Used cooking oil, or UCO, is the waste grease and frying oil collected from restaurants and food plants. In fuel, it is a feedstock, the raw material that gets processed into renewable fuels.
Kitchens go through large amounts of frying oil, and when it is spent it has to go somewhere. UCO is that spent oil, gathered from restaurants, fast-food chains, and food processors by collectors who haul it away. What used to be a disposal headache is now a sought-after raw material.
In the fuel trade UCO is a feedstock, meaning an input to a finished fuel rather than a fuel itself. It is cleaned and then processed into biodiesel, renewable diesel, or sustainable aviation fuel. The oil never goes in a tank as it is; it is the starting point for making the fuel.
Its value comes from being a waste product. Because it was not grown as a crop and would otherwise be thrown out, fuel made from UCO earns a very low carbon score and strong credits under low-carbon fuel programs. That demand has turned waste grease into a traded commodity.
For the broader fuel business, UCO is one of the main feedstocks behind the growth in renewable diesel and SAF, which is why collecting and trading it has become its own industry.
In useA collector picks up used cooking oil from a chain of diners and sells it to a refiner that turns it into renewable diesel.
See also Biomass-based diesel, Renewable diesel, Co-processing