Feasibility study of enhanced biogenic coalbed methane production by super-critical CO2 extraction

Super-critical CO2 enhanced coalbed methane (Sc-CO2-ECBM) and microbially enhanced coalbed methane (MECBM) are environment-friendly technologies that can improve CBM recovery and generation. In this study, a new approach of MECBM based on Sc-CO2 extraction is presented. The Sc-CO2 pretreatment experiments of anthracite and bituminous coal were conducted to produce biomethane. The extracted organics and the changes of coal structure caused by Sc-CO2 were also analyzed to discuss the mechanism of methane stimulation. The results indicated that methane yields have been greatly improved after Sc-CO2 extraction by 734.85% and 148.15% for anthracite and bituminous coal, respectively. The extractions observed by GC-MS analysis is also favored to generate methane by microorganisms. The little increment of methane production from coal treated by subcritical CO2 indicated that the special characteristics of Sc-CO2 were critical for the stimulation of methane production. More functional groups and even new functional groups were formed to increase coal bioavailability after ScCO2 extraction. The specific surface area and total pore volume of bituminous coal increase after Sc-CO2 extraction that could provide more action sites for microorganisms and enzymes. These results strongly proved the feasibility of enhancing CBM by microbial degradation based on Sc-CO2 extraction. (c) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study presents a new approach of enhancing coalbed methane production by microbial degradation based on Sc-CO2 extraction. Results showed that Sc-CO2 plays a critical role in improving methane yields, forming more functional groups, and increasing coal bioavailability. This study proves the feasibility of enhancing CBM via microbial degradation with Sc-CO2 extraction.