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.

What is/are the present constraint/constraints in using biomass as fuel for power generation ? 1. Lack of sustainable supply of biomass 2. Biomass production competes with food production 3. Bio-energy may not always be low carbon on a life-cycle basis Select the correct answer using the code given below :

(a) 1 and 2 only
(b) 3 only
(c) 2 and 3 only
(d) 1, 2 and 3 ✓ UPSC's answer

Why the answer is (d)

• Statement 1 is supported by the passage, which identifies the 'biggest challenge' as a 'long-term reliable supply' and notes that the 'maximum sustainable technical potential' is limited, making sustainable supply a constraint.

• Statement 2 is supported by the text stating that 'Energy crops, if not managed properly, compete with food production,' which is a key problem in biomass utilization.

• Statement 3 is supported by the passage's assertion that 'Some liquid biofuels... may aggravate rather than ameliorate carbon emissions on a life-cycle basis,' indicating that bio-energy is not always low carbon.

• Since all three statements are explicitly mentioned in the passage as challenges or constraints associated with biomass use, all are correct.

• Therefore, the correct option is (d) 1, 2 and 3.

Why the other options are wrong

(a) 1 and 2 only: This option is incorrect because it excludes Statement 3, which is valid as the passage notes that some biofuels may aggravate carbon emissions on a life-cycle basis.
(b) 3 only: This option is incorrect because it excludes Statements 1 and 2, which are valid constraints regarding supply reliability and competition with food production.
(c) 2 and 3 only: This option is incorrect because it excludes Statement 1, which is a valid constraint as the passage highlights the challenge of long-term reliable supply and limits to sustainable biomass.

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.