Enhanced biomethane production from anthracite by application of an electric field

Abstract

The utilization of biogenic coalbed methane (CBM) meets the increasing demand of energy and reduces the impact of greenhouse gases on the environment. Application of an electric field is a promising technology to increase biomethane production from various complex organic compounds. Here, the effects of an applied voltage (0.6 V, 1.2 V, and 1.8 V) on methane production due to coal biodegradation, as well as the structure of microflora and intermediates were studied by anaerobic culture, pyrosequencing, and GC–MS. The maximum methane production was observed at 1.2 V with an average of 63.0 μmol/g of coal, which was 134% higher than the control without electrodes (26.9 μmol/g of coal). The CO2 yield was negatively correlated with the methane yield, suggesting that more carbon in coal has been transferred to methane after application of an electric field. The pyrosequencing results showed that the abundance of bacteria with extracellular electron transfer abilities, such as Soehngenia, Desulfovibrio, and Deferrisoma, increased after applying a 1.2 V electric field. Moreover, the structure of the fungal communities changed significantly, especially the abundance of Mortierella, Thielavia, Humicola, and Plectosphaerella. According to the GC-MS results, most of the products detected at the end of the cultivation period in the control were not detected in the cultures cultivated at 1.2 V. New organic compounds such as alcohols, unsaturated fatty acids, and amines were produced in the cultures cultivated at 1.2 V. These results suggest that application of an electric field changes the structure of the microflora, which promotes extracellular electron transfer and the biodegradation of organic compounds, thus enhancing methane production from coal. Furthermore, the distinct organic products detected after cultivation and the significant changes in microbial communities suggest that the degrading metabolism of organic matter in coal might be altered due to the application of an electric field. Based on the results, a biogenic methane production system implemented by application of an electric field was proposed and described.