Reactor performance and economic evaluation of singular, binary, and ternary mixing of feedstocks for anaerobic digestion

Abstract

ABSTRACT This study compared the performance of singular, binary, and ternary mixing of feedstocks for anaerobic digestion. Three wastes, including organic fraction of municipal solid waste (OFMSW), dairy manure, and corn stover, were tested under the mesophilic condition. Results showed that the binary and ternary mixing stabilised digesters while solely processing OFMSW resulted in pH drop and over accumulation of volatile fatty acids. The highest methane yield of 302.3 L/kg-VS was achieved with 50% OFMSW, 33% corn stover, and 17% dairy manure, which was about 5 times of that obtained from digesting OFMSW alone. The binary and ternary mixing led to multiple peaks in daily methane production, which evened out methane production throughout the 50-day digestion process. Economic analysis showed that solid digestate price, direct fixed capital cost, and labour cost significantly affected net present value (NPV). Ternary mixtures had the highest NPV and internal rate of return and were financially attractive under analysis conditions.