Effects of digestion time in anaerobic digestion on subsequent digestate composting

Digestion time (DT) in anaerobic digestion (AD) on performance of subsequent digestate composting regarding compost maturity and greenhouse gas (GHG) emission was investigated. Digestates for composting were obtained after anaerobically digested mixture of dairy manure, corn stalks, and tomato residues (48:32:20, volatile solids based) with DT of 15, 30, and 45 days, respectively. Digestates were composted with corn stalks (85:15, wet weight based). Results showed approximately 30% and 70% of biochemical methane potential (342.0 L/kg VS_feedstock) were obtained when DT of 15 and 30 days. Digestate co-composting with cornstalks could be initiated effectively and reduced GHG emissions by 18.9-29.0% compared to compost with raw materials. DT of 30 and 45 days digestate composting cause benefit on germination index. DT of 45 days had the highest net power production in combine AD and composting system. DT of 30 days digestate composting was optimum choice for compost maturity and GHG emissions.