The grease economy

The drawing is the whole argument. Kitchen fat moves in a loop, from a fryer or a trap, through a collector, to a plant that makes fuel, feed ingredients, or chemicals, and the money moves back toward the kitchen as a pickup service or a payment for oil. Lubricating grease is not in that loop. It is manufactured for bearings and fittings and thrown out as a spent shop waste, not rendered into yellow grease.

Start with the fryer. Oil that is finished for cooking is still a fat. Held in a closed tank, free of wash water, it is used cooking oil. Collectors sell it as yellow grease when it meets a spec for free fatty acids and for moisture and impurities. Biofuel plants hydrotreat it into renewable diesel or jet-fuel blendstock, or they make biodiesel. Other buyers use it in feed and in oleochemicals where the rules allow. The kitchen's lever is quality. Water and crumbs are the discount.

The interceptor is the second loop. It catches the fat that would have gone to the sewer. A pumper hauls a watery load. A plant recovers brown grease, a lower grade than yellow grease, and the rest is waste. Cities require this loop because fat hardens in municipal pipes. A restaurant that skips the pump-out breaks the loop and shifts the cost onto the sewer. Probiotics and drain chemicals do not close it. A truck and a manifest do.

Choice white grease is the animal-fat loop, mostly pork, graded by hardness and color. It is easy to confuse with white lithium grease, which is a machine lubricant, and with the pale oil in a fryer. The drawing only works if those names stay attached to the right loop. Prices, when they appear on this site, are historical hundredweight quotes for the commodity loops, not prices for a grease cartridge.

GREASE.ORG sits on the kitchen side of the picture. The company picks up used cooking oil and services grease traps and kitchen drains. It does not operate the hydrotreater and it does not publish a daily commodity bid. Use the drawing to see which stream you have. Then use the cooking-oil page, the trap page, or the lubricant page, and do not cross the streams.