Judul: Pembuatan Biopelet Dari Bungkil Jarak Pagar (Jathropa Curcas L.) Dengan Penambahan Sludge Dan Perekat Tapioka
Abstrak: Seed of jatropha (Jatropha curcas L) contains 60 % kernel (weight) and 40 % husk (weight). Its nucleus’s seeds contain 40 – 45 % oils that can be separated into jatropha oil either with mechanical or extraction way (Hambali et al. 2006). More than its 60 % component is an oil cake. The huge amount of oil cake can be used as a solid fuel such as Biomass Pellets (Biopelet). Biopelet has diameters 3 – 12 mm and 6 – 25 mm long. Biopelet is produced by continuous inlet dry materials that is pushed and pressed through steel ring that has particular holes. The pressing process produces solid materials that will be broken into specific size (Ramsay (ed) 1982). Jatropha oil cakes have a weakness as a solid fuel. It has no high heating value and its physic characteristic that has low binder. The addition of sludge in this research are expected to increase the heating value. Sludge can be used as an alternative heating resource. Binding problems can be solved by adding tapioca. Tapioca is used because the price is cheap. But it has a weakness, tapioca will decrease heating value on the product. Binding agents also produce smoke. Optimum adding of tapioca is not more than 5% (Sudrajat and Soleh, 1994). The most important parameter of Biomass fuel is heating value (Grover et al, (eds) 2002). Heating values implies energy that is binded on the fuel with standard from environment. The standard are temperature, water (liquid or vapor), CO2, O2, etc (Palz, 1985). This research starts with physic and burning characterizations of jatropha oil cakes. Biopelet produce in the pellets mill that has capacity 350 kg/ hour. Production held in PT Indofeed Bogor. Biopelet parameters test conducted at Laboratories of Biomass Energy and Chemistry, Forest Product Research and Development Center. The final step of this research is found the comparison of quality between biopelet jatropha oil cake with adding sludge and tapioca and biopelet jatropha oil cake without adding sludge and tapioca. Experimental design used in this research is using Random Complete Design with two factors (RAL factorial). The first is the addition of sludge treatment with three levels, which is, 2%, 4% and 6%, while the second factor is the addition of tapioca adhesive that also has three levels of treatment, which is 1%, 3% and 5%. From the results of the research obtained, although the results of interaction from two factors of treatment, the sludge and tapioca adhesive does not produce real difference, but with the combination can further improve value of the some expected parameters. Combination of sludge 6% and 3% tapioca, can increase heating value to 4914 Kcal / kg, meaning that the combination treatment can increase the heating value 5.62% of the value content from biopelet (control ). So also for bound carbon, a combination of sludge 6% and 1% tapioca can increase the level of bound carbon of 24.41% of the value content of carbon bound control, the combination treatment has value of carbon content of 20.59%. v The addition of sludge and tapioca
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Judul: Karakteristik Biopelet Limbah Ampas Tebu dan Batang Singkong
Abstrak: Limbah ampas tebu (bagasse) dan batang singkong merupakan biomassa yang berpotensi menjadi alternatif bahan bakar terbarukan untuk memenuhi kebutuhan energi yang kian meningkat. Penelitian ini bertujuan untuk menganalisis karakteristik biopelet dan menentukan formulasi biopelet terbaik dari campuran limbah ampas tebu dan batang singkong. Pembuatan biopelet menggunakan pelletizer tipe rotary dies dengan perbandingan komposisi bahan baku yaitu A1 (100% serbuk batang singkong), A2 (100% limbah ampas tebu), A3 (20% limbah ampas tebu : 80% serbuk batang singkong), A4 (80% limbah ampas tebu : 20% serbuk batang singkong), A5 (50% limbah ampas tebu : 50% serbuk batang singkong), A6 (65% limbah ampas tebu : 35% serbuk batang singkong), A7 (35% limbah ampas tebu: 65% serbuk batang singkong). Penentuan biopelet terbaik berdasarkan pembobotan dengan tingkat kepentingan parameter dengan bobot tertinggi hingga terendah yaitu nilai kalor, kadar abu, kadar zat terbang, kerapatan, kadar air, dan laju pembakaran. Formulasi terbaik dari campuran kedua bahan baku berdasarkan SNI 8675-2018 didapatkan dari perlakuan A5 dengan rata-rata hasil uji kerapatan sebesar 0,60 g/cm³, kadar air 8,29%, kadar zat terbang 77,63%, kadar abu 4,10%, kadar karbon terikat 9,98%, nilai kalor 17,40 MJ/kg, keteguhan 96,55%, laju pembakaran 3,57 kg/jam, serta suhu pembakaran 761°C., Sugarcane bagasse and cassava stems are biomass waste which have potential as alternative renewable fuels by converting it into biopellets. This research aims to analyze the characteristics of biopellets made from a mixture of sugarcane bagasse and cassava stems waste, and determine the best formulation based on SNI no 8765-2018. A rotary dies type pelletizer has been used to produce the pellets. Pellets formulation was represented by the ratio of raw material composition, they were A1 (100% cassava stem powder), A2 (100% sugarcane bagasse waste), A3 (20% sugarcane bagasse waste : 80% cassava stem powder), A4 (80% bagasse waste : 20% cassava stem powder), A5 (50% sugarcane bagasse waste : 50% cassava stem powder), A6 (65% sugarcane bagasse waste : 35% cassava stem powder), A7 (35% sugarcane bagasse waste : 65 % cassava stem powder). Determination of the best biopellets is based on the scoring with the level of lightness of the parameters with the highest to lowest score is calorific value, ash content, volatile matter content, density, moisture content, and combustion rate. The best formulation obtained from A5 composition (50% bagasse and 50% cassava stem) with average density of 0,60 g/cm³, water content of 8,29%, volatile matter content of 77,63%, ash content of 4,10%, bound carbon content of 9,98%, calorific value 17,40 MJ/kg, durability 96,55%, and combustion rate 3,67 kg/hour, combustion temperature 761°C.
Keyword: biomassa, biopelet, bagasse, batang singkong, pelletizer

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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