anaerobic digestion presentazione si
Post on 07-May-2015
Embed Size (px)
2. ANAEROBIC DIGESTION
Anaerobic digestion is a series ofmicrobiologicalprocessesthat convert organic compounds to methane. Anaerobic digestion con take place only in an air tight chamber kept at a temperature not lower than 20 C. The maximum temperature for a digester is 65C: such a high temperature reduces processing time and digester dimensions, but the digestion is more prone to upset, so it requires close control.
3. The digestion takes place thanks to four different types of bacteria which operated at different stages of the digestion process:
4. HYDROLYTIC BACTERIA
The hydrolyticbacteria break down complex organic waste into sugars and amino acids.
5. Hydrolytic bacteria form a variety of reduced end-products from the fermentation of a given substrate. One fundamental question which arises, concerns the metabolic features which control carbon and electron flow to a given reduced end-product during pure culture, and mixed methanogenic cultures of hydrolytic bacteria.
6. FERMENTATIVE BACTERIAThe fermentative bacteria turn sugars and amino acids into organic acids.
7. Fermentation bacteria are anaerobic, but use organic molecules as their final electron acceptor to produce fermentation end-products. Bacteria are a large group of unicellular or multi-cellular organisms which can tolerate different temperatures. While most bacteria have a temperature optimum of between 20 to 30C, there are some which prefer higher temperatures (50 to 55C) and those with colder temperature optima (15 to 20C).
8. ACIDOGENIC MICRO ORGANISMS
The acidogenic micro organismconverted organic acids into hydrogen, carbon dioxide and acetic acid.
9. Acidogenesis is a biological reaction where simple monomers are converted into volatile fatty acids ; is one of the main reactions of this stage, in this, the intermediary metabolites produced are metabolized to acetate, hydrogen and carbonic gas by the groups of bacteria.
10. METHANOGENIC BACTERIA
Produce biogas from acetic acid, carbon dioxide and acetate.
11. Methanogens are microorganisms that produce methane as a metabolic byproduct in anoxic conditions. They are common in wetlands, where they are responsible for marsh gas, and in the guts of animals such as ruminants and humans, where they are responsible for the methane content of flatulence.
12. 13. There a three traditional main types of digester , and more recently developed one which is promising but not yet largery tested:
- They have different building;
14. Operating and maintaining cost; 15. Each one can digester manure with a specific total solid content.