Evaluation of biogas production potential from co-digestion of cow dung and dried pineapple peels

Abstract

The abundance of agricultural wastes produced from pineapple processing and livestock farms has resulted in the difficulties of disposing off a large amount of waste. Anaerobic digestion is a way to reduce waste and generate renewable energy sources including biogas. In this study, pineapple waste is co-digested with cow dung in batch experiments under mesophilic temperature at 35±5°C at a working volume of 700 ml in 1000 ml serum bottles reactors. The effects of different substrate mix ratios on methane yields are investigated. The batch study is conducted at 8% VS at three different substrate ratios of cow dung to pineapple waste (CD: PW) (1:1, 1:2 and 1:3) and a control (0:1). Daily biogas collection at 1:2 ratio of CD: PW resulted into the highest cumulative biogas production of 1313.5 ml, followed by 1:3 ratio with 912.5ml biogas yield. According to the results, maximum methane yield was achieved at co-digestion ratio of 1:2 CD/PW which was 726.93 CH4/g VS and the lowest methane yield of 324.85 CH4/g VS was obtained from the ratio 0:1 of CW: PW. Overall, the production of methane from pineapple wastes co-digested with cow dung is proven to be a good strategy to minimize solid wastes mainly pineapple waste. The digestate had a final pH ranging from 4.8 to 4.9 in all the reactors and this indicates high levels of acidity. Treatment 0:1 had the highest VS of 90.88% followed by 1:1 with 87.91% VS and treatment 1:2 had the lowest VS with 86.27%. For the biodegradable efficiency, the ratio 1:2 had the highest efficiency of 63.93% followed by 1:1 ratio (CD/PW) with 62.71% and 0:1 had the lowest biodegradability efficiency of 45.48%.