Judul: Pra-perlakuan bahan dan pencernaan campuran (Co-digestion) jerami sorgum-lumpur pada produksi biogas
Abstrak: Sorghum stalk and sludge are potential agriculture biomass to be processed into biogas. Pretreatment and co-digestion are used to support increased of gas production. The aimed of this study are to determine effect of pretreatment of sorghum stalk, to determine effect co-digestion of sorghum straw-sludge in biogas production, and to get optimum composition look from volume total of gas production. Substrates composition based on percentage comparison between sorghum stalk and sludge, which is 100:0; 80:20; 60:40; and 40:60 with 2 repetition. Fermentation was conducted in anaerob and batches on 102 days fermentation at Erlenmeyer flask of 500 ml and submerged in water-filled reactor on temperature 36oC with initial TS of 12%. Analysis of research focused on calculate of gas production from each substrate and characterisation sample composition of 60:40 every 2 weeks. Volume totals of gas in L/kg TS biomass are 66.9 composition of 100:0; 122.3 composition of 80:20; 115.4 composition of 60:40; and 13.4 composition of 40:60. Based on result of observation that optimum composition of mixing is 80:20 that have a maximum total gas volume.
Keyword: co-digestion, sludge, pretreatment, sorghum stalk, biogas production

Judul: Penambahan Sludge untuk Mempercepat Proses Konversi Jerami Sorgum menjadi Biogas
Abstrak: Jerami sorgum merupakan limbah pertanian yang belum dimanfaatkan secara optimal. Tujuan penelitian ini adalah mengetahui pengaruh penambahan sludge pada proses konversi jerami sorgum menjadi biogas, mendapatkan perbandingan bobot terbaik antara jerami sorgum dan sludge dalam proses fermentasi anaerobik dan mendapatkan data karakteristik produk akhir berupa digestate dan leachate. Penelitian ini menggunakan jerami sorgum yang telah dikecilkan ukurannya sebesar 1-2 cm. Tahapan penelitian ini terdiri dari karakterisasi jerami sorgum dan sludge, perhitungan dan karakterisasi jumlah bahan yang dimasukkan ke dalam digester dengan perbandingan bobot antara jerami sorgum dan sludge yaitu 100:0, 80:20, 60:40 dan 40:60, fermentasi anaerobik secara batch selama 91 hari di dalam shaker terendam pada suhu terkontrol 36˚C dengan pengukuran gas yang terbentuk dilakukan secara harian, pengamatan khusus untuk perbandingan bobot 60:40, penentuan perbandingan bobot terbaik dan karakterisasi produk akhir berupa digestate dan leachate. Hasil penelitian menjelaskan bahwa produksi biogas kumulatif perbandingan bobot 100:0 sebesar 3,34-5,60 l/kg TS, perbandingan bobot 80:20 sebesar 24,20-67,36 l/kg TS, perbandingan bobot 60:40 sebesar 19,59-83,70 l/kg TS dan perbandingan bobot 40:60 sebesar 78,59-79,69 l/kg TS. Perbandingan bobot terbaik antara jerami sorgum dan sludge adalah 40:60. Digestate perbandingan 40:60 memiliki kadar air 85,22-87,52%, kadar abu (% TS) 36,63-58,76%, total volatile solid (% TS) 41,24-63,37%, pH 7,70-8,13 dan total kjeldahl nitrogen (% TS) 0,34-0,51%. Leachate perbandingan 40:60 memiliki total kjeldahl nitrogen (% TS) 4,65-12,50%, COD 1.416-2.596 mg/l, volatile fatty acid 209,82 mg/l, nitrogen 607,05 mg/l, phosfor 1,18 mg/l dan kalium 55,5 mg/l.
Keyword: jerami sorgum, sludge, biogas, fermentasi anaerobik, digestate, leachate.

Judul: Centrality test for Non-Normal And Skewed Population
Abstrak: The t modified 2 test is more robust than t test for skewed popnlation. This test tolerate the population skewness from -1.2 to 1.2 sample size is reather than 25. The sign test robust to the populated skewed population, but the value of the estimated always close to the size of the tcst. Wilcoxon test is not robust to the population skewness. This test is more suittalble for Symmetric population
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