R2 inoculated with AD also achieved complete CO conversion at the same LRCO despite a significantly longer adaptation period of approximately 70 days. After the adaption period, PRCH₄ and PRCO₂ of 1.1 and 3.3 Nm³ m⁻³ d⁻¹ on average were observed, respectively. This showed that the AD inoculum required more time for microbial selection and establishment. This delay in CO conversion may be attributed to the slower development of CO-utilizing communities within the digestate. These results align with our previous study using AD as an inoculum, which demonstrated that approximately 80 days were needed to achieve full conversion, with an average CRCO of 3.5 Nm³ m⁻³ d⁻¹ at an LRCO of 3.10 Nm³ m⁻³ d⁻¹ . However, both the AS and AD inocula in this study outperformed the results from the previous study. In the previous study , a LRCO of 5.16 Nm³m⁻³d⁻¹ resulted, on average, a CRCO of 4.5 Nm³m⁻³d⁻¹, CO conversion of 88%, PRCH₄ of 0.99 Nm³m⁻³d⁻¹, and PRCO₂ of 2.55 Nm³m⁻³d⁻¹. These differences highlight the role of the inoculum source in microbial adaptation, as the AD inoculum in this study originated from a different biogas plant than that used previously.