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Biodiesel is non- flammable, and in contrast to petroleum diesel it is non- explosive, with a flash pointThe flashpoint of a fuel is the lowest temperature at which it can form an ignitable mix with air. At this temperature the vapour may cease to burn when the source of ignition is removed. A slightly higher temperature, the fire point, is defined at which of 150 ° CThe degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius ( 1701 1744), who first proposed it in 1742. The Celsius temperature scale was designed so that the freezing point of water is 0 degrees, and the boiling po for biodiesel as compared to 64 °C for petrodiesel. Unlike petrodiesel, it is biodegradable and non- toxic, and it significantly reduces toxic and other emissions when burned as a fuel. Chemically, it is a fuel comprised of a mix of mono- alkyl esterFor the Biblical Ester, see Esther. For the town, see Ester, Alaska. In organic chemistry and biochemistry esters are substances that have the functional group R´-COOR" (the carbon is double-bonded to one oxygen atom and single-bonded to another) and conss of long chain fatty acids. The most common form uses methanol to produce methyl esters, though ethanol can be used to produce an ethyl ester biodiesel. A lipid transesterification production process is used to convert the base oil to the desired esters and remove free fatty acids. A byproduct of the process is the production of glycerol.
Currently, biodiesel is more expensive to produce than petroleum diesel, which appears to be the primary factor keeping it from being in more widespread use. Current worldwide production of vegetable oil and animal fat is not enough to replace liquid fossil fuel use. Some environmental groups, notably NRDC object to the vast amount of farming and the resulting over- fertilization, pesticide use, and land use conversion that would be needed to produce the additional vegetable oil.
During the 1920s, diesel engine manufacturers altered their engines to utilize the lower viscosity of the fossil fuel (petrodiesel) rather than vegetable oil, a biomass fuel. The petroleum industries were able to make inroads in fuel markets because their fuel was much cheaper to produce than the biomass alternatives. The result was, for many years, a near elimination of the biomass fuel production infrastructure. Only recently have environmental impact concerns and a decreasing cost differential made biomass fuels such as biodiesel a growing alternative.
In the 1990s, France launched the local production of biodiesel fuel (known locally as diester) obtained by the transesterification of rapeseed oil. It is mixed to the proportion of 5% into regular diesel fuel, and to the proportion of 30% into the diesel fuel used by some captive fleets ( public transportation). Renault, Peugeot and other manufacturers have certified truck engines for use with up to this partial biodiesel. Experiments with 50% biodiesel are underway.
From 1978 to 1996, the U.S. National Renewable Energy Laboratory experimented with using algae as a biodiesel source in the "Aquatic Species Program". A recent paper from the UNH Biodiesel Group, [1] offers calculations for the realistic replacement of all vehicular fuel with biodiesel by utilizing algae that has an over 50% natural oil content.
Biodiesel is a clear amber-yellow liquid with a viscosity similar to petrodiesel (the industry term for diesel produced from petroleum). Much of the world uses a system known as the "BD factor" to state the amount of biodiesel in any fuel mix, in contrast to the "BA" system used for bioalcohol mixes. For example, 20% biodiesel is labeled BD20. Pure biodiesel, 100%, is referred to as BD100. In the United States, a similar system is used, but the "D" is dropped (B100, B20, B5, etc.).
The international standard for biodiesel is ISO 14214. Another is the ASTM International standard ASTM D 6751, which is the most common standard referenced in the United States. In Germany, the requirements for biodiesels are fixed in a DIN standard. There are standards for three different varieties of biodiesel, which is made of different oils:
The standards make sure that the following important factors in the fuel production process are satisfied:
The basic industrial tests to see if the product conforms to the standard typically includes gas chromatography that verifies only the more important of the variables above. More complete testings cost more. Fuel meeting the quality standards is very non-toxic, with a toxicity rating ( LD50) of greater than 50ml/KG. This translates to greater than 3 liters having to be consumed for an average 60 KG person to cause death 50% of the time. The common comparison is that this makes biodiesel ten times less toxic than table salt.
Biodiesel can be mixed with petroleum diesel at any concentration in most modern engines, although it has the disadvantage of degrading rubber gaskets and hoses in older vehicles (prior to 1992). Biodiesel is a better solvent than petrodiesel and has been known to break down deposits of residue in the fuel lines of vehicles which usually run on petroleum. Fuel filters may become clogged with particulates if a quick transition to pure biodiesel is made, but the biodiesel cleans the engine in the process.
In a study at a U.S. military base, a biodiesel blend was used as a replacement for heating oil at housing on the base. Due to the solvent power of biodiesel, residues that had been present in fuel tanks for decades were dissolved. The particulate component of the residues caused repeated clogging of fuel strainers, requiring repeated replacement, cleaning, and in some cases installation of higher capacity filters. Due to the relatively smaller surface area and service life of fuel tanks in motor vehicles and mobile equipment, filter clogging is less prevalent but still a factor to be considered.
Environmental benefits in comparison to petroleum based fuels include:
Pure biodiesel (BD100 or B100) can be used in any petroleum diesel engine, though it is more commonly used in lower concentrations. Some areas have mandated ultra-low sulfur diesel (ULSD) petroleum, which reduces the natural viscosity and lubricity of the fuel because the sulfur and certain other materials have been removed. Additives are required to make it properly flow in engines, and biodiesel is one popular alternative. Ranges as low as 2% (BD2 or B2) have been shown to restore lubricity. Also, many municipalities have started using 5% biodiesel (BD5 or B5) in snow-removal equipment and other systems.
Since biodiesel is more often used in a blend with petroleum diesel, there is less information and formal studies about the effects on pure biodiesel in unmodified engines and vehicles in actual use. Fuel meeting the standards and engine parts that can withstand the greater solvent properties of biodiesel is expected to, and in reported cases does, run without any additional problems over petroleum diesel.
Main article: Biodiesel production
A variety of biolipids can be used to produce biodiesel. These include:
Many advocates suggest that waste vegetable oil is the best source of oil to produce biodiesel. However, the available supply is drastically less than the amount of petroleum-based fuel that is burned for transportation and home heating in the world. According to the United States Environmental Protection Agency (EPA), restaurants in the US produce about 3 million gallons of waste cooking oil annually. Although it is economically profitable to use WVO to produce biodiesel, it is even more profitable to convert WVO into other products such as soap. Hence, most WVO that is not dumped into landfills is used for these other purposes. Animal fats are similarly limited in supply, and it would not be efficient to raise animals simply for their fat. However, producing biodiesel with animal fat that would have otherwise been discarded could replace a small percentage of petroleum diesel usage.
The estimated transportation fuel and home heating oil use in the United States is about 230,000 million gallons. (Briggs, 2004) Waste vegetable oil and animal fats would not be enough to meet this demand. In the United States, estimated production of vegetable oil for all uses is about 33,000 million pounds (15,000,000 t) or 4,500 million US gallons (17,000,000 m³)), and estimated production of animal fat is 12,000 million pounds (5,000,000 t). (Van Gerpen, 2004)
For a truly renewable source of oil, crops or other similar cultivatable sources would have to be considered. Plants utilize photosynthesis to convert solar energy into chemical energy. It is this chemical energy that biodiesel stores and is released when it is burned. Therefore plants can offer a sustainable oil source for biodiesel production. Different plants produce usable oil at different rates. Some studies have shown the following annual production:
The production of algae to harvest oil for biodiesel has not been undertaken on a commercial scale, but working feasibility studies have been conducted to arrive at the above number. Specially bred mustard varieties can produce reasonably high oil yields, and have the added benefit that the meal leftover after the oil has been pressed out can act as a effective and biodegradable pesticide. There is ongoing research into finding more suitable crops and improving oil yield. Using the current yields, vast amounts of land would have to be put into production to produce enough oil to completely replace fossil fuel usage.
Soybeans are not a very efficient crop solely for the production of biodiesel, but their common use in the United States for food products has led to soybean biodiesel becoming the primary source for biodiesel in that country. Soybean producers have lobbied to increase awareness of soybean biodiesel, expanding the market for their product. In Europe, rapeseed is the most common base oil used in biodiesel production.
According to a study written by Drs. Van Dyne and Raymer for the Tennessee Valley Authority, the average US farm consumes fuel at the rate of 82 litres per hectare (8.75 US gallons per acre) of land to produce one crop. However, average crops of rapeseed produce oil at an average rate of 1,029 L/ha (110 US gal/acre), and high-yield rapeseed fields produce about 1,356 L/ha (145 US gal/acre). The ratio of input to output in these cases is roughly 1:12.5 and 1:16.5. However, these statistics by themselves are not enough to show whether such a change makes economic sense.
Additional factors must be taken into account, such as: the fuel equivalent of the energy required for processing, the yield of fuel from raw oil, the return on cultivating food, and the relative cost of biodiesel versus petrodiesel. A 1998 joint study by the U.S. Department of Energy (DOE) and the U.S. Department of Agriculture (USDA) traced many of the various costs involved in the production of biodiesel and found that overall, it yields 3.2 units of fuel product energy for every unit of fossil fuel energy consumed. [3] That measure is referred to as the energy yield. A comparison to petroleum diesel, petroleum gasoline and bioethanol using the USDA numbers can be found at the Minnesota Department of Agriculture website. In the comparison petroleum diesel fuel is found to have a 0.843 energy yield, along with 0.805 for petroleum gasoline, and 1.34 for bioethanol. The 1998 study used soybean oil primarily as the base oil to calculate the energy yields. It is concievable that higher oil yielding crops could increase the energy yield of biodiesel.
Some nations and regions that have pondered transitioning fully to biofuels have found that doing so would require immense tracts of land if traditional crops are used. Considering only traditional plants and analyzing the amount of biodiesel that can be produced per acre of cultivated land, some have concluded that it is likely that the United States, which uses more energy per capita than any other country, does not have enough arable land to fuel all of the nation's vehicles. Other developed and developing nations may be in better situations, although many regions cannot afford to divert land away from food production. For third world countries, biodiesel sources that use marginal land could make more sense, e.g. honge nuts [4] grown along roads.
More recent studies using a species of algae that has oil contents of as high as 50% have concluded that as little as 28,000 km² or .3% of the land area of the US could be utilized to produce enough biodiesel to replace all transportation fuel the country currently utilizes. Further encouragement comes from the fact that the land that could be most effective in growing the algae is desert land with high solar irradiation, but lower economic value for other uses and that the algae could utilize farm waste and excess CO2 from factories to help speed the growth of the algae. [5]
The direct source of the energy content of biodiesel is solar energy captured by plants during photosynthesis. The website biodiesel.co.uk discusses the positive energy balance of biodiesel:
Biodiesel is becoming of interest to companies interested in commercial scale production as well as the more usual home brew biodiesel user and the user of straight vegetable oil or waste vegetable oil in diesel engines. Homemade biodiesel processors are many and varied.
Biodiesel is commercially available in most oilseed-producing states in the United States. At this time, it is considerably more expensive than fossil diesel, though it is still commonly produced in relatively small quantities (in comparison to petroleum products and ethanol). Many farmers who raise oilseeds use a biodiesel blend in tractors and equipment as a matter of policy, to foster production of biodiesel and raise public awareness. It is sometimes easier to find biodiesel in rural areas than in cities. Similarly, some agribusinesses and others with ties to oilseed farming use biodiesel for public relations reasons. In 2003 some tax credits are available in the U.S. for using biodiesel. In 2002 almost 3.5 million gallons (13,000 m³) of commercially produced biodiesel were sold in the U.S., up from less than 0.1 million US gallons (380 m³) in 1998. Due to increasing pollution control requirements and tax relief, the U.S. market is expected to grow to 1 or 2 billion US gallons (4,000,000 to 8,000,000 m³) by 2010. The price of biodiesel has come down from an average $3.50 per US gallon ($0.92/l) in 1997 to $1.85 per US gallon ($0.49/l) in 2002. However this is still higher than petrodiesel which averaged about $0.85 per US gallon ($0.22/l) in 2002 before road tax is added.
Biodiesel is available in the United Kingdom, at prices comparable with petroleum-based diesel - high fuel taxation making the cost of production a small fraction of the retail cost - but is so far not widely available or in very great demand.
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