Used cooking oil follows a four-step supply chain: collection from restaurants, aggregation and basic processing, refining into commodity-grade yellow grease, and final conversion into fuels (primarily renewable diesel and SAF), animal feed, or oleochemicals. The majority of UCO collected in North America now ends up in fuel production.
Step 1: Collection
The journey starts in your kitchen. A collection truck arrives on a scheduled route, the driver pumps the oil from your storage container into the truck's holding tank, and the load moves to an aggregation point — typically a yard or depot operated by the collection company.
Collection companies range in size from single-truck local operators to national fleets with thousands of trucks. The biggest names — Darling Ingredients, Baker Commodities, Restaurant Technologies — operate at national scale, while hundreds of regional and local operators serve specific metro areas.
Step 2: Aggregation and basic processing
At the aggregation yard, oil from many restaurants is consolidated, allowed to settle (so water and solids sink), and transferred to heated bulk storage tanks. Some basic processing happens here: heavy water and solids are removed, the oil is warmed to allow consistent pumping, and samples are tested for quality.
At this stage, collectors often sell by the truckload (6,500 to 9,000 gallons) to larger aggregators or directly to rendering companies. The price they receive depends on the quality of the oil — specifically its FFA content and MIU (moisture, insolubles, unsaponifiables) measurement.
Step 3: Rendering and refining
The next stop is a rendering or pre-processing facility. Renderers — think Darling Ingredients, Baker Commodities, Mahoney Environmental, and similar firms — operate industrial plants that take raw collected oil and refine it into a standardized commodity product.
The process typically involves:
- Heating to break up emulsions and allow water separation.
- Centrifugation or filtration to remove fine particulates.
- Chemical treatment in some cases to reduce FFA content.
- Testing to confirm the finished product meets yellow grease commodity specifications.
The output is commodity-grade yellow grease, a tradeable product with published market prices. From here, it gets sold into end-user markets.
Step 4: Final use
Yellow grease has several end uses, but the balance among them has shifted dramatically in recent years.
Renewable diesel (largest use today)
Renewable diesel is produced through a hydrogenation process that converts fats and oils directly into a fuel that is chemically identical to petroleum diesel. Major producers — Neste, Diamond Green Diesel (a Valero/Darling joint venture), World Energy — consume massive quantities of UCO-derived yellow grease. Renewable diesel now represents the largest single end-use category for UCO in North America.
Sustainable aviation fuel (SAF)
A growing share of UCO goes into sustainable aviation fuel. The process is similar to renewable diesel production but produces a jet-grade fuel. Airlines facing emissions targets — driven by programs like CORSIA internationally and state mandates in the U.S. — have committed to blending SAF into their fuel purchases, and UCO is one of the preferred feedstocks.
Biodiesel
Biodiesel is a distinct product from renewable diesel — it is produced through transesterification rather than hydrogenation, and the resulting fuel blends with conventional diesel but is not chemically identical to it. Biodiesel was the original major outlet for UCO and still represents a significant share.
Animal feed
Before the fuel boom, animal feed was the largest market for yellow grease. It is still a meaningful outlet — yellow grease is added to feed rations for energy content. Pet food manufacturers are also buyers. However, because fuel buyers typically pay more, this market has shrunk relative to the fuel markets.
Oleochemicals and industrial uses
A smaller slice goes into soap manufacturing, industrial lubricants, personal care products, and similar industrial applications. These are specialty markets that can pay premium prices for specific oil properties.
Where geography enters the picture
North American UCO is increasingly destined for North American refineries, but a substantial portion also goes to export markets — particularly Europe, where mandates on waste-derived fuels (double-counting under RED III) drive up prices. Asia is an emerging buyer, with Singapore's new SAF mandate pulling additional volume eastward.
The policy environment has shifted recently to favor domestic use: the 45Z tax credit in the U.S. effectively rewards fuels made from domestically-collected feedstock, pulling more UCO into North American refineries and out of export channels.
Key takeaway
Your restaurant's used cooking oil travels through a four-step supply chain — collection, aggregation, refining, end use — and most of it today ends up as renewable diesel or sustainable aviation fuel. This supply chain is the reason UCO has become meaningfully valuable over the last several years, and why restaurant operators have more negotiating power than they used to.