There are several methods which could be considered for pollution abatement in distilleries. The two important methods are aerobic and anaerobic. Unfortunately, due to economic reasons, the aerobic method does not find much application, especially, when the total amount of organic load to be removed is fairly high.
Efforts have also been made for the development of a few suitable processes for the recovery of potash as well as for the manufacture of Torula yeast, and both have been briefly mentioned in The possibility of using distillery effluents for irrigational purposes has also been indicated in Considering that anaerobic processes have proved economically viable, the details for the same have been given.
A critical evaluation of different techniques which could be employed for pollution control in distillery clearly indicates that practically all the methods involve a considerable amount of both capital as well as running expenditure without any equivalent return.
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Considering the growing concern for the development of suitable renewable resources of energy, in view of the global energy crisis, it is considered practical to opt for the generation of methane out of all biomaterial including distillery effluent.
The methane gas obtained could be used either as a fuel gas or as a raw material for the petrochemical industry. Some of its characteristics are enumerated below:
Methane Gas as Fuel:
1. It is a non-knocking fuel with a very high compression ratio.
2. It is a clean engine fuel.
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3. It has the advantage of getting well distributed in the internal engine and shows no tendency to dilute the lubricating oil.
4. It burns with a non-luminous flame in air, forming carbon dioxide and water.
5. It emits an exhaust gas with extremely low carbon monoxide content.
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Methane Gas as a Raw Material for Petrochemical Industry:
1. It can be used in the production of ammonia and urea (used as fertilizers).
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2. It is used in the formation of valuable derivatives, viz., methyl chloride, methyl dichloride, chloroform and carbon tetrachloride.
3. It can be used in the production of methanol.
4. It can be used in the preparation of carbon black.
5. It can be used as a source of hydrogen for synthesis gas (manufacture of petrol).
Anaerobic Treatment of Distillery Effluent:
Anaerobic treatment of distillery effluent is a biochemical process, caused by the facultative and anaerobic group of bacteria which converts the organic substance into volatile acid and methanogenic bacteria, and, then, converts the volatile acid into carbon dioxide and methane.
Methanogenic bacteria are strictly anaerobes. They thrive best when the pH is close to neutral but fail to thrive at pH 6. The methane bacteria are heterogenous in cellular morphology- some are rods, others cocci, and others in clusters of cocci known as sarcina.