• Title, Summary, Keyword: Methane

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Low Temperature Methane Steam Reforming for Hydrogen Production for Fuel Cells

  • Roh, Hyun-Seog;Jun, Ki-Won
    • Bulletin of the Korean Chemical Society
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    • v.30 no.1
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    • pp.153-156
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    • 2009
  • Low temperature methane steam reforming to produce $H_2$ for fuel cells has been calculated thermodynamically considering both heat loss of the reformer and unreacted $H_2$ in fuel cell stack. According to the thermodynamic equilibrium analysis, it is possible to operate methane steam reforming at low temperatures. A scheme for the low temperature methane steam reforming to produce $H_2$ for fuel cells by burning both unconverted $CH_4$ and $H_2$ to supply the heat for steam methane reforming has been proposed. The calculated value of the heat balance temperature is strongly dependent upon the amount of unreacted $H_2$ and heat loss of the reformer. If unreacted $H_2$ increases, less methane is required because unreacted $H_2$ can be burned to supply the heat. As a consequence, it is suitable to increase the reaction temperature for getting higher $CH_4$ conversion and more $H_2$ for fuel cell stack. If heat loss increases from the reformer, it is necessary to supply more heat for the endothermic methane steam reforming reaction from burning unconverted $CH_4$, resulting in decreasing the reforming temperature. Experimentally, it has been confirmed that low temperature methane steam reforming is possible with stable activity.

Methane Production Potential of Feed Ingredients as Measured by In Vitro Gas Test

  • Lee, H.J.;Lee, S.C.;Kim, J.D.;Oh, Y.G.;Kim, B.K.;Kim, C.W.;Kim, K.J.
    • Asian-Australasian Journal of Animal Sciences
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    • v.16 no.8
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    • pp.1143-1150
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    • 2003
  • This study was conducted to investigate in vitro methane production of feed ingredients and relationship between the content of crude nutrients and methane production. Feed ingredients (total 26) were grouped as grains (5 ingredients), brans and hulls (8), oil seed meals (9) roughages (3), and animal by-product (1) from their nutrient composition and their methane production protential were measured by in vitro gas test. Among the groups, the in vitro methane productions for both 6 and 24 h incubation were highest in grains, followed by brans and hulls, oil meals and roughages, animal byproducts. Within the group of grains, methane production from wheat flour was the highest, followed by wheat, corn, tapioca, and then oat. Within the brans and hulls, soybean hull showed the highest methane production and cotton seed hull, the lowest. Methane production from oil meals was lower compared with grains and brans and hulls, and in decreasing order production from canola meal was followed by soybean meal, coconut meal, and corn germ meal (p<0.01). Three ingredients were selected and the interactions among feed ingredients were evaluated for methane production. Correlation coefficient between measured and estimated values of the combinations were 0.91. Methane production from each feed ingredient was decreased with increasing amount of crude fiber (CF), protein (CP) and ether extract (EE), whereas positive relationship was noted with the concentrations of N-free extract (NFE). The multiple regression equation (n=134) for methane production and nutrient concentrations was as follows. Methane production (ml/0.2 g DM)=(0.032${\times}$CP)-(0.057${\times}$EE)-(0.012${\times}$CF)+(0.124${\times}$NFE) (p<0.01; $R^2$=0.929). Positive relationship was noted for CP and NFE and negative relationship for CF and EE. It seems possible to predict methane production potential from nutritional composition of the ingredients for their effective application on formulating less methane emitting rations.

Characteristics of Microbial Community Structures of the Methane Hydrate Sediments in the Ulleung Basin, East Sea of Korea (동해 울릉분지 메탄 하이드레이트 퇴적토의 미생물 군집 특성)

  • Shin, Ji-Hye;Nam, Ji-Hyun;Lee, Jin-Woo;Lee, Dong-Hun
    • Korean Journal of Microbiology
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    • v.50 no.3
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    • pp.191-200
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    • 2014
  • Gas hydrates play a significant role in the global carbon cycle and climate change because methane, a greenhouse gas, can be released from the dissociation of gas hydrate. Anaerobic oxidation of methane (AOM) is an important process that consumes more than 90% of the methane released into the hydrosphere and atmosphere. In this study, the microbial community associated with the methane gas hydrate sediment in the Ulleung basin, East Sea of Korea (UBGH) was analyzed by phylogenetic analysis of the mcrA and 16S rRNA gene libraries. A vertical stratification of the dominating anaerobic methane oxidizer (ANME)-1 group was observed at the surface and the sulfate methane transition zone (SMTZ). The ANME-2c group was found to be dominant in the high methane layer. The archaea of marine benthic group B, which is commonly observed in the AOM region, accounted for more than 50% of the identifications in all sediments. Nitrate reducing bacteria were predominant at SMTZ (Halomonas: 56.5%) and high methane layer (Achromobacter: 52.6%), while sulfate reducing bacteria were not found in UBGH sediments. These results suggest that the AOM process may be carried out by a syntrophic consortium of ANME and nitrate reducing bacteria in the gas hydrates of the Ulleung Basin of the East Sea.

Evaluation of field application of biocover and biofilter to reduce landfill methane and odor emissions (매립지 메탄 및 악취 배출 저감을 위한 바이오커버 및 바이오필터의 현장적용 평가 연구)

  • Chae, Jeong-Seok;Jeon, Jun-Min;Oh, Kyeong-Cheol;Ryu, Hee-Wook;Cho, Kyung-Suk;Kim, Shin-Do
    • Journal of odor and indoor environment
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    • v.16 no.2
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    • pp.139-149
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    • 2017
  • In order to reduce odor and methane emission from the landfill, open biocovers and a closed biofilter were applied to the landfill site. Three biocovers and the biofilter are suitable for relatively small-sized landfills with facilities that cannot resource methane into recovery due to small volumes of methane emission. Biocover-1 consists only of the soil of the landfill site while biocover-2 is mixed with the earthworm casts and artificial soil (perlite). The biofilter formed a bio-layer by adding mixed food waste compost as packing material of biocover-2. The removal efficiency decreased over time on biocover-1. However, biocover-2 and the biofilter showed stable odor removal efficiency. The rates of methane removal efficiency were in order of biofilter (94.9%)>, biocover-1(42.3%)>, and biocover-2 (37.0%). The methane removal efficiency over time in biocover-1 was gradually decreased. However, drastic efficiency decline was observed in biocover-2 due to the hardening process. As a result of overturning the surface soil where the hardening process was observed, methane removal efficiency increased again. The biofilter showed stable methane removal efficiency without degradation. The estimate methane oxidation rate in biocover-1 was an average of 10.4%. Biocover-2 showed an efficiency of 46.3% after 25 days of forming biocover. However, due to hardening process efficiency dropped to 4.6%. After overturn of the surface soil, the rate subsequently increased to 17.9%, with an evaluated average of 12.5%.

Water Quality and Methane Emission Characteristics of Aerobic Wetlands Constructed in Coal Mine Area (폐탄광 인공습지의 수질과 메탄 발생 특성 연구)

  • Kwon, Ju-Hyeok;Han, Young-Soo;Cho, Yong-Chan;Ahn, Joo-Sung;Yim, Gil-Jae
    • Journal of the Korean Society of Mineral and Energy Resources Engineers
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    • v.55 no.5
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    • pp.371-382
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    • 2018
  • Global warming is accelerating due to methane release to the atmosphere. The contribution of mine areas among the anthropogenic sources of methane can not be ignored. However, the study on mine area as a methane source is insufficient. The purposes of this study are to monitor methane fluxes in constructed wetlands of mine areas and to investigate the effect of water quality on methane production. Water temperature was the most influential factor affecting methane emissions. The methane fluxes measured by a closed chamber method at aerobic wetlands were estimated to be $-3.6{\sim}12.0CH_4\;mg/m^2/hr$ in seven mines in Korea. This range is similar to the methane flux estimated from European free water surface wetlands. As a future work, it is necessary to study the characteristics of the wetland substrates (or sediments), microbes using the substrates and their environmental control factors in order to qualitatively estimate the methane production in mine areas.

Effects of Rumen Protozoa of Brahman Heifers and Nitrate on Fermentation and In vitro Methane Production

  • Nguyen, S.H.;Li, L.;Hegarty, R.S.
    • Asian-Australasian Journal of Animal Sciences
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    • v.29 no.6
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    • pp.807-813
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    • 2016
  • Two experiments were conducted assessing the effects of presence or absence of rumen protozoa and dietary nitrate addition on rumen fermentation characteristics and in vitro methane production in Brahman heifers. The first experiment assessed changes in rumen fermentation pattern and in vitro methane production post-refaunation and the second experiment investigated whether addition of nitrate to the incubation would give rise to methane mitigation additional to that contributed by defaunation. Ten Brahman heifers were progressively adapted to a diet containing 4.5% coconut oil distillate for 18 d and then all heifers were defaunated using sodium 1-(2-sulfonatooxyethoxy) dodecane (Empicol). After 15 d, the heifers were given a second dose of Empicol. Fifteen days after the second dosing, all heifers were allocated to defaunated or refaunated groups by stratified randomisation, and the experiment commenced (d 0). On d 0, an oral dose of rumen fluid collected from unrelated faunated cattle was used to inoculate 5 heifers and form a refaunated group so that the effects of re-establishment of protozoa on fermentation characteristics could be investigated. Samples of rumen fluid collected from each animal using oesophageal intubation before feeding on d 0, 7, 14, and 21 were incubated for in vitro methane production. On d 35, 2% nitrate (as $NaNO_3$) was included in in vitro incubations to test for additivity of nitrate and absence of protozoa effects on fermentation and methane production. It was concluded that increasing protozoal numbers were associated with increased methane production in refaunated heifers 7, 14, and 21 d after refaunation. Methane production rate was significantly higher from refaunated heifers than from defaunated heifers 35 d after refaunation. Concentration and proportions of major volatile fatty acids, however, were not affected by protozoal treatments. There is scope for further reducing methane output through combining defaunation and dietary nitrate as the addition of nitrate in the defaunated heifers resulted in 86% reduction in methane production in vitro.

Comparison of Greenhouse Gas Emission from Landfills by Different Scenarios (매립지의 온실가스 배출량 산정 시나리오에 따른 온실가스 배출량 비교)

  • Kim, Hyun-Sun;Choi, Eun-Hwa;Lee, Nam-Hoon;Lee, Seung-Hoon;Cheong, Jang-Pyo;Lee, Chae-Young;Yi, Seung-Muk
    • Journal of Korean Society for Atmospheric Environment
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    • v.23 no.3
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    • pp.344-352
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    • 2007
  • Quantifying the methane emission from landfills is important to evaluate measures for reduction of greenhouse gas emissions. To estimate methane emission for the entire landfills from 1990 through 2004 in Korea, Tier 1 and 2 methodologies were used. In addition, five different scenarios were adopted to identify the effect of important variables on methane emission. The trends of methane emission using Tier 1 were similar to the disposed waste amount. Methane emission using Tier 2 increased as the degradation of waste was gradually proceeded. This result indicates that disposed waste amount and methane generation rate are the important variables for the estimation of methane emission by Tier 1 and 2, respectively. As for the different scenarios, methane emission was highest with scenario I that the entire landfills in Korea were regarded as one landfill. Methane emissions by scenario III and IV considering different $DOC_F$ values with the waste type and different MCF values with the height of waste layer, respectively, were underestimated compared to scenario II. This result indicates that the method of scenario I employed to most previous studies may lead to the overestimation of methane emission. Therefore, more careful consideration of the variables should be needed to develop the methodologies of greenhouse gas emission in landfills along with the characteristics of disposed waste in Korea.

Effect of Soil Texture and Tillage Method on Rice Yield and Methane Emission during Rice Cultivation in Paddy Soil

  • Cho, Hyeon-Suk;Seo, Myung-Chul;Kim, Jun-Hwan;Sang, Wan-gyu;Shin, Pyeong;Lee, Geon Hwi
    • Korean Journal of Soil Science and Fertilizer
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    • v.49 no.5
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    • pp.564-571
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    • 2016
  • As the amount of rice straw collected increases, green manure crops are used to provide the needed organic matter. However, as green manure crops generate methane in the process of decomposition, we tested with different tillage depths in order to reduce the emission. The atmosphere temperature of the chamber was $25{\sim}40^{\circ}C$ during the examination of methane and soil temperature was $2{\sim}10^{\circ}C$ lower than air temperature. The redox potential (Eh) of the soil drastically fell right before irrigated transplanting and showed -300~-400 mV during the cultivating period of rice (7~106 days after transplant). When hairy vetch was incorporated to soil and the field was not irrigated, the generation of methane did not occur from 12 to 4 days before transplanting rice and started after irrigation. Regarding the pattern of methane generation during the cultivation of rice, methane was generated 7 days after transplanting, reached the pinnacle at by 63~74 days after transplanting, rapidly decreased after 86~94 days past transplanting and stopped after 106 days past transplanting. When tested by different soil types, methane emission gradually increased in loam and clay loam during early transplant, whereas it sharply increased in sandy loam. The total amount of methane emitted was highest in sandy loam, followed by loam and clay loam. In all three soil types, methane emission significantly reduced when tillage depth was 20 cm compared to 10 cm. The rice growths and yield were not affected by tillage depth. Therefore, reduction of methane emission could be achieved when application hairy vetch to the soil with tillage depth of 20 cm in paddy soil.

$CH_4$ Gas Sensor Utilizing Pd-SiC Schottky Diode (Pd-SiC 쇼트키 다이오드를 이용한 $CH_4$ 가스센서)

  • 김창교;이주헌;이영환
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.163-166
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    • 1998
  • The mechanism of methane sensing by Pd-SiC diode was investigated over the temperature range of 400~$600^{\circ}C$. The effects or methane gas reaction on the parameters such as barrier height, initial rate of methane gas reaction are investigated. The methane gas reaction kinetics on the device are also discussed. The physical and chemical mechanism responsible for methane detection are proposed. Analysis of steady-state reaction kinetics using I-V method confirmed that methane gas reaction processes are responsible for the barrier height change in the diode.

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Abatement of Methane Production from Ruminants: Trends in the Manipulation of Rumen Fermentation

  • Kobayashi, Yasuo
    • Asian-Australasian Journal of Animal Sciences
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    • v.23 no.3
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    • pp.410-416
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    • 2010
  • Methane emitted from ruminant livestock is regarded as a loss of feed energy and also a contributor to global warming. Methane is synthesized in the rumen as one of the hydrogen sink products that are unavoidable for efficient succession of anaerobic microbial fermentation. Various attempts have been made to reduce methane emission, mainly through rumen microbial manipulation, by the use of agents including chemicals, antibiotics and natural products such as oils, fatty acids and plant extracts. A newer approach is the development of vaccines against methanogenic bacteria. While ionophore antibiotics have been widely used due to their efficacy and affordable prices, the use of alternative natural materials is becoming more attractive due to health concerns regarding antibiotics. An important feature of a natural material that constitutes a possible alternative methane inhibitor is that the material does not reduce feed intake or digestibility but does enhance propionate that is the major hydrogen sink alternative to methane. Some implications of these approaches, as well as an introduction to antibiotic-alternative natural materials and novel approaches, are provided.