel energy density is more dependent on the feedstock used than the production process. Still these variations are less than for petrodiesel. It has been claimed biodiesel gives better lubricity and more complete combustion thus increasing the engine energy output and partially compensating for the higher energy density of petrodiesel.
Biodiesel is a liquid which varies in color — between golden and dark brown — depending on the production feedstock. It is immiscible with water, has a high boiling point and low vapor pressure. Typical methyl ester biodiesel has a flash point of ~ 150 °C (300 °F). Biodiesel has a density of ~ 0.88 g/cm³, less than that of water.
Biodiesel has a viscosity similar to petrodiesel, the current industry term for diesel produced from petroleum. Biodiesel has high lubricity and virtually no sulfur content, and it is often used as an additive to Ultra-Low Sulfur Diesel (ULSD) fuel.
Much of the world uses a system known as the "B" factor to state the amount of biodiesel in any fuel mix: fuel containing 20% biodiesel is labeled B20, while pure biodiesel is referred to as B100. It is common to see B99, since 1% petrodiesel is sufficiently toxic to retard mold.
Biodiesel refers to a non-petroleum-based diesel fuel consisting of short chain alkyl (methyl or ethyl) esters, typically made by transesterification of vegetable oils or animal fats, which can be used (alone, or blended with conventional petrodiesel) in unmodified diesel-engine vehicles. Biodiesel is distinguished from the straight vegetable oil (SVO) (aka "waste vegetable oil", "WVO", "unwashed biodiesel", "pure plant oil", "PPO") used (alone, or blended) as fuels in some converted diesel vehicles. "Biodiesel" is standardized as methyl ester and other non-diesel fuels of biological origin are not included.
Origin
On August 31, 1937, G. Chavanne of the University of Brussels (Belgium) was granted a patent for a 'Procedure for the transformation of vegetable oils for their uses as fuels' (fr. 'Procédé de Transformation d’Huiles Végétales en Vue de Leur Utilisation comme Carburants') Belgian Patent 422,877. This patent described the alcoholysis (often referred to as transesterification) of vegetable oils using ethanol (and mentions methanol) in order to separate the fatty acids from the glycerol by replacing the glycerol with short linear alcohols. This appears to be the first account of the production of what is known as 'biodiesel' today.
Applications
Biodiesel can be used in pure form (B100) or may be blended with petroleum diesel at any concentration in most modern diesel engines. Biodiesel has different solvent propereties than petrodiesel, and will degrade natural rubber gaskets and hoses in vehicles (mostly found in vehicles manufactured before 1992), although these tend to wear out naturally and most likely will have already been replaced with FKM, which is nonreactive to biodiesel. Biodiesel has been known to break down deposits of residue in the fuel lines where petrodiesel has been used.[6] As a result, fuel filters may become clogged with particulates if a quick transition to pure biodiesel is made. Therefore, it is recommended to change the fuel filters on engines and heaters shortly after first switching to a biodiesel blend.
Vehicular use and manufacturer acceptance
Research sponsored by petroleum producers has found petroleum diesel better for car engines than biodiese. This has been disputed by independent bodies, including for example the Volkswagen environmental awareness division, who note that biodiesel reduces engine wear. Pure biodiesel produced 'at home' is in use by thousands of drivers who have not experienced failure. In spite of the fact that biodiesel sold to the public is held to high standards set by national standards bodies, biodiesel has been widely available at fuel stations for less than a decade, and hence is reasonably perceived to carry more risk than older fuels.
Volkswagen, for example, may tell European customers that they have no problem with biodiesel, while dealers in the USA have posted notices that only blends with less than 5% biodiesel are permitted. In 2005, DaimlerChrysler released Jeep Liberty CRD diesels from the factory into the American market with 5% biodiesel blends, indicating at least partial acceptance of biodiesel as an acceptable diesel fuel additive. In 2007, DiamlerChrysler indicated intention to increase warranty coverage to 20% biodiesel blends if biofuel quality in the United States can be standardized.
Distribution is possible using today's diesel infrastructure as long as minor adjustments are made, such as replacement of old solvent-prone fittings and hoses, filtering of loosened fossil fuel varnishes, and prevention of the growth of mold and care taken to prevent coagulation at colder temperatures.
Its use and production are increasing rapidly. Fuel stations make biodiesel readily available to consumers across Europe, and increasingly in the USA and Canada, and a growing number of transport fleets use it as an additive in their fuel. Biodiesel is often more expensive to purchase than petroleum diesel but this is expected to diminish due to economies of scale and agricultural subsidies versus the rising cost of petroleum as reserves are depleted.
Railroad use
The British businessman Richard Branson's Virgin Voyager train, number 220007 Thames Voyager, billed as the world's first "biodiesel train" was converted to run on 80% petrodiesel and only 20% biodiesel, and is expected to save 14% on direct emissions.
Aircraft use
Aircraft manufacturers are understandably even more cautious, but some test flights have been performed and commercial passenger jet testing has been announced by Virgin Atlantic's Richard Branson.
The world's first biofuel-powered commercial aircraft took off from London's Heathrow AirportFebruary 24, 2008 and touched down in Amsterdam on a demonstration flight hailed as a first step towards "cleaner" flying.
As a heating oil
Biodiesel can also be used as a heating fuel in domestic and commercial boilers. Older furnaces may contain rubber parts that would be affected by biodiesel's solvent properties, but can otherwise burn biodiesel without any conversion required. Care must be taken at first, however, given that varnishes left behind by petrodiesel will be released and can clog pipes- fuel filtering and prompt filter replacement is required. Another approach is to start using biodiesel as blend, and decreasing the petroleum proportion over time can allow the varnishes to come off more gradually and be less likely to clog. Thanks to its strong solvent properties, however, the furnace is cleaned out and generally becomes more efficient.A technical research paper describes laboratory research and field trials project using pure biodiesel and biodiesel blends as a heating fuel in oil fired boilers. During the Biodiesel Expo 2006 in the UK, Andrew J. Robertson presented his biodiesel heating oil research from his technical paper and suggested that B20 biodiesel could reduce UK household CO2 emissions by 1.5 million tonnes per year
Contamination by waterBiodiesel may contain small but problematic quantities of water. Although it is hydrophobicmolecules), it is said to be, at the same time, hygroscopic to the point of attracting water molecules from atmospheric moisture[19]; one of the reasons biodiesel can absorb water is the persistence of mono and diglycerides left over from an incomplete reaction. These molecules can act as an emulsifier, allowing water to mix with the biodiesel.[citation needed]condensation. The presence of water is a problem because: (non-miscible with water In addition, there may be water that is residual to processing or resulting from storage tank
- Water reduces the heat of combustion of the bulk fuel. This means more smoke, harder starting, less power.
- Water causes corrosion of vital fuel system components: fuel pumps, injector pumps, fuel lines, etc.
- Water & microbes cause the paper element filters in the system to fail ( rot), which in turn results in premature failure of the fuel pump due to ingestion of large particles.
- Water freezes to form ice crystals near 0 °C (32 °F). These crystals provide sites for nucleation and accelerate the gelling of the residual fuel.
- Water accelerates the growth of microbe colonies, which can plug up a fuel system. Biodiesel users who have heated fuel tanks therefore face a year-round microbe problem.
Previously, the amount of water contaminating biodiesel has been difficult to measure by taking samples, since water and oil separate. However, it is now possible to measure the water content using water in oil sensors.
Biodiesel can also be used as a heating fuel in domestic and commercial boilers. and would only require around 330,000 hectares of arable land for the required biodiesel for the UK heating oil sector. The paper also suggests that existing oil boilers can easily and cheaply be converted to biodiesel if B20 biodiesel is used.
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