Judul: Feasibility of Sheep and Biogas Farming (Case Study: Cikarawang Farm)
Abstrak: Jawa Barat merupakan provinsi dengan jumlah peternakan domba terbesar di Indonesia, yaitu 9.987.870 ekor domba pada tahun 2022. Hal tersebut menimbulkan permasalahan lingkungan salah satunya adalah limbah feses atau kotoran domba yang belum dimanfaatkan. Penelitian ini berfokus pada kelayakan usaha peternakan domba dan penerapan biogas di Cikarawang Farm, Bogor. Penelitian ini bertujuan untuk menganalisis kelayakan finansial dan non-finansial dari penggunaan teknologi biogas dalam peternakan domba, serta melakukan analisis switching value. Data dikumpulkan dari 32 responden menggunakan kuesioner dan wawancara. Data dianalisis dengan kriteria investasi seperti NPV, IRR, Net B/C dan PP. Tanpa biogas, NPV sebesar Rp466.418.189, IRR mencapai 22%, Net B/ sebesar 1.04 dan PP selama 4.5 tahun. Sementara itu, dengan penerapan biogas, Rp578.762.730 , IRR naik menjadi 28%, Net B/C juga meningkat menjadi 1.34 dan Payback Period berkurang menjadi 4.1 tahun. Analisis switching value mengindikasikan bahwa penurunan harga domba dapat berdampak negatif pada pendapatan. Kesimpulannya, penggunaan teknologi biogas layak secara finansial dan non-finansial, meskipun terdapat tantangan yang perlu diatasi untuk memaksimalkan keuntungan dan keberlanjutan usaha., West Java is the province with the largest number of sheep farms in Indonesia, totaling 9,987,870 sheep in 2022. This creates environmental issues, particularly with untreated sheep manure. This study focuses on the feasibility of sheep farming and biogas application at Cikarawang Farm, Bogor, aiming to analyze the financial and non-financial aspects of biogas technology, as well as conduct a switching value analysis. Data were collected from 32 respondents through questionnaires and interviews, and analyzed using investment criteria such as NPV, IRR, Net B/C, and Payback Period (PP). Without biogas, NPV was Rp466.418.189, IRR was 22%, Net B/C was 1.04, and PP was 4.5 years. With biogas, NPV rose to Rp578.762.730, IRR increased to 28%, Net B/C rose to 1.34, and Payback Period extended to 4.1 years. The switching value analysis indicates that a decrease in sheep price can negatively impact income. In conclusion, biogas technology is financially and non-financially feasible, though challenges remain to maximize profits and business sustainability.
Keyword: biogas, domba, non finansial, Switching Value, aspek finansial

Judul: Biogas Production from A Combination of Sheep and Dairy Cattle Manure
Abstrak: Tingginya populasi domba dan sapi perah di Jawa barat akan menghasilkan kotoran ternak yang berlimpah. Kotoran ternak dapat mencemari lingkungan jika tidak dikelola dengan benar. Biogas dapat diproduksi dari kotoran domba dan kotoran sapi perah melalui fermentasi anaerob. Penelitian bertujuan menganalisis produksi biogas dari kombinasi kotoran domba dan kotoran sapi perah. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) dengan tiga perlakuan dan tiga kali ulangan tiap perlakuan. Perlakuan pada penelitian ini yaitu D100S0 (100% kotoran domba dan 0% kotoran sapi perah), D50S50 (50% kotoran domba dan 50% kotoran sapi perah), dan D25S75 (25% kotoran domba dan 75% kotoran sapi perah). Nilai TS akhir setelah fermentasi anaerobik semua perlakuan berbeda nyata (P<0,05). Volume biogas dan lama nyala api perlakuan D50S50 berbeda nyata daripada D100S0 dan D25S75. Suhu harian biogas mengalami fluktuasi antara 2629 °C. Nilai pH pada rentang 6,698,13 melebihi kondisi netral. Penggunaan kotoran domba sebagai biogas menghasilkan warna nyala api biru sedikit kemerahan. Hasil penelitian menyimpulkan bahwa kotoran domba berpotensi menghasilkan biogas., The high population of sheep and dairy cattle in West Java will produce high manure production. Animal manure can pollute the environment if not managed properly. Biogas can be produced from sheep manure and dairy cattle manure through anaerobic fermentation. This study aimed to analyze biogas production from a combination of sheep and dairy cattle manure. This study used a completely randomized design (CRD) with three treatments and three replications for each treatment, including D100S0 (100% sheep manure and 0% dairy cattle manure), D25S75 (25% sheep manure and 75% dairy cattle manure), and D50S50 (50% sheep manure and 50% dairy cattle manure). The final TS after anaerobic fermentation differed for all treatment (P<0,05). The biogas volume and flame duration of D50S50 differed (P<0,05) than D100S0 and D25S75. The daily biogas temperature fluctuates between 26-29 °C. The pH value in the range of 6,69-8,13 exceeded neutral conditions. The use of sheep manure as biogas produces a slightly reddish-blue flame. To conclude, sheep manure has the potential to produce biogas.
Keyword: biogas, kotoran domba, kotoran sapi perah

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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