Co-processing means running renewable feedstock, such as waste fats and oils, alongside crude oil in the same refinery equipment. The renewable material rides through the existing process together with the crude.
Making renewable fuel normally takes a dedicated plant. Co-processing is a shortcut. A regular oil refinery feeds a share of renewable feedstock, like used cooking oil or vegetable oil, into the same units that process crude oil. The two run through together and come out as finished fuel.
The draw for a refiner is that it can make some renewable fuel without building a separate facility. It uses the equipment it already has, simply adding renewable feedstock to the mix, which is faster and cheaper than starting from scratch.
The catch is measurement. When renewable and crude material are processed together, the finished fuel is a mix, so the refiner has to account for how much of the output counts as renewable. That share is what earns the credits, and getting it measured and documented right is the hard part.
For the fuel trade, co-processing is one way the renewable supply grows, sitting alongside dedicated renewable diesel and SAF plants as a source of lower-carbon fuel.
In useThe refinery co-processes a stream of used cooking oil with its crude, so a measured share of the diesel that comes out counts as renewable and earns credits.
See also Used cooking oil (UCO), Renewable diesel, Biomass-based diesel