- Home
- Oil mill process
How an oil mill turns seed into oil
Every oil mill does the same five things, whatever the seed. Here they are in plain words, followed by the full machine line for each seed, drawn by the people who build them.
The whole idea
Five jobs, in the same order
1. CleanTake out dust, straw and stones, and remove husk where the seed has one.
2. WarmWarm oil flows and cold oil does not, so the seed is heated before pressing.
3. SqueezeA turning screw squeezes out the oil. This splits the seed into oil and a dry cake.
4. Clean the oilSift out the bits, let the oil settle, then filter it until it runs clear.
5. Bag the mealThe dry cake is weighed and bagged, usually to be sold as animal feed.
Choose your seed
The full line for each seed
Pick a seed for its full machine line, drawn step by step and explained in plain words.
Mustard
CleanWarmPressOil + meal2 presses, one after the otherSee the line
Groundnut
CleanWarmPressOil + meal2 line optionsSee the line
Soybean
CleanExtrudePressOil + mealOne pressSee the line
CanolaCleanWarmPressOil + meal2 presses side by sideSee the line
Sunflower
CleanWarmPressRefineOil + meal3 line optionsSee the line
Ways to arrange presses
One press, side by side, or one after the other
- One press
- The simplest arrangement. All the seed goes through one machine.
- Side by side
- Presses share one feed. The mill crushes more seed in a day, and each piece of seed is pressed once.
- One after the other
- Also called double crushing. The cake from the first press goes through the second, to recover more oil.
Words explained
- Expeller or screw press
- The machine that squeezes oil out of seed, using a turning screw and no chemicals.
- Cake or meal
- What is left of the seed after pressing. It still holds some oil and protein, and is usually sold as animal feed.
- Foots
- The bits of seed that come out of the press mixed in with the oil.
- Conditioning
- Warming the seed and evening out its moisture so the oil releases easily.
- Crude oil
- Pressed and filtered oil that has not been refined.
- Soap stock
- What settles out when free fatty acids are removed from the oil during refining.
Common questions
- How is oil made from seeds?
- Seed is cleaned, warmed, and squeezed in a machine called an expeller. That gives two products: oil, and a dry cake called meal. The oil is then sifted and filtered until it runs clear, and the meal is bagged.
- What machines does an oil mill need?
- At a minimum: machines to clean the seed, a cooker with a boiler for steam, one or more expellers, and a sifter, settling tank and filter for the oil. Conveyors and elevators link them together. The exact list depends on the seed, which is why each one has its own line here.
- What is the difference between side-by-side presses and double crushing?
- Presses side by side share one feed, and each piece of seed goes through one press only, so the mill crushes more seed in a day. In double crushing the presses work one after the other, and the cake from the first goes through the second to recover more oil.
- Why does the seed need to be cooked before pressing?
- Warm, evenly moist seed gives up its oil far more easily than cold seed. Soybean on our line is the exception: it is extruded rather than cooked in steam, which does a similar job.
- What happens to what is left after pressing?
- The cake, or meal, is weighed into bags and usually sold as animal feed. On some lines it is first broken up and cooled. Bits of seed caught in the oil are sent back through the press, so their oil is not wasted.
Tell us your seed and we will draw your line
Send your seed and your daily tonnage. We reply with the machine list and layout for your mill.