Should I Run my Car on Biodiesel?
Everyone wants to do their part to reduce emissions and help save the world – a noble idea.
The world-wide tendency to increase engine performance and reduce exhaust emissions has lead to the development of new generations of diesel fuel injection systems to help achieve the government legislated emissions targets. Handling the rising injection pressures and multiple injection events results in higher operating temperatures, increased operating pressures and reduced clearances. To maintain these critical tolerances, a minimum standard of fuel quality is essential to achieve emission compliance and ensure reliable operation of your diesel engine over a long service life.
Diesel fuel injection equipment manufacturers certainly support the development of alternative sources of fuel. Wherever possible, engineers have designed compatible components that were developed, provided and validated for use with bio-diesel fuels. However – many vehicles, engines and equipment simply are not designed to run on alternative fuels.
Biofuels are becoming increasingly available to end-users. In Europe, Canada and the United States, fuel sources such as rapeseed methyl ester (RME), soybean methyl ester (SME), palm oil methyl ester (PME) and others, are collectively known as fatty acid methyl esters (FAME). These FAME fuel sources are being used as alternatives and ‘extenders’ to add to mineral oil derived fuels.
It must be recognized that the physical and chemical characteristics of bio components are significantly different to conventional fuels and that care must be taken in their use.
Long term stability of FAME is of a particular concern. Aged or poor quality FAME contains organic acids (like formic acid) and polymerization products. These acids attack many engine components, and the polymers can lead to plugged filters, creating sediments and stickiness to moving parts drastically reducing the service life of the fuel system components.
Issues may occur on older vehicles designed before the use of FAME was considered. As FAME concentrations increase, there are compatibility issues that create headaches like filters, hoses, gaskets and seals being the most commonly affected components often swelling or distorting in reaction.
Bio-diesel fuel does not like long stand-still periods. This warning is aimed directly at seasonally operated equipment like harvesters or emergency generators, vehicles being exported to overseas, etc. For this reason FAME-free fuel is highly recommended for “first fill” or extended periods of inactivity.
Bio-diesel is Hygroscopic
Diesel fuel is highly hygroscopic, meaning it readily absorbs water from moisture in the air. Water contamination in diesel fuel is a major concern as it leads to the corrosion of steel components and the promotion of microbial growth in the fuel tanks. Water contamination of bio-diesel is very common and bio-diesel absorbs water at x100 the rate of regular mineral based diesel. For this reason, it is critical that a water-separator fuel filter be installed to remove water contamination before the fuel enters the fuel system.
Microbial growths that naturally occur in diesel can form a layer of organic debris that adheres to the walls and bottom of the fuel tank or storage container as the fuel ages. These growths survive and flourish by living in or around the water line and feeding on the rich hydrocarbons present in the asphaltene layer of the fuel. Adding fresh fuel to a contaminated fuel supply accelerates the development of these growths. Growths that break away from the sides and float freely in the fuel can unexpectedly clog fuel lines or filters.
Re-polymerization and Oxidation: These are natural processes by which the diesel molecules lengthen and bond to produce varnishes and insoluble gums. These particles then drop to the bottom of the tank to form asphaltenes (also known as diesel sludge).
North American standards for bio-diesel (B0 to B5) does not contain any mandatory stability requirements, and the standards for B6 to B20 blends (and for pure FAME) do not include sufficient stability safeguards.
Modern fuel injection equipment manufacturers do not agree with the use of unresterified plant oil (waste veggie oil – WVO), even where such fuel meets existing national standards.