Iron-promoted zirconia-alumina supported Ni catalyst for highly efficient and cost-effective hydrogen production via dry reforming of methane.

Developing cost-effective and high-performance catalyst systems for dry reforming of methane (DRM) is crucial for producing hydrogen (H2) sustainably. Herein, we investigate using iron (Fe) as a promoter and major alumina support in Ni-based catalysts to improve their DRM performance. The addition of iron as a promotor was found to add reducible iron species along with reducible NiO species, enhance the basicity and induce the deposition of oxidizable carbon. By incorporating 1 wt.% Fe into a 5Ni/10ZrAl catalyst, a higher CO2 interaction and formation of reducible "NiO-species having strong interaction with support" was observed, which led to an ∼80% H2 yield in 420 min of Time on Stream (TOS). Further increasing the Fe content to 2wt% led to the formation of additional reducible iron oxide species and a noticeable rise in H2 yield up to 84%. Despite the severe weight loss on Fe-promoted catalysts, high H2 yield was maintained due to the proper balance between the rate of CH4 decomposition and the rate of carbon deposit diffusion. Finally, incorporating 3 wt.% Fe into the 5Ni/10ZrAl catalyst resulted in the highest CO2 interaction, wide presence of reducible NiO-species, minimum graphitic deposit and an 87% H2 yield. Our findings suggest that iron-promoted zirconia-alumina-supported Ni catalysts can be a cheap and excellent catalytic system for H2 production via DRM.

A Comprehensive Integration and Synthesis of Methane Emissions from Canada's Oil and Gas Value Chain.

Methane emissions from the global oil and gas value chain are a major contributor to climate change, and their mitigation could avoid 0.1 °C of warming by 2050. Here, we synthesize nearly a decade of research encompassing thousands of multiscale methane measurements along the oil and gas value chain (production to end use) to better constrain estimates of methane emissions from Canada's energy sector and to identify research gaps contributing to uncertainty in current estimates. We find that total value chain methane emissions are 2,600 (2,100-3,700) kt, which broadly agrees with Canada's latest official inventory that now includes atmospheric measurement data in some of their oil and gas methane estimates. Accurate understanding of emission magnitudes is critical because Canada committed to a 75% reduction of oil and gas methane emissions by 2030. We also identify and discuss information gaps in both emissions and activity data, namely, from the midstream, downstream, and end-use sectors. While they make up a smaller portion of the total inventory, accurate quantification of these emissions is still important and could point to more cost-effective mitigation solutions. This work emphasizes the need for frequent, comprehensive measurements to better constrain the climate impacts of the oil and gas sector and to validate reductions and commitments pledged by industry and governments.

Biostimulation accelerates landfill stabilization and resource utilization efficiency, providing feasible technical support for the overall lifecycle management of landfills.

Although sanitary landfill is one of the principal municipal solid waste (MSW) treatment and disposal methods, its limitations, such as insufficient use of resources, long stability time, and high risk of environmental pollution, must be urgently resolved. The effect of multifunctional microbial community (MMC) inoculation on MSW landfill process was investigated using simulated anaerobic bioreactor landfill (ABL), and composition and microbial community structure of waste, leachate water quality, and gas production were monitored. MMC inoculation significantly accelerated lignocellulose degradation, and the (Hemicellulose content + Cellulose content)/Lignin content ((C+H)/L) of MMC inoculation treatment was 0.89±0.04 on day 44, which was significantly lower than that of the control group (1.14±0.02). At the end of the landfill process, the reductive organic matter, ammonia nitrogen, and volatile fatty acids in the leachate of the MMC group decreased to 9,400.00±288.68, 332.78±5.77, and 79.33±6.44 mg L-1, respectively, significantly lower than those of the control group (24,167.00±208.17, 551.14±5.60, and 156.33±8.22 mg L-1). Meanwhile, MMC inoculation increased the methane production to 118.12±5.42 L kg-1 of dry matter, significantly higher than the output of the control group (60.60±2.24 L kg-1). MMC inoculation optimized the microbial community structure in ABL and increased lignocellulose-degrading microorganisms (Brevundimonas, Cellvibrio, Leifsonia, and Devosia) and methanogen (Methanosaeta and Methanoculleus) abundance in the middle stage of landfill. Moreover, MMC introduction improved the abundance of carbon metabolism enzymes and increased saprophytic fungal abundance by 30.09% in the middle stage of landfill. Overall, these findings may help in developing an effective method to increase the lifespan of landfills and enhance their post-closure management.

Effects of cashew nutshell liquid on milk production and methane emission of dairy cows in a farm condition.

This study aimed to clarify the efficacy of cashew nutshell liquid (CNSL) in methane emissions, milk production, and rumen fermentation of lactating cows in practical conditions. Ten Holstein lactating cows were used in a free-stall barn with a milking robot. Two treatments were arranged as control (no CNSL additive, n = 5) or CNSL addition (10 g/day of CNSL, n = 5) for 21 days after the 7-day preliminary period. A sniffer method was applied to predict daily methane production and methane conversion factor (MCF). In vitro, rumen gas production was also tested using the rumen fluid of individual cows. Daily dry matter intake (DMI), eating time, milk production, and methane production were not affected by the CNSL addition. However, methane production per DMI and MCF were lower (p ≤ 0.01) for the CNSL cows than those for the control cows. Ruminal total volatile fatty acid (VFA) concentration and acetate proportion tended to be lower (p < 0.15) for CNSL cows. A tendency to decrease (p < 0.10) in methane was also observed in the in vitro incubation with the rumen fluid obtained from the CNSL cows compared with those from the control cows. These results suggest that adding CNSL to diets could reduce the methane yield of cows in practical conditions.

Surprising concentrations of hydrogen and non-geological methane and carbon dioxide in the soil.

Due to its potential use as a carbon-free energy resource with minimal environmental and climate impacts, natural hydrogen (H2) produced by subsurface geochemical processes is today the target of intensive research. In H2 exploration practices, bacteria are thought to swiftly consume H2 and, therefore, small near-surface concentrations of H2, even orders of 102 ppmv in soils, are considered a signal of active migration of geological gas, potentially revealing underground resources. Here, we document an extraordinary case of a widespread occurrence of H2 (up to 1 vol%), together with elevated concentrations of CH4 and CO2 (up to 51 and 27 vol%, respectively), in aerated meadow soils along Italian Alps valleys. Based on current literature, this finding would be classified as a discovery of pervasive and massive geological H2 seepage. Nevertheless, an ensemble of gas geochemical and soil microbiological analyses, including bulk and clumped CH4 isotopes, radiocarbon of CH4 and CO2, and DNA and mcrA gene quantitative polymerase chain reaction analyses, revealed that H2 was only coupled to modern microbial gas. The H2-CO2-CH4-H2S association, wet soil proximity, and the absence of other geogenic gases in soils and springs suggest that H2 derives from near-surface fermentation, rather than geological degassing. H2 concentrations up to 1 vol% in soils are not conclusive evidence of deep gas seepage. This study provides a new reference for the potential of microbial H2, CH4 and CO2 in soils, to be considered in H2 exploration guidelines and soil carbon and greenhouse-gas cycle research.

Non-conductive silicon-containing materials improve methane production by pure cultures of methanogens.

Conductive materials (CM) enhance methanogenesis, but there is no clear correlation between conductivity and faster methane production (MP) rates. We investigated if MP by pure cultures of methanogens (Methanobacterium formicicum, Methanospirillum hungatei, Methanothrix harundinacea and Methanosarcina barkeri) is affected by CM (activated carbon (AC), magnetite), and other sustainable alternatives (sand and glass beads, without conductivity, and zeolites (Zeo)). The significant impact of the materials was on M. formicicum as MP was significantly accelerated by non-CM (e.g., sand reduced the lag phase (LP) duration by 48 %), Zeo and AC (LP reduction in 71% and 75 %, respectively). Conductivity was not correlated with LP reduction. Instead, silicon content in the materials was inversely correlated with the time required for complete MP, and silicon per se stimulated M. formicicum's activity. These findings highlight the potential of using non-CM silicon-containing materials in anaerobic digesters to accelerate methanogenesis.

Aromatic compound 2-acetyl-1-pyrroline coordinates nitrogen assimilation and methane mitigation in fragrant rice.

Rice paddy has been the main source of anthropogenic methane (CH4) emissions, with significant variations among rice varieties. 2-Acetyl-1-pyrroline (2-AP) is the key component of the pleasant aroma in fragrant rice. Here, we show that fragrant rice is metabolically active in nitrogen assimilation and exhibits high levels of 2-AP and that CH4 fluxes at the booting stage and cumulative emissions are 25.5% and 14.8% lower, respectively, in fragrant rice paddies compared with nonfragrant rice paddies. Three precursors involved in 2-AP synthesis-proline, glutamic acid, and ornithine-are identified as crucial nitrogen compounds that significantly promote CH4 oxidation in the rhizosphere. Augmenting 2-AP synthesis, either through foliar spraying or by utilizing CRISPR-Cas9 technology to generate knockout lines of BETAINE ALDEHYDE DEHYDROGENASE 2 gene, effectively enhances CH4 oxidation and reduces CH4 fluxes. Our findings reveal that the 2-AP metabolic pathway coordinates the carbon/nitrogen cycle to improve nitrogen assimilation along with high 2-AP levels and mitigate CH4 emissions in paddy ecosystems.

Radiocatalytic synthesis of acetic acid from CH4 and CO2.

The C-C coupling of methane (CH4) and carbon dioxide (CO2) to generate acetic acid (CH3COOH) represents a highly atom-efficient chemical conversion, fostering the comprehensive utilization of greenhouse gases. However, the inherent thermodynamic stability and kinetic inertness of CH4 and CO2 present obstacles to achieving efficient and selective conversion at room temperature. Our study reveals that hydroxyl radicals (·OH) and hydrated electrons (eaq-) produced by water radiolysis can effectively activate CH4 and CO2, yielding methyl radicals (·CH3) and carbon dioxide radicals (·CO2-) that facilitate the production of CH3COOH at ambient temperature. The introduction of radiation-synthesized CuO-anchored TiO2 bifunctional catalyst could further enhance reaction efficiency and selectivity remarkably by boosting radiation absorption and radical stability, resulting in a concentration of 7.1 mmol·L-1 of CH3COOH with near-unity selectivity (>95%). These findings offer valuable insights for catalyst design and implementation in radiation-induced chemical conversion.

Impact of Iron Oxide on Anaerobic Digestion of Frass in Biogas and Methanogenic Archaeal Communities' Analysis.

With the increasing prominence of the global energy problem, socioeconomic activities have been seriously affected. Biofuels, as a renewable source of energy, are of great significance in promoting sustainable development. In this study, batch anaerobic digestion (AD) of frass (swine manure after bioconversion by black soldier fly larvae) and co-digestion with corn straw after the addition of iron oxide (Fe3O4) nanoparticles is investigated, as well as the start-up period without inoculation. The biochemical methane potential of pure frass was obtained using blank 1 group and after the addition of various sizes of Fe3O4 nanoparticles for 30 days period, and similarly, the digestion of frass with straw (blank 2) and after the addition of various sizes of Fe3O4 nanoparticles for 61 days period. The results showed that the average gas production was 209.43 mL/gVS, 197.68 mL/gVS, 151.85 mL/gVS, and 238.15 mL/gVS for the blank, ~176 nm, ~164 nm, and ~184 nm, respectively. The average gas production of frass with straw (blank 2) was 261.64 mL/gVS, 259.62 mL/gVS, 241.51 mL/gVS, and 285.98 mL/gVS for blank 2, ~176 nm, ~164 nm, and ~184 nm, respectively. Meanwhile, the accumulated methane production of the ~184 nm group was 2312.98 mL and 10,952.96 mL, respectively, which significantly increased the biogas production compared to the other groups. The methanogenic results of the frass (30 days) indicated that Methanocorpusculum, Methanosarcina, and Methanomassiliicoccus are the important methanogenic species in the AD reactor, while the microbial diversity of the ~184 nm group was optimal, which may be the reason for the high gas production of ~184 nm.

Redox and Kinetic Properties of Composition-Dependent Active Sites in Copper-Exchanged Chabazite for Direct Methane-to-Methanol Oxidation.

The CH4 oxidation performance of Cu-chabazite zeolites characterized by distinct Si/Al ratios and Cu loadings has been studied and the observed variations in reactivity have been correlated to the differences in the nature of the formed active centers. Plug flow reactor tests, in situ Fourier-transform infrared, and X-ray absorption spectroscopy demonstrate that a decrease in Cu loading shifts the reactivity/redox profile to higher temperatures and increases the CH3OH selectivity and Cu-efficiency. In situ electron paramagnetic resonance, Raman, ultraviolet-visible, Fourier-transform infrared, and photoluminescence spectroscopies reveal that this behavior is associated with the presence of monomeric Cu active sites, including bare Cu2+ and [CuOH]+ present at low Si/Al ratio and Cu loading. Formation of two distinct [Cu2(µ-O)]2+ moieties at higher Si/Al ratio or Cu loading forces these trends into the opposite direction. Operando electron paramagnetic resonance and ultraviolet-visible spectroscopy show that the apparent activation energy of monomeric Cu active species decreases with increasing Si/Al ratio, whereas the one of dimeric centers is unaffected.

Effects of long-term exposure to zinc on performances of anaerobic digesters for swine wastewater treatment under various organic loading rates.

The long-term performance of anaerobic digestion (AD) often decreases substantially when treating swine wastewater contaminated with heavy metals. However, the toxicological characteristics and mechanisms of continuous exposure to heavy metals under different organic loading rates (OLR) are still poorly understood. In these semi-continuous AD experiments, it was found that zinc concentrations of 40 mg/L only deteriorated the reductive environments of AD. In comparison, a concentration of 2.0 mg/L probably facilitated the reproduction of microorganisms in the operating digesters with a constant OLR of 0.51 g COD/(L·d). Nevertheless, when the OLR was increased to 2.30 g COD/(L·d), 2.0 mg/L zinc inhibited various life activities of microorganisms at the molecular level within only 10 days. Hence, even though 2.0 mg/L zinc could promote AD performances from a macroscopic perspective, it had potential inhibitory effects on AD. Therefore, this study deepens the understanding of the inhibitions caused by heavy metals on AD and the metabolic laws of anaerobic microorganisms in swine wastewater treatment. These results could be referred to for enhancing AD in the presence of zinc in practical swine wastewater treatment.

Simultaneous production of syngas and carbon nanotubes from CO2/CH4 mixture over high-performance NiMo/MgO catalyst.

Direct conversion of biogas via the integrative process of dry reforming of methane (DRM) and catalytic methane decomposition (CDM) has received a great attention as a promising green catalytic process for simultaneous production of syngas and carbon nanotubes (CNTs). In this work, the effects of reaction temperature of 700-1100 °C and CH4/CO2 ratio of biogas were investigated over NiMo/MgO catalyst in a fixed bed reactor under industrial feed condition of pure biogas. The reaction at 700 °C showed a rapid catalyst deactivation within 3 h due to the formation of amorphous carbon on catalyst surface. At higher temperature of 800-900 °C, the catalyst can perform the excellent performance for producing syngas and carbon nanotubes. Interestingly, the smallest diameter and the highest graphitization of CNTs was obtained at high temperature of 1000 °C, while elevating temperature to 1100 °C leads to agglomeration of Ni particles, resulting in a larger size of CNTs. The reaction temperature exhibits optimum at 800 °C, providing the highest CNTs yield with high graphitization, high syngas purity up to 90.04% with H2/CO ratio of 1.1, and high biogas conversion (XCH4 = 86.44%, XCO2 = 95.62%) with stable performance over 3 h. The typical composition biogas (CH4/CO2 = 1.5) is favorable for the integration process, while the CO2 rich biogas caused a larger grain size of catalyst and a formation of molybdenum oxide nanorods (MoO3). The long-term stability of NiMo/MgO catalyst at 800 °C showed a stable trend (> 20 h). The experimental findings confirm that NiMo/MgO can perform the excellent activity and high stability at the optimum condition, allowing the process to be more promising for practical applications.

Rice rhizobiome engineering for climate change mitigation.

The year 2023 was the warmest year since 1850. Greenhouse gases, including CO2 and methane, played a significant role in increasing global warming. Among these gases, methane has a 25-fold greater impact on global warming than CO2. Methane is emitted during rice cultivation by a group of rice rhizosphere microbes, termed methanogens, in low oxygen (hypoxic) conditions. To reduce methane emissions, it is crucial to decrease the methane production capacity of methanogens through water and fertilizer management, breeding of new rice cultivars, regulating root exudation, and manipulating rhizosphere microbiota. In this opinion article we review the recent developments in hypoxia ecology and methane emission mitigation and propose potential solutions based on the manipulation of microbiota and methanogens for the mitigation of methane emissions.

Methane Quantification Performance of the Quantitative Optical Gas Imaging (QOGI) System Using Single-Blind Controlled Release Assessment.

Quantitative optical gas imaging (QOGI) system can rapidly quantify leaks detected by optical gas imaging (OGI) cameras across the oil and gas supply chain. A comprehensive evaluation of the QOGI system's quantification capability is needed for the successful adoption of the technology. This study conducted single-blind experiments to examine the quantification performance of the FLIR QL320 QOGI system under near-field conditions at a pseudo-realistic, outdoor, controlled testing facility that mimics upstream and midstream natural gas operations. The study completed 357 individual measurements across 26 controlled releases and 71 camera positions for release rates between 0.1 kg Ch4/h and 2.9 kg Ch4/h of compressed natural gas (which accounts for more than 90% of typical component-level leaks in several production facilities). The majority (75%) of measurements were within a quantification factor of 3 (quantification error of -67% to 200%) with individual errors between -90% and 831%, which reduced to -79% to +297% when the mean of estimates of the same controlled release from multiple camera positions was considered. Performance improved with increasing release rate, using clear sky as plume background, and at wind speeds ≤1 mph relative to other measurement conditions.

Long-term observations on the hydraulic performance of a combined capillary barrier-methane oxidation landfill cover system.

This study quantifies the field hydraulic performance of a dual-functionality landfill cover, combining microbial methane oxidation with water diversion using a capillary barrier. The investigated 500 m2 test field, constructed on a landfill in the Netherlands, consisted of a cover soil optimised for methane oxidation, underlain by a sandy capillary layer and a gravelly capillary block. Outflows from these layers were measured between 2009 and 2023. Average precipitation was 848 mm/a, evapotranspiration, diverted infiltration and breakthrough amounted to 504 (59.4 %), 282 (33.3 %) and 62 (7.3 %) mm/a, respectively. On average, the capillary barrier diverted 82 % of the inflow into the capillary layer. Breakthrough occurred mainly from October to March when evapotranspiration was low and the maximum water storage capacity of the cover soil was reached. During this period, inflow into the capillary barrier exceeded its diversion capacity, caused by the relatively high hydraulic conductivity of the cover soil due to its optimisation for gas transport. The diversion capacity declined drastically in the year after construction and increased again afterwards. This was attributed to suffusion of sand from the capillary layer into the capillary block and subsequent washout to greater depths or the influence of iron precipitates at the bottom of the capillary layer. The effect of a more finely grained methane oxidation layer on the hydraulic and methane oxidation performance should be investigated further. These measures could further improve the combined performance of the dual functionality landfill cover system under the given conditions of a temperate climate.

Optimizing anaerobic digestion: Benefits of mild temperature transition from thermophilic to mesophilic conditions.

Anaerobic digestion (AD) plays a significant role in renewable energy recovery. Upgrading AD from thermophilic (50-57 °C) to mesophilic (30-38 °C) conditions to enhance process stability and reduce energy input remains challenging due to the high sensitivity of thermophilic microbiomes to temperature fluctuations. Here we compare the effects of two decreasing-temperature modes from 55 to 35 °C on cell viability, microbial dynamics, and interspecies interactions. A sharp transition (ST) is a one-step transition by 20 °C d-1, while a mild transition (MT) is a stepwise transition by 1 °C d-1. We find a greater decrease in methane production with ST (88.8%) compared to MT (38.9%) during the transition period. ST mode overproduced reactive oxygen species by 1.6-fold, increased membrane permeability by 2.2-fold, and downregulated microbial energy metabolism by 25.1%, leading to increased apoptosis of anaerobes by 1.9-fold and release of intracellular substances by 2.9-fold, further constraining methanogenesis. The higher (1.6 vs. 1.1 copies per gyrA) metabolic activity of acetate-dependent methanogenesis implied more efficient methane production in a steady mesophilic, MT-mediated system. Metagenomic binning and network analyses indicated that ST induced dysbiosis in keystone species and greatly enhanced microbial functional redundancy, causing loss of microbial syntrophic interactions and redundant metabolic pathways. In contrast, the greater microbial interconnections (average degrees 44.9 vs. 22.1) in MT at a steady mesophilic state suggested that MT could better maintain necessary system functionality and stability through microbial syntrophy or specialized pathways. Adopting MT to transform thermophilic digesters into mesophilic digesters is feasible and could potentially enhance the further optimization and broader application of practical anaerobic engineering.

Methane gas in breath test is associated with non-alcoholic fatty liver disease.

Although the associations between a patient's body mass index (BMI) and metabolic diseases, as well as their breath test results, have been studied, the relationship between breath hydrogen/methane levels and metabolic diseases needs to be further clarified. We aimed to investigate how the composition of exhaled breath gases relates to metabolic disorders, such as diabetes mellitus, dyslipidemia, hypertension, and nonalcoholic fatty liver disease (NAFLD), and their key risk factors. An analysis was performed using the medical records, including the lactulose breath test (LBT) data of patients who visited the Ajou University Medical Center, Suwon, Republic of Korea, between January 2016 and December 2021. The patients were grouped according to four different criteria for LBT hydrogen and methane levels. Of 441 patients, 325 (72.1%) had positive results for methane only (hydrogen < 20 parts per million [ppm] and methane ⩾ 3 ppm). BMIs and NAFLD prevalence were higher in patients with only methane positivity than in patients with hydrogen and methane positivity (hydrogen ⩾ 20 ppm and methane ⩾ 3 ppm). According to a multivariate analysis, the odds ratio of only methane positivity was 2.002 (95% confidence interval [CI]: 1.244-3.221,P= 0.004) for NAFLD. Our results demonstrate that breath methane positivity is related to NAFLD and suggest that increased methane gas on the breath tests has the potential to be an easily measurable biomarker for NAFLD diagnosis.

Animal Behaviour Packs a Punch: From Parasitism to Production, Pollution and Prevention in Grazing Livestock.

Behaviour is often the fundamental driver of disease transmission, where behaviours of individuals can be seen to scale up to epidemiological patterns seen at the population level. Here we focus on animal behaviour, and its role in parasite transmission to track its knock-on consequences for parasitism, production and pollution. Livestock face a nutrition versus parasitism trade-off in grazing environments where faeces creates both a nutritional benefit, fertilizing the surrounding sward, but also a parasite risk from infective nematode larvae contaminating the sward. The grazing decisions of ruminants depend on the perceived costs and benefits of the trade-off, which depend on the variations in both environmental (e.g., amounts of faeces) and animal factors (e.g., physiological state). Such grazing decisions determine the intake of both nutrients and parasites, affecting livestock growth rates and production efficiency. This impacts on the greenhouse gas costs of ruminant livestock production via two main mechanisms: (1) slower growth results in longer durations on-farm and (2) parasitised animals produce more methane per unit food intake. However, the sensitivity of behaviour to host parasite state offers opportunities for early detection of parasitism and control. Remote monitoring technology such as accelerometers can detect parasite-induced sickness behaviours soon after exposure, before impacts on growth, and thus may be used for targeting individuals for early treatment. We conclude that livestock host x parasite interactions are at the centre of the global challenges of food security and climate change, and that understanding livestock behaviour can contribute to solving both.

Effects of Centella asiatica Extracts on Rumen In Vitro Fermentation Characteristics and Digestibility.

Two in vitro experiments were conducted to evaluate the effects of Centella asiatica extract (CAE) supplementation on the rumen's in vitro fermentation characteristics. In the first experiment, CAE with five concentrations (C: 0%; T1: 3.05%; T2: 6.1%; T3: 12.2%; and T4: 24.4% CAE in diet) was supplemented in the rumen fluid and incubated for 6, 24, and 48 h to determine the optimal dosage. The total gas and methane production increased in all incubation times, and the total volatile fatty acids increased at 6 and 48 h. Ammonia nitrogen, branched chain volatile fatty acids, acetate, and butyrate were increased by CAE supplementation. T1 was chosen as the optimal dosage based on the total volatile fatty acids, branched chain volatile fatty acids, and ammonia nitrogen production. The CAE with the identified optimal dosage (T1) was incubated to identify its effect on the rumen's in vitro degradability in the second experiment. The CAE supplementation did not influence the in vitro dry matter, crude protein, or neutral detergent fiber degradability. In conclusion, CAE has no CH4 abatement or digestion promotion effects. However, CAE could be utilized as a feed additive to increase the rumen's total volatile fatty acid production without an adverse effect on the in vitro dry matter, crude protein, or neutral detergent fiber degradability.

Oxygen Species Involved in Complete Oxidation of CH4 by SrFeO3-δ in Chemical Looping Reforming of Methane.

Compared with conventional methane reforming technologies, chemical looping reforming (CLR) has the advantages of self-elimination of coke, a suitable syngas ratio for certain down-stream processes, and a pure H2 or CO stream. In the reduction step of CLR, methane combustion has to be inhibited, which could be achieved by designing appropriate oxygen carriers and/or optimizing the operating conditions. To gain a further understanding of the combustion reaction, methane oxidation by perovskite (SrFeO3-δ) at 900 °C and 1 atm in a pulse mode was investigated in this work. The oxygen non-stoichiometry of SrFeO3-δ prepared by a Pechini-type polymerizable complex method is 0.14 at ambient conditions, and it increases to 0.25 and subsequently to 0.5 when heating from 100 to 900 °C in argon that contains 2 ppmv of molecular oxygen. The activation energies of the first and second transitions are 294 and 177 kJ/mol, respectively. The presence of 0.99 vol.% hydrogen in argon significantly reduces the amount CO2 produced. At a pulse interval of 10 min, the amount of CO2 produced in the absence of hydrogen is one order of magnitude greater than that in the presence of hydrogen. In the former case, the amount of CO2 produced dramatically decreases first and then gradually approaches a constant, and the oxygen species involved in methane combustion can be partially replenished by extending the pulse interval, e.g., 82.5% of this type of oxygen species is replenished when the pulse interval is extended to 60 min. The restored species predominantly originate from those that reside in the surface layer or even in the bulk.