No abstract

Bioetanol merupakan bahan bakar alternatif yang sangat berpotensi menggantikan BBM. Bahan baku bioetanol dapat berasal dari alga Spirogyra sp yang jarang dimanfaatkan. Karbohidrat tinggi yang terkandung dalam alga Spirogyra sp sangat berpotensi untuk dikembangkan menjadi etanol melalui proses kimia dan biologi. Penelitian ini dilakukan dengan beberapa tahapan yaitu hidolisis asam menggunakan H2SO4 0,2 M, fermentasi dengan bantuan mikroorganisme Saccharomyses cereviseae secara anaerob, dan distilasi. Penelitian ini bertujuan untuk mengetahui waktu dan kadar yeast optimum pada proses fermentasi. Pada proses fermentasi, digunakan variasi waktu fermentasi 3, 4, 5,  dan 6 hari serta variasi kadar khamir 0,5%; 0,75%; 1%; 1,25%; 1,5%; dan 1,75% dari volume filtrat. Hasil fermentasi dari masing-masing percobaan dianalisa untuk mengetahui kadar etanol dengan menggunakan perhitungan secara stoikiometri.Waktu optimum yang didapat dalam penelitian ini adalah 5 hari dan kadar khamir optimum yang didapat adalah 1 % volume filtrat. Kondisi operasi saat fermentasi yaitu pada pH 4,5 dan suhu dijaga pada 300C. Mol alkohol yang terbentuk sebanyak 0,0613 mol. Bioethanol is an alternative fuel that has potential to replace the oil fuel. The bioethanol feedstock can be derived from the green algae Spirogyra sp that is rarely exploited. High carbohydrates content in the Spirogyra sp algae is highly potential to be developed into ethanol through chemical and biological processes. This research is done through several stages: preparation of raw material, hydrolysis using sulfuric acid 0,2 M, and fermentation using Saccharomyses cerevisiae in an anaerob condition. The objective of this study is to find out the optimum reaction time and optimum quantity of Saccharomyses cerevisiae in the fermentation process. Variations of reaction time and yeast quantity are applied; those are 3, 4, 5 and 6 days for reaction time, and 0,5%; 0,75%; 1%; 1,25%; 1,5%; and 1,75% for yeast quantity. The stoichiometric calculation is used to analyse the result of this experiment. The result shows that the optimum duration for the fermentation is 5 days and the optimum quantity of yeast is 1% by weight. The condition of fermentation process must be held in pH of 4,5 and temperature of 30oC. The produced alcohol in those condition is 0,0613 mol.

Indonesia's rapid population growth means that power demand will continue to rise year after year. Indonesia's growing population has resulted in an increase in restaurants, including Chinese food restaurants. As the number of restaurants grows, so does the amount of waste produced. Microbial Fuel Cells (MFC) that create electrical energy are one solution to this challenge. The study aimed to explore the utilization of MFC systems for power generation. It measured the performance of MFC in liquid waste in generating electrical value by utilizing a series of electrode types, particularly Aluminum (Al), Copper (Cu), Zinc (Zn), and Lead (Pb), and a blend of the four types of electrodes. The measured electrical value indicated that MFC can produced the high electrical voltage value was the pair of zinc (anode) and copper (cathode) of (0.863 V) and then the highest electric current value is 0.14 mA with electrode Cu and Zn. The maximum power density is 0.00464 W/m2 using a combination of Zn/Cu electrodes and then electrical energy with highest value is 0.75168 J with Zn/Cu.

Potensi sumber daya batubara di Indonesia sangat melimpah. Namun, cadangan batubara tersebut pada umumnya termasuk batubara peringkat rendah dengan kadar air yang tinggi. Untuk mengatasi kadar air, salah satu teknologi yang telah dikembangkan saat ini ialah slurry dewatering yaitu pemanasan dengan menambahkan zat aditif berupa minyak residu. Proses slurry dewatering dilakukan dengan mencampurkan batubara ukuran 35 mesh seberat 100 gr ke dalam minyak goreng bekas dan minyak tanah pada perbandingan berat sebesar 1 : 1 : 1 , 1 : 1 : 0,5 ,dan 1 : 0,5 : 0,5. Campuran dipanaskan pada suhu 120 o C, 130 o C, 140 o C, 150 o C, dan 160 o C. Selanjutnya dilakukan pengadukan dengan kecepatan putaran 500 rpm dengan waktu 1,5 jam. Hasil slurry yang didapat dari proses tersebut dimasukan ke dalam centrifuge untuk memisahkan cairan dengan padatannya. Kemudian setelah didapatkan hasil optimal dilakukan percobaan kembali pada suhu 170 o C dan 180 o C. Hasil penelitian yang paling optimum didapatkan pada perbandingan batubara, minyak goreng bekas dan minyak tanah 1 : 1 : 1 dan suhu operasi 160 o C. Hasil analisa awal kadar air batubara sebesar 13,09 % dan nilai kalor sebesar 5554,36 kal/g. Dengan proses dewatering yang dilakukan pada penelitian ini, diperoleh hasil analisis akhir kadar air batubara sebesar 0,61 % dengan nilai kalor 7391,09 kal/gr. Data menunjukan penurunan kadar air batubara Jorong, Kalimantan Selatan mecapai 95,34% dan kenaikan nilai kalori sebesar 24,85%. Kata Kunci: batubara; slurry dewatering; zat aditif; uprgading brown coal; minyak residu ABSTRACT: Indonesia has a very abundant coal deposit. However, type of coal deposit is in a low rank coal quality with high water content. To overcome that problem, one of the technologies is called slurry dewatering which the coal are being heated with adding residue oil as additives. The procedure of this process is by mixing 100 grams of coal that have size around 35 mesh with residue oil, and kerosene at t hratios of 1:1:1 ; 1:1:0,5 ; and 1:0,5:0,5. The mixture are being heated at 120 o C, 130 o C, 140 o C, 150 o C, and 160 o C, with stirring of 500 rpm for 1,5 hours. Slurry formed are then transferred to centrifugation to separate liquid and the solid. After the optimum result obtained, the experiment are conducted at 170 o C and 180 o C. The optimum result happened at 1:1:1 ratio and the temperature at 160 o C. The initial water content at coal is 13,09% with heating value 5554,36 cal/g. After dewatering process are conducted, the water content is reduced to be around 0,61 % with heating value 7391,09 cal/g. Data shown that the declined water content from Jorong, South Kalimantan coal is around 95,34% and the increased of heating value is 24,85%.

This research aims to protect Digital Elevation Model (DEM) data from piracy or counterfeiting. An invisible watermark inserted into the data, which will not considerably change the data value, is necessary. The proposed method involves the use of the two-dimensional discrete cosine transform (2D DCT), a combination of 2D DCT and discrete wavelet transform (DWT), and two-dimensional discrete Fourier transform (2D DFT) in the frequency domain. The data used include a National DEM file downloaded from the geoportal of the Geospatial Information Agency (Badan Informasi Geospasial—BIG). Three files represent mountainous, lowland/urban, and coastal areas. An “attack” is also conducted on the watermarked DEM by cropping. The results indicate that the watermarked DEM is well recognized. The watermark can be read 100% for 2D DCT, while that for 2D DFT can be read 90.50%. The distortion value of the elevation data under the DCT technique demonstrates the smallest maximum value of 0.1 m compared with 4.5 and 1.1 m for 2D DFT and 2D DCT–DWT. Meanwhile, the height difference (Max Delta), the peak signal-to-noise ratio, and the root mean squared error (RMSE) are highest in mountainous, lowland, and coastal areas, respectively. Overall, the 2D DCT is also superior to the 2D DFT and the2D DCT–DWT. Although only one can recognize the nine watermarks inserted on each sheet, DEMs attacked by the cropping process can still be identified. However, this finding can sufficiently confirm that DEMs belong to BIG.