Technology For Production Of Ethanol

The technology for manufacture of ethanol (dehydrated/Anhydrous
Alcohol) involves special processing of alcohol/rectified spirit.
There are three commercial routes for the manufacture of dehydrated Ethanol from rectified spirit/ alcohol. These are as follows

Azeotropic Distillation Technology
*Molecular Sieve Technology*
Membrane Technology


Azeotropic Distillation Technology

The technology for ethanol production from rectified spirit using azeotropic distillation is well established in India as a number of plants exist in the country based on this technology. This technology involves a distillation system employing benzene as the third component has been in use in India since World War II.


The initial capital cost (project cost) for this technology is lower than the molecular sieve technology but the cost of production is higher because of higher energy consumption and higher consumption of benzene or other similar third component such as cyclohexane. It is essential to mention here that the third component may cause air pollution as well as water pollution especially components such as benzene are known to be highly carcinogenic.

Molecular Sieve Technology

This is the most commercially popular, financially viable and environmentally friendly technology, which has emerged, in the late 1980s. This is a clean technology in which the water is removed by molecular sieves and dehydrated alcohol/ethanol is obtained. The dehydration process using this technology can be carried out either in liquid phase or vapour phase. For smaller plants and for removing less water content liquid phase technology is adequate and is often used.
Smaller plants using this liquid phase have been set up in the past.
However, for larger plants where ethanol is being used for blending with petrol, the globally preferred technology is based on vapour phase dehydration of ethanol.


In this technology, although, the capital cost is higher than azeotropic distillation, the cost of production is lower. Another major advantage is that it does not cause any pollution especially water pollution, as is the case with azeotropic distillation technology, in which case, benzene and other toxic chemicals pose a health hazard.

Membrane technology

Membrane technology has not been successful at commercial scale as the cost of membrane is high and its life is reported to be very short.
This leads to high cost of production. However, technologies using newer type of membranes which will have a relatively longer life, and therefore lower cost of production, are reported to be under development in developed countries. This technology does not have a proven track record yet.

Raw Materials/Substrates



Alcohol can be manufactured from a large number of raw materials, which fall into three main categories



Sugar based



Starch based



Cellulose based


Sugar Based

In this category the main crops are sugar cane (sugar cane juice & molasses), sugar beet (beet juice and molasses), sweet sorghum,

Starch Based

All types of grain including wheat, rice, corn (maize), barley, malt, millet etc. are included in this. In addition, tubers such as potatoes, cassava (tapioca) etc. are also starch based.

Cellulose Based

This category includes agro-waste, agro- residues, bagasse, rice husk, straw, groundnut shells, wood chips, sawdust, organic municipal waste etc.