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PubMed2002

High-rate methane fermentation of lipid-rich food wastes by a high-solids co-digestion process.

This paper presents an experimental study on anaerobic degradation of lipids-rich food wastes by using the high solids co-digestion process. The experiments were conducted under mesophilic (35 degrees C) and thermophilic (55 degrees C) condition, respectively, by using a semi-continuous flow completely mixed reactor. The influent TS level was controlled at around 10%, while the hydraulic retention time (HRT) was changed from 15 days to 7.5 days. The lipids (fats or oil and grease) content in the influent TS was changed from 8% to 40% by adding salad oil (vegetable) and lard (animal) to the food wastes. The result of this study showed that the food wastes containing high lipids content was effectively degraded by the high solids co-digestion process and over 85% of lipid was degraded to biogas with 60-65% of methane. In addition, thermophilic methane fermentation was more effective for reducing lipids and had more higher loading capacity compared with mesophilic condition.

Bacteria, Anaerobic↗
PubMedDate not supplied

[Alternativity of methane assimilation pathways in obligate methylotrophs].

The activity of key enzymes involved in the primary pathways of methane assimilation and enzymes of the citrate cycle was determined in various obligate methylotrophs: mesophilic, thermotolerant, and thermophilic. The bacteria are characterized by the membrane ultrastructure of the I type, high activity of hexosephosphate synthase, NAD- and NADP-specific isocitrate dehydrogenase, and the absence of alpha-ketoglutarate dehydrogenase. The bacteria also displayed the activity of key enzymes of the serine cycle, hydroxypyruvate reductase, and serineglyoxylate aminotransferase. Therefore, both the ribulose monophosphate and serine pathways are involved in methane assimilation, and the division of methanotrophs into two groups, according to their metabolism, is tentative.

Aldehyde-Lyases↗
PubMed2002

[Methane emission from rice paddy soils as influenced by soil physicochemical properties].

To identify the key soil parameters influencing methane emission from rice paddies, and to quantitatively describe the relationship of methane emission with the soil properties, an outdoor pot experiment with a total of 18 paddy soils sampled from different regions in Jiangsu province was conducted in Nanjing Agricultural University during 2000 rice growing season. Seasonal average rate of CH4 emission for all the 18 soils was 6.42 +/- 2.70 mg.(m2.h)-1, ranging from 1.96 to 11.06 mg.(m2.h)-1, approximately a 5.6-fold difference between the maximum and the minimum. Correlation analysis indicated that the seasonal average of CH4 emission was positively dependent on soil sand content (r = 0.528, p = 0.024) and negatively on soil clay content (r = -0.484, p = 0.042). Negative correlation of CH4 emission against soil total nitrogen (r = -0.449, p = 0.062), available nitrogen (r = -0.611, p = 0.007) and NH4(+)-N(r = -0.649, p = 0.004) was also observed. Copper content of soils has a significant negative impact on CH4 emission. The correlation coefficient (r) of CH4 emission against soil available copper and with total copper was -0.594 (p = 0.009) and -0.547 (p = 0.019), respectively. No clear relationship existed between CH4 emission and soil carbon content. A further investigation suggests that the seasonal average rate of CH4 emission can be quantitatively determined by a linear combination of soil available copper, total manganese, and a ratio of available to total iron (R2 = 0.755, p = 0.0001).

Methane↗
PubMedDate not supplied

[Determination of the rate of microbiological oxidation of methane using 14CH4].

The rate of microbiological oxidation of methane was determined by a technique using 12CH4. About 75-96 percent of the carbon form the methane oxidized by microorganisms was found in carbon dioxide, the remaining part was incorporated into the microbial cells. The rate of microbiological mehtane oxidation in the water of the Mari lakes was 6.4 times 10(-3) to 464.4 times 10(-3) cm3 CH4/litre per day.

Bacteria↗
PubMed2003

Sinking methane.

Concentrations of the powerful greenhouse gas, methane, in our atmosphere have doubled since the beginning of the industrial age. Reducing these levels is a vital part of global efforts to combat global warming. Could we make use of the Earth's own methane sinks?

Atmosphere↗
PubMedDate not supplied

[Intensity of bacterial methane formation in ooze deposits in lakes].

The rate of methane production of bacteria via the decomposition of acetate in ooze deposits of the Mari lakes was 0.0165 to 0.483 mg CH4/day/ litre wet ooze. From 32 to 98 per cent of methane in the ooze of studied reservoirs formed through microbiological reduction of carbon dioxide by hydrogen.

Acetates↗
PubMed1992

Hydrogen and methane breath tests for evaluation of resistant carbohydrates.

This review considers in detail the background, principles, techniques, limitations and advantages of the hydrogen and methane breath tests. Resistant food carbohydrates, defined as dietary carbohydrates partly or totally escaping small intestinal assimilation, are fermented in the human colon. This results in production of H2, CH4 and volatile fatty acids. Increased colonic H2 production is a sensitive index of increased carbohydrate fermentation, and a rather constant fraction of the colonic H2 production is excreted by the lungs. It is therefore possible to assess mouth-to-caecum transit times as well as to estimate absorption capacities for several types of resistant carbohydrates by means of H2 breath tests. A prerequisite for correct interpretation is that procedures for determination of H2 concentrations and for breath sampling and storage are carefully validated and standardized. Due to the large interindividual variations of hydrogen excretion, unabsorbable standards should be used. The intraindividual variations of H2 production/excretion and differences in fermentability of different carbohydrate substrates only allow for semiquantitative estimates of malabsorbed amounts of some carbohydrates. Methane breath tests may supplement the information gained from hydrogen measurements, but further evaluations are needed. The hydrogen breath technique is rapid, simple and non-invasive as well as non-radioactive. It may be carried out in a large number of intact individuals under physiological circumstances, and it may be used for studies in children and for field studies. Compared to classical tolerance tests the hydrogen breath test is more sensitive. It is concluded that the hydrogen breath test is a useful tool for investigations of dietary carbohydrates.

Breath Tests↗
PubMed2003

[Effect of iron oxide addition on hydrogen, carbon dioxide and methane geneses in paddy soil].

Paddy soil is an important contributor for atmospheric methane. The methanogenesis is related to the production of acetate, hydrogen and carbon dioxide during the decomposition of organic matter under anaerobic conditions. As electron acceptors, iron (III) oxides can effectively compete with electrons in the transformation of organic matter into methane. Its mechanism maybe relates to the consumption of H2 and CO2. After added ferrihydrite and lepidocrocite, the H2, CO2 and CH4 were determined during the anaerobic incubation of slurries at 25 degrees C for 105 days. The results indicated that the addition of ferrihydrite and lepidocrocite could greatly decrease the concentration of H2, CO2 and CH4, and ferrihydrite had a stronger effect than lepidocrocite. In this system, the balance of organic-C was disturbed, CH4-C and CO2-C were reduced, but the CO3(2-)-C fixed by slurry was greatly increased.

Carbon Dioxide↗
PubMed2003

[Effects of rice plants on methane emission from paddy fields].

Methane emission from rice paddy fields is the net result of the combination of many processes, i.e., CH4 production, CH4 oxidation and CH4 transportation in paddy soil. Rice plants play a key role in the CH4 emission from paddy fields, particularly in all the processes involved. The positive and negative effects of rice plants on CH4 emission from paddy fields are well recognized as the main factors influencing the temporal variation of CH4 emission flux in paddy field. Process-based studies about the effects of rice plants on methane emission from paddy fields were summarized, and different roles of rice plants on this emission were discussed. Root exudates and litters of rice plants could serve as the substrate for methanogenesis and enhance the CH4 production of paddy soils, resulting in a high CH4 emission peak, particularly in rice late growing season. Rhizospheric CH4 oxidation induced by rice root-excreted oxygen constitutes a main biogenic sink of CH4, which could account for 36-90% of CH4 produced in paddy soil over the entire growing season of rice. Up to 80% and more of CH4 released from rice field during a growing season could be emitted by rice plant-mediated transport. The fully developed aerenchyma of rice plants could be of importance in CH4 emission during rice growing seasons, and responsible for the CH4 emission peak observed at rice early growing season.

Methane↗
PubMedDate not supplied

[Forensic and chemical determination of methane in cadaveric samples].

Conditions were elaborated for the determination of methane, through gas chromatography, in blood and the lung by using a 2% methanol solution as an internal standard and with the below gas-chromatography column being applied: dimensions--200 x 0.3 cm, 15% di-2-ethylhexyl sebacate on Dinochrome II (0.16 x 0.21 mm) at 110 0 degree C. The detector is of the flame-ionization type. The normal content of methane was determined for blood and for the lung--0.122 +/- 0.0074 microgram/ml and 0.20 +/- 0.04 microgram/g, respectively. Biological samples from cadavers of other persons who died due to trauma were suggested for use as controls. The method was used to examine expertise objects, blood and the lung from the cadavers of peoples who died in fire.

Cadaver↗
PubMedDate not supplied

Methane oxidation in slurry storage surface crusts.

Livestock manure is a significant source of atmospheric methane (CH4), especially during liquid storage. In liquid manure (slurry) storages a surface crust may form naturally, or an artificial surface crust can be established. We investigated whether there is a potential for CH4 oxidation in this environment. Surface crust materials were sampled from experimental storages with cattle slurry (with natural crust) or anaerobically digested cattle slurry (with straw layer) that had been stored with or without a wooden cover. Extracts of surface crust material were incubated with 5.6% CH4 in the headspace, and methanotrophic activity was demonstrated in all four treatments following a 4- to 10-d lag phase. Subsequent incubation of field-moist surface crust material with 350 microL L(-1) CH4 also showed CH4 oxidation, indicating a potential for CH4 removal under practical storage conditions. There was no CH4 oxidation activity during incubation of autoclaved samples. Methane oxidation rates were 0.1 to 0.5 mg kg(-1) organic matter (OM) h(-1), which is comparable with the activity in wetlands and rice paddies. Partial drying increased CH4 oxidation to 0.2 to 1.4 mg kg(-1) OM h(-1), probably as a result of improved diffusivity within the surface crust. Rewetting reversed the stimulation of methanotrophic activity in some treatments, but not in others, possibly due to a decline in CH4 production in anaerobic volumes, or to growth of methanotrophs during incubation. This study presents direct evidence for methanotrophic activity in slurry storages. Measures to ensure crust formation with or without a solid cover appear to be a cost-effective greenhouse gas mitigation option.

Animals↗
PubMed2005

Anaerobic digestion: impact of future greenhouse gases mitigation policies on methane generation and usage.

The debate as to whether carbon dioxide, methane, nitrous oxide and other greenhouse gas emissions will become subject to increasing regulation, increased restrictions, and probably to some form of carbon tax, has moved from a simple "yes" or "no" to "when". Wastewater treatment plants will be significantly impacted by increased energy costs and by specific regulations and/or penalties associated with emissions of methane and nitrous oxide. In this paper, the greenhouse gases emissions of different wastewater process options are estimated. The paper outlines the increasing need for wastewater treatment plants to factor greenhouse gas mitigation issues into their medium- as and long-term strategies, and identifies anaerobic enhouse as processes as being at the core of such strategies. Further, the paper identifies a number of key research challenges to be addressed if such strategies are to play a larger role in attenuating the likely impacts of GHG mitigation requirements on wastewater treatment plant design and operation.

Air Pollutants↗
PubMed2006

Removal of organic matter and nitrogen from distillery wastewater by a combination of methane fermentation and denitrification/nitrification processes.

The distillery wastewater of Guangdong Jiujiang Distillery, which is characteristic of containing high organic matters and rich total nitrogen, was treated by a combination of methane fermentation and denitrification/nitrification processes. 80% of COD in the raw wastewater was removed by methane fermentation at the COD volumetric loading rate of 20 kg COD/(m3 x d) using the expanded granule sludge bed (EGSB) process. However, almost all the organic nitrogen in the raw wastewater was converted into ammonia by ammonification there. Ammonia and volatile fatty acids (VFA) remaining in the anaerobically treated wastewater were simultaneously removed utilizing VFA as an electron donor by denitrification occurring in the other EGSB reactor and nitrification using PEG-immobilized nitrifying bacteria with recirculation process. An aerobic biological contact oxidization reactor was designed between denitrification/nitrification reactor for further COD removal. With the above treatment system, 18000-28000 mg/L of COD in raw wastewater was reduced to less than 100 mg/L. Also, ammonia in the effluent of the system was not detected and the system had a high removal rate for 900-1200 mg/L of TN in the raw wastewater, only leaving 400 mg/L of nitrate nitrogen.

Ammonia↗
PubMed1989

[Effect of short-time intra-ruminal infusions of linoleic and cis-oleic acids on methane level in the blood of sheep].

Studies were carried out on 7 sheep aged 2-4 years about 40 kg in body weight successively in summer and autumn. The animals were fed in 6 feeding groups. The samples of arterial and venous blood and control air also were taken 4 hrs after morning feeding. During feeding sheep were given in a short intraruminal 1-hr infusions unsaturated fatty acids: linoleic and cis-oleic. The methane levels in arterial and venous blood were both higher in summer than in autumn. The contents of CH4 in each of the diets were higher in venous blood than in arterial blood. The highest inhibition of methane production was observed in blood of experimental sheep which were fed on a bulky feed.

Animals↗
PubMedDate not supplied

[Characteristics of the methane fermentation of waste of animal husbandry complexes with respect to the biomass of microorganisms and volatile fatty acids].

The content of microbial biomass and the concentration of volatile fatty acids were comparatively studied in the tanks where the waste products of three stock farms were subjected to methane fermentation. The biomass content was shown to vary from 19 to 30% of the dry matter weight and the concentration of volatile fatty acids from 0 to 4.5 g per litre. The low concentrations of acetic and propionic acids together with the high biomass content were indicative of an active balanced microbial association. The parameters can be used to assess the operation of methane fermentation tanks.

Animal Husbandry↗
PubMed1988

[Changes in the function of the cardiovascular system and cerebral circulation in patients poisoned by carbon monoxide and methane].

Altogether 68 patients with carboxyhemoglobinemia and 58 patients poisoned with methane were investigated. Toxic encephalopathy was observed in all of them: I degree of severity--in 13 patients, II degree in 29, III degree in 24, and IV degree in 60. To control CVS function, indices of central hemodynamics were investigated using methods of whole-body rheography and ECG; a volumetric rate of cerebral circulation was determined. A decrease in volumetric cerebral circulation was noted in patients with encephalopathy, III-IV degree, by 37.5% (carboxyhemoglobinemia) and by 26.1% (methane poisoning). Central hemodynamic disorders were more noticeable in carboxyhemoglobinemia. Multimodality intensive therapy included HBO and drugs to restore cerebral circulation, microcirculation in the brain, cerebral metabolism, and CVS function. Of 126 patients CNS functional restoration without neurological deficiencies was noted in 108 patients, neurological and psychic deficiencies were noted in 9 patients; 9 patients died.

Adult↗
PubMedDate not supplied

[Refinement of the diagnosis of the genera and species of methane-using bacteria].

The diagnoses of taxons have been corrected for methane assimilating bacteria of the family Methylomonadaceae Leadbetter 1974, of the genera Methylomonas Leadbetter 1974. Methylococcus Foster a. Davis 1966, Methylosinus Whittenbury. Phillips a. Wilkinson 1970, Methylocytis Whittenbury, Phillips a. Wilkinson 1970, and of 16 species. The diagnosis of the species Methylomonas rubra Whittenbury, Phillips a. Wilkinson 1970 has been completed, and the new species Methylomonas gracilis sp. nov. and Methylococcus luteus sp. nov. have been described. Since information about the properties of certain strains is not complete, they should be transferred to the category incertae sedis. Diagnostic keys for identification of methane assimilating bacteria are presented in the paper.

Methane↗
PubMed1977

[Prevention of methane emission by pre-tele-injection of water into the layer].

This paper describes trials of pre-tele-infusion carried out at Zolder mine, of the Kempense Steenkolenmijnen, as part of a research project on the control of methane emission. An increase in output of more than 25% (accompanied by a reduction in dust concentration) with no significant increase in total methane emission is reported. Furthermore, a reduction in total emission of between 13 and 22% was observed when an infused panel was worked above a coal seam which had also been infused.

Accidents, Occupational↗