Elsevier

Biomass and Bioenergy

Volume 26, Issue 4, April 2004, Pages 389-399
Biomass and Bioenergy

Biochemical methane potential of fruits and vegetable solid waste feedstocks

https://doi.org/10.1016/j.biombioe.2003.08.006Get rights and content

Abstract

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 (B0) and kinetics of fruit wastes ranged from 0.18 to 0.732lg−1 VS added and 0.016 to 0.122d−1, respectively, and that of vegetable wastes ranged from 0.19 to 0.4lg−1 VS added and 0.053 to 0.125d−1, respectively. Temperature had no effect on the B0 of mango peels; however, the conversion kinetics were higher at 35°C than at 28°C. 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 0.3lg−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).

Introduction

Fruits and vegetable solid wastes (FVSW) represent a potential energy resource if they can be properly and biologically converted to methane. They are renewable and their net CO2 contribution to the atmosphere is zero. Over 60×106tons of fruits and vegetables are produced annually in India, of which only 1% is processed in the fruit and vegetable processing industries [1]. FVSW are transported to municipal dump sites and Mata—Alvarez et al. [2] have referred these wastes as organic fraction of municipal solid waste from a separated collection (SC-OF MSW). According to Gunaseelan [3], some of the earlier reports on anaerobic digestion (AD) of FVSW were carried out in 1–5l batch digesters and continuously stirred tanks reactors (CSTR). The source of the FVSW were from commercial processing factories [4], [5], [6], [7], [8], [9] which represent only 1% of the annual production in India. Methane yields of some of the FVSW were to be calculated from the data reported. Only limited data is available on the biochemical methane potential (BMP) and conversion kinetics of FVSW. The objective of this investigation was to determine the BMP of several fractions of FVSW and to provide a database to compare the extent and rates of conversion of various FVSW to methane.

Section snippets

Feedstock

Fresh samples of FVSW were obtained from the vegetable market, domestic kitchen of the author and fruit juice shops, Coimbatore, India (Table 1). The samples belonged to ‘mature’ stage of growth and were grown in nutrient–enriched and irrigated environmental conditions. Standard biomass samples of sorghum and napiergrass were obtained from the Millet Breeding Station, Tamilnadu Agricultural University, Coimbatore. Microcrystalline cellulose powder marketed by Burbidges and Co., Bombay-13,

Standard biomass and cellulose

The corrected cumulative methane yield from sorghum (Sweet sorghum) (Fig. 1 and Table 2) showed that B0 from leaf sheath (stem) was higher than lamina. Inflorescence with flowers and grains exhibited the highest yield. B0 from roots were significantly (P<0.05) lower than shoots. Literature data on methane yield from sorghum ranged from 0.28 to 0.42lg−1VS added from samples containing stems and leaves for a 60 day BMP assay at 35°C. Substantial differences in BMP yields were observed from

Conclusions

The FVSW mentioned in this study are commonly used in South Indian homes and they form the bulk of wastes originated from domestic kitchen. They are dumped into municipal dust-pins and significantly contribute to the OF-MSW. The BMP of FVSW reported in this study provide an extensive database on the extent and rates of their conversion to methane. This study has demonstrated that substantial differences were observed in the methane yields and kinetics among the varieties of FVSW. Methane yields

Acknowledgements

The author wishes to thank the University Grants Commission, New Delhi (Sanction No. F.3-16/99 (SR-11)) for providing financial assistance. Dr. B. Sampathkumar, Principal and Secretary, PSG College of Arts and Science is acknowledged for providing the laboratory facilities.

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