Mol Of Methane Research Articles

Sewage-water treatment with bio-energy production and carbon capture and storage

Typical large-scale sewage-water treatments consume energy, occupy space and are unprofitable. This work evaluates a conceivable two-staged sewage-water treatment at 40,000 m3/d of sewage-water with sewage-sludge (totaling 10kgCOD/m3) that becomes a profitable bioenergy producer exporting reusable water and electricity, while promoting carbon capture. The first stage comprises microbial anaerobic digesters reducing the chemical oxygen demand (COD) by 95% and producing 60%mol methane biogas. The effluent waters enter the subsequent aerobic stage comprising microbial air-fed digesters that extend COD reduction to 99.7%. To simulate the process, up-to-date anaerobic/aerobic digester models were implemented. A biogas-combined-cycle power plant with/without post-combustion carbon capture is designed to match the biogas production, supplying electricity to the process and to the grid. Results comprehend electricity exportation of 13.21 MW (7.92 kWh/tReusable-Water) with -9.957tCO2/h of negative carbon emission (-0.6 kgCO2-Emitted/kgCOD-Removed). The biogas-combined-cycle without carbon capture achieves 21.08 MW of power exportation, while a 37.3% energy penalty arises if carbon capture is implemented. Configurations with/without carbon capture reach feasibility at 125 USD/MWh of electricity price, with respective net present values of 6.86 and 85.07 MMUSD and respective payback-times of 39 and 12 years. These results demonstrate that large-scale sewage-water treatment coupled to biogas-fired combined-cycles and carbon capture can achieve economically feasible bioenergy production with negative carbon emissions.

Effects of methane processing strategy on fuel composition, electrical and thermal efficiency of solid oxide fuel cell

Natural gas is a cheap and abundant fuel for solid oxide fuel cell (SOFC), generally integrating the SOFC system with methane pre-treating system for improving the stability of SOFC. In this paper, the accurate effects of methane processing strategy on fuel composition, electrical efficiency and thermal efficiency of SOFC are investigated based on the thermodynamic equilibrium. Steam reforming of methane is an endothermic process and can produce 3 mol of H2 and 1 mol of CO from 1 mol of methane, and thus the electrical efficiency of SOFC is high at the same O/C ratio and equivalent fuel utilization, whereas the thermal efficiency is low. On the contrary, partial oxidation of methane is an exothermal process and only produces 2 mol of H2 and 1 mol of CO from 1 mol of methane, and thus the electrical efficiency of SOFC is low at the same O/C ratio and equivalent fuel utilization, whereas the thermal efficiency is high. When the O/C ratio is 1.5, the electrical efficiency of SOFC is 55.3% for steam reforming of methane, while 32.7% for partial oxidation of methane. High electrical efficiency of SOFC can be achieved and carbon deposition can be depressed by selecting suitable O/C ratio from methane pretreatment according to the accurate calculation and analysis of effects of different methane processing strategies on the electrical efficiency and thermal efficiency of SOFC.

The effect of fine droplets on laminar propagation speed of a strained acetone-methane flame: Experiment and simulations

In this study, we investigate the effect of the presence of fuel droplets, their size and concentration, on stretched laminar flame speeds. We consider premixed strained methane/air mixtures, with the addition of small acetone droplets, and compare the flame velocity field behaviour to that of the fully vaporized mixture. An impinging stagnation flame configuration is used, to which a narrowly distributed polydisperse mist of acetone droplets is added. Total acetone molar concentrations between 9% and 20% per mole of methane are used, corresponding to 18.6% and 41.4% of the total fuel energy. The Sauter Mean Diameter (SMD) of acetone droplets is varied from 1.0 to 4.7 μm by carefully tuning the air flow rate passing through an atomizer. The droplet size distribution is characterized by a Phase Doppler Anamometry (PDA) system at the outlet of the burner. The flame propagation speed is measured using Particle Image Velocimetry (PIV) for overall equivalence ratios ranging from 0.8 to 1.4 at various strain rates, and the result is compared with a reference case in which acetone was fully vaporized. Unlike the fully vaporized flame, a two-stage reaction flame structure is observed for all droplet cases: a blue premixed flame front followed by a reddish luminous zone. Comparison of the results between gas-only and droplet-laden cases shows that the mean reference burning velocity of the mixture is significantly enhanced when droplets are present under rich cases, whereas the opposite is true for stoichiometric and lean cases. The mean droplet size also changes the relationship between flame speed and strain rate, especially for rich cases. The result suggests that with typical conditions found in laminar strained flames, even for the finest droplets that may have been vaporized before reaching the flame front, the resulting inhomogeneities may lead the flame to behaves differently from the well-premixed gaseous counterpart. Simulations at similar conditions are performed using a two-phase counterflow flame model to compare with experimental data. Model results of reference velocities do not compare well with observations, and the possible reasons for this behaviour are discussed, including the difficulties in determining the pre-vaporization process and thus the boundary conditions, as well as the fidelity of the current point-source based 1D model.

Study of biogas generation from guinea pig excretions in discontinuous and Taiwanese biodigesters at elevations above 2,500 masl

The study was carried out to find out if it is feasible to use guinea pig excretions for the generation of biogas as an alternative energy source at altitudes above 2,500 meters above sea level. Two types of biodigesters were investigated, one discontinuous and the other Taiwanese. The biogas was subjected to a gas chromatography analysis, which showed the concentration in weight and moles of CO2, methane, nitrogen and water, relative density, molecular weight and caloric value. The gas from the discontinuous biodigester was the one with the best results, since its composition had 50.10 % mol of methane.

Visible-Light-Driven Methane Conversion with Oxygen Enabled by Atomically Precise Nickel Catalyst

It remains an extreme challenge to activate thermodynamically unfavorable, chemically inert methane molecules under mild conditions. Herein, we report a molecular-like nickel-thiolate hexameric clu...

Efficient conversion of methane into power via microchanneled solid oxide fuel cells

Methane-fueled solid oxide fuel cells (SOFCs) are promising to achieve high energy conversion efficiency while no study focuses on the conversion efficiency of methane into power, which is greatly restrained by gas diffusion within anode supports. This study employs microchanneled anode supports to provide fast gas diffusion pathway. To confirm the advantage, the anodes with half-channels and without channels are also used for comparison. The microchannel structure increases the maximum power density up to 2.5 times because of diminishing or eliminating concentration polarization within anode supports and improving catalyst coating over anode internal surface. As a compromise of fuel utilization and power output, methane conversion efficiency is defined as power output per mol methane input in feeding gas to compare with the reported results, and the microchanneled SOFCs achieve the record high methane conversion efficiency.

Reduction of SnO2 by a Mixed Gas of Methane and Hydrogen

We investigate the reduction of SnO2 and the generation of syngas(H2, CO) using methane(CH4) and hydrogen(H2) or a mixed gas of methane and hydrogen as a reducing gas. When methane is used as a reducing gas, carbon is formed by the decomposition of methane on the reduced Sn surface, and the amount of generated carbon increases as the amount and time of the supply of methane increases. However, when hydrogen is used as a reducing gas, carbon is not generated. High purity Sn of 99.8 % and a high recovery rate of Sn of 93 % are obtained under all conditions. The effects of reducing gas species and the gas mixing ratio on the purity and recovery of Sn are not significantly different, but hydrogen is somewhat more effective in increasing the purity and recovery rate of Sn than methane. When 1 mole of methane and 1 mole of hydrogen are mixed, a product gas with an H2/CO value of 2, which is known to be most useful as syngas, is obtained.

Investigation of the influence of polyelectrolytes hydrodynamic properties on the hydrateformation process

One of the most perspective non-traditional sources of hydrocarbon raw materials and energy is gas hydrates (GH), which stimulates their large-scale study in many laboratories and scientific centers around the world. The interest in the GH is related to the possibility of their industrial application. The use of technologies for storage and transportation of natural gas in the form of GH requires fundamental kinetic studies of the hydration process at atmospheric pressure in the presence of chemical impurities (catalysts, surfactants, etc.). During the research, an increase in the rate of gas hydrates formation was discovered at the expense of activated impurities and composite compounds obtained on their basis, which lead to changes in the hydrochemical and hydrodynamical modes of systems. It was established that the process of GH formation occurs due to the binding of methane macromolecules and other chemical impurities, which contribute to increase the number of moles of gaseous methane, due to the flow of exchange processes between the polymer matrix and water soluble salts, as well as a result of the change in the hydrodynamics of the water system. The purpose of this work is to investigate the effect of polyelectrolytes solutions hydrodynamic properties on the GH formation. We used a number of ionenes based on polymeric quaternary ammonium salts, side aliphatic radicals of different lengths contained in the acyl fragment.

Early Mars serpentinization‐derived CH4 reservoirs, H2‐induced warming and paleopressure evolution

AbstractCH4 has been observed on Mars both by remote sensing and in situ during the past 15 yr. It could have been produced by early Mars serpentinization processes that could also explain the observed Martian remanent magnetic field. Assuming a cold early Mars, a cryosphere could trap such CH4 as clathrates in stable form at depth. The maximum storage capacity of such a clathrate cryosphere has been recently estimated to be 2 × 1019 to 2 × 1020 moles of methane. We estimate how large amounts of serpentinization‐derived CH4 stored in the cryosphere have been released into the atmosphere during the Noachian and the early Hesperian. Due to rapid clathrate dissociation and photochemical conversion of CH4 to H2, these episodes of massive CH4 release may have resulted in transient H2‐rich atmospheres, at typical levels of 10–20% in a background 1–2 bar CO2 atmosphere. The collision‐induced heating effect of H2 present in such an atmosphere has been shown to raise the surface temperature above the water freezing point. We show how local and rapid destabilization of the cryosphere can be induced by large events (such as the Hellas Basin or Tharsis bulge formation) and lead to such releases. Our results show that the early Mars cryosphere had a sufficient CH4 storage capacity to have maintained H2‐rich transient atmospheres during a total time period up to several million years or tens of million years, having potentially contributed to the formation of valley networks during the Noachian/early Hesperian.

A modelling approach to the techno-economics of Biomass-to-SNG/Methanol systems: Standalone vs Integrated topologies

Chile accounts for one of the most important forest areas in Latin America; nevertheless, both Chilean energy and chemical infrastructures heavily relies on imported fossil fuels. This study focuses on the analysis of several scenarios contributing to change this status quo by producing biomass-based Methanol and Synthetic Natural Gas (SNG). A comprehensive flowsheeting model, including such technologies, is developed and validated. The plants are assembled in a general superstructure to perform their energy integration and economic evaluation. For the studied scenarios, the energy efficiency of gasifier was 74%; Methanol and SNG yields were 0.59kgMeOH/kgDry-biomass and 0.33kgSNG/kgDry-biomass, respectively. The biomass-derived SNG has an average of 88%mol of methane and a Lower Heating Value of 41MJ/kg. The unit energy cost ($/GJ) via SNG and Methanol were 18.41$/GJ and 29.54$/GJ for standalone operation, and both can be reduced by 12.7% and 9.5%, respectively, by using an integrated process scheme. Finally, near 25% of sensitivity on unit cost of products (energy based) was found when the feedstock price varied between 1 and 60US$/tonne.

Heat Transfer during the Dissociation of Hydrate in Porous Media

The decomposition of gas hydrate accompanied with phase transformation is an endothermic process demanding approximately 52-60kJ of latent heat per mole of methane in hydrate. Energy is a key factor that restricts the hydrate exploitation. Hence the heat transfer plays a very significant role in the decomposition of hydrate. This paper describes a simple analytical model in cylindrical coordinate for simulating gas production from homogeneous hydrates in porous media by the thermal stimulation method. The results from the analytical solution can predict the temperature distribution in the decomposed and undecomposed hydrate zone, the decomposing interface location at any time, and the rate of the decomposition. This simple model can be used to perform the feasibility of commercial gas production from hydrates reservoirs in the South China Sea region using the warm-seawater at surface. It is of great significance to guide the practical production.

Investigation of various feed conditions on NGL recovery plant energy and exergy performance: A case study

NGL recovery from natural gas is an important process in gas refineries to achieve objectives including: the elimination of heavy hydrocarbons to reach the standard specification of sale gas when the possibility of condensation in pipelines is high and afterwards the possibility of selling it in the market. The high heating value of gas condensates causes the attention of gas companies to this precious resource. The existence of light and volatile particles in gas condensates and stabilization process requirement are the greatest challenges of using this resource on refineries. Therefore, this paper deals with energy and exergy performance of NGL recovery plant in Sirri Island taking various typical feed compositions classified as lean and rich. A commercial simulator was used to obtain thermodynamic properties of the process streams and to perform mass and energy balances. Due to changes in the composition entering to de-methanization unit, in this article, simulation and exergy analysis was investigated simultaneously for the five feeds with different percentages of composition. The equations of exergy destruction and exergy efficiency for the main system components such as heat exchangers, compressors and expander were developed and utilized for evaluating system performance. Simulation results and the exergy evaluation showed that with increasing compounds heavier than methane in de-methanizer feed, the efficiency of exchanger and compression work will be reduced. Approximately 60% of the exergy efficiency was for the feed containing 86.68% mol methane while for the feed containing 65.21% mol methane, exergy efficiency was reduced to 50%. Consequently, the highest exergy destruction and exergy efficiency were belonging to the cold heat exchanger and the re-compressor, respectively.

Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification

Abstract. We mapped, sampled, and quantified gas emissions at the continental margin west of Svalbard during R/V Heincke cruise He-387 in late summer 2012. Hydroacoustic mapping revealed that gas emissions were not limited to a zone just above 396 m water depth. Flares from this depth have gained significant attention in the scientific community in recent years because they may be caused by bottom-water warming-induced hydrate dissolution in the course of global warming and/or by recurring seasonal hydrate formation and decay. We found that gas emissions occurred widespread between about 80 and 415 m water depth, which indicates that hydrate dissolution might only be one of several triggers for active hydrocarbon seepage in that area. Gas emissions were remarkably intensive at the main ridge of the Forlandet moraine complex in 80 to 90 m water depths, and may be related to thawing permafrost. Focused seafloor investigations were performed with the remotely operated vehicle (ROV) "Cherokee". Geochemical analyses of gas bubbles sampled at about 240 m water depth as well as at the 396 m gas emission sites revealed that the vent gas is primarily composed of methane (> 99.70%) of microbial origin (average δ13C = −55.7‰ V-PDB). Estimates of the regional gas bubble flux from the seafloor to the water column in the area of possible hydrate decomposition were achieved by combining flare mapping using multibeam and single-beam echosounder data, bubble stream mapping using a ROV-mounted horizontally looking sonar, and quantification of individual bubble streams using ROV imagery and bubble counting. We estimated that about 53 × 106 mol methane were annually emitted at the two areas and allow for a large range of uncertainty due to our method (9 to 118 × 106 mol yr−1). First, these amounts show that gas emissions at the continental margin west of Svalbard were on the same order of magnitude as bubble emissions at other geological settings; second, they may be used to calibrate models predicting hydrate dissolution at present and in the future; and third, they may serve as a baseline (year 2012) estimate of the bubble flux that will potentially increase in the future due to ever-increasing global-warming-induced bottom water warming and hydrate dissociation.

Evidence for a hydrogen-sink mechanism of (+)catechin-mediated emission reduction of the ruminant greenhouse gas methane

Methane formation in the rumen is a major cause of greenhouse gas emission. Plant secondary compounds in ruminant diets, such as essential oils, saponins and tannins, are known to affect methane production. However, their methane-lowering properties have generally been associated with undesired side effects such as impaired feed digestibility. Here we show that microbial methane formation in diluted and buffered rumen fluid was significantly lowered in the presence of (+)-catechin, a natural polyphenol. This flavan-3-ol, a tannin precursor, decreased the production of methane in a dose-dependent manner, where 1.0 mol catechin prevented the emission of 1.2 mol methane. During methane mitigation, (+)-catechin was step-wise degraded via C- and A-ring cleavage and reductive dehydroxylation reactions, as indicated by LC-QToF-MS based metabolomic profiling and NMR-based metabolite identification. This accounted for the acceptance of six hydrogen atoms per catechin molecule. Consequently, catechin functions as an extensive hydrogen sink, thereby competing with methane production by rumen methanogens (\( {\text{CO}}_{2} + 4{\text{H}}_{2} \Rightarrow {\text{CH}}_{4} + 2{\text{H}}_{2} {\text{O}} \)). Catechin therefore acts as an antireductant under the anaerobic test conditions, in contrast to its well-known antioxidant role during oxidative stress. The reductive degradation of catechin had no impact on the formation of ruminal fermentation products such as short-chain fatty acids in this model system. These results highlight the potential of plant secondary compounds to replace methane precursors as hydrogen sinks, and justify future scientific screening programs for similar, potentially more effective organic compounds.

Adiabatic Flame Temperature for Combustion of Methane II

We calculate the adiabatic flame temperature of a mixture of methane and oxygen in the presence of a diluent gas then determine the mole fractions of methane without respect to nitrogen and solve for the moles of oxygen present. Knowing the moles of methane and oxygen, allows us to calculate the moles of nitrogen present at four constant mole fractions of nitrogen, and the adiabatic flame temperature is determined from the energy released by the reaction. Lastly, we produce several graphs to compare the adiabatic flame temperatures at different mole fractions of nitrogen.

Hydrogen and methane selectivity during alkaline supercritical water gasification of biomass with ruthenium-alumina catalyst

Ruthenium supported on alpha-alumina spheres has been employed as a catalyst for the gasification of glucose and other biomass-related samples in supercritical water at 550°C, 36MPa, in a batch Inconel reactor. Most of the reactions were conducted in the presence of alkaline additives particularly sodium hydroxide and calcium oxide (hydroxide). In general, over 96% carbon gasification efficiencies (CGE) were achieved in the presence of Ru/Al2O3, while hydrogen gasification efficiencies (HGE) based on result-derived reaction stoichiometries reached 87% for glucose. Both HGE and CGE approached 100% for the sodium carboxylates. Without alkaline additives, Ru/Al2O3 converted glucose into gas product with average yields of 10.8mol hydrogen/(kg of glucose), 8.6mol methane/(kg of glucose) and 17mol carbon dioxide/(kg of glucose), while carbon monoxide and C2-C4 hydrocarbons made up only 1mol//(kg of glucose). However, when the ruthenium catalyst was used in combination with sodium hydroxide and calcium hydroxide, the selectivity towards hydrogen gas increased, with the complete removal of carbon dioxide. Similar yields of hydrogen (14.7mol/kg of glucose) and methane (12.8mol/kg of glucose) were obtained with CaO and Ru/Al2O3. Reactions of sodium carboxylates (formate and acetate) suggested that the ruthenium catalyst was capable of catalyzing the Sabatier reversible reaction in both the forward and backward directions. The yield of each gas was found to be dependent on the concentrations of methane, hydrogen and carbon dioxide in the reactor.

Quantification of gas bubble emissions from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan)

Evidence for twelve sites with gas bubble emissions causing hydroacoustic anomalies in 18 kHz echosounder records (‘flares’) was obtained at the convergent Makran continental margin. The hydroacoustic anomalies originating from hydrocarbon seeps at water depths between 575 and 2870 m disappeared after rising up to 2000 m in the water column. Dives with the remotely operated vehicle ‘Quest 4000 m’ revealed that several individual bubble vents contributed to one hydroacoustic anomaly. Analyzed gas samples suggest that bubbles were mainly composed of methane of microbial origin. Bubble size distributions and rise velocities were determined and the volume flux was estimated by counting the emitted bubbles and using their average volume. We found that a low volume flux (Flare 1 at 575 mbsl: 90 ml/min) caused a weak hydroacoustic signal in echograms whereas high volume fluxes (Flare 2 at 1027 mbsl: 1590 ml/min; Flare 5 C at 2870 mbsl: 760 ml/min) caused strong anomalies. The total methane bubble flux in the study area was estimated by multiplying the average methane flux causing a strong hydroacoustic anomaly in the echosounder record with the total number of equivalent anomalies. An order‐of‐magnitude estimate further considers the temporal variability of some of the flares, assuming a constant flux over time, and allows a large range of uncertainty inherent to the method. Our results on the fate of bubbles and the order‐of‐magnitude estimate suggest that all of the ∼40 ± 32 × 106 mol methane emitted per year within the gas hydrate stability zone remain in the deep ocean.

Thermodynamic evaluation of dry reforming of vegetable oils for production of synthesis gas

The dry reforming (DR) is a promising technology for utilization of greenhouse gas, carbon dioxide, to produce synthesis gas for downstream synthesis of valuable chemicals and fuels. In this study, equilibrium of DR and autothermal dry reforming (ATDR) of vegetable oils was investigated by Gibbs free energy minimization method. The effects of various process variables of DR and ATDR of vegetable oils such as temperature (673–1273 K), carbon dioxide-to-carbon mole ratio (CCMR) (0.5–3.0), and oxygen-to-carbon mole ratio (OCMR) (0–1.0) were studied to obtain equilibrium products composition, thermodynamically promising operating conditions, and thermoneutral conditions of the process. The study revealed that insignificant amount of coke and compounds containing two or more carbon atoms were formed for both DR and ATDR of vegetable oils. The hydrogen yield was found to increase with increase in temperatures for DR of vegetable oil. At temperature 983 K and above, the hydrogen yield was found to increase with CCMR, reach maxima, and then decrease with further increase in CCMR. The carbon dioxide conversion and yield of CO and water were increased and yield of methane was decreased with increase in temperature. The yield of CO and water were increased and the conversion of carbon dioxide and yield of methane were decreased with increase of CCMR. For ATDR of vegetable oils, the reduced yield of CO and methane and enhanced yield of water and hydrogen (up to temperature of maximum hydrogen yield) were observed compared to that of DR. From critical analysis of the results of DR and ATDR of vegetable oil, the optimum conditions for maximum yield of hydrogen with very low yield of methane were determined as 1000–1050 K, CCMR of about 1, and oxygen-to-carbon mole ratio of 0.6–0.7. It was observed that about 80% hydrogen yield with 78–83 moles of CO and 0.2–0.6 moles of methane per mole of vegetable oil could be obtained under the optimum conditions.

Vodyanitskii mud volcano, Sorokin trough, Black Sea: Geological characterization and quantification of gas bubble streams

Vodyanitskii mud volcano is located at a depth of about 2070 m in the Sorokin Trough, Black sea. It is a 500-m wide and 20-m high cone surrounded by a depression, which is typical of many mud volcanoes in the Black Sea. 75 kHz sidescan sonar show different generations of mud flows that include mud breccia, authigenic carbonates, and gas hydrates that were sampled by gravity coring. The fluids that flow through or erupt with the mud are enriched in chloride (up to ∼650 mmol L −1 at ∼150-cm sediment depth) suggesting a deep source, which is similar to the fluids of the close-by Dvurechenskii mud volcano. Direct observation with the remotely operated vehicle Quest revealed gas bubbles emanating at two distinct sites at the crest of the mud volcano, which confirms earlier observations of bubble-induced hydroacoustic anomalies in echosounder records. The sediments at the main bubble emission site show a thermal anomaly with temperatures at ∼60 cm sediment depth that were 0.9 °C warmer than the bottom water. Chemical and isotopic analyses of the emanated gas revealed that it consisted primarily of methane (99.8%) and was of microbial origin ( δD-CH 4 = −170.8‰ (SMOW), δ 13C-CH 4 = −61.0‰ (V-PDB), δ 13C-C 2H 6 = −44.0‰ (V-PDB)). The gas flux was estimated using the video observations of the ROV. Assuming that the flux is constant with time, about 0.9 ± 0.5 × 10 6 mol of methane is released every year. This value is of the same order-of-magnitude as reported fluxes of dissolved methane released with pore water at other mud volcanoes. This suggests that bubble emanation is a significant pathway transporting methane from the sediments into the water column.

Basic Thermodynamic Studies and Exergetic Analysis of Fuel Cell Steam Reforming for Natural Gas in Waste Landfill and Anaerobic Digestor Gas

One of the great opportunities for waste utilization and reduction of global warming (carbon footprint) is the utilization of the methane in the gas to produce electric power with a fuel cell. These waste gases are primarily methane which must be reformed to hydrogen before use in a fuel cell. There are three basic types of methane reforming—steam, autothermal and partial oxidation. Temperature, pressure, and steam-to-carbon ratio play an important role in the performance of steam reforming. These variables also influence the reversible work and reaction enthalpy of the reforming products. A fuel cell stack or cell integrated steam reformer allows a recirculation of reversible heat as long as the operational temperature of the fuel cell is appropriate to the temperature of the reformer. The maximum total reversible work (highest exergetic efficiency) of the hydrogen and the carbon monoxide Wrev,H2,CO,ox is achieved at 762 kJ per 1 mol methane which is converted in the fuel processor. This corresponds to a maximum intrinsic thermal efficiency ηTh,Max, of 95% at an optimum temperature of 1023 K. This optimum temperature is in the operating temperature range of the high-temperature fuel cells like the molten carbonate and solid oxide fuel cells. Higher efficiencies can be expected with these fuel cells with steam reforming when utilizing natural gas, anaerobic digestor gas, or landfill gas.