Yellow grease

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Yellow grease is a term from the rendering industry. It usually means used frying oils from deep fryers and restaurants' grease traps. It can also refer to lower-quality grades of tallow from rendering plants.

Yellow grease is recovered, traded as a marginally valuable commodity, and has traditionally been used to spray on roads as dust control, or as animal feed additive. But waste restaurant grease has recently become more desirable as one source of biodiesel fuel for cars. Although most biodiesel is developed from renewable plant sources, namely soybeans, yellow grease is attractive because it's cheap, it turns waste into fuel, and the exhaust smells like french fries.

According to a study by Dr. K. Shaine Tyson of the National Renewable Energy Laboratory in Golden, Colorado, the US produces enough yellow grease annually to make 500 million gallons of biodiesel.

"SVO" (straight vegetable oil) refers to any vegetable oil that can fuel diesel engines, but has not been chemically optimzed through transesterification for use in lower temperatures. "WVO" (waste vegetable oil) refers to yellow grease, the kind that comes from restaurants, and usually has to be filtered to remove food particles. Confusingly, yellow grease falls in the category of SVO/WVO, although restaurant waste grease can be assumed to contain beef tallow and other animal products.