Effects Of Straw Components On Methane Production By Co-degradation Of Coal And Straw

The technology of increasing coalbed methane(CBM)production by microorganism could realize the biological transformation of coal,increase the reserves of CBM and extend the service life of CBM well by utilizing the characteristics of anaerobic microorganism degradation of coal to produce methane.Straw as an exogenous carbon to increase coal biomethane was proposed to activate microbial flora and coal molecules,accelerate microbial metabolism,and increase methane production.Although straw has a good effect on increasing methane production,the related research is still in its infancy.The evolution of microbial community structure,intermediate metabolites and the unique degradation pathway of methane generation under the action of straw need to be studied in depth to clarify the mechanism of straw production.Therefore,in order to study the influence mechanism of coal bioconversion and the influence of straw components on co-degradation of coal and straw for methane production.An experimental system of co-degradation by raw components(root,stem and leaf),extraction components(different reagents/extracts at different times and residual solids),pretreatment components(chemical pretreatment and biological pretreatment)and coal was established by anaerobic culture combined with chromatographic analysis technology.The influence mechanism of straw original components,extraction components and pretreatment components on coal biotransformation of methane was analyzed,the key straw components of straw and coal in co-degradation were found,and the mechanism of straw accelerating coal degradation was explored.The main results were as follows:(1)The methane yield of co-degradation of straw and coal was significantly higher than that of degradation of only coal or only straw.The root and stem promote the coal seam biomethane more obviously.As for the particle size,the influence of coal particle size on biomethane production was greater than that of straw.When the coal particle size was < 0.075 mm and the straw size was 10 mm,the highest methane yield was 597.01 μmol,279.46% higher than that of only coal.Therefore,the increase of methane production was more the result of stimulating the biodegradation of coal,and the key straw raw components were cellulose and hemicellulose.(2)Different reagents(methanol,ethanol,petroleum ether)can not effectively promote the production of biomethane,while the residual solid can significantly increase the production of biomethane,and with the increase of extraction time,the production of biomethane increased first and then decreases.The maximum methane yield of total degradation was 298.81 μmol,138.10% higher than that of only coal.Extraction can damage lignin,cellulose and hemicellulose to some extent,make carbohydrate and fatty acid compounds more vulnerable to anaerobic microorganisms,thus improving biodegradability.The liquid extracts contain furans which inhibit biodegradation,which may inhibit the production of biomethane.(3)The co-degradation of liquid products and coal of straw by microorganism pretreatment can significantly improve the anaerobic biodegradation efficiency of coal.The maximum methane yield of co-degradation was 649.52 μmol/g,which was 1579.65% higher than that of only coal.The co-degradation of straw and coal destroys some side chains on the aromatic ring of coal,which leads to the reduction of substituents on the aromatic ring and the increase of hydrogen atoms,which is more conducive to the degradation of microorganisms.The content of organic acid is related to the production of biomethane,which is an important organic substance in the process of co-degradation between coal and straw.Butyric acid and 4-methylvaleric acid were probably necessary organic acids in the process of co-degradation.(4)From the results of increasing methane yield,the effect of straw pretreatment components(intermediate products of straw biodegradation)in cp-degradation was better.(5)From the perspective of application prospect,straw can be liquefied by microbial pretreatment and chemical pretreatment in the actual production process.Liquid products or organic acids from straw pretreatment could be injected into coal seam or goaf to significantly improve the output of CBM.In the process of co-degradation,there was a synergistic effect between coal and straw.The co-degradation of coal and straw can promote the formation of biomethane.This was of great significance to further improve the production of biomethane and fully,reasonably and efficiently utilize straw biological resources to promote the production of CBM.