Biogas fermentation refers to a variety of organic compounds decomposed and transformed by various types of biogas microbial, and eventually generate biogas process in certain moisture, temperature and anaerobic conditions.
Biogas is a mixture of gas, the main component of which is methane, occuping 50-70% of the total volume of gas, followed by 30-40% of carbon dioxide. In addition, it contains a small amount of gas such as nitrogen, hydrogen, oxygen, ammonia, carbon monoxide, and hydrogen sulfide. Methane, ammonia and carbon monoxide are flammable gas, which we mainly use burning to get energy.
Biogas fermentation process can be generally divided to three stages: liquefaction, acid yielding and methane-producing.
The first stage (liquefaction): organic substances (carbohydrates, protein, fat, etc.) by the effect of fermentation bacteria (cellulose decomposing bacteria, protein decomposing bacteria, fat decomposition bacteria, etc.) hydrolyzing the polysaccharide into simple sugars, protein into peptides and amino acids, fat hydrolysis into glycerol and fatty acids, and further degraded into various lower organic acids, such as acetic acid, propionic acid, Yichun etc. Meanwhile, it also generates hydrogen and carbon dioxide.
The second stage (acid yielding): Mainly by hydrogen-producing bacteria and acetic acid bacteria decomposing propionic acid, acetic acid and ethanol forms hydrogen and acetate, or occasionally produces carbon dioxide.
The third stage (methane-producing phase): Methanogenic bacteria decomposes of acetic acid and alcohols to form methane and carbon dioxide, or make use of hydrogen to restore carbon dioxide to form methane, or converse formic acid to form methane.
The three stages of biogas fermentation are interdependent and continuously proceed to maintain dynamic balance. In the early stage of biogas fermentation, the first and second stages take the main role, also the third stage takes places; in later stage, the three stages take place at the same time, to a certain time maintaining a dynamic balance to continue produce biogas normally. |