Bioethanolbased on (Lamy, 2004) is ethanol which is the main ingredient using plants andfermentation process. Ethanol or ethylalcohol (C2H5OH) is biodegradable, low toxicity, colorless,and non-polluted fluid when leaking. Ethanol is a high-octane fuel and canreplaced Pb (Lead), by mixing ethanol with gasoline it will oxygenate the fuelmixture so that it can perfectly burn and reduce exhaust gas emissions such ascarbon monoxide (CO). based on (Wiratmaja,2011) the plant for making bioethanolshould have a high content of starch. In Indonesia, is many cassava skin waste fromhousehold or industry, while cassava skin has a high content of about 25-30% ofstarch, this is very suitable as an alternative energy material. The steps for making bioethanol fromcassava skin is, first is preparation and drying process steps.
Peeled the cassava skin and cut them into smallpieces. Before cassava skin is cut, clean the cassava skin using fresh water. Afterthat, dried the cassava skin that has been chopped to a maximum water content 16%.
Then, put 25kg of dried cassava skin tostainless steel tank with capacity up to 120 liters, add 100 liters of water andheated it on 100oC for 30 minutes. This step is for make cassavaskin becomes porridge and thickens the porridge. After preparation and drying processis a saccharification and fermentation process,. Saccharification process isthe process of decomposing starch into glucose. And fermentation process is aanaerobic 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 Oncecool, add fungus (Aspergillus sp.).
Aspergillus sp. will break down starch into glucose. To decompose 100 liters ofcassava starch porridge need 10 liters of aspergillus sp. After decompositionprocess, cassava porridge becomes two layers, water and sugar. Then, stir backthe sugar starch, then place it in the fermentation tank. Fermentation processis using saccharomyces sp. Sealtightly fermentation tank to prevent contamination and saccharomyces work optimally. For make fermentation process maximal,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 lowerlayer is a protein precipitate, middle layer is ethanol, and top layer iswater. The result of the fermentation is called beer (contains 6-12% ethanol). Then,filter the ethanol layer through a one micron filter paper to filter out theprotein precipitate. Although it has been filtered, ethanol is still mixed withwater. To separate it, we need distillation process.
The way to distillation isheat a mixture of water and ethanol at a temperature 78oC orequivalent boiling point of ethanol. The ethanol gas is flowed through asubmerged 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 isrequired 99% or called dry ethanol. Therefore, an absorbent distillation isnecessary, 95% ethanol was heated at 100oC.
At this temperature,ethanol and water evaporate. The steam is passed into a pipe whose walls arezeolite or starchy. The zeolite will absorb the remaining moisture contentuntil 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.