Judul: Treatment of Leather Tannery Sludge Waste at the Leather Factory X
Abstrak: Pabrik penyamakan kulit merupakan industri yang menghasilkan berbagai jenis limbah. Sludge sebagai salah satu jenis limbah yang berasal dari Instalasi Pengolahan Air Limbah penyamakan kulit. Proyek desain utama agroindustri ini bertujuan mengidentifikasi sumber dan jumlah limbah yang terbentuk, menganalisis formulasi pengomposan dan mutu kompos, peningkatan skala pengomposan, serta analisis biaya. Pengomposan dilakukan dengan metode in vessel composting menggunakan aerasi alami dengan variasi konsentrasi EM4 0%; 0,1%; dan 0,2%. Hasil analisis mutu terbaik terdapat pada kompos dengan konsentrasi EM4 0,1%. Dimensi reaktor pengomposan skala laboratorium diperbesar untuk skala pilot plant dan skala industri kecil dengan jumlah reaktor yang diperlukan masing-masing sebanyak 3 dan 9 buah dengan dimensi yang sama. Analisis biaya pengomposan menggunakan harga pokok produksi pada skala laboratorium sejumlah Rp2.039,46/kg; skala pilot plant sejumlah Rp249,38/kg; dan skala industri kecil sejumlah Rp567,9/kg. Kompos dengan konsentrasi aktivator EM4 0,1% memenuhi baku mutu SNI untuk parameter kadar air, suhu, pH, dan nisbah C/N sedangkan kadar logam krom masih belum memenuhi baku mutu SNI. Hasil mutu kompos yang dihasilkan direkomendasikan pengaplikasiannya untuk tanaman berbatang tinggi atau tanaman hias. Pengkajian terkait pengomposan lebih lanjut untuk menurunkan kadar krom yang masih relatif tinggi dapat direkomendasikan menggunakan metode pengomposan lainnya salah satunya vermicomposting., Leather tanning factory is an industry that produces various types of waste. Sludge as a type of waste originating from the tannery wastewater treatment plant. The main design project for this agro-industry aims to identify the source and amount of waste generated, analyze compost formulation and compost quality, increase the scale of composting, and analyze costs. Composting was carried out using the in-vessel composting method using natural aeration with a variation of 0%; 0.1%; and 0.2% EM4 concentration. The best quality analysis results were found in compost with 0.1% EM4 concentration. The dimensions of the laboratory scale composting reactor were enlarged for pilot plant scale and small industrial scale with the required number of reactors being 3 and 9 respectively with the same dimensions. Composting cost analysis uses the cost of production on a laboratory scale in the amount of IDR 2,039.46/kg; pilot plant scale of IDR 249.38/kg; and small industrial scale in the amount of IDR 567.9/kg. Compost with an EM4 activator concentration of 0.1% complies with SNI quality standards for parameters of water content, temperature, pH, and C/N ratio, while chromium metal content still does not meet SNI quality standards. The quality of the resulting compost is recommended for its application for tall-stemmed plants or ornamental plants. Studies related to further composting to reduce chromium levels which are still relatively high can be recommended using other composting methods, one of which is vermicomposting.
Keyword: in-vessel composting, compost, chromium, scale up, sludge

Judul: Co-Composting Process Engineering Design of Sludge, Boiler Ash, and Dregs at PT Tanjungenim Lestari Pulp and Paper using Aerated Static Pile Method
Abstrak: PT Tanjungenim Lestari Pulp and Paper menghasilkan limbah padat berupa sludge (30 ton/hari), abu ketel (33,7 ton/hari), dan dregs (3 ton/hari). Limbah yang dihasilkan ini belum diolah dengan baik. Sanitary landfill yang menjadi penanganan limbah saat ini tidak tepat untuk diterapkan ke depannya. Cocomposting dapat menjadi solusi terbaik untuk mereduksi limbah dalam jumlah besar berdasarkan kandungan organik pada bahan dan mengubahnya menjadi produk bernilai tambah. Penelitian ini bertujuan untuk merancang proses co-composting berupa campuran sludge:abu:dregs (2:1:1) dengan metode Aerated Static Pile (ASP). Pengomposan dilakukan pada skala 500 kg dengan menggunakan laju aerasi 0,4 L/menit.kg bahan. Kualitas produk kompos yang dihasilkan lalu dibandingkan dengan baku mutu pada SNI-7847:2012. Dari pengomposan yang telah dilakukan selama 32 hari, diperoleh produk kompos dengan suhu 28?, pH 5,75, kadar air 44,12%, dan rasio C/N sebesar 17,43. Berdasarkan parameter fisik, produk kompos memiliki warna dan bau khas dregs. Berdasarkan parameter kimia, produk kompos kurang memenuhi baku mutu pH dan c-organik. Produk kompos memenuhi baku mutu parameter biologi dan logam berat. Produk kompos yang dihasilkan belum memenuhi baku mutu warna, bau, dan pH, sehingga desain proses pengomposan yang dilakukan belum bisa menjadi acuan untuk peningkatan skala pengomposan., PT Tanjungenim Lestari Pulp and Paper produces solid waste such as sludge (30 tons/day), boiler ash (33.7 tons/day), and dregs (3 tons/day). These wastes are currently not well managed. The sanitary landfill currently used for waste disposal is not suitable for future application. Co-composting could provide the best solution to reduce large quantities of waste based on the organic content of the materials and convert them into value-added products. This research aims to design a cocomposting process using a mixture of sludge:ash:dregs (2:1:1) with the Aerated Static Pile (ASP) method. Composting was conducted on a 500 kg scale with aeration flow rate of 0.4 L/minute.kg of material. The compost product quality was compared to quality standards of SNI-7847:2012. After 32 days of composting, the compost product had a temperature of 28?, pH of 5.75, moisture content of 44.12%, and C/N ratio of 17.43. Based on physical parameters, the compost product had the characteristic color and odor of dregs. Based on chemical parameters, the compost product didn’t meet the quality standards for pH and c-organic. Compost product met quality standards of biology and heavy metal parameters. The compost product did not accord the quality standards for color, odor, and pH, indicating that the composting process design conducted cannot yet serve as a reference for scaling up composting operations.
Keyword: Boiler ash, co-composting, sludge, dregs, process design

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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