CH4 Consumption Research Articles

Scalable Electro‐Biosynthesis of Ectoine from Greenhouse Gases

Converting greenhouse gases into valuable products has become a promising approach for achieving a carbon‐neutral economy and sustainable development. However, the conversion efficiency depends on the energy yield of the substrate. In this study, we developed an electro‐biocatalytic system by integrating electrochemical and microbial processes to upcycle CO2 into a valuable product (ectoine) using renewable energy. This system initiates the electrocatalytic reduction of CO2 to methane, an energy‐dense molecule, which then serves as an electrofuel to energize the growth of an engineered methanotrophic cell factory for ectoine biosynthesis. The scalability of this system was demonstrated using an array of ten 25 cm2 electrochemical cells equipped with a high‐performance carbon‐supported isolated copper catalyst. The system consistently generated methane at the cathode under a total partial current of approximately −37 A (~175 mmolCH4 h–1) and O2 at the anode under a total partial current of approximately 62 A (~583 mmolO2 h–1). This output met the requirements of a 3‐L bioreactor, even at maximum CH4 and O2 consumption, resulting in the high‐yield conversion of CO2 to ectoine (1146.9 mg L–1). This work underscores the potential of electrifying the biosynthesis of valuable products from CO2, providing a sustainable avenue for biomanufacturing and energy storage.

Scalable Electro-Biosynthesis of Ectoine from Greenhouse Gases.

Converting greenhouse gases into valuable products has become a promising approach for achieving a carbon-neutral economy and sustainable development. However, the conversion efficiency depends on the energy yield of the substrate. In this study, we developed an electro-biocatalyticsystem by integrating electrochemical and microbial processes to upcycle CO2 into a valuable product (ectoine) using renewable energy. This system initiates the electrocatalytic reduction of CO2 to methane, an energy-dense molecule, which then serves as an electrofuel to energize the growth of an engineered methanotrophic cell factory for ectoine biosynthesis. The scalability of this system was demonstrated using an array of ten 25 cm2 electrochemical cells equipped with a high-performance carbon-supported isolated copper catalyst. The system consistently generated methane at the cathode under a total partial current of approximately -37 A (~175 mmolCH4 h-1) and O2 at the anode under a total partial current of approximately 62 A (~583 mmolO2 h-1). This output met the requirements of a 3-L bioreactor, even at maximum CH4 and O2 consumption, resulting in the high-yield conversion of CO2 to ectoine (1146.9 mg L-1). This work underscores the potential of electrifying the biosynthesis of valuable products from CO2, providing a sustainable avenue for biomanufacturing and energy storage.

Advancing syngas production: A comparative techno-economic analysis of ICCU and CCU technologies for CO2 emission reduction

The Paris Agreement stresses the need to cut CO2 emissions, a global priority. Innovative methods like carbon capture and utilization (CCU) aim to limit the temperature increase to 1.5 °C by 2100. Traditional CCU involves separate CO2 collection and purification steps, while integrated carbon capture and utilization (ICCU) streamlines the process by capturing CO2 using CaO adsorbents and using it with CH4 on-site to produce syngas. ICCU reduces CO2 conversion costs by eliminating intermediaries, potentially resulting in lower operational costs than traditional CCU. This study employs the Aspen Plus model to evaluate ICCU and CCU processes, analyzing parameters such as CaCO3 consumption, purge production, annual CO and H2 production, energy balance, total annual costs, and CO production costs. Results show that ICCU generates 1.39 million tons of CO annually, with lower CH4 and CaCO3 consumption along with improved energy efficiency at 46.75% compared to CCU for 42.49%. ICCU incurs an annual capital outlay of $554.92 million with $396.94/ton of CO, while CCU costs M$853.10/year with $325.11/ton of CO. Notably, ICCU reduces costs of CO2 avoidance to $380.44/ton compared to $513.59/ton for CCU. These findings highlight ICCU as a more efficient and cost-effective approach to reducing CO2 emissions, aligning with the Paris Agreement goals and providing insights for future deployment and regulatory considerations. The use of Aspen Plus simulation software has been instrumental in facilitating the analysis, modeling, and validation of these conclusions.

Investigating the explosive characteristics of hydrogen/ n-butane blended fuel: Experimental and kinetic insights

Investigating the explosive characteristics of H2/n-C4H10 mixtures is crucial for the safe utilization of this blended fuel. Our study focused on varying equivalent ratios and hydrogen blending ratios within a closed 20-L spherical explosion vessel. Additionally, the microscopic kinetics of the reactions were analyzed through chemical reaction simulation. Our findings indicate that the most violent explosion occurred at an equivalent ratio of 1.2. Increasing hydrogen content intensified combustion reactions, reducing flame thickness and inducing cellular structures along the flame front. This escalation also increased explosion pressure, flame temperature, and flame propagation speed, elevating explosion risk. Moreover, the equilibrium molar fraction of O2 and CO2 decreased while that of H2O increased with higher hydrogen blending ratios. Correspondingly, the heat release rate and generation rates of H•, O•, and OH• radicals increased. Notably, the peak time of C2H4 and CH4 consumption rates preceded. Additionally, R5: O2 + H• = O• + OH• and R978: C4H10 + H• = SC4H9 + H2 represented crucial promoting and inhibiting steps, respectively. These insights deepen our understanding of the explosion mechanism of H2/n-C4H10 mixtures, providing a theoretical basis for designing safer protective measures and evaluating explosion risks in industrial production.

The role of halophyte-induced saline fertile islands in soil microbial biogeochemical cycling across arid ecosystems

Halophyte shrubs, prevalent in arid regions globally, create saline fertile islands under their canopy. This study investigates the soil microbial communities and their energy utilization strategies associated with tamarisk shrubs in arid ecosystems. Shotgun sequencing revealed that high salinity in tamarisk islands reduces functional gene alpha-diversity and relative abundance compared to bare soils. However, organic matter accumulation within islands fosters key halophilic archaea taxa such as Halalkalicoccus, Halogeometricum, and Natronorubrum, linked to processes like organic carbon oxidation, nitrous oxide reduction, and sulfur oxidation, potentially strengthening the coupling of nutrient cycles. In contrast, bare soils harbor salt-tolerant microbes with genes for autotrophic energy acquisition, including carbon fixation, H2 or CH4 consumption, and anammox. Additionally, isotope analysis shows higher microbial carbon use efficiency, N mineralization, and denitrification activity in tamarisk islands. Our findings demonstrate that halophyte shrubs serve as hotspots for halophilic microbes, enhancing microbial nutrient transformation in saline soils.

Methane hydrate formation in amino acids / sodium montmorillonite systems

To understand the occurrence of natural gas hydrates in seabed sediments, it is crucial to examine the mechanisms of methane (CH4) hydrate formation in sodium montmorillonite (Na-Mt) systems in the presence of amino acid. Accordingly, this study employed kinetics experiments and molecular dynamics simulations to investigate CH4 hydrate nucleation and growth in an Na-Mt system containing alanine (Ala), leucine (Leu), and phenylalanine (Phe), respectively. Kinetics and Raman experiments showed that, compared with Ala, Leu and Phe enhanced hydrogen bonding between water molecules surrounding Na-Mt. This enhancement was due to the long carbon chain of Leu and the phenyl ring of Phe and facilitated CH4 hydrate formation. Moreover, in the Na-Mt system, Ala reduced CH4 consumption, whereas Leu and Phe increased CH4 consumption. Molecular dynamics simulations revealed that the strength of electrostatic interactions between the negatively charged Na-Mt surface and the functional groups of amino acids affected the distribution of amino acids, thereby altering CH4 aggregation and CH4 hydrate nucleation processes. The strong interaction between Na-Mt and Ala significantly disrupted interfacial interactions between Na-Mt and water molecules. In contrast, the weaker interactions between Na-Mt and Leu and Phe, respectively, meant that these amino acids affected CH4 hydrate nucleation in the bulk-like solution by influencing the arrangement of water molecules. These findings indicate that interfacial interactions between Na-Mt and amino acids play a crucial role in CH4 hydrate formation. Overall, this study generated insights into the formation kinetics and nucleation properties of CH4 hydrates in clay mineral–amino acid complexes that may increase understanding about the occurrence of natural gas hydrates in marine sediments.

Operando Spectroscopic Studies of Solid Oxide Fuel Cell Operation Using Dimethyl Ether as an Alternative Fuel

Dimethyl ether (DME) is an oxygen-containing fuel that is an attractive alternative to the reforming of light alkanes like CH4. Its higher volumetric exergy compared to CH4 yields comparable power densities to other fuels while decreasing its potential for performance degradation that results from coking. We have characterized an SOFC operating at 800 °C on DME using a suite of operando optical and ex post facto methods. Based on exhaust gas infrared spectroscopy, DME decomposes to CH4, C2H2, H2O, CO2, and CO. Electrochemical analysis indicates that under dry DME the maximum power output of an anode supported button cell Ni-YSZ SOFC is only 10% lower than under CH4 (where H content was matched in the fuel stream). FTIR analysis of the anode exhaust gas indicates an electrochemical response under galvanostatic conditions resulting in the consumption of both CH4 and C2H2 to form CO, CO2, and H2O. Operando near-infrared thermal imaging reveal more cooling at the anode surface with DME than CH4 resulting from increased endothermic cracking of CH4. Additional contributions to the cooling are possible from reforming reactions.

The effect of CO content on CH4/CO/H2 rotating detonation wave propagation characteristics

Rotating detonation experiments were conducted using CH4/CO/H2 (methane/carbon monoxide/hydrogen) mixtures with varying CO contents, the modes of rotating detonation wave (RDW) propagation in the mixtures were analyzed, and the impact of CO content on the propagation characteristics of the RDW in the gas mixture was compared. Three propagation modes of RDW were observed: sawtooth wave mode, mixed mode, and single wave mode. An increase in the CO content resulted in an upward shift in the range of working equivalence ratios for different gas mixtures. Additionally, the propagation modes of the same gas mixture change with increased fuel flow rate. When the equivalence ratio is below 1.13, it is observed that the gas mixture with the lowest CO content exhibits the highest RDW velocity and the shortest time required to establish RDW. This was attributed to the higher content of oxygen-containing functional groups, such as OH (hydroxyl), HO2 (peroxyhydroxyl), and O (oxygen atom), which were present under lean combustion conditions, along with the highest mass content of H2 in the gas mixture with the lowest CO content. Conversely, for equivalence ratios above 1.13, it is observed that the gas mixture with the highest CO content exhibits the highest propagation velocity and the shortest time required to establish RDW. This was attributed to the lowest mass content of CH4 and H2 in the gas mixture with the highest CO content at the same equivalence ratio, along with the inhibitory effect of elevated CO content on CH4 consumption under fuel-rich combustion conditions. The increase in the CO content resulted in maximum propagation velocities of the detonation wave being achieved for the three gas mixtures at equivalence ratios of 0.91, 1.09, and 1.19, with corresponding velocities of 1136.7, 1108.7, and 1113.2 m/s, and the shortest times required to establish RDW were measured at 1.5, 1.1, and 0.8 ms for the respective mixtures.

Revisit the PAH and soot formation in high-temperature pyrolysis of methane

As the major component of natural gas, most basic and stable hydrocarbon molecule, methane (CH4) is an important source in industrial processing. The polycyclic aromatic hydrocarbons (PAHs) and the soot produced in the utilization of CH4 also attract particular attention. In this work, CH4 pyrolysis was studied with gas chromatographs (GCs) and a gas chromatography-mass (GC-MS) spectrometry within the temperature range of 1073–1623 K at atmospheric pressure. Mole fraction profiles of 11 species, including CH4, C2H2, C2H4, C2H6, aC3H4, pC3H4, C3H6, C4H6, C6H6, C10H8 (naphthalene) and C12H8 (acenaphthylene) were quantified. C10H8 and C12H8 were detected during the pyrolysis of CH4. A detailed kinetic model involving 300 species and 1840 reactions was proposed with reasonable prediction against the measured data. During pyrolysis, CH4 is mainly consumed by the H-abstraction reactions. 2CH3=C2H5+H and C9H7+C3H3=A2R5+H2 are the two major reactions controlling CH4 consumption according to sensitivity analysis. In addition, the soot generated in the reactor was analyzed by Raman spectroscopy and Scanning Electron Microscope (SEM), showing the morphology and structural characteristics of the soot. The detailed formation and consumption pathways of PAHs such as naphthalene and acenaphthylene were analyzed. This work will enrich the understanding of CH4 pyrolysis and promote experimental and theoretical studies on the formation of PAHs and soot.

Carbon Dioxide Driven Methane Consumption in Soil Ecosystem

Soil is an important source and sink of greenhouse gas carbon dioxide (CO2) and methane (CH4). During CH4 consumption CO2 is produced as an end product. It is generally assumed that CO2 would inhibit CH4 consumption due to feedback inhibition. To test the effect of CO2 on methanotrophy, experiments were conducted in microcosms with different initial concentration of CO2 and CH4. Changes in CH4 consumption potential and abundance of pmoA gene copies in relation to CO2 concentration were estimated. In general, CH4 consumption ceased in the absence of CO2. In presence of CO2, rate of CH4 consumption (ng CH4 consumed g−1 soil d−1) varied from 0.283 to 0.481 at 1000 ppm of CH4 and 2.958 to 4.994 at 10,000 ppm of CH4. Abundance of methanotrophs (pmoA gene copies g−1 soil) ranged from 4.5 × 105 to 107 × 105 g−1 soil. A follow up experiment was carried out to evaluate CH4 consumption in the presence or absence of CO2, which proved that CO2 is essential for CH4 consumption. Study concludes that CO2 is a precursor molecule for CH4 consumption in soil ecosystem and methanotrophs are capable of mitigating both the greenhouse gases, CH4 and CO2.

Greenhouse gas emission potential of tropical coastal sediments in densely urbanized area inferred from metabarcoding microbial community data

Although benthic microbial community offers crucial insights into ecosystem services, they are underestimated for coastal sediment monitoring. Sepetiba Bay (SB) in Rio de Janeiro, Brazil, holds long-term metal pollution. Currently, SB pollution is majorly driven by domestic effluents discharge. Here, functional prediction analysis inferred from 16S rRNA gene metabarcoding data reveals the energy metabolism profiles of benthic microbial assemblages along the metal pollution gradient. Methanogenesis, denitrification, and N2 fixation emerge as dominant pathways in the eutrophic/polluted internal sector (Spearman; p < 0.05). These metabolisms act in the natural attenuation of sedimentary pollutants. The methane (CH4) emission (mcr genes) potential was found more abundant in the internal sector, while the external sector exhibited higher CH4 consumption (pmo + mmo genes) potential. Methanofastidiosales and Exiguobacterium, possibly involved in CH4 emission and associated with CH4 consumers respectively, are the main taxa detected in SB. Furthermore, SB exhibits higher nitrous oxide (N2O) emission potential since the norB/C gene proportions surpass nosZ up to 4 times. Blastopirellula was identified as the main responsible for N2O emissions. This study reveals fundamental contributions of the prokaryotic community to functions involved in greenhouse gas emissions, unveiling their possible use as sentinels for ecosystem monitoring.

Nitrite-dependent microbial utilization for simultaneous removal of sulfide and methane in sewers

Chemicals are commonly dosed in sewer systems to reduce the emission of hydrogen sulfide (H2S) and methane (CH4), incurring high costs and environmental concerns. Nitrite dosing is a promising approach as nitrite can be produced from urine wastewater, which is a feasible integrated water management strategy. However, nitrite dosing usually requires strict conditions, e.g., relatively high nitrite concentration (e.g., ∼200 mg N/L) and acidic environment, to inhibit microorganisms. In contrast to “microbial inhibition”, this study proposes “microbial utilization” concept, i.e., utilizing nitrite as a substrate for H2S and CH4 consumption in sewer. In a laboratory-scale sewer reactor, nitrite at a relatively low concentrations of 25–48 mg N/L was continuously dosed. Two nitrite-dependent microbial utilization processes, i.e., nitrite-dependent anaerobic methane oxidation (n-DAMO) and microbial sulfide oxidation, successfully occurred in conjunction with nitrite reduction. The occurrence of both processes achieved a 58 % reduction in dissolved methane and over 90 % sulfide removal in the sewer reactor, with microbial activities measured as 15.6 mg CH4/(L·h) and 29.4 mg S/(L·h), respectively. High copy numbers of n-DAMO bacteria and sulfide-oxidizing bacteria (SOB) were detected in both sewer biofilms and sediments. Mechanism analysis confirmed that the dosed nitrite at a relatively low level did not cause the inhibition of sulfidogenic process due to the downward migration of activity zones in sewer sediments. Therefore, the proposed “microbial utilization” concept offers a new alternative for simultaneous removal of sulfide and methane in sewers.

Microbial Communities in Standing Dead Trees in Ghost Forests are Largely Aerobic, Saprophytic, and Methanotrophic

Standing dead trees (snags) are recognized for their influence on methane (CH4) cycling in coastal wetlands, yet the biogeochemical processes that control the magnitude and direction of fluxes across the snag-atmosphere interface are not fully elucidated. Herein, we analyzed microbial communities and fluxes at one height from ten snags in a ghost forest wetland. Snag-atmosphere CH4 fluxes were highly variable (− 0.11–0.51 mg CH4 m−2 h−1). CH4 production was measured in three out of ten snags; whereas, CH4 consumption was measured in two out of ten snags. Potential CH4 production and oxidation in one core from each snag was assayed in vitro. A single core produced CH4 under anoxic and oxic conditions, at measured rates of 0.7 and 0.6 ng CH4 g−1 h−1, respectively. Four cores oxidized CH4 under oxic conditions, with an average rate of − 1.13 ± 0.31 ng CH4 g−1 h−1. Illumina sequencing of the V3/V4 region of the 16S rRNA gene sequence revealed diverse microbial communities and indicated oxidative decomposition of deadwood. Methanogens were present in 20% of the snags, with a mean relative abundance of < 0.0001%. Methanotrophs were identified in all snags, with a mean relative abundance of 2% and represented the sole CH4-cycling communities in 80% of the snags. These data indicate potential for microbial attenuation of CH4 emissions across the snag-atmosphere interface in ghost forests. A better understanding of the environmental drivers of snag-associated microbial communities is necessary to forecast the response of CH4 cycling in coastal ghost forest wetlands to a shifting coastal landscape.

Leafcutter ants enhance microbial drought resilience in tropical forest soil.

We conducted a research campaign in a neotropical rainforest in Costa Rica throughout the drought phase of an El-Nino Southern Oscillation event to determine microbial community dynamics and soil C fluxes. Our study included nests of the leafcutter ant Atta cephalotes, as soil disturbances made by these ecosystem engineers may influence microbial drought response. Drought decreased the diversity of microbes and the abundance of core microbiome taxa, including Verrucomicrobial bacteria and Sordariomycete fungi. Despite initial responses of decreasing diversity and altered composition, 6 months post-drought the microbiomes were similar to pre-drought conditions, demonstrating the resilience of soil microbial communities to drought events. A. cephalotes nests altered fungal composition in the surrounding soil, and reduced both fungal mortality and growth of Acidobacteria post-drought. Drought increased CH4 consumption in soils due to lower soil moisture, and A. cephalotes nests decrease the variability of CH4 emissions in some soil types. CH4 emissions were tracked by the abundance of methanotrophic bacteria and fungal composition. These results characterize the microbiome of tropical soils across both time and space during drought and provide evidence for the importance of leafcutter ant nests in shaping soil microbiomes and enhancing microbial resilience during climatic perturbations.

Black soldier fly larvae mitigate greenhouse gas emissions from domestic biodegradable waste by recycling carbon and nitrogen and reconstructing microbial communities.

Black soldier fly larvae have been proven to reduce greenhouse gas emissions in the treatment of organic waste. However, the microbial mechanisms involved have not been fully understood. The current study mainly examined the dynamic changes of carbon and nitrogen, greenhouse gas emissions, the succession of microbial community structure, and changes in functional gene abundance in organic waste under larvae treatment and non-aeration composting. Thirty percent carbon and 55% nitrogen in the organic waste supplied were stored in larvae biomass. Compared to the non-aeration composting, the larvae bioreactor reduced the proportion of carbon and nitrogen converted into greenhouse gases (CO2, CH4, and N2O decreased by 62%, 87%, and 95%, respectively). 16S rRNA sequencing analysis indicated that the larvae bioreactor increased the relative abundance of Methanophaga, Marinobacter, and Campylobacter during the bioprocess, enhancing the consumption of CH4 and N2O. The metagenomic data showed that the intervention of larvae reduced the ratio of (nirK + nirS + nor)/nosZ in the residues, thereby reducing the emission of N2O. Larvae also increased the functional gene abundance of nirA, nirB, nirD, and nrfA in the residues, making nitrite more inclined to be reduced to ammonia instead of N2O. The larvae bioreactor mitigated greenhouse gas emissions by redistributing carbon and nitrogen and remodeling microbiomes during waste bioconversion, giving related enterprises a relative advantage in carbon trading.

Electrochemically coupled CH4 and CO2 consumption driven by microbial processes

The chemical transformations of methane (CH4) and carbon dioxide (CO2) greenhouse gases typically have high energy barriers. Here we present an approach of strategic coupling of CH4 oxidation and CO2 reduction in a switched microbial process governed by redox cycling of iron minerals under temperate conditions. The presence of iron minerals leads to an obvious enhancement of carbon fixation, with the minerals acting as the electron acceptor for CH4 oxidation and the electron donor for CO2 reduction, facilitated by changes in the mineral structure. The electron flow between the two functionally active microbial consortia is tracked through electrochemistry, and the energy metabolism in these consortia is predicted at the genetic level. This study offers a promising strategy for the removal of CH4 and CO2 in the natural environment and proposes an engineering technique for the utilization of major greenhouse gases.

Regulation of nitrite-dependent anaerobic methane oxidation bacteria by available phosphorus and microbial communities in lake sediments of cold and arid regions

As global anthropogenic nitrogen inputs continue to rise, nitrite-dependent anaerobic methane oxidation (N-DAMO) plays an increasingly significant role in CH4 consumption in lake sediments. However, there is a dearth of knowledge regarding the effects of anthropogenic activities on N-DAMO bacteria in lakes in the cold and arid regions. Sediment samples were collected from five sampling areas in Lake Ulansuhai at varying depth ranges (0–20, 20–40, and 40–60 cm). The ecological characterization and niche differentiation of N-DAMO bacteria were investigated using bioinformatics and molecular biology techniques. Quantitative PCR confirmed the presence of N-DAMO bacteria in Lake Ulansuhai sediments, with 16S rRNA gene abundances ranging from 1.72 × 104 to 5.75 × 105 copies·g−1 dry sediment. The highest abundance was observed at the farmland drainage outlet with high available phosphorus (AP). Anthropogenic disturbances led to a significant increase in the abundance of N-DAMO bacteria, though their diversity remained unaffected. The heterogeneous community of N-DAMO bacteria was affected by interactions among various environmental characteristics, with AP and oxidation-reduction potential identified as the key drivers in this study. The Mantel test indicated that the N-DAMO bacterial abundance was more readily influenced by the presence of the denitrification genes (nirS and nirK). Network analysis revealed that the community structure of N-DAMO bacteria generated numerous links (especially positive links) with microbial taxa involved in carbon and nitrogen cycles, such as methanogens and nitrifying bacteria. In summary, N-DAMO bacteria exhibited sensitivity to both environmental and microbial factors under various human disturbances. This study provides valuable insights into the distribution patterns of N-DAMO bacteria and their roles in nitrogen and carbon cycling within lake ecosystems.

Methanol excretion by Methylomonas methanica is induced by the supernatant of a methanotrophic consortium

AbstractBACKGROUNDMethanotrophs play an important role in mitigating methane (CH4) emissions in ecosystems. They closely interact with other microorganisms forming communities where the cross‐feeding of metabolites, presumably methanol (MeOH), is essential for the growth and activity of non‐methanotrophs. The experiments in this study were focused on investigating the effect of adding the supernatant from a methanotrophic consortium to pure cultures of Methylomonas methanica.RESULTSMethanol dehydrogenase inhibition caused the accumulation of MeOH, which resulted in a significant production after 3 h, with 1.99 mmol L−1 CH3OH. The addition of the supernatant was associated with the excretion of MeOH by M. methanica and enhancement of the CH4 consumption rate, despite a reduction in growth. The maximum MeOH concentrations were between 0.7 and 1.5 mmol L−1 CH3OH.CONCLUSIONThese findings indicate that MeOH excretion may indeed be linked to a metabolic imbalance, which could potentially be compensated through the cross‐feeding of metabolites within the methanotrophic community. © 2024 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry (SCI).

Spatial variation of net methane uptake in Arctic and subarctic drylands of Canada and Greenland

The importance of uptake of atmospheric methane (CH4) in dry Arctic soils for the total Arctic CH4 budget is unresolved. This is partly due to lack of data on the spatial variability of net CH4 consumption and understanding of the main process drivers. We measured net CH4 consumption in Arctic and subarctic landscapes located in in Disko Bay Area and Kangerlussuaq in Western Greenland and in the St. Elias Range in the Yukon, Canada, respectively. Our aim was to characterize the in situ spatial variability of net CH4 uptake in hitherto unexplored Arctic dry upland soils to explore possible limits and environmental drivers across the Arctic geodiversity. Furthermore, we sampled soil for incubation experiments to investigate how net CH4 oxidation responded to changes in soil moisture in contrasting geomorphic settings and parent geological parent materials. We used a laser-based fast deployable chamber system for flux measurements. All studied sites were net sinks of atmospheric CH4 with an average flux −7.5 ± 5.6 μmol CH4 m-2h−1, that are in the upper range of reported net CH4 uptake fluxes in similar soils of the Arctic. The large observed spatial variability within all studied sites (coefficient of variation 50 – 120 %) highlights the need for careful research design allowing for many spatial replicates to achieve representative values. Sites with an active geomorphic environment (abrasion plateau, riverbeds, mountain tops) generally had lower than average net CH4 uptake. Our incubation studies revealed that subsurface CH4 oxidation is the main driver of net surface-atmosphere exchange and that net CH4 oxidation in these layers responded more to changes to soil moisture than in near surface layers. Our study shows surprisingly similar flux magnitudes of net CH4 uptake across widely different landscape forms and geologic parent material, but responding similarly to soil hydrology and geomorphic disturbance, indicating global controls on the net CH4 oxidation in these dry upland environments.

Catalytic performance of NixCoy catalysts supported on honeycomb-lantern-like CeO2 for dry reforming of methane: Synergistic effect and kinetic study

Dry reforming of methane (DRM) is considered one of the most efficient methods for carbon utilization, as it can transform greenhouse gases (CH4 and CO2) into syngas (CO and H2) which could be widely used in the production of high-value hydrocarbons. The synergistic effect between Ni and Co is leveraged to enhance the coke resistance and stability of Ni-based catalyst during the DRM process, building upon the surface spatial confinement provided by honeycomb-lantern-like CeO2 support. The enhanced catalytic performance of Ni0.9Co0.1 catalyst can be attributed primarily to the addition of cobalt, which facilitates CO2 adsorption and activation, further promotes the Boudouard reaction and aids in the elimination of coke. This phenomenon is supported by evidence from CO2-TPD, XPS, SEM, TGA, XRD, and CO2-TPO analyses. Furthermore, the kinetics of Ni0.9Co0.1 are examined using Power-Law (PL) and Langmuir-Hinshelwood (LH) mechanisms, obtaining the explicit equations for the rate constants (k and kr), reaction orders of the reactants (α and β), and adsorption equilibrium constants (KCH4 and KCO2). The comparison of the predicted CH4 consumption rates with the experimental rates suggests that the LH mechanism is notably more precise than PL mechanism for Ni0.9Co0.1 catalyst. Moreover, the relevant kinetic parameters (the activation energy and pre-exponential factor), pertinent to coke gasification process for the spent Ni0.9Co0.1 and Ni1.0, are determined and calculated through CO2-TPO characterization and the modified Wigner-Polanyi equation.