(best examples and good practices) on household organic waste ...

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wastewater treatment plant to be energy efficient more energy production is
usually needed <strong>and</strong> if there is none energy from power plants is used.
Another important use of the AD process is in food industries <strong>and</strong> agro
industries. A large number of AD plants are pre-treating organic loaded
industrial waste waters from beverages, food, meat, pulp <strong>and</strong> paper, milk
industries etc. before the final product is disposed. The biogas as in most of the
AD processes is used to generate energy for the whole process. The
environmental benefits <strong>and</strong> the high costs of alternative disposal will increase
the application of this process in the future.
Finally, the treatment of source separated organic fraction of solid household
waste is one of the areas with a large biomass potential all over the world
nowadays. Many plants operate today with a total capacity of almost five
million tones <strong>and</strong> more. The main effort of this application is the reduction of
the organic waste flow to other treatment possibilities such as incineration or
l<strong>and</strong>fill which are considered as 2 of the treatment methods which have a great
negative effect to the environment. Some AD treatment of organic household
waste takes place at the manure based co-digestion plants. AD treatment of
household waste though has negative impacts too that is why it needs to be
improved <strong>and</strong> developed more in the future. (Christopoulos.,2005)
2.2.3. Digestion Process Description
The anaerobic digestion stabilization of the organic material is accomplished by
a consortium of microorganisms working together. The four-steps of the
digestion process are: hydrolysis, acidogenesis, acetogenesis, <strong>and</strong>
methanogenesis (Figure 8.):
1. Large protein macromolecules, fats <strong>and</strong> carbohydrate polymers (such as
cellulose <strong>and</strong> starch) are broken down through hydrolysis to amino acids, longchain
fatty acids, <strong>and</strong> sugars.
2. In acidogenesis, the products from the previous process are been fermented
to form three, four, <strong>and</strong> five-carbon volatile fatty acids, such as lactic, butyric,
propionic, <strong>and</strong> valeric acid.
3. In acetogenesis, bacteria consume these fermentation products <strong>and</strong> generate
acetic acid, carbon dioxide, <strong>and</strong> hydrogen. (NSWAI., 2010)