• Renewable energy sources are energy sources that are always being replenished. They can never be depleted. Some examples of renewable energy sources are solar energy, wind energy, hydropower, geothermal energy, biomass energy, ethanol, jatropha plant, and bagasse.
• Ethanol, derived from plant material, is a renewable energy source because the production and combustion of ethanol complete a cycle.
  
• The oil from Jatropha plants is mainly converted into biodiesel for use in diesel engines(biodiesel).
  
• Bagasse is the dry pulpy residue left after the extraction of juice from sugar cane. Bagasse is usually combusted in furnaces to produce steam for power generation. 
• Hence ethanol, jatropha plant and Bagasse are the renewable sources of energy.
• So, the correct answer is 'All the above'.

The composition of biogas is :

• Biogas is a mixture of gases produced by the breakdown of organic matter in the absence of oxygen. It is produced by anaerobic digestion with methanogen or anaerobic organisms, which digest material inside a closed system, or fermentation of biodegradable materials.
• Biogas is primarily methane ($CH _4$) and carbon dioxide ($CO _2$) and may have small amounts of hydrogen sulfide ($H _2$S), moisture and siloxanes.
  
• Hence Methane is present predominantly in biogas.
• So, the correct answer is 'Methane'.

Biogas consists mostly of methane (CH$ _4$), carbon dioxide (CO$ _2$) and a mix of trace gases including nitrogen, hydrogen sulfide (H$ _2$S), hydrogen and others. Methane is the main constituent (63%) of the biogas. The other major constituent is CO$ _2$ (30%).
Hence, option B is correct.

I can help in maintaining the green wealth of my locality by taking care of the plants and trees growing in or around my locality. I can plant more and more trees. I can also encourage the people in my locality to plant more trees by informing them about the importance of growing trees. I can make young children aware of the effects that deforestation has on our environment and on our planet. I can also ask them to water the plants daily, which will take very little of their time. I believe planting new trees is as important as taking care of the existing trees.

In many areas, biogas can be used as a replacement for fuels like firewood and dried dung for their energy consumption. Replacing firewood with biogas would have a positive effect on deforestation. That would improve  the local environments, ecosystems, problems with erosion etc. Hence option A is correct.

Biogas is principally a mixture of methane (CH₄) and carbon dioxide (CO₂) along with hydrogen (H2) gas in small amount. It can be collected from landfills, covered lagoons, or enclosed tanks called anaerobic digesters. Biogas is commonly made from animal manure, sludge settled from wastewater, and at landfills containing organic wastes. Hence option C is correct.

The biogas plant helps in the degradation of the organic waste to form gases like methane, carbon dioxide, hydrogen and some other gases in traces. The wastes from various different sources can be used for the production of biogas. The molasses are considered as the industrial wastes which can be degraded by the bacterial action. The cattle and animal dung is used in the biogas plant. The vegetable peels, fruit peel and other domestic wastes are used as the sources for the production of biogas. 

Definition of biogas- The gas fermentation of animal during which takes place in the absence of air due to the presence of anaerobic bacteria. 

• The production of alternative sources of non-renewable (not capable of being replenished) sources is called as Eco-efficiency.
• The term eco-efficiency was coined by WBCSD(World Business Council for Sustainable Development) in its 1992 publication
  
• Eco-efficiency can be achieved by the use of alternative raw materials and recycling wastes.
  
• Hence the production of alternative sources of non-renewable sources is called as Eco-efficiency.
• So, the correct answer is 'Eco-efficiency'.

• Bagasse is the dry pulpy fibrous residue left after the extraction of juice from sugar cane.
• Bagasse products are perfect alternatives to petroleum-based and plastic products.
  
• It is used as a biofuel for the production of heat, energy, and electricity, and in the manufacture of pulp and building materials. 
  
• Hence bagasse is Biomass of sugarcane.
• So, the correct answer is 'Biomass of sugarcane'.

(i) Bhopal gas disaster took place on 3rd December 1984 and this day is now observed as the Bhopal gas tragedy day in India to make the anniversary of the Bhopal gas disaster.

Less than $50\%$ of the solar energy incident over earth is PAR(photosynthetically active radiation).

Pollution from animal excreta and organic waste from kitchen can be most profitably minimized by using them to produce biogas for domestic use. 

Definition of sustainable development the management of forest resources in a sustainable manner, involves two aspects - prevention of deforestation and extension of out forest wealth. 

Solar cooker is a non conventional sources of energy. Increasing population would need more and more energy. New sources such as solar energy, nuclear energy are being used. Solar cooker uses solar energy.