Showing papers on "Methane published in 1978"

Light hydrocarbons in recent Texas continental shelf and slope sediments

Abstract: The distributions of the concentrations of methane, ethene, ethane, propene, and propane in twelve l-to 2-m-long gravity cores for two transects from nearshore to midslope off the southwest Texas Gulf Coast are reported. Methane profiles exhibit maxima in the top 40 cm of sediment on the shelf, in contrast to downward increasing gradients in the slope region. Nearshore surface methane concentrations ranging from 50 to 400 tl (normal temperature and pressure) per liter pore water are apparently due to microbial production ijsulfate-free microenvironments such as fecal pellets in a near-seawater sulfate environment. A decrease in sediment methane levels to less than 5 tl/l pore water in downslope sediments is attributed to reduced microbial activity due to lower organic contents and temperatures. Profiles of the saturated and unsaturated C: and Ca hydrocarbons suggest that these gases are also microbia!ly produced. plastic liner, was removed from the core barrel and sectioned at specific depths. Five-centimeter sections were immediately extruded into 0.5-1 containers holding 125 ml of sodium-azide- poisoned hydrocarbon-free seawater. The containers were capped, and the headspaces flushed with helium or nitrogen through septa in the lids. The hydrocarbon gases dissolved in the interstitial water were equilibrated with the gas phase by agitation for 5 min with a high-speed shaker. The shaker also dispersed the sodium azide throughout the sediment to inhibit microbial activity. The headspace gases were then analyzed, or the containers were inverted to form liquid seals around the lids and stored in darkness at near-freezing temperatures until analysis.

Methane cycling in a eutrophic shield lake and its effects on whole lake metabolism 1

Abstract: The methane cycle of an artificially eutrophic shield lake is considered by relating in situ rates of production to rates of oxidation and evasion. Methane production rates f’or oxygenated and anoxic sediments were quite consistant throughout the year, ranging from ~1.0 to ~10 mmol m−2 sediment d−1. Methane oxidation rates were highly variable (0.02–32 mmol m−2 lake surface d−1) as were evasion rates (0.0–60 mmol m−2 lake surface d−1). Oxidation and evasion rates both peaked during fall overturn and were very low during the remainder of the year. Methane production was important in regenerating carbon from sediments. Fifty-five percent of total carbon input was regenerated as methane during 1 year and 36% of this total carbon input was recycled by methane oxidation. Methane oxidation was not an important source of carbon dioxide for primary producers or of seston for secondary grazers during the summer. During some winters production of particulate carbon by methane oxidizers may have been an important source of seston for grazers. Methane oxidation was the most important contributor to the development of total lake anoxia under ice cover.

Process for in situ coal gasification

Abstract: In situ coal gasification to form a methane rich gas is carried out by injecting a lower aliphatic alcohol such as methanol into a coal seam, raising the temperature to cause dissociation of the alcohol and injecting water into the same. Nascent hydrogen is produced which reacts with the coal to form methane. The product gas may also contain hydrogen and carbon monoxide which can be separated and reacted to form methanol.

Kinetics of methane fermentation

Abstract: The kinetics on methane fermentation are described using published data for livestock residue, sewage sludge, and municipal refuse. Methods are presented to determine the kinetic constants and the finally attainable methane production using steady-state methane production data. The effects of temperature, loading rate, and influent substrate concentration on methane fermentation kinetics are discussed. These relationships were used to predict the rate of methane production of a pilot-scale fermentor with excellent results.

Methanogenesis, fires and the regulation of atmospheric oxygen

Abstract: The Gaia hypothesis states that the composition, oxidation-reduction potential and the temperature of the Earth's lower atmosphere are modulated by and for the biota living on the surface (Lovelock, 1972; Margulis and Lovelock, 1974). A corollary is that atmospheric oxygen is presently regulated at about 21% for the dominant life forms today: vascular plants and metazoa. We suggest that the enormous annual production of methane (of the order of 10 14 mol) is directly related to the short term modulation of oxygen concentration. Atmospheric oxygen results from the burial of reduced carbon; methanogenesis and subsequent atmospheric oxidation of methane prevents that burial. We also present experimental work on the probability of ignition of vegetation as a function of increasing oxygen concentration (Watson, 1978). Both the experiments and consideration of the fossil record lead us to conclude that oxygen has been regulated by methane (and perhaps by N 2 O and others) at about 10–25% for very long periods relative to the atmospheric residence times of these reactive gases.

Liquid-vapor equilibriums at 270.00 K for systems containing nitrogen, methane, and carbon dioxide

Abstract: To provide data needed for the low-temperature, high-pressure processing of natural gas, the Colorado School of Mines measured liquid-vapor equilibria for the binary systems nitrogen-carbon dioxide and methane-carbon dioxide and for the ternary system nitrogen-methane-carbon dioxide at 270.00/sup 0/ K and pressures of 23-122 atm. The equations of state chosen for study were the modified Redlich-Kwong equations and the modified van der Waals equation proposed by Peng and Robinson. The Peng-Robinson relation most closely represented the experimental data for two binary systems; predictions of the ternary system, however, proved unsatisfactory in all regions near the critical point.

Adsorption rate on molecular sieving carbon by chromatography

Abstract: Diffusivities in the micropore and adsorption equilibrium constants were determined for neon, argon, krypton, xenon, nitrogen, methane, ethylene, ethane, propylene, propane, n-butane, and benzene on molecular sieving carbon by chromatographic measurement and moment analysis. Isosteric heat of adsorption was found to be 2.6 times heat of vaporization for the gases examined here. Two separate linear relations were obtained between activation energies of diffusion in micropore and isosteric heats of adsorption for rare gases, methane, and benzene, and for n-paraffin and n-olefin except methane.

Consumption of dissolved methane in the deep ocean 1

Abstract: Oceanic dissolved methane concentrations are normally in excess of atmospheric equilibrium values in surface waters but show a rapid decrease with depth. Deep North Atlantic waters have only ca. 30% of their atmospheric equilibrium values of methane and deep North Pacific waters have only ca. 10%. Methane consumption rates calculated from methane analyses and water mass ages derived from published data on SII/3He ages, r4C ages, and model calculations show that both methane and oxygen are rapidly consumed in “young” water but, while oxygen consumption continues at a low rate throughout the deep ocean, methane consumption virtually ceases within about 100 years of isolation from the surface ocean.

Production of methane and carbon dioxode from methane thiol and dimethyl sulphide by anaerobic lake sediments

Abstract: METHANE THIOL (methyl mercaptan, MeSH), its oxidation product, dimethyl disulphide (DMDS), and dimethyl sulphide (DMS) are naturally occurring metabolites. They are also produced by paper mills using the kraft pulp process1 and cause an industrial odour problem because of their low odour threshold. Although the biological production of these compounds is fairly well understood2, little is known about their biological decomposition. We report here that microbial populations present in anaerobic freshwater sediments and in anaerobic sewage digestor sludge are capable of metabolising the carbon in these volatile organic sulphur compounds to methane and carbon dioxide. Therefore, anaerobic habitats may serve as sinks in the biogeochemical cycling of these compounds.

Kinetic parameters of the conversion of methane precursors to methane in a hypereutrophic lake sediment.

Abstract: The kinetic parameters K(m), V(max), T(t) (turnover time), and v (natural velocity) were determined for H(2) and acetate conversion to methane by Wintergreen Lake sediment, using short-term (a few hours) methods and incubation temperatures of 10 to 14 degrees C. Estimates of the Michaelis-Menten constant, K(m), for both the consumption of hydrogen and the conversion of hydrogen to methane by sediment microflora averaged about 0.024 mumol g of dry sediment. The maximal velocity, V(max), averaged 4.8 mumol of H(2) g h for hydrogen consumption and 0.64 mumol of CH(4) g h for the conversion of hydrogen to methane during the winter. Estimated natural rates of hydrogen consumption and hydrogen conversion to methane could be calculated from the Michaelis-Menten equation and estimates of K(m), V(max), and the in situ dissolved-hydrogen concentration. These results indicate that methane may not be the only fate of hydrogen in the sediment. Among several potential hydrogen donors tested, only formate stimulated the rate of sediment methanogenesis. Formate conversion to methane was so rapid that an accurate estimate of kinetic parameters was not possible. Kinetic experiments using [2-C]acetate and sediments collected in the summer indicated that acetate was being converted to methane at or near the maximal rate. A minimum natural rate of acetate conversion to methane was estimated to be about 110 nmol of CH(4) g h, which was 66% of the V(max) (163 nmol of CH(4) g h). A 15-min preincubation of sediment with 5.0 x 10 atm of hydrogen had a pronounced effect on the kinetic parameters for the conversion of acetate to methane. The acetate pool size, expressed as the term K(m) + S(n) (S(n) is in situ substrate concentration), decreased by 37% and T(t) decreased by 43%. The V(max) remained relatively constant. A preincubation with hydrogen also caused a 37% decrease in the amount of labeled carbon dioxide produced from the metabolism of [U-C]valine by sediment heterotrophs.

Methane, carbon dioxide, and hydrogen sulfide production from the terminal methiol group of methionine by anaerobic lake sediments.

Abstract: A significant portion of the sulfide in lake sediments may be derived from sulfur-containing amino acids. Methionine degradation in Lake Mendota (Wisconsin) sediments was studied with gas chromatographic and radiotracer techniques. Temperature optimum and inhibitor studies showed that this process was biological. Methane thiol and dimethyl sulfide were produced in sediments when 1-μmol/ml unlabeled methionine was added. When chloroform (an inhibitor of one-carbon metabolism) was added to the sediments, methane thiol, carbon disulfide, and n-propane thiol were produced, even when no methionine was added. When 35S-labeled methionine was added to the sediments in tracer quantities (1.75 nmol/ml), labeled hydrogen sulfide was produced, and a roughly equal amount of label was incorporated into insoluble material. Methane and carbon dioxide were produced from [methyl-14C]methionine. Evidence is given favoring methane thiol as an intermediate in the formation of methane, carbon dioxide, and hydrogen sulfide from the terminal methiol group of methionine. Methionine may be an important source of sulfide in lake sediments.

Changes in proportions of acetate and carbon dioxide used as methane precursors during the anaerobic digestion of bovine waste

Abstract: In an anaerobic digestor which was fed daily with bovine waste, during the early stages after feeding (4 to 7 h) acetate (via the methyl group) accounted for almost 90% of the methane produced. As time after feeding increased, acetate declined as a precursor so that in the 12- to 14-h and 21- to 23-h periods, after feeding the methyl group accounted for 80 and 73% of the methane produced, respectively. Measurements of methane production from CO2 reduction showed that in the 2- to 12-h period after feeding, CO2 accounted for 14% of the methane produced, whereas in the 12- to 24-h period it accounted for 27-5%. These results show that the percentages of methane accounted for by acetate and CO2 vary with time after feeding the digestor.

Speculations on the budget of particulate and vapor phase non-methane organic carbon in the global troposphere

Abstract: Perhaps less is known about the global source, distribution, and fluxes of non-methane organic matter than any other major class of chemical substances in the atmosphere. Source strength estimates and consideration of the available concentration data suggest that the quantity of organic carbon on large particles (d>1 μm) in the global troposphere can be explained by primary emissions from anthropogenic sources and such natural sources as the ocean, crustal weathering, and forest wildfires. However, these pollution and natural sources apparently cannot account for the global tropospheric burden of small particle (d<1 μm) organic carbon. Approximately 80–160 MT/yr of small particle carbon from some additional source is required to balance this cycle. Possibilities include direct production from the leaves of vegetation and gas to particle conversion of natural and anthropogenic organic carbon compounds. The estimated production of reactive vapor phase organic compounds from natural and pollution sources is sufficient to account for the mass of this additional small particle organic carbon. However, considerably more data is required on the global distribution, source strengths, reaction pathways and rates, and removal mechanisms before an accurate description of the non-methane organic carbon cycle can be made.

In situ methane production in a small, hypereutrophic, hard‐water lake: Loss of methane from sediments by vertical diffusion and ebullition 1

Abstract: The rate and quantity of methane produced by sediments of Wintergreen Lake were estimated by separately measuring methane lost by ebullition using bubble traps and by estimating methane lost to the water column by diffusion. The maximum rates of methane loss by ebullition occurred in late summer and were 35 mmol. rnw2. d-i in 1972 and 37 in 1973. The average dissolved methane flux for 1972 was estimated to be in the range of lo-46 mmol. rnw2. d-l. The minimum value was estimated by summing dissolved methane concentrations in the water column for each sampling date. The maximum value was estimated using the eddy diffusion coefficient of 4.9 x 10e3 cm2-s-l, calculated from the temperature method of Hutchinson. This methane diffusion rate was about two times the average rate of methane lost by ebullition (21 mmol*m-2*d-1) over the same time period. Dissolved methane was detected only in anoxic waters during summer stratification and within a meter of both the sediment and ice during winter. Ebullition also occurred during winter.

Gas Production from Solid Waste in Landfills

Abstract: The rate and composition of gases released during anaerobic degradation of solid waste were measured. From 55 kg to 80.5 kg of solid waste was placed in 208-l containers, sealed, and maintained at different environmental conditions, and the gas production and composition were measured. The major gases observed in the present study were CO\d2, H\d2 and CH\d4. The maximum rate of gas production was 0.18 l/kg.day while the maximum amount of gas produced was 5.7 l/kg.day dry weight during the 300-day testing period. The rate of gas production generally increased with increasing moisture content and temperature and with decreasing solid waste size and density.

Biomethanation: Anaerobic fermentation of CO2, H2 and CO to methane

Abstract: Studies to examine the microbial fermentation of coal gasification products (CO2, H2 and CO) to methane have been done with a mixed culture of anaerobic bacteria selected from an anaerobic sewage digestor. The specific rate of methane production at 37°C reached 25 mmol/g cell hr. The stoichiometry for methane production was 4 mmol H2/mol CO2. Cell recycle was used to increase the cell concentration from 2.5 to 8.3 g/liter; the volumetric rate of methane production ran from 1.3 to 4 liter/liter hr. The biogasification was also examined at elevated pressure (450 psi) and temperature to facilitate interfacing with a coal gasifier. At 60°C, the specific rate of methane production reached 50 mmol/g cell hr. Carbon monoxide utilization by the mixed culture of anaerobes and by a Rhodopseudomonas species was examined. Both cultures are able to carry out the shift conversion of CO and water to CO2 and hydrogen.

Physical Adsorption of Gases at High Pressures: Argon and Methane onto Graphitized Carbon Black

Abstract: A gravimetric method for the determination of surface excess isotherms of compressed gases on solid adsorbents is described. Buoyancy corrections are minimized by using a symmetric-beam microbalance and by compensating the volume of the adsorbent. — Isotherms of argon and methane onto Graphon (a graphitized carbon black) are determined up to 150 bar at −20, 0, 25, and 50°C, corresponding to bulk densities up to the critical density for methane, and more than half the critical density for argon. Surface excess isotherms exhibit a maximum at about 0.4 to 0.5 of the critical density. The range of applicability of simple isotherm equations for higher gas pressures is discussed briefly.

Combined pressure and diffusional transition region flow of gases in porous media

Abstract: Expressions were derived for combined pressure and diffusional transition region flow of gases in porous media. Experimental systems were developed to verify the applicability of the equations for packed columns of Kaolinite clay and quartz sand with methane and carbon dioxide flowing into nitrogen.

Selectivity of semiconductor gas sensors

Abstract: It is shown that Taguchi Gas sensors Types 812 and 813 exhibit a marked degree of selectivity to carbon monoxide and methane, and curves of their performance in mixtures of these gases are presented.

System for combustion of gases of low heating value

Abstract: A gas turbine system for the recovery of power from fuel gases having a low heating value, i.e., below about 80 Btu/scf, and usually in the range of 35 to 70 Btu/scf, has an external catalytic combustor. The catalytic combustor is divided into a primary and a secondary catalytic combustion chamber with a heat exchanger between the two combustion chambers. In the preheater the low heating value gas mixed with combustion air is passed in indirect heat exchange with products of combustion from the first combustion chamber before the low heating value gas is delivered to the first combustion chamber. The turbine system is particularly advantageous in recovering power from low heating value gas in which the combustibles are hydrocarbons, primarily methane.

Thermophilic methanogenesis in a hot-spring algal-bacterial mat (71 to 30 degrees C).

Abstract: Algal-bacterial mats which grow in the effluent channels of alkaline hot springs provided an environment suitable for studying natural thermophilic methane producing bacteria. Methane was rapidly produced in cores taken from the meat and appeared to be an end product of decomposition of the algal-bacterial organic matter. Formaldehyde prevented production of methane. Initial methanogenic rate was lower and methanogenesis became exponential when samples were permitted to cool before laboratory incubation. Methanogenesis occurred and methanogenic bacteria were present over a range of 68 to 30 degrees C, with optimum methanogenesis near 45 degrees C. The temperature distribution of methanogenesis in the mat is discussed relative to published results on standing crop, primary production, and decomposition in the thermal gradient. The depth distribution of methanogenesis was similar to that of freshwater sediments, with a zone of intense methanogenesis near the mat surface. Methanogenesis in deeper mat layers was very low or undetectable despite large numbers of viable methanogenic bacteria and could not be stimulated by addition of anoxic source water, sulfide, or a macronutrient solution.