Anaerobic digestion means the breaking down of the organic wastes and other materials through natural means. This breaking down occurs due to anaerobic respiration and results in the production of methane, fertilizers and carbon dioxide gas. The breaking of waste materials may either happen through natural means, or it can be done manually in an anaerobic digester specially built for this purpose.
A digester where anaerobic digestion will take place is usually a sealed vessel or vessels where the bacteria can act without the need of oxygen. The organic waste materials should be mixed fully and kept warm, generally equivalent to the blood temperature of the human body. The process of digestion starts with anaerobic respiration and bacterial hydrolysis of the organic waste materials that starts to break these into organic polymers and carbohydrates, which are insoluble. The other bacteria that is produced, takes over and converts the sugar and amino acids into carbon dioxide, ammonia, organic acids and hydrogen. The Acetogenic bacteria in the materials then take over and convert the organic acids into acetic acid.
During the process of digestion through anaerobic respiration, biogas, which is actually the name given to a mixture of gasses that gets formed during anaerobic digestion of the wastes, is produced. This biogas is composed of 70 percent methane and 30 percent of carbon dioxide. The biogas that is obtained can be used in fixed engines to produce electricity. However, this gas is not suitable to be used as a fuel for vehicles.
Anaerobic digestion is useful for producing renewable energy, because during the process of digestion that takes place through anaerobic respiration, the gas (biogas) that is produced is very rich in methane and carbon dioxide and is highly suitable for producing alternative sources of energy and can effectively reduce our dependence on fossil fuels. The digestate, which is produced, is very rich in nutrients and can also be used in the place of chemical fertilizers.
Another byproduct is Biomethane, also known as the Renewable Natural Gas. Removing carbon dioxide as well as other gases produces this gas. This process is known as the upgrading of gas. The Biomethane Gas obtained is similar to the natural gas. The only difference is that Biomethane Gas can be obtained very quickly, whereas, natural gas is produced through natural means after millions of years.
Biomethane Gas can be used in place of natural gas. It can be easily used for heating, cooing and can also be used as a source for the production of a variety of chemicals, hydrogen or fertilizers. This gas is used as a fuel for vehicles.
Anaerobic digesters can also be used effectively for waste management, as the anaerobic respiration that is induced during the digestion process also reduces the emission of harmful gases into our atmosphere. This type of digestion is specially suited to organic material wastes that are wet and are found in the sewage systems.
Most of the organic waste materials can be easily processed with anaerobic digestion. These materials include waste materials such as waste paper, leftover food, animal waste, sewage, grass clippings and the host of other materials that can be digested through anaerobic respiration.