Anaerobic Digestion (AD) is a process in which the bio-degradable products are processed and are broken down into smaller biogas materials. This biogas consists of elements like Methane and Carbon dioxide that can be used for the manufacturing of electricity. For the Anaerobic Digestion to occur the products have to be free of oxygen and they have to satisfy certain conditions such as Temperature, Moisture and pH level. The favorable temperate for this to occur is between 30-40 degree Celsius and 60-80 degree Celsius.
Need for the process
The Anaerobic Digestion is usually done to convert the raw materials such as wood waste into good biomass fuels. Biomass is one of the eco-friendly ways of producing electricity and it requires cheap, renewable source of fuel that can be produced by the Anaerobic Digestion process.
Various types of Anaerobic Digesters
There are different types of digesters which produce heat from the raw materials namely Cover Lagoon, Complete Mix and Plug Flow.
The complete mix is a large circular container that can process wastes with a solid mix of only around 10%. It can operate well in any temperature and it could produce heat for more than 20 days on a row. Since it does not require any maintenance or repair, it is one of the most preferred types of Anaerobic Digesters.
The Plug Flow digester is usually built underground. Each day, a particular amount of manure is send through it. It also contains an air tight compartment. It can process manure with no more than 15% of solid mix. So, what happens when you add new manure the other day is, the old manure goes into the trough and gets processed while the new manure waits for the next day's manure to push it down. This way, the process continues to go on until you stop feeding the digester.
Anaerobic Digestion of Renewable Biomass
The third type is Cover Lagoon and it is basically the same what its name suggests. So, first you take a cover like membrane made up of fabric and place it in the lagoon. Then you process the bio-waste and the heat produced from it is absorbed by the cover. This process is not suitable for bio-waste that contains solid materials but it is the most preferred for liquid waste.
The Cover Lagoon type is rather simple and cost effective than the two other types but it has one disadvantage that is the production is dependent on the temperature. So, in summer when the lagoons are heated, the production is 35% more than it is in winter. Another thing that you should note is the fact that it at least takes 2-3 years for the Lagoon to steady and produce Biogas in a consistent manner.
Why AD is needed in this World?
The production of Eco-Friendly green energy, utilization of agricultural waste and production of many byproducts has changed the face of Anaerobic Digestion. It is becoming one of the top practices around the world and many countries have well developed AD structures with them. Over 5000 MW of energy is produced in Asia alone from AD process. If this continues, AD will become one of the top practices of producing electricity around the world.
