Anaerobic Digestion 1

As we all know, there is certain part of energy exists in the waste. To extract this part of energy, anaerobic digestion can be a choice. Anaerobic digestion is a phenomenon that some types of bacteria break down the biodegradable materials under specific requirement on the absence of oxygen. While the organic maters are decomposed, biogas like methane can be provided alternatively. In fact, anaerobic digestion has several hundreds years of history. It is started since Robert Boyle and Stephen Hale discovered the flammability of the gas generated while disturbing the sediment in 17th century. Due to its flammability as well as high heating value, the biogas generated during the digestion is considered as an alternative energy for fossil fuel. Also, the price for conventional fuels like oil has continued to rise, so biogas has the economically feasibility in the energy market. Since the certain types of microorganisms oxidize the organic wastes during anaerobic digestion, the size of the waste will be decreased as well. However, these species of microorganism cannot digest nonorganic components actually. So refuse preparation is important in this technology as well as in the incineration. Most of industries waste is not recommended to be dealt by anaerobic digestion, while sewage slurry is much more suitable in this case since it has a large fraction of organic constituents.

 Except the absence of oxygen, the proper operation of anaerobic digestion also requires other conditions including suitable moisture content, pH and alkalinity. The details of these factors are given below in the second section. The bacteria metabolize the glucose, amino acids and fatty acids to organic acids, and by products of carbon dioxide, hydrogen, ammonia and H2O. the amounts and types of organic acids produced vary and are not readily ascertained.