Lab to large-scale applications of microaeration in anaerobic digestion: Biowaste digestibility, microbiome nexus, and reactor stability

Anaerobic digestion (AD) is improved with different approaches, including pretreatments, additives, co-digestion, and bioaugmentation. However, these techniques have limitations such as high cost, harmful substances production, and post-treatment of residues. Microaeration is preferable because it is cost-effective, eco-friendly, and easily operable. Recently, the effect of microaeration on AD has drawn researchers' attention. However, in-depth discussion about microbial communities’ shifts, hydrogen sulfide (H₂S) removal, oxidative stress, antioxidative mechanisms, and biomethane efficiency under microaeration is still needed to be reviewed. Thus, the current review fully covered the recent research on the impact of microaeration on substrate digestibility, microbial diversity, desulfurization, and biomethane production. Growth of Firmicutes and Bacteroidetes is increased with microaeration, which facilitates the breakdown of organic compounds. The relative abundance of Methanosaeta is increased by 3–90.6 % with microaeration. Lab-scale studies exhibited biomethane enhancement by 7.8–77 % under microaeration. Several methanogens (such as Methanosarcina barkeri and Methanobacterium thermoautotrophicum) overexpressed antioxidative genes (2–30-fold) that encode enzymes such as catalase, superoxidase dismutase, and superoxide reductase. Large-scale microaeration in anaerobic wastewater treatment plants (WWTPs) removed ≥ 90 % H₂S. This review further suggests that integrating microaeration technology with bioaugmentation, co-digestion, and biochar could improve the reactor stability for efficient biomethanation and H₂S removal.