Sugar is made from sugarcane through a series of steps that extract the sweet juice from the plant, remove impurities, and concentrate the liquid until sugar crystals form. A mature sugarcane stalk is about 12 to 16% sugar by weight, with 63 to 73% water and the rest fiber and other solids. Turning that into the white granules in your kitchen takes both physical force and careful chemistry.
What’s Inside a Sugarcane Stalk
Sugarcane is essentially a tall grass that stores energy as sucrose in its stem. At maturity, the plant reaches 3 to 4 meters tall with a stem about 5 centimeters in diameter. That stem makes up roughly 75% of the entire plant and contains 11 to 16% fiber, 12 to 16% soluble sugars, and 2 to 3% non-sugar carbohydrates, all suspended in water. The goal of sugar production is to separate that sucrose from everything else.
Harvesting and the Race to the Mill
Once sugarcane is cut, the clock starts ticking. Sucrose begins breaking down almost immediately, and delays between cutting and crushing are the single biggest controllable factor in post-harvest sugar loss. In one study of several cane varieties, sucrose dropped 4 to 12% within just 24 hours of harvest. Leave the cane sitting for five days in warm weather, and losses can exceed 30 to 55% depending on the variety and temperature.
A three- to four-day delay between harvesting and crushing is common in the sugar industry, which means significant sugar is lost before processing even begins. The most effective countermeasure is simply speed: cut the cane and get it to the mill as fast as possible.
Crushing the Juice Out
At the mill, the cane stalks are shredded and then passed through heavy rollers that squeeze the juice out of the fibrous material. This is the milling method, and it uses a series of roller sets (typically several units with large steel rollers) that progressively extract more liquid from the shredded cane.
Some mills use a different approach called diffusion, which works by rupturing the cane cells and then washing them with water in a counter-current system. Hot water flows in the opposite direction of the shredded cane, gradually picking up sugar as it moves. The liquid becomes more concentrated as it passes over fresher cane. Diffusion can extract sugar more thoroughly than milling alone, and many modern facilities use a combination: a diffuser for primary extraction followed by a single dewatering mill to squeeze remaining juice from the spent fiber.
The leftover fibrous material, called bagasse, doesn’t go to waste. More on that later.
Cleaning the Juice
Raw sugarcane juice is a murky, greenish-brown liquid full of dissolved impurities: proteins, organic acids, waxes, and fine plant particles. Clarification removes these so the sugar can crystallize cleanly.
The standard method involves adding lime (calcium hydroxide) to the juice, which raises its pH and causes many impurities to clump together and settle out. The juice is also heated, typically to around 80°C, which helps remove starch, phosphate, and turbidity. Some mills use carbonation, where carbon dioxide is bubbled through the limed juice. This forms calcium carbonate particles that trap color and impurities as they settle. Under optimal conditions (pH between 8.0 and 9.5, temperatures around 80°C, and 20 to 40 minutes of reaction time), carbonation can remove 88 to 93% of the juice’s color.
After clarification, the juice passes through filters to catch any remaining solids. What comes out is a clear, pale yellow liquid.
Boiling It Down
Clarified juice is still mostly water, starting at roughly 15% dissolved sugar (measured in degrees Brix, a scale for sugar concentration). To crystallize sugar, you need to remove most of that water. This happens in two stages.
First, the juice enters a series of large vessels called multiple-effect evaporators. These are connected so that the steam produced by boiling juice in the first vessel heats the second, and so on. Each successive vessel operates at lower pressure, which lowers the boiling point and lets the juice boil at gentler temperatures. This saves enormous amounts of energy. By the time the juice leaves the third effect, it has thickened from about 15% to around 40% sugar concentration, now called syrup.
The syrup then moves to vacuum pans for the final concentration. These large enclosed vessels operate under vacuum, further reducing the boiling point so the sugar isn’t damaged by excessive heat. As water continues to evaporate, the syrup becomes supersaturated, and sugar crystals begin to form. Mill operators often introduce tiny seed crystals to control the process. The thick mixture of crystals and remaining liquid is called massecuite.
Separating Crystals From Molasses
The massecuite goes into centrifuges, which are essentially spinning baskets with perforated walls. As the basket spins at high speed, the liquid (molasses) is flung outward through the perforations while the sugar crystals stay inside. The crystals get a wash with hot water while still in the centrifuge to rinse off clinging molasses.
This first batch of molasses still contains recoverable sugar, so it’s boiled and centrifuged again. Mills typically repeat this cycle two or three times, each round yielding a darker, less pure molasses. The final round produces blackstrap molasses, which has too little sugar left to be worth processing further. It’s sold for animal feed, fermentation into rum or ethanol, or as a food product on its own.
What comes out of the centrifuge after the first spin is raw sugar: golden-brown crystals coated in a thin film of molasses. This is the product that many mills ship to refineries.
Refining Into White Sugar
Raw sugar is edible, but it still contains color, minerals, and other impurities. Turning it into the white granulated sugar sold in stores requires several additional steps.
The first step, called affination, involves washing the raw crystals with warm, nearly saturated syrup. This loosens the molasses film on each crystal without dissolving the crystal itself. The crystals are then spun in a centrifuge and rinsed with hot water. If the refinery is integrated with the mill, this step may be simplified or skipped because the crystals were already washed more thoroughly during initial processing.
Next, the washed crystals are dissolved in hot water and steam-heated into a syrup, which is screened to remove any particles. This syrup goes through another round of clarification, typically using lime along with either phosphoric acid or carbon dioxide to remove remaining impurities.
The clarified syrup then passes through a decolorization step. Refineries use adsorbent materials, most commonly granular activated carbon or bone char (made from degreased cattle bones), which trap the molecules responsible for color and off-flavors. The result is a nearly colorless sugar solution.
From here, the process mirrors what happened at the mill: evaporation, vacuum pan crystallization, and centrifuging. The white sugar crystals are washed once in the centrifuge, then sent to drying drums. One drum dries the crystals and a second cools them. Finally, the dried sugar passes over vibrating mesh screens that sort it by crystal size. The finished granulated sugar moves to conditioning bins, then storage, and eventually into bags or bulk shipments.
How Much Sugar One Field Produces
The yield from sugarcane to finished sugar is surprisingly modest. A productive field might grow around 150 tons of cane per hectare, but that typically yields only about 10 tons of sugar. That’s roughly a 6 to 7% conversion rate from raw cane to finished product, which makes sense when you consider that most of the stalk is water and fiber. The “pol” percentage, a measure of sucrose content in the juice, runs around 15 to 16% in good varieties under favorable conditions.
What Happens to the Leftover Fiber
Bagasse, the crushed fiber left after juice extraction, is one of sugar production’s most valuable byproducts. Nearly every sugar mill burns it to generate steam and electricity through cogeneration, making the facilities largely energy self-sufficient.
In Brazil, sugarcane bagasse powers 11.5 gigawatts of installed electrical capacity, accounting for 6.4% of the country’s total. India’s sugar mills export around 7 gigawatts to the power grid. In China, 75 to 80% of the electricity generated from bagasse is consumed by the mills themselves, with the rest going to the grid or the bagasse diverted to pulp and paper production. The milling system alone consumes enormous energy, with backpressure turbines driving the rollers using around 60% of the steam a mill produces. Still, many modern mills generate surplus electricity that they sell back to the grid.