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  Ethanol Fuel  
milling  
Once harvested, sugarcane is usually transported to the plant by tractor trailer trucks. After quality control sugarcane is washed, chopped, and shredded by revolving knives. The feedstock is fed to and extracted by a set of mill combinations to collect juice, that contain 10–15% sucrose, and the fiber residue.

The main objective of the milling process is to extract the largest possible amount of sucrose from the cane, and a secondary but important objective is the production of bagasse with a low moisture content as boiler fuel, as bagasse is burned for electricity generation (see below), allowing the plant to be self-sufficient in energy and to generate electricity for the local power grid. The cane juice or garapa is then filtered and treated by chemicals and pasteurized. Before evaporation, the juice is filtered once again, producing a byproduct rich in organic compounds. The syrup resulting from evaporation is then precipitated by crystallization producing a mixture of clear crystals surrounded by molasses. A centrifuge is used to separate the sugar from molasses, and the crystals are washed by addition of steam, after which the crystals are dried by airflow. Upon cooling, sugar crystallizes out of the syrup. From this point, the sugar refining process continues to produce different grades of sugar, and the molasses continue a separate process to produce ethanol.

Fermentation, distillation and dehydration

The resulting molasses are treated to become a sterilized molasses free of impurities, ready to be fermented. In the fermentation process sugars are transformed into ethanol by addition of yeast. Fermentation time varies from four to twelve hours resulting in an alcohol content of 7-10% by total volume (°GL), called fermented wine. The yeast is recovered from this wine through a centrifuge. Making use of the different boiling points the alcohol in the fermented wine is separated from the main resting solid components. The remaining product is hydrated ethanol with a concentration of 96°GL, the highest concentration of ethanol that can be achieved via complexed distillation and by national specification can contain up to 4.9% of water by volume. This hydrous ethanol is the fuel used by ethanol-only and flex vehicles in the country. Further dehydration is normally done by addition of chemicals, up to the specified 99.7°GL in order to produce anhydrous ethanol, which is used for blending with pure gasoline to obtain the country's E25 mandatory blend. The additional processing required to convert hydrated into anhydrous ethanol increases the cost of the fuel, as in 2007 the average producer price difference between the two was around 14% for São Paulo State. This production price difference, though small, contributes to the competitiveness of the hydrated ethanol (E100) used in Brazil, not only with regard to local gasoline prices but also as compared to other countries such as the United States and Sweden, that only use anhydrous ethanol for their flex fuel fleet.

electricity  
Since the early days bagasse was burnt in the plant to provide the energy required for the industrial part of the process. Today, the Brazilian best practice uses a high-pressure boiler that increase energy recovery, allowing most sugar-ethanol plants to be energetically self-sufficient and even sell surplus electricity to utilities. 

By 2000, the total amount of sugarcane bagasse produced per year was 50 million tons/dry basis out of more than 300 million tons of harvested sugarcane. Several authors estimated a potential power generation from the use of sugarcane bagasse ranging from 1,000 to 9,000 MW, depending on the technology used and the use of harvest trash. One utility in São Paulo is buying more than 1% of its electricity from sugar mills, with a production capacity of 600 MW for self-use and 100 MW for sale.  According to analysis from Frost & Sullivan, Brazil's sugarcane bagasse used for power generation has reached 3.0 GW in 2007, and it is expected to reach 12.2 GW in 2014. The analysis also found that sugarcane bagasse cogeneration accounts for 3% of the total Brazilian energy matrix. The energy is especially valuable to utilities because it is produced mainly in the dry season when hydroelectric dams are running low.

According to a study commissioned by the Dutch government in 2006 to evaluate the sustainability of Brazilian bio ethanol "...there are also substantial gains possible in the efficiency of electricity use and generation: The electricity used for distillery operations has been estimated at 12.9 kWh/tone cane, with a best available technology rate of 9.6 kWh/tone cane . For electricity generation the efficiency could be increased from 18 kWh/tone cane presently, to 29.1 kWh/tone cane maximum. The production of surplus electricity could in theory be increased from 5.3 kWh/tone cane to 19 kWh/tone cane.

 
       
 
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History

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Production

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Production process

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Agricultural Technology

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  Milling & Refining
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Overall Energy Use

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  Prices and effect on oil consumption
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Comparison with the United States

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Environmental & Social Impacts

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  Concerns