Biodiesel
Biodiesel is a renewable biofuel, a form of diesel fuel, derived from biological sources like vegetable oils, animal fats, or recycled greases, and consisting of long-chain fatty acid esters. It is typically made from fats.
The roots of biodiesel as a fuel source can be traced back to when J. Patrick and E. Duffy first conducted transesterification of vegetable oil in 1853, predating Rudolf Diesel's development of the diesel engine. Diesel's engine, initially designed for mineral oil, successfully ran on peanut oil at the 1900 Paris Exposition. This landmark event highlighted the potential of vegetable oils as an alternative fuel source. The interest in using vegetable oils as fuels resurfaced periodically, particularly during resource-constrained periods such as World War II. However, challenges such as high viscosity and resultant engine deposits were significant hurdles. The modern form of biodiesel emerged in the 1930s, when a method was found for transforming vegetable oils for fuel use, laying the groundwork for contemporary biodiesel production.
The physical and chemical properties of biodiesel vary depending on its source and production method. The trade association National Biodiesel Board defines "biodiesel" as a mono-alkyl ester. It has been experimented with in railway locomotives and power generators. Generally characterized by a higher boiling point and flash point than petrodiesel, biodiesel is slightly miscible with water and has distinct lubricating properties. Its calorific value is approximately 9% lower than that of standard diesel, impacting fuel efficiency. Biodiesel production has evolved significantly, with early methods including the direct use of vegetable oils, to more advanced processes like transesterification, which reduces viscosity and improves combustion properties. Notably, biodiesel production generates glycerol as a by-product, which has its own commercial applications.
Biodiesel's primary application is in transport. There have been efforts to make it a drop-in biofuel, meaning compatible with existing diesel engines and distribution infrastructure. However, it is usually blended with petrodiesel, typically to less than 10%, since most engines cannot run on pure biodiesel without modification. The blend percentage of biodiesel is indicated by a "B" factor. B100 represents pure biodiesel, while blends like B20 contain 20% of biodiesel, with the remainder being traditional petrodiesel. These blends offer a compromise between the environmental benefits of biodiesel and performance characteristics of standard diesel fuel. Biodiesel blends can be used as heating oil.
The environmental impact of biodiesel is complex and varies based on factors like feedstock type, land use changes, and production methods. While it can potentially reduce greenhouse gas emissions compared to fossil fuels, concerns about biodiesel include land use changes, deforestation, and the food vs. fuel debate. The debate centers on the impact of biodiesel production on food prices and availability, as well as its overall carbon footprint. Despite these challenges, biodiesel remains a key component in the global strategy to reduce reliance on fossil fuels and mitigate the impacts of climate change.
Blends
Blends of biodiesel and conventional hydrocarbon-based diesel are most commonly distributed for use in the retail diesel fuel marketplace. Much of the world uses a system known as the "B" factor to state the amount of biodiesel in any fuel mix:- 100% biodiesel is referred to as B100
- 20% biodiesel, 80% petrodiesel is labeled B20
- 10% biodiesel, 90% petrodiesel is labeled B10
- 7% biodiesel, 93% petrodiesel is labeled B7
- 5% biodiesel, 95% petrodiesel is labeled B5
- 2% biodiesel, 98% petrodiesel is labeled B2
- Mixing in tanks at manufacturing point prior to delivery to tanker truck
- Splash mixing in the tanker truck
- In-line mixing, two components arrive at tanker truck simultaneously.
- Metered pump mixing, petroleum diesel and biodiesel meters are set to X total volume.
Technical standards
ASTM D6751 details standards and specifications for biodiesels blended with middle distillate fuels. This specification standard specifies various test methods to be used in the determination of certain properties for biodiesel blends. Some of the tests mentioned include flash point and kinematic viscosity.
Historical background
of a vegetable oil was conducted as early as 1853 by Patrick Duffy, four decades before the first diesel engine became functional. Earlier processes for making lamp oil, were patented but not published in peer-reviewed publications. Rudolf Diesel's prime model, a single iron cylinder with a flywheel at its base, ran on its own power for the first time in Augsburg, Germany, on 10 August 1893 running on nothing but peanut oil. In remembrance of this event, 10 August has been declared "".It is often reported that Diesel designed his engine to run on peanut oil, but this is not the case. Diesel stated in his published papers, "at the Paris Exhibition in 1900 there was shown by the Otto Company a small Diesel engine, which, at the request of the French government ran on arachide oil, and worked so smoothly that only a few people were aware of it. The engine was constructed for using mineral oil, and was then worked on vegetable oil without any alterations being made. The French Government at the time thought of testing the applicability to power production of the Arachide, or earth-nut, which grows in considerable quantities in their African colonies, and can easily be cultivated there." Diesel himself later conducted related tests and appeared supportive of the idea. In a 1912 speech Diesel said, "the use of vegetable oils for engine fuels may seem insignificant today but such oils may become, in the course of time, as important as petroleum and the coal-tar products of the present time."
Despite the widespread use of petroleum-derived diesel fuels, interest in vegetable oils as fuels for internal combustion engines was reported in several countries during the 1920s and 30s and later during World War II. Belgium, France, Italy, the United Kingdom, Portugal, Germany, Brazil, Argentina, Japan and China were reported to have tested and used vegetable oils as diesel fuels during this time. Some operational problems were reported due to the high viscosity of vegetable oils compared to petroleum diesel fuel, which results in poor atomization of the fuel in the fuel spray and often leads to deposits and coking of the injectors, combustion chamber and valves. Attempts to overcome these problems included heating of the vegetable oil, blending it with petroleum-derived diesel fuel or ethanol, pyrolysis and cracking of the oils.
On 31 August 1937, Georges Chavanne of the University of Brussels was granted a patent for a "Procedure for the transformation of vegetable oils for their uses as fuels" Belgian Patent 422,877. This patent described the alcoholysis of vegetable oils using ethanol 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. This is similar to the patented methods used in the 18th century to make lamp-oil, and may be inspired by some old historical oil lamps, in some places.
More recently, in 1977, Brazilian scientist Expedito Parente invented and submitted for patent, the first industrial process for the production of biodiesel. This process is classified as biodiesel by international norms, conferring a "standardized identity and quality. No other proposed biofuel has been validated by the motor industry." As of 2010, Parente's company Tecbio is working with Boeing and NASA to certify bioquerosene, another product produced and patented by the Brazilian scientist.
Research into the use of transesterified sunflower oil, and refining it to diesel fuel standards, was initiated in South Africa in 1979. By 1983, the process for producing fuel-quality, engine-tested biodiesel was completed and published internationally. An Austrian company, Gaskoks, obtained the technology from the South African Agricultural Engineers; the company erected the first biodiesel pilot plant in November 1987, and the first industrial-scale plant in April 1989.
Throughout the 1990s, plants were opened in many European countries, including the Czech Republic, Germany and Sweden. France launched local production of biodiesel fuel from rapeseed oil, which is mixed into regular diesel fuel at a level of 5%, and into the diesel fuel used by some captive fleets at a level of 30%. Renault, Peugeot and other manufacturers have certified truck engines for use with up to that level of partial biodiesel; experiments with 50% biodiesel are underway. During the same period, nations in other parts of the world also saw local production of biodiesel starting up: by 1998, the Austrian Biofuels Institute had identified 21 countries with commercial biodiesel projects. 100% biodiesel is now available at many normal service stations across Europe.
Properties
The color of biodiesel ranges from clear to golden to dark brown, depending on the production method and the feedstock used to make the fuel. This also changes the resulting fuel properties. In general, biodiesel is slightly miscible with water, has a high boiling point and low vapor pressure. The flash point of biodiesel can exceed, significantly higher than that of petroleum diesel which may be as low as. Biodiesel has a density around ~0.88 g/cm3, higher than petrodiesel.The calorific value of biodiesel is about 37.27 MJ/kg. 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 also contains virtually no sulfur and although lacking sulfur compounds that in petrodiesel provide much of the lubricity, it has promising lubricating properties and cetane ratings compared to low sulfur diesel fuels and often serves as an additive to ultra-low-sulfur diesel fuel to aid with lubrication. Biodiesel Fuels with higher lubricity may increase the usable life of high-pressure fuel injection equipment that relies on the fuel for its lubrication. Depending on the engine, this might include high pressure injection pumps, pump injectors and fuel injectors.