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Anaerobic digestion of sugar beet pulps was studied in a 70 l digestor with sequential feeding, after enzymatic hydrolysis by Trichoderma harzianum cellulases. During the 130 days feeding, 3.6 m3 of biogas were produced with an average content of 58% CH4 from 270 l of hydrolysed pulps at 20 g VS/l. Average yield and production rate were respectively 0.67 m3/kg VS and 0.4 m3/ kg VS and 0.4 m3/m3 of digestor per day.

Thermophilic degradation of sugar beet pulp was studies in batch cultures at 55°C by different associations of bacteria, including CLOSTRIDIUM THERMOCELLUM, METHANOBACTERIUM sp. and METHANOSARCINA MP. C. THERMOCELLUM produced acetate, succinate, methanol, ethanol, H2 and CO2. The coculture of C. THERMOCELLUM and METHANOBACTERIUM sp. produced trace amounts of ethanol and succinate ; acetate concentration was about three times higher than in the C. THERMOCELLUM monoculture. The association of this coculture with METHANOSARCINA MP produced 5.5 mmol CH4/g dry weight sugar beet pulp. (Résumé d'auteur)