Maximizing biogas production from leftover injera: influence of yeast addition to anaerobic digestion system

Abstract

Injera is a staple food in Ethiopian dine. This study aimed to investigate on leftover injera (LI) for producing biogas via anaerobic digestion (AD), while leftover injera is full of easily biodegradable components. Aiming to examine the impact of yeast addition on biogas production efficiency, it was found that the addition of 2 % volatile solids (VS) of stimulated yeast, daily biogas output increased by 520 and 550 ml after 12 and 37 days of anaerobic digestion, respectively, with rather steady biogas production. The rate at which gas production increased was drastically cut in half when yeast was left out of the control group. Biogas production increased by only 60 ml despite the addition of two portions of substrate and yeast. Biogas output in the yeast group after fermentation was also up 33.2 % compared to the control group. The yeast group’s anaerobic digesting system was more stable, as determined by the study of markers including volatile organic acids, alkalinity, and propionic acid. The findings can be used as a benchmark for future trials aiming to industrialise continuous anaerobic digestion, allowing for more flexible response to feed as waste LI as organic load.