Judul: Torrified Biopellet of Coconut Husk
Abstrak: Kepadatan energi sabut kelapa dapat ditingkatkan melalui proses torefaksi. Penelitian ini bertujuan untuk mengetahui mutu biopelet sabut kelapa yang ditorefaksi pada suhu dan waktu torefaksi yang beragam. Mutu biopelet ditentukan berdasarkan kadar air, kadar abu, zat terbang, karbon terikat, kerapatan, ketahanan dan nilai kalor yang mengacu pada standar DIN EN 14961-2 dan SNI 8021-2014. Secara umum biopelet yang dihasilkan telah memenuhi standar SNI 8021-2014. Hasil penelitian menunjukkan bahwa biopelet memiliki kadar air sebesar 5,41-5,54%, zat terbang sebesar 31,88-32,25%, kadar abu sebesar 2,95-3,26%, karbon terikat sebesar 59,26-59,45%, kerapatan sebesar 0,91- 1,02 g/cm3, ketahanan sebesar 93,57-93,81%, dan nilai kalor sebesar 4.454-4.923 kkal/kg. Torefaksi biopelet sabut kelapa pada suhu 300oC selama 15 menit mampu meningkatkan nilai kalor sampai dengan 4.923 kkal/kg, The energy density of coconut husk can be increased through torefaction process. This research was intended to determine the quality of coconut husk biopelet torefied at various temperatures and retention times. Biopelet quality parameter was determined based on moisture content, volatile matter, ash content, fix carbon, density, durability, and heating value refered to the standards of DIN EN 14961-2 and SNI 8021-2014. In general, the biopellet produced have met the SNI 8021-2014 requirements. The results showed that the biopellets had a moisture content of 5,41-5,54%, a volatile matter of 31,88-32,25%, an ash content of 2,95-3,26%, a fix carbon of 59,26-59,45%, a density of 0,91-1,02 g/cm3, a durability of 93,57-93,81%, and a heating value of 4.454-4.923 kcal/kg. Torefaction of the biopelet at 300oC for 15 minutes increased the heating value up to 4.923 kcal/kg.
Keyword: Biopelet, coconut husk, torrefaction, bioenergy

Judul: Biopellet Characterization of Arabica Coffee Grounds and Teak Sawdust as A Result of Torrefaction
Abstrak: Limbah ampas kopi arabika dan serbuk gergaji kayu jati memiliki potensi untuk dijadikan substitusi energi yang bersifat keberlanjutan. Salah satu pemanfaatannya adalah dengan menjadikan biopelet yang ditingkatkan mutunya melalui proses torefaksi. Penelitian ini bertujuan untuk menganalisis karakterisasi biopelet hasil torefaksi pre-treatment (A) dan post-treatment (B). Biopelet dibuat dengan menggunakan pelletizer tipe flat dies dengan formulasi bahan baku 1:1 (perekat 5%), dan pemrosesan torefaksi menggunakan suhu 220 oC (A1 dan B1), 250 oC (A2 dan B2), dan 280 oC (A3 dan B3). Kondisi pre-treatment merupakan torefaksi bahan baku mentah, sementara post-treatment merupakan torefaksi biopelet. Pengujian fisiokimia biopelet mengacu pada SNI 8675-2018 yang mencakup kerapatan, kadar air, kadar zat terbang, kadar abu, kadar karbon terikat, nilai kalor. Pengujian fisik mencakup dimensi, ketahanan, dan hidrofobisitas. Formulasi terbaik pada tiap parameter dicapai oleh perlakuan A3 dengan nilai kerapatan 0,46 g/cm3 , kadar air 3,32%, kadar zat terbang 44,7%, kadar abu 4,75%, kadar karbon terikat 50,55%, dan nilai kalor 25,96 MJ/kg dan perlakuan B3 dengan nilai kerapatan 0,34 g/cm3 , kadar air 3,11%, kadar zat terbang 39,04%, kadar abu 6,97%, kadar karbon terikat 53,98%, dan nilai kalor 25,12 MJ/kg., The potential of Arabica coffee grounds and teak sawdust waste as sustainable energy substitutes by converting them into bio-pellets enhanced through torrefaction. The research focuses on characterizing bio-pellets from pre-treatment (raw material torrefaction) and post-treatment (bio-pellet torrefaction). Using a flat die pelletizer, the bio-pellets were produced with a 1:1 raw material ratio (5% adhesive) and torrefied at 220°C, 250°C, and 280°C. The bio-pellets' physicochemical properties, including density, moisture content, volatile matter content, ash content, fixed carbon content, and calorific value, were evaluated according to SNI 8675:2018 standards. Physical properties such as dimensions, durability, and hydrophobicity were also assessed. The optimal formulations were A3, with a density of 0,46 g/cm³, moisture content of 3,32%, volatile matter content of 44,7%, ash content of 4,75%, fixed carbon content of 50,55%, and a calorific value of 25,96 MJ/kg, and B3, with a density of 0,34 g/cm³, moisture content of 3,11%, volatile matter content of 39,04%, ash content of 6,97%, fixed carbon content of 53,98%, and a calorific value of 25,12 MJ/kg
Keyword: biopelet, Ampas kopi arabika, serbuk gergaji kayu jati, torefaksi pre-treatment dan post-treatment

Judul: Tinjauan Matematis pada Model Makroskopik dan Mikroskopik Arus Lalu-lintas
Abstrak: Traffic flow phenomenon can be described through mathematical model such as continuous dynamic model with an ordinary differential equation so that it can be solved with integral factors. In this paper three simple models of traffic flow are discussed, i.e, two macroscopic and one microscopic models. Macroscopic model formulates dynamics of the traffic flow that occurs on a large number of vehicles on a road. While the microscopic model explains drivers’ behavior in their interaction with other vehicles ahead, i.e, car-following model. This paper shows the existence of ordinary differential equation found in the traffic flow model and indicates some different representations in the context of the same model. It also reviews a simple model of traffic flow along a single link, which leads to some unexpected results, i.e, it can express the solution model in term of link outflows as well as trip time. In the microscopic model, simulation is done to illustrate the behavior of the drivers with a sensitivity coefficient as a benchmark parameter.
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