Evaluation of the Methanogenic Potential of Tunisian Vegetables and Fruit Wastes: Biogas Production and Characterizations

The present work explores the production of biogas from fruit and vegetable wastes obtained from the wholesale market of Bir El Kasaa (Tunis) under anaerobic conditions. The experiments were carried under mesophilic temperatures (35 ± 2 °C) for 25 days. Total solids, volatile solids, moisture content, and chemical oxygen demand content of the wastes were determined before the experiment to characterize both the substrate and the inoculum. Four laboratory-scale batch digesters were used (T, D1, D2, D3) with the Inoculum to substrate ratio (ISR) in the reactors of (0, 0.25, 0.5, 0.75), respectively. The volatile solids degradation in each of the reactors (T, D1, D2, D3) was 17%, 15%, 28.3%, and 55%, respectively. To evaluate the production of biogas, the cumulative volume of biogas after 25 days and the methane yields were measured. In the four reactors (T, D1, D2, D3), the cumulative volume and the methane yields were (0.9 L/days, 1.5 L/days, 1.2 L/days, 1.1 L/days) and (6%, 15%, 21%, 27%). Thus, it was shown that among all the reactors, optimum results were given in the reactor D3.