Groundnut oil is one of the most widely used cooking oils in India and many other parts of the world. But getting that oil out of the groundnut kernel takes more than just crushing it. To pull out almost every last drop of oil and leave behind a useful, protein rich cake, oil mills rely on a groundnut solvent extraction plant.
If you are planning to set up a groundnut oil business, or you simply want to understand how this process works, this guide breaks it down step by step in plain language. No heavy jargon, just a clear look at how raw groundnuts become refined oil and animal feed.
What Is a Groundnut Solvent Extraction Plant?
A groundnut solvent extraction plant is a processing unit that uses a chemical solvent, usually food grade hexane, to separate oil from groundnut kernels or from the press cake left after mechanical pressing. The solvent dissolves the oil trapped inside the seed, and the oil is later separated from the solvent through distillation.
This method is far more efficient than mechanical pressing alone. A screw press can only pull out around 85 percent of the available oil. Solvent extraction recovers almost all of the remaining oil, often pushing total oil yield above 98 percent. That difference matters a lot when you are running a commercial oil mill, because even a small gain in yield adds up to significant profit over time.
Mechanical Pressing vs Solvent Extraction
Most modern groundnut peanut oil refinery plants actually combine both methods. The kernels are pre pressed first, and the leftover cake goes through solvent extraction. Here is how the two methods compare.
| Factor | Mechanical Pressing | Solvent Extraction |
| Oil recovery | Around 85% | Up to 98-99% (from the residual cake) |
| Process cost | Lower upfront cost | Higher setup cost, better long term returns |
| Best suited for | Small scale, cold pressed oil | Medium to large scale commercial plants |
| Byproduct | Oil cake with 8-10% residual oil | De-oiled cake with less than 1% residual oil |
| Oil quality | Requires filtration | Requires refining before edible use |
Neither method is “better” on its own. A well designed plant uses pre pressing to remove the bulk of the oil quickly, then sends the cake to the solvent extraction unit to squeeze out what is left. This combined approach keeps energy costs down while maximizing yield.
Step by Step Groundnut Solvent Extraction Process
Here is how raw groundnuts move through the plant, from farm to finished oil.
1. Cleaning and Shelling
Harvested groundnuts arrive with pods, stones, dust, and other foreign material mixed in. The first job is to clean this out using sieves and aspiration systems. The pods are then shelled to separate the kernel from the outer husk, and the shells are removed with an aspiration or gravity separation system.
2. Second Cleaning and De-stoning
Even after shelling, kernels picked up from farms often carry sand, small stones, and metal fragments. Drum type cleaners remove sand and larger particles, while gravity or belt type de-stoners take out stones that are similar in size to the kernels. A magnetic separator then pulls out any iron particles, which protects downstream machinery and keeps the final oil and meal free of metal contamination.
3. Conditioning and Cooking
Cleaned kernels are conditioned in a vertical stack cooker or horizontal rotary cooker. This step uses controlled heat and moisture to:
- Soften the kernel structure so oil releases more easily
- Rupture the oil bearing cells
- Coagulate proteins to aid separation
- Reduce oil viscosity for smoother flow during pressing
4. Pre-Pressing
The conditioned kernels pass through a screw press (expeller) that squeezes out the bulk of the oil, usually around 85 percent. What comes out on one side is crude oil, and what remains is a press cake that still holds a meaningful amount of oil, typically 8 to 12 percent.
5. Flaking
The press cake is flaked into thin sheets before it goes into the extractor. Thinner flakes have more surface area, which lets the solvent penetrate the material faster and dissolve the residual oil more thoroughly. This step has a big impact on how efficient the extraction stage will be.
6. Solvent Extraction
The flaked cake enters the extractor, where it comes into contact with food grade hexane. The solvent seeps into the flakes and dissolves the trapped oil, forming a mixture called miscella. What is left behind, called the marc, still contains a small amount of solvent that needs to be removed.
7. Desolventizing the Meal
The extracted meal (marc) passes through a desolventizer toaster, which uses steam and heat to drive off any remaining hexane. This step recovers the solvent for reuse and produces a safe, dry meal that can be sold as animal feed.
8. Miscella Distillation
The oil rich solvent mixture, or miscella, goes through a miscella distillation system. Here, heat is applied in stages to evaporate the hexane out of the oil, leaving behind crude groundnut oil.
9. Hexane Recovery
Solvent is expensive, so no well run plant lets it go to waste. A hexane recovery system condenses the vaporized solvent from both the desolventizer and the distillation unit, cools it, and sends it back into the process. A good recovery system can bring solvent loss down to a very small fraction, which keeps running costs low and the plant safer to operate.
10. Oil Refining
Crude groundnut oil is not yet ready for the kitchen. It needs to go through refining, which typically includes:
- Degumming to remove phospholipids and gums
- Neutralization to remove free fatty acids
- Bleaching to remove color pigments
- Deodorization to strip away unwanted odors and improve shelf life
Once refined, the oil is filtered, cooled, and ready for packaging as edible groundnut oil.
11. De-Oiled Cake Production
The dry, solvent free meal from the desolventizer is processed further into de-oiled cake, a protein rich byproduct. This cake is a valuable ingredient in poultry and cattle feed, and selling it adds a useful second revenue stream for the plant.
Why Solvent Extraction Improves Oil Recovery
Mechanical pressing alone leaves a lot of oil behind in the cake, sometimes as much as 10 percent. Over a full production run, that unrecovered oil represents real lost income. Solvent extraction closes that gap. You can read a more detailed breakdown of the yield difference in our article on how solvent extraction plants improve oil recovery.
Beyond yield, solvent extraction also produces a more consistent, lower fat meal, which is easier to store, transport, and sell as feed.
Key Equipment in a Groundnut Solvent Extraction Plant
A typical plant includes:
- Cleaning and de-stoning equipment
- Decorticators and shelling machines
- Conditioners and cookers
- Screw presses (expellers)
- Flaking rolls
- Extractor unit
- Desolventizer toaster
- Distillation columns for miscella
- Hexane recovery and condensing system
- Stainless steel reactors and process tanks
- Valves and instrumentation for process control
If you are planning to set up or expand a plant, it also helps to know common pitfalls. Many first time investors run into avoidable oil plant installation mistakes that end up costing time and money, so it is worth reviewing these before finalizing your plant layout.
Choosing the Right Plant Manufacturer
The performance of your groundnut solvent extraction plant depends heavily on the manufacturer you choose. A good manufacturer will offer proper engineering support, quality spares, and after sales service. If you are unsure where to start, our guide on how to choose the right solvent extraction plant manufacturer in India covers the key questions to ask before signing a contract, and it is worth reading alongside a broader look at turnkey oil plant manufacturers if you want a single vendor to handle the full project.
Frequently Asked Questions
Q1 What solvent is used in groundnut oil extraction?
Food grade hexane is the most common solvent used because it dissolves oil efficiently and can be recovered and reused with minimal loss.
Q2 Is solvent extracted groundnut oil safe to eat?
Yes. After distillation and refining, no meaningful trace of solvent remains in the finished oil. Refining steps like degumming, neutralization, bleaching, and deodorization also improve the oil’s purity, taste, and shelf life.
Q3 How much oil can a solvent extraction plant recover from groundnut cake?
A well designed plant can recover almost all of the residual oil left in the press cake, often bringing the leftover oil content in the meal down to less than 1 percent.
Q4 What happens to the leftover meal after extraction?
The desolventized meal becomes de-oiled cake, which is sold as a protein source for cattle and poultry feed.
Q5 Do small groundnut oil producers need a solvent extraction unit?
Not always. Small scale or cold press producers often skip solvent extraction and sell the oil cake as is. Solvent extraction becomes worthwhile once you are operating at a scale where the extra oil recovery clearly outweighs the equipment and running costs.
Final Thoughts
A groundnut solvent extraction plant brings together cleaning, pressing, extraction, distillation, and refining into one continuous process that turns raw kernels into edible oil and valuable feed cake. Understanding each stage helps you make smarter decisions, whether you are setting up a new plant, upgrading an existing one, or simply want to know what goes into the bottle of groundnut oil in your kitchen.
If you are planning a new project or need guidance on plant capacity, layout, or spares and equipment, our team can help you plan a setup that fits your budget and production goals. Get in touch to discuss your requirements.
