Feasibility assessment of magnetite for enhancing the clean utilization of lignite through anaerobic digestion

This study pioneers the application of magnetite in anaerobic digestion of lignite, achieving dual enhancement of biomethane production and coal-derived waste valorization. At an optimal dosage of 2 g, magnetite increased cumulative methane yield by 55.4 % compared to the control, driven by selective enrichment of electroactive bacteria such as norank_f_Synergistaceae and Proteiniclasticum, alongside DIET-driven methanogens dominated by Methanosaeta at 86.29 % abundance. Concurrently, magnetite induced structural modification of lignite through degradation of recalcitrant aliphatic hydrocarbons and a 53.5 % increase in specific surface area from 7.772 to 11.924 m²/g, collectively improving the combustion efficiency of residual coal. These findings establish magnetite as a bifunctional catalyst that unlocks the bioenergy potential of low-rank coals while converting residual waste into cleaner solid fuels. The strategy offers coal-intensive regions a sustainable pathway to integrate biogas production with circular coal waste management.