Anaerobic digestion is the most attractive technique for biogas production from organic materials. This research studies and models such production from anaerobic digestion of tomato processing wastes in a single-stage laboratory digester and the variation of pH of the process. The single-stage digester was designed and built on a laboratory scale and the tomato processing wastes used as feed materials for digestion were collected from the Zoshk Khorasan Company (Mashhad-Iran). Some properties of digested materials were determined. The results revealed that the tomato processing wastes could be an appealing option for production of biogas by anaerobic digestion process. The digester was controlled under mesophilic conditions (35 °C) with continuous mixing. Also, the percentage of total solids content was adjusted 8%. The amount of production of biogas from the waste was approximately 142.00 L (130.00 L in STP conditions) which is equivalent to 0.14 m3 per kilogram of volatile solids (m3/kg vs). The methane content in the produced biogas was approximately 60.50% (about 86.00 L).

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