Biofuels promise much, but you must also be aware of the potential pitfalls
by Robert C. Miller Jr
The use of biofuels is increasing all the time. Biofuel is the same as biodiesel, which is commonly a ratio of soybean oil to diesel or heating fuel. Soybean oil is the most commonly used form of biodiesel. The major advantages of biofuels are that the soybean portion if a renewable resource, will reduce dependence on foreign oil and, most important, will reduce emissions (see chart).
As of Oct. 1, 2005, the state of Minnesota enacted a law that all diesel fuel sold in the state will contain no less, but not limited to, 2 percent soy or vegetable oil.
The most common forms of biodiesel, for on-road, off-road or heating oil, are B2, B5 and B20, which are 2 percent, 5 percent and 20 percent soybean oil concentration.
Soybean oil for use in fuels is produced by a process called esterfication via a batch-to-batch process, and each batch varies in terms of quality. The oil from crushed soybeans is filtered, then reacted with sodium hydroxide (common lye, such as you would purchase to clean a drain). It is then rinsed with alcohol and that is the finished product.
Aside from the higher price for biodiesel, everyone is touting its use, but there are many documented and reported problems with its use that you should be aware of so you can deal with potential problems.
Biodiesel is known to act as a detergent when first introduced into existing storage tanks. It will disperse any old sludge that has settled to the bottom of the tank and has caused massive filter-plugging problems. This problem occurs during the first few loads of switching to biodiesel.
Biodiesel, specifically B-20, has 117,000 BTU per gallon of fuel compared to 131,000 BTU per gallon of normal heating oil or diesel fuel. In over-the-road operation, there is a loss of power and the miles per gallon decrease from .5 to 1 mile per gallon.
There is no standard quality control test for the soybean oil producers, so the finished quality varies significantly. There is an ASTM standard for biodiesel, but no standard for the soybean oil itself. We have seen cloudy product and product that drops out of the biodiesel mixture and will only redissolve when heated to 100F. We have also been product that contains excessive alcohol. Excessive alcohol affects the auto-ignition temperature of the fuel and causes very rough running in engines.
Biodiesel wants to absorb water and hold onto it as a milky emulsion which can form ice at cold temperatures and cause operating problems. Water in biodiesel may be in either the emulsion or free form, and in either form, may promote the growth of bacteria and fungi. The bio portion of the fuel is a nutrient for slime and bacteria growths and we have successfully recommended the use of a biocide twice yearly into biofuel tanks to ‘sterilize” the tanks. Bacteria growths ‘blossom” very quickly, and if not controlled has caused massive filter plugging.
The most common form of biodiesel, B20, does not flow very well in cold weather. It will form a thick and cloudy biomass at temperatures around 50F. Some biodiesel suppliers do not recommend its use during the winter months. Most of the existing cold-flow and anti-gel additives do not improve the flow of B20.
Another cause of concern is the compatibility of biofuels with various materials. Some O-rings, seals and gaskets are affected by biofuels. Various hose materials used to dispense biofuels are softened and have failed when in contact with the fuels.
Biofuels degrade about four times faster than diesel fuel or heating oil. In the presence of even small amounts of water, pure biodiesel degrades 80 percent to 85 percent faster than pure fuel alone. Blending biofuels with other fuels accelerates its biodegradability; blends of 20 percent biofuels and 80 percent diesel or home heating fuels degrade twice as fast as No. 2 diesel alone. This aging can be predicted by having an ASTM aging test performed on the fuel.
Destabilized biofuels turn thick, darken in color and plug fuel filters in any application involving filters. Having seen this problem in the field and in laboratory samples, some chemical manufacturers have developed a fuel-storage stabilizer that greatly reduces the aging of biofuels.
We have seen biofuel users have problems when they do their own blending. Users have found that the bio portion that they are adding to a tank of No. 2 diesel or home heating oil must be added on top of the regular fuel to assure good mixing. This type of ‘splash” blending takes advantage of the difference in weight per gallon; soy oil weighs more than diesel or home heating oil.
As with anything new, we tend to hear all the good things, why it is good for the economy, the planet, etc., but we must also be aware of the potential problems so that we can all be better prepared, together.
Robert C. Miller Jr. is a graduate chemist and has been involved with formulating fuel additives for almost 30 years. He can be reached at (973) 226-6316