Biogas is produced when organic material get decomposed and broken down by micro-organisms anaerobically (in the absence of oxygen). The whole degradation and biogas production process can be break down in the three basic steps as follows:
- Hydrolysis: This is the first step where particulate materials get converted to soluble compounds suitable for further breakdown in the next step.
- Fermentation: The second step of degradation is known as fermentation or acidogenesis where the products of hydrolysis such as simple sugars, amino acids, fatty acids etc. break down further and produce final products of fermentation such as H2, CO2 and acetate.
- Methanogenesis: The third and final step of anaerobic degradation is known as methanogenesis. In this process, one group of microorganism known as aceticlastic methanogens, converts acetate into H2 and CO2. Then a second group of microorganism referred as as Hydrogen-utilizing methanogens combined H2 and CO2 into methane (CH4). The end product of methanogenesis is biogas, a mixture of methane and carbon dioxide.
In Anaerobic Digestion (AD) technology, organic materials are let decomposed and broken down by anaerobic microorganisms by creating optimum environment for them to work. Anaerobic digestion take place generally in an enclosed vessel known as anaerobic digester with or without mixing, and the process can be perform either in Batch, semi-continuous or in continuous mode. This almost 200 years old technology has evolved over the year and exists from its very basic to most advanced form.