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. 21. In the context of using biomass, which of the following is/are the characteristic/characteristics of the sustainable production of biofuel? 1. Biomass as a fuel for power generation could meet all the primary energy requirements of the world by 2050 2. Biomass as a fuel for power generation does not necessarily disrupt food and forest resources 3. Biomass as a fuel for power generation could help in achieving negative emissions, given certain nascent technologies Select the correct answer using the code given below:

Explanation: The question asks for characteristics of the sustainable production of biofuel based on the provided passage. 1. Biomass as a fuel for power generation could meet all the primary energy requirements of the world by 2050. The passage states: "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." "Almost a quarter" is far from "all". Therefore, statement 1 is incorrect. 2. Biomass as a fuel for power generation does not necessarily disrupt food and forest resources. The passage mentions: "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". This phrase suggests that there is a potential for biomass production that does not disrupt food and forest resources. However, the passage also highlights significant challenges: "Energy crops, if not managed properly, compete with food production and may have undesirable impacts on food prices." It also notes that "only part of this [sustainable potential] is realistically and economically feasible." Given the overall cautionary tone and emphasis on the difficulties and risks of disruption in practice, stating that it "does not necessarily disrupt" might be considered an oversimplification or not a defining characteristic of *sustainable production* in a practical, large-scale sense, where disruption is a constant threat and often occurs if not managed perfectly. While a theoretical potential without disruption exists, the passage's emphasis on the challenges suggests this is not a readily achievable characteristic for sustainable production. Therefore, this statement is considered incorrect in the context of the passage's overall message. 3. Biomass as a fuel for power generation could help in achieving negative emissions, given certain nascent technologies. The passage states: "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." "Unproven technology" aligns with "nascent technologies," and the goal is "to achieve negative emissions." This statement is directly supported by the text. Therefore, statement 3 is correct. Based on the analysis, only statement 3 is clearly and unambiguously supported by the passage as a characteristic of biomass use in the context of sustainability and climate mitigation. The final answer is B