Passage

Directions for the following 5 (five ) items : Read the following two passages and answer the items that follow each passage. Your answers to these items should be based on the passages only. Passage-1 Biomass as fuel for power, heat, and transport has the highest mitigation potential of all renewable sources. It comes from agriculture and forest residues as well as from energy crops. The biggest challenge in using biomass residues is a long-term reliable supply delivered to the power plant at reasonable costs; the key problems are logistical constraints and the costs of fuel collection. Energy crops, if not managed properly, compete with food production and may have undesirable impacts on food prices. Biomass production is also sensitive to the physical impacts of a changing climate. Projections of the future role of biomass are probably overestimated, given the limits to the sustainable biomass supply, unless breakthrough technologies substantially increase productivity. Climate-energy models project that biomass use could increase nearly four-fold to around 150 – 200 exajoules, almost a quarter of world primary energy in 2050. However the maximum sustainable technical potential of biomass resources (both residues and energy crops) without disruption of food and forest resources ranges from 80 – 170 exajoules a year by 2050, and only part of this is realistically and economically feasible. In addition, some climate models rely on biomass-based carbon capture and storage, an unproven technology, to achieve negative emissions and to buy some time during the first half of the century. Some liquid biofuels such as corn-based ethanol, mainly for transport, may aggravate rather than ameliorate carbon emissions on a life-cycle basis. Second generation biofuels, based on ligno-cellulosic feedstocks – such as straw, bagasse, grass and wood – hold the promise of sustainable production that is high-yielding and emit low levels of greenhouse gases, but these are still in the R & D stage.

With reference to the passage, following assumptions have been made : 1. Some climate-energy models suggest that the use of biomass as a fuel for power generation helps in mitigating greenhouse gas emissions 2. It is not possible to use biomass as a fuel for power generation without disrupting food and forest resources Which of these assumptions is/are valid ?

(a) 1 only ✓ UPSC's answer
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Why the answer is (a)

• Assumption 1 is valid because the passage states that biomass has the 'highest mitigation potential of all renewable sources' and that second-generation biofuels 'emit low levels of greenhouse gases,' implying that models projecting its use assume it helps mitigate emissions.

• Assumption 2 is invalid because the passage explicitly defines the 'maximum sustainable technical potential' as the range 'without disruption of food and forest resources,' indicating that such use is possible if managed within these limits.

• The passage notes that energy crops 'if not managed properly' compete with food, which implies that proper management allows for use without disruption, contradicting the absolute claim in Assumption 2.

• Therefore, only Assumption 1 is supported by the text, leading to option (a).

Why the other options are wrong

(b) 2 only: Assumption 2 is invalid because the passage specifies a sustainable technical potential that exists without disrupting food and forest resources.
(c) Both 1 and 2: Assumption 2 is invalid because the passage confirms that biomass can be used sustainably without disrupting food and forest resources.
(d) Neither 1 nor 2: Assumption 1 is valid because the passage identifies biomass as having the highest mitigation potential for greenhouse gas emissions.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2016, held on 7 August 2016. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.