Chapter 1　Introduction to Biogas

1.1　Biogas Origin & Nomenclature

Biogas fermentation is one of the most important elements of Material Circle in nature. Biogas is produced from the metabolized substances of anaerobic microorganisms, the origins are listed in Tab 1.1. In some ponds, manure pits and sewage which are rich in organic wastes, we can see gas bubbling to surface. When ignited, the gas can burn with a blue flame. Due to its origination in nature wetlands, we call this marsh gas or biogas. Methane bacteria are also found in some higher plants and animals, including the stomach of ruminants where biogas fermentation takes place. Through study of microbes in ruminants' stomachs, researchers have obtained knowledge concerning bacteria therein. There are many different types of biogas bacteria in ruminants' stomachs where methane and carbon dioxide are formed. In the ruminant stomach of a milk cow, there are 100 L of cellulose fermenting material, which by fermentation can produce more than 200 L of methane, which is primarily released during breathing.

Table 1.1　Origins & nomenclature of biogas