The results of the study of anaerobic co-digestion of agro-industrial organic waste and animal manure are presented in this work. The experiments are divided in two stages. In the first stage the optimal ratio between vegetable waste and animal manure is studied in batch reactors. Once the results of the optimal mixture are obtained, the research of the anaerobic co-digestion continues in semi-continuous operating reactor. In this reactor, the main operating parameters can be controlled. The daily biogas production and the consumption of the buffering solution are monitored in function of the hydraulic residence time (TRH) and the daily organic load in the feed. It can be observed that the reactor operation is stable at TRH greater than 10 days and organic loads up to 4,0 kgDQO/m3d. A yield of de 100 kgDQO/m3reactor is achieved, while the specific biogas production obtained is of 0,31 m3biogas/kgDQO,feed. When the TRH is reduced below 10 days and the organic load is increased simultaneously, the digester enters an unstable operation regime and it tends to acidify. This indicates that the methanogenesis is the limiting step in the process.
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