Effect of cow manure-derived biochar addition on bio methane production from anaerobic digestion of fruit and vegetable waste

Abstract

Fruit and Vegetable Waste (FVW) is one of the Municipal Solid Waste (MSW) fractions which adds pressure on the existing solid waste treatment facilities as well as on the waste management process. The main objective of this study was to evaluate the effect of cow manure-derived biochar (CMDBC) as an additive to the quality and quantity of biomethane production during the anaerobic digestion (AD) process of FVW. The CMDBC was prepared at different pyrolysis temperatures ranging from 300-600 0C and added in varying quantities ranging from 0.5 – 3 g. This study was carried out at different Inoculum-to-Substrate ratios (ISRs) of 1, 1.75 and 2.5 to enable optimal AD conditions. In terms of ISR, higher biogas and methane production were recorded from reactors with ISR values ranging from 1 to 1.75, with the highest from the reactor with an ISR value of 1 and CMDBC loading of 1.75 g prepared at 300 0C. In this case, CMDBC addition reduced Volatile Fatty Acids (VFAs) formation during the digestion of FVW which favored both biogas and methane production. During the optimization process for biogas yield and methane gas, the mean experimental values were obtained as 517 ml/g VS and 311 ml CH4/g VS respectively with CMDBC prepared at 416 0 C and an ISR value of 1.016. The increase in both biogas and methane production was a result of improved AD conditions which favored the methanogenic bacteria responsible for methane production. The results from this study showed that the effectiveness of the AD process depends on the ISR, CMDBC quantity and the pyrolysis temperature used for the production of the CMDBC. However, there is a need to determine the most economical and feasible way for Biochar (BC) production at a family-size level to reduce its economic impact on the biogas systems.