Anaerobic mono-digestion and co-digestion of agricultural wastes and comparison of valorization potentials

Abstract

Anaerobic digestion is an immense technology for not only waste disposal but also biogas production for agricultural-based residues, however the economic value of the biogas is limited. The transition of anaerobic digestion to produce carboxylates can provide a sustainable future and better valorization. In this study, Turkish delight (D), sunflower head (S), and tea waste (T) were mono-digested and co-digested at neutral pH under mesophilic conditions to determine the best set of substrates that can produce maximum methane gas. Methane yield for each digester was recorded as D (388 ml CH4/g TVSused), S (206 ml CH4/g TVSused), T (69 ml CH4/g TVSused), DS (312 ml CH4/g TVSused), DT (213 ml CH4/g TVSused), ST (173 ml CH4/g TVSused), and DST (234 ml CH4/g TVSused) after 30-day in anaerobic digestion. According to the results, the three sets D, DS, and DST were the ones that produced the highest amount of methane gas within their groups. Bacterial community composition for these three sets was determined using MinIONTM. The family Pseudomonadaceae was observed more numerous in D digester that producing the highest methane than the digesters of DS and DST. Moreover, acidification was also conducted to the three sets D, DS, and DST to determine VFA productions under mesophilic condition at pH 5.5 ± 0.2. According to the valorization results, market values of VFAs (sum of acetic and butyric acid) were 6-13 times higher than methane.