ALKALINE PRETREATMENT AND AIR MIXING FOR IMPROVEMENT OF METHANE PRODUCTION FROM ANAEROBIC CO-DIGESTION OF POULTRY LITTER WITH WHEAT STRAW

Abstract

Alkaline pretreatment (AL) and air mixing (air) both have the potential to improve anaerobic co-digestion (Co-AD) of poultry litter with wheat straw for methane production. In this study, the effects of the combination of AL (pH 12 for 12 h) and air mixing (12 mL·d−1) on the Co-AD process were investigated. The substrate hydrolysis was enhanced by AL, with soluble chemical oxygen demand increased by 4.59 times and volatile fatty acids increased by 5.04 times. The cumulative methane yield in the group of Co-AD by AL integrated with air (Co-(AL + air)), being 287 mL·(g VSadded)−1, was improved by 46.7% compared to the control. The cone model was found the best in simulating the methane yield kinetics with R2 ≥ 0.9979 and root mean square prediction error (rMSPE) ≤ 3.50. Co-(AL + air) had a larger hydrolysis constant k (0.14 d−1) and a shorter lag phase λ (0.99 d) than the control (k = 0.12 d−1, λ = 2.06 d). The digestate improved the removal of total solids and total volatile solids by 2.0 and 2.3 times, respectively. AL facilitated substrate degradation, while air can enrich the microbial activity, together enhancing the methane generation. The results show that AL + air can be applied as an effective method to improve methane production from the Co-AD process.