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PubMed1988

Breath methane and large bowel cancer risk in contrasting African populations.

Breath methane has been measured in 1016 people from four populations resident in Southern Africa which experience widely different risks of bowel cancer and other colonic diseases. Highly significant differences in the proportion of subjects with detectable methane in breath were found; % producers--rural black 84, urban black 72, white 52, Indian 41 (chi 2 121 p less than 0.001 3 df). There was a slight preponderance of female producers over male (female producers 63%, males 57%) and an age trend with fewer producers in the older age groups in the urban blacks and Indians, these comparisons being significant when tested by stepwise logistic regression analysis. Bowel cancer risk, determined from a variety of sources, was lowest in rural blacks, greatest in whites, with intermediate rates for urban blacks and Indians. Methane production in the human colon shows significant interethnic differences but which bear no relation to bowel cancer risk in these populations.

Adolescent↗

PubMed1976

Factors affecting rate of methane formation from acetic acid by enriched methanogenic cultures.

A stable enrichment culture converting acetic acid to methane was successfully obtained from a pear waste digester, using a synthetic substrate solution with acetic acid as the main carbon source. This enrichment culture converted up to 10 mmol of acetic acid per litre per day at 35 degrees C and did not use hydrogen or formic acid in appreciable amounts as substrate for methane production instead of, or in addition to, acetic acid. The rate of conversion of acetic acid to methane was maximum at temperature of 40-45 degrees C, at a pH of 6.5 to 7.1, and was adversely affected by exposure to air, reducing agents, and high salt concentrations. The rate of conversion was independent of acetic acid concentration between 0.2 and 100 mM, but dropped markedly at concentrations below 0.2 mM.

Acetates↗

PubMed2005

[Potential activity of methane production in soil, peat, and lacustrine sediments and in the Robert Bourassa hydro-electric reservoir in northern Canada].

Flooding of land associated with the creation of reservoirs may increase, at least in the short term, methane flux to the atmosphere. To evaluate the potential contribution of such land use on methane production, field samples were studied in vitro for the potential activity of methanogenic bacteria in unflooded or flooded boreal forest soils, together with lacustrine sediments. From this comparative study, periodically flooded or flooded peats contribute more to methane production than do unflooded peats, soils, and natural lake sediment. The intensity and temporal changes in the activity of methanogenic archaea in the different systems depended on a combination of environmental factors, such as the amount and quality of organic carbon, the water level, and the concentration of oxidizing ions (SO42-, Fe3+).

Archaea↗

PubMed1980

Methane negative chemical ionization analysis of 1,3-dihydro-5-phenyl-1,4-benzodiazepin-2-ones.

The methane negative chemical ionization (NCI) mass spectra of the medically important 1,3-dihydro-5-phenyl-1,4-benzodiazepin-2-ones generally consisted solely of M- and (M-H)- ions. Attempts to find the location of the H lost in the generation of the (M-H)- ion were unsuccessful, although many possibilities were eliminated. A Hammett correlation analysis of the relative sensitivities of a series of 7-substituted benzodiazepines suggested that the initial ionization takes place at the 4,5-imine bond. For certain benzodiazepines, the (M-H)- ion generated by methane NCI was 20 times more intense than the MH+ ion generated by methane positive chemical ionization (PCI). By using NCI, a sensitive and simple GC-MS assay for nordiazepam was developed that can quantitate this important metabolite of many of the clinically used benzodiazepines in the blood and brain of rats.

Animals↗

PubMed1999

Measurement for breath concentration of hydrogen and methane in horses.

This study concerns the establishment of a simple testing method for breath concentration of hydrogen and methane in horses. Twenty-eight healthy thoroughbreds and 24 Arabians were used. Breath samples were collected using one-minute closed circulatory respiration through an aluminum bag filled with 10 liters of pure oxygen, which was mounted on the subjects by means of a face mask. Breath samples obtained, were analyzed by gas chromatography. A significant correlation in both hydrogen and methane levels was observed for samples collected at separate times. These findings confirmed the usefulness of our approach for testing breath concentrations of hydrogen and methane in horses.

Abdomen, Acute↗

PubMed1999

Bioremediation of trichloroethylene and cis-1,2-dichloroethylene-contaminated groundwater by methane-utilizing bacteria.

Experimental studies on the bioremediation of groundwater contaminated with low concentration trichloroethylene (TCE) and cis1,2-dichloroethylene (DCE) were performed with two sets of bioreactors. Reactors No. 1 and No. 2 were operated without and with methane supplement, respectively. No inoculum was used. The concentrations of TCE and DCE in the effluent and the off gas from reactor No. 2 were much lower than those from reactor No. 1. When air and an H2O2 solution were supplied to reactor No. 2, concentrations of TCE and DCE in the effluent and the off gas were lower than the lowest detectable limit. The population of methane-utilizing bacteria in reactor No. 2 was 1,000 times higher than that in groundwater or in the effluent from reactor No. 1. These methane-utilizing bacteria were apparently attributable to the treatment of TCE.

Biodegradation, Environmental↗

PubMed1999

Two-phase methanization of food wastes in pilot scale.

A 5 ton/d pilot scale two-phase anaerobic digester was constructed and tested to treat Korean food wastes in Anyang city near Seoul. The easily degradable presorted food waste was efficiently treated in the two-phase anaerobic digestion process. The waste contained in plastic bags was shredded and then screened for the removal of inert materials such as fabrics and plastics, and subsequently put into the two-stage reactors. Heavy and light inerts such as bones, shells, spoons, and plastic pieces were again removed by gravity differences. The residual organic component was effectively hydrolyzed and acidified in the first reactor with 5 d space time at pH of about 6.5. The second, methanization reactor converted the acids into methane with pH between 7.4 and 7.8. The space time for the second reactor was 15 d. The effluent from the second reactor was recycled to the first reactor to provide alkalinities. The process showed stable steady-state operation with the maximum organic loading rate of 7.9 kg volatile solid (VS)/m3/d and the volatile solid reduction efficiency of about 70%. The total of 3.6 tons presorted MSW containing 2.9 tons of food organic was treated to produce about 230 m3 of biogas with 70% (v/v) of methane and 80 kg of humus. This process is extended to full-scale treating 15 tons of food waste a day in Euiwang city and the produced biogas is utilized for the heating/cooling of adjacent buildings.

Bacteria, Anaerobic↗

PubMed2006

Mosquito larval habitat mapping using remote sensing and GIS: implications of coalbed methane development and West Nile virus.

Potential larval habitats of the mosquito Culex tarsalis (Coquillett), implicated as a primary vector of West Nile virus in Wyoming, were identified using integrated remote sensing and geographic information system (GIS) analyses. The study area is in the Powder River Basin of north central Wyoming, an area that has been undergoing a significant increase in coalbed methane gas extractions since the late 1990s. Large volumes of water are discharged, impounded, and released during the extraction of methane gas, creating aquatic habitats that have the potential to support immature mosquito development. Landsat TM and ETM+ data were initially classified into spectrally distinct water and vegetation classes, which were in turn used to identify suitable larval habitat sites. This initial habitat classification was refined using knowledge-based GIS techniques requiring spatial data layers for topography, streams, and soils to reduce the potential for overestimation of habitat. Accuracy assessment was carried out using field data and high-resolution aerial photography commensurate with one of the Landsat images. The classifier can identify likely habitat for ponds larger than 0.8 ha (2 acres) with generally satisfactory results (72.1%) with a lower detection limit of approximately 0.4 ha (1 acre). Results show a 75% increase in potential larval habitats from 1999 to 2004 in the study area, primarily because of the large increase in small coalbed methane water discharge ponds. These results may facilitate mosquito abatement programs in the Powder River Basin with the potential for application throughout the state and region.

Animals↗

PubMedDate not supplied

Methane oxidation and production activity in soils from natural and agricultural ecosystems.

Methane (CH4) flux from soil to the atmosphere is the result of two microbial processes, methanogenesis and CH4 oxidation. Land use may have a profound impact on the relative activities of these groups of organisms. In this study, the CH4 production and consumption potentials of soils from agricultural and nonagricultural ecosystems were assessed in laboratory incubations. Methane production potentials of most soils were low and in the range of 0.02 to 0.35 nmol CH4 g soil(-1) h(-1); however, soils from two of the agricultural sites that experience periodic water saturation had CH4 production potentials from 100 to 300 nmol CH4 g soil(-1) h(-1). The high methanogenic potential suggests that CH4 consumers may not be wholly dependent on atmospheric CH4 for their survival and maintenance. The prairie soils exhibited the highest CH4 oxidation under ambient atmospheric CH4 concentrations, and CH4 oxidation activity was markedly enhanced in incubations with an atmosphere enriched in CH4. This stimulated CH4 oxidation activity was generally greater in the agricultural soils as compared with the forest and prairie soils. Methane oxidation appeared to be related to soil nitrogen status. Under ambient atmospheric CH4 concentrations, CH4 oxidation was negatively related to soil mineral N (NO2- + NO3- + NH4+) concentration. However, a positive relationship between soil mineral N status and CH4 oxidation activity was observed in incubations with atmospheres enriched in CH4. This pattern suggests that the agricultural lands contain different populations of CH4 oxidizers than the natural systems.

Agriculture↗

PubMedDate not supplied

Methane emissions of beef cattle on forages: efficiency of grazing management systems.

Fermentation in the rumen of cattle produces methane (CH4). Methane may play a role in global warming scenarios. The linking of grazing management strategies to more efficient beef production while reducing the CH4 emitted by beef cattle is important. The sulfur hexafluoride (SF6) tracer technique was used to determine the effects of best management practices (BMP) grazing compared with continuous grazing on CH4 production in several Louisiana forages during 1996-1998. Cows and heifers (Bos taurus) grazed common bermudagrass [Cynodon dactylon (L.) Pers.], bahiagrass (Paspalum notatum Flugge), and ryegrass (Lolium multiflorum Lam.) pastures and were wintered on bahiagrass hay with supplements of protein molasses blocks (PMB), cottonseed meal and corn (CSMC), urea and corn (URC), or limited ryegrass grazing (LRG). Daily CH4 emissions were between 89 and 180 g d(-1) for young growing heifers and 165 to 294 g d(-1) for mature Simbrah cows. Heifers on "ad lib" ryegrass in March and April produced only one-tenth the CH4 per kg of gain as heifers on LRG of 1 h. Using BMP significantly reduced the emission of CH4 per unit of animal weight gain. Management-intensive grazing (MIG) is a BMP that offers the potential for more efficient utilization of grazed forage crops via controlled rotational grazing and more efficient conversion of forage into meat and milk. Projected CH4 annual emissions in cows reflect a 22% reduction from BMP when compared with continuous grazing in this study. With the BMP application of MIG, less methane was produced per kilogram of beef gain.

Animal Husbandry↗

PubMed2006

Methane production and solids destruction in an anaerobic solid waste reactor due to post-reactor caustic and heat treatment.

This study was undertaken to determine the feasibility of caustic and heat treatment of sludge from a dry anaerobic reactor (DAR) with respect to increased methane production and solids destruction. The DAR was operated semi-continuously at 55 degrees C on sized-reduced municipal solid waste at a solids retention time of 15 days. A respirometer was employed to monitor the extent and rate of methane production from anaerobic biodegradation of DAR sludge that was treated with caustic and heat. Results indicate that caustic and heat treatment at 50 degrees C and 175 degrees C increased methane production by 22% and 52%, respectively. Also, volatile solids destruction increased from 46% to 58% and 83%, respectively. Based on these results, economic analysis for a full-scale 10(5) kg/d facility suggests that annual project revenue for 50 degrees C and 175 degrees C treatment is estimated at $21,000 and $445,000, respectively.

Anaerobiosis↗

PubMed1996

In vitro inhibition of microbial methane production by 9,10-anthraquinone.

Monensin, 2,2-dichloroacetamide, and 9,10-anthraquinone were incubated for 24 h in ruminal fluid and buffer with 100:0, 50:50, and 10:90 forage-concentrate diets. Monensin (.5 ppm of the fluid) increased (P < .05) the molar proportion of propionate in the 50 and 100% forage diets but not in the high concentrate diet. At the same level of addition, 2,2-dichloroacetamide increased (P < .05) the molar proportion of propionate only in the 50:50 forage-concentrate diet. Relative to control cultures, monensin and 2,2-dichloroacetamide numerically decreased methane production in the 10 and 100% forage diets and decreased (P < .05) methane in the 50% forage diet. Hydrogen production was unaffected by treatment. Lack of an effect on fermentation end products in the high concentrate diet was probably a result of the low dose levels. In general, increasing levels of 9,10-anthraquinone (.5, 1.0, and 5.0 ppm) reduced total VFA concentration and the molar proportion of acetate, and increased propionate, butyrate and valerate. Increasing levels of 9,10-anthraquinone caused linear and quadratic decreases (P < .05) in methane production, and increases (P < .05) in hydrogen. There were no consistent effects on ammonia concentration in culture fluid from any of the compounds. In continuous culture of a 10:90 forage-concentrate diet, addition of 9,10-anthraquinone (10 ppm of the fluid/12 h) caused changes similar to those observed in batch culture with the exception of a decreased (P < .05) molar percentage of propionate, which may have been due to the high dose. The data are interpreted to indicate that 9,10-anthraquinone has the ability to alter in vitro microbial fermentation.

Acetamides↗

PubMed2003

Alternative approaches to predicting methane emissions from dairy cows.

Previous attempts to apply statistical models, which correlate nutrient intake with methane production, have been of limited value where predictions are obtained for nutrient intakes and diet types outside those used in model construction. Dynamic mechanistic models have proved more suitable for extrapolation, but they remain computationally expensive and are not applied easily in practical situations. The first objective of this research focused on employing conventional techniques to generate statistical models of methane production appropriate to United Kingdom dairy systems. The second objective was to evaluate these models and a model published previously using both United Kingdom and North American data sets. Thirdly, nonlinear models were considered as alternatives to the conventional linear regressions. The United Kingdom calorimetry data used to construct the linear models also were used to develop the three nonlinear alternatives that were all of modified Mitscherlich (monomolecular) form. Of the linear models tested, an equation from the literature proved most reliable across the full range of evaluation data (root mean square prediction error = 21.3%). However, the Mitscherlich models demonstrated the greatest degree of adaptability across diet types and intake level. The most successful model for simulating the independent data was a modified Mitscherlich equation with the steepness parameter set to represent dietary starch-to-ADF ratio (root mean square prediction error = 20.6%). However, when such data were unavailable, simpler Mitscherlich forms relating dry matter or metabolizable energy intake to methane production remained better alternatives relative to their linear counterparts.

Animal Feed↗

PubMed1981

Monensin supplementation and in vivo methane production by steers.

The effect of monensin on methanogenesis was examined. Growing steers were fed 4.1 kg daily of a low roughage diet (12.6% crude protein, 12% acid detergent fiber) or 5.4 kg daily of either a medium roughage (12.3% crude protein, 27% acid detergent fiber) or a high roughage diet (14.4% crude protein, 40% acid detergent fiber) with or without 200 mg of supplemental monensin. At the low and high roughage levels, monensin increased (P less than .05) the molar proportion of ruminal propionate and decreased acetate. Methane production and inhibition by monensin declined with time postprandially. Monensin decreased methane production by 16% (P less than .05) at the two lower roughage levels and 24% (P less than .01) at the high roughage level. Total heat production and respiratory quotient remained unaltered by monensin. Averaged across roughage levels, metabolizable energy was increased (P less than .01) 5.2% by monensin. Although dry matter digestibility and N retention were not statistically altered, both tended to increase with monensin. Reduced ruminal methane production with monensin feeding can explain a portion of the increased feed efficiency.

Animals↗

PubMed1986

Epidemiology of polyps in the rectum and sigmoid colon. Evaluation of breath methane and predisposition for colorectal neoplasia.

The clinical significance of methanogenic bacteria in large-bowel carcinogenesis has not been established so far. As part of a screening study of a randomized population sample of 200 men and 200 women aged 50-59 years, the present breath methane study was designed to gain further information on methane excretion in relation to premalignant colorectal lesions, familial cancer disposition, and dietary fat and fiber. Testing for breath methane excretion did not contribute towards the identification of individuals with premalignant colorectal lesions and therefore should probably not be considered a screening tool.

Adenoma↗

PubMed2003

Effect of sarsaponin on ruminal fermentation with particular reference to methane production in vitro.

This experiment was designed to investigate the effects of different concentrations (0, 1.2, 1.8, 2.4, and 3.2 g/L) of sarsaponin on ruminal microbial methane production using the substrates soluble potato starch, cornstarch, or hay plus concentrate (1.5:1). Ruminal fluid was collected from a dairy cow, mixed with phosphate buffer (1:2) and incubated (30 ml) anaerobically at 38 degrees C for 6 and 24 h with or without sarsaponin. Excluding the lower level of sarsaponin, pH of the medium was slightly decreased. Ammonia-N concentration and numbers of protozoa were decreased in a dose-dependent manner. Total volatile fatty acids and total gas production were increased. Molar proportion of acetate was decreased and propionate was increased with a corresponding decrease in acetate:propionate ratio. Hydrogen production was decreased. As the concentration of sarsaponin increased from 1.2 to 3.2 g/L, fermentation of soluble potato starch, cornstarch, or hay plus concentrate decreased methane production from 20 to 60% (6 h) and 17 to 50% (24 h), 21 to 58% (6 h) and 18 to 52% (24 h), and 23 to 53% (6 h) and 15 to 44% (24 h), respectively. Excluding the lower dose concentration (1.2 g/L) of sarsaponin, in vitro disappearance of dry matter of hay plus concentrate was decreased after 24 h. In conclusion, these results show that sarsaponin stimulated the mixed ruminal microorganism fermentation as well as to inhibit methane production in vitro.

Acetic Acid↗

PubMed1980

Methane production from cattle waste in laboratory reactors at 40 degrees and 60 degrees C after solid-liquid separation.

Whole dairy waste and liquid effluent separated from the same waste with a solid-liquid separator were fermented at mesophilic and thermophilic temperatures. Chemical analyses of the two materials were similar. Methane production was superior in thermophilic reactors. With subtrates adjusted to 4.1% volatile solids, average methane production at 60 degrees C (166 ml/g volatile solids fed to reactors at 3- and 6-day retention time) was as efficient as the 40 degrees C (162 ml/g at 5- and 10-day retention times). Thermophilic reactors produced 1.67 liter methane/liter reactor per day as compared to .93 liter for mesophilic reactors. Efficiency of methanogenesis was no greater for whole waste than for separated effluent. Production of methane for the two substrates averaged over retention times and temperatures was 156 ml/g volatile solids fed to reactor for whole waste and 173 ml/g for separated effluent.

Animals↗

PubMed1976

[Isotopic effect in enzymatic oxidation of methane].

The isotopic effect during oxidation of methane and deuteromethane by a suspension of Methylomonas rubrum cells, for which methane is the only source of carbon, was observed. The rate of CH4 oxidation is 12.5 times higher than that of CH4 oxidation. It is demonstrated that CD4 is a competitive inhibitor of CH4 oxidation. The results obtained suggest that the disruption of the C-H bond is the limiting step of enzymatic oxidation of methane.

Deuterium↗