Judul: Inaktivasi Lipase Pada Biji Jarak Pagar  (Jatropha Curcas L.) Dengan Metode Pengukusan
Abstrak: Biodiesel is produced from trans-estherification process of vegetables oil with methanol and base catalyst. This process can be done if the free fatty acid content in oil is low. If the free fatty acid content is high, it can be taken care of with estherification process to convert some part of the free fatty acid to ester. However this process can make biodiesel production cost higher so it is not competitive enough with diesel fuel. Free fatty acid is produced from hydrolysis process of the oil by water and catalyzed by lipase enzyme. Lipase should be inactivated in order to prevent the increase of free fatty acid in post harvest handling. The objective of this research is to obtain the best steaming time to inactivate lipase in jatropha seeds. The jatropha seeds are steamed during 15, 30, 45, and 60 minutes at temperature of 100-110oC. The experiment design is completely randomized design with one factor, which is the steaming duration of jatropha seed (15, 30, 45, 60 minutes and control). This research is conducted with five times replications for every level of treatment. The parameters to be observed are oil yield, water content, free fatty acid content (FFA) and acid value. The analysis of variance (ANOVA) of oil yield at confidence level of 95% (α = 0,05) indicate that the duration of steaming made a significant effect on oil yield. The significance testing by Duncan test, show that every steaming duration treatment was different with the control (not steamed), but among steaming duration has no significant difference. The analysis showed that the steaming duration do not have a significant effect to the water content in the oil. The water content in oil on each treatment range between 0,0722% to 0,0816%. The steaming duration has a significant effect on increasing rate of FFA content. Increasing rate of FFA content on the steaming duration of 60 and 45 minutes do not have significant effect and both duration treatments have significant difference with control. Increasing rate of FFA content on the steaming duration of 30 and 15 minutes do not have significant effect and both of them do not have significant effect with control as well as 45 and 60 minutes steaming duration, with a tends that the longer of steaming duration the reduce of the FFA content increasing rate. The steaming duration has a significant effect on acid value increasing rate. Acid value increasing rate on the steaming duration of 45 and 60 minutes have significant differences with control. On steaming duration of 15 and 30 minutes have no difference neither with control nor with steaming duration of 45 and 60 minutes. The conclusion from this research is steaming process of 45 minutes was the best lipase inactivation. Steaming process at the same temperature and duration can also produce higher oil yield compared to seed without steaming.
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Judul: Kajian Proses Produksi Biodiesel Melalui Transesterifikasi in situ Biji Jarak Pagar (Jatropha curcas L.) Pada Berbagai Kondisi Operasi
Abstrak: Biodiesel production is generally carried out through several stages of process. They are oil extraction, oil purification, and oil transesterification. Several steps that must be passed in the biodiesel production causing low efficiency and high energy consumption, resulting in high cost of biodiesel production. Therefore, it is necessary to develop a process that simplify the steps in biodiesel production, more efficient, low cost and low energy consumption, also be able to produce high quality of biodiesel through in situ transesterification. This study purposes to investigate on in situ transesterification of Jatropha curcas L. under various operating condition by studying the influence of temperature, stirring speed, and reaction time on the yield and quality of biodiesel. In situ transesterification of Jatropha seeds was carried out under the following process conditions : the moisture content of Jatropha seeds less than 1%, the particle size of 35 mesh, the methanol to hexane to seeds ratio of 6:1:1 (v/v/w), and the KOH concentration of 0.075 mol/L methanol. Operating conditions of in situ transesterification was varied at temperature of 40, 50, and 60ºC, reaction time of 3, 4, and 5 hours, and mechanical stirring of 700, 800, and 900 rpm. Analysis of variance showed that temperature, stirring speed, and reaction time did not significantly affected the yield and viscosity of biodiesel. Temperature, reaction time, and interactions between temperature, stirring speed, and reaction time significantly affected acid value of biodiesel. Temperature and interaction between temperature and stirring speed significantly affected saponification value and ester value of biodiesel. The experimental results showed that in situ transesterification conditions which recommended for commercial scale was at temperature of 40ºC, mechanical stirring of 700 rpm, and reaction time of 3 hours (A1B1C1). That condition was choosen because this condition used low energy than other operating condition. This was also supported by the results of statistical analysis showed that the yield and viscosity of biodiesel were not significantly different at all operating conditions, and biodiesel’s characteristics meets Indonesian Biodiesel Standard. The value of acid value, saponification value, ester value, and viscosity at A1B1C1 are 0.49 mg KOH/g, 201.36 mg KOH/g, 200.87 mg KOH/g, and 3.49 cSt.
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Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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