Comparing the two methods of producing ethanol
3 marks · NormalEthanol can be produced industrially by fermentation or by hydration of ethene with steam.
Explain why the hydration of ethene is not considered a sustainable process in the long term.
State one environmental advantage of using fermentation instead.
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(a) The hydration method uses ethene produced from crude oil, which is a non-renewable and finite resource. Once crude oil runs out, ethene will not be available for ethanol production by this method, making it unsustainable in the long term.
(b) Fermentation uses renewable resources/sugar or crops, so it is more sustainable/environmentally friendly.
Common mistakes: Confusing renewable and non-renewable; Not explaining the resource limitation in a)
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Marking points
M1 (a) · 1 mark · Identifies that ethene is made from crude oil/finite resource.
A1 (a) · 1 mark · Explains that oil will eventually run out, so the process cannot continue indefinitely/unsustainable.
B1 (b) · 1 mark · States that fermentation uses renewable resources/crops/sugar.
Worked solution
(a) Hydration requires ethene from crude oil, which is non-renewable. Once crude oil is used up, ethene (and thus ethanol via this method) cannot be produced, making the process unsustainable.
(b) Fermentation uses crops such as sugar cane, which are renewable, so the process can continue indefinitely.