The correct answer is option C) Vermi-composting.

Explanation:

Vermi-composting is the process of using earthworms to decompose biodegradable solid waste. It is a type of composting that harnesses the natural digestive process of earthworms to break down organic materials into nutrient-rich vermicompost.

Vermi-composting involves the following steps:

1. Selection of suitable earthworm species: Certain species of earthworms, such as Eisenia fetida (red worms) or Lumbricus rubellus (red wrigglers), are commonly used for vermi-composting due to their ability to consume large amounts of organic waste and thrive in composting conditions.

2. Preparation of bedding material: A suitable bedding material, such as shredded paper, coconut coir, or straw, is prepared to create a favorable environment for the earthworms. The bedding material provides moisture, carbon, and aeration necessary for the earthworms' survival and decomposition process.

3. Addition of organic waste: Biodegradable solid waste materials, such as kitchen scraps (vegetable peels, fruit leftovers, coffee grounds), yard waste (grass clippings, leaves), and other organic materials, are added to the vermi-composting bin. The waste should be shredded or chopped into smaller pieces to facilitate faster decomposition.

4. Introduction of earthworms: The selected earthworm species are introduced into the vermi-composting bin. The earthworms consume the organic waste and break it down into smaller particles through their digestive process.

5. Decomposition and digestion: The earthworms process the organic waste by ingesting it, grinding it with their muscular gizzard, and digesting it in their intestines. During digestion, the organic waste is partially decomposed and transformed into nutrient-rich vermicompost.

6. Harvesting of vermicompost: After a certain period, usually a few months, the vermicompost is ready for harvesting. The vermicompost is separated from the remaining bedding material and earthworms using methods like manual separation or sieving. The harvested vermicompost is a dark, crumbly, and nutrient-rich fertilizer that can be used in gardening, horticulture, or agriculture.

Vermi-composting offers several advantages over traditional composting methods, including faster decomposition, better nutrient retention, and improved soil structure. It is an environmentally-friendly and sustainable approach to managing biodegradable solid waste while producing a valuable organic fertilizer.