Chemical factors influencing lignite biogenic gas production in laboratory condition

Lignite samples were investigated for their ability to support microbial methane production with parent bacte- ria in laboratory incubations,with 0. 2 mol / L sodium acetate,0. 2 mol / L formic acid and 5 mg / L yeast extract as exog- enous organic carbon sources respectively. Results show that the organic matter in both soft and hard lignite samples could be used as independent carbon sources to produce biogas. Production rate of soft lignite (0. 18 mL / (g·d)) is higher than that of hard lignite (0. 13 mL / (g·d)). The simulated biogases are composited by CH4 and CO2 . The in- fluence characteristics of exogenous carbon sources on the biogas production rates and gas compositions are different. Sodium acetate (0. 2 mol / L) could lead to an earlier generating time of lignite and a increasing production rate,but could not change the production of lignite biogas. Formic acid (0. 2 mol / L) could not only activate methanogen activi- ties,but also increase the lignite biogas production and CH4 concentration,which effect is more significant for soft lig- nite. Yeast extract (5 mg / L) inhibites the activities of methanogen in the incubation. The high concentration of chloro- form bitumen might be the dominate reason for the high production rate of soft lignite. DOC could not affect the biogas production significantly. The results indicate that the substrate availability within the coal and different types of exoge- nous organic carbon sources are two factors that may influence the lignite biogas production.