In the February edition of FleetWatch, our correspondent Max Braun took an overall look at biodiesel and the potential pros and cons of its use as an alternative fuel in the trucking industry. In this, the second and final part of the feature, he discusses some of the side issues and inputs that need to be considered in the overall biodiesel debate. If ever anyone thought of biodiesel as being the easy answer to our environmental woes, think again. The jury is still out on this subject.
QUOTING THE ASIAN Institute of Petroleum Studies, the ideal diesel fuel is 100% normal paraffin which is a fully saturated hydrocarbon which, in turn, means it is totally oxidation stable. As such, it is resistant to oxidation, not prone to bacterial growth, corrosion, rust formation, polymerisation and gumming even without anti-oxidant additives.
Being totally saturated, the ideal diesel is easy to burn, has a high cetane number and produces low NOx emissions. Because most commercial diesel contains a mixture of other elements which are of a lower oxidation characteristic, this means the fuel is a bit more difficult to burn and is prone to a degree of oxidation, bacterial growth, corrosion clogging, etc which results is the deterioration of fuel quality. For this reason, multiadditive packages are made integral to diesel fuel formulation to address the problems mentioned and improve performance parameters of a commercial diesel fuel.
John Deere, one of the world’s largest and well-known manufacturers of agricultural, construction and forestry equipment, estimates the energy content of biodiesel to be about 90% of petroleum diesel provided it is responsibly derived from suitable vegetable oil or animal fats according to published standards such as ASTM D6751 in the US, EN 14214 in the EU and SANS 1935 and SANS 342 in South Africa. Similar standards exist in countries such as Argentina, Brazil, Australia and Asia.
At the time of writing, most of these standards limit approval of biodiesel blends to 5%. The limitation on blends results from engine and fuel injection equipment manufacturers expressing concern in respect of quality control, handling and distribution issues and limited shelf life of biodiesel fuels. Under certain conditions in the US, biodiesel conforming to ASTM D6751 can be used as a 20% blend.
The common European standard for biodiesel, EN 14214, is probably of most interest for South Africa given the number of European vehicles operating in the country. Based on “FAME” (fatty acid methyl esters), this standard prescribes methods of testing the properties of biodiesel. These include: Ester Content, Density, Viscosity, Flash Point, Sulphur Content, Carbon Residue, Cetane Number, Ash and Water Content, Thermal and Oxidation Stability and many other aspects of the finished product.
The South African National Standard for biodiesel used as a 5% blend in conventional diesel, according to SANS 1935:2004 (Edition 1) automotive biodiesel fuel, is based on the technical performance requirements contained in EN 14214. Marc Bataille, manager of Industry Liaison and Vehicle Regulatory Policy at Mercedes-Benz SA Commercial, says: “After blending, the diesel must conform to SANS 342 – automotive diesel fuel.”
Following the rapid increase in biodiesel producers in Germany, the Association for Quality Management of Biodiesel (AGQM) offer a complex quality assurance system applicable to biodiesel producers, trading enterprises, traders, filling stations and additive manufacturers. Their objectives include:
Other aspects of the AGQM quality assurance system lay down parameters to avoid degradation of the product during its useful life. To date the most appropriate feedstock identified by AGQM to guarantee quality fuel, is rapeseed. In Germany, fuel pumps are labelled DIN EN 14214.
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