Use of Compact Biogas Plant for Biogas Production Utilizing Waste Food Materials, Fruits, and Vegetable Peelings of High Calorific Contents
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In order to study the efficiency of compact biogas plant, two experiments taking waste food materials and vegetable peelings (cooked stale rice, flour, peelings of pineapple and potato) were conducted. Before initiating the experiment and to quicken the digestion process, dung slurry was inoculated in the plant digesters. In Experiment I, stale cooked rice, potato peelings, pineapple peelings and their mixture (1:1:1) were used. In Experiment II, waste flour obtained from flour mills and potato peelings were used as the feed stocks and the experiment was completed in 28 days. Feed stocks were blended using a blender and mixed with water before using in the experiments. Studies have revealed that production of biogas was higher when stale cooked rice (0.60 m³) was used as the feedstock, followed by potato peelings (0.44 m³), pineapple peelings (0.32 m³) and the mixture of these three feedstocks (0.21 m³). The yield of biogas from waste flour remained low and the values ranged between 0.01 to 0.04 m³. Studies have further revealed that during cooking no soot was observed and the flame appeared to be blue, indicating that the biogas generated contained more Methane. Experiments on the heating potential of the biogas indicated that heating potential of potato peelings was higher, followed by those of pineapple peelings, stale cooked rice and waste flour. Further, heat values of the biogas of different feedstocks was calculated and it was observed that the heat value of stale cooked rice was higher (0.0922 m³/day/Kg) than those of potato peelings, and the mixture of the feed stocks. Heat values of the biogas of flour remained lower. The liquid effluent, the slurry dispersed from the compact biogas was tested in the field for its nutritive value as organic fertilizer. Studies have shown that slurry could be utilized as a fertilizer. Its use as fertilizer resulted in high growth of tomatoes, dalo, cabbage, eggplants, capsicum and also of indoor ornamental plants
Keywords: Biogas, Waste food, Calorific value