Filed by Erika Engelhaupt and Steve Ritter
EMERALD CITY Across this sugarcane field lies the city of Ribeirão Preto; its name translates to “little black river.” The city of about half a million people lies at the heart of the world’s largest ethanol-producing region and is home to 26 of the 128 ethanol plants in São Paulo state. About 70% of Brazil’s ethanol comes out of São Paulo.
Today, we toured the Santa Elisa sugar refinery and ethanol distillery (right). We were welcomed with cups of Brazil’s typically potent coffee, pitchers of green cane juice, and slices of fresh-cut sugarcane to chew on (below). Brazil is the world’s leading producer of both coffee and sugarcane, and after sampling the native treats, we headed to the processing plant to see how sugarcane is turned into ethanol and refined sugar—and generates electricity to boot.
Sugarcane rolls in from the fields cradled on the backs of a constant stream of trucks (below). This Santa Elisa plant processes 6 million metric tons of sugarcane per year. By comparison, the largest plant in the country handles about four times that amount.
The cane gets washed after it comes off the trucks. (Residual soil from the washing is returned to the fields.) Next, the cane enters a series of five crushers (below).
The first two crushers (above, shown from right to left) expel most of the juice. Water is added to the third crusher, and subsequent treatment in the fourth and fifth crushers removes essentially all the sugar from the plants.
The fiber that’s left behind (called bagasse), shown above flying off the final crusher, is carried by conveyor belts to furnaces, where it is burned to generate electricity. The cane juice from the first pressing moves on to be refined into sugar, and the remaining juice is fermented by yeast into alcohol.
To make sugar, cane juice is pumped into large tanks (above, top), where it’s filtered and condensed. It’s then crystallized and centrifuged (above, bottom) to remove excess water.
We had the chance to taste-test the refined sugar, still warm from the centrifuge. It tasted like any other sugar, we admit, but it was undoubtedly the freshest we’ve ever sampled.
The Santa Elisa plant produces 475,000 metric tons of sugar per year. That’s about 475 billion packets of sugar or, on average, 1.3 billion packets per day. The sugar leaves the plant in 1 ton bags.
To make ethanol, a stream of cane juice from the crushers is diluted to a 20% sugar solution and poured into fermentation vats. During the next 8 hours, yeast ferment the sugars to a 6 to 10% ethanol brew. The yeast is removed and is either recycled to ferment more sugar or dried and sold as animal feed. The ethanol is then distilled in stages (shown below) to >99% purity, denatured, loaded into tanker trucks, and delivered to fuel distributors.
The Santa Elisa plant produces about 250 million L (about 67 million gal) of ethanol per year. As the region’s production continues to increase, both Petrobras, a state-owned petrochemical company, and a coalition of ethanol producers each plan to build pipelines for delivering ethanol to a coastal port to ship overseas.
As for the bagasse left over from the crusher, it dries to a fibrous, grass-like fluff that floats throughout the plant. Piles of it are sent to a set of furnaces to be burned to produce steam. The steam powers the crushers and generators that make electricity. The Santa Elisa plant generates 58 MW of electricity, of which 19 MW is used to power the plant. The remaining 30 MW is sold to the local power company.
Even with generators running at full capacity, the plant still produces excess bagasse, shown below in a mountain of leftovers. The company sells this material to other ethanol plants that burn it for power.
And that’s how they make the most of sugarcane here in Brazil, fully using the biomass to make sugar, ethanol, electricity, and a few extra Reais—the Brazilian currency that is worth about 50 cents to the dollar.