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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

MgO Nanostructures on Au(111) as Catalysts for Low-Temperature Methane Activation and C-C Coupling

The selective conversion of methane (CH4) under mild conditions remains challenging due to strong C-H bonds and catalyst coking. We systematically investigated sub-monolayer MgO nanostructures on Au(111), where two-dimensional (2D) MgO islands with stable Mg-O-Au interfaces catalyze low-temperature CH4 activation and C-C coupling. Upon CH4 exposure at 300 K, surface-bound CHx and C2Hx intermediates formed and persisted post-evacuation, indicating robust CHx-O-Mg linkages. Temperature-programmed studies revealed that C-H activation and C-C coupling intensify with heat: the CHx signal grew continuously while the C2Hx signal reached a plateau at 400-500 K. O 1s and Mg 2p attenuation confirmed adsorption of the hydrocarbons on MgO. Catalytic tests at 500 K yielded C2H6 (70%) and C2H4 (30%) without coking, underscoring MgO's role as an active catalyst. These results offer new design principles for developing coke-resistant and low-temperature methane upgrading catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Chemical influence of ammonia on suppressing soot formation pathways

There is interest in mixing ammonia (NH3) with hydrocarbons, as this decreases overall CO2 emissions from the fuel mixture when burned. Co-firing NH3 with hydrocarbons like methane (CH4) also enables stable combustion over a larger set of operating conditions in engines and gas turbines than firing only NH3 permits. When NH3 is co-fired with hydrocarbons, the influence of NH3 on soot formation chemistry becomes relevant. In this work, soot concentrations in laminar nonpremixed co-flow flames of NH3/CH4 and N2/CH4 were analyzed using color-ratio pyrometry. The concentrations of combustion species (CH4, CO2, H2O, O2, C2H2, C6H6, HCN) across the different flames were also determined using on-line electron-impact mass spectrometry. The flames were also interrogated with 2D CFD simulations, which employ a detailed chemical mechanism tailored to capturing fuel-nitrogen chemistry. Addition of NH3 to CH4 flames was found to decrease soot concentrations more significantly than N2-addition (Fig. 1). The NH3/CH4 flames were found to have higher flame temperatures than the N2/CH4 flames, implying the suppression of soot afforded by NH3 is due to a chemical influence of NH3, as opposed to thermal or dilution effects. Based on experimental and simulated soot volume fractions and species concentrations, soot formation pathways affected by NH3 are postulated.

10 SYNTHETIC FUELS↗
DOE OSTI2020

Observations of Greenhouse Gas Changes across Summer Frontal Boundaries in the Eastern United States

Our knowledge about synoptic-scale variations of atmospheric CO2 produced by interactions between mid-latitude cyclones and regional-scale surface fluxes remains limited by scarcity of observations. We synthesize observations of greenhouse gases (GHG) with respect to frontal passages to understand how GHG distributions change vertically and horizontally during a synoptic event. We use the airborne in-situ measurements of GHGs collected during the first Atmospheric Carbon and Transport–America (ACT) summer field campaign across three regions of the eastern US. We find that frontal structures are consistently and clearly associated with spatially coherent, significant changes in GHG composition. Warm sector CO2 mole fractions (henceforth, [CO2]) are significantly higher than those in the cold sector. The CO2 frontal differences (5-30 ppm) are largest in the atmospheric boundary layer (ABL) with smaller differences (3-5 ppm) in the free troposphere (FT). Bands of elevated CO2 (5-20 ppm enhancement compared to warm-sector mean [CO2]) repeatedly occurred in the ABL adjacent to the frontal boundary. Analyses of 84 vertical profiles reveal higher [CO2] in the FT than in the ABL in the cold-sector, the opposite pattern in the warm-sector. Average ABL-to-FT [CO2] differences are 12 ppm and -6 ppm in the warm and cold sectors, respectively. The same analysis for CH4 shows higher [CH4] in the ABL than in the FT in both warm and cold sectors with at least 30-ppb higher ABL-to-FT [CH4] differences in the warm-sector than in the cold-sector. The observational analyses presented here define new metrics for model evaluation of GHG transport.

Pal, Sandip↗
DOE OSTI2021

Soil metabolome response to whole-ecosystem warming at the Spruce and Peatland Responses under Changing Environments experiment

In this study, a suite of complementary environmental geochemical analyses, including NMR and gas chromatography-mass spectrometry (GC-MS) analyses of central metabolites, Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) of secondary metabolites, and lipidomics, was used to investigate the influence of organic matter (OM) quality on the heterotrophic microbial mechanisms controlling peatland CO2, CH4, and CO2:CH4 porewater production ratios in response to climate warming. Our investigations leverage the Spruce and Peatland Responses under Changing Environments (SPRUCE) experiment, where air and peat warming were combined in a whole-ecosystem warming treatment. We hypothesized that warming would enhance the production of plant-derived metabolites, resulting in increased labile OM inputs to the surface peat, thereby enhancing microbial activity and greenhouse gas production. Because shallow peat is most susceptible to enhanced warming, increases in labile OM inputs to the surface, in particular, are likely to result in significant changes to CO2 and CH4 dynamics and methanogenic pathways. In support of this hypothesis, significant correlations were observed between metabolites and temperature consistent with increased availability of labile substrates, which may stimulate more rapid turnover of microbial proteins. An increase in the abundance of methanogenic genes in response to the increase in the abundance of labile substrates was accompanied by a shift toward acetoclastic and methylotrophic methanogenesis. Our results suggest that as peatland vegetation trends toward increasing vascular plant cover with warming, we can expect a concomitant shift toward increasingly methanogenic conditions and amplified climate–peatland feedbacks.

Wilson, Rachel M.↗
DOE OSTI2023

Simulation of Methane Oxycombustion in Supercritical Carbon Dioxide

The Allam-Fetvedt Cycle (AFC) offers the potential for electricity generation with minimal or even negative carbon emissions by using oxycombustion in supercritical carbon dioxide (sCO2). Because of the extreme high temperatures and pressures encountered in these systems, simulation of oxycombustion requires use of a complex equation of state such as the modified Soave-Redlich-Kwong (SRK) equation, coupled with equally complex correlations for transport properties. The current work simulates a model combustor using both an ideal gas equation of state and the SRK equation of state. The model combustor features a jet of CH4 mixing with and reacting with O2 in the sCO2 ambient. Two jet configurations are considered: one of pure CH4, and one of CH4 mixed with sCO2. Comparison of results shows that key output properties such as combustor temperature and flow distribution are impacted by the choice of equations of state. Inspection of simulation results shows that mixing and reaction rates, as well as the uniformity of the flow, are impacted by the choice of equation of state. These results show that even though use of a complex equation of state greatly increases the computational costs of these simulations, it is critical to accurately capturing the physics of these systems.

computational fluid dynamics↗
DOE OSTI2025

Climate-carbon feedback tradeoff between Arctic and alpine permafrost under warming

Whether greenhouse gas (GHG) emissions from permafrost will trigger positive climate feedbacks under warming remains unknown. Here, we synthesized the response of growing season carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions to experimentally manipulated warming of ~2°C for permafrost in alpine and Arctic regions. Warming weakened the GHG sink of alpine permafrost, thereby increasing (13%) its global warming potential, but strengthened the GHG sink of Arctic permafrost and decreased (-10%) its global warming potential. When warming caused drying of alpine permafrost soils, the CO2 sink weakened but the CH4 sink increased. In contrast, warming of relatively wet Arctic permafrost increased the CO2 sink and CH4 source. Warming led to much stronger increases of the N2O source in alpine than Arctic permafrost. Although keeping additional warming below 2°C in permafrost regions can avoid the positive permafrost-climate feedback, measures are needed to maintain fragile carbon sink of alpine permafrost ecosystems.

Bao, Tao↗
DOE OSTI2022

Data for: Patel et al. Carbon flux estimates are sensitive to data source: A comparison of field and lab temperature sensitivity data

This dataset contains data and code used for the paper "Carbon flux estimates are sensitive to data source: A comparison of field and lab temperature sensitivity data" [DOI COMING SOON]A large literature exists on mechanisms driving soil production of the greenhouse gases CO2 and CH4. Measurements of these gases’ fluxes are often performed using closed-chamber incubations in the laboratory or in situ, i.e., in the field. Although it is common knowledge that measurements obtained through field studies vs. laboratory incubations can diverge because of the vastly different conditions of these environments, few studies have systematically examined these patterns. It is crucial to understand the magnitude and reasons for any differences, as these data are used to parametrize and benchmark ecosystem- to global-scale models, which are then susceptible to the biases of the source data. Here, we specifically examine how greenhouse gas measurements may be influenced by whether the measurement/incubation was conducted in the field vs. laboratory, focusing on CO2 and CH4 measurements. We use Q10 of greenhouse gas flux (temperature sensitivity) for our analyses, because of the ubiquity of this metric in biological and Earth system sciences and its importance to many modeling frameworks. We predicted that laboratory measurements would be less variable, but also less representative of true field conditions. However, there was greater variability in the Q10 values calculated from lab-based measurements of CO2 fluxes, because lab experiments explore extremes rarely seen in situ, and reflect the physical and chemical disturbances occurring during sampling, transport, and incubation. Overall, respiration Q10 values were significantly greater in laboratory incubations (mean = 4.19) than field measurements (mean = 3.05), with strong influences of incubation temperature and climate region/biome. However, this was in part because field measurements typically represent total respiration (Rs), whereas lab incubations typically represent heterotrophic respiration (Rh), making direct comparisons difficult to interpret. Focusing only on Rh-derived Q10, these values showed almost identical distributions across laboratory (n = 1110) and field (n = 581) experiments, providing strong support for using the former as an experimental proxy for the latter, although we caution that geographic biases in the extant data make this conclusion tentative. Due to a smaller sample size of CH4 Q10 data, we were unable to perform a comparable robust analysis, but we expect similar interactions with soil temperature, moisture, and environmental/climatic variables. Our results here suggest the need for more concerted efforts to document and standardize these data, including sample and site metadata. This dataset contains a compressed (.zip) archive of the data and R scripts used for this manuscript. The dataset includes files in .csv format, which can be accessed and processed using MS Excel or R. This archive can also be accessed on GitHub at https://github.com/kaizadp/field_lab_q10 (DOI: 10.5281/zenodo.7106554).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Carbon flux measurements from chambers collected between July to October 2022 at Old Woman Creek, Huron, Ohio.

This dataset contains carbon dioxide and methane flux measurements collected via chamber sampling at Old Woman Creek National Estuarine Research Reserve in Huron, OH. These data were generated to understand temporal and vegetation patterns associated with wetland carbon cycling. Specifically, this dataset intends to answer how carbon dioxide and methane fluxes change monthly and hourly across sites with vegetation and without vegetation. Data includes chamber measurements that were measured in both sites with vegetation and without vegetation and that were collected hourly, for 12 hours, and monthly, for four months. The file soilrespiration_data.csv contains these data, and the metadata file (soilrespiration_chammetadata.csv) and location metadata file (soilrespiration_locationmetadata.csv) have information on locations where the chambers were placed and sampled in the wetland. Data processing was done on raw methane fluxes (Flux_CH4) to remove the influence of ebullition (Flux_CH4_ebullition) to get a diffusive flux (Flux_CH4_diffusive).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

SPRUCE Methane Transport in Plants at S1 Bog, Marcell Experimental Forest, Minnesota, 2017-2019

This data set contains measurements of methane (CH4) transport by plants (both ground-layer and trees) and diffusion, as well as whole-plot emissions, taken in September 2018 and June 2019 in S1 Bog outside of the SPRUCE (Spruce and Peatland Responses Under Changing Environments) experimental enclosures. Additionally, CH4 and carbon dioxide (CO2) stable isotope data in porewater and atmospheric emissions were taken in July 2017 in the SPRUCE enclosures to explore the relative magnitude of CH4 oxidation. Episodic ebullition rates for S1 Bog are taken from Gill et al. (2017). Methane transport is an important component of many ecosystem models of peatlands. The results were compared to two methane models that have been developed for the SPRUCE project, ELM-SPRUCE (Earth Land Model) and TECO_SPRUCE (Terrestrial ECOsystem model). This dataset contains six data files in comma separate (.csv) format. Additional metadata are provided: six data dictionaries and a file-level metadata file in comma separate (.csv) format and a user guide in PDF (*.pdf) format.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Data from: Lowland Tropical Forests Remain a Methane Sink Under Warming and Long-Term Hurricane Disturbance Recovery

The repository folder contains spreadsheets and script for soil greenhouse gas (GHG) fluxes, soil moisture, soil temperature, air temperature, and precipitation measurements collected from the Tropical Responses to Altered Climate Experiment (TRACE) at the Sabana Research Field Station, El Yunque National Forest (USDA Forest Service; 18°19′28.74″ N, 65°43′50.09″ W) — an open-air field warming experiment located in a lowland tropical forest in Puerto Rico within the Luquillo Experimental Forest (LEF) — six to seven years after Hurricanes Irma and Maria (2017). All spreadsheets for soil and air microclimate data, as well as soil greenhouse gas data, are included as csv files. Air temperature data are also included as Excel spreadsheets (.xlsx). The script is built in R Studio, which is the only software required to run data analysis. This dataset is associated with the manuscript “Larocca Conte G ; Zuvela L ; Cruz-Pérez R ; Barreto-Vélez T ; Becerra-Santillan N ; Campbell S ; Chu H ; Dam T ; Grullón-Penkova I ; Kleit M ; Ortiz-Iglesias D ; Rubio-Lebrón L ; Cavaleri M ; Reed S ; Sihi D ; Wood T ; O'Connell C., 2026. Lowland Tropical Forests Remain a Methane Sink Under Warming and Long-Term Hurricane Disturbance Recovery. Agricultural and Forest Meteorology. In review". The dataset was used to test the effect of warming on soil CH4 dynamics following long-term legacy effects of hurricane disturbance. The dataset includes: - An overall README file in word and pdf format describing methodology and spreadsheets’ structure. - Continuous measurements of soil temperature and moisture from January 2023 to July 2024 measured with Campbell CS655 probes (“TRACE_soil_temperature_and_moisture_2023_cleaned(in).csv” and “TRACE_soil_temperature_and_moisture_2024_cleaned. csv”). - Air temperature data measured with a HOBO MX23O1A data logger (“Hobo air temperature 2023 Sep 2024” and “Hobo air temperature 2023 Sep 2024” – “CSV FILES folders”). - Precipitation data from a nearby weather tower downloaded from González et al. (2025; “sabana_2020-2025.csv”). - Soil CH4 and CO2 effluxes measured intermittently in two summer campaigns (June – August 2023 and June – July 2024) with a LI-COR 8200-01S Portable Smart Chamber coupled with a LI-COR LI-7810 CH4/ CO2/H2O Trace Gas Analyzer (“23_24COMBO2.0.csv”). - R markdown script for data analysis (“Trace new_PLOTS.Rmd”).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Carbon flux measurements from chambers collected between April to October 2023 at Old Woman Creek, Huron, Ohio

This dataset contains carbon dioxide and methane gas flux measurements collected via chamber sampling at Old Woman Creek National Estuarine Research Reserve in Huron, OH. These data were generated to understand temporal and vegetation patterns associated with wetland carbon cycling. Specifically, this dataset intends to answer how carbon dioxide and methane fluxes change monthly and hourly across sites with vegetation and without vegetation. Data includes chamber measurements that were measured in both sites with vegetation and without vegetation and that were collected hourly (7 AM to 7 PM or 5 AM to 10 PM and monthly (April to October). The file soilrespiration_data23.csv contains these data, and the metadata file (soilrespiration_chammetadata23.csv) and location metadata file (soilrespiration_locationmetadata23.csv) have information on locations where the chambers were placed and sampled in the wetland. Data processing was done on raw methane fluxes (Flux_CH4) to remove the influence of ebullition (Flux_CH4_ebullition) to get a diffusive flux (Flux_CH4_diffusive).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on NiB18(H11C2)2 by Materials Project

NiB12(CH4)4(BH)6 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of twenty-four boranediylradical molecules and four NiB12(CH4)4 clusters. In each NiB12(CH4)4 cluster, Ni2+ is bonded in a 9-coordinate geometry to six B+0.33- and three C4- atoms. There are a spread of Ni–B bond distances ranging from 2.08–2.31 Å. There are a spread of Ni–C bond distances ranging from 1.98–2.11 Å. There are twelve inequivalent B+0.33- sites. In the first B+0.33- site, B+0.33- is bonded in a single-bond geometry to one Ni2+ and one H+0.91+ atom. The B–H bond length is 1.18 Å. In the second B+0.33- site, B+0.33- is bonded in a distorted water-like geometry to one C4- and one H+0.91+ atom. The B–C bond length is 1.72 Å. The B–H bond length is 1.20 Å. In the third B+0.33- site, B+0.33- is bonded in a distorted bent 120 degrees geometry to one C4- and one H+0.91+ atom. The B–C bond length is 1.59 Å. The B–H bond length is 1.19 Å. In the fourth B+0.33- site, B+0.33- is bonded in a distorted bent 120 degrees geometry to one Ni2+, one C4-, and one H+0.91+ atom. The B–C bond length is 1.66 Å. The B–H bond length is 1.19 Å. In the fifth B+0.33- site, B+0.33- is bonded in a distorted single-bond geometry to one Ni2+ and one H+0.91+ atom. The B–H bond length is 1.19 Å. In the sixth B+0.33- site, B+0.33- is bonded in a distorted bent 120 degrees geometry to one Ni2+, one C4-, and one H+0.91+ atom. The B–C bond length is 1.70 Å. The B–H bond length is 1.19 Å. In the seventh B+0.33- site, B+0.33- is bonded in a distorted bent 120 degrees geometry to one C4- and one H+0.91+ atom. The B–C bond length is 1.69 Å. The B–H bond length is 1.19 Å. In the eighth B+0.33- site, B+0.33- is bonded in a 3-coordinate geometry to two C4- and one H+0.91+ atom. There is one shorter (1.70 Å) and one longer (1.72 Å) B–C bond length. The B–H bond length is 1.19 Å. In the ninth B+0.33- site, B+0.33- is bonded in a distorted bent 120 degrees geometry to one Ni2+, one C4-, and one H+0.91+ atom. The B–C bond length is 1.70 Å. The B–H bond length is 1.19 Å. In the tenth B+0.33- site, B+0.33- is bonded in a single-bond geometry to one Ni2+ and one H+0.91+ atom. The B–H bond length is 1.19 Å. In the eleventh B+0.33- site, B+0.33- is bonded in a distorted bent 120 degrees geometry to one C4- and one H+0.91+ atom. The B–C bond length is 1.62 Å. The B–H bond length is 1.19 Å. In the twelfth B+0.33- site, B+0.33- is bonded in a distorted bent 120 degrees geometry to two C4- atoms. There is one shorter (1.60 Å) and one longer (1.70 Å) B–C bond length. There are four inequivalent C4- sites. In the first C4- site, C4- is bonded in a 4-coordinate geometry to two B+0.33- and two H+0.91+ atoms. There is one shorter (1.09 Å) and one longer (1.11 Å) C–H bond length. In the second C4- site, C4- is bonded in a 1-coordinate geometry to one Ni2+, three B+0.33-, and one H+0.91+ atom. The C–H bond length is 1.09 Å. In the third C4- site, C4- is bonded in a 1-coordinate geometry to one Ni2+, three B+0.33-, one C4-, and one H+0.91+ atom. The C–C bond length is 1.61 Å. The C–H bond length is 1.09 Å. In the fourth C4- site, C4- is bonded in a 1-coordinate geometry to one Ni2+, three B+0.33-, one C4-, and one H+0.91+ atom. The C–H bond length is 1.08 Å. There are sixteen inequivalent H+0.91+ sites. In the first H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the second H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the third H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the fourth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the fifth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the sixth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one C4- atom. In the seventh H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one C4- atom. In the eighth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one C4- atom. In the ninth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the tenth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the eleventh H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the twelfth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the thirteenth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the fourteenth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one B+0.33- atom. In the fifteenth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one C4- atom. In the sixteenth H+0.91+ site, H+0.91+ is bonded in a single-bond geometry to one C4- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on B10H33C10I by Materials Project

B3(CH4)2(BH)4(CH2)4(CH3)2B3C2H7I crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of eight boranediylradical molecules, eight methane molecules, four methane molecules, two B3(CH4)2 clusters, and two B3C2H7I clusters. In each B3(CH4)2 cluster, there are three inequivalent B+1.20+ sites. In the first B+1.20+ site, B+1.20+ is bonded in a water-like geometry to two H+0.88+ atoms. There is one shorter (1.19 Å) and one longer (1.31 Å) B–H bond length. In the second B+1.20+ site, B+1.20+ is bonded in a trigonal non-coplanar geometry to one C4- and two H+0.88+ atoms. The B–C bond length is 1.59 Å. There is one shorter (1.37 Å) and one longer (1.38 Å) B–H bond length. In the third B+1.20+ site, B+1.20+ is bonded in a water-like geometry to two H+0.88+ atoms. There is one shorter (1.19 Å) and one longer (1.31 Å) B–H bond length. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded in a 4-coordinate geometry to one B+1.20+, one C4-, and two H+0.88+ atoms. The C–C bond length is 1.54 Å. There is one shorter (1.10 Å) and one longer (1.11 Å) C–H bond length. In the second C4- site, C4- is bonded in a distorted water-like geometry to one C4- and two equivalent H+0.88+ atoms. There is one shorter (1.10 Å) and one longer (1.11 Å) C–H bond length. There are seven inequivalent H+0.88+ sites. In the first H+0.88+ site, H+0.88+ is bonded in a single-bond geometry to one C4- atom. In the second H+0.88+ site, H+0.88+ is bonded in a single-bond geometry to one B+1.20+ atom. In the third H+0.88+ site, H+0.88+ is bonded in a single-bond geometry to one C4- atom. In the fourth H+0.88+ site, H+0.88+ is bonded in a single-bond geometry to one B+1.20+ atom. In the fifth H+0.88+ site, H+0.88+ is bonded in an L-shaped geometry to two B+1.20+ atoms. In the sixth H+0.88+ site, H+0.88+ is bonded in an L-shaped geometry to two B+1.20+ atoms. In the seventh H+0.88+ site, H+0.88+ is bonded in a single-bond geometry to one C4- atom. The H–C bond length is 1.10 Å. In each B3C2H7I cluster, there are three inequivalent B+1.20+ sites. In the first B+1.20+ site, B+1.20+ is bonded in a water-like geometry to one H+0.88+ and one I1- atom. The B–H bond length is 1.31 Å. The B–I bond length is 2.19 Å. In the second B+1.20+ site, B+1.20+ is bonded in a trigonal non-coplanar geometry to one C4- and two H+0.88+ atoms. The B–C bond length is 1.58 Å. There is one shorter (1.37 Å) and one longer (1.39 Å) B–H bond length. In the third B+1.20+ site, B+1.20+ is bonded in a water-like geometry to two H+0.88+ atoms. There is one shorter (1.19 Å) and one longer (1.31 Å) B–H bond length. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded in a 4-coordinate geometry to one B+1.20+, one C4-, and two H+0.88+ atoms. The C–C bond length is 1.54 Å. Both C–H bond lengths are 1.10 Å. In the second C4- site, C4- is bonded in a water-like geometry to one C4- and two H+0.88+ atoms. The C–H bond length is 1.11 Å. There are seven inequivalent H+0.88+ sites. In the first H+0.88+ site, H+0.88+ is bonded in a single-bond geometry to one B+1.20+ atom. In the second H+0.88+ site, H+0.88+ is bonded in an L-shaped geometry to two B+1.20+ atoms. In the third H+0.88+ site, H+0.88+ is bonded in an L-shaped geometry to two B+1.20+ atoms. In the fourth H+0.88+ site, H+0.88+ is bonded in a single-bond geometry to one C4- atom. In the fifth H+0.88+ site, H+0.88+ is bonded in a single-bond geometry to one C4- atom. In the sixth H+0.88+ site, H+0.88+ is bonded in a single-bond geometry to one C4- atom. In the seventh H+0.88+ site, H+0.88+ is bonded in a single-bond geometry to one C4- atom. I1- is bonded in a single-bond geometry to one B+1.20+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Catalytic Reduction of Residual Oxygen for the Purification of Carbon Dioxide Streams from Pressurized Oxy-Combustors

Pressurized oxy-combustion (OC) is regarded as an energy-efficient alternative to atmospheric OC. To utilize the captured carbon dioxide (CO2) from pressurized OC for enhanced oil recovery or carbon storage in geological formations, the CO2 product stream must meet the required purity specifications. One major impurity in OC flue gases is residual O2 (e.g., 3 vol%). In this study, a catalytic approach has been investigated to remove the residual O2 through a reduction reaction with injected methane (CH4) in a reverse-flow fixed-bed (RFFB) reactor. The performance was tested for a supported copper (Cu)-based catalyst synthesized by incipient wetness impregnation and a cobalt-manganese (CoMn) oxide catalyst synthesized by a coprecipitation method. A commercial Cu-based catalyst was also studied as the reference. Experimental results revealed that under the reverse-flow operation, the temperature profiles in the reactor were symmetrical on both sides of the catalyst zone and were more homogenous than those under the conventional one-direction-flow operation. Among the tested catalysts, the CoMn catalyst was the most reactive for promoting the reduction of O2 with CH4, able to attain >95% O2 removal at 475 °C and a gas hourly space velocity (GHSV) of 18,000 h-1 with a feed gas containing 3 vol% O2. Under all experiments, the concentrations of carbon monoxide (CO) were lower than 30 ppmv in the effluent gas streams. The reaction between O2 and CH4 could be depicted by using the Mars–van Krevelen redox mechanism based on a two-step reduction–oxidation reaction pathway.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Geochemical and Microbial Dynamics of Hydrogen in a Methane Storage Reservoir

Hydrogen has been identified as a flexible energy carrier with zero or negative emission across multiple energy systems, and existing natural gas infrastructure could be leveraged if hydrogen gas (H2) was blended with methane (CH4). For example, subsurface methane storage reservoirs could be slightly modified to also store hydrogen if a methane/hydrogen blend were injected. However, the compatibility of methane storage reservoirs to include H2 injection has not been fully demonstrated, and this could lead to geochemical and microbiological reactions that alter the reservoir and stored gas content. It is essential that we understand the impact of H2 gas on the biogeochemistry of subsurface storage reservoirs before deploying large-scale H2-CH4 storage, We collected produced fluid from two separate methane storage reservoirs in the Southwestern US. First, we completed a baseline analysis of the biogeochemistry through qPCR, 16S rRNA sequencing, metagenomic sequencing, and geochemical analysis. Each reservoir was found to have unique geochemical conditions and a unique microbial community structure, with Site 1 having a higher TDS and an abundance of Shewanella and Site 2 having a lower TDS and high abundance of Eubacterium and Acetobacterium. Next, we ran a series of high pressure, high temperature reactors under hydrogen storage conditions with the biological sample from one of the storage reservoirs and a 20% H2-80% CH4 gas blend for up to 7 days. Our results show a decrease of hydrogen by 5% in reactors as early as 1-3 days. Previous hydrogen storage work has linked subsurface microorganisms with methanogenesis hydrogen sulfide production, acid production, and microbial corrosion. Our results show minimal change in the fluid chemistry, with the exception of a decrease in dissolved sulfate concentrations. Taxonomic sequencing demonstrated the presence of microorganisms capable of iron redox, acid generation, and hydrogen sulfide production throughout the reactors, suggesting microbial hydrogen consumption may occur through various metabolic pathways. This work demonstrates that site-specific geochemistry and microbiology may impact the efficiency of hydrogen storage in methane storage reservoirs.

environmental microbiology↗
DOE OSTI2025

Potential Challenges of HyBlend Storage in a Methane Reservoir Located in Southwestern United States

Hydrogen has been identified as a flexible energy carrier with zero or negative emissions across multiple energy systems. It is possible to utilize hydrogen by storing Hyblend, or hydrogen gas blended with methane, in existing natural gas infrastructure. However, the compatibility of adapting the current CH4 storage strategies to include H2 injection has not been fully demonstrated. It is essential that we understand the impact of H2 gas on the naturally occurring microbial community of subsurface storage reservoirs before deploying large-scale H2-CH4 storage. We designed a series of experiments that allowed us to identify potential geochemical and microbial challenges of HyBlend Storage in existing methane reservoirs. First, we collected and characterized field fluid samples from a methane reservoir located in southwestern United States. Next, we used these field fluid samples to complete a series of short-term reactor experiments at reservoir conditions (80 °C and ~1,000 psi) for a natural gas (100% CH4) and HyBlend(80% CH4/20% H2) storage environment to measure the transformation of gas content. We conducted both biotic and abiotic (sterilized) measurements to accurately understand and decouple abiotic and microbially driven processes. Overall, we found that our field sample was characterized by a diverse microbial community with the metabolic capacity for sulfur reduction, iron reduction, and acetogenesis. Across our reactors, there was minimal change in geochemistry.

hydrogen storage↗
DOE OSTI2025

SPRUCE Redox-Active Subsurface Organic Matter, Marcell Experimental Forest, Minnesota, 2023

This dataset contains measurements that report on the effects of the SPRUCE experimental treatments on redox-active organic matter (RAOM) reduction (Valenzuela and Cervantes, 2021). Measurements occurred at the SPRUCE Experiment site in the Marcell Experimental Forest in northern Minnesota, USA. This work is also a follow-up to Rush et al. (2021a) which investigated effects of temperature on RAOM reduction after two years of experimental warming (Rush et al. 2021b). This follow-up dataset addresses two main questions; (i) How does warming and elevated carbon dioxide (CO2) directly affect in situ RAOM reduction, and subsequent methane (CH4) and CO2 production, across the peat depth profile? and (ii) How has long-term warming and elevated CO2 changed the total RAOM pool, and subsequent CH4 and CO2 production, across the peat depth profile? This dataset reports electron shuttling capacity (a proxy for RAOM reduction; Keller, and Takagi, 2013) and carbon dioxide (CO2) and methane (CH4) concentrations both in one-week in situ incubations (2023-05-31 to 2023-08-01) and 42-day laboratory incubations from peat collected in 2023 (2023-05-31 to 2023-06-26). Laboratory incubations also measured acetate concentrations. The 2023 laboratory incubations were also compared with laboratory incubations conducted on peat collected in 2016 (Rush et al. 2021b). This dataset contains three data files in comma-separate (.csv) format. Additional metadata are provided: three data dictionaries and a file-level metadata file in comma separate (.csv) format and a user guide in PDF (*.pdf) format.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Quantification of oil and gas methane emissions in the Delaware and Marcellus basins using a network of continuous tower-based measurements

Abstract. According to the United States Environmental Protection Agency (US EPA), emissions from oil and gas infrastructure contribute 30 % of all anthropogenic methane (CH4) emissions in the US. Studies in the last decade have shown emissions from this sector to be substantially larger than bottom-up assessments, including the EPA inventory, highlighting both the increased importance of methane emissions from the oil and gas sector in terms of their overall climatological impact and the need for independent monitoring of these emissions. In this study we present continuous monitoring of regional methane emissions from two oil and gas basins using tower-based observing networks. Continuous methane measurements were taken at four tower sites in the northeastern Marcellus basin from May 2015 through December 2016 and five tower sites in the Delaware basin in the western Permian from March 2020 through April 2022. These measurements, an atmospheric transport model, and prior emission fields are combined using an atmospheric inversion to estimate monthly methane emissions in the two regions. This study finds the mean overall emission rate from the Delaware basin during the measurement period to be 146–210 Mg CH4 h−1 (energy-normalized loss rate of 1.1 %–1.5 %, gas-normalized rate of 2.5 %–3.5 %). Strong temporal variability in the emissions was present, with the lowest emission rates occurring during the onset of the COVID-19 pandemic. Additionally, a synthetic model–data experiment performed using the Delaware tower network shows that the presence of intermittent sources is not a significant source of uncertainty in monthly quantification of the mean emission rate. In the Marcellus, this study finds the overall mean emission rate to be 19–28 Mg CH4 h−1 (gas-normalized loss rate of 0.30 %–0.45 %), with relative consistency in the emission rate over time. These totals align with aircraft top-down estimates from the same time periods. In both basins, the tower network was able to constrain monthly flux estimates within ±20 % uncertainty in the Delaware and ±24 % uncertainty in the Marcellus. The results from this study demonstrate the ability to monitor emissions continuously and detect changes in the emissions field, even in a basin with relatively low emissions and complex background conditions.

54 ENVIRONMENTAL SCIENCES↗