Bioethanolbased on (Lamy, 2004) is ethanol which is the main ingredient using plants andfermentation process. Ethanol or ethylalcohol (C2H5OH) is colorless, biodegradable, low toxicity,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, peeled the cassava skin and cut them into small pieces. Beforecassava skin is cut, clean the cassava skin using fresh water.
After that, driedthe cassava skin that has been chopped to a maximum water content 16%. The purposeof this step is to more durable so the bioethanol maker can save as rawmaterial reserves. Then, put 25kg of dried cassava skin to stainless steel tankwith capacity up to 120 liters, add 100 liters of water and heated it on 100oCfor 30 minutes. This step is for make cassava skin becomes porridge andthickens the porridge. After that, cooling the cassavathick porridge and put that into the sacchafrification tank.
Saccharification isthe process of decomposing starch into glucose. Once cool, add fungus (Aspergillus sp.). Aspergillus sp. willbreak down starch into glucose. To decompose 100 liters of cassava starchporridge need 10 liters of aspergillus sp. After decomposition process, cassavaporridge becomes two layers, water and sugar.
Then, stir back the sugar starch,then place it in thefermentation tank. Fermentation process is using saccharomyces sp. Seal tightly fermentation tank to preventcontamination and saccharomyces workoptimally. Fermentation process is does not require oxygen (anaerobic).
Foroptimal fermentation, keep the temperature at 28-32oC and with pH4,5-5,5. After 2-3 days, the starch solutionturns into 3 layers. The lower layer is a protein precipitate, middle layer isethanol, and top layer is water.
The result of the fermentation is called beer(contains 6-12% ethanol). Then, suck an ethanol layer with a plastic hosethrough a one micron filter paper to filter out the protein precipitate. Althoughit has been filtered, ethanol is still mixed with water. To separate it, weneed distillation process. The way to distillation is heat a mixture of waterand ethanol at a temperature 78oC or equivalent boiling point ofethanol. The ethanol gas is flowed through a submerged tube so it becomescondensed 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.