Hint: Animal excreta and organic waste from the kitchen belongs to the category of biodegradable wastes. Biodegradable wastes are any organic matter that have the ability to break down water, methane, carbon dioxide or simple molecules by microorganisms or other living organisms by the process of anaerobic digestion, aerobic digestion, composting etc.
“Biodegradable” is referred to as the ability of the matter or thing to get decomposed or disintegrated by the action of bacteria or fungi that gets assimilated into the natural environment. Biodegradable materials include dead animals and plants, food waste like peel of vegetables and fruits, chicken, egg shells, paper, garden waste etc.
Kitchen waste and animal excreta can be reduced by the process of anaerobic fermentation that is by exposing them to sunlight and moisture. This occurs due to the presence of the bacteria in the matter that functions in the absence of oxygen. As a result, nitrous oxide and methane are produced in excess and are released into the atmosphere. The results of this decay process leads to the production of the source of energy known as biogas.
Therefore the correct answer is option (B) i.e, Using them for producing biogas.
Note: The recycling of the biodegradable waste results in the formation of the compost. On an industrial scale,these biodegradable materials can be treated either by anaerobic digestion or by composting. Composting is preferred for the fibrous material. For sludges and wet wastes that can easily be degraded, anaerobic digestion is more suitable. These processes do not have any adverse effect on the ecology.