Methane Carbon Dioxide Research Articles

Supported-Single Nickel Atom Catalysts for the Methanation of Carbon Dioxide.

Synthesis of twenty-seven bimetallic catalysts consisting of nickel and one of nine different dopants (B, Co, Cu, Fe, Mg, Mn, Sn, V, and Zn) supported on three different metal oxides (Al2O3, CeO2, and SiO2) is carried out via organometallic grafting. The catalysts are evaluated for their activity and selectivity for the CO2 methanation reaction at a feed ratio of H2/CO2 of 4 at 300 °C in a high-throughput flow reactor system. After in situ pre-activation (500 °C in H2), Ni/Co/CeO2 exhibited high conversion (84.3%) and selectivity for methane (99.6%). Ni/Co/CeO2 was characterized by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction, H2-temperature-programmed reduction (H2-TPR), and CO2-temperature-programmed desorption (CO2-TPD). HRTEM showed the presence of single Ni and Co atoms on ceria after pre-reduction at 500 °C and after the methanation reaction at 300 °C for 15 h. XPS determined that the strong interaction between Ni, Co, and ceria increased after the reduction, leading to a charge transfer between Ni and Ce that created oxygen vacancies in ceria. Nickel was found to be Ni2+ in the as-prepared material and was partially reduced in the presence of cobalt and after the activation in H2 at 500 °C. The DFT results show that both nickel and cerium exhibit lower Bader charges in the Ni/Co/CeO2 system, confirming that the presence of cobalt enhances the reduction of both Ni and Ce through electronic interactions. This indicates that single cationic Ni atoms are highly effective for the methanation reaction. The organometallic grafting technique is found to be efficient for synthesizing catalysts with highly homogeneous dispersed species at low metal loadings (0.16 wt % Ni-0.15 wt % Co), which leads to high turnover frequency (up to 248.7 h-1) and durability for methanation.

Management approach matters: meeting seagrass recovery and carbon mitigation goals

Seagrass habitats support biodiversity, improve water quality, protect coastlines, and sequester carbon, among other essential ecosystem functions, yet they are declining worldwide due to human activity. Seagrass restoration and conservation can act as nature-based solutions for climate change, garnering growing interest from a diversity of stakeholders globally. Despite this interest, no seagrass projects have yet received carbon credits under international voluntary carbon standards. There is a clear need to better understand potential carbon mitigation outcomes of seagrass conservation and restoration practices. Here, we developed a mechanistic model based on a temperate meadow of Zostera marina to estimate carbon benefits (including net carbon dioxide removals, reductions, and methane and nitrous oxide fluxes) over 10 years as a result of four theoretical seagrass management scenarios, selected for their prevalence and potential—(1) restoration via seeding, (2) restoration via transplanting, (3) conserving a meadow and associated sediment from loss (e.g., from dredging), and (4) infilling an area with sediment prior to transplanting. We found significant differences and high variability in carbon benefits between these management scenarios. Restoration via transplant led to higher carbon gains than restoration via seeding, driven by more rapid areal bed expansion in transplanted meadows. However, the infill (adding 1 m of sediment) and conservation (preventing loss of 1 m of sediment) scenarios had total carbon benefits roughly 13–33 times (respectively) higher than the seeding and transplanting scenarios in which no sediment was mobilized. Within the model presented here, the minimum estimated revenue shows a 6 Ha seeding project generating as little as $1189 over 10 years (39.6 ± 6.2 T CO2eq), while a 100 Ha conservation project could generate a maximum of $1.53 million over this same time period (21,910 ± 2196 T CO2eq), excluding costs for project implementation and MRV (monitoring, reporting and verification). Voluntary carbon credit revenue variability (ranging from $198 to $15,337 per Ha) is driven by project size, project approach, and carbon price, among other factors. This work highlights the need for careful, context-specific consideration for if and how carbon finance might support seagrass recovery goals. Seascape-level approaches that pair strategic sediment management and avoided emissions with habitat restoration may lead to the highest climate mitigation benefits, while simultaneously supporting biodiversity and other ecosystem functions.

Assessing the methanogenic activity of microbial communities enriched from a depleted reservoir.

Using a depleted gas reservoir as a natural reactor is a novel approach for microbial methanation of hydrogen (H2) and carbon dioxide (CO2) into methane (CH4). This approach, known as underground biomethanation reactor (UMR), could enable the simultaneous valorization of geologically sequestered CO2 and the excess renewable energy, stored in the form of H2 in the same formation as the CO2. In this study, we explore the possibility to trigger biomethanation from formation water sample by testing various carbon sources (CO2, trypticase peptone, glucose, and acetate) in batch test with a defined mineral medium. Obtained results show that trypticase peptone supplementation greatly increased methane production and the enrichment of methanogenic archaea, outperforming alternative carbon sources. 16S rRNA amplicon sequencing of the enriched consortia revealed that supplementation of trypticase peptone and a mixture of H2:CO2 (80:20), resulted in the selection of a mixed culture dominated by microorganisms assigned to the Methanothermobacterium, Garciella, and Caminicella genera. Furthermore, KEGG (Kyoto Encyclopedia of Genes and Genomes) and COG (Clusters of Orthologous Genes) predictive functional analyses underline a possible syntrophic relationship, enhancing the conversion of H2 and CO2 into CH4. This work lays the groundwork for biologically exploiting a depleted gas reservoir by implementing the UMR technology.

Utilizing zeolitic imidazolate framework-8 for enhanced carbon dioxide/methane separation and improved carbon dioxide methanation performance.

Utilizing zeolitic imidazolate framework-8 for enhanced carbon dioxide/methane separation and improved carbon dioxide methanation performance.

Cold Seeps and Coral Reefs in Northern Norway: Carbon Cycling in Marine Ecosystems With Coexisting Features

AbstractCold seeps and cold‐water corals (CWCs) coexist on Northern Norway's continental shelf at the Hola trough between Lofoten and Vesterålen. Here, cold seeps release methane from the seabed, yet none reaches the sea surface. Instead, the methane dissolves and disperses in the ocean where it is ultimately consumed by methane‐oxidizing microorganisms. These microorganisms metabolize methane and release carbon dioxide and dissolved organic matter (DOM), which may impact the biogeochemical habitat of CWCs in close vicinity of cold seeps. We investigated the biogeochemistry of carbon, carbon isotopes, nutrients, DOM compositions, and microbial diversity in the water column. Our results indicated that dissolved inorganic carbon concentrations were 29% higher near cold seeps with modified carbon's isotopic compositions. The hydrophysical parameters and surface‐to‐bottom control of sinking particles mainly govern water column productivity and nutrient cycle. DOM compositions implied that the seep‐associated microbiomes modify DOM's chemical diversity and isotopic composition at CWCs and the entire water column near cold seeps. Cold seeps and CWCs coexist in Northern Norway's continental shelves; however, enhanced water temperatures and consequent increase in methane release at cold seeps may modify the carbon cycling in the area, which could mitigate the ecological role and functioning of CWC reefs in the future.

Modulation strategy and effect of metal-support interaction over catalysts for carbon dioxide methanation

Modulation strategy and effect of metal-support interaction over catalysts for carbon dioxide methanation

Mohr–Coulomb-Model-Based Study on Gas Hydrate-Bearing Sediments and Associated Variance-Based Global Sensitivity Analysis

Different gas hydrate types, such as methane hydrate and carbon dioxide hydrate, exhibit distinct geomechanical responses and hydrate morphologies in gas-hydrate-bearing sediments (GHBSs). However, most constitutive models for GHBSs focus on methane-hydrate-bearing sediments (MHBSs), while largely overlooking carbon-dioxide-hydrate-bearing sediments (CHBSs). This paper proposes a modified Mohr–Coulomb (M-C) model for GHBSs that incorporates the geomechanical effects of both MHBSs and CHBSs. The model integrates diverse hydrate morphologies—cementing, load-bearing, and pore-filling—into hydrate saturation and incorporates an effective confining pressure. Its validity was demonstrated through simulations of reported triaxial compression tests for both MHBSs and CHBSs. Moreover, a variance-based sensitivity analysis using Sobol’s method evaluated the effects of hydrate-related soil properties on the geomechanical behavior of GHBSs. The results indicate that the shear modulus influences the yield axial strain of the CHBSs and could be up to 1.15 times more than that of the MHBSs. Similarly, the bulk modulus showed an approximate 5% increase in its impact on the yield volumetric strain of the CHBSs compared with the MHBSs. These findings provide a unified framework for modeling GHBSs and have implications for CO2-injection-induced methane production from deep sediments, advancing the understanding and simulation of GHBS geomechanical behavior.

Global peatland greenhouse gas dynamics: state of the art, processes, and perspectives.

Natural peatlands regulate greenhouse gas (GHG) fluxes through a permanently high groundwater table, causing carbon dioxide (CO2) assimilation but methane (CH4) emissions due to anaerobic conditions. By contrast, drained and disturbed peatlands are hotspots for CO2 and nitrous oxide (N2O) emissions, while CH4 release is low but high from drainage ditches. Generally, in low-latitude (tropical and subtropical) peatlands, emissions of all GHGs are higher than in high-latitude (temperate, boreal, and Arctic) peatlands. Their inherent dependence on the water regime makes peatlands highly vulnerable to both direct and indirect anthropogenic impacts, including climate change-induced drying, which is creating anthro-natural ecosystems. This paper presents state-of-the-art knowledge on peatland GHG fluxes and their key regulating processes, highlighting approaches to study spatio-temporal dynamics, integrated methods, direct and indirect human impacts, and peatlands' perspectives.

Rising Water Levels and Vegetation Shifts Drive Substantial Reductions in Methane Emissions and Carbon Dioxide Uptake in a Great Lakes Coastal Freshwater Wetland.

Coastal freshwater wetlands are critical ecosystems for both local and global carbon cycles, sequestering substantial carbon while also emitting methane (CH4) due to anoxic conditions. Estuarine freshwater wetlands face unique challenges from fluctuating water levels, which influence water quality, vegetation, and carbon cycling. However, the response of CH4 fluxes and their drivers to altered hydrology and vegetation remains unclear, hindering mechanistic modeling. To address these knowledge gaps, we studied an estuarine freshwater wetland in the Great Lakes region, where rising water levels led to a vegetation shift from emergent Typha dominance in 2015-2016 to floating-leaved species in 2020-2022. Using eddy covariance flux measurements during the peak growing season (June-September) of both periods, we observed a 60% decrease in CH4 emissions, from 81 ± 4 g C m-2 in 2015-2016 to 31 ± 3 g C m-2 in 2020-2022. This decline was driven by two main factors: (1) higher water levels, which suppressed ebullitive fluxes via increased hydrostatic pressure and extended CH4 residence time, enhancing oxidation potential in the water column; and (2) reduced CH4 conductance through plants. Net carbon dioxide (CO2) uptake decreased by 90%, from -267 ± 26 g C m-2 in 2015-2016 to -27 ± 49 g C m-2 in 2020-2022. Additionally, diel CH4 flux patterns shifted, with a distinct morning peak observed in 2015-2016 but absent in 2020-2022, suggesting changes in plant-mediated transport and a potential decoupling from photosynthesis. The dominant factors influencing CH4 fluxes shifted from water temperature and gross primary productivity in 2015-2016 to atmospheric pressure in 2020-2022, suggesting an increased role of ebullition as a primary transport pathway. Our results demonstrate that changes in water levels and vegetation can substantially alter CH4 and CO2 fluxes in coastal freshwater wetlands, underscoring the critical role of hydrological shifts in driving carbon dynamics in these ecosystems.

Competitive methane/carbon dioxide adsorption mechanism in shale kerogen using molecular modeling approach

Research on CH4/CO2 competitive adsorption mechanism in shale kerogen based on molecular simulation. In order to study the competitive adsorption mechanism of CO2 and CH4 in kerogen. On the basis of gas isothermal adsorption experimental data, molecular simulation was used to analyze the competitive adsorption mechanism of CO2 and CH4 in the kerogen, which provides support for the technology of improving the recovery rate of shale gas reservoirs. The results show that: when the proportion of CO2 in the gas mixture rises from 10% to 90%, the ability of CO2 to replace CH4 increases but the adsorption position of the gas remains unchanged; the increase of pressure (5 MPa–40MPa) and temperature (30 °C–90 °C) causes the change of the energy distribution of the different gases, which ultimately leads to the change of energy distribution of CO2 and CH4 changes in the competitive adsorption behavior of CO2 and CH4. The conclusion is that changes in temperature and pressure affect the energy of different gas molecules, ultimately leading to changes in the competitive adsorption behavior between methane molecules and carbon dioxide molecules.

Influence of Low Metal Loading on the Catalytic Activity and Stability of Supported Metal Catalysts for Methane Dry Reforming

This study aims to utilize highly active nickel catalysts supported by zirconia for the dry reforming of methane (DRM). The catalysts were prepared with a low nickel loading of 5 wt%. This study seeks to investigate how the limited nickel content (5 wt%) and various preparation methods impact the properties of the catalysts as well as their performance during the DRM reaction. To assess the physicochemical properties of the catalysts, several techniques were employed, including X-ray diffraction (XRD), N2 physisorption, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The evaluation of the activity and stability of the synthesized catalysts demonstrated that a specific configuration of the Ni/ZrO2 catalyst exhibited the best performance. The study further revealed a clear distinction between the two preparation methods. Catalysts prepared via co-precipitation displayed high activity of methane conversion (53%) and carbon dioxide conversion (55%) across all tested temperatures and maintained stability throughout the reaction. In contrast, catalysts synthesized through impregnation exhibited lower activity at all temperatures and were deactivated during the testing period. The observed catalytic activity can be attributed to a combination of factors, including highly dispersed NiO particles and a high number of oxygen vacancies within the catalyst structure. These findings underscore the critical role of catalyst preparation methods and the resulting physicochemical properties, such as phase composition and particle size, in determining catalytic performance. This highlights the potential for further enhancing the performance of these catalyst systems through optimization of preparation methods and exploration of novel support materials for the development of more efficient and sustainable DRM technologies.

Methanation of carbon dioxide over zirconium-tin oxide-based catalyst

An advanced catalyst, [Formula: see text], was synthesized for the methanation of [Formula: see text] under moderate conditions of atmospheric pressure and low [Formula: see text] concentration (4 vol%). The use of scrutinyite-type [Formula: see text] improved the catalytic activity, likely because of abundant oxygen vacancies for [Formula: see text] adsorption and good redox properties for cleavage of the C-O bond of adsorbed [Formula: see text]. The [Formula: see text] yield of 18 wt.% Ni/20 wt.% [Formula: see text] reached 61.0% with high [Formula: see text] conversion (58.4%) at 350°C using 1 vol% [Formula: see text]-4vol% [Formula: see text]-95 vol% Ar at atmospheric pressure.

COMPREHENSIVE TECHNOLOGY FOR UTILIZATION OF ACID CONDENSATE FROM FLUE GAS AFTER BOILER UNITS

This paper presents material related to the comprehensive technology for the utilization of acidic condensate formed at thermal power plants and contains a series of issues related to the processes of neutralization and degassing of the liquid, further carbon dioxide methanation, and water electrolysis. The proposed technology for acidic condensate utilization will address several environmentally oriented issues, including reducing CO2 emissions into the atmosphere, preventing acidic effluents from entering wastewater and natural water bodies, saving water resources, and promoting alternative fuel production. The basis of the technology is a cavitation reactor, which allows almost complete extraction of carbon dioxide gas present in the form of bubbles ranging in size from 5 µm to 0.5 µm. Experimental and theoretical studies of carbon dioxide extraction, the efficiency of liquid neutralization, and the sizes of bubbles that can be activated under the proposed processing regimes for carbon dioxide extraction were conducted to purposefully control the liquid neutralization processes through cavitation mechanisms implemented in the equipment of this technological scheme. The primary idea of the technology was associated with finding ways for effective reagent-free neutralization of condensate by extracting CO2. Treatment of condensate using the proposed technology practically realizes complete extraction of carbon dioxide gas from the liquid contained in bubbles, the concentration of which, according to literature data, ranges from 30 mg/kg to 70 mg/kg in acidic condensate. However, further development of this idea involves using a series of processes that allow avoiding the release of carbon dioxide into the atmosphere after its extraction from the liquid and redirecting this stream to the methanation process for fuel production. Extraction of impurities from the condensate allows obtaining water, which can be used to replenish the water circuit of the boiler or for the water electrolysis process to obtain hydrogen as a raw material for the carbon dioxide methanation process or as an alternative fuel. Bibl. 18, Fig. 5, Tab. 2.

ANALYSIS OF HYDROCARBON GASES OF MUD VOLCANOES OF THE LOWER KURA TROUGH

Based on the detailed analysis of the existing geological-geophysical material, the distribution area of the mud volcanoes developed in the depression, and the geochemical characteristics of their eruption products were studied. The aim is to determine the gases contained in the wastes thrown by volcanoes onto the earth's surface and to study of distribution along the territory. For this reason, the capacity of methane gas, heavy hydrocarbons, nitrogen and carbon dioxide of erupted materials on the surface was studied. Based on the results obtained during the analysis, the composition of the gases of the mud volcanoes located in the depression consists mostly of methane. The content of methane in the eruptive materials of Agzibir volcano varies from 86.3% to 98.88% (Kalamaddin mud volcano). The average mark of methane gas ranges from 86.6% (Akhtarmaardi) to 91.3% (Harami). In addition, maps were drawn up to determine the distribution of gases in the eruptive materials along the study area. Besides, a map of the location of the Galmaz mud volcano, a geological profile passing through the mud volcano was created. The content of gases emitted into the atmosphere was determined based on the analysis of mud volcano eruptive wastes in the south-west and north-east parts of the Galmaz field. As a result of geological-geophysical studies was determined that the chemical composition of the eruption materials of the Galmaz mud volcano is different. The analysis show that, most of the gases emitted from the volcano to the atmosphere consist of methane (CH4) gas. Content of it is up to 97.42% and more. The content of other gases is relatively small, so heavy hydrocarbons is 0.04%, nitrogen is 0.48%, CO2 is 2.06%. The individual deposits related with mud volcano are mainly massive, structural and tectonically screened types. However, hydrocarbons accumulated within traps are formed oil-gas and gas individual deposits. Keywords: Galmaz field, mud volcano eruption, methane gas content, content of nitrogen, carbon dioxide, crushing zones, heavy hydrocarbons, oil and gas accumulations.

(Invited) Gallium Nitride: An Industry Ready Platform for Scalable Artificial Photosynthesis

In this talk, I will present recent advances of artificial photosynthesis utilizing gallium nitride (GaN), which is the second most produced semiconductors next only to silicon. Through nanoscale, quantum, and catalyst engineering, conventional GaN-based semiconductors can be transformed to be highly efficient and stable photocatalyst materials for a broad range of artificial photosynthesis reactions, including solar water splitting, carbon dioxide reduction, methane oxidation, and nitrogen reduction to ammonia. By growing GaN nanostructures under N-rich conditions, the nonpolar surfaces can be transformed to be gallium oxynitride during harsh photocatalysis reaction, which not only protects the surfaces of the light absorber but leads to significantly enhanced photocatalytic and photoelectrochemical performance. Moreover, we have developed unique photocatalytic processes wherein high efficiency solar hydrogen can be produced utilizing tap water, or seawater, without any wire connection, or electricity input. The demonstration of large-scale solar water splitting systems and the performance will be discussed and reported, together with advances in carbon dioxide and nitrogen reduction to clean chemicals and fuels.

Syngas from Reforming Methane and Carbon Dioxide on Ni@M(SiO2 and CeO2).

The accumulation of greenhouse gasses (CH4 and CO2) results in an increase in the temperature of the atmosphere. The conversion of greenhouse gasses into chemicals and fuels with high added value benefits not only the environment but also energy development. A promising and well-studied process is the reforming of methane, where CH4 and CO2 are converted into syngas (CO and H2). However, catalysts hinder the development of the process. In this paper, we investigate the conversion of CH4 and CO2 into syngas using a thermal conversion method. The catalysis performance was evaluated by reforming methane. Ni-based catalysts were prepared by different methods. All prepared catalysts were characterized (XRD, HRTEM et al.), and the process of reforming carbon dioxide-methane was carried out in a fixed bed reactor under atmospheric pressure and a high temperature. Ni(M) @CeO2 is one of the most popular options due to the role of CeO2. The deposition of coke in Ni-based catalysts was investigated.

Plasma‐Catalytic CO2 Methanation Over Supported Ni–Co Catalysts Prepared by Solution Combustion Synthesis

ABSTRACTIncorporating suitable promoters into nickel‐based catalysts for carbon dioxide methanation proves to be a successful strategy for enhancing catalyst structure, optimizing surface properties, mitigating deactivation, and ultimately boosting catalytic performance. This study focuses on the synthesis of Co‐modified Ni/CaCO3 catalysts using the solution combustion synthesis method. The catalytic activity of the afforded catalysts has been evaluated for CO2 methanation in a dielectric barrier discharge reactor operating at a gaseous hourly space velocity of 11,320 h−1 and an H2:CO2 ratio of 4:1. The catalyst exhibits optimal performance at a Ni:Co ratio of 13:2, achieving a CO2 conversion rate of 57.5% and CH4 selectivity of 92.4%. Characterization techniques such as X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy, programmed temperature‐raising hydrogen reduction, carbon dioxide desorption, and in situ plasma DRIFTS are employed to evaluate the catalysts. The results indicate that the addition of Co to Ni‐based catalysts leads to an increase in moderately basic sites, thereby enhancing the catalytic activity and stability of catalysts for CO2 methanation. Notably, the combination of the plasma and the Ni–Co catalyst offers a novel pathway for CO2 methanation, featuring higher energy efficiency and superior synergistic effects compared to monometallic catalysts.

Influence of Microwave-Assisted Supercritical Carbon Dioxide Treatment on the Pore Structure of Low-Rank Coal.

CO2 injection into coal seams not only enhances coalbed methane (CBM) extraction but also allows for CO2 sequestration. Microwave irradiation is considered to be an effective technology to enhance CBM extraction. In this paper, the effects of microwave irradiation and supercritical CO2 immersion on the pore structure of low-rank coals were investigated by scanning electron microscopy (SEM), mercury-in-pressure (MIP), low-temperature nitrogen adsorption (LTN2GA), and carbon dioxide isothermal adsorption/desorption (CO2IA/D) of coal samples. The results showed that the macropores and micropores of the coal samples were more developed after microwave irradiation. After carbon dioxide immersion, the coal samples showed huge fissures, and the meso- and micropores were reduced. In contrast, microwave-assisted carbon dioxide not only reduced the specific surface area in the meso- and microporous stages and decreased the adsorption sites of methane but also enhanced the pore connectivity in the macroporous stage instead of the appearance of huge fissures. This study illustrates the potential of microwave-assisted supercritical carbon dioxide for enhanced coalbed methane extraction and carbon dioxide sequestration.

Global warming impacts of carbon dioxide, methane, and albedo in an island forest nature reserve

Abstract Forest ecosystems influence climate by sequestering carbon from the atmosphere and by altering the surface energy balance. However, the combined global warming impacts (GWIs), contribution from carbon dioxide (CO2) fluxes, methane (CH4) fluxes, and albedo changes (Δα) remain poorly understood. Here, we reported the combined GWIs of CO2, CH4, and albedo with eddy covariance (EC) measurements during 2020–2022 in a subtropical island forest located in the Nanji Islands National Marine Protected Area in Southern China. We suggested that the island forest acted as a significant carbon sink, with annual CO2 and CH4 fluxes of −548.6 ± 11.1 and −5.67 ± 1.1 g C m−2 yr−1, respectively, while the daily albedo varied within the range of 0.03–0.15. By converting the radiative forcing induced by CH4 and albedo change in the forest to CO2 equivalents, we analyzed the three contributors to the combined GWI. The annual averages GWI of CO2 uptake, CH4 uptake, and Δα were −2 011.6 ± 40.6, −211.3 ± 1.1, and 0.03 ± 4.5 g CO2-eq m−2 yr−1, respectively, with a mean combined GWI of −2 223 ± 40.8 g CO2-eq m−2 yr−1. During 2020–2022, the contributions of CO2 uptake, CH4 uptake, and Δα to the combined GWI were 89.7% to 91.4%, 9.4% to 9.6% and −1.0%–0.9%, respectively. Nanji Island forest had a strong positive effect on climate change mitigation, with CO2 and CH4 uptake greatly enhancing its cooling benefits. Using Pearson correlation and path analysis, we found photosynthetically active radiation, precipitation, soil water content were the primary factors controlling the GWI dynamics, mainly driving the changes in CO2 fluxes. This study provided novel insights into the establishment of the overall evaluation framework for ecosystem-scale GWIs of CO2 and CH4 fluxes, and albedo based on long-term EC measurements in an island forest.

Continuous Biological Ex Situ Methanation of CO2 and H2 in a Novel Inverse Membrane Reactor (IMR)

A promising approach for carbon dioxide (CO2) valorization and storing excess electricity is the biological methanation of hydrogen and carbon dioxide to methane. The primary challenge here is to supply sufficient quantities of dissolved hydrogen. The newly developed Inverse Membrane Reactor (IMR) allows for the spatial separation of the required reactant gases, hydrogen (H2) and carbon dioxide (CO2), and the degassing area for methane (CH4) output through commercially available ultrafiltration membranes, enabling a reactor design as a closed circuit for continuous methane production. In addition, the Inverse Membrane Reactor (IMR) facilitates the utilization of hydraulic pressure to enhance hydrogen (H2) input. One of the process’s advantages is the potential to utilize both carbon dioxide (CO2) from conventional biogas and CO2-rich industrial waste gas streams. An outstanding result from investigating the IMR revealed that, employing the membrane gassing concept, methane concentrations of over 90 vol.% could be consistently achieved through flexible gas input over a one-year test series. Following startup, only three supplemental nutrient additions were required in addition to hydrogen (H2) and carbon dioxide (CO2), which served as energy and carbon sources, respectively. The maximum achieved methane formation rate specific to membrane area was 87.7 LN of methane per m2 of membrane area per day at a product gas composition of 94 vol.% methane, 2 vol.% H2, and 4 vol.% CO2.