Factors affecting gaseous emissions, maturity, and energy efficiency in composting of livestock manure digestate

This study investigated the interplay effects of key operational factors on maturity, gaseous emissions, and energy efficiency during composting of livestock manure digestate. Orthogonal experiments were conducted with three factors: digestion duration (15, 30, 45 days), corn stalk addition (15%, 25%, 35%, wet weight based), and aeration rate (0.12, 0.24, 0.48 L kg(-1) dry matter (DM) min(-1)). Results showed that digestion duration was the main factor influencing the compost germination index (GI), greenhouse gases (GHGs) emission, and net energy. Digestion duration of 30 days was favored for compost GI and GHG reduction, while digestion duration of 45 days exhibited 18% higher daily net energy. Increasing corn stalk addition and aeration rates improved compost GI, but increased energy consumption. Corn stalk addition of 25% and aeration rate of 0.24 L kg-1 DM min-1 could ensure desirable compost maturity and save energy consumption. Thus, digestion for 30 days, 25% corn stalk addition, and aeration rates of 0.24 L kg-1 DM min-1 can be potentially implemented in industry for environmental and cost efficient composting of digestate. (C) 2020 Elsevier B.V. All rights reserved.