Mesophilic anaerobic co-digestion of acorn slag waste with dairy manure in a batch digester: Focusing on mixing ratios and bio-based carbon accelerants

Abstract

Co-digestion of acorn slag waste (ASW) and dairy manure (DM) with two bio-based carbon (BC) accelerants are investigated via batch experiments under mesophilic condition. With the favorable synergistic effect of the mixed substrate and BC accelerant, the anaerobic digestion (AD) systems assembled with aloe peel-derived BC (2.16 g/L) show significantly improved methanogenesis on the basis of the optimum wet weight ratio of ASW to DM (1:3). The cumulative biogas yield is 580.9 mL/g VS, and the total chemical oxygen demand reduction is 79.37%. These results are higher than those of the AD systems without carbon-based accelerants. The feasibility of digestate utilization is evaluated by thermal and fertilizer analyses, which manifest outstanding stability and excellent fertility (6.93%-7.40%) of digestate in co-digestion systems. A general strategy for understanding the enhanced methanogenesis pathways, induced by BC in AD systems, is demonstrated. These important findings open an innovative opportunity for developing carbon-based accelerants in anaerobic co-digestion.

Keywords: Acorn slag waste; Anaerobic co-digestion; Bio-based carbon accelerants; Biogas yield; Dairy manure; Fertilizer utilization.