• Microbiology and Biotechnology Letters
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• v.40 no.2
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• pp.152-156
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• 2012

Methanotrophic communities from freshwater wetland (FW), seawater wetland (SW), forest (FS), and landfill soils (LS) around Seoul of South Korea, were characterized using comparative sequence analyses of clone libraries. Proportions of Methylocaldum, Methlyococcus and Methylosinus were found to be greater in FW and SW, while Methylobacter and Methylomonas were more notable in FS and Methylocystis and Methylomicrobium more prominent in LS. Lag periods behind the initiation of methane oxidation significantly varied amongst the soils. Methane oxidation rates were greater in $FW{\geq}LS{\geq}SW>FS$ (p<0.05). Thus, the environmental setting is a significant factor influencing the communities and capabilities of methanotrophs.

• Journal of Korea Soil Environment Society
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• v.3 no.3
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• pp.75-86
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• 1998

This paper is going to show the way we can sample the landfill gases flowing out to the air through final cover soil by using an closed chamber in the field for a short time. In addition, we came to the following results through the application of model with actual measurements. 1) Analyzing changes of concentration in the chamber(H: 10-30cm) every 5 minutes, considering analysis time of gas chromatograph for an half hour. 2) The proportion of $CE_4$to $CO_2$changes rapidly near the surface of final cover soil by the influence of methane oxidation reaction. 3) When flux of landfill gas is F=$10^{-5}$mol/$\textrm{m}^2$.s), methane oxidation reaction has an influence on composition of gases, however there is little influence when F=$10^{-6}$ mol/($\textrm{m}^2$.s).

• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.269-275
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• 2021

In this study, ordered mesoporous silica-supported Ni catalysts were prepared for catalytic partial oxidation of methane (CPOM) by using electroless nickel plating method. Unlike conventionally impregnated catalysts, the electrolessly-plated nickel catalyst showed that nickel was highly dispersed and formed stably on silica-supported surface. It was verified by TEM-EDS analysis. During the activity tests, the electrolessly-plated nickel was barely sintered and the amount of carbon deposition was very small. Consequently, the catalyst was far less deactivated, while the sintering was significantly observed in the cases of the catalysts prepared by the conventional impregnation method. Regarding the palladium-promoted catalysts, the reducibility of nickel was increased, and the reaction performances were enhanced in terms of CH4 conversion and H2/CO ratio of produced syngas.

• Journal of Microbiology and Biotechnology
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• v.33 no.7
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• pp.886-894
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• 2023

During the rhizoremediation of diesel-contaminated soil, methane (CH₄), a representative greenhouse gas, is emitted as a result of anaerobic metabolism of diesel. The application of methantrophs is one of solutions for the mitigation CH₄ emissions during the rhizoremediation of diesel-contaminated soil. In this study, CH₄-oxidizing rhizobacteria, Methylocystis sp. JHTF4 and Methyloversatilis sp. JHM8, were isolated from rhizosphere soils of tall fescue and maize, respectively. The maximum CH₄ oxidation rates for the strains JHTF4 and JHM8 were 65.8 and 33.8 mmol·g-DCW^-1·h^-1, respectively. The isolates JHTF4 and JHM8 couldn't degrade diesel. The inoculation of the isolate JHTF4 or JHM8 significantly enhanced diesel removal during rhizoremediation of diesel-contaminated soil planted with maize for 63 days. Diesel removal in the tall fescue-planting soil was enhanced by inoculating the isolates until 50 days, while there was no significant difference in removal efficiency regardless of inoculation at day 63. In both the maize and tall fescue planting soils, the CH₄ oxidation potentials of the inoculated soils were significantly higher than the potentials of the non-inoculated soils. In addition, the gene copy numbers of pmoA, responsible for CH₄ oxidation, in the inoculated soils were significantly higher than those in the non-inoculated soils. The gene copy numbers ratio of pmoA to 16S rDNA (the ratio of methanotrophs to total bacteria) in soil increased during rhizoremediation. These results indicate that the inoculation of Methylocystis sp. JHTF4 and Methyloversatilis sp. JHM8, is a promising strategy to minimize CH₄ emissions during the rhizoremediation of diesel-contaminated soil using maize or tall fescue.

• Microbiology and Biotechnology Letters
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• v.41 no.2
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• pp.221-227
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• 2013

The methane oxidation characteristics at the top and bottom layers in up-flow biofilters were investigated. Two biofilters were packed with perlite and tobermolite (biofilter A: respectively top and bottom; biofilter B: respectively bottom and top) and then compared. The methane oxidation rate was analyzed with the packed bed of the biofilter layers. The bacterial population in the biofilter was characterized using quantitative real-time PCR. For the methane oxidation rate of the biofilter A column, the perlite top part ($845.16{\pm}64.78{\mu}mol{\cdot}VS^{-1}{\cdot}h^{-1}$) gave a relatively higher value than the tobermolite bottom part ($381.85{\pm}42.00{\mu}mol{\cdot}VS^{-1}{\cdot}h^{-1}$). For the methane oxidation rate of the biofilter B column, the tobermolite top part ($601.25{\pm}37.78{\mu}mol{\cdot}VS^{-1}{\cdot}h^{-1}$) provided a relatively higher value than the perlite bottom part ($411.07{\pm}53.02{\mu}mol{\cdot}VS^{-1}{\cdot}h^{-1}$). The pmoA gene copy numbers, responsible for methanotrophs, in the top layer of biofilter A (1.27E+13 pmoA gene copy number/mg-VSS) was higher than in the bottom layer (3.33E+13 pmoA gene copy number/mg-VSS). However, the population of methanotrophs in biofilter B was not significantly different between the top and bottom layers. These results suggest that although the methane oxidation rates of perlite and tobermolite in the top parts of biofilter A and B were high, methanotroph populations were higher in the bottom parts of both biofilters, with a rapid decline in methane concentrations within the biofilters.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.45-48
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• 2007

Thermochemical 2-step methane reforming, involving the reduction of metal oxide with methane to produce syn-gas and the oxidation of the reduced metal oxide with water to produce pure hydrogen, was investigated on ferrite-based metal oxide mediums and $WO_{3}/ZrO_{2}$. Thermochemical 2-step methane reforming were accomplished at 900 $^{\circ}C$(syn-gas production step) and 800 $^{\circ}C$(water-splitting step). In syn-gas production step, it appeared carbon deposition on metal oxides with increasing react ion time. Various mediums showed the different starting point of carbon deposition each other. To minimize the carbon deposition, the reaction time was controlled before the starting point of carbon deposition. As a result, $CO_{x}$ were not evolved in water-splitting step, Among the various metal oxides, $Mn-ferrite/ZrO_{2}$ showed high reactivity, proper $H_{2}/CO$ ratio, high selectivity of undesired $CO_{2}$ and high evolution of $H_{2}$.

• Korean Journal of Ecology and Environment
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• v.34 no.4 s.96
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• pp.261-266
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• 2001

Effects of elevated carbon dioxide ($CO_2$) on soil microbial processes were studied in a northern peatland. Intact peat cores with surface vegetation were collected from a northern Welsh fen, and incubated either under elevated carbon dioxide (700 ppm) or ambient carbon dioxide (350 ppm) conditions for 4 months. Higher algal biomass was found under the elevated $CO_2$ condition, suggesting $CO_2$ fertilization effect on primary production, At the end of the incubation, trace gas production and consumption were analyzed using chemical inhibitors. For methane ($CH_4$ ), methyl fluoride ($CH_3F$) was applied to determine methane oxidation rates, while acetylene ($C_2H_2$) blocking method were applied to determine nitrification and denitrification rates. First, we have adopted those methods to optimize the reaction conditions for the wetland samples. Secondly, the methods were applied to the samples incubated under two levels of $CO_2$. The results exhibited that elevated carbon dioxide increased both methane production (210 vs. $100\;ng\;CH_4 g^{-1}\;hr^{-1}$) and oxidation (128 vs. $15\;ng\;CH_4 g^{-1}\;hr^{-1}$), resulting in no net increase in methane flux. For nitrous oxide ($N_2O$) , elevated carbon dioxide enhanced nitrous oxide emission probably from activation of nitrification process rather than denitrification rates. All of these changes seemed to be substantially influenced by higher oxygen diffusion from enhanced algal productivity under elevated $CO_2$.

• Journal of the Korean Applied Science and Technology
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• v.40 no.3
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• pp.425-434
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• 2023

An analysis was conducted on landfill gas generation and surface emission by major routes for three landfill sites of S Landfill in the metropolitan area. LS1, which had a total landfill gas generation ratio of 10.9%, accounted for 49.4% of the total surface emissions. The total surface emission of methane alone was 13.6 Nm³/min in the three landfill sites. Among them, the surface emission of methane at LS1, LS2, and LS3 was 8.4(61.7%), 4.0(29.4%), and 1.2 Nm³/min(8.9%), respectively. By emission path in the upper, slope, and dike, it was 7.3(53.2%), 6.4(46.7%), and 0.02 Nm³/min(0.1%). The dike section of the major surface emission areas showed the largest oxidation rate at 87.5%, followed by the upper at 72.3%, and the slope at 71.8%. Based on methane generation, LS1 had the largest surface emission contribution rate, with 61.7% of the total by S Landfill. By major emission path, the slope section of LS1 accounted for 41.7% of the total, the upper section of LS2 24.4%, and the upper section of LS1 20.0%, which accounted for 86.1% of the total methane surface emission of S Landfill. Therefore, it is concluded that intensive management will be necessary.

• Applied Chemistry for Engineering
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• v.5 no.1
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• pp.139-148
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• 1994

The partial oxidation of methane with nitrous oxide on silica-supported metal-oxygen cluster compounds, known as heteropoly acids, has been studied. The effects of several variables such as reaction temperature, partial pressure of reactants, residence time, loading of the catalysts, and pretreatment temperature, on the conversion and product distribution were observed. The kinetics also has been studied. The conversion and yield of formaledehyde show maximum values at a loading of 20 wt%. The apparent reaction order of methane conversion is ca. 1.0 with respect to $CH_4$ and ca. 0.4 with respect to $N_2O$. In addition, the apparent activation energy is 30.78 kcal/mole. The addition of small quantities methane whereas water introduced to the reactant decreased the activity of catalyst under present study.

• Journal of the Korean Chemical Society
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• v.43 no.2
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• pp.156-160
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• 1999

The ignition of methane-oxygen mixtures highly diluted with argon was examined in the temperature range of 1516-1937 K behind a reflected shock wave. The ignition delay times were measured by monitoring pressure profiles and the total emissions at 5.0 cm from the end wall. It was found that the experimental result was correlated by the temperature and the concentrations of the gases. To complement the experiment, computer modeling study of methane oxidation was carried out using a GRI 1.2 mechanism.