What is it, who needs it and how to get it
DCO: Distiller's corn oil
Ethanol production from starch-based feedstocks like corn and wheat, creates tons of stillage which can be used in animal feed, preferably as dried distiller’s grain with solubles (DDGS).
If corn is used as feedstock the stillage also contains oil that can be obtained with centrifuges to get the most out of your raw material and process.
What is Distiller’s Corn Oil (DCO)?
Distiller’s corn oil (DCO) is a valuable co-product from dry milling ethanol production, a common method in bioethanol production across the U.S. and India. Extracted post-fermentation from stillage, it is used both as a high-energy animal feed ingredient and a renewable biodiesel feedstock.
Unlike edible corn oil, which is extracted from corn germ for human consumption, DCO is not food-grade and is used in industrial applications such as biofuels and feed production.
“Distiller’s oil” or “distiller’s corn” oil generally refers to the oil recovered from corn stillage in dry milling ethanol plants.
What is Distiller's Corn Oil used for?
Distillers corn oil is widely used in two major sectors:
1. Animal Feed Industry
DCO is added to livestock rations—especially for beef, dairy and poultry—thanks to its high energy content. It improves feed efficiency, adds digestible fat and enhances overall caloric value.
2. Renewable Fuel Production
Because of its fatty acid profile, DCO is an important feedstock for biodiesel production, hydrated vegetable oil (HVO) and sustainable aviation fuel (SAF). Refineries prefer DCO due to:
- its consistent supply from ethanol plants,
- suitable triglyceride profile,
- the fact that it is a non-food feedstock and a side-stream from already existing production processes
Additionally, smaller volumes are used in industrial lubricants, surfactants, and chemical intermediates, expanding its market relevance.
How to produce DCO?
Bioethanol is made from raw alcohol. To produce the alcohol, the whole grain - in this case corn - is ground, mixed with water, the pH value is adjusted and enzymes are added to convert the starch from the corn to simple sugars. This sugar mixture is fermented with yeast and alcohol is produced. Raw alcohol is subsequently distilled off in a distillation column.
What remains from this process are the non-fermentable solids also known as distillation bottoms or stillage. The oil that was originally contained in the corn is now part of the stillage. To obtain it, centrifugal separation technology is the best choice.
From a process perspective there are several options to engineer the DCO separation stage in the overall stillage treatment process. But the question is not only "what is the best stage to recover the oil?", the question is also "what kind of centrifuge is the best choice for the job?"
Thin stillage de-oiling
This new process set-up developed by GEA moves the corn oil recovery to after stillage clarification but before evaporation. As the oil is now separated from the thin stillage, disk-stack separators can be used instead of decanters. Separators have higher g-forces as well as clarification areas than decanter centrifuges and thus have better separation results.
Thin stillage de-oiling with high speed disk-stack centrifuges
This thin stillage de-oiling comes with convincing results as experienced from first customer installations: it is still early enough in the overall process to recover as much oil as possible. In addition, the disk-stack separators can fully exploit the advantages of their larger clarification area and higher g-forces. Another huge benefit we have experienced: this process runs with greatly reduced to no demulsifiers/chemicals.
The advantages at a glance
- Greatly reduced to no chemicals needed
- Very high g-force and clarification area in disk-stack centrifuges capture even the smallest oil droplets and make for high yields
- No free oil in heavy phase (de-oiled syrup)
- Reduced fouling in your evaporator stage
- Disk-stack separators fully CIP possible
- Disk-stack centrifuges are low-maintenance centrifuges compared to decanters
- Protein phase as a separate on-top by-product with additional value
Cleared for takeoff
Applications and market value of DCO
DCO is increasingly in demand for renewable energy and feed applications. Most commonly, it is used as a feed ingredient in livestock nutrition or processed into biodiesel, hydrated vegetable oil (HVO) and sustainable aviation fuel (SAF). The global DCO market has been growing, driven by increasing demand in renewable fuels and animal nutrition.
Apart from recovering the feedstock for biofuels GEA has also extensive process know-how in the pretreatment of HVO and SAF.
By eliminating the bleaching stage with GEA Pre2Fuel, manufacturers benefit from significant savings potential: over 50 % lower operating costs and up to 12 % less CO2 emissions.
Conventional corn oil recovery from syrup
Conventionally, a decanter centrifuge separates the stillage into thin stillage and wet distillers grain (WDG) which is then dried to produce DDGS. In this process corn oil is being recovered from the thick stillage (evaporated thin stillage). Ethanol producers benefit from a DDGS with less fat and higher protein content as well as additional income from the corn oil which can be used as a feedstock for i.e. green diesel.
Conventional corn oil recovery from syrup
The Varipond system for GEA ethanol decanters makes it easy for producers to adapt the decanter to changing feed conditions or flow rates. Adjust the separation zone during operation for fast and precise results. No standstills, no tedious exchange of decanter parts, no unnessecary product loss. Instead, instant adjustment of the decanters setting and instant results. .
The advantages at a glance
- Additional income from the obtained corn oil
- DDGS with less fat and higher protein content
- Proven process setup
- GEA Varipond C system for always top separation results and yield even under varying feed conditions
FFA and triglycerides
DCO quality matters
The quality of recovered corn oil is critical for downstream processing.
GEA technology helps maintain high triglyceride levels and low free fatty acid (FFA) content, which are key quality indicators for biodiesel conversion and storage stability.
GEA centrifuges for whole stillage and DCO separation
Whole stillage decanters
Whole stillage decanters separate the stillage into a centrate called "thin stillage" which contains proteins and microfibers, and a solids phase called wet cake that contains the coarse constituents of the grain's fiber.
3-phase decanters
3-phase decanters separate the oil from the rest of the suspension consisting of solids and water.
High speed separators
High speed separators are able to capture smallest oil dropplets due to their high separation efficiency making for top recovery rates.
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Frequently asked questions
Can I retrofit this technology into my existing plant?
Yes. Both, separator‑ and decanter‑based systems can be retrofitted into most existing dry milling ethanol plants, depending on your process setup. GEA adapts the configuration to your current equipment, layout and capacity so you can increase DCO yield and improve DDGS quality without a complete process redesign.
How much oil can I expect to recover? How much corn is needed to make 1 gallon of ethanol? Can you make biodiesel, HVO and SAF from corn oil? Is DCO‑based biodiesel eligible under RFS2? Do I need chemicals or demulsifiers? What about DDGS quality? Why do refineries prefer DCO over other oils?
Actual yields depend on corn quality and process conditions, but plants using high‑efficiency GEA centrifuges can achieve up to 1.4 lbs of distillers corn oil (DCO) per bushel of corn or higher. Based on the standard oil content of corn of around 1.8 lbs you can thus recover up to 75 percent of DCO and more. This translates into a significant additional revenue stream per gallon of ethanol produced.
A typical dry milling ethanol plant produces about 2.8–3.0 gallons of ethanol per bushel of corn, depending on plant efficiency and corn quality. Alongside ethanol, this same corn also produces valuable co‑products such as distiller's corn oil (DCO) and DDGS.
Yes. Distiller's corn oil (DCO) is widely used as a feedstock for biodiesel, HVO and SAF. Its triglycerides can be converted via transesterification or hydrotreating into finished fuels. Because DCO is a non‑food industrial oil and a co‑product of ethanol production, it is a cost‑effective and sustainable alternative to food‑grade vegetable oils.
DCO is commonly used in biodiesel and renewable diesel pathways that can generate RINs under the U.S. Renewable Fuel Standard (RFS2), provided the production pathway meets EPA requirements. Producers should always consult current EPA guidance and their fuel buyers to confirm eligibility and RIN generation for specific DCO‑based fuels.
In many cases, GEA’s thin stillage de‑oiling setup can operate with greatly reduced or even no additional demulsifiers, depending on your feedstock and process conditions. This reduces operating costs, simplifies handling and can improve downstream evaporator performance.
Optimized corn oil recovery typically produces DDGS with higher protein and lower fat. This improves its nutritional profile and flowability and often enhances its market value in livestock feed markets. Many plants see improved acceptance from feed customers when DDGS fat levels are reduced and protein is concentrated.
Renewable diesel, biodiesel as well as HVO and SAF producers value distiller's corn oil because it offers:
