scholarly journals Petrological factors controlling abiotic methane formation in mafic-ultramafic rocks

2020 ◽  
Author(s):  
Ελένη Υφαντή
Keyword(s):  
Ultramafic Rocks ◽  
Methane Formation ◽  
Abiotic Methane

Η ύπαρξη αβιοτικού μεθανίου σε υπερβασικά πετρώματα ως προϊόν υδρογόνωσης του CO2, είναι ένα αναδυόμενο ερευνητικό θέμα. Θεωρείται, ότι μέταλλα που απαντώνται σε ορυκτές φάσεις ορισμένων υπερμαφικών πετρωμάτων, καταλύουν την αντίδραση Sabatier. Ωστόσο, δεν είναι ακόμη σαφές ποια ορυκτολογικά χαρακτηριστικά ή/και πετρολογικοί παράγοντες ελέγχουν το σχηματισμό του μεθανίου και ποιος λιθότυπος είναι η πηγή του. Η εμφάνιση και η ισοτοπική σύνθεση του αερίου που περιέχεται στα πετρώματα, ποσοτικοποιείται μέσω γεωχημικών αναλύσεων αερίου, έπειτα από την κονιοποίηση πετρωμάτων. Ο σκοπός αυτής της μελέτης είναι να δώσει νέες πληροφορίες για τα κενά της βιβλιογραφίας που αναφέρονται παραπάνω. Ο στόχος ήταν να εντοπιστούν οι ορυκτολογικές αντιδράσεις που υποδηλώνουν το σχηματισμό μεθανίου και να εντοπιστούν οι πιθανοί ορυκτοί-καταλύτες που δείχνουν παρελθούσα ή σύχρονη αντίδραση μεταξύ αερίου-πετρώματος. Η εις βάθος κατανόηση των πετρολογικών παραγόντων που ελέγχουν το σχηματισμό αβιοτικού μεθανίου κατά τη διάρκεια της ηπειρωτικής σερπεντινίωσης, αναμένεται να επιτρέψει την εξαγωγή ερευνητικών κριτηρίων που θα μπορούσαν να χρησιμοποιηθούν σε επικείμενες έρευνες για την ύπαρξη αβιοτικού μεθανίου, σε μη μελετημένες περιοχές. Αυτή η μελέτη πραγματοποιήθηκε σε δύο μέρη. Το πρώτο μέρος της διατριβής, επικεντρώθηκε στον προσδιορισμό των λιθολογιών που φιλοξενούν αβιοτικό μεθάνιο, μεταξύ δειγμάτων που προέρχονται από διαφορετικά οφιολιθικά συμπλεγματα καθώς και δειγμάτων μη οφιολιθικών βασαλτών στην Ελλάδα. Τα αποτελέσματα χρησιμοποιήθηκαν για τη διερεύνηση των ορυκτολογικών παραγόντων που επηρεάζουν το σχηματισμό του αβιοτικού μεθανίου και για την εξαγωγή ερευνητικών κριτηρίων για διερεύνηση μεθανίου σε μη μελετημένες περιοχές. Στο δεύτερο μέρος, οι ορυκτολογικοί και γεωχημικοί δείκτες της ύπαρξης αβιοτικού αερίου που τέθηκαν στο πρώτο μέρος, δοκιμάστηκαν για την καταλληλότητά τους να εκτιμήσουν την πιθανότητα ενός οφιολιθικού συμπλέγματος να φιλοξενεί αβιοτικό μεθάνιο. Για το σκοπό αυτό, επιλέχθηκαν οι Περιδοτιτες του Ranau, στη Sabah, ανατολική Μαλαισία. Τα αποτελέσματα αυτής της μελέτης έδειξαν ότι οι χρωμιτίτες από την Μοσχοκαρυά και τις Αετορράχες, φιλοξενούν την υψηλότερη ποσότητα μεθανίου. Επιπλέον, οι χρωμιτίτες από τη Μοσχοκαρυά είναι εμπλουτίσμένοι σε IPGE, με κύριες ορυκτές φάσεις τον λωρίτη και τα IPGE-Ni θειούχα ορυκτά. Τα δευτερεύοντα κράματα IPGE στους χρωμίτες της Μοσχοκαρυάς, μοιάζουν ιστολογικά με αποδομημένους καταλύτες που προκείπτουν έπειτα από εκτεταμένες αντιδράσεις αερίου-πετρώματος με ρευστή φάση. Επιπλέον, τέθηκαν τέσσερις κύριες κατηγορίες κριτηρίων έρευνας για να βοηθήσουν τη μελλοντική διερεύνηση του αβιοτικού μεθανίου σε νέες περιοχές (υπαιθριες ενδείξεις, λιθολογίες να αντιδράσουν, λιθολογία σχηματισμού του αβιοτικού μεθανίου, δείκτες ύπαρξης καταλύτη). Αυτά τα κριτήρια, χρησιμοποιήθηκαν για τη διερεύνηση της πιθανότητας εμφάνισης αβιοτικού μεθανίου σε μια μη μελετημένηπεριοχή (Περιδοτιτες του Ranau). Τα πρώτα αποτελέσματα έδειξαν ότι οι Περιδοτίτες του Ranau φιλοξενούν μεθάνιο με πιθανή αβιοτική προέλευση. Συνοπτικά, αυτή η έρευνα έδειξε ότι οι συμπαγείς χρωμιτίτες είναι οι λιθολογίες που φέρουν τον καταλύτη και φιλοξενούν την υψηλότερη ποσότητα αβιοτικού μεθανίου. Συνεπώς θεωρούνται ως η λιθολογία σχηματισμου του αβιοτικού μεθανίου. Τα Ru-PGM είναι οι δυνητικοί καταλύτες της αντίδρασης Sabatier, ενώ η εξαλλοίωση των PGM σε αναγωγικές συνθήκες, μοιάζει με έναν αποδομημένο καταλύτη, έπειτα από εκτεταμένες αντιδράσεις αερίου-βράχου με τη ρευστή φάση.

High-pressure serpentinization and abiotic methane formation in metaperidotite from the Appalachian subduction, northern Vermont

Lithos ◽  
2021 ◽  
pp. 106190
Author(s):  
Antoine Boutier ◽  
Alberto Vitale Brovarone ◽  
Isabelle Martinez ◽  
Olivier Sissmann ◽  
Sara Mana
Keyword(s):  
High Pressure ◽  
Methane Formation ◽  
Abiotic Methane

scholarly journals Abiotic methane formation during experimental serpentinization of olivine

2016 ◽  
Vol 113 (49) ◽  
pp. 13965-13970 ◽  
Author(s):  
Thomas M. McCollom
Keyword(s):  
Laboratory Experiments ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Methane Formation ◽  
Natural Systems ◽  
Abiotic Synthesis ◽  
Inorganic Carbon Source ◽  
Abiotic Reduction ◽  
Abiotic Methane ◽  
Kinetic Barriers

Fluids circulating through actively serpentinizing systems are often highly enriched in methane (CH4). In many cases, the CH4 in these fluids is thought to derive from abiotic reduction of inorganic carbon, but the conditions under which this process can occur in natural systems remain unclear. In recent years, several studies have reported abiotic formation of CH4 during experimental serpentinization of olivine at temperatures at or below 200 °C. However, these results seem to contradict studies conducted at higher temperatures (300 °C to 400 °C), where substantial kinetic barriers to CH4 synthesis have been observed. Here, the potential for abiotic formation of CH4 from dissolved inorganic carbon during olivine serpentinization is reevaluated in a series of laboratory experiments conducted at 200 °C to 320 °C. A 13C-labeled inorganic carbon source was used to unambiguously determine the origin of CH4 generated in the experiments. Consistent with previous high-temperature studies, the results indicate that abiotic formation of CH4 from reduction of dissolved inorganic carbon during the experiments is extremely limited, with nearly all of the observed CH4 derived from background sources. The results indicate that the potential for abiotic synthesis of CH4 in low-temperature serpentinizing environments may be much more limited than some recent studies have suggested. However, more extensive production of CH4 was observed in one experiment performed under conditions that allowed an H2-rich vapor phase to form, suggesting that shallow serpentinization environments where a separate gas phase is present may be more favorable for abiotic synthesis of CH4.

scholarly journals First Detection of Methane within Chromitites of an Archean-Paleoproterozoic Greenstone Belt in Brazil

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 256
Author(s):  
Yuri de Melo Portella ◽  
Federica Zaccarini ◽  
Giuseppe Etiope
Keyword(s):  
Greenstone Belt ◽  
Isotope Composition ◽  
Co2 Hydrogenation ◽  
Ultramafic Rocks ◽  
Gas Extraction ◽  
Methane Generation ◽  
Upper Limit ◽  
Similar Temperature ◽  
First Time ◽  
Abiotic Methane

Abiotic methane is widely documented in seeps, springs and aquifers associated with mafic-ultramafic rocks in Phanerozoic ophiolites, peridotite massifs and intrusions worldwide. Chromitites in ophiolites, in particular, have been interpreted as the rocks potentially generating methane though CO2 hydrogenation. Here, we document, for the first time, the presence of methane within chromitites in South America. We analyzed, through milling and gas extraction, the content of gas occluded in Cedrolina chromitite samples, belonging to the Pilar de Goiás greenstone belt in Brazil. The chromitites display significant gas concentrations up to 0.31 µg CH4/grock and 2800 ppmv of hydrogen, while the host talc schist is devoid of gas. Stable C isotope composition of methane (δ13C from −30 to −39.2‰) and the absence of organic-matter rich metasediments in the region suggest an abiotic origin. Hydrogen and methane concentrations appear related to high-Cr chromite modal content and to the presence of Ni-sulfides/alloys, which are potential catalysts of CO2 hydrogenation at temperatures above 200 °C. Accessory ruthenium-bearing minerals occurring in the chromitites could also act as catalysts, even at lower temperatures. Geothermometry of chlorite found in the chromitites constrains serpentinization at ~250 °C, during lower greenschist facies retrometamorphism. Hydrogen could be autochthonous, and thus formed under similar temperature, which we hypothesize represents the upper limit for abiotic methane generation in the area (250 °C). The Cedrolina chromitites are the first example of CH4 occurrence in ultramafic rocks related to an Archean-Paleoproterozoic greenstone belt. This may imply that serpentinized Cr-rich chromitites could have been sources of methane for the early Earth’s atmosphere.

BIOGAS PRODUCTION IN THE CONCENTRATED DISTILLERY WASTEWATER TREATMENT

2018 ◽  
pp. 51-59 ◽  
Author(s):  
N. Golub ◽  
M. Potapova ◽  
M. Shinkarchuk ◽  
O. Kozlovets
Keyword(s):  
Wastewater Treatment ◽  
Dry Matter ◽  
Ph Value ◽  
Biogas Production ◽  
Anaerobic Sludge ◽  
Methane Formation ◽  
Maximum Output ◽  
Processing Technologies ◽  
Spent Wash ◽  
Distillery Spent Wash

The paper deals with the waste disposal problem of the alcohol industry caused by the widespread use of alcohol as biofuels. In the technology for the production of alcohol from cereal crops, a distillery spent wash (DSW) is formed (per 1 dm3 of alcohol – 10–20 dm3 DSW), which refers to highly concentrated wastewater, the COD value reaches 40 g O2/dm3. Since the existing physical and chemical methods of its processing are not cost-effective, the researchers develop the processing technologies for its utilization, for example, an anaerobic digestion. Apart from the purification of highly concentrated wastewater, the advantage of this method is the production of biogas and highquality fertilizer. The problems of biotechnology for biogas production from the distillery spent wash are its high acidity–pH 3.7–5.0 (the optimum pH value for the methanogenesis process is 6.8–7.4) and low nitrogen content, the lack of which inhibits the development of the association of microorganisms. In order to solve these problems, additional raw materials of various origins (chemical compounds, spent anaerobic sludge, waste from livestock farms, etc.) are used. The purpose of this work is to determine the appropriate ratio of the fermentable mixture components: cosubstrate, distillery spent wash and wastewater of the plant for co-fermentation to produce an energy carrier (biogas) and effective wastewater treatment of the distillery. In order to ensure the optimal pH for methanogenesis, poultry manure has been used as a co-substrate. The co-fermentation process of DSW with manure has been carried out at dry matter ratios of 1:1, 1:3, 1:5, 1:7 respectively. It is found that when the concentration of manure in the mixture is insufficient (DSW/manure – 1:1, 1:3), the pH value decreases during fermentation which negatively affects methane formation; when the concentration of manure in the mixture is increased (DSW/manure – 1:5, 1:7), the process is characterized by a high yield of biogas and methane content. The maximum output of biogas with a methane concentration of 70 ± 2% is observed at the ratio of components on a dry matter “wastewater: DSW: manure” – 0,2:1:7 respectively. The COD reduction reaches a 70% when using co-fermentation with the combination of components “wastewater: DSW: manure” (0,3:1:5) respectively.

DISTRIBUTION OF DISSOLVED METHANE IN SURFACE COASTAL WATERS OF THE NORTHEASTERN PART OF THE BLACK SEA

2017 ◽  
Author(s):  
Elena Kovaleva ◽  
Elena Kovaleva ◽  
Alexander Izhitskiy ◽  
Alexander Izhitskiy ◽  
Alexander Egorov ◽  
...  
Keyword(s):  
Black Sea ◽  
Natural Waters ◽  
Sea Water ◽  
The Black Sea ◽  
Methane Formation ◽  
Anthropogenic Pressure ◽  
Russian Science ◽  
Southeastern Part ◽  
Dissolved Methane ◽  
Continental Runoff

Studying of methane formation and distribution in natural waters is important for understanding of biogeochemical processes of carbon cycle, searching for oil and gas sections and evaluation of CH4 emissions for investigations of greenhouse effect. The Black Sea is the largest methane water body on our planet. However, relatively low values of methane concentration (closed to equilibrium with the atmospheric air) are typical of the upper aerobic layer. At the same time, the distribution pattern of CH4 in surface waters of coastal areas is complicated by the influence of coastal biological productivity, continental runoff, bottom sources, hydrodynamic processes and anthropogenic effect. The investigation is focused on the spatial variability of dissolved methane in the surface layer of the sea in coastal regions affected by the continental runoff and anthropogenic pressure. Unique in situ data on methane concentrations were collected along the ship track on 2 sections between Sochi and Gelendzhik (2013, 2014) and 2 sections between Gelendzhik and Feodosia (2015). Overall 170 samples were obtained. Gas-chromatographic analysis of the samples revealed increase of CH4 saturation in the southeastern part of the Crimean shelf and the Kerch Strait area. Such a pattern was apparently caused by the influence of the Azov Sea water spread westward along the Crimean shore from the strait. This work was supported by the Russian Science Foundation, Project 14-50-00095 and the Russian Foundation for Basic Research, Project 16-35-00156 mol_a.

DISTRIBUTION OF DISSOLVED METHANE IN SURFACE COASTAL WATERS OF THE NORTHEASTERN PART OF THE BLACK SEA

2017 ◽  
Author(s):  
Elena Kovaleva ◽  
Elena Kovaleva ◽  
Alexander Izhitskiy ◽  
Alexander Izhitskiy ◽  
Alexander Egorov ◽  
...  
Keyword(s):  
Black Sea ◽  
Natural Waters ◽  
Sea Water ◽  
The Black Sea ◽  
Methane Formation ◽  
Anthropogenic Pressure ◽  
Russian Science ◽  
Southeastern Part ◽  
Dissolved Methane ◽  
Continental Runoff

Studying of methane formation and distribution in natural waters is important for understanding of biogeochemical processes of carbon cycle, searching for oil and gas sections and evaluation of CH4 emissions for investigations of greenhouse effect. The Black Sea is the largest methane water body on our planet. However, relatively low values of methane concentration (closed to equilibrium with the atmospheric air) are typical of the upper aerobic layer. At the same time, the distribution pattern of CH4 in surface waters of coastal areas is complicated by the influence of coastal biological productivity, continental runoff, bottom sources, hydrodynamic processes and anthropogenic effect. The investigation is focused on the spatial variability of dissolved methane in the surface layer of the sea in coastal regions affected by the continental runoff and anthropogenic pressure. Unique in situ data on methane concentrations were collected along the ship track on 2 sections between Sochi and Gelendzhik (2013, 2014) and 2 sections between Gelendzhik and Feodosia (2015). Overall 170 samples were obtained. Gas-chromatographic analysis of the samples revealed increase of CH4 saturation in the southeastern part of the Crimean shelf and the Kerch Strait area. Such a pattern was apparently caused by the influence of the Azov Sea water spread westward along the Crimean shore from the strait. This work was supported by the Russian Science Foundation, Project 14-50-00095 and the Russian Foundation for Basic Research, Project 16-35-00156 mol_a.

Effect of sulfate on anaerobic processes fed with dual substrates

1995 ◽  
Vol 31 (9) ◽  
pp. 101-107 ◽  
Author(s):  
Chongchin Polprasert ◽  
Charles N. Haas
Keyword(s):  
Acetic Acid ◽  
Sulfate Reduction ◽  
Mixed Culture ◽  
Biogas Production ◽  
Cod Removal ◽  
Methane Formation ◽  
Batch Mode ◽  
Sulfate Reducing ◽  
Anaerobic Reactors ◽  
Optimal Feed

Anaerobic reactors were operated in a semi-batch mode and fed with the dual substrates glucose (G) plus acetic acid (Ac) as primary organic sources to study the effect of sulfate on COD oxidation. With glucose, COD removal by methane formation was seriously inhibited, resulting in COD accumulation in the reactor. Although acetic acid can be consumed by some sulfate-reducing species, it was not a major substrate for sulfate reduction, but was largely responsible for methane formation in the anaerobic mixed culture used in this study. With dual substrates, extreme inhibition of methanogenesis did not occur as did with glucose alone. Instead, methanogens were found to work in harmony with acid formers as well as sulfate reducers to oxidise COD. Interestingly, from 12-hour monitoring, increased G/Ac COD ratios decreased COD removal rates as well as biogas production, but resulted in higher sulfate reduction. This suggests that there should be an optimal feed G/Ac COD ratio, for which removal of both organics could be maximised.

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