Definition suitable as an alternative energy material. The steps

of bioethanol based on (Lamy, 2004) is ethanol which is the main ingredient using
plants and fermentation  process. Ethanol
or ethyl alcohol (C2H5OH) is biodegradable, low toxicity,
colorless, and non-polluted fluid when leaking. Ethanol is a high-octane fuel and
can replaced Pb (Lead), by mixing ethanol with gasoline it will oxygenate the
fuel mixture so that it can perfectly burn and reduce exhaust gas emissions
such as carbon monoxide (CO). And based on (Wiratmaja,2011) the plant for
making bioethanol should have a high content of starch. In Indonesia, is many
cassava skin waste from household or industry, while cassava skin has a high
content of about 25-30% of starch, this is very suitable as an alternative
energy material.  

            The steps for making bioethanol from
cassava skin is, first is preparation and drying process steps.  Peeled the cassava skin and cut them into small
pieces. Before cassava skin is cut, clean the cassava skin using fresh water. After
that, dried the cassava skin that has been chopped to a maximum water content 16%.
 Then, put 25kg of dried cassava skin to
stainless steel tank with capacity up to 120 liters, add 100 liters of water and
heated it on 100oC for 30 minutes. This step is for make cassava
skin becomes porridge and thickens the porridge.

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            After preparation and drying process
is a saccharification and fermentation process,. Saccharification process is
the process of decomposing starch into glucose. And fermentation process is a
anaerobic or does not require oxygen and the result of fermentation process is ethanol.
Cooled the cassava thick porridge and put that into the sacchafrification tank.
When cassava thick porridge cool, add fungus (Aspergillus sp.). Aspergillus sp. will break down starch into glucose.
To decompose 100 liters of cassava starch porridge need 10 liters of
aspergillus sp. After decomposition process, cassava porridge becomes two
layers, water and sugar. Then, stir back the sugar starch, then place it in the
fermentation tank. Fermentation process is using saccharomyces sp. Seal tightly fermentation tank to prevent
contamination and saccharomyces work
optimally. For optimal fermentation, keep the temperature at 28-32oC
and with low pH or at pH 4,5-5,5.

            Fermentation process about 2-3 days,
and then after 2-3 days the starch solution turns into 3 layers. The lower
layer is a protein precipitate, middle layer is ethanol, and top layer is
water. The result of the fermentation is called beer (contained 6-12% ethanol).
Then, filter the ethanol layer through a one micron filter paper to filter out
the protein precipitate. Although it has been filtered, ethanol is still mixed
with water. To separate it, we need distillation process. The way to
distillation is heat a mixture of water and ethanol at a temperature 78oC
or equivalent boiling point of ethanol. The ethanol gas is flowed through a
submerged tube so it becomes condensed and returns into liquid ethanol.

            The distillation product is 95%
ethanol and is not soluble in gasoline. In order for the herbs, ethanol is
required 99% or called dry ethanol. Therefore, an absorbent distillation is
necessary, 95% ethanol was heated at 100oC. At this temperature,
ethanol and water evaporate. The steam is passed into a pipe whose walls are
zeolite or starchy. The zeolite will absorb the remaining moisture content
until 99% of the ethanol is ready to be mixed with gasoline. Ten liters of 99%
ethanol, requires 120-130 liters of beer produced from 25kg dried cassava.



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