FUNGAL PRETREATMENT OF ORANGE PROCESSING WASTE BY SOLID-STATE FERMENTATION FOR IMPROVED PRODUCTION OF METHANE

Pretreatment of orange processing waste (OPW) by solid-state fermentat ion using selected strains of Sporotrichum, Aspergillus, Fusarium and Penicillium improved overall productivity of biogas and methane. Funga l pretreatment enhanced the availability of feed constituents and redu ced the level of antimicrobial substances and allowed the use of a len ding rate of OPW of 8-10% (dry weight) compared with untreated feed of 4%. Anaerobic digestion of pretreated feed for six months in 1500 lit re KVIC (Khadi and Village Industries Commission) digesters yielded an average biogas yield of 0.5-0.6 m(3)/kg volatile solids added at a lo ading rate of 8% with a 25 day hydraulic retention time (HRT). Higher concentrations of pretreated OPW posed serious operational problems du e to plugging of the digester The methane production by this process d emonstrated the stability of the digester throughout the period of stu dy with a volatile fatty acids (VFA) of 600-800 mg/litre (as acetate), pH 6.8-7.0 and total alkalinity of 2200-3000 mg/litre (as CaCO3).