The National Policy on Biofuels was amended in 2022 chiefly to

The correct answer is B, ethyl alcohol, C2H5OH. Ethanol is the two carbon alcohol obtained by the fermentation of sugars by yeast, and it is the alcohol blended into petrol under the Ethanol Blended Petrol programme. Option A is wrong because methyl alcohol or methanol is a different, single carbon alcohol; it is highly poisonous and is the subject of a separate methanol blending programme, not the ethanol one. Option C is wrong because glycerol is a three carbon trihydric alcohol and in this chapter appears as the by-product of biodiesel manufacture, not as a fuel blend. Option D is wrong because acetic acid is a carboxylic acid, the acid of vinegar, formed when ethanol is oxidised; it is not a fuel. Remember that ethanol also raises the octane number of petrol.

The correct answer is C, paddy straw. Second generation biofuels are made from lignocellulosic biomass that is not food, such as paddy straw, wheat straw, bagasse, cotton stalk and municipal solid waste; the cellulose must first be broken down into fermentable sugars, which makes the process costlier and earns these fuels the name advanced biofuels. Options A and B are wrong because sugarcane juice and maize grain are food or food crop materials and yield first generation ethanol, the ordinary kind. Option D is wrong because edible mustard oil would give first generation biodiesel, and Indian policy avoids edible oils altogether and looks to non-edible seeds like Jatropha instead. India built its first commercial second generation ethanol plant, running on paddy straw, at Panipat in Haryana.

The correct answer is A, compressed bio-gas. SATAT stands for Sustainable Alternative Towards Affordable Transportation and was launched in October 2018 by the Ministry of Petroleum and Natural Gas; under it the oil marketing companies invite entrepreneurs to set up compressed bio-gas plants from agricultural residue, cattle dung and municipal waste and offer to buy the gas for sale at their retail outlets. Option B is wrong because rooftop solar is promoted through separate schemes of the Ministry of New and Renewable Energy. Option C is wrong because nuclear fuel reprocessing is the business of the Department of Atomic Energy and has no connection with biomass. Option D is wrong because green hydrogen has its own National Green Hydrogen Mission. Compressed bio-gas is over ninety per cent methane.

The correct answer is C, methane. Biogas is produced by the anaerobic digestion of organic matter, and methane is its largest component, roughly half to three quarters of the gas by volume; this is what makes biogas combustible. Option A is wrong because carbon dioxide is the second largest component, usually a quarter to a half, and it does not burn; it is scrubbed out when raw biogas is upgraded to compressed bio-gas. Option B is wrong because hydrogen sulphide is present only in traces, and it is removed because it is corrosive and foul smelling. Option D is wrong because carbon monoxide is a product of incomplete combustion of fuels and is not a normal constituent of biogas at all. Upgraded compressed bio-gas is over ninety per cent methane.

The correct answer is A, transesterification. In transesterification a vegetable oil or animal fat is made to react with methanol or ethanol in the presence of an alkaline catalyst such as potassium hydroxide, giving fatty acid methyl esters, which are biodiesel, and glycerol as the by-product. Option B is wrong because fractional distillation is how crude petroleum is separated into petrol, kerosene and diesel; it separates an existing mixture instead of making a new ester. Option C is wrong because hydrogenation adds hydrogen across double bonds and is the process that turns liquid oils into vanaspati. Option D is wrong because fermentation is the anaerobic action of yeast on sugars, which is how ethanol and not biodiesel is produced. Pure biodiesel is designated B100, a five per cent blend is B5, and the alkaline catalyst commonly used in the reaction is potassium hydroxide or sodium hydroxide.