Background <p>Aerobic granular sludge (AGS) is a promising biological wastewater treatment technology owing to its compact footprint, low energy demand, and simultaneous removal of organic matter, nitrogen, and phosphorus. However, despite more than 100 full-scale installations worldwide, major challenges remain in granule stability, large-scale implementation, and carbon-neutral operation.</p> Methods <p>This review critically synthesizes evidence from laboratory-, pilot-, and full-scale studies using a Multidimensional Socio-Biological (MSB) framework integrating temporal, spatial, evidence-quality, and governance perspectives. The literature is evaluated across three interconnected themes: granule stability, scalability, and pathways toward carbon-neutral AGS systems.</p> Results <p>Three key findings are identified. First, granule disintegration occurs in approximately 42% of full-scale AGS plants annually, highlighting unresolved mechanisms governing long-term stability. Second, the only available full-scale N₂O emission dataset (0.33%) differs by a factor of 5–15 from laboratory estimates (0.54–4.8%), indicating considerable uncertainty in the carbon balance of AGS. Third, no published full-scale AGS studies are available from Southeast Asia, South Asia, or sub-Saharan Africa, despite these regions representing future growth in wastewater treatment infrastructure.</p> Conclusions <p>Although AGS has substantial potential for sustainable wastewater treatment, its widespread adoption is constrained by critical evidence gaps. Future research should prioritize long-term full-scale monitoring, greenhouse gas assessment, and demonstration projects in tropical and developing regions to enable reliable and carbon-neutral AGS implementation.</p>