PRODUKSI BIOGAS DARI LIMBAH PEMBUATAN TAHU DAN KOTORAN SAPI

BUDI NINING WIDARTI, ST, Ir. Siti Syamsiah, Ph.D.

2012 | Tesis | S2 Teknik Kimia

Limbah pembuatan tahu (limbah cair tahu dan ampas tahu) dan kotoran sapi merupakan bahan organik, dimana komponen utamanya terdiri dari karbohidrat, protein dan lemak. Bahan organik bisa terurai ke bentuk lain melalui proses anaerobik yang akhirnya berubah menjadi biogas. Potensi produksi biogas dari bahan organik dapat diketahui dari kandungan volatile solid bahan baku. Setiap perubahan konsentrasi substrat volatile solid setiap saat menunjukkan terdegradasinya bahan organik untuk menghasilkan biogas. Penelitian ini bertujuan untuk mengetahui kandungan volatil solid optimal dari campuran limbah pembuatan tahu dan kotoran sapi dan untuk memperoleh parameter kinetika degradasi substrat volatile solid sebagai bahan pembentuk biogas. Parameter yang dipelajari adalah kandungan volatile solid dan pengaruh adanya ampas tahu. Percobaan dilakukan dengan memasukkan campuran limbah cair tahu, ampas tahu dan kotoran sapi dengan komposisi tertentu sehingga menghasilkan rasio C/N = 28,7, inokulum dan air ke dalam digester sehingga volume totalnya 800 ml. pH awal campuran diukur dengan kertas lakmus, campuran diberi N 2 supaya kondisi anaerob tercapai kemudian digester ditutup rapat dan diinkubasi di dalam water bath pada suhu 35 o C selama 56 hari. Volume biogas dan pH diukur setiap hari. Metana, VFA dan VS dianalisis setiap 7 hari. Karbohidrat, protein dan lemak dalam slurry dianalisis tiga kali selama proses produksi biogas. Hasil yield biogas tertinggi pada kandungan volatile solid 12% yaitu sebesar 89,522 ml/g VS dengan konsentrasi metana tertinggi 14,68%, sedangkan biogas yang tidak menggunakan ampas tahu hasil yield biogas sebesar 43,249 ml/g VS dengan konsentrasi metana tertinggi 63,38%. Model kinetika degradasi substrat dalam volatile solid sebagai bahan pembentuk biogas dengan first order model, diperoleh k = 0,013/hari.

Waste from tofu production (wastewater and bean curd refuse) and cow manure are organic compounds, which the main components are carbohydrate, protein, and fat. An organic compound can be decomposed into another form trough an anaerobe process and finally transform into biogas. The potency of biogas production from organic compound can be observed from the volatile solid content of the material. The volatile solid content of the substrate change every period of time shows the degradability the organic compound to form the biogas. This research aim is to obtain volatile solid content optimum from the mixture of waste from tofu production and cow manure and to obtain the kinetics parameter of the substrate degradation volatile solid as the biogas raw material. The parameter studied was volatile solid content and the effect of bean curd refuse existence. The experiment was done by entering the mixture of waterwaste and curd been refuse from tofu production added with the cow manure in certain composition so that the ratio of C vs. N =28.7, inoculums and water in digester so that its total volume is 800 ml. The pH at initial condition of mixture was measured by litmus paper, then it was added with N 2 in order to achieve anaerobic condition, and then digester was closed tightly and incubated in the water bath at the temperature of 35oC within 56 days. The biogas volume and pH was measured every day. The methane content, VFA and VS were measured every 7 days. The carbohydrate, protein concentration and lipid concentration in the slurry was analyzed three times a day during the biogas production process. The average yield of biogas at the volatile solid of 12% is 89,522 ml/g VS with the highest methane content is 14.68%. The average yield of biogas from the substrate without bean curd refuse is 43,249 ml/g VS with the highest concentration of methane was 63.38%. the mathematic model of kinetic of the degradation of substrate at the volatile solid as the material or biogas with the first order model it was gained k=0.013/day.

Kata Kunci : Limbah pembuatan tahu, kotoran sapi, volatile solid, biogas.