Bio-diesel Fuel. Is it the Right Choice?
While all of us are aware that we need to take better care of our planet by reducing vehicle emissions, making the switch to biofuels may not be the right choice.
It is human nature (or maybe male nature) to want to continually increase engine performance and reduce exhaust emissions, however, these improvements mean we must also develop new generations of diesel fuel injection systems that meet government legislated emissions targets. Handling the rising injection pressures and multiple injection events that are the result of Increased performance results in higher operating temperatures, increased pressures and reduced clearances. Maintaining these critical tolerances requires a minimum standard of fuel quality, both to meet emissions compliance requirements and ensure a long vehicle service life.
While you many not think so, diesel fuel injection system manufacturers actually support the development of alternative fuel sources. Engineers have designed biodiesel compatible components, however, many vehicles, engines and equipment just are not designed to run on alternative fuels.
Becoming increasingly available to end-users, Biofuels in Canada, Europe and the United States comes from sources such as rapeseed methyl ester (RME), soybean methyl ester (SME), palm oil methyl ester (PME) and others. These are collectively known as fatty acid methyl esters or FAME. FAME fuel sources are currently being used as alternatives and ‘extenders’ to add to fuels derived from mineral oil.
It’s imperative to understand that the chemical and physical characteristics of biofuel components are drastically different when compared to conventional fuels. Here are some important points to consider:
FAME Stability
The long-term stability of FAME is a big concern. FAME that has aged or is of poor quality contains organic acids, such as formic acid) and polymerization products. These acids attack the various engine components while the polymers can plug filters; thereby creating sediments and stickiness in moving parts which drastically reduces the service life of the fuel injection system components.
FAME Impurities
With an increasing number of feedstocks being used to create FAME, there are several uncertainties associated with unknown impurities that may not become evident until the vehicle is in operation. The minor components of FAME are of further concern as their high molecular weight can lead to filter plugging. Additionally, FAME additives can interact with the various chemistries, creating undesirable results.
FAME Compatibility
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 standstill 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 which means that it readily absorbs water from the moisture in the air. Water contamination in one of the biggest concerns with diesel as it leads to the corrosion of the steel components in the fuel injection system, as well as it promotes microbial growth in the fuel tanks. Water contamination is very common in bio-diesel as the fuel absorbs water at x100 the rate of regular mineral-based diesel. That is why it is critical to install a water-separator fuel filter to remove contamination before the fuel enters the fuel system.
Microbial Growth
Naturally occurring in diesel, microbial growths can form a layer of organic debris that sticks to the walls and the bottom of the fuel tank or storage container) over time, or as the fuel ages. These growths survive and thrive by living in or around the water line to feed on the rich hydrocarbons present in the asphaltene layer of the fuel. This growth process can be accelerated by adding fresh fuel to contaminated fuel. When these growths break away from the sides of the tank, they float freely, leading to clogged fuel lines or filters.
Oxidation and Re-polymerization
These terms refer to the natural processes that lengthen and bond the diesel molecules to produce varnishes and insoluble gums. When these particles drop to the bottom of the tank they form asphaltenes, or diesel sludge.
The North American standards for bio-diesel (B0 to B5) does not specify mandatory stability requirements, nor do the standards for B6 to B20 blends (and for pure FAME) include sufficient stability safeguards.
While modern fuel injection equipment manufacturers support the use of bio-diesel, they do not agree with the use of unesterified plant oil (waste veggie oil – WVO), even when this fuel meets existing national standards.
We say all that to say: we know that you CAN run your diesel engine on bio-fuel, but we also know there are many of caveats to be aware of. Let’s take a look at the pros and cons:
- THE PROs
- • Abundant lubricity
• A reduction in emissions
- THE CONs
- • Poor long-term fuel storage stability
• High water absorption rate increases algae growth
• Reactions and/or distortions from gaskets and seals
• Lower BTU’s of energy are generated with bio-fuels
• Organic acids may attack diesel fuel engine components
• A water-separator fuel filter is required
• An increase in fuel filter changes
When you factor in all of these variables you have to ask yourself if you are actually reducing your carbon footprint? Or, will you just end up spending more money on maintenance on a vehicle that is not as reliable as it could be?
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