Two sets of camshafts

Rabbi Tzvi Rosen considers biodiesel in the context of Jewish dietary laws:

In an energy driven world with limited fuel resources, and a public that is totally enamored with its automobiles, industry is constantly looking for inexpensive new sources of alternative fuel. Biodiesel fuel is one answer. Biodiesel is a chemical process that separates vegetable oil or animal fats into two parts: methyl esters — which is another name for biodiesel, and glycerin. The biodiesel is then blended with alcohol to make biodiesel blends that can be used as a substitute for diesel fuel or other fuel substitutes.

Sources of vegetable oil that can be used for biodiesel include rapeseed (canola), soybean and even waste vegetable oil, such as frying oils or trap grease from restaurants, as well as animal fats such as tallow or lard.

Nothing here you didn’t already know. But here’s where I got caught by surprise:

If biodiesel production will skyrocket, and a natural resource of raw material will be spent restaurant oil, vegetable glycerin will have to be even more carefully monitored.

Moreover, of greater kashrus consequence is the potential introduction of naturally produced biodiesel propylene glycol in the marketplace. Propylene glycol has always been assumed to be produced synthetically for commercial use and has been accepted as a kosher ingredient. Propylene glycol has a myriad of uses, as well as endless non-food applications. Although the kashrus status of propylene glycol has never been questioned, propylene glycol can also be produced from glycerin. As biodiesel production grows, thus making the production of propylene glycol from glycerin more economical, this status quo is subject to change.

The pivotal factors, apparently, are where the original fats were obtained and what wound up being fried in them.

(Via Autoblog Green.)

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