Enhanced anaerobic co-digestion under a magnetic field by a synergistic host–guest strategy: Focusing on accelerant, biogas yield, fertilization and coupled effect.

[Display omitted] • CQDs and PC effectively promote biogas production in AcoD MF system. • Cumulative biogas yield of the CQDs/PC (1.2) group is 648.5 mL/g VS. • The digestate with CQDs/PC (1.2) show total nutrient content (N + P + K) of 49 g/kg. • Methanobacterium and Methanosarcina are enriched by adding CQDs and PC. • Mechanisms of magnetic field coupled CQDs/PC to improve AD performance is analysed. Carbon materials are widely used for direct interspecies electron transfer (DIET) to promote CH 4 yield in anaerobic digestion (AD). However, the addition of host–guest assembly carbon accelerant has not been reported. This work explores the facilitation of carbon quantum dots (CQDs) immobilized in porous carbon (PC) as a host–guest accelerant in anaerobic co-digestion (AcoD) under a magnetic field. The addition of CQDs and PC increased the biogas yield and TCOD removal efficiency by 30.1–38.6 % and 14.2–24.2 %, respectively, compared with control group (467.8 mL/g VS; 37.7 %). Fertilization efficiency of the optimal CQDs/PC group was 4.9 % and the excellent electronic exchange capability of CQDs (1.04 μmol e-/g) and PC (0.64 μmol e-/g) facilitated DIET. This approach helped in enriching anaerobic microorganisms and strengthened the thermal stability of the digestates. These findings provide new insights for improving AD performance using CQDs coupled PC. [ABSTRACT FROM AUTHOR]