UPSC Prelims 2013 · GS Paper I
Question 13: Economy and Social Development
With reference to the usefulness of the by-products of sugar industry, which of the following statements is/are correct?
- 1.Bagasse can be used as biomass fuel for the generation of energy.
- 2.Molasses can be used as one of the feedstocks for the production of synthetic chemical fertilizers.
- 3.Molasses can be used for the production of ethanol.
Select the correct answer using the codes given below.
AnswerUPSC’s answer is (c).
Bagasse, the fibrous residue left after cane is crushed, is burnt in sugar mills as biomass fuel to generate heat and power. Molasses, the syrup left after sugar crystallises, is fermented to make ethanol, which is blended with petrol. Synthetic chemical fertilisers such as urea are made from ammonia produced from natural gas, naphtha or coal, not from molasses, so statement 2 is wrong. So 1 and 3 only.
- 1. Bagasse is burnt in cogeneration plants for power.
- 2. Chemical fertilisers use natural gas, naphtha or coal as feedstock, not molasses.
- 3. Molasses is fermented into ethanol.
How you could have got this
- If you were sure statement 2 is not correct, (b) and (d) go: each of them includes 2.
What you needed to know: Chemical fertilisers use natural gas, naphtha or coal as feedstock, not molasses.
- Then, if you were sure statement 3 is correct, (a) goes: it leaves 3 out.
What you needed to know: Molasses is fermented into ethanol.
Only (c) is left. You didn’t need statement 1.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Wrong. Molasses is also a feedstock for ethanol.
- (b) Wrong. Statement 2 is false; molasses is not a feedstock for synthetic chemical fertilisers.
- (c) Correct. Bagasse is fuel and molasses gives ethanol; molasses does not make chemical fertiliser.
- (d) Wrong. Statement 2 is false.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2013, General Studies Paper I, Series A. The paper on upsc.gov.in.