Enhancing biomethan generation of lignite with blue-green algae as an additive

•Using blue-green algae as organic additive to promote biomethanation of lignite.•The solid phase, liquid phase and gas phase product parameters in the reactor were evaluated.•The process of methane production can be divided into three stages.•Coal: blue-green algae = 1:2 has the best methane production effect.•The addition of blue-green algae promoted the beneficial coexistence of multiple communities. Coal microbial gasification is a new method for mining coal, but the low conversion efficiency of lignite in the existing methods limits the production of biomethane. The research shows that adding proper amount of organic amendments can improve the biological conversion of lignite to methane. Using lignite (L) as the only carbon source and blue-green algae (BGA) to regulate metabolic environment, anaerobic fermentation was carried out for 30 days, and the gas phase, liquid phase and solid phase products were observed and analyzed. The experimental results show that the addition of blue-green algae can enhance the adaptability of related microorganisms to multi-carbon environment, and the degradation effect of lignite is significantly improved. When the ratio of lignite and blue-green algae is 1:2, the degradation effect of lignite is the best, and the methane yield can reach 17.86 g/mL, which is 535.59 % higher than that of pure coal degradation (2.81 g/mL). Among them, The abundance of microorganisms in the culture group, combined with lignite and blue-green algae, effectively demonstrates the anaerobic fermentation process at various stages. Compared with the blank control group, the abundance and diversity of methanogenic archaea increased significantly. In this paper, the contribution of blue-green algae to the microbial degradation process of lignite was discussed from the aspects of composition of fermentation products, morphological characteristics of degradation substrate and evolution of microcoenosis community, and the effective addition amount of blue-green algae, a complex nutrient source, was determined, providing a new idea for further exploration of efficient and clean energy conversion technology of lignite.