What the FOG: What’s the difference between brown and yellow grease?

Yellow grease, used cooking oil, UCO

Welcome to What the FOG, a new section of The SwiftComply Blog dedicated to all things concerning fat, oil and grease — from what is FOG, to how it can play a key role as a sustainable material. In this post, we cover a question that is often asked by food businesses: “What is the difference between FOG and used cooking oil?”

What is FOG?

Let’s start with the easy one: fat, oil and grease is a byproduct of food production. If there is any food prep, cooking or cleaning carried out in the kitchen, then chances are you are producing FOG.

Dave Gibbons, Head of Knowledge at SwiftComply, explains: “Dairy produces it, meat, pizza (there’s lots of oil in the dough), as well as salad dressings and coffee beans. If you roll a piece of paper over a piece of food, you’re probably leaving some kind of fatty residue on it. When you wash that into a sink, it creates a problem.”

Yellow grease

Used cooking oil, or UCO, is what the industry calls yellow grease. UCO is exactly what it says on the tin – oil that has been used and is no longer good for cooking with. This oil is typically captured from deep fat and chip fryers, then stored in a container or barrel to be collected by a waste contractor for recycling.

Restaurants usually sign up for a deliver-new-oil, collect-old-oil system, and because this material is homogenous, it is relatively the same throughout. In other words, if you extract used cooking oil from two restaurants located in different parts of a city, you will find a very similar product in both.

Brown grease

This is the FOG waste collected from grease control devices (GCDs), more typically known as grease traps. A GCD will collect fat, oil and grease at source and prevent it from entering the sewers.

Compared to UCO, brown grease is more challenging to collect without the right equipment. Grease traps or any other form of GCD should be used to effectively trap and retrieve it. And unlike the yellow grease, depending on the restaurant’s menu, this waste resource will differ from place to place in terms of physical product (and even smell).

In summary…

To recap, yellow grease is the same as used cooking oil (or UCO). It is relatively easy to collect it and food businesses usually can avail of exchange schemes where a contractor will come collect the old product for recycling and leave a new one to be used by the establishment.

Brown grease is commonly called FOG – which stands for fat, oil and grease. This material is present in the food preparation as well as in cleaning procedures. The only way to effectively capture it is by having grease control devices installed in the kitchen’s discharging points.

Despite the differences, these products have two important things in common. The first is that they are both highly polluting and therefore, should not end up in sewers or landfills. Secondly, both are waste resources and not waste, meaning there is great potential for recycling and reusing them – something that we will talk about soon here at What the FOG.

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