Single vs Double Pressing

At a glance

What single and double pressing are

Both describe how many times seed passes through a screw press (expeller). In single pressing, prepared seed goes through the press once and the de-oiled cake is done. In double pressing, that first-pass cake is fed through a press again — sometimes the same machine, sometimes a dedicated second press, often after re-conditioning to restore workable moisture and temperature — to extract more of the oil it still holds. Double pressing is a purely mechanical way to raise recovery; it uses no solvent, which is why it belongs to the world of presses and small-to-mid mills rather than large solvent plants that reach low residual oil chemically.

Yield versus the residual in the cake

The point of a second pass is to attack the oil left behind in the cake. A single press typically leaves a fairly high residual oil — indicatively around 10–18% depending on seed, preparation and how hard the press is run — because one pass cannot squeeze out everything. Re-pressing that cake brings the residual down to roughly 5–8%, recovering oil that would otherwise be sold (cheaply) in the cake or left as lost value. So double pressing raises total oil yield and lowers cake oil. Whether that extra recovery is worth it depends on the price of oil versus the value of the fattier cake and on the added running cost — which is the real trade-off, since the recovered oil is not free.

What the second pass costs

Double pressing is not free yield — it has real costs. Running every batch through a press twice roughly halves effective throughput for a given machine (or requires a second press), uses more energy per tonne, and puts more wear on worms and cage bars, which are consumable parts. The cake must often be re-conditioned between passes, adding a step. For a mill weighing this, the question is whether the value of the extra oil recovered exceeds the added energy, wear, labour and lost throughput — a calculation that shifts with oil prices and seed. A double-press calculator helps put numbers to it rather than guessing.

Why cold-press mills often double

There is a second, quality-driven reason to double-press that has nothing to do with squeezing the last drop. In cold pressing, the press must be run gently — slower, with the choke opened and the oil kept cool — to avoid the friction heat that would warm the oil and cost its cold-pressed status. A single gentle pass therefore recovers relatively little oil. Running two gentle passes lets a cold-press mill recover a reasonable total while keeping each pass cool, achieving with two mild presses what one hard, hot press would do to yield — but without the heat. So for cold-pressed and premium oils, double pressing is often less about chasing residual and more about reconciling good yield with low temperature.

When a single pass is enough

Plenty of operations sensibly stick to single pressing. If the seed presses easily and one pass already leaves an acceptable residual, if the cake is valued as a fattier feed (so the residual oil is not really lost, just sold in the cake), or if throughput and simplicity matter more than squeezing out the last few percent, a single pass is the right call. Large operations that want very low residual do not double-press at all — they pre-press and then solvent-extract, which reaches ~1% residual far more completely than any number of mechanical passes. So double pressing occupies a middle ground: more recovery than a single press, without the capital and safety of a solvent plant — useful for mid-scale mills and for cold-press work, unnecessary for both the simplest and the largest operations.

Verdict — which should you choose?

FAQ