Methane

This study presents a new method to remove lignin from wheat straw (lignocellulosic) using the ozonation technique. Lignocellulosic material is a complex biopolymer composed of cellulose, hemicellulose and lignin. Apart from lignin, which acts as a chemical resistant, lignocellulosic is the main resource of cellulose and hemicellulose sugars. The ozonation reaction takes place in a two-phase solid–gas fluidization stainless steel reactor. The focus of this paper is to investigate the kinetics that govern lignin removal from lignocellulosic material after ozonation treatment. The kinetics of lignin removal did not agree with the experimental data until the suggested model is modified to a pseudo-second-order. The results showed that at a higher ozone supply of 150 mg min⁻¹, the surface reaction and intra-particular diffusion were the most significant factors to remove the lignin. Moreover, at a lower ozone supply of 30 mg min⁻¹, the intra-particular diffusion was the only contributor towards lignin removal. Full article

In this paper, a predictive combustion model is developed and implemented in GT-Power. The model consists of a detailed physically/chemically based ignition delay model, including a 1D spray model. The spray model results at the start of combustion are used to initialize the combustion model. The spray zone and the homogenous natural gas/air mixture are burned with different combustion models, to account for the effect of the inhomogeneous fuel distribution. NOx-emissions are modelled using a standard Extended Zeldovich Mechanism, and for the HC-emissions, two flame quenching models are included and extended with an empirical correlation. The models are calibrated with measurement data from a single cylinder engine, except for the ignition delay model which needs no calibration. The start of combustion and the combustion parameters are predicted well for a wide range of injection timings and operation conditions. Furthermore, considering unburned fuel, the engine operation parameters BSFC and IMEP are also predicted satisfactory. Due to the detailed description of the different combustion phases, the influence of the injection timing on the NOx-emission is captured satisfactorily, with the standard NOx-model. Finally, the knock limited MFB50 is also predicted within an acceptable range. Full article

Syngas generated from the catalytic dry reforming of methane (DRM) enables the downstream production of H₂ fuel and value-added chemicals. Ni-based catalysts with metal oxides, as both supports and promoters, are widely applied in the DRM reaction. In this review, four types of metal oxides with support confinement effect, metal-support interaction, oxygen defects, and surface acidity/basicity are introduced based on their impacts on the activity, selectivity, and stability of the Ni-based catalyst. Moreover, the structure–performance relationships are discussed in-depth. Finally, conclusive remarks and prospects are proposed. Full article

Stubble burning in India continues despite the severe consequences on the environment and the massive health crisis in the country. Farmers resort to such practices as a cheap and hasty solution post-harvest, which helps them prepare for their next crops. This study employs a mathematical model, the ADM1 (Anaerobic Digestion Model No. 1), to design a virtual biogas plant in the SIMBA simulation platform. The plant was designed keeping the small-scale farmers in mind, hence, cost-effectiveness, simplicity in design and operation remained a priority. Simulations were performed with different crop leftovers that are widely subjected to on-farm burning in the country such as from rice, wheat, sugarcane, cotton and maize. Simulation trials were performed for each crop residue for nearly two years, to observe the digester performance and possible disruptions over prolonged periods. The optimal feeding ratio and operating conditions for process stability were determined. Simulations revealed generation of nearly 9–10 m³ methane per day, equivalent to 90–100 kWh electricity. Co-fermentation with animal manures was strongly recommended by the model for process stability and to avoid pH disruptions due to organic acid accumulations. Policy makers and farmers are, thus, encouraged to explore a sustainable alternative to generate energy from stubble. Full article

Exploring advanced catalysts and reaction systems operated at mild reaction conditions is crucial for conducting the direct methane oxidation reaction toward oxygenate products. Many efforts have been put into research on pentasil−type (MFI) zeolites based on mononuclear and/or binuclear iron sites, using H₂O₂ as the oxidant. In this work, we present a modified liquid ion−exchange method to better control Fe loading in a mordenite−type (MOR) zeolite with a Si/Al molar ratio of 9. The optimized Fe/MOR catalyst showed excellent performance in the direct methane oxidation reaction with turnover frequencies (TOFs) of 555 h⁻¹ to C₁ oxygenates, significantly better than the reported activity. Multiple comparative experiments were conducted to reveal the mechanism behind the performance. Strikingly, the active sites in the Fe/MOR catalyst were found to be mononuclear iron sites, confirmed by transmission electron microscopy (TEM), ultraviolet−visible diffuse reflectance spectroscopy (UV−vis DRS), and X-ray absorption spectroscopy (XAS). Increasing the iron loading led to the aggregation of the iron sites, which tend to trigger undesirable side reactions (i.e., H₂O₂ decomposition and over−oxidation), resulting in a significant decrease in TOFs to C₁ oxygenates. Full article

Growing concern about climate processes has caused an interest in low-carbon fuels, such as methane and hydrogen. Although hydrogen seems to be beyond comparison in this regard, the need for high energy consumption for its production—mainly due to the same fossil hydrocarbons, low specific volume energy, and problems with its storage and transportation—make the production and consumption in the “hydrogen energy” chain extremely expensive, and even environmentally unattractive. Estimates show that it is significantly inferior to methane-based energy not only in terms of costs and efficiency, but also in terms of global CO₂ emissions. The vast resources of natural methane, primarily gas hydrates, are able to provide humanity with energy and hydrocarbons for hundreds of years. Meanwhile, promising modern technologies for the conversion of methane into basic chemicals—including new autothermal technologies for its oxidative conversion into syngas and its direct conversion into chemicals—allow the consideration of methane not only as a fuel, but also as the basis of future organic chemistry. Methane and other hydrocarbons, synthesized using thermonuclear energy from CO₂ and water—which are abundant on the Earth—can remain the most convenient mobile, easily stored and transported fuels and universal chemical raw materials, even after the inevitable transition to thermonuclear energy in the distant future. The inclusion of CO₂ through the synthesis of methane into the global energy cycle will allow real global carbon neutrality to be achieved. Full article

This review aims to elucidate the contemporary methods of measuring and estimating methane (CH₄) emissions from ruminants. Six categories of methods for measuring and estimating CH₄ emissions from ruminants are discussed. The widely used methods in most CH₄ abatement experiments comprise the gold standard respiration chamber, in vitro incubation, and the sulfur hexafluoride (SF₆) techniques. In the spot sampling methods, the paper discusses the sniffer method, the GreenFeed system, the face mask method, and the portable accumulation chamber. The spot sampling relies on the measurement of short-term breath data adequately on spot. The mathematical modeling methods focus on predicting CH₄ emissions from ruminants without undertaking extensive and costly experiments. For instance, the Intergovernmental Panel on Climate Change (IPCC) provides default values for regional emission factors and other parameters using three levels of estimation (Tier 1, 2 and 3 levels), with Tier 1 and Tier 3 being the simplest and most complex methods, respectively. The laser technologies include the open-path laser technique and the laser CH₄ detector. They use the laser CH₄ detector and wireless sensor networks to measure CH₄ flux. The micrometeorological methods rely on measurements of meteorological data in line with CH₄ concentration. The last category of methods for measuring and estimating CH₄ emissions in this paper is the emerging technologies. They include the blood CH₄ concentration tracer, infrared thermography, intraruminal telemetry, the eddy covariance (EC) technique, carbon dioxide as a tracer gas, and polytunnel. The emerging technologies are essential for the future development of effective quantification of CH₄ emissions from ruminants. In general, adequate knowledge of CH₄ emission measurement methods is important for planning, implementing, interpreting, and comparing experimental results. Full article

Ni/CeO₂ catalysts were synthesized by the coprecipitation method in a basic medium, using different solvents: water, methanol, ethanol, and isopropanol (Ni content, 10% wt.). These catalysts were tested in the production of syngas through the oxidative reforming of methane (ORM), and partial oxidation of methane (POM). The results of this research demonstrated that the use of alcohols (methanol, ethanol, and isopropanol) during the preparation of the Ni/CeO₂ catalysts by the coprecipitation method, improved their characteristics such as crystallite size (nm), surface area (m²·g⁻¹), and reducibility (measured by H₂-TPR) that influenced on their catalytic performance in ORM and POM reactions. The best solvent of this study was isopropanol. The use of alcohols (methanol, ethanol, isopropanol) in the co-precipitation method led to the formation of filamentous carbon on the catalyst after the reactions. The catalyst synthesized in the water proved to be inefficient in the POM and ORM reactions and led to the formation of amorphous carbon after the reactions. Full article

The catalytic activation of CH₄ by limited amounts of O₂ produces a mixture of synthesis gas (CO, H₂) and light hydrocarbons (C₂H_x), the relative amounts of each depending on catalyst type and process conditions. Using an elementary reaction mechanism for the oxidative coupling of methane (OCM) on a La₂O₃/CeO₂ catalyst derived from the literature, this study replaces the activating O₂ with moist H₂O₂ vapor to reduce synthesis gas production while improving C₂H_x yields and selectivities. As the H₂O₂ content of the activating oxidant rises, more of the CH₄ conversion occurs in the gas phase instead of with the catalytic surface. In a packed bed reactor (PBR), the use of H₂O₂ allows the PBR “light-off” to occur using a lower feed temperature. In exchange for a small decline in CH₄ conversion, C₂H_x selectivity increases while synthesis gas production drops. In a continuous stirred tank reactor (CSTR), H₂O₂ improves C₂H_x over synthesis gas across a wider range of feed temperatures than is possible with the PBR. This suggests the CSTR will likely reduce OCM preheating requirements. Full article

The handheld, portable laser methane detector (LMD) was developed to detect gas leaks in industry from a safe distance. Since 2009, it has also been used to measure the methane (CH₄) concentration in the breath of cattle, sheep, and goats to quantify their CH₄ emissions. As there is no consensus on a uniform measurement and data-analysis protocol with the LMD, this article discusses important aspects of the measurement, the data analysis, and the applications of the LMD based on the literature. These aspects, such as the distance to the animal or the activity of the animals, should be fixed for all measurements of an experiment, and if this is not possible, they should at least be documented and considered as fixed effects in the statistical analysis. Important steps in data processing are thorough quality control and reduction in records to a single point measurement or “phenotype” for later analysis. The LMD can be used to rank animals according to their CH₄ breath concentration and to compare average CH₄ production at the group level. This makes it suitable for genetic and nutritional studies and for characterising different breeds and husbandry systems. The limitations are the lower accuracy compared to other methods, as only CH₄ concentration and not flux can be measured, and the high amount of work required for the measurement. However, due to its flexibility and non-invasiveness, the LMD can be an alternative in environments where other methods are not suitable or a complement to other methods. It would improve the applicability of the LMD method if there were a common protocol for measurement and data analysis developed jointly by a group of researchers. Full article

The leakage of methane from the subsurface on the coalfield or natural gas field invariably becomes an important issue nowadays. In notable addition, materials such as activated carbon, zeolites, and Porapak have been successfully identified as adsorbents. Those adsorbents could adsorb methane at atmospheric pressure and room temperature. Therefore, in this scholarly study, a new method using adsorbents to detect points of methane leakage that can cover a wide-scale area was developed. In the beginning, the most capable adsorbent should be determined by quantifying adsorbed methane amount. Furthermore, checking the possibility of adsorption in the column diffusion and desorption method of adsorbents is equally necessary. The most capable adsorbent was activated carbon (AC), which can adsorb 1.187 × 10⁻³ mg-CH₄/g-AC. Hereinafter, activated carbon successfully can adsorb methane through column diffusion, which simulates the situation of on-site measurement. The specific amount of adsorbed methane when the initial concentrations of CH₄ in a bag were 200 ppm, 100 ppm, and 50 ppm was found to be 0.818 × 10⁻³ mg-CH₄/g-AC, 0.397 × 10⁻³ mg-CH₄/g-AC, 0.161 × 10⁻³ mg-CH₄/g-AC, respectively. Desorption of activated carbon analysis shows that methane concentration increases during an hour in the temperature bath under 80 °C. In conclusion, soil methane leakage points can be detected using activated carbon by identifying the observed methane concentration increase. Full article

Mechanisms of growth and dissociation, growth rates, and morphology of gas hydrates of methane, carbon dioxide, and two CH${}_4$:CO${}_2$ mixtures (80:20 and 30:70 nominal concentration) were studied using using high resolution images and very precise temperature control. Subcooling and a recently proposed mass transfer-based driving force were used to analyze the results. When crystal growth rates did not exceed 0.01 mm/s, all systems showed faceted, euhedral crystal habits at low driving forces. At higher driving forces and growth rates, morphologies were different for all systems. These results solve apparent contradictions in literature about the morphology of hydrates of methane, carbon dioxide, and their mixtures. Differences in the growth mechanism of methane-rich and carbon dioxide-rich hydrates were elucidated. It was also shown that hydrate growth of methane, carbon dioxide, and their mixtures proceed via partial dissociation of the growing crystal. Temperature gradients were used to dissociate hydrates at specific locations, which revealed a most interesting phenomenon: On dissociation, carbon dioxide-rich hydrates propagated onto the bare substrate while drawing water from the opposite side of the sample. Furthermore, it was shown that an abrupt change in morphology common to all systems could be correlated to a change in the slope of growth rate data. This change in morphology was explained by a shift in the crystal growth mechanism. Full article