Biogas, as the name implies, is a mixture of organic substances under anaerobic conditions, which is formed by microbial fermentation. We often see bubbles coming out in swamps, sewers or cesspools. If we strike a match, we can light it. It's natural methane. Since this gas was first found in swamps, it is called methane. Biogas is produced by anaerobic (anaerobic) fermentation of human and animal manure, straw, sewage and other organic matters in a closed biogas digester. Biogas is a combustible mixture. Biogas is a combustible gas produced by anaerobic digestion of organic matter by microorganisms. Biogas is a mixture of many gases, usually containing 50% to 70% methane, the rest is carbon dioxide and a small amount of nitrogen, hydrogen and hydrogen sulfide. Its nature is similar to that of natural gas.
Biogas is produced by the decomposition of a variety of microorganisms (collectively referred to as biogas bacteria) under the conditions of air isolation and maintaining a certain humidity, temperature, pH, etc. The process of biogas production by bacteria is called biogas fermentation. This is the basic principle of methanogenesis, i.e. anaerobic mechanism. Artificial methanogenesis must have two conditions: first, there must be a strict anaerobic environment; second, there must be sufficient fermentation raw materials, sufficient bacterial agents, and appropriate fermentation concentration, fermentation temperature and pH value. The biochemical process of fermentation can be divided into three stages:
Stage 1 (liquefying stage): fermentable bacteria use large molecular organics such as extracellular enzymes secreted by bacteria to decompose poultry manure, crop straw and soybean products for wastewater treatment to form small molecular compounds such as monosaccharide, amino acid, glycerin and fatty acid, which are soluble in water.
The second stage (acid making stage): fermentation bacteria decompose small molecular compounds into acetic acid, propionic acid, butyric acid, hydrogen and carbon dioxide, and then convert them into acetic acid, hydrogen and carbon dioxide for methanogens to use.
The third stage (methanogenic stage): methanogenic bacteria colony, using the above three methanogenic bacteria to decompose and transform formic acid, acetic acid, hydrogen and carbon dioxide small molecular compounds to produce methane. The three stages of biogas fermentation are interdependent and continuous, maintaining a dynamic balance. In the initial stage of biogas fermentation, the first and second stages play the main role, but also the third stage. In the later stage of biogas fermentation, the three stages are carried out at the same time. After a certain period of time, maintain a certain dynamic balance and continue to produce gas normally.