Main attributes of biodiesel
Renewable resource - Biodiesel is derived from vegetable oil, used cooking oils and animal tallow. These feedstocks can be produced indefinitely, using sustainable farming techniques to provide an environmentally friendly, sustainable fuel.
Widely used and accepted - Biodiesel is a proven fuel with an extensive history in the US and wide usage in Europe.
Carbon neutrality – Plants absorb CO2 from the atmosphere and store the carbon primarily in the form of carbohydrates and oils. By using vegetable oils as a raw material, biodiesel recycles carbon through the biosphere, allowing a significant reduction in carbon emissions when compared to traditional sources of energy.
What is biodiesel
Biodiesel is a clean burning fuel made from vegetable oil or animal fats. It can be used in modern compression-ignition (diesel) engines without requiring any engine modifications. Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel blend. Biodiesel is simple to use, biodegradable, non-toxic, carbon neutral and is essentially free of sulphur and aromatics.
How is it produced
Vegetable oils and animal fats consist of a glycerine molecule, with three ‘fatty acid’ molecules attached to it. Biodiesel is made through a process called transesterification whereby the glycerine is separated from the fatty acids. The process leaves behind two products - biodiesel (Mono-alkyl ester) and glycerine
(a by-product used in soaps and other products).
 The process of manufacturing biodiesel is relatively simple. The feedstock oil is mixed with methanol and a catalyst (NaOH or KOH) to produce a reaction that creates biodiesel and glycerine. Applying heat and pressure to the reaction decreases the processing time. The Glycerine fraction is heavier than the biodiesel, allowing it to separate out naturally after the reaction. Ethanol can be used instead of methanol for biodiesel production, however the reaction is less predictable.
Advantages of biodiesel
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Renewable - vegetable oil derived fuel
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Potential for Carbon Neutral lifecycle
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Simple to make
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Non-toxic
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Biodiesel is free from sulphur (< 0,001 %)
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The only alternative fuel that does not require engine modification or retuning
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Safer for storage and handling than petroleum diesel
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Can be used neat or blended in any ratio with
petroleum diesel
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Biodegradable
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Higher Lubricity - can prolong engine life
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Dramatically reduced emissions
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High flashpoint
Operational benefits
Emissions
The lifecycle production and use of biodiesel produces approximately 80% less carbon dioxide emissions, and almost 100% less sulphur dioxide than mineral diesel. Combustion of biodiesel alone provides over a 90% reduction in total unburned hydrocarbons, and a 75-90% reduction in aromatic hydrocarbons. Biodiesel further provides significant reductions in particulates and carbon monoxide than petroleum diesel fuel. Biodiesel produces either a slight increase or a slight decrease in nitrogen oxides, depending on engine design and testing procedures. Based on Ames Mutagenicity tests, biodiesel provides a 90% reduction in cancer risk over mineral diesel.
Sulphur emissions
Biodiesel contains almost no sulphur at all (max. 0.001%).
This gives rise to the following advantages:
- during combustion no sulphur dioxide is generated.
SO2 is one of the main substances blamed for acid rain.
- during combustion no sulphate is produced.
The amount of particles in exhaust fumes is drastically reduced.
- the motor oil is less laden with acidic residue of combustion.
- catalysts can easily be adjusted to sulphur-free fuel.
Catalyst poisoning is reduced and the service lifetime is significantly prolonged
Cetane rating
Cetane is a measurement of how quickly the fuel burns- higher cetane ratings indicate a faster, more efficient ignition of the fuel. To meet the Australian standard, biodiesel must have a cetane rating of at least 51, whereas mineral diesel is only 47. The cetane rating of biodiesel is usually 55-65, so meeting this standard is not a problem for producers.
Oxygenated fuel
Oxygenated fuels provide significant improvements to combustion characteristics and emissions. Petroleum companies artificially oxygenate their premium fuel products for this reason. However, biodiesel naturally contains between 6-12% oxygen (depending on the type of feedstock oil) which improves combustion efficiency and significantly reduces emissions, particularly the soot emissions that are normally associated with diesel engines.
Power and torque
In field tests for over 15 million driven miles, biodiesel shows fuel consumption, power and torque similar to mineral diesel. Due to the oxygen content of the fuel it has a slightly lower specific energy content, however, this is offset by better combustion properties to provide a fuel that is, in most instances, equivalent to mineral diesel.
Lubricating properties
Biodiesel has much better lubrication properties than mineral diesel. The lubricity of mineral diesel can be improved by blending in relatively small amounts biodiesel, preventing the need for lubricity additives which are normally required in mineral diesel products.
Odour
Biodiesel generally smells like vegetable oil, and has none of the strong vapours that are associated with petroleum products. When using 100% biodiesel in a diesel engine, the exhaust odour reflects the feedstock that was used for production. For example, biodiesel made from used cooking oil usually smells like hot chips, which is far more pleasant for pedestrians and cyclists than the smell of mineral diesel.
Environment and safety information
Toxicity
Biodiesel is non-toxic. Biodiesel is the only alternative fuel in the US to complete EPA Tier I Health Effects Testing under section 211(b) of the Clean Air Act, which provide the most thorough inventory of environmental and human health effects attributes that current technology will allow. The acute oral LD50 (deadly doses for 50% of all test animals) is larger then 17.4g/kg bodyweight. The LD50 for table salt (NaCl) 3-4g/kg of bodyweight, indicating that biodiesel is approximately 5 times less toxic than salt.
Skin irritation for human beings
A 24 hour testing shows undiluted Biodiesel producing fewer skin irritations when compared to 4% lye of dissolved soap in water.
Flash point
Flash point is measured in degrees at that point, when open fire or sparks ignite a certain matter. Biodiesels' flash point is at 200°C much higher (therefore safer) when compared to mineral diesels' 70°C. Thus, storage, transport and handling of Biodiesel are cheaper and less dangerous than mineral diesel.
Biological degradability
Biodiesel degrades about 4 times faster than mineral diesel. Within 28 days pure biodiesel solved in water will be degraded by 85 to 88 per cent - which is exactly the same value as dextrose. Blending biodiesel with conventional mineral diesel enhances degradability of mineral diesel significantly. For example B20 (20% Bio-, 80% Mineral diesel) is degraded 2x faster than B100
(100% mineral diesel).
Water poisoning
Deadly doses of Biodiesel on basis of bluegill in 96 hours of testing was larger than 1000 mg/l. Deadly doses of this kind and at this level are rated by the NIOSH (National Institute of Safety and Health) as "generally not harmful”.
What vehicles / equipment can use biodiesel
Biodiesel is the only alternative fuel that runs in any conventional, unmodified diesel engine. It can be stored anywhere that petroleum diesel fuel is stored. Biodiesel can be used alone or mixed in any ratio with petroleum diesel fuel. The most common blend is a mix of 20% biodiesel with 80% petroleum diesel, or "B20."
The politics of car producers are different, e.g., all European production models since production year 1996 are fully equipped and rated for biodiesel use. There is a directory with vehicles that have the manufactures permission to use Biodiesel:
http://www.ufop.de/downloads/Freigaben20060927_en.pdf
Use in engines
In general, biodiesel will soften and degrade certain types of elastomers and natural rubber compounds over time. Using high percent blends can impact fuel system components (primarily fuel hoses and fuel pump seals), that contain elastomer compounds which are incompatible with biodiesel. Manufacturers recommend that natural or butyl rubbers not be allowed to come in contact with pure biodiesel. Biodiesel may lead to degradation of these materials over time, although the effect is lessened with biodiesel blends. If a fuel system does contain these materials and user’s wish to fuel with pure biodiesel, replacement with compatible elastomers is recommended. The recent switch to low sulphur diesel fuel has caused many OEMs to switch to components suitable for use with biodiesel, but users should contact their OEM for specific information.
Biodiesel has a solvent effect that may initially release deposits accumulated on tank walls and pipes from previous mineral diesel fuel storage. The release of deposits may clog filters and it is generally recommended to change filters after initial use of biodiesel. Depending on the age and condition of the fuel system the filter may have to be changed several times in the first 15,000km of use after the transition to biodiesel.
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