Jurnal Rekayasa Proses, Vol. 10, No. 1, 2016, hal. 10-15 e-ISSN 2549-1490 p-ISSN 1978-287X 10 JURNAL REKAYASA PROSES Volume 10 No.1, 2016, hal. 10-15 Journal homepage: http://journal.ugm.ac.id/jrekpros Evaluasi Pengaruh Konsentrasi Umpan pada Produksi Biogas dari Limbah Cair Industri Alkohol secara Fed Batch Dewi Astuti Herawati 1* , Argoto Mahayana 2 1 Program Studi S1 Teknik Kimia, Fakultas Teknik, Universitas Setia Budi 2 Program Studi D3 Analis Kimia, Universitas Setia Budi *Alamat korespondensi: dewitkusb@gmail.com (Submisi:; Revisi:; Penerimaan:) A B S T R A C T Biogas is an alternative energy source that can be renewed as one of the solutions for the scarcity of fossil energy. Liquid waste from industrial bioalcohol production (technically termed as “vinasse”) is potentially one of very promising raw material of biogas. Vinasse has low pH value (4-5), which is not preferable for metanogen. Therefore this study aimed to define the optimum condition for the production of biogas. The variable to be studied in this research was the influence of vinasse to water ratios on the production of biogas in a fed batch reactor. Three ratios of vinasse and water with the ratios of vinasse to water as 1:2 (R1); 1:2.5 (R2); and 1:3 (R3) were studied. As much as 500 mL of raw material was fed to bioreactor with 6 L of cow manure as starter inoculums. The reactor was fed once every three days, with the feed input as much as 500 mL. At the beginning of the process, total solid suspended (TSS), volatile suspended solid (VSS) and chemical oxygen demand (COD) were analyzed. The volume of biogas was measured every day while the TSS and VSS values were measured once a week. The results showed that the production of biogas at R1 reached 1640.95 ml on day 9 with pH 7, CH 4 concentration of 9.89% and CO 2 level of 36.93%. The biogas production at R2 on day 20 reached 119.67 mL with a methane content of 15.85%, 43.282% of CO 2 level, and pH 5. In R3 the volume biogas generated on day 10 reached 158.24 mL with CH 4 content of 35.36%; 35.27% of CO 2 level and pH 7. Fed batch system was shown to reduce the effects of inhibitor. Keywords: biogas, vinasse, levels of CH 4 , fed batch. A B S T R A K Biogas merupakan sumber energi alternatif yang dapat diperbaharui sehingga dapat mengurangi kelangkaan kebutuhan energi. Limbah cair industri alkohol (vinasse) berpotensi sebagai salah satu bahan baku biogas. Vinasse dengan nilai pH relatif rendah (4-5) bukan bahan baku yang mendukung pertumbuhan bakteri metanogen, sehingga diperlukan penelitian untuk mengatur kondisi yang terbaik pada produksi biogas. Penelitian ini bertujuan untuk mengetahui pengaruh perbandingan vinasse dan air terhadap produksi biogas secara fed batch. Berbagai perbandingan vinasse dan air, yaitu 1:2 (R1); 1:2,5 (R2); dan 1:3 (R3) sebanyak total 500 mL diumpankan ke bioreaktor setiap 3 hari sekali dengan jumlah starter kotoran sapi sebanyak 6 L. Sebagai karakterisasi bahan baku, dilakukan analisis Total Suspended Solid (TSS), Volatile Suspended Solid (VSS) dan Chemical Oxygen Demand (COD) awal. Volume biogas diukur setiap hari. Sepanjang proses berjalan, kandungan TSS, VSS dan COD dianalisis setiap 1 minggu sekali. Analisis TSS dan VSS dengan metode APHA 2005 dan COD dengan metode SNI (2009) serta volume biogas dengan manometer air. Hasil penelitian menunjukkan