Research advances of coalbed gas bioengineering

Coalbed Gas Bioengineering is a special fermentation project by injecting nutrient solution or domesticated and improved strains into underground coal seams or producing gas through surface fermentation to convert some organic components of coal into methane to achieve microbial enhanced coalbed methane(CBM) production.As a newly emerging marginal discipline with multiple disciplines,the project involves three major fields of energy,environment and new materials.It has multiple benefits and attracts more and more attention.This paper summarizes the development history of CBM bioengineering at home and abroad for more than 10 years in detail.Firstly,the microbiological Basis of CBM Bioengineering is systematically discussed from the aspects of coalbed (water) biodiversity,anaerobic fermentation system gas production mechanism and control factors.Then,taking the research of gas-solid-liquid bacteria in anaerobic fermentation system as the core and integrating the research methods of other disciplines,the research method of CBM bioengineering itself has been initially formed.Finally,the implementation plan and development trend of CBM Bioengineering are proposed.Biodiversity provides a source of bacteria for the formation of bio-methane in coal seams.The fermentation process is divided into four stages according to the changes of gas-solid-liquid bacteria in the fermentation system.The substrate and environmental factors in the system control the microbial community structure and affect the production of bio-methane.The causes of methane are divided into three types: acetic acid nutrient type,hydrogen nutrient type,and methyl nutrient type.This understanding has initially formed the theoretical basis of coalbed gas bioengineering.The combination of molecular biology,geochemistry and coal chemistry provides method support for the development of this discipline.In addition，to obtaining bio-methane as a clean energy source,the ground fermentation tank gas production project can also be combined with lignite upgrading,high sulfur coal microbial desulfurization and new material synthesis to maximize economic benefits; Underground coalbed gas bioengineering can greatly increase the output of coalbed methane wells with its gas-enhancing,decomposing,and permeability-increasing effects,and obtain liquid-phase organic matter.At the same time,it can realize the methanation of carbon dioxide,and the emission reduction effect is obvious.CBM Bioengineering is becoming a brand-new field with its theoretical,methodological and practical natures,and will effectively promote the large-scale commercial development process of CBM in China.