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PubMed2003

A methodology to estimate odors around landfill sites: the use of methane as an odor index and its utility in landfill siting.

The estimation of odor production and dispersion from landfill sites is a very complicated task because of the different chemical species that exist in biogas. To site a new landfill, it is necessary to know the distance that odors can travel around the landfill under atmospheric conditions that increase the concentration of pollutants. Although CH4 is an odorless gas, it can be used as an index to determine the dispersion of low-reactivity odorous species around a landfill site. Methane production rates, estimated by biogas production models, were used by an air dispersion model to determine the spatial distribution of CH4 around landfill sites. By utilizing dispersion models under extreme atmospheric conditions, a maximum CH4 concentration around the landfills was determined. Based on the ratio between CH4 and odorous chemical species, the spatial distribution of the concentration of an odorous species was determined for those species with low reactivity in the atmosphere. For odorous species with high reactivity in the atmosphere, a dispersion-reaction model must be used. In this way, the acceptable distance between new landfills and residential areas can be determined. The proposed methodology could be used as a design tool for those who are interested in landfill siting.

Air Pollutants↗
PubMed2004

Performance of an innovative two-stage process converting food waste to hydrogen and methane.

This study was conducted to evaluate the performance of an innovative two-stage process, BIOCELL, that was developed to produce hydrogen (H2) and methane (CH4) from food waste on the basis of phase separation, reactor rotation mode, and sequential batch technique. The BIOCELL process consisted of four leaching-bed reactors for H2 recovery and post-treatment and a UASB reactor for CH4 recovery. The leaching-bed reactors were operated in a rotation mode with a 2-day interval between degradation stages. The sequential batch technique was useful to optimize environmental conditions during H2 fermentation. The BIOCELL process demonstrated that, at the high volatile solids (VS) loading rate of 11.9 kg/m3 x day, it could remove 72.5% of VS and convert VS(removed) to H2 (28.2%) and CH4 (69.9%) on a chemical oxygen demand (COD) basis in 8 days. H2 gas production rate was 3.63 m3/m3 x day, while CH4 gas production rate was 1.75 m3/m3 x day. The yield values of H2 and CH4 were 0.31 and 0.21 m3/kg VS(added), respectively. Moreover, the output from the post-treatment could be used as a soil amendment. The BIOCELL process proved to be stable, reliable, and effective in resource recovery as well as waste stabilization.

Bioelectric Energy Sources↗
PubMedDate not supplied

Determination of carbon monoxide with a modified zeolite sorbent and methanization-gas chromatography.

The purpose of this study was to develop an alternative sorbent sampling technique to concentrate CO from an air sample for subsequent instrumental analysis. Y52 zeolite doped with 9.4 wt % cuprous ions was found to have high capacity, stability to air, and thermal reversibility for CO. The Cu(I)-modified zeolite was packed in glass tubes, preceded by a drying tube containing silica gel. Air was sampled through the tubes at the flow rate of 100 mL/min. Collected CO was thermally desorbed at 300 degrees C and determined by gas chromatography with reduction of CO to methane and flame ionization detection (TD-GC-CH4-FID). Breakthrough capacity of the sorbent was found to be 2.74 mg CO per gram of sorbent. For 2-L air samples containing 12.5 to 100 ppm CO and 50% relative humidity at room temperature, recovery of CO was found to be 96.6% with pooled relative standard deviation of 5.8%. The estimated detection limit for a 2-L sample was 0.2 ppm. Collected CO was stable at room temperature for 1 day and up to 7 days at 4 degrees C if the sorbent tube was flushed with helium before storage. In field testing, the ratio of CO measured by the new technique and by a reference technique was found to be 0.93 with pooled relative standard deviation of 6.3%. This unique new sorbent coupled with TD-GC-CH4-FID shows promise as a sensitive and specific alternative for measurement of CO in air.

Air Pollutants↗
PubMed1981

Effect of methane inhibitors on the metabolism of rumen microbes in vitro.

In incubations in vitro with rumen fluid, the effect of two methane inhibitors, linseed oil hydrolysate (LOH) and chloral hydrate (CH) on the efficiency of microbiol growth was investigated. Total and net microbial growth were determined from 32PO43- and NH3--N incorporation respectively and expressed as g N incorporated per kg organic matter fermented (gN/kgOMf). In a first series on incubations, it was found that LOH had no influence on overall microbial growth efficiency, while with CH, a small but significant decrease of total and net growth efficiency was measured. Further experiments showed that this was not due to accumulation of hydrogen gas in the CH incubations. Microscopic examination showed a toxic effect of LOH on protozoa, but with CH, no such effect was observed. This observation, together with earlier work where a considerable increase in microbial growth efficiency was found in vitro after defaunation of the rumen suggested the following hypothesis: both inhibitors lowered bacterial growth. In the case of LOH, this effect is marked by the defaunating action of LOH, the latter resulting in an increased growth efficiency of the bacterial fraction. This hypothesis was confirmed by incubations with washed cell suspensions (WCS) of mixed rumen bacteria, where growth efficiency was indeed decreased by both inhibitors. The possible mechanism explaining this phenomenon was discussed.

Animals↗
PubMed2005

Methane (CH4) emission from a natural wetland of northern China.

This article focuses on the seasonal and spatial changes of CH4 emission from the natural reed marsh of Liaohe Delta, China. Field experiments showed that this natural wetland acts as a CH4 sink in spring (-30 approximately -1000 microg/m2 x h), a strong source in summer (400-3000 microg/m2 x h) and a weak source in autumn (< 400 microg/m2 x h). Reed plants play an important role in transportation and emission of methane produced in soil. According to our field measurement data, CH4 emission is positively related to temperature, and negatively related to Eh value and water depth. The activity of methanogenic bacteria is higher in the rhizosphere and surface layer, and thus contributes more in CH4 emission than other layers.

China↗
PubMed1998

Experimental W values of low-energy protons in the alkane series from methane to pentane.

Accurate measurements of the mean energy expended in a gas per ion pair formed (W value) for protons slowed down in alkanes are needed (i) in the fields of neutron metrology and microdosimetry, and (ii) in the field of basic radiation research to check the validity of theoretical models describing the degradation of protons in matter. Here, data for protons at energies of less than 100 keV are of particular interest because W increases strongly with decreasing proton energy in the very low-energy region and shows some structure between 10 keV and 100 keV. For these reasons, the energy dependence of W was studied for completely slowed down monoenergetic protons in the alkane series from methane to pentane at energies 1 keV < or = T < or = 100 keV, by measuring the positive ionization yield produced in a plane-parallel ionization chamber. The final results, which have uncertainties of less than 1.5%, are given in tabular form and also in an analytical representation. They were used to determine the differential value omega of the mean energy expended in a gas per ion pair formed and to analyse differences in proton degradation in the alkanes as a function of the number of carbon atoms.

Alkanes↗
PubMed1989

Nonabsorbed carbohydrate: effect on fecal pH in methane-excreting and nonexcreting individuals.

To determine whether the acidifying effect of malabsorbed carbohydrate on fecal pH differed between methane-excreting and nonexcreting individuals, we administered the poorly absorbed disaccharide lactulose to five CH4 excretors and six CH4 nonexcretors. Lactulose, 20 g twice daily for 1 wk, significantly lowered fecal pH among CH4 nonexcretors as compared with CH4-excreting individuals (5.38 +/- 0.66 vs 6.90 +/- 0.61, p less than 0.01). To determine whether this observation was due to differences in acid production from bacterial carbohydrate fermentation, feces from each subject were incubated with lactulose. There were no differences in in vitro acid or hydrogen production between groups. We conclude that malabsorbed carbohydrate fails to induce in vivo colonic acidification in CH4 excretors. In contrast, in vitro fecal carbohydrate fermentation is similar among CH4 excretors and nonexcretors. These results suggest differences between these two groups in the colonic absorption of fermentation products.

Adult↗
PubMed1998

Analysis of dissolved methane, ethane, and ethylene in ground water by a standard gas chromatographic technique.

The measurement of dissolved gases such as methane, ethane, and ethylene in ground water is important in determining whether intrinsic bioremediation is occurring in a fuel- or solvent-contaminated aquifer. A simple procedure is described for the collection and subsequent analysis of ground water samples for these analytes. A helium headspace is generated above a water-filled bottle. Gases that are dissolved in the water partition between the gas and liquid phases and equilibrate rapidly. An aliquot of this headspace is analyzed by gas chromatography to determine the gases concentration in this phase. The concentration of the gas dissolved in the water can then be calculated based on its partitioning properties, as indicated by its Henry's Law constant.

Chromatography, Gas↗
PubMed1993

Mutagenic and lethal effects of halogenated methanes in the Ara test of Salmonella typhimurium: quantitative relationship with chemical reactivity.

The mutagenic and lethal effects of nine halogenated methanes (CCl4, carbon tetrachloride; CHCl3, chloroform; CH2Cl2, dichloromethane; CBr4, carbon tetrachloride; CHBr3, bromoform; CH2Br2, dibromomethane; CI4, carbon tetraiodide; CHI3, iodoform; and CH2I2, diiodomethane) have been investigated with the Ara forward-mutation assay of Salmonella typhimurium. Five substances (CH2Cl2, CBr4, CH2Br2, CHI3 and CH2I2) gave clear mutagenic responses. In all these cases the mutagenicity diminished in the presence of mammalian metabolic activation (S9 mixture). Two halomethanes (CCl4 and CHBr3) were classified as 'questionable' mutagens since they did not double the spontaneous value although a dose-response curve was obtained. All halomethanes tested exerted a lethal effect. A high concordance was found between lethality and chemical reactivity, as expected from the type and number of halogenated substituents. Compounds with equal numbers of substituents were lethal in the order I > Br > Cl. Additionally, the lethality of compounds with identical halogen substituents increased by successive halogenations. No such concordances were observed with respect to mutagenic activity. Structure-activity quantitative relationships were investigated by using the previously reported values of the polarographic half-wave reduction potential (-E1/2), a physicochemical parameter related to the energy required to put an electron into the lowest unoccupied molecular orbital. The lethality, quantified as LD37, correlated highly with the -E1/2 values for the nine halogenated compounds (r = -0.955 P < 0.001). These data suggest that halomethanes which are reduced easily will induce higher lethality than those with low reduction potential, in agreement with the predicted effects on lipid peroxidation and hepatotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-Response Relationship, Drug↗
PubMed1993

Quantitative structure-activity relationship models correctly predict the toxic and aneuploidizing properties of six halogenated methanes in Aspergillus nidulans.

In a previous study, the relationships between the chemical structure and the ability of 35 chlorinated aliphatic hydrocarbons to induce aneuploidy and toxicity in Aspergillus nidulans were analyzed. Quantitative structure-activity relationships (QSAR) were defined for each of the biological activities under study: ARR (the dose able to block mitotic growth), D37 (the dose with 37% of survival) and LEC (the lowest efficient concentration in aneuploidy induction). In this study, these QSAR equations were used to predict the toxic and genetic activity of a further six chemicals, not included in the previous data base: bromotrichloromethane, bromoform, bromochloromethane, bromodichloromethane, dibromochloromethane and dibromochlorofluoromethane. Their ARR, D37 and LEC values were measured, and were in agreement with the predicted values, with correlation coefficients around 0.99. Furthermore, the QSAR model, which had previously been developed to discriminate between aneugenic and inactive halogenated hydrocarbons, correctly predicted the aneugenic activity of five out of six methanes. These correct predictions confirmed the validity of our QSAR model, according to which the induction of aneuploidy in A. nidulans depends on both the electrophilic and steric properties of the chemicals, whereas toxicity mainly depends on steric factors.

Aneuploidy↗
PubMedDate not supplied

Methane gas explosion during colonoscopy.

This article discusses a complication of colonoscopy that healthcare providers think can not happen: methane gas explosion. Despite proper bowel cleansing, such an incident did occur. This article shows how quick recognition and action can save a patient's life. Colonic preparations are also discussed.

Cautery↗
PubMed2002

Methanothermococcus okinawensis sp. nov., a thermophilic, methane-producing archaeon isolated from a Western Pacific deep-sea hydrothermal vent system.

A novel thermophilic, methane-producing archaeon was isolated from a deep-sea hydrothermal vent chimney at the Iheya Ridge, in the Okinawa Trough, Japan. The cells were highly motile, irregular cocci, with a polar bundle of flagella. Growth was observed between 40 and 75 degrees C (optimum 60-65 degrees C; 30 min doubling time) and between pH 4.5 and 8.5 (optimum pH 6.7). The isolate was a strictly anaerobic autotroph capable of using hydrogen and carbon dioxide as sole sources of energy and carbon. Formate can serve as an alternative energy source. The G+C content of the genomic DNA was 33.5 mol%. Phylogenetic analysis based on 16S rDNA sequences and DNA-DNA hybridization analysis indicated that the isolate was closely related to members of the genera Methanococcus and Methanothermococcus. This isolate, however, could be differentiated from the previously described species of these genera on the basis of its physiological and molecular properties. The name Methanothermococcus okinawensis sp. nov is proposed, with the type strain IH1T (=JCM 11175T=DSM 14208T).

DNA, Ribosomal↗
PubMed1988

Effect of nitrate on methane production and fermentation by slurries of human faecal bacteria.

Most probable number counts showed that denitrifying species were the numerically predominant NO3- reducing bacteria in the faeces of five methanogenic individuals [about 10(10) bacteria (g dry wt faeces)-1]. In faecal slurries, however, denitrification was a relatively minor route of NO3- dissimilation, since only about 3% of the NO3- was converted to gaseous products, with NO3- being mainly reduced to NO2- and NH4+. When KNO2 was added to the slurries, denitrification became quantitatively more significant with approximately 23% of the NO2- being lost as gaseous products. The addition of KNO3 (10 mM) to slurries containing either starch or casein significantly decreased H2 and CH4 production. The effect of NO3- on methanogenesis was twofold: firstly, H2 accumulation decreased due to diversion of electrons towards NO3-/NO2- reduction, and as a result of H2 being used as an electron donor for NO3- reduction, resulting in the removal of the methanogenic substrate; secondly, there was direct inhibition of methane-producing bacteria by NO3- and NO2-. In starch-containing slurries, acetate: butyrate molar ratios were increased when NO3- was added but this effect was not observed when casein replaced starch. These results show that the ability of NO3-/NO2- to act as an electron sink can significantly influence the major products of the human colonic fermentation.

Bacteria↗
PubMed2004

Methylobacterium populi sp. nov., a novel aerobic, pink-pigmented, facultatively methylotrophic, methane-utilizing bacterium isolated from poplar trees (Populus deltoides x nigra DN34).

A pink-pigmented, aerobic, facultatively methylotrophic bacterium, strain BJ001T, was isolated from internal poplar tissues (Populus deltoidesxnigra DN34) and identified as a member of the genus Methylobacterium. Phylogenetic analyses showed that strain BJ001T is related to Methylobacterium thiocyanatum, Methylobacterium extorquens, Methylobacterium zatmanii and Methylobacterium rhodesianum. However, strain BJ001T differed from these species in its carbon-source utilization pattern, particularly its use of methane as the sole source of carbon and energy, an ability that is shared with only one other member of the genus, Methylobacterium organophilum. In addition, strain BJ001T is the only member of the genus Methylobacterium to be described as an endophyte of poplar trees. On the basis of its physiological, genotypic and ecological properties, the isolate is proposed as a member of a novel species of the genus Methylobacterium, Methylobacterium populi sp. nov. (type strain, BJ001T=ATCC BAA-705T=NCIMB 13946T).

Aerobiosis↗
PubMed2004

Methanotorris formicicus sp. nov., a novel extremely thermophilic, methane-producing archaeon isolated from a black smoker chimney in the Central Indian Ridge.

A novel extremely thermophilic, methane-producing archaeon was isolated from a black smoker chimney at the Kairei field in the Central Indian Ridge. Cells of this isolate were irregular cocci with several flagella; motility was not observed. Growth was observed between 55 and 83 degrees C (optimum of 75 degrees C; 30 min doubling time) and between pH 6.0 and 8.5 (optimum of pH 6.7). The isolate was a strictly anaerobic, methanogenic autotroph capable of using hydrogen and carbon dioxide as sole energy and carbon sources. Formate was utilized as an alternative energy source. The G+C content of the genomic DNA was 33.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate was most closely related to Methanotorris igneus strain Kol 5T. The isolate, however, could be genetically differentiated from this species by DNA-DNA hybridization analysis and on the basis of its physiological properties. The name Methanotorris formicicus sp. nov. is proposed for this isolate; the type strain is Mc-S-70T (=JCM 11930T=ATCC BAA-687T).

Anaerobiosis↗
PubMed2005

Hydrogen concentrations in methane-forming cells probed by the ratios of reduced and oxidized coenzyme F420.

Coenzyme F420 is the central low-redox-potential electron carrier in methanogenic metabolism. The coenzyme is reduced under hydrogen by the action of F420-dependent hydrogenase. The standard free-energy change at pH 7 of F420 reduction was determined to be -15 kJ mol(-1), irrespective of the temperature (25-65 degrees C). Experiments performed with methane-forming cell suspensions of Methanothermobacter thermautotrophicus incubated under various conditions demonstrated that the ratios of reduced and oxidized F420 were in thermodynamic equilibrium with the gas-phase hydrogen partial pressures. During growth in a fed-batch fermenter, ratios changed in connection with the decrease in dissolved hydrogen. For most of the time, the changes were as expected for thermodynamic equilibrium between the oxidation state of F420 inside the cells and extracellular hydrogen. Also, methanol-metabolizing, but not acetate-converting, cells of Methanosarcina barkeri maintained the ratios of reduced and oxidized coenzyme F420 in thermodynamic equilibrium with external hydrogen. The results of the study demonstrate that F420 is a useful probe to assess in situ hydrogen concentrations in H2-metabolizing methanogens.

Acetates↗
PubMed2005

Production of H2 by sulphur-deprived cells of the unicellular cyanobacteria Gloeocapsa alpicola and Synechocystis sp. PCC 6803 during dark incubation with methane or at various extracellular pH.

AIMS: To examine sulphur (S) deprivation in combination with the presence of methane (CH4) and changes in extracellular pH as a method to enhance in situ hydrogen (H2) generation during fermentation in the unicellular non-diazotrophic cyanobacteria Gloeocapsa alpicola and Synechocystis PCC 6803. METHODS AND RESULTS: The level of H2 production, measured using a gas chromatography, was determined in S-deprived cells of G. alpicola and Synechocystis PCC 6803 during fermentation. Starvation on S enhanced the rate of H2 production by more than fourfold in both strains. S-deprived cyanobacteria were able to maintain maximum rate of H2 production during at least 8 h of fermentation representing the entire dark period of a day. Increased H2 production was observed during dark anoxic incubation with a gas phase of 100% CH4 (up to four times) at lower pH of the medium (5.0-5.5). CONCLUSIONS: S-deprivation in combination with CH4, added or maybe produced by another micro-organisms, and changes in the pH of the media can be used to further increase the specific capacity of unicellular non-N2-fixing cyanobacteria to produce H2 during fermentation with the overall aim of applying it for outdoor photobiological H2 production. SIGNIFICANCE AND IMPACT OF THE STUDY: S-deprivation with respect to H2 production is well studied in the green algae Chlamydomonas reinhardtii while its application for H2 production in cyanobacteria is novel. Similarly, the stimulation of H2 generation in the presence of CH4 opens up new possibilities to increase the H2 production. Natural gas enriched with H2 seems to be a perspective fuel and may be an intermediate step on the pathway to the exploitation of pure biohydrogen.

Bacteriological Techniques↗
PubMed1992

Biological methane activation involves the intermediacy of carbon-centered radicals.

The spin-trapping technique has demonstrated that carbon-centered radicals are produced during soluble-methane-monooxygenase catalysis of the hydroxylation of several different types of substrate. The resulting spin-adducts were identified from the hyperfine splitting constants in their EPR spectra. Isotopic labelling showed unequivocally that the trapped radicals were derived from substrate. The carbon-centered substrate radicals are believed to result from hydrogen-atom abstraction by a ferryl species in a cytochrome-P-450-like mechanism. No hydroxy radical nor an oxygen-based radical of any kind was detected in any of the spin-trapping experiments.

Carbon↗