Bioethanol is alternative fuel to gasoline that made from renewable resources. There is three kind of resource: sugar base (sugar cane, molasses, sugar bit, etc), starch base (corn, cassava, sago, etc), and cellulose base (wood, rice musk, grass, etc).
Sugar base bioethanol is the most simple process. Sugar source can directly fermented by yeast to produce ethanol. Brazil produce ethanol from molasses, side product from sugar cane processing. Brazilian have perfect geographical condition to expand their cane farm. Cane should be farmed at sun rich land, mostly country at earth equator suitable for cane farm.
Difference with Brazil, US produce ethanol from starch base. US climate is not suitable for cane farm. They produce ethanol mostly from corn. There is two step corn to ethanol, liquefaction and fermentation. Liquefaction aimed to convert starch to sugar, and the next step (after liquefaction) is mostly same with sugar base ethanol.
Cellulose base bioethanol is the most complex and difficult technology since there is quite hard to crack cellulose into more simple molecule like carbohydrate or starch. Some scientist study to find more simple way to reduce molecular length by acidification. Cellulose treated with strong acid to produce simpler starch molecule, this process also produce some by product like carbon, carbon dioxide, volatile matter, etc. Simpler starch molecule then seeded to liquefaction and fermentation process to produce ethanol. Even though it is the most difficult, but cellulose base ethanol can be one of solution to produce cheap environment friendly fuel since its can convert cellulose from wood waste, farm waste, etc to ethanol.
Indonesia have much source for ethanol. Indonesia have tropical climate that suitable for cane farm, Indonesia climate also suitable produce starch or cellulose. The only problem is its productivity. Cane should have around 12% yield to sugar cane, but in Indonesia it is only 6-7%.
Other problem to develop renewable energy in developing country is competition with food. Producing ethanol from starch will disturb food supply and demand. The effect is starch for food price is increasing because starch demand increasing. This effect can be shown at crude palm oil case. Before hegemony of renewable energy, crude palm oil price is only 200-300 USD per tons, but now CPO price can reach up to 900 USD per tons. This problems can be solved with government regulation in market quota.
Bioethanol from cassava
Cassava root is one of source for starch. Cassava plant can growth well, even without any maintenance and fertilizer, at tropical climate, like in Indonesia. Cassava plantation can be found in Lampung, around 200 km from Jakarta.
Cassava can be converted to ethanol by fermentation. Cassava starch slurry must be treated with enzymatic process to convert most of starch to fermentable sugar. This process called liquefying. In this process, cassava slurry is heated to remove any microbial contaminant, then add liquefying enzyme to convert starch to sugar. Starch will be very viscous at high temperature, called gelatination, so viscosity reduction enzyme is needed.
Converted starch then can be easily to fermented to produce ethanol. Fermented sugar (ethanol) can be purified in distillation and dehydration process to produce fuel grade ethanol.
Ethanol fuel also very clean to burn and have renewable resource. CO2 from combustion of ethanol process came from CO2 in the atmosphere that converted into starch by cassava or other starch source plant, so burning bioethanol will not affected to CO2 balance in the atmosphere. That why bioethanol is called environment friendly fuel.
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