Comparing the two methods of producing ethanol
2 marks · HardGive one reason why the fermentation method for producing ethanol is not as sustainable as it first appears, and one limitation of the hydration of ethene method for future production.
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Also accept: Fermentation requires land/water/food crops, which may compete with food supply, or needs energy for purification; Hydration of ethene relies on non-renewable petroleum, which will eventually run out
Common mistakes: Saying fermentation is always fully renewable without mention of limitations; Saying hydration is sustainable
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Marking points
B1 · 1 mark · Correct limitation of fermentation method (e.g. uses land for crops/energy needed for purification/competes with food supply)
B2 · 1 mark · Correct limitation of hydration of ethene method (e.g. uses finite resources/relies on crude oil)
Worked solution
Fermentation is not completely sustainable because it uses land and crops that could be used to grow food, and also needs energy for purification. Hydration of ethene uses crude oil, which is a finite, non-renewable resource and will one day run out.