Biochemical methane potential of fruits and vegetable solid waste feedstocks

The biochemical methane potential of 54 fruits and vegetable wastes samples and eight standard biomass samples were determined in order to compare extents and rates of their conversion to methane. All the samples were obtained fresh, grown in nutrient enriched environment and belonged to mature age group. The ultimate methane yields (B-0) and kinetics of fruit wastes ranged from 0.18 to 0.7321 g(-1) VS added and 0.016 to 0.122 d(-1), respectively, and that of vegetable wastes ranged from 0.19 to 0.41 g(-1) VS added and 0.053 to 0.125 d(-1), respectively. Temperature had no effect on the B-0 of mango peels; however, the conversion kinetics were higher at 35 C than at 28degreesC. All the samples of fruits and vegetable wastes tested gave monophasic curves of methane production. Substantial differences were observed in the methane yields and kinetics among the varieties in mango, banana and orange. Different fruit parts within the same variety showed different yields in orange, pomegranate, grape vine and sapota. The methane yields from the mango peels of some of the varieties, orange wastes, pomegranate rotten seeds and lemon pressings were significantly (P < 0.05) higher than the cellulose. Methane yields and kinetics of vegetable wastes in different varieties as well as within different plant parts of the same variety differed. Onion peels exhibited yields significantly (P < 0.05) similar to cellulose, while majority of the vegetable wastes exhibited yields greater than 0.31 g(-1) VS. These results provide a database on extent and rates of conversion of fruits and vegetable solid wastes that significantly contribute to organic fraction of municipal solid wastes (OF-MSW). (C) 2003 Elsevier Ltd. All rights reserved.