Modelling Selective CO₂ Absorption and Validation via Photosynthetic Bacteria and Chemical Adsorbents for Methane...

This study delves into advanced methane purification techniques within anaerobic fermentation bioreactors, focusing on selective CO₂ absorption and comparing photosynthetic bacteria (PNSB) with chemical adsorbents. Our investigation demonstrates that MgO-Mg(OH)₂ composites exhibit remarkable CO₂ selectivity over CH₄, substantiated through rigorous bulk and surface modelling analyses. To address the challenges posed by MgCO₃ shell formation on MgO particles, hindering CO₂ 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% CO₂ removal rate within a single day while preserving CH₄ content. In contrast, solid MgO powder (S3) retained a mere 5% of CH₄ over a 10 h period. Although PNSB (S1) exhibited slower CO₂ removal, it excelled in nutrient recovery from anaerobic effluent. We introduce a groundbreaking hybrid strategy that leverages S2's swift CO₂ 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 CO₂ capture step, offering a promising solution for advancing biogas production and promoting sustainable waste treatment practices.