2. Key Issues
Biodiesel is an additive to diesel fuel, a mono‐alkyl ester, which is produced when a vegetable oil or animal fat
is chemically reacted (trans esterification) with an alcohol (ethanol/methanol).
Organic fuels derived from plant and animal fats. Mineral fuels derived from decomposed fossil of organic
matter extracted from earth beneath. Everyone knows that the resources of fossil fuel are depleting, and the
cost of extracting the last reserves will become increasingly high. There is an urgent need to find alternative
sources before fossil fuel supplies run dry.
It is also well known that burning of fossil fuels increases the level of carbon‐dioxide in the atmosphere as the
carbon locked within the earth's crust is released by burning into the atmosphere as exhaust gasses. This is
the main cause of the 'Green House' effect in which the overall temperature of the globe increases as it
becomes enveloped within a pool of carbon‐dioxide. This process is thought to be the main cause of global
warming, which is now a well accepted fact even amongst those who were the most skeptical. All the time we
burn normal petrol or mineral diesel we are therefore actively contributing to global warming.
However, the burning of organically derived fuels does not contribute any additional CO2 into the
atmosphere, as the carbon released is the same as the carbon absorbed by the plants as they grow. Using
organic fuels is therefore beneficial to the environment and to the atmosphere.
The Advantages of biodiesel
Biodiesel is the most accepted and widely used biofuel today, in part because of the ability to operate in
standard diesel engines with little or no modifications. Not only is biodiesel environmental friendly
(renewable fuel, biodegradable, non toxic and clean burning‐ reduce CO by 50% and CO2 by 75%,); it also
provides horsepower, torque, and mileage similar to conventional diesel, as well as improved lubricity
(increase in engine life‐time).
3. How It Is Made!
When oil, alcohol, and a catalyst are mixed together, they undergo a chemical reaction, producing two
substances, biodiesel and glycerin. The biodiesel is considered crude biodiesel at this point and contains
trace amounts of glycerin, soap, and extra catalyst and alcohol. It must be cleaned using either water or a
dry‐wash system to remove these impurities.
Transesterification
The process of turning vegetable oil into biodiesel is a chemical reaction called transesterification. This
process occurs when the oil is mixed with an alcohol and a catalyst. The catalyst is simply a substance that
causes the reaction, or the chemical change, to happen faster. Without the catalyst, transesterification
would take too long and not create enough biodiesel to be commercially viable. The catalyst used in
biodiesel production is usually potassium hydroxide (KOH) or sodium hydroxide (NaOH). A chemical
mixture of oil, alcohol, and catalyst is heated in a reactor creating two different layers, glycerin and
biodiesel. There are a few more steps involved, but that is basically it.
4. Biodiesel blends adversely effect material compatibility
1.Biodiesel are electrically conductive > more corrosive (more conductive than gasoline and diesel)
The greater electrical conductivitycan cause galvanic metal corrosionin vulnerable metals copper, bronze,
brass, aluminum, lead, tin, zinc…
2.Biodiesel can oxidize : producing corrosive peroxides
3.Biodiesel is often out‐of‐spec and contaminated with corrosives (off spec contaminants: peroxide,
water, & sulphur)
4.Biodiesel are solvents that can degrade elastomers under specific conditions (volume change may exceed
100 %, hardness and tensile strength may decrease more than 50 %)
5.Biodiesel are more aggressive when water contaminated
Water facilitates electrical conductivity
Water accelerates oxidation
Water often contains other contaminants such as salts ‐‐‐maintain dry tanks and insist on dry fuel
6. Biodiesel are more aggressive in acidic conditions (acids are a byproduct of biodiesel oxidation)
7. Biodiesel is more aggressive with age
5. Materials Compatibility
Biodiesel’s physical properties are similar to those of petroleum diesel, but the fuel significantly reduces
greenhouse gas emissions and toxic air pollutants. It is a biodegradable and cleaner‐burning alternative
to petroleum diesel. Biodiesel can be blended and used in many different concentrations. They include
B100 (pure biodiesel), B20 (20% biodiesel, 80% petroleum diesel), B5 (5% biodiesel, 95% petroleum
diesel), and B2 (2% biodiesel, 98% petroleum diesel). The most common biodiesel blend is B20, which
qualifies for fleet compliance under the Energy Policy Act (EPAct) of 1992.
B100 (pure biodiesel) is not compatible with some metals, elastomers and plastics. B100 will degrade,
soften, or seep through some hoses, gaskets, seals, elastomers, glues, and plastics with prolonged
exposure. Nitrile rubber compounds, polypropylene, polyvinyl, polyethylen, polyamide materials are
particularly vulnerable to B100. In some cases, the vendor may need the chemical family name for
biodiesel (the methyl esters of fats and oils) to look up the information or even the exact chemical
name of some of the biodiesel components, such as methyl oleate, methyl linoleate, methyl palmitate,
or methyl stearate. Oxidized biodiesel and biodiesel blends can contain organic acids and other
compounds that can significantly accelerate elastomer degradation.
Biodiesel will degrade and form high sediment levels if contacted for long periods by copper or copper
containing metals (brass, bronze) or with lead, tin, or zinc (galvanized surfaces). These high sediment
levels may clog filters. B100 may also permeate some common plastics (polyethylene, polypropylene,
polyamide) over time, so these should not be used for storing B100.
6. Study :
PVDF successfully compete with metals and other materials for protection against corrosion in
chemical processing and other demanding environments. Over the life of the unit they decrease
the maintenance and repair expenses for an overall lower cost of ownership.
No change in dimension after immersion No change in weight after immersion
at 40⁰C in biodiesel at 40⁰C in biodiesel
Graphic : PVDF gain is minimal (<0,1%) in Diesel and Biodiesel fuels for a period of 16 weeks
PVDF shows excellent resistance to biodiesel blends. PVDF immersed up to 3000 hrs in biodiesel blends at 40°C,
have seen no loss of physical properties minimal length change and minimal swelling. PVDF repels diesel, biodiesel
and their blends. (Source : www.arkema‐inc.com). Typically plastics materials such as polyethylen will swell in
presence of gasoline and diesel. Long‐term exposure results then in a loss of the mechanical resistance of these
plastics. Because of these fluoropolimers nature PVDF does not absorb diesel and keep its strength and physical
properties.
