2.4

• What is fermentation?

  • Fermentation is a natural process in which an organism converts a carbohydrate such as starch or sugar into an alcohol
  • Various enzymes and microorganisms catalyse or facilitate the reactions involved
  • The process is carried out at 35oC because at higher temperatures, the microorganisms and enzymes would be destroyed
  • The reaction is:

                      C6H12O6 (aq) → 2CH3CH2OH(aq) + 2CO2(g)
• What are the three main bioethanol feedstocks?

  • Sugar Cane (high in sucrose)
  • Wheat (high in starch)
  • Forest Waste (high in cellulose)
• What chemical changes occur in the manufacturing process of bioethanol?

  • The carbohydrates are pulped with water; a process that involves blending the biomass in water to break up the cell or plant structures
  • Various enzymes are then added to the mixture to break the carbohydrate molecules down to form glucose.
  • Enzymes catalyse the fermentation of glucose to produce an ethanol solution
• What is distillation?

  • The process of separating the components or substances from a liquid mixture by using selective boiling and condensation
  • Fermentation produces a solution with 10% ethanol and 90% water. Distillation separates these two liquids, so that the ethanol can be used as a fuel
•  What are the advantages and disadvantages of using ethanol as an alternative fuel for motor vehicles?

  Advantages

  • Renewable (fuels that can be replaced at a sustainable rate)
  • Carbon Neutral (a process that absorbs the same amount of carbon as it generates)

   

  Disadvantages:

  • Lower Energy Content
  • Ethanol can make water with the Hydrogen and oxygen, therefore the water produced can damage the parts of the car
  • To have Ethanol, you need crops and that can lead to deforestation
• What is the differences between E10 and Petrol?

  E10:

  • Lower energy density (46 kJ g-1)
  • Cheaper
  • Cleaner combustion
  • Can be renewable fuel
  • Absorbs CO2 during formation to avoid the impact of CO2 emissions during combustion (lower net CO2 emissions)
  • Generally safer production

  Petrol:

  • Higher energy density (48 kJ g-1)
  • More widely distributed
  • Less CO2 produced per km when driving