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Methanogenesis

About: Methanogenesis is a research topic. Over the lifetime, 5064 publications have been published within this topic receiving 244478 citations. The topic is also known as: methane biosynthetic process & methane biosynthesis.


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Journal ArticleDOI
01 Nov 2018
TL;DR: In this article, an alternative biological method was proposed to control the methanogen colony by introducing isolates of denitrifying bacteria to the system which will act as inhibitor to hydrogenotrophic methanogens.
Abstract: The increasingly adverse effects of climate change caused by a variety of fossil-based fuel demands an alternative to such fuel. Hydrogen is one of the potential renewable fuel that offers numerous advantages compared to its competitors. However, the dominant hydrogen production methods are still energy-heavy and dependent on fossil-based resources. Microbial electrolysis cell or MEC system is one of the leading solution towards replacing conventional hydrogen production method. A persistent downside to this system in the presence of methanogens that consumes the hydrogen product. This research proposes alternative biological method to control the methanogen colony by introducing isolates of denitrifying bacteria to the system which will act as inhibitor to hydrogenotrophic methanogen. The reactor implemented is a single-chambered, membrane-less 20-ml reactor. Net hydrogen yield produced in the cathodic headspace will be analyzed by gas chromatography (GC). Hydrogen yield for reactor with enriched cathode is expected to be higher in comparison to unenriched reactor, as nitrogen oxides produced during the metabolism of the denitrifiers were known to inhibit methanogen growth. Experimental results showed consistent higher H 2 yield in inoculated reactor compared to control reactor, where in the second cycle H 2 production increased 100% compared to the control.

2 citations

Dissertation
01 Jan 1997
TL;DR: Results showed that the advantages of a reduced content of readily biodegradable material, achieved by guidance or pretreatment, encompass several aspects of the performance, and that the shift from acidogenic to methanogenic condition is not a discrete one, but rather a continuous transition.
Abstract: Landfilling in "cells" has become more common in recent years. Different waste streams are guided to different cells, among which the biocell is a landfill designed for biogas production. In this thesis, the dependence of biogas generation on waste composition was investigated. Six 8,000 m3 test cells, with contents ranging from mainly commercial waste to pure domestic waste and equipped with gas extraction systems and bottom plastic liners, were monitored for seven years. Great emphasis was given to the characterization of conversion processes and governing mechanism in the topics of bioenergetics, kinetics and capacities. A thermodynamic model, in which the oxidations of volatile fatty acids (VFA) (2< C<7) and hydrogenotrophic methanogenesis were assumed to equilibrate at a certain lower limit for energy conservation (dGmin), explained the relative distribution of VFA's observed in situ. dGmin ranged between -11 to -15 kJ/reaction and decreased with increasing levels of undissociated acetic acid, indicating the reduction of proton gradients over cytoplasmic membranes. Comparisons of methane production rates and internal conditions observed during a two year period, demonstrated that high biogas rates corresponded with low VFA levels. Rates obtained in test cells with mainly commercial waste were 13 - 19 Nm3 CH4/dry tonne,yr, whereas VFA levels ranged between 10 and 24 gO2/l. Corresponding values in domestic waste and food-rich waste fractions were 10 - 14 Nm3 CH4/dry tonne,yr and 18 - 77 gO2/l, respectively. This demonstrates that substrate inhibition of acetotrophic methanogenesis is one of the most important factors governing the rate of biogas generation, a notion supported by the findings from the thermodynamic model, and that the shift from acidogenic to methanogenic condition is not a discrete one, but rather a continuous transition. To explain the discrepancies between theoretical methane potentials and quantified yields (in this study found to be 150-200 and 40-70 Nm3/dry tonne, respectively), the possible nutritional limitation was investigated. Pools and emissions of chemical oxygen demand, N, P and K were quantified. Biomass pools were estimated from methane yields, growth yield coefficients, and bacterial mineral contents. However, results from commercial waste test cells showed that the assimilation of P exceeded the refuse content, which suggests the turnover of microbial biomass and questions the notion of nutritional limitation. In sum, the results showed that the advantages of a reduced content of readily biodegradable material, achieved by guidance or pretreatment, encompass several aspects of the performance. (Less)

2 citations

Posted ContentDOI
TL;DR: In this article, the authors used the humic analog anthraquinone-2, 6-disulfonate (AQDS) to explore the importance of humic substances, and their effects on the temperature sensitivity of anaerobic decomposition in two peatland soils.
Abstract: . Methane (CH4) production is often impeded in many northern peatland soils, although inorganic terminal electron acceptors (TEAs) are usually present in low concentrations in these soils. Recent studies suggest that humic substances in wetland soils can be utilized as organic TEAs for anaerobic respiration and may directly inhibit CH4 production. Here we utilize the humic analog anthraquinone-2, 6-disulfonate (AQDS) to explore the importance of humic substances, and their effects on the temperature sensitivity of anaerobic decomposition, in two peatland soils. In a bog peat, AQDS was not instantly utilized as a TEA, but greatly inhibited the fermentative production of acetate, carbon dioxide (CO2), and hydrogen (H2), as well as CH4 production. When added together with glucose, AQDS was partially reduced after a lag period of 5 to 10 days. In contrast, no inhibitory effect of AQDS on fermentation was found in a fen peat and AQDS was readily reduced as an organic TEA. The addition of glucose and AQDS to both bog and fen peats caused complicated temporal dynamics in the temperature sensitivity of CH4 production, reflecting temporal changes in the temperature responses of other carbon processes with effects on methanogenesis. Our results show that the humic analog AQDS can act both as an inhibitory agent and a TEA in peatland soils. The high concentrations of humic substances in northern peatlands may greatly influence the effect of climate change on soil carbon cycling in these ecosystems.

2 citations

Journal ArticleDOI
09 Mar 2019-Energies
TL;DR: In this article, the feasibility and potential on the reduction of CO2 injected into methane as bioenergy by indigenous microorganisms residing in oilfields in the presence of the fermentative metabolite ethanol were assessed in high-temperature petroleum reservoir production water.
Abstract: Transformation of CO2 in both carbon capture and storage (CCS) to biogenic methane in petroleum reservoirs is an attractive and promising strategy for not only mitigating the greenhouse impact but also facilitating energy recovery in order to meet societal needs for energy. Available sources of petroleum in the reservoirs reduction play an essential role in the biotransformation of CO2 stored in petroleum reservoirs into clean energy methane. Here, the feasibility and potential on the reduction of CO2 injected into methane as bioenergy by indigenous microorganisms residing in oilfields in the presence of the fermentative metabolite ethanol were assessed in high-temperature petroleum reservoir production water. The bio-methane production from CO2 was achieved in enrichment with ethanol as the hydrogen source by syntrophic cooperation between the fermentative bacterium Synergistetes and CO2-reducing Methanothermobacter via interspecies hydrogen transfer based upon analyses of molecular microbiology and stable carbon isotope labeling. The thermodynamic analysis shows that CO2-reducing methanogenesis and the methanogenic metabolism of ethanol are mutually beneficial at a low concentration of injected CO2 but inhibited by the high partial pressure of CO2. Our results offer a potentially valuable opportunity for clean bioenergy recovery from CCS in oilfields.

2 citations

Journal Article
TL;DR: It can be concluded that sunflower oil in mixed microbial culture reduced ciliate protozoal population, ruminal methanogenesis, ammonia nitrogen concentration and improved microbial biomass and propionic acid production.
Abstract: An experiment was conducted to assess the effect of locally available vegetable oils on rumen fermentation characteristics, methanogenesis, enzyme profile and rumen protozoal population in in vitro studies. Four locally available vegetable oils viz., mustard oil, sunflower oil, sesame oil and rice bran oil were incubated at 39±0.5°C for 24 h at four levels viz., 0, 50, 100 and 200 μl in 100 ml glass syringes having 200±5 mg of substrate (paddy straw and concentrate mixture in 1:1 ratio) and 30 ml of incubation medium (mixed rumen microbial culture). Total rumen protozoa as well as isotrichidae and entodiniomorphid population and methane production decreased (P<0.01) due to sunflower oil in the medium. Although, all the vegetable oils did not have any effect on total volatile fatty acid production, propionic acid and microbial biomass production increased (P<0.01) and ammonia nitrogen concentration decreased (P<0.01) due to inclusion of sunflower oil. Inclusion of sunflower oil also improved the activity of carboxymethyl cellulase. However, sunflower oil had no effect on dry matter degradability. Inclusion of sesame oil in the medium at higher dose (200 μl/30 ml incubation medium) decreased (P<0.01) total protozoal number and methanogenesis. Mustard and rice bran oils did not have any effect on ciliate protozoal population, ruminal methanogensis, activity of polysaccharide degrading enzymes, microbial biomass production, ammonia nitrogen concentration and dry matter degradibility in vitro. It can be concluded that sunflower oil in mixed microbial culture reduced ciliate protozoal population, ruminal methanogenesis, ammonia nitrogen concentration and improved microbial biomass and propionic acid production.

2 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023331
2022768
2021367
2020312
2019336
2018267