The environmental and cost benefits of biodiesel fuel depend upon its properties. In turn, these properties are largely determined by the way in which this new energy source is produced and stored. Thus, producers, distributors and retailers can ensure the quality of their product by following the specifications presented by the American Society for Testing and Materials (ASTM).

The guidelines, within the ASTM specifications, place limitations upon various properties. While space constraints make an exhaustive discussion of these properties impossible, this article will discuss the reasons why maximum and/or minimum limits are placed on four of the characteristics of the fuel.

One important characteristic is the flash point. The flash point is the lowest temperature for which combustion may occur. If the flash point is too low, then inadvertent combustion may occur resulting in a safety hazard. According to some sources, one way of raising the flash point and reducing the risk of accidental ignition is to increase the percentage of biodiesel within a blend. However, a low flash point can also result from small amounts of methanol left over from the conversion process. Therefore, producers should always biodiesel fuel tests upon the flash point to ensure the safety of distributors, retailers and consumers.

While the amount of water and sediment does not pose any safety concerns, the presence of these contaminant materials has undesirable mechanical implications. In particular, water and sediment can clog filters, reduce ignition performance and have a negative impact upon the fuel pump. Specifications, set by the ASTM, refer to the amount of water dissolved and not to the water coexisting in bulk form alongside the fuel within a tank. Nonetheless, the state of Michigan also places constraints on the amount of such bulk water within a storage tank.

The presence of water may also stimulate the growth of microbes. This is especially true for warmer temperatures. The microbes produce deposits that can add to the clogging effects of the water upon filters. This only further underscores the importance of testing for water.

The final property that will be discussed is the glycerin content. Glycerin is a natural byproduct of the production process. A large glycerin concentration in the final product may signal that the process used to transform oils and fats into fatty acid methyl esters (FAME) was not completed. A high glycerin concentration may result in the clogging of filters and pumps as well as the contamination of injectors.

Performing biodiesel fuel tests upon the four characteristics discussed within this article, as well as other properties not discussed here, can help to increase the safety of consumers and increase engine performance while reducing emissions.