Effect of thermal pretreatment of East African highland cooking banana peels on biogas production

Abstract

East African Highland Cooking Banana peels (EAHB peels) possess suitable properties for biogas production through anaerobic digestion however hydrolysis of EAHB Peels like other lignocellulosic materials is slow and therefore limited to compounds that are not encapsulated by lignin. Different methods have been sought to improve the biogas yield from this kind of biomass and these include mechanical, chemical, and biological methods. The present study investigated the effect of thermal pretreatment of EAHB peels on biogas production through conducting anaerobic batch fermentation. The results from this study showed that generally, EAHB peels are viable for biogas production through anaerobic digestion. From proximate analysis the EAHB peels had ash content ranging between 8.54 – 9.34% db; moisture content 84.2 – 84.5% wb; and dry matter content 14.7 – 15.5% wb and volatile solids ranged between 13.5 – 14.2% wb. Hydrothermal pretreatment had the highest C:N ratio, cellulose, and hemicellulose at 15.11, 39.63±1.42% and 44.69±1.10% respectively. Hydrolysis of lignin led to increase in percentage hemicellulose and cellulose as a result of thermal pretreatment. Biogas yield was observed to increase significantly with thermal pretreatment yielding 614±23 lN/kg VS biogas while the untreated had 571±28% lN/kg VS biogas. Methane yield also increased with the hydrothermal pretreatment giving highest methane yield at 296±7 lN/kg VS methane compared to the untreated with 279±13% lN/kg VS methane. In conclusion, thermal pretreatment improved the hydrolysis of lignin which improved degradability and digestibility of the EAHB peels as well as biogas yield.