Biomethanization of orange peel waste.

Recent research has demonstrated that orange peel waste is a potentially valuable resource that can be developed into high value products such as methane. Following a pre-treatment to extract D-limonene, the anaerobic digestion of orange peel waste was evaluated at laboratory and pilot scale under mesophilic and thermophilic conditions. D-limonene removals of 70% were reached with pre-treatment. The results showed the convenience of thermophilic conditions for treating this waste as the methane production rate and biodegradability were higher than at mesophilic temperature. At pilot scale, a thermophilic continuously stirred-tank reactor working in semi-continuous mode was employed. The OLR was found to be in the range of 1.20-3.67 kg COD/m(3) d; the most appropriate range for working under stable conditions at SRT of 25 d. The methane yield coefficient was found to be 0.27-0.29 L(STP)CH(4)/g added COD and the biodegradability 84-90% under these conditions. However, acidification occurred at the highest OLR. 2010 Elsevier Ltd. All rights reserved.