Modelling Selective CO 2 Absorption and Validation via Photosynthetic Bacteria and Chemical Adsorbents for Methane Purification in Anaerobic Fermentation Bioreactors.

This study delves into advanced methane purification techniques within anaerobic fermentation bioreactors, focusing on selective CO 2 absorption and comparing photosynthetic bacteria (PNSB) with chemical adsorbents. Our investigation demonstrates that MgO-Mg(OH) 2 composites exhibit remarkable CO 2 selectivity over CH 4 , substantiated through rigorous bulk and surface modelling analyses. To address the challenges posed by MgCO 3 shell formation on MgO particles, hindering CO 2 transport, we advocate for the utilisation of MgO-Mg(OH) 2 composites. In on-site experiments, these composites, particularly saturated MgO-Mg(OH) 2 solutions (S2), achieved an astonishing 100% CO 2 removal rate within a single day while preserving CH 4 content. In contrast, solid MgO powder (S3) retained a mere 5% of CH 4 over a 10 h period. Although PNSB (S1) exhibited slower CO 2 removal, it excelled in nutrient recovery from anaerobic effluent. We introduce a groundbreaking hybrid strategy that leverages S2's swift CO 2 removal and S1 PNSB's nutrient recovery capabilities, potentially resulting in a drastic reduction in bioreactor processing time, from 10 days when employing S1 to just 1 day with the use of S2. This represents a remarkable efficiency improvement of 1000%. This pioneering strategy has the potential to revolutionise methane purification, enhancing both efficiency and sustainability. Importantly, it can be seamlessly integrated into existing bioreactors through an additional CO 2 capture step, offering a promising solution for advancing biogas production and promoting sustainable waste treatment practices.