Improving biogas production from fruit waste: using chemical, mechanical and thermal pretreatments and co-digestion with cow manure

Authors

1 Department of Biosystems Engineering, Faculty of Agriculture, University of Kurdistan

2 Department of Biosystems Engineering, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran

Abstract

Every year, a significant part of fruit and vegetable products is lost due to the country's inappropriate transportation systems and storage facilities. The waste of strawberry and apple products in Iran is estimated at 40% and 31%, respectively; which can be considered as a source of biomass in bioenergy production. Despite the good biogas production potential, fruit waste requires pretreatment due to lignocellulosic matter to reduce biological decomposition time. This research investigated the effect of mechanical, chemical and thermal pretreatments on the degradability of fruit waste and the amount of biogas production from its co-digestion with cow manure. Mechanical pretreatment was by crushing apple and strawberry waste into pieces of 5, 10 and 15 mm, chemical pretreatment was by placing fruit waste in sodium hydroxide solution (NaOH) at concentrations of 6, 8 and 10% for 3 hours and heat treatment was done by putting waste together with distilled water inside the microwave at 800 watts for 10, 20 and 30 minutes. The pretreated wastes were co-digested with cow manure and were fed into the batch digesters under anaerobic digestion conditions for 25 days. The results showed that the pretreatments of crushing, sodium hydroxide and the microwave increased biogas production compared to the control by 5%, 50.9% and 27.3%, respectively. Chemical pretreatment can be suggested as a preferred method of pretreatment of the identified wastes.

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