(a) Name the two institutes which developed the technology of biogas production in India.

(b) Explain the main principle used in this technology.

The correct answer is:
(a) IARI / Indian Agricultural Research Institute, KVIC / Khadi and Village Industries Commission.
(b) Methanogens when grown on cellulosic material anaerobically, they produce a large amount of methane along with CO₂ and H₂ which is called biogas and has a high calorific value.

Step-by-step Explanation:

Part (a): Institutes Developing Biogas Technology in India
The technology of biogas production in India was joint-collaborated and developed mainly due to the efforts of two premier organizations:
1. Indian Agricultural Research Institute (IARI): A national institute for agricultural research, education, and extension in India.
2. Khadi and Village Industries Commission (KVIC): A statutory body formed by the Government of India to plan, promote, facilitate, organize, and assist in the establishment of rural and village industries, including renewable energy initiatives like biogas.

Part (b): Main Principle of Biogas Technology
The fundamental biological principle behind biogas technology is the anaerobic digestion of organic matter:
1. Anaerobic Environment: The process occurs in the complete absence of oxygen (anaerobic conditions).
2. Cellulosic Feedstock: Cellulosic material, primarily found in cattle dung (commonly known as gobar), acts as the primary feed or substrate.
3. Methanogenic Bacteria: Anaerobic bacteria, collectively known as methanogens (specifically species like Methanobacterium), grow and break down the cellulosic material.
4. Gas Production: During this breakdown, these micro-organisms produce a gas mixture predominantly containing methane (${\mathrm{CH}}_4$) along with carbon dioxide (${\mathrm{CO}}_2$) and hydrogen ($H_2$). This mixture is called biogas, and because it contains a high percentage of methane, it possesses a high calorific value, making it an excellent fuel for cooking and lighting.