Henry Ford, founder of Ford Motor Co., once said: “Quality means doing it right when no one is looking.” He understood that consumers expect a quality product and that quality is the key to customer satisfaction. It is no different with biodiesel.
ASTM International, originally known as the American Society for Testing and Materials, develops technical standards for many products and services including biodiesel. The standards for biodiesel performance are outlined in ASTM specification number D6751. Biodiesel producers must meet these specifications as a minimum standard of performance, but there is more to the story.
When product quality is taken seriously, biodiesel producers strive to produce a product that exceeds ASTM standards. Meeting a minimum standard isn’t good enough. While some biodiesel performance characteristics are a result of the feedstock used, others can be improved during the production process. Consider the following examples:
The percent mass of total glycerin to meet ASTM D6751 is .24 of a percent maximum. But for best performance, this number must be considerably lower. Lower total glycerin and more importantly, lower monoglyceride content, means fewer plugged filters and better cold temperature storage characteristics.
The percent volume of water and sediment to meet ASTM D6751 is .05 of a percent maximum, but good suppliers aim for half that amount. Biodiesel is extremely absorbent and can absorb much more water than conventional diesel fuel. Excessive water in the fuel is the No. 1 cause of filter plugging in biodiesel blends. The lower the water content, the better the performance.
The cold soak filterability test is a recent addition to the D6751 specifications, but it has proved to be an important tool for preventing unexpected filter plugging. The test is intended to detect any components of the biodiesel that may precipitate out of suspension when exposed to long periods of cold temperature.
The test requires biodiesel to be cooled in a 40 degrees Fahrenheit bath for 16 hours. It is then warmed to ambient temperature. The biodiesel is required to pass through a 0.8 micron filter in less than 360 seconds (winter) or 200 seconds (summer). A lower filtration time indicates better performance.
When it comes to using biodiesel blends or storing them successfully for a period of time, it is essential to use a quality biodiesel blend that not only meets but exceeds ASTM standards.
For additional information and assistance in determining biodiesel quality, contact your local FS energy salesperson.
Brigette Harlan is GROWMARK’s renewable fuels product manager. Her e-mail address is firstname.lastname@example.org