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Considering micro-aeration strategy for enhancing methane production in anaerobic digestion of agricultural wastes

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2022 ASABE Annual International Meeting  2200429.(doi:10.13031/aim.202200429)
Authors:   Yuanhang Zhan, Yiting Xiao, Leland C. Schrader, Ndeddy Aka Robinson Jr., S. Wu, Jun Zhu
Keywords:   Anaerobic mono-digestion, Anaerobic co-digestion, Micro-aeration, Alkaline pretreatment; Methane yield

Abstract. Anaerobic digestion (AD) of agricultural straw waste has been widely applied to produce methane-containing biogas but with limited efficiency. Micro-aeration at different batch AD stages (initial, middle, or daily) had been applied as a novel technology to improve methane production efficiency. However, these micro-aeration strategies had not been directly compared. Neither had the effect of micro-aeration integrated with alkaline pretreatment on the AD process been investigated. Therefore, two groups of AD batch experiments were conducted in this study. Firstly, anaerobic mono-digestion (Mo-AD) of wheat straw was batch operated in 5 identical reactors with different micro-aeration methods employed, including the blank (B), pretreatment (pMA), secondary (sMA), pretreatment plus secondary (pMA + sMA), and daily (dMA). Secondly, anaerobic co-digestion (Co-AD) of wheat straw and poultry litter was batch operated in 4 identical reactors with alkaline pretreatment or micro-aeration applied, i.e. the blank (Co-B), alkaline pretreatment (Al), micro-aeration (Co-MA), and Al plus Co-MA (Al + Co-MA). In the Mo-AD, the cumulated ethane yield (CMY) was 181.44, 191.01, 187.24, 200.25, and 212.37 mL CH4/g VS added for B, pMA, sMA, pMA + sMA, and dMA, respectively, where the highest CMY was reached in dMA, with an increase of 17.05 % compared with that of B. In the Co-AD, the CMY was 195.84, 259.54, 225.44, and 287.20mL CH4/g VS added for Co-B, Al, Co-MA, and Al + Co-MA, respectively. The highest CMY was reached by Al + Co-MA, which was 46.65%, 10.66%, and 27.40% higher than that of the Co-B, Al, and Co-MA, respectively. Daily micro-aeration integrated with alkaline pretreatment of the substrate was suggested to improve the methane production efficiency of the batch Co-AD.

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