| Abstrakt: |
Biodiesel has become a subject which increasingly attracts worldwide attention because of its environmental benefits, biodegradability and renewability. Negative environmental consequences of fossil fuels and concerns about petroleum supplies have spurred the search for renewable transportation biofuels. To be a viable alternative, a biofuel should provide a net energy gain, have environmental benefits, be economically competitive, and be producible in large quantities without reducing food supplies. We use these criteria to evaluate, through lifecycle accounting, ethanol from corn grain and biodiesel from soybeans. Ethanol yields 25% more energy than the energy invested in its production, whereas biodiesel yields 93% more. Compared with ethanol, biodiesel releases just 1.0%, 8.3%, and 13% of the agricultural nitrogen, phosphorus, and pesticide pollutants, respectively, per net energy gain. Relative to the fossil fuels they displace, greenhouse gas emissions are reduced 12% by the production and combustion of ethanol and 41% by biodiesel. Biodiesel also releases less air pollutants per net energy gain than ethanol. These advantages of biodiesel over ethanol come from lower agricultural inputs and more efficient conversion of feedstocks to fuel. Neither biofuel can replace much petroleum without impacting food supplies. Even dedicating all U.S. corn and soybean production to biofuels would meet only 12% of gasoline demand and 6% of diesel demand. Until recent increases in petroleum prices, high production costs made biofuels unprofitable without subsidies. Biodiesel provides sufficient environmental advantages to merit subsidy. Transportation biofuels such as synfuel hydrocarbons or cellulosic ethanol, if produced from low-input biomass grown on agriculturally marginal land or from waste biomass, could provide much greater supplies and environmental benefits than food-based biofuels.Biodiesel production typically involves the transesterification of a triglyceride feedstock with methanol or other short-chain alcohol. This paper presents a study of transesterification of various vegetable oils, sunflower, soybean, olive, and waste cooking oils, with the alkaline catalyst.Transesterification reaction plays an important role in converting vegetable oil or used oil into biodiesel. Reaction process may result in low yield, due to the conversion stage between oil and methanol takes place is not perfect and can lead to low-quality of biodiesel. In the transesterification reaction; mass of catalysts, mass of methanol, FFA value, reaction temperature, reaction time, and stirring speed is a major factor determining the quality of biodiesel produced. Reactions were carried out at 65°C temperature gives lower yield of methyl ester. Using the stirrer speed is too high will cause the saponification reaction which reduce the yield generated. Use stirring speed is too high will cause the saponification reaction which will reduce the yield generated. The results of these three variables biodiesel, has met SNI the standard and ASTM D 6751 for testing density, viscosity, cetane index, and flash point. [ABSTRACT FROM AUTHOR] |
