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Magazines & Newsletters / ASTM Standardization News

feature

January/February 2008
Feature

Why Is a Measurement System for Biodiesels So Necessary?

Biodiesel has distinct advantages over petroleum diesel. It also has some potential disadvantages.

The esters in biodiesel are more biologically active than the alkanes and alkenes in petroleum diesel. Especially if enough moisture is left in it after the refining process, biodiesel can break down into acetic acid, a corrosion hazard. This relates to stability issues — how long can you store biodiesel, say, in your home heating tank, before it causes problems?

Then there’s flammability. Methanol, the most common reagent used to break triglycerides into esters, is highly flammable. If some amount is left in the final product, the final product could be flammable.

Add the fact that biodiesel, especially biodiesel derived from animal fat, congeals at a higher temperature than petroleum diesel. In regions that regularly experience below-freezing temperatures, kerosene is added to petroleum diesel to prevent congealing problems, but how might kerosene — or another antidote — affect the performance of biodiesel?

Then there are regulatory issues. In the U.S., the 50 states set individual requirements for sulfur content and perform weights-and-measures services that guarantee consumers that the fuel they purchase meets certain specifications. With mom and pop operations delivering biodiesel to tank farms for blending into petroleum diesel, how can state agencies guarantee that what comes out of the service station nozzle meets established specifications?

All of these variables can be controlled by maintaining optimum specifications, and maintaining specifications relies on metrology and on laboratories having the technical tools to apply that metrology.