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Analytical Instrumentation
The Cutting Edge Advances in Worldwide Biodiesel Testing Specifications and Standardisation
Dr. Raj Shah and Michaelle Exhume 1595 Sycamore Ave, Bohemia, NY 11716, USA Tel: 001 6315893800 • Email:
rshah@koehlerinstrument.com • Web
www.koehlerinstrument.com
Dr. Raj Shah Michaelle Exhume
Te search for alternatives to replace fossil fuel based energy sources has contributed to the development of fuels from various sources which include renewable feedstock such as fats and oils. Several types of fuels can be derived from this triglyceride-containing feedstock. Biodiesel is one of the most sought after forms of alternative fuel in the industry. Tis fuel can be made from various resources including agricultural oils, recycled cooking oil and animal fat; the diversity of this mix is increasing every day. Due to the increasing prices of petroleum, biofuels are gradually becoming more prevalent
worldwide. Accordingly, biodiesel standards have been established and continue to be developed in regions like the United States, Europe, Brazil, South Africa and elsewhere. Tis article cites the specifications and standards pertaining to testing biodiesel in particular regions around the world.
The primary motivation behind biofuels as an alternative source of energy stems from the world’s increasing demand for energy. With depleting fossil fuel sources, fears of global warming and for many, the intent to decrease the dependence on fuel imports, biodiesel is becoming more and more prelevant in the fuel industry as an alternative. Petroleum caught on early as the primary source of energy because it was plentiful and relatively inexpensive to refine. Currently, biodiesel is one of the most sought after fuel alternatives due to its biodegradability and low emission profile. The ultimate goal is to one day replace petro fuels with bio-based fuels. These days however, biodiesel is primarily used as a blend with petrodiesel.
The concept of bio-based fuels is not as new as one may think. A bio-based fuel was first used in 1895 by the German engineer Rudolf Diesel who invented the first engine that ran on vegetable oil. Due to the lack of interest in this alternative fuel in his days, the idea did not flourish. Nowadays, Biodiesel can be blended and used in many different concentrations1, these include: B100 (pure biodiesel), B20 (20% biodiesel, 80% petrodiesel), B5 (5% biodiesel, 95% petrodiesel) and B2 (2% biodiesel, 98% petrodiesel). The most common blend currently used in the United States is B20.
As we consider B100 to one day fully replace petrodiesel, some key differences are to be cited. Diesel is obtained through distillation of crude oil to separate lighter and heavier components, whereas biodiesel is obtained by chemically reacting lipids with an alcohol. Biodiesel is made up of a combination of esters of different fatty acids whereas diesel contains a broad range of hydrocarbons. Their different compositions pose a number of issues; biodiesel may contain heavy materials which would thermally decompose when exposed to heat in a working engine. A large number of unsaturated carbons are found in biodiesel whereas crude oil contains few olefins which would not cause instability and contribute to degradations. The presence of oxygen in biodiesel is an advantage because it allows for a more complete combustion which results in lower emissions, but it also negatively affects the performance of the engine by slightly reducing its peak power.
Biodiesel is obtained by reacting lipids with an alcohol to produce fatty acid esters through a process known as transesterification of vegetable fats and oils with glycerin as a co-product (figure 1). This fuel has steadily been gaining interest in the industry due the increasing price of petroleum. With the increasing interest and use, the successful commercialisation and market acceptance of biodiesel has become a major focus of the market.
Accordingly, biodiesel standards have been established or are being developed in various countries and regions around the world, which include the United States, Europe, Brazil, South Africa and elsewhere. This article cites the specifications for testing in the biodiesel industry. Due to the different emerging biofuel economies, one of the main issues facing the alternative fuels industry is the international compatibility of testing standards.
ASTM International has recently published new specifications for a broader range of Biodiesel Blends. Advancements in other bio- or alternative energy technology have widened the scope of what we see as feasible solutions to our energy problems. These developments and advances are a positive sign for the alternative fuels industry.
Standardisation is however not the only issue which is to be dealt with as this fuel’s usage becomes more common. Issues dealing with the use of vegetable oil as feedstock and its relatively high costs are also to be considered. This is primarily due to the availability of vegetable oil in that it will always have uses, such as food rather than to be used as an energy source. Only a fraction of vegetable oil production is available for non-food use. It is unlikely that this problem should be solved by merely producing more vegetable oil to use for fuel due to the lack of land and other natural limitations.
ASTM D6751, Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels, was first developed in 1999 as Provisional Specification, PS121-99 by the American Society
Figure 1: Transesterification Process2
ASTM D6751 highlights specifications dealing with the physical and chemical characteristics that ensure safe and adequate operation of diesel engines. It does not consider the feedstock or refining process used in the production of the fuel. The fuel’s final blend stock simply must meet these required conditions (Table 1). The content of Magnesium (Mg) and Calcium Combined in biodiesel is limited because these metals can form harmful deposits that damage emission control equipment. One of the most vital physical properties to be measured is the Flash Point of the product. The standard minimum set for pure biodiesel is 93°C; this is to make certain that it is classified as “nonhazardous under the National Fire Protection Association”(2).
There are two specifications stated under alcohol content in the fuel of which only one has to be met. The first pertains to the flash point to ensure that it isn’t affected by the methanol presence from the manufacturing process; this minimum is set to a value of 130 °C. The other is based on the amount of methanol present which shall be reduced to a maximum of 0.2 vol %. During the manufacturing process, both Gas Chromatography (GC) and High Performance Liquid Chromatography (HPLC) can be used for analysis of ester content. Their presence can lead to operational problems such as engine deposits, filter clogging or fuel deterioration5.
AUGUST / SEPTEMBER 2013 •
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for Testing and Materials (ASTM). It was adopted as a standard in 2002 as D6751-02; since then several revisions have been made and its latest form stands as ASTM D6751-11a. This test method is used as a basis for several other standards for biodiesel. Another standard prevalently used as a reference to other methods is the European method, EN14214.
The European standard EN14214 (table 2) is broadly based on DIN 51606. This standard outlines the requirements and test methods for fatty acid methy esters (FAME) to be used as automotive fuel for diesel engines at concentrations of up to 100% or as an “extender” for these engines as specified by EN 590.
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