High H2 Concentrations Research Articles

PSVII-30 Effect of mineral mixture containing HMTBa in hay-based substrate on methane production.

Abstract In grazing systems, cattle produce a high molar ratio of acetate, resulting in greater methane production and greater energy loss via gas production. Thus, the objective of this study was to evaluate in vitro gas production and methane concentration using a mineral mixture containing 0.4% HMTBa in a Tifton hay-based substrate. The experiment was carried out under anaerobic conditions using ANKOM Gas Pressure Monitor bottles kept at 39 ºC containing artificial saliva, ruminal fluid, and two grams of a substrate from each treatment: (FE) Control, 1.75 g of Tifton hay and 0.25 g of mineral mixture; and (FM) 1.75 g of Tifton hay and 0.25 g of Suplemax mineral mixture (Suplemento Nutrição Animal) containing 0.4% of HMTBa. Duplicate substrates and duplicate blanks were fermented for each treatment in two runs, with a total of four repetitions per treatment. The accumulated pressure resulting from the fermentation was measured automatically over 48 hours using the Gas Monitor software connected to the ANKOM modules of each bottle. The conversion of pressure to gas volume was calculated as follows: Volume (mL) = 2.3932 + 3.4053 × pressure (R2 = 0.9146; n = 1.151). At the end of each run, a gas sample was collected from each bottle to measure methane concentration using gas chromatography. To obtain the methane production for every 100 mL of gas produced, the total volume of methane produced was multiplied by 100 and divided by the total gas production. Data were analyzed in a completely randomized design using analysis of variance (ANOVA) at α = 0.05. Gas production was not affected by the inclusion of HMTBa (P = 0.3938), with an average of 54.14 mL (Table 1). There was a reduction in methane production from 25.41 to 20.05 mL with the addition of HMTBa (P = 0.0034), representing a decrease of 21.09%. There was a tendency to reduce methane production for each 100 mL of gas produced from 46.01 to 37.86 mL (P = 0.0889). Although HMTBa reduces the molar proportion of propionate, it is considered to be one of the main hydrogen users. In environments with a high concentration of H2 (above 1 mmol) and the presence of an anti-methanogen, the most favored path for using hydrogen is acetogenesis, which reduces methane production. Thus, the use of a mineral mixture containing 0.4% HMTBa in a Tifton-hay-based substrate reduced methane production in an in vitro assay.

Geochemistry and origins of hydrogen-containing natural gases in deep Songliao Basin, China: Insights from continental scientific drilling

The different reservoirs in deep Songliao Basin have non-homogeneous lithologies and include multiple layers with a high content of hydrogen gas. The gas composition and stable isotope characteristics vary significantly, but the origin analysis of different gas types has previously been weak. Based on the geochemical parameters of gas samples from different depths and the analysis of geological settings, this research covers the diverse origins of natural gas in different strata. The gas components are mainly methane with a small amount of C2+, and non-hydrocarbon gases, including nitrogen (N2), hydrogen (H2), carbon dioxide (CO2), and helium (He). At greater depth, the carbon isotope of methane becomes heavier, and the hydrogen isotope points to a lacustrine sedimentary environment. With increasing depth, the origins of N2 and CO2 change gradually from a mixture of organic and inorganic to inorganic. The origins of hydrogen gas are complex and include organic sources, water radiolysis, water-rock (Fe2+-containing minerals) reactions, and mantle-derived. The shales of Denglouku and Shahezi Formations, as source rocks, provide the premise for generation and occurrence of organic gas. Furthermore, the deep faults and fluid activities in Basement Formation control the generation and migration of mantle-derived gas. The discovery of a high content of H2 in study area not only reveals the organic and inorganic association of natural-gas generation, but also provides a scientific basis for the exploration of deep hydrogen-rich gas.

Turbulent Flame Speed and Flame Characteristics of Lean Premixed H2-CH4 Flames at Moderate Pressure Levels

Abstract Carbon dioxide emissions in gas turbine power generation can be reduced by adding an increasing amount of hydrogen to the existing natural gas-fueled combustion systems. To enable safe operation, more insight on how H2 addition affects turbulent flame speed and other important flame characteristics is needed. In this work, the investigation of hydrogen addition effects on certain flame properties has been carried out in a high-pressure axial-dump combustor at gas turbine relevant conditions. OH planar laser induced fluorescence (PLIF) was applied to retrieve flame front contours and turbulent flame speed. The results show that as the concentration of hydrogen in the fuel mixture increases, turbulent flame speed and flame characteristics change drastically. Two main regimes can be identified: From 0 to 50% vol. Hydrogen, the turbulent flame speed increases weakly in an almost linear fashion, while from 50% vol. to 100% vol. the trend sharply changes and the higher reactivity of hydrogen, combined with a lower Lewis number, cause thermal-diffusive instability and preferential diffusion effects to become increasingly strong, leading to very high burning rates. The presented results help to understand and to define the relevant modifications that are necessary to successfully operate gas turbine combustor systems with high H2 content fuels.

Experimental study on gas production characteristics of electrolyte of lithium-ion battery under pyrolysis conditions

The fires of lithium-ion batteries are mainly due to the vent gas generated from electrolyte decomposition in the thermal runaway process. The gas production characteristics from lithium-ion battery electrolytes are studied experimentally. Furthermore, the effects of varying ratios of lithium cathode, temperature, and state of charge on the volume of electrolyte gas production, thermal runaway trigger time, gas composition, and gas component content are investigated in this study. The results show that the volume of electrolyte gas production gradually increases with rising temperature, reaching a “turning point” temperature between 180 °C and 210 °C. Above this temperature threshold, the growth rate of gas volume accelerates. The gas composition of the electrolyte is high sensitivity to temperature, with CO2 being the predominant gas followed by H2 and CO. High concentrations of H2 (30.3 mmol) and CO (19.1 mmol) serve as effective indicators for early detection of lithium battery thermal runaway. Approximately 55 % or more of the gas generated in thermal runaway are combustible gases, which is the primary factor leading to fire. The gas production volume at 100 % state of charge is approximately 2.5 times higher than that at 0 state of charge.

Experimental Study on Properties of Syngas, Tar, and Biochar Derived from Different Gasification Methods

Biomass gasification technology is a clean and renewable energy utilization approach. Understanding the evolution of gasification product properties is crucial to achieving carbon neutrality goals. A fixed-bed reactor is employed for the biomass gasification with CO2 in this study. Various methodologies have been conducted to characterize the syngas, tar, and biochar produced from the electric gasification (EG) and microwave gasification (MG) of oak and corn stalk samples at different temperatures. When gasifying the same biomass at the same temperature, the syngas yield of MG is generally 3–7% higher than that of EG, and the difference increases with decreasing temperature. The biochar yield of MG is 3–6% higher than that of EG. EG produces more tar at 600–800 °C. The yield of syngas increases as the gasification temperature rises from 600 to 1000 °C, but that of tar and biochar falls. The syngas mainly comprises H2, CH4, CO, and CO2. MG produces 8–15% higher CO content and 2.5–3.5% higher H2 content than EG. This is due to different heating mechanisms. The net calorific value of syngas increases with temperature, reaching a maximum of 11.61 MJ m−3 at 1000 °C for syngas from corn stalk MG. When the temperature rises from 600 to 1000 °C, more primary tars are converted into polycyclic aromatic hydrocarbons (PAHs). At 900 °C, corn stalk biochar from MG has a maximum specific total pore volume (0.62 cm3 g−1), surface area (525.87 m2 g−1), and average pore diameter (4.18 nm). The intensities of the characteristic peaks of biochar functional groups decrease gradually. The heating method has little effect on the types of functional groups.

Engineered Microbial Nanohybrids for Tumor-Mediated NIR II Photothermal Enhanced Ferroptosis/Cuproptosis and Immunotherapy.

The colon tumor microenvironment has a high concentration of H2 S and glutathione, which is highly immunosuppressive and adverse to multiple therapeutic methodologies such as ferroptosis. Here, an engineered microbial nanohybrid based on Escherichia coli (E. coli) and Cu2 O nanoparticles to specific colon tumor therapy and immunosuppression reversion is reported. The as-prepared E. coli@Cu2 O hybrid can accumulate in tumor sites upon intravenous injection, and Cu2 O nanoparticles convert to Cux S by consuming the endogenous H2 S, which exhibits strong photothermal conversion at near-infrared II (NIR II) biological window. Furthermore, E. coli@Cu2 O is able to induce cellular ferroptosis and cuproptosis through inactivation of glutathione peroxidase 4 and aggregation of dihydrolipoamide S-acetyltransferase, respectively. Photothermal-enhanced ferroptosis/cuproptosis achieved by E. coli@Cu2 O reverses the immunosuppression of colon tumors by triggering dendritic cell maturation (about 30%) and T cell activation (about 50% CD8+ T cells). Concerted with immune checkpoint blockade, the engineered microbial nanohybrid can inhibit the growth of abscopal tumors upon NIR illumination. Overall, the designed microbial nanohybrid can achieve tumor-specific photothermal-enhanced ferroptosis/cuproptosis and immunosuppression reversion, showing promise in precise tumor therapy in future clinical translation.

Hydrogen-diesel dual-fuel combustion sensitivity to fuel injection parameters in a multi-cylinder compression-ignition engine

Adding hydrogen to the intake of a diesel engine offers a near-term route to reducing greenhouse gas emissions from heavy-duty commercial vehicles. Variations in combustion behavior between cylinders can limit the performance and H2 utilization in these engines. This research evaluates the impacts of varying H2 concentrations between cylinders due to the phasing of pulsed fuel injection in the intake manifold, and the potential to optimize the diesel injection strategy for each cylinder to compensate for these effects. The study is conducted using a predictive phenomenological combustion model for H2-diesel combustion within the GT-SUITE™ software environment calibrated and validated using experimental data from a 4-cylinder, 5.2 L engine at three loads and at two different H2 concentrations per load. Predictions of engine and combustion performance were within 5% of the experimental results for key parameters. The validated model is then used to quantify the impacts of varying H2 distribution between cylinders on combustion performance and hardware limitations including peak cylinder pressure, rate of pressure rise, and exhaust temperature. From these results, the diesel injection parameters, including timing and quantity of both pilot and main injections, are optimized for each cylinder to minimize variations in engine performance. The results indicate that cylinder-to-cylinder variations in H2 concentration increased with more rapid H2 injection, due to limited dispersion of H2 between the cylinders. Variations in indicated power approached 13.5% between cylinders, with those with high H2 content encountering a substantial risk of knock and noise. Adjusting the diesel injected mass per cylinder balanced power variations, while adjusting pilot injection timing minimized variations in the rate of pressure rise (dP/dCA). Exhaust temperature and efficiency were most sensitive to the timing of the main diesel injection. Combined, these control approaches reduced diesel fuel consumption and CO2 emission by 5.2 and 6.2%, respectively, where an average 3.8% increase in the engine's indicated efficiency was observed. The optimization findings offer a promising approach for balancing the engine performance when there is unbalanced H2 distribution between the cylinders.

A Comprehensive Review in Microwave Pyrolysis of Biomass, Syngas Production and Utilisation

Lignocellulosic and waste materials, such as sewage sludge, can be broken down into its useful constituents and converted into fuel for engines. This paper investigates microwave pyrolysis to decompose biomass into H2 and CO (syngas), which may be catalysed in the Fischer–Tropsch (F-T) process to liquid biofuels. Using microwave radiation as the heat source for pyrolysis proves to yield large quantities of gas with higher concentrations of H2 and CO compared to conventional heating methods. This is largely due to the energy transfer mechanism of microwaves. Pyrolysis parameters such as temperature (which increases with input power), feedstock type, microwave absorber, and biomass moisture content influence syngas yield. Several papers reviewed for this study showed differing optimal conditions for microwave pyrolysis, all being heavily dependent on the biomass used and its composition. However, all researchers agreed on the thermal efficiency of microwave heating and how its material-selective nature can increase syngas yield. Compared to diesel fuels (while processing a similar efficiency and a higher cetane number), FT fuels and specifically pyrolysis may yield the benefit of reduced nitric oxides (NOx), particulate matter (PM), unburnt hydrocarbons (HC) and carbon monoxide (CO) emissions.

Valorizing the Steel Industry Off-Gases: Proof of Concept and Plantwide Design of an Electrified and Catalyst-Free Reverse Water-Gas-Shift-Based Route to Methanol.

Conversion of steel industry off-gases to value-added chemicals enabled by renewable electricity can significantly reduce the environmental burden of the steelmaking process. Herein, we demonstrate that CO2 reduction by H2, both contained in steel mill off-gases, to form syngas via the reverse water-gas-shift reaction is effectively performed by nanosecond pulsed discharges at atmospheric pressure. The experimental results suggest the following: (i) An optimum interelectrode distance exists, maximizing CO2 conversion. (ii) CO2 conversion at constant SEI follows a nonmonotonic trend with H2 excess. CO2 conversion increases with H2 excess up to H2:CO2 = 3:1 upon shifting the chemical equilibrium. At larger H2:CO2, both gas cooling, promoted by the high H2 content, and hindered CO2 collisions in a highly diluted stream hamper CO2 conversion. (iii) SEI enhances CO2 conversion, but the effect decreases with increasing SEI due to equilibrium limitations. A stoichiometric H2:CO2 feed ratio in the plasma reactor is recommended for higher energy efficiency. Intensifying MeOH productivity via SEI elevation is not advised as a 2-fold SEI increase results only in 17% higher MeOH throughput.

Strong geochemical anomalies following active submarine eruption offshore Mayotte

Submarine volcanic activity releases large amounts of gases and metals in the water column, affecting biogeochemical cycles and ecosystems at a regional and local scale. In 2018, Fani Maoré submarine volcano erupted 50 km offshore Mayotte Island (Comoros Archipelago, Indian Ocean). Active eruptive plumes were observed in May 2019 at and around the summit with acoustic plumes rising 2 km into the water column coupled to strong geochemical anomalies. Between May 2019 and October 2020, three research cruises monitored the eruptive activity. Here, we report spatial and temporal variability of water column chemistry above the volcano, focusing on dissolved gases, trace metal concentrations, and physico-chemical parameters. In May 2019, concentrations above 800 nM in CH4 and H2 were measured throughout the water column, with Total Dissolvable Mn and Total Dissolvable Fe concentrations above 500 nM, and CO2 values of 265 μM. Strong water column acidification was measured (0.6 pH unit) compared to the regional background. From May 2019 to October 2020, we observed a general decrease in gas concentrations, and an evolution of the TDMn/TDFe ratios similar to previously reported values in other submarine volcanic contexts, and consistent with a decrease of the eruptive activity at the volcano. In October 2020, a rebound of high H2 concentrations resulted from new lava flows, which were identified by seafloor observation using deep-towed camera, 5 km further than the volcano summit. During 2 years timespan of our observations (2019–2020), He, CO2 and CH4 concentrations correlate highlighting a magmatic origin of dissolved gases. δ13C-CH4 values of −34‰ vs. vPDB might suggest magma/sediments interaction during the magma ascent, and potential thermal cracking of organic matter, although abiotic methane generation cannot be ruled out given the volcanic context. Weak correlations between H2 and excess of 3He suggest complex processes of H2 from magmatic degassing, lava/seawater interaction, and oxidation processes in the water column. Strong and correlated Fe, Mn and Si water column anomalies are also consistent with fluid-rock reactions induced by acidic fluids rich in magmatic volatiles. Water column acidification appears to be associated with the release of CO2-rich fluids. A year after the main eruptive event, the system seems to be back to steady-state highlighting the buffer capacity and resilience of the seawater column environment.

CO2 plasma gasification of bakelite-based electrical switch waste feedstock

Poor degradability of e-waste causes severe soil and water contamination. In recent times, plasma gasification has been an attractive way of solid waste management towards energy recovery considering the environmental benefits. To reduce the short end-of-life electrical products and net CO2 emissions, the low-grade feed of electrical switch waste (ESW) comprising of bakelite (BAK) is chosen for generating clean syngas through the plasma method using CO2. The influence of the feed rate of solid waste, feed CO2 gas and plasma torch power on the product yield and syngas composition is evaluated. Energy and exergy (2-E) analyses are performed to assess the feasibility of the process. The experiment results indicate a maximum syngas yield of ∼85% at the highest torch power of 1.6 kW, with high concentrations of H2 (24.36 vol%) and CO (43.61 vol%). At low torch power of 0.5 kW, the residual solid yield reaches 24.58%. Considering all the cases, syngas with a medium calorific value of up to 10.20 MJ/m3 is attained. For the optimum feed rate of 40 g/10 min, CO2 flow rate of 0.6 lpm and plasma power of 0.75 kW, the process achieved the highest cold gas and exergy efficiency of 42.33% and 35.99%, respectively. The obtained oil (viscosity = 6.43 cP, density = 0.975 g/ml, pH = 8.01 and LHV = 31.47 MJ/kg) is suitable for applications in combustion, transportation and chemical production after quality upgradation. The solid residue (volatile matter = 11 wt%, fixed carbon = 65.67 wt%, ash = 23.33 wt% and LHV = 15.51 MJ/kg) obtained containing Ba (70.42 wt%), Zn (3.87 wt%), Ti (3.25 wt%), etc. in the ash, can be used for making corrosion coating agents, alloys and paints after recovery. The oil analysis showed the formation of NH3 during the reaction at a high torch power of 1.6 kW. Lastly, the reaction mechanism of plasma gasification for the conversion of ESW into syngas is proposed.

Performance Analysis of Hydrogen Production for a Solid Oxide Fuel Cell System Using a Biogas Dry Reforming Membrane Reactor with Ni and Ni/Cr Catalysts

The present study aims to analyze the performance characteristics of the biogas dry reforming process conducted in a membrane reactor using Ni/Cr catalysts and to compare these characteristics with those obtained using pure Ni catalysts. The effect of the pre-set reaction temperature, the molar ratio of CH4:CO2 and the pressure difference between the reaction chamber and the sweep chamber on the characteristics of biogas dry reforming is analyzed. In the present work, the molar ratio of the supplied CH4:CO2 is varied to 1.5:1, 1:1 and 1:1.5. In this case, CH4:CO2 = 1.5:1 simulates a biogas. The pressure difference between the reaction chamber and the sweep chamber is varied to 0 MPa, 0.010 MPa and 0.020 MPa. The reaction temperature is changed to 400 °C, 500 °C and 600 °C. It is revealed that the highest concentration of H2 is achieved using a Ni/Cr catalyst when the molar ratio of CH4:CO2 is 1.5:1 at the differential pressure of 0.010 MPa and the reaction temperature of 600 °C. Under this condition, the H2 yield, H2 selectivity and thermal efficiency are 12.8%, 17.5% and 174%, respectively. The concentration of the H2 produced using a Ni/Cr catalyst is larger than that produced using a Ni catalyst regardless of the pre-set reaction temperature, the molar ratio of CH4:CO2 and the differential pressure.

Simultaneous Response of Mitochondrial MicroRNAs to Identify Cell Apoptosis with Multiple Responsive Intelligent DNA Biocomputing Nanodevices.

Challenges remained in precisely real-time monitoring of apoptotic molecular events at the subcellular level. Herein, we developed a new type of intelligent DNA biocomputing nanodevices (iDBNs) that responded to mitochondrial microRNA-21 (miR-21) and microRNA-10b (miR-10b) simultaneously which were produced during cell apoptosis. By hybridizing two hairpins (H1 and H2) onto DNA nanospheres (DNSs) that had been previously modified with mitochondria-targeted triphenylphosphine (TPP) motifs, iDBNs were assembled in which two localized catalytic hairpins self-assembly (CHA) reactions occurred upon the co-stimulation of mitochondrial miR-21 and miR-10b to perform AND logic operations, outputting fluorescence resonance energy transfer (FRET) signals for sensitive intracellular imaging during cell apoptosis. Owing to the spatial confinement effects of DNSs, it was discovered that iDBNs had a high efficiency and speed of logic operations by high local concentrations of H1 and H2, making the simultaneous real-time responses of mitochondrial miR-21 and miR-10b reliable and sensitive during cell apoptosis. These results demonstrated that iDBNs were simultaneously responsive to multiple biomarkers, which greatly improved the detection accuracy to identify the cell apoptosis, demonstrating that iDBNs are highly effective and reliable for the diagnosis of major disease and screening of anticancer drugs.

Numerical study of the impact of hydrogen addition, swirl intensity and equivalence ratio on methane-air combustion

Abstract Hydrogen-blended fuel is a promising resource for future generations of gas turbine engines, due to its capability of reducing carbon-based emissions. This paper presents a numerical study to assess hydrogen-enriched combustion in a laboratory-scale burner operating at a high turbulence level and under lean and stoichiometric burning conditions. Moreover, a wide range of H2 (up to 90 %) is used for enriching CH4-air combustion in combination with two different swirl levels. The results show that a high swirl intensity results in shorter flames, due to the increased turbulent intensity, which reduces the flame surface area and uniformness the reacting zone. Besides, increasing swirl intensity further increase flame temperature for a given H2-blended fuel. Overall, the results suggest that high swirl intensity in combination to lean mixtures is favorable when using H2-blended fuel with high H2 concentrations. The simulation results also demonstrate that considering radiation heat loss is influential, as it yields a reduction of the outlet temperature by not less than 100 K, bringing down NO x emissions by half.

Metapangenomic investigation provides insight into niche differentiation of methanogenic populations from the subsurface serpentinizing environment, Samail Ophiolite, Oman.

Serpentinization reactions produce highly reduced waters that have hyperalkaline pH and that can have high concentrations of H2 and CH4. Putatively autotrophic methanogenic archaea have been identified in the subsurface waters of the Samail Ophiolite, Sultanate of Oman, though the strategies to overcome hyperalkaline pH and dissolved inorganic carbon limitation remain to be fully understood. Here, we recovered metagenome assembled genomes (MAGs) and applied a metapangenomic approach to three different Methanobacterium populations to assess habitat-specific functional gene distribution. A Type I population was identified in the fluids with neutral pH, while a Type II and "Mixed" population were identified in the most hyperalkaline fluids (pH 11.63). The core genome of all Methanobacterium populations highlighted potential DNA scavenging techniques to overcome phosphate or nitrogen limitation induced by environmental conditions. With particular emphasis on the Mixed and Type II population found in the most hyperalkaline fluids, the accessory genomes unique to each population reflected adaptation mechanisms suggesting lifestyles that minimize niche overlap. In addition to previously reported metabolic capability to utilize formate as an electron donor and generate intracellular CO2, the Type II population possessed genes relevant to defense against antimicrobials and assimilating potential osmoprotectants to provide cellular stability. The accessory genome of the Mixed population was enriched in genes for multiple glycosyltransferases suggesting reduced energetic costs by adhering to mineral surfaces or to other microorganisms, and fostering a non-motile lifestyle. These results highlight the niche differentiation of distinct Methanobacterium populations to circumvent the challenges of serpentinization impacted fluids through coexistence strategies, supporting our ability to understand controls on methanogenic lifestyles and adaptations within the serpentinizing subsurface fluids of the Samail Ophiolite.

Biomass Combustion in the Helically Coiled Domestic Boiler Combined with the Equilibrium/Chemical Kinetics CFD Approach

In the face of threats related to energy supply and climate change, the use of biomass is gaining importance, particularly in distributed energy systems. Combustion of biomass, including residue biomass, is considered one of the routes to increase the share of renewables in energy generation. The modeling of gaseous phase reactions remains crucial in predicting the combustion behavior of biomass and pollutant emissions. However, their simulation becomes a challenging task due to the computational cost. This paper presents a numerical analysis of the combustion process of a gas mixture released during biomass decomposition in a domestic 25 kW coil-type boiler. Three types of biogenic fuels were taken into consideration. The work aimed at examining the available tools for modeling gas burning, thus the geometry of the system was limited only to the 2D case. The thermodynamic equilibrium composition of pyrolysis gas was determined and implemented in Ansys to simulate the process. The computational results showed the potential of detailed, but reduced, combustion mechanisms of CH4/CO/H2 mixtures in predicting the main process features. The mechanism involving 85 reactions appeared to be more reliable compared to that comprising 77 reactions, particularly for volatiles with higher H2 content, whilst offering an acceptable calculation time. The burning characteristics obtained for volatiles with less CH4 and more H2 are in good agreement with the real operation conditions reported for the boiler.

H2 generated by fermentation in the human gut microbiome influences metabolism and competitive fitness of gut butyrate producers

BackgroundHydrogen gas (H2) is a common product of carbohydrate fermentation in the human gut microbiome and its accumulation can modulate fermentation. Concentrations of colonic H2 vary between individuals, raising the possibility that H2 concentration may be an important factor differentiating individual microbiomes and their metabolites. Butyrate-producing bacteria (butyrogens) in the human gut usually produce some combination of butyrate, lactate, formate, acetate, and H2 in branched fermentation pathways to manage reducing power generated during the oxidation of glucose to acetate and carbon dioxide. We predicted that a high concentration of intestinal H2 would favor the production of butyrate, lactate, and formate by the butyrogens at the expense of acetate, H2, and CO2. Regulation of butyrate production in the human gut is of particular interest due to its role as a mediator of colonic health through anti-inflammatory and anti-carcinogenic properties.ResultsFor butyrogens that contained a hydrogenase, growth under a high H2 atmosphere or in the presence of the hydrogenase inhibitor CO stimulated production of organic fermentation products that accommodate reducing power generated during glycolysis, specifically butyrate, lactate, and formate. Also as expected, production of fermentation products in cultures of Faecalibacterium prausnitzii strain A2-165, which does not contain a hydrogenase, was unaffected by H2 or CO. In a synthetic gut microbial community, addition of the H2-consuming human gut methanogen Methanobrevibacter smithii decreased butyrate production alongside H2 concentration. Consistent with this observation, M. smithii metabolic activity in a large human cohort was associated with decreased fecal butyrate, but only during consumption of a resistant starch dietary supplement, suggesting the effect may be most prominent when H2 production in the gut is especially high. Addition of M. smithii to the synthetic communities also facilitated the growth of E. rectale, resulting in decreased relative competitive fitness of F. prausnitzii.ConclusionsH2 is a regulator of fermentation in the human gut microbiome. In particular, high H2 concentration stimulates production of the anti-inflammatory metabolite butyrate. By consuming H2, gut methanogenesis can decrease butyrate production. These shifts in butyrate production may also impact the competitive fitness of butyrate producers in the gut microbiome.3hTM6nso89x7h1g_xY7TKkVideo

Numerical study on pollutant emissions characteristics and chemical and physical exergy analysis in Mild combustion

This analytical study appraises the emission characteristics of different pollutants such as CO and NOX as well as conducting chemical and physical exergy analyses on conventional and Mild combustion regimes. The RANS turbulence approach and the k-ε RNG model were utilized in this study to simulate turbulence, whereas the eddy dissipation concept (EDC) model and the GRI–Mech 2.11 chemical mechanism were adopted to treat the turbulence-chemistry interaction. This study evaluated local and global pollutant emissions and exergy efficiency along the reacting jet and explored the effects of temperature and chemical species on the physical and chemical exergies in MILD combustion in comparison to conventional combustion. It is found that the overall exergy efficiency of MILD combustion rises by 1, 3, and 4% for oxygen mass fractions of 3, 6, and 9% in hot oxidizer coflow, with the NOx emissions are 81, 72, and 55% lower than conventional combustion, respectively. Chemical exergy is greater than physical exergy near the fuel nozzle due to high CH4 and H2 concentrations. Chemical exergy reduces along the burner due to chemical reactions, while physical exergy increases due to the increased temperature. However, owing to the trade-off between these two exergies along the flame jet, the total exergy approaches a constant value at large distances from the burner. The maximum total exergy occurs at a distance of 0.12 m from the fuel nozzle, with chemical exergy accounting for 83% of the total exergy. In the outlet (0.5 m from the fuel nozzle), chemical exergy accounts only for 30% of the total exergy. It can also be concluded that the exergy is stabilized at a distance of 0.3 m from the nozzle (60% of the domain length). Despite a higher local CO emission in conventional combustion than in MILD combustion, the CO emission substantially decreases at a smaller distance from the nozzle in conventional combustion due to the high O2 concentration.

Techno-economic assessment of sunflower husk pellets treated with waste glycerol for the Bio-Hydrogen production– A Simulation-based case study

Biomass gasification is a renewable and sustainable energy source with high product yield and economic viability. This study presents a conceptual model for producing biohydrogen from sunflower husks pellets and waste glycerol using the Aspen Plus® simulation tool. The study analyzes the effects of temperature, steam to biomass rate, and CaO rate on the product gas. The results show that increasing the gasifier temperature from 600 to 750 °C increases H2 volume percentage to 92%. Optimizing steam to biomass rate and CaO to biomass rate also affects the volume % of H2 gas in the product gas. The study concludes that a CaO rate of 1.8:1 and a steam-to-biomass ratio of 1.75:1 produce high H2 content with a high heating value of gas. The total capital cost incurred for the system is $2.93 × 106, with a total operating cost of $14.58 × 106/yr.

Influence of reduction conditions on the structure-activity relationships of NaNO3-promoted Ni/MgO dual function materials for integrated CO2 capture and methanation

Integrated CO2 capture and utilization (ICCU) represents an innovative concept and technique for reducing industrial carbon emissions. Ni-MgO dual function materials (DFMs) promoted by alkali metal salt (AMS) for integrated CO2 capture and methanation (ICCU-M) is gaining increasing interest. The in-situ methanation performance depends heavily on the high-temperature NiO reduction process, while this might adversely affect CO2 adsorption due to loss of AMS. Herein, we investigated the effects of H2 concentration and reduction temperature on structure–activity relationships of AMS-promoted Ni-MgO DFMs for ICCU-M. The increase in H2 concentration and reduction temperature favors NiO reduction to metallic Ni0 and boosts oxygen vacancy concentration in the DFMs. Both CO2 uptakes and CH4 yield increase with the elevating H2 concentration, and CH4 yield also increases with the increasing reduction temperature, considering the increased metallic Ni0 content and oxygen vacancy concentration. CO2 uptakes of the DFMs decline with the increase in reduction temperature, due to the obvious loss in AMS. The bulk diffusion kinetics in CO2 adsorption stage will be improved under higher H2 concentration and reduction temperature, while the chemisorption kinetics will be weakened at elevating reduction temperature. The methanation kinetics will be enhanced when the DFMs are reduced under higher H2 concentration and temperature. The AMS-NM-100-450 DFMs reduced in 100 %H2 and 450 °C exhibit good ICCU-M performance with high CO2 adsorption capacity and CH4 yield of 6.46 mmol CO2/g and 0.85 mmol CH4/g. The results in this work enlighten that the ICCU-M performance of AMS promoted Ni-MgO DFMs can be tuned by regulating the operating parameters for catalyst reduction.