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PubMed2001

Production and oxidation of methane at low temperature by the microbial population of municipal sludge checks situated in north-east Europe.

Methanogenic and methane-oxidizing activities of the microbial population of sewage sludge checks (Moscow and Syktyvkar regions) were studied at temperatures ranging from 5 to 25 degrees C. The number of methanogens in silt samples reached 10(10) cells/ml. A temperature decrease from 25 to 5 degrees C led to a sharp decrease of methanogenesis in the silt samples. Nevertheless, methanogenesis was still significant even at 5 degrees C. Different organic substrates, including polymeric and aromatic compounds, were degraded with methane production at 6 degrees C. At depths of 20-40 cm the number of methanotrophic bacteria reached 10(11) cells/ml. Methane oxidative activity of the microbial populations in the silt was less sensitive to the 25 degrees to 5 degrees C temperature decrease. Ten methanotrophic species, able to grow at 6 degrees C, were enriched from the Syktyvkar sludge lagoon and identified by indirect immunofluorescence. Enrichments obtained from the Syktuvkar region (62 N) contained more species of methane oxidizing bacteria able to grow at low temperature then methanogenic enrichments obtained from Moscow region (56 N).

Europe↗

PubMed2002

[A backward trajectory inversion model for methane emission over Beijing area].

A Backward trajectory inversion model was established for estimating methane emission over Beijing area, with in situ data of methane measurement. The model was systematically tested for its ability on reflecting diffusion processes in atmospheric boundary layers. In specific condition, the model acted excellently on calculating emission strength and distribution over an area of 100 km scale. By applying to Beijing area with 9 days real methane data and practice meteorological data, the model showed source patches in this area with emission rate 0.0066-0.026 mg/(m2.s), which was correspond well to rice fields emission, the major methane source, in this region. Model results of source patches also showed certain spatial correlation with rice fields distribution.

China↗

PubMed2003

Evaluation of the current status of operating and closed landfills in Russia, Finland and Ireland with regard to water pollution and methane emission.

The annual production of municipal solid wastes (MSW) in Russia, Finland and Ireland in the late 1990s accounts for 37.5, 2.5 and 2.05 min. tonnes or 252, 488 and 566 kg per capita, respectively. 96.5, 64 and 91% of these wastes (for Russia, Finland and Ireland, correspondingly) are currently disposed of via landfilling. However, nowadays, MSW management in these countries is undergoing drastic changes (source separation, closure of old landfills, reduction of the number of landfills etc.) forced by recent legislation set by the European Union and Russian authorities. This paper evaluates the current status of MSW landfills, as well as information on current leachate and methane emissions in the three above mentioned countries. Landfill leachates are highly variable in each country and between different countries due to different rainfall and climatic conditions and also due to poor landfill top insulation/cover. Leachates in poorly structured landfills are very dilute, whereas leachates with total COD and nitrogen contents as high as 33,700 mg COD/l and 4,030 mg N/l, respectively, have been detected from state-of-the-art sites. Currently, on-site treatment of leachates exists at only a few landfills in Russia, Finland and Ireland but this situation will be considerably improved during the next years. The annual methane emissions from landfills are estimated as 500-900 and 77 ktonnes for Russia and Finland, respectively. Recent estimates from Ireland suggest an annual landfill methane emission of c. 2.1 Mt CO2 equivalent. Several systems of methane recovery have been developed in all three countries and these are currently in different stages of implementation.

Environmental Monitoring↗

PubMed2003

Solubilization of waste activated sludge by alkaline pretreatment and biochemical methane potential (BMP) tests for anaerobic co-digestion of municipal organic waste.

Biochemical methane potential (BMP) tests have been carried out to determine the anaerobic digestibility of the waste activated sludge (WAS) and the sludge pretreated by NaOH (PWAS). The optimal NaOH dosage was determined to be 45 meq NaOH/L. The maximum SCOD solubilization was 27.7, 31.4 and 38.3% at the temperatures of 25, 35 and 55 degrees C respectively after 4 hours reaction. The final methane yield of simulated food waste (SFW) was 430 ml CH4/g VS(added), and those of PWAS (25 degrees C), PWAS (35 degrees C) and PWAS (55 degrees C) was 274, 286 and 310 ml CH4/g VS(added) respectively after 20 days. The figures were 66%, 73% and 88% higher than that of WAS. The methane production in anaerobic co-digestion is considerably affected by the fraction of SFW and PWAS in the feed. The anaerobic digestibility of the feed mixture (SFW with PWAS) is higher than that of the feed mixture (SFW with WAS). Anaerobic co-digestion of food waste with the PWAS is found to be an attractive option to reduce the solid waste volume with improved methane recovery.

Bacteria, Anaerobic↗

PubMedDate not supplied

[Microbiological oxidation of methane in the stratal waters of the Lower Volgian].

Methanotrophic bacteria are rather widely distributed in bed waters of oil and gas deposits in the Nizhneye Povolzhye. Their number reaches 250 cells per 1 ml of water. However, bacterial methane oxidation is active only in waters whose redox potential exceeds +250 mV. In a number of cases, microbial methane oxidation is limited by the absence of oxygen from bed waters. If air is added to samples of such water, methane dissolved in the water is oxidized by microorganisms at a high rate (2--451 X 10(-4) cm3 of methane per litre of water per day).

Geological Phenomena↗

PubMed2005

[Methanogens and manipulation of methane production in the rumen].

Methanogens belong to the kingdom of Euryarchaeota in the domain of Archaea. They are characterized by their ability to produce methane under anaerobic conditions. Methane production in the rumen represents a loss of energy for the host animal, and, in addition, methane eructated by ruminants may contribute to a greenhouse effect or global warming. Reduction or elimination of methanogenesis in the rumen has been touted as a way of improving animal production and may marginally benefit to control of anthropogenic release of methane. More and more scientists focus on ruminal methanogens and methanogenesis recently. Authors summarized the manipulation of methanogenesis in the rumen, including defaunation, feed formulation, adding electron acceptors and stimulation of acetogens. The characteristics of methanogenic Archaea and the recent knowledge of the methanogenesis in the rumen were also reviewed in this article.

Animals↗

PubMedDate not supplied

[Physicochemical and biological factors affecting atmospheric methane oxidation in gray forest soils].

The decline of methane oxidizing activities in gray forest soil upon its conversion into arable land was shown to be caused by major changes in biotic and physicochemical properties of soil. Using the method of immune serums, methane-oxidizing bacteria were detected in both forest and agricultural soils, but their populations differed significantly in both abundance and composition. In the forest soil, the number of methanotrophs was an order of magnitude higher than in arable soil, amounting to 3.5 x 10(8) and 0.24 x 10(8) cells/g soil, respectively. All methane-oxidizing bacteria identified in the forest soil belonged to the genus Methylocystis, and 94% of these were represented by a single species, M. parvus. The arable soil was dominated by type I methanotrophs (Methylobacter and Methylomonas, 67.6%), occurring along with bacteria of the genus Methylocystis. In addition, arable soil is characterized by a low content of microbial biomass, lower porosity and water permeability of soil aggregates, and the predominance of nitrogen mineralization processes over those of nitrogen immobilization. These factors can also contribute to lower rates of methane oxidation in arable soil as compared to forest soil.

Agriculture↗

PubMed1989

Methane production in patients with colorectal carcinoma.

In searching for a screening test to identify a population at high risk for large bowel cancer, methane production was measured in 45 patients with colorectal carcinoma compared with 67 individuals who served as a control group. There was no significant difference in methane production between the colorectal cancer patients and the control group (37.8 and 25.4% respectively). Within the colorectal cancer group 54% of the males were methane producers compared with 19% of the females (P = 0.03). There were no differences according to disease stage. In view of these results, we see little value in using expired air methane concentration as a screening test for large bowel cancer.

Breath Tests↗

PubMed1986

Is human methane production affected by long-term occupational exposure to a methanogenic flora?

The factors determining human methane production or nonproduction are unknown. Exposure at a young age to a methanogenic flora is thought to be of significance. We examined whether long-term occupational exposure to methanogenic flora in adult life affects methane production. Among 38 subjects who worked in a cowshed for a mean period of 14 +/- 15 years, the proportion of methane producers was identical to that found in well-matched controls. The length of work in the cowshed had no effect on methane production.

Adolescent↗

PubMed1982

[Role of CO-binding cytochrome c in enzymatic oxidation of methane by the bacterium Methylococcus capsulatus].

The cytochrome c spectrally related to cco cytochromes has been isolated and purified from the methane-oxidizing bacterium Methylococcus capsulatus. The cytochrome binds CO but does not bind other substrates of methane monooxygenase, does not activate the methane monooxygenase reaction and is not a component of methane monooxygenase. In the methanol dehydrogenase enzymatic system cytochrome cco functions as electron acceptor. A possible role of cytochrome cco as electron carrier intermediate in the sequence of the dehydrogenase and oxidase enzymatic systems of M. capsulatus is discussed.

Carbon Monoxide↗

PubMedDate not supplied

[The multiphase character of methane fermentation of cellulose].

An enrichment culture producing methane from cellulose was studied. The culture is a system of changing microbial populations realizing various pathways of methane formation. This change of microbial associations is expressed in three phases of growth; each phase is characterized by its maximum of methane production. The first maximum is related to accumulation and utilization of propionic acid. The second maximum is due to methane formation from acetate by Methanosarcina. One of the possible pathways regulating the methanogenous ecosystem is the action of concentrations of the main metabolites--glucose and the products of its fermentation.

Bacteria↗

PubMed2003

Structural and dynamical properties of methane clathrate hydrates.

Equilibrium molecular dynamics (MD) simulations have been performed in both the NVT and NPT ensembles to study the structural and dynamical properties of fully occupied methane clathrate hydrates at 50, 125, and 200 K. Five atomistic potential models were used for water, ranging from fully flexible to rigid polarizable and nonpolarizable. A flexible and a rigid model were utilized for methane. The phonon densities of states were evaluated and the localized rattling modes for the methane molecules were found to couple to the acoustic phonons of the host lattice. The calculated methane density of states was found to be in reasonable agreement with available experimental data.

Journal Article↗

PubMed2002

Mechanistic study of partial oxidation of methane to syngas using in situ time-resolved FTIR and microprobe Raman spectroscopies.

In situ time-resolved Fourier transform infrared (FTIR) and microprobe Raman spectroscopies were used to characterize the reaction mechanisms of the partial oxidation of methane to syngas over SiO(2)- and gamma-Al(2)O(3)-supported rhodium and ruthenium catalysts. The interaction of both pure methane and a methane/oxygen mixture at a stoichiometric feed ratio with an oxygen-rich catalyst surface led to the formation of CO2 and H(2)O as the primary products. For the H(2)-pretreated samples, the reaction mechanisms with the catalysts differ. Only Rh/SiO(2) is capable of catalyzing the direct oxidation of methane to syngas, while syngas formation over Rh/gamma-Al(2)O(3), Ru/SiO(2), and Ru/gamma-Al(2)O(3) can be achieved mainly via a combustion-reforming scheme. The significant difference in the mechanisms for partial oxidation of methane to syngas over the catalysts can be correlated to the differences in the concentration of oxygen species (O(2-)) on the catalyst surface during the reaction, mainly due to the difference in the nature of the metals and supports.

Journal Article↗

PubMed2001

Thermodynamic and Kinetic Requirements in Anaerobic Methane Oxidizing Consortia Exclude Hydrogen, Acetate, and Methanol as Possible Electron Shuttles.

Anaerobic methane oxidation (AMO) has long remained an enigma in microbial ecology. In the process the net reaction appears to be an oxidation of methane with sulfate as electron acceptor. In order to explain experimental data such as effects of inhibitors and isotopic signals in biomarkers it has been suggested that the process is carried out by a consortium of bacteria using an unknown compound to shuttle electrons between the participants. The overall change in free energy during AMO with sulfate is very small (?22 kJ mol-1) at in situ concentrations of methane and sulfate. In order to share the available free energy between the members of the consortium, the concentration of the intermediate electron shuttle compound becomes crucial. Diffusive flux of a substrate (i.e, the electron shuttle) between bacteria requires a stable concentration gradient where the concentration is higher in the producing organism than in the consuming organism. Since changes in concentrations cause changes in reaction free energies, the diffusive flux of a catabolic product/substrate between bacteria is associated with a net loss of available energy. This restricts maximal inter-bacterial distances in consortia composed of stationary bacteria. A simple theoretical model was used to describe the relationship between inter-bacterial distances and the energy lost due to concentration differences in consortia. Key parameters turned out to be the permissible concentration range of the electron shuttle in the consortium (i.e., the concentration range that allows both participants to gain sufficient energy) and the stoichiometry of the partial reactions. The model was applied to two known consortia degrading ethanol and butyrate and to four hypothetical methane-oxidizing consortia (MOC) based on interspecies transfer of hydrogen, methanol, acetate, or formate, respectively. In the first three MOCs the permissible distances between producers and consumers of the transferred compounds were less than two times prokaryotic cell wall diameters. Consequently, it is not possible that a MOC can be based on inter-species transfer of hydrogen, methanol, or acetate. Formate, on the other hand, is a possible shuttle candidate provided the bacteria are attached to one another. In general the model predicts that members of consortia thriving on low energy such as the MOC must adhere to each other and utilize a compound for the exchange of electrons that has a high permissible concentration range and a high diffusion coefficient and transfers as many electrons as possible per molecule.

Journal Article↗

PubMed1994

Landfill site restoration: the inimical challenges of ethylene and methane.

Vertically migrating landfill gases pose inimical challenges to site revegetation strategies. Laboratory studies were made to examine the efficacy of ectomycorrhizae and soil cover to obviate the challenges of ethylene and methane. In the presence of ethylene concentrations </= 640 ppm the mean colony radial extension rates of the fungal isolates Laccaria proxima, Paxillus involutus and Hebeloma crustuliniforme were comparable with the non-ethylene controls. H. crustuliniforme afforded no protection to Betula pendula (Silver Birch) seedlings. Methane removal by the soil cover may be important to minimise the indirect phytotoxic effects of methane on tree seedlings. In closed culture enrichments with refuse as inoculum source material methanogenesis consistently exceeded methanotrophy even after major oxygen perturbations. With subsoil and topsoil, however, net methane concentrations decreased, thus emphasising the importance of these cover materials in site restoration strategies.

Journal Article↗

PubMed1995

The measurement of methane losses from grazing animals.

A detailed description is given of the construction, operation and calibration of a system designed to measure methane emissions from sheep grazing in the field under as near natural conditions as possible. Results from four preliminary studies show that emission of methane averaged 14 g day(-1) per animal, equivalent to 5.1 kg year(-1) per animal. These rates, although lower than some estimates, confirm that methane emission from sheep forms a significant proportion of the total methane emissions currently attributed to UK agriculture.

Journal Article↗

PubMed2004

Myristic acid supports the immediate inhibitory effect of lauric acid on ruminal methanogens and methane release.

Two in vitro experiments were carried out with the Hohenheim gas test (HGT) apparatus in order to investigate dose-dependent effects and interactions of non-esterified lauric acid (C(12)) and myristic acid (C(14)) given either individually or in mixture on ruminal methanogens and methanogenesis. Special emphasis was also put on the relationship between effects on methane formation and methanogenic counts. The in vitro incubations were conducted in 10mL ruminal fluid and 20mL buffer solution and lasted for 24h. In the first experiment, 14 levels of C(12), C(14) and stearic acid (C(18); control) were supplied each in increasing steps of 2.5mg covering the range from 0 to 32.5mg. In the second experiment, dosages ranging from 2.5 to 30mg C(12) were supplemented in steps of 2.5mg either without or with 10, 20 or 30mg of C(14). Counts of total Archaea and individual methanogenic orders were determined by the fluorescence in situ hybridization technique using 16S rRNA oligonucleotide probes. In experiment 1, a methane-suppressing effect of more than 80% was achieved with a supply of 30mg C(12), whereas C(14) and C(18) had no effect. Incubation liquid counts of total Archaea and individual methanogenic orders (Methanococcales, Methanosarcinales, Methanomicrobiales and Methanobacteriales) exponentially decreased as a response to C(12) and C(14) to about the same degree (up to 90%) and, to a lesser extent, by C(18). The proportions of the orders of total methanogenic population were not altered by any of the fatty acids. In experiment 2, an additional supply of 10 or 20mg of C(14) supported the suppression of methanogenesis and methanogens by C(12) synergistically. Supplementing 30mg instead of 20mg of C(14) did not further increase the efficacy of C(12) in suppressing methane formation and methanogens. The study illustrated the advantage of using mixtures of C(12) and C(14) in ruminant nutrition to suppress methane emission since mixtures will reduce the amounts of the less palatable C(12) required in feed.

Journal Article↗

PubMed2005

Monte Carlo and molecular dynamics simulations of methane in potassium montmorillonite clay hydrates at elevated pressures and temperatures.

The structure and dynamics of methane in hydrated potassium montmorillonite clay have been studied under conditions encountered in sedimentary basin and compared to those of hydrated sodium montmorillonite clay using computer simulation techniques. The simulated systems contain two molecular layers of water and followed gradients of 150 bar km(-1) and 30 K km(-1) up to a maximum burial depth of 6 km. Methane particle is coordinated to about 19 oxygen atoms, with 6 of these coming from the clay surface oxygen. Potassium ions tend to move away from the center towards the clay surface, in contrast to the behavior observed with the hydrated sodium form. The clay surface affinity for methane was found to be higher in the hydrated K-form. Methane diffusion in the two-layer hydrated K-montmorillonite increases from 0.39 x 10(-9) m2 s(-1) at 280 K to 3.27 x 10(-9) m2 s(-1) at 460 K compared to 0.36 x 10(-9) m2 s(-1) at 280 K to 4.26 x 10(-9) m2 s(-1) at 460 K in Na-montmorillonite hydrate. The distributions of the potassium ions were found to vary in the hydrates when compared to those of sodium form. Water molecules were also found to be very mobile in the potassium clay hydrates compared to sodium clay hydrates.

Journal Article↗