Ethanol by fermentation

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  • Created by: Sophie
  • Created on: 07-06-14 10:41

Ethanol by fermentation

Advantages

  • Ethanol in this process is made using sugar (glucose) found in plants. This makes it a renewable source as it can be grown again.
  • The process could be seen as carbon neutral because as the plant grows, it takes in carbon dioxide for photosynthesis. This therefore balances out the carbon dioxide released when it is fermented.
  • High amounts of energy are not needed as sugar is fermented at temperatures of around 35°c to 40°c. Low cost process because of low temperature.
  • In places such as Brazil, sugar cane is used in this process as it is a starchy material. In areas such as this, it is beneficial to the economy as it means that there is more employment.

Disadvantages

  • Two stage process.
  • It is a batch process.
  • When the ethanol concentration reaches about 15% the yeast dies and fermentation stops.
  • The product obtained is not pure.
  • 15% mixture must be constentrated and purified by distillation-extra cost
  • Carbon dioxide is produced.
  • It raises ethical questions as to weather we should use crops for ethanol when there are third world countries with no food.

Evaluation

There is a balanced argument for and against ethanol from fermentation. It is advantageous as it is produced from a renewable resource (sugar from plants such as sugar cane) and could be seen as carbon neutral. It helps the economy as sugar cane can be grown in poorer, hotter climates. The negatives are that it is impure, and more steps are needed afterwards to purify the ethanol obtained. It is a batch process, which means that less is produced in an amount of time, even industrially. It also raises the question 'is it right for us to use crops for ethanol when there are children in third world countries who are starving'?

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