Research Of Strengthening Methane Oxidation Cover Material Function By Using Exogenous Bacteria

As the second most significant greenhouse gas,methane(CH₄)has 15-30 times more global warming potential than carbon dioxide.Over nearly a century,the concentration of methane in the atmosphere continues to grow.Methane emission reduction as a measure to restrain the Global warming,the most effective way to reduce methane proportion of anthropogenic emission source.Use of landfill cover material as an object of simulation in laboratory to screen and build efficient methane oxidation material.Further,building methane oxidation biocover material based on exogenous bacteria,and studying the factors affecting of methane oxidation capacity and methane oxidative bacteria growth.Function strengthen mechanism of exogenous bacteria for methane oxidation cover material was explored.The experimental results as the following:(1)Cattle manure compost(CMC)was the most effective methane removal biocover material in all selected material(methane oxidation capacity V_max:3386.50?g·g^-1·h^-1-3451.25?g·g^-1·h^-1).Building three compounded biocover material for methane removal based on CMC,the optimum mix proportion of CMC and other material was 2:8(m/m).The optimum moisture content and temperature were 80%of saturated water content and 35oC.For compounded biocover material(CMC and sand,CMC and clay,CMC and paddy soil),methane oxidation rate reached 280.44,530.88,581.84?g·g^-1·h^-1 respectively after three methane incubation culture.T-RFLP analysis based on 16s r DNA showed that the adding of CMC reduced the bacteria diversity index and evenness index of compounded biocover material.T-RFLP analysis based on pmo A gene found that the Type I methanotroph,including Methylococcus,Methylocaldum,Methylamonas,Methylomicrobium,widely existed in all the selected samples.(2)Using 16 s r DNA identification,methanotroph M16 was identified as Methylocystis and named Methylocystis sp M16.The optimized conditions for the methane removal and growth of Methylocystis sp.M16 as follows:NH₄NO₃ 1.0 g/L,Copperion 1.0?mol/L,p H was 7.0 and temperature was 30?.High concentration of inorganic nitrogen source contains ammonium nitrogen could suppress methane oxidation;The copper ion is the most significant trace elements on M16.In the optimal conditions of these factors,the Absorption values(A₆₀₀)of Methylocystis sp.M16 were above 0.5 and methane removal efficience were above 95%.(3)Methane oxidation cover material based on exogenous bacteria,which is laboratory cultures of methane oxidizing bacteria strains,was builded.These materials included exogenous bacteria&paddy soil,exogenous bacteria&clay,exogenous bacteria&sand.Exogenous bacteria&paddy soil and exogenous bacteria&clay all have high methane removal rate,which reach to 63?74?g·g^-1·h^-1.Compared with the soil without bacteria(5?g·g^-1·h^-1),the rate of increase more than 10 times.After adding exogenous bacteria methane oxidation,enhancing effect of methane oxidation capacity of sand(rate fluctuations within 10?g·g^-1·h^-1)was not significant.Using Biolog ECO micro plate technology analytic function diversity of material bacteria,results shows that adding bacteria improved the activity of microorganism overall material,changed the carbon source utilization types and levels.T-RFLP and Clone Library analysis shows that Type?methanotroph predominated in materail added M16 strain.Type?methanotroph of material mainly similar to Methylocystis species.Relative abundance of Type?methanotroph increase over time,and then tends to be stable.Type?methanotroph of material have high similarity with the Methylomicrobium album.(4)The enhanced effect of nutrients addition(i.e.,carbon source,inorganic nitrogen,copper)on growth of methane removal rate and bacteria number is not obvious.Some nutrients,such as methanol,NH₄⁺-N,high concentration of copper,even have the effect of inhibition on promotion of methane removal rate and bacteria number.Number of bacteria calculated by count method of MS solid plate contained methanol as sole carbon source,has positive correlation with the methane oxidation rate.The pmo A T-RFLP analysis showed that after adding exogenous nutrient element,methanotroph of methane oxidation material is still mainly included Type?methanotroph(Relative abundance,>60%),but the Type?relative abundance is generally reduced,and the abundance of Type?methanotroph increase of 2.7-8.54%.Ammonia oxidizing bacteria mainly increased in the samples added glucose,ammonium chloride,and ammonium nitrate.Add extra nutrients did not promote the increasing of the relative abundance of Type?methanotroph within 9 days.In conclusion,using exogenous methanotroph to strengthen the methane oxidation capacity of methane oxidation biocover material is an effective and feasible way.The reinforcement measures for improving methane oxidation capacity in this study could provide good reference for the emissions reduction of methane.