Holistic transition in the anaerobic digestion: influences of multiple process controls on the methane enrichment

Anaerobic digestion (AD) of organic wastes primarily generates biogas, an accessible bioenergy resource. The process is straightforward; however, complexity increases at elevated organic loading rates. For instance, the methane yield decreases by 3.5-fold when the organic loading exceeds 8%. The instability of the microbial population structure contributes to challenges in the process. The development of robust microbial consortia offers flexibility in the removal of toxic gases, achieving a 97% removal rate of hydrogen sulfide while also enriching methane gas. The modern real-time monitoring of biogas using microbial fuel cells enhances the accuracy in the determination of volatile fatty acid concentrations (> 7.87 mM), biogas productivity (0.35-0.4 L/h), and methane yield (558 mL methane/g volatile solids). This review paper aims to cover the fundamental aspects of process controls in the biogas generation system. In addition, the paper distinguishes the key measurements needed for AD stability from the various process adjustments for AD upgradation. For instance, measurement of volatile fatty acids by a dissolved hydrogen sensor prevents AD failure. In contrast, employing a helical impeller enhances the productivity of methane. Furthermore, case studies on the application of zerovalent iron nanoparticles, biochar, and bioaugmentation for biogas production have been discussed in detail. Interestingly, the combination of AD upgradation with real-time monitoring elevates the biogas yield (80% increase) and methane content (2.3-fold increase) and improves the process sustainability.