Journal Description
Methane
Methane
is an international, peer-reviewed, open access journal on all aspects of methane published quarterly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 17.3 days after submission; acceptance to publication is undertaken in 9.7 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
Latest Articles
Photoperiod Regulates Aerobic Methane Emissions by Altering Plant Growth and Physiological Processes
Methane 2024, 3(3), 380-396; https://doi.org/10.3390/methane3030021 (registering DOI) - 28 Jun 2024
Abstract
Previous studies have shown that light quality and quantity affect methane emissions from plants. However, the role of photoperiod in plant-derived methane has not been addressed. We studied the effects of two photoperiods—long-day (16 h light/8 h dark), and short-day (8 h light/16
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Previous studies have shown that light quality and quantity affect methane emissions from plants. However, the role of photoperiod in plant-derived methane has not been addressed. We studied the effects of two photoperiods—long-day (16 h light/8 h dark), and short-day (8 h light/16 h dark)—on growth and methane emissions of lettuce (a long-day plant), mung bean (a short-day plant), and tomato (a day-neutral plant) under a temperature regime of 22/18 °C. All species were grown under both light durations. First, seeds were germinated in Petri dishes for one week, then plants were transferred to pots and randomly assigned to one of the two experimental conditions. Under each condition, twelve plants were grown for 21 days; at that time, plant growth and physiological traits, including plant dry mass, growth index, photosynthesis, chlorophyll fluorescence, total chlorophyll, nitrogen balance index, flavonoids, and anthocyanin, were measured. Lettuce plants under the short-day photoperiod had the highest methane emissions. Long-day plants that were exposed to short-day conditions and short-day plants that were exposed to long-day conditions were stressed; day-neutral plants were also stressed under short days (p< 0.05). All three species had decreased total dry mass under short-day conditions, most likely because of decreased photosynthesis and increased transpiration and stomatal conductance. Methane emission was positively correlated with shoot/root mass ratio, nonphotochemical quenching and anthocyanin; but was negatively correlated with stem height, dry mass, photosynthesis, water-use efficiency, total chlorophyll, and flavonoids (p < 0.05). This study revealed that, besides light intensity and quality, light duration can also affect methane emissions from plants.
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Open AccessFeature PaperReview
Recent Advances in the Use of Controlled Nanocatalysts in Methane Conversion Reactions
by
Felipe Anchieta e Silva and Thenner Silva Rodrigues
Methane 2024, 3(2), 359-379; https://doi.org/10.3390/methane3020020 - 11 Jun 2024
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This study investigates the utilization of controlled nanocatalysts in methane conversion reactions, addressing the pressing need for the efficient utilization of methane as a feedstock for valuable chemicals and clean energy. The methods employed include a comprehensive review of recent advancements in nanocatalyst
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This study investigates the utilization of controlled nanocatalysts in methane conversion reactions, addressing the pressing need for the efficient utilization of methane as a feedstock for valuable chemicals and clean energy. The methods employed include a comprehensive review of recent advancements in nanocatalyst synthesis, characterization, and application, as well as the critical analysis of underlying mechanisms and controversies in methane activation and transformation. The main findings reveal significant progress in the design and synthesis of controlled nanocatalysts, enabling enhanced activity, selectivity, and stability in methane conversion reactions. Moreover, the study highlights the importance of resolving controversies surrounding metal–support interactions for rational catalyst design. Overall, the study underscores the pivotal role of nanotechnology in shaping the future of methane utilization and sustainable energy production, providing valuable insights for guiding future research directions and technological developments in this field.
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Open AccessArticle
Dry Reforming of CH4 Using a Microreactor
by
Tarsida N. Wedraogo, Jing Wu and Huai Z. Li
Methane 2024, 3(2), 346-358; https://doi.org/10.3390/methane3020019 - 3 Jun 2024
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In the present study, a comparison of the dry reforming of a gas mixture containing methane, carbon dioxide and nitrogen without contaminants to a ruthenium-based Ru/Al2O3 catalyst was carried out in a microreactor for the first time. The influence of
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In the present study, a comparison of the dry reforming of a gas mixture containing methane, carbon dioxide and nitrogen without contaminants to a ruthenium-based Ru/Al2O3 catalyst was carried out in a microreactor for the first time. The influence of the contact time, temperature and composition of the feed on the conversion was exhaustively investigated. The optimal operating conditions were found to be a contact time of 80 milliseconds, a temperature of 700 °C and a CH4:CO2 ratio of 1. The assessment of diffusional limitations reveals that there is no resistance to mass transfer, which reveals the potential benefit of the determination of intrinsic reaction kinetics within a microreactor.
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Open AccessArticle
A Study on the Heterogeneity and Anisotropy of the Porous Grout Body Created in the Stabilization of a Methane Hydrate Reservoir through Grouting
by
Yuchen Liu and Masanori Kurihara
Methane 2024, 3(2), 331-345; https://doi.org/10.3390/methane3020018 - 21 May 2024
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To solve the sand problem during the depressurization of methane hydrate (MH), we proposed a method to build a porous grout body with sufficient permeability and strength around the wellbore through inhibitor pre-injection and grouting, and verified its effectiveness and potential in our
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To solve the sand problem during the depressurization of methane hydrate (MH), we proposed a method to build a porous grout body with sufficient permeability and strength around the wellbore through inhibitor pre-injection and grouting, and verified its effectiveness and potential in our previous research using artificial cores created with silica sand and alternative hydrates such as TBAB- hydrate and iso-butane hydrate. However, all of the artificial cores mentioned above were created with high homogeneity, injected, cured, and had their physical properties measured in the vertical direction, which differs from real reservoir conditions. To investigate the effects of grouting in a more realistic fluid flow, we conducted further experiments using horizontal 1D cores, 1D cubic models, and a 2D cross-sectional model mimicking the near wellbore. These experiments revealed that (1) the generated gas somewhat suppressed the effects of grouting as in the case of previous experiments, and (2) grouted reservoirs would be heterogenous and anisotropic due to the fluid densities and the distribution of grout particles and turbidite sediments, but sufficient permeability and satisfactory strength could still be attained. The above series of experiments demonstrated that our method has the potential to effectively produce actual MH, preventing sand problems even in heterogeneous and anisotropic grouted reservoirs.
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Open AccessArticle
Methane Production from Sugarcane Vinasse Biodigestion: An Efficient Bioenergy and Environmental Solution for the State of São Paulo, Brazil
by
Letícia Rodrigues de Melo, Bruna Zerlotti Demasi, Matheus Neves de Araujo, Renan Coghi Rogeri, Luana Cardoso Grangeiro and Lucas Tadeu Fuess
Methane 2024, 3(2), 314-330; https://doi.org/10.3390/methane3020017 - 20 May 2024
Abstract
This study mapped the bioenergy production from sugarcane vinasse according to the mesoregions of the State of São Paulo (SP), Brazil, assessing the magnitude of biogas-derived electricity and biomethane production and estimating the greenhouse gas (GHG) emissions. SP holds 45% of the Brazilian
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This study mapped the bioenergy production from sugarcane vinasse according to the mesoregions of the State of São Paulo (SP), Brazil, assessing the magnitude of biogas-derived electricity and biomethane production and estimating the greenhouse gas (GHG) emissions. SP holds 45% of the Brazilian ethanol-producing plants, in which 1.4 million m3 of carbon-rich vinasse are generated daily. The electricity generated from vinasse has the potential to fully supply the residential consumption (ca. 6.5 million inhabitants) in the main sugarcane-producing mesoregions of the state (Ribeirão Preto, São José do Rio Preto, Bauru, Araçatuba and Presidente Prudente). In another approach, biomethane could displace almost 3.5 billion liters of diesel, which represents a 26% abatement in the annual state diesel consumption. Energetically exploiting biogas is mandatory to prevent GHG-related drawbacks, as the eventual emission of methane produced under controlled conditions (261.2 × 106 kg-CO2eq d−1) is ca. 7-fold higher than the total emissions estimated for the entire ethanol production chain. Meanwhile, replacing diesel with biomethane can avoid the emission of 45.4 × 106 kg-CO2eq d−1. Implementing an efficient model of energy recovery from vinasse in SP has great potential to serve as a basis for expanding the utilization of this wastewater in Brazil.
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(This article belongs to the Special Issue Trends in Methane-Based Biotechnology)
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Open AccessReview
Methane Advances: Trends and Summary from Selected Studies
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Stephen Okiemute Akpasi, Joseph Samuel Akpan, Ubani Oluwaseun Amune, Ayodeji Arnold Olaseinde and Sammy Lewis Kiambi
Methane 2024, 3(2), 276-313; https://doi.org/10.3390/methane3020016 - 1 May 2024
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The role of methane (CH4) in the 21st century presents a critical dilemma. Its abundance and clean-burning nature make it a promising energy source, while its potent greenhouse effect threatens climate stability. Despite its potent greenhouse gas (GHG) nature, CH4
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The role of methane (CH4) in the 21st century presents a critical dilemma. Its abundance and clean-burning nature make it a promising energy source, while its potent greenhouse effect threatens climate stability. Despite its potent greenhouse gas (GHG) nature, CH4 remains a crucial energy resource. However, advancements in CH4 capture, utilization, and emissions mitigation are rapidly evolving, necessitating a critical assessment of the advances, their potential, and challenges. This study aims to comprehensively evaluate the current state of the art in these advancements, particularly focusing on the emissions trends, with corresponding global warming potentials of projected CH4 emissions, and a discussion on the advances that have been made towards reducing the impacts of CH4 emissions. The areas of these advances include measurement, computational, numerical modeling, and simulation studies for CH4, emerging technologies for CH4 production, management and control, the nexus of CH4 –X, and case study applications in countries. This study reports on these advances, which involves a technical review of studies, mainly from the last decade, discussing the technical feasibility, economic viability, and environmental impact of these advancements. Our trend analysis reveals that even though the share of CH4 in the GHG mix has been around 19% compared with carbon dioxide (CO2), still, CH4 reduction would need to be highly subsidized because of the high global warming potential it has, compared with CO2. We conclude that while significant progress has been made, further research and development are essential to optimize the performance, scalability, and affordability of these advancements. Additionally, robust policy frameworks and international collaborations are crucial to ensure widespread adoption and maximize the potential that comes with the advancements in the mitigation of the impact of CH4 emission. This study contributes to the ongoing dialogue on balancing the potentials of CH4 with its environmental footprint, paving the way for a future where this versatile resource can be utilized sustainably.
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Open AccessFeature PaperArticle
Fungal Methane Production Controlled by Oxygen Levels and Temperature
by
Moritz Schroll, Katharina Lenhart, Thomas Bender, Piet Hötten, Alexander Rudolph, Sven Sörensen and Frank Keppler
Methane 2024, 3(2), 257-275; https://doi.org/10.3390/methane3020015 - 19 Apr 2024
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Saprotrophic fungi, key players in global carbon cycling, have been identified as methane (CH4) sources not yet accounted for in the global CH4 budget. This study, for the first time, explores the influence of oxygen (O2) and temperature
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Saprotrophic fungi, key players in global carbon cycling, have been identified as methane (CH4) sources not yet accounted for in the global CH4 budget. This study, for the first time, explores the influence of oxygen (O2) and temperature on CH4 production by two fungi, Laetiporus sulphureus and Pleurotus sapidus. To explore the relationship between these parameters and fungal CH4 formation, we examined CH4 formation under varying O2 levels (0 to 98%) and temperatures (17, 27, and 40 °C) during fungal growth on pine wood, beech wood, and grass under sterile conditions. Our findings show that fungal CH4 formation strongly depends on O2 levels. Methane formation was highest when O2 levels exceeded 5%, whilst no CH4 formation was observed after complete O2 consumption. Reintroducing O2 immediately resumed fungal CH4 production. Methane formation normalized to O2 consumption (CH4_norm) showed a different pattern. L. sulphureus showed higher CH4_norm rates with higher O2 levels, whereas P. sapidus showed elevated rates between 0 and 5%. Temperature also significantly influenced CH4 and CH4_norm rates, with the highest production at 27 °C, and comparatively lower rates at 17 and 40 °C. These findings demonstrate the importance of O2 levels and temperature in fungal CH4 emissions, which are essential for refining CH4 source predictions.
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Open AccessReview
A Comprehensive Review of the Strategies to Improve Anaerobic Digestion: Their Mechanism and Digestion Performance
by
Xiaoyong Li, Zhi Wang, Yun He, Yuzhong Wang, Shilei Wang, Zehui Zheng, Songtao Wang, Jingliang Xu, Yafan Cai and Hanjie Ying
Methane 2024, 3(2), 227-256; https://doi.org/10.3390/methane3020014 - 15 Apr 2024
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Low and unstable digestion performance is a challenging issue for anaerobic digestion, which prompts researchers to develop new strategies. In addition to traditional approaches such as co-digestion, pre-treatment, and recirculation, some emerging strategies, namely additive processes and microaeration, have also been recognized and
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Low and unstable digestion performance is a challenging issue for anaerobic digestion, which prompts researchers to develop new strategies. In addition to traditional approaches such as co-digestion, pre-treatment, and recirculation, some emerging strategies, namely additive processes and microaeration, have also been recognized and developed in recent years. Many studies have evaluated the effect of these strategies on digestion performance. However, their comprehensive analysis is lacking, especially regarding the mechanisms of the different strategies. This review presents a comprehensive overview of research progress on these strategies based on the latest research, considering the five main strategies listed above. Through critical thinking, a summary of their mechanism, reactor performance, and availability of these strategies is presented. The results demonstrate that the contribution of microaeration is mainly to balance the composition and activity of hydrolysis, acidogenesis, and methanogenic archaea. Recirculation and co-digestion mainly balance mass and reaction environments. Pre-treatment, such as removing lignin, reducing cellulose crystallinity, and increasing the substrate-specific surface area, makes the characteristics of the substrate more conducive to the digestion of microorganisms. The mechanism of additive strategies varies greatly depending on the type of additive, such as enhancing interspecies electron transfer through conductive materials, resisting adverse digestion conditions through functional microbial additives, and accelerating nutrient absorption by regulating the bioavailability of trace elements. Although these strategies have different mechanisms for promoting digestion performance, their ultimate effect is to allow the parameters of the reactor to reach an ideal status and then achieve a balance among the substance, microorganisms, and water in an anaerobic reactor.
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Open AccessArticle
Thermochemical Pretreatment for Improving the Psychrophilic Anaerobic Digestion of Coffee Husks
by
Tzyy Shyuan Yang, Carla Flores-Rodriguez, Lorena Torres-Albarracin and Ariovaldo José da Silva
Methane 2024, 3(2), 214-226; https://doi.org/10.3390/methane3020013 - 29 Mar 2024
Abstract
Psychrophilic anaerobic digestion emerges as an appealing integrated solution for the management of agricultural waste, particularly for farmers in regions where the average temperature does not exceed 26 °C, as seen in coffee cultivation. Therefore, this study seeks to assess the biomethane potential
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Psychrophilic anaerobic digestion emerges as an appealing integrated solution for the management of agricultural waste, particularly for farmers in regions where the average temperature does not exceed 26 °C, as seen in coffee cultivation. Therefore, this study seeks to assess the biomethane potential of thermochemical-treated coffee husk through psychrophilic anaerobic digestion (C3-20 °C-w/pretreatment). To examine its viability, outcomes were compared with reactors operating at both mesophilic (C1-35 °C) and psychrophilic (C2-20 °C) conditions, albeit without the use of pretreated coffee husk. The C3-20 °C-w/pretreatment test demonstrated a 36.89% increase (150.47 NmL CH4/g VS; 161.04 NmL CH4/g COD), while the C1-35 °C test exhibited a 24.03% increase (124.99 NmL CH4/g VS; 133.77 NmL CH4/g COD), both in comparison to the C2-20 °C test (94.96 NmL CH4/g VS; 101.63 NmL CH4/g COD). Notably, the C3-20 °C-w/pretreatment trial yielded superior outcomes, accompanied by an associated energy output of 3199.25 GWh/year, sufficient to meet the annual energy demands of 494 residences. This marks an increase of 83 and 182 million residences compared to the mesophilic and psychrophilic AD of CH without pretreatment, respectively.
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(This article belongs to the Special Issue Anaerobic Digestion Process: Converting Waste to Energy)
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Open AccessArticle
Energy Security Blind Spots of Gas, Oil, and Coal Exporters
by
Andrew Curtis and Benjamin McLellan
Methane 2024, 3(1), 191-213; https://doi.org/10.3390/methane3010012 - 12 Mar 2024
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The global narrative around domestic energy security is dominated by the paradigm of import-dependent countries, and as a result the interactions of energy export activities with domestic energy systems are not generally considered. In this paper, we apply a systems approach to establish
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The global narrative around domestic energy security is dominated by the paradigm of import-dependent countries, and as a result the interactions of energy export activities with domestic energy systems are not generally considered. In this paper, we apply a systems approach to establish two potential blind spots in evaluating the whole-of-system energy security of energy resource exporters (actual primary energy self-sufficiency and export exposure of the domestic energy system), and examine some case studies, primarily in the Australian context, to validate the existence of these blind spots. The commencement of LNG exports from the state of Queensland is examined in detail. Furthermore, we propose two novel quantitative indicators to mitigate the blind spots established. First, a revised method is proposed to calculate energy self-sufficiency, showing for the exporters studied a less secure position than shown by the traditional method. Second, an indicator is proposed to quantify the extent of exposure of the domestic energy system to international markets through export linkages, which we have applied to Australia’s domestic energy system, showing the extent of the increase in international exposure since LNG exports from Queensland commenced in 2015–2016. Conclusions of this paper include the realization that domestic energy security for energy exporters, such as Australia and the other countries examined, is more complex and, in the cases examined, less secure than importer-oriented energy security frameworks have previously recognized. A further conclusion is established that the decoupling of energy resource exports from the domestic energy system through transition to a zero-carbon energy system based on domestic renewable energy sources can be an effective means of improving Australia’s energy security.
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Open AccessReview
Exploring Geochemical Signatures in Production Water: Insights from Coal Bed Methane and Shale Gas Exploration—A Brief Review
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Santanu Ghosh, Tushar Adsul, Balram Tiwari, Dinesh Kumar and Atul Kumar Varma
Methane 2024, 3(1), 172-190; https://doi.org/10.3390/methane3010011 - 4 Mar 2024
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This article furnishes a brief review of the geochemistry of waters produced during coal bed methane and shale gas exploration. Stable deuterium and oxygen isotopes of produced waters, as well as the stable carbon isotope of dissolved inorganic carbon in these waters, are
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This article furnishes a brief review of the geochemistry of waters produced during coal bed methane and shale gas exploration. Stable deuterium and oxygen isotopes of produced waters, as well as the stable carbon isotope of dissolved inorganic carbon in these waters, are influenced by groundwater recharge, methanogenic pathways, the mixing of formation water with saline water, water–rock interactions, well completion, contamination from water from adjacent litho-units, and coal bed dewatering, among many others. Apart from the isotopic fingerprints, significant attention should be given to the chemistry of produced waters. These waters comprise natural saturated and aromatic organic functionalities, metals, radioisotopes, salts, inorganic ions, and synthetic chemicals introduced during hydraulic fracturing. Hence, to circumvent their adverse environmental effects, produced waters are treated with several technologies, like electro-coagulation, media filtration, the coupling of chemical precipitation and dissolved air flotation, electrochemical Fe+2/HClO oxidation, membrane distillation coupled with the walnut shell filtration, etc. Although produced water treatment incurs high costs, some of these techniques are economically feasible and sustain unconventional hydrocarbon exploitation.
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Open AccessFeature PaperArticle
Effect of Particle Size on the Biomethanation Kinetics of Mechanically Pretreated Sargassum spp. Biomass
by
Rosy Paletta, Rossella Girimonte, Yessica A. Castro, Jose Atilio De Frias and Vincenza Calabrò
Methane 2024, 3(1), 160-171; https://doi.org/10.3390/methane3010010 - 4 Mar 2024
Abstract
The collection and use of Sargassum spp. as feedstock for the production of valuable products such as biomethane by anaerobic digestion (AD) would mitigate the negative impact of the blooms and the costs related to waste management in the Dominican Republic. In this
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The collection and use of Sargassum spp. as feedstock for the production of valuable products such as biomethane by anaerobic digestion (AD) would mitigate the negative impact of the blooms and the costs related to waste management in the Dominican Republic. In this work, the effect of the particle size of pelagic Sargassum spp. biomass, as a result of mechanical pretreatments, on the biomethanation was determined. The granulometric analysis of the mechanically pre-treated biomass was carried out using a Mastersize2000. The Biochemical Methane Potential (BMP) of the samples was determined using an Automatic Potential System Test II (AMPTS® II). The kinetic parameters of the reaction were scientifically evaluated by using First order kinetic Model and modified Gompertz Model. The granulometric analysis showed a monomodal distribution on crushed biomass (505 µm) and a bimodal distribution on the milling sample (107 µm). The bimodal biomass means the biomass is characterized by the presence of fine and large particles. We observed that BMP increased by 78.85% when particles were reduced from 50,000 µm to 505 µm and by 73.61% when particles were reduced from 50,000 µm to 107 µm. A low methane yield from the milling biomass (107 µm) compared to the crushed biomass (505 µm) could be related to the excessive reduction of particle size. The fine particles are subject to the formation of aggregates and consequently, the contact area between the algae cells and the microorganisms that operate the anaerobic digestion process decreases.
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(This article belongs to the Special Issue Anaerobic Digestion Process: Converting Waste to Energy)
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Open AccessArticle
Use of Increasing Levels of Low-Quality Forage in Dairy Cows’ Diets to Regulate Enteric Methane Production in Subtropical Regions
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Mohammed Benaouda, Manuel González-Ronquillo, Francisca Avilés-Nova, Reynaldo Zaragoza-Guerrero, Juan Carlos Ku-Vera and Octavio Alonso Castelán-Ortega
Methane 2024, 3(1), 149-159; https://doi.org/10.3390/methane3010009 - 22 Feb 2024
Abstract
Dairy cows are the highest daily and annual methane (CH4) producers among all cattle categories. So, the present study aimed to evaluate the effect of increasing supplementation levels of a low-quality forage on dry matter intake (DMI), DM digestibility (DMD), milk
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Dairy cows are the highest daily and annual methane (CH4) producers among all cattle categories. So, the present study aimed to evaluate the effect of increasing supplementation levels of a low-quality forage on dry matter intake (DMI), DM digestibility (DMD), milk production, enteric CH4 emission, gross energy, and protein partitioning in Holstein cows. In total, eight cows (112 ± 38 days postpartum; mean ± s.d.) were randomly assigned to 4 treatments composed of 4 dietary neutral detergent fibre (NDF) inclusion levels (40.2% (control), 43.3%, 46.5%, and 50.5%) in a 4 × 4 repeated Latin square experimental design. The cows were fed corn + alfalfa silage and a concentrate (60:40 forage:concentrate ratio). To increase the contents of low-quality NDF, part of the silage was replaced with maize stover (MSTV). The CH4 production was measured in an open-circuit respiration chamber. The DMI increased significantly and linearly (p < 0.05) with increasing levels of MSTV. However, the CH4 yield decreased (p < 0.0001) as the NDF level increased (32.1, 28.1, 23.1, and 21.3 CH4 L/kg DMI, respectively). DMD decreased as NDF levels in the diet increased (p < 0.0001). The NDF digestibility (DNDF) explained the better (p < 0.0001) CH4 production response than DMD. It was concluded that low-quality forages can be used to regulate CH4 production in subtropical and tropical climate regions.
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Open AccessFeature PaperReview
Methane Biofiltration Processes: A Summary of Biotic and Abiotic Factors
by
Fatemeh Ahmadi, Tatiana Bodraya and Maximilian Lackner
Methane 2024, 3(1), 122-148; https://doi.org/10.3390/methane3010008 - 21 Feb 2024
Cited by 1
Abstract
The ongoing yearly rise in worldwide methane (CH4) emissions is mostly due to human activities. Nevertheless, since over half of these emissions are scattered and have a concentration of less than 3% (v/v), traditional physical–chemical methods are
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The ongoing yearly rise in worldwide methane (CH4) emissions is mostly due to human activities. Nevertheless, since over half of these emissions are scattered and have a concentration of less than 3% (v/v), traditional physical–chemical methods are not very effective in reducing them. In this context, biotechnologies like biofiltration using methane-consuming bacteria, also known as methanotrophs, offer a cost-efficient and practical approach to addressing diffuse CH4 emissions. The present review describes recent findings in biofiltration processes as one of the earliest biotechnologies for treating polluted air. Specifically, impacts of biotic (such as cooperation between methanotrophs and non-methanotrophic bacteria and fungi) and abiotic factors (such as temperature, salinity, and moisture) that influence CH4 biofiltration were compiled. Understanding the processes of methanogenesis and methanotrophy holds significant importance in the development of innovative agricultural practices and industrial procedures that contribute to a more favourable equilibrium of greenhouse gases. The integration of advanced genetic analyses can enable holistic approaches for unravelling the potential of biological systems for methane mitigation. This study pioneers a holistic approach to unravelling the biopotential of methanotrophs, offering unprecedented avenues for biotechnological applications.
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(This article belongs to the Special Issue Trends in Methane-Based Biotechnology)
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Open AccessArticle
Genetical and Biochemical Basis of Methane Monooxygenases of Methylosinus trichosporium OB3b in Response to Copper
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Dipayan Samanta, Tanvi Govil, Priya Saxena, Lee Krumholz, Venkataramana Gadhamshetty, Kian Mau Goh and Rajesh K. Sani
Methane 2024, 3(1), 103-121; https://doi.org/10.3390/methane3010007 - 20 Feb 2024
Abstract
Over the past decade, copper (Cu) has been recognized as a crucial metal in the differential expression of soluble (sMMO) and particulate (pMMO) forms of methane monooxygenase (MMO) through a mechanism referred to as the “Cu switch”. In this study, we used Methylosinus
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Over the past decade, copper (Cu) has been recognized as a crucial metal in the differential expression of soluble (sMMO) and particulate (pMMO) forms of methane monooxygenase (MMO) through a mechanism referred to as the “Cu switch”. In this study, we used Methylosinus trichosporium OB3b as a model bacterium to investigate the range of Cu concentrations that trigger the expression of sMMO to pMMO and its effect on growth and methane oxidation. The Cu switch was found to be regulated within Cu concentrations from 3 to 5 µM, with a strict increase in the methane consumption rates from 3.09 to 3.85 µM occurring on the 6th day. Our findings indicate that there was a decrease in the fold changes in the expression of methanobactin (Mbn) synthesis gene (mbnA) with a higher Cu concentration, whereas the Ton-B siderophore receptor gene (mbnT) showed upregulation at all Cu concentrations. Furthermore, the upregulation of the di-heme enzyme at concentrations above 5 µM Cu may play a crucial role in the copper switch by increasing oxygen consumption; however, the role has yet not been elucidated. We developed a quantitative assay based on the naphthalene–Molisch principle to distinguish between the sMMO- and pMMO-expressing cells, which coincided with the regulation profile of the sMMO and pMMO genes. At 0 and 3 µM Cu, the naphthol concentration was higher (8.1 and 4.2 µM, respectively) and gradually decreased to 0 µM naphthol when pMMO was expressed and acted as the sole methane oxidizer at concentrations above 5 µM Cu. Using physical protein–protein interaction, we identified seven transporters, three cell wall biosynthesis or degradation proteins, Cu resistance operon proteins, and 18 hypothetical proteins that may be involved in Cu toxicity and homeostasis. These findings shed light on the key regulatory genes of the Cu switch that will have potential implications for bioremediation and biotechnology applications.
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(This article belongs to the Special Issue Trends in Methane-Based Biotechnology)
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Open AccessReview
Research Progress on Stability Control on Ni-Based Catalysts for Methane Dry Reforming
by
Minghui Wei and Xuerong Shi
Methane 2024, 3(1), 86-102; https://doi.org/10.3390/methane3010006 - 6 Feb 2024
Cited by 1
Abstract
CO2 reforming of CH4 (DRM) utilizes the greenhouse gases of CH4 and CO2 to obtain the synthesis gas, benefiting the achievement of carbon neutrality. However, the deactivation of Ni-based catalysts caused by sintering and carbon deposition limits the industrial
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CO2 reforming of CH4 (DRM) utilizes the greenhouse gases of CH4 and CO2 to obtain the synthesis gas, benefiting the achievement of carbon neutrality. However, the deactivation of Ni-based catalysts caused by sintering and carbon deposition limits the industrial application. Focusing on stability improvement, this review first summarizes the reaction mechanism and deactivation mechanism in DRM and then discusses the impact of catalyst active components, supports, and interfacial structure. Finally, we propose the design direction of stable Ni-based catalysts towards DRM, providing guidance for the future development of catalysts suitable for industrial production.
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(This article belongs to the Special Issue Methane Dry Reforming)
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Open AccessArticle
Towards a Mechanistic Understanding of the Slagging Propensities of Petroleum Coke: Lessons Learned from Its Co-Combustion with Natural Gas in Oxygen-Enriched Atmospheres
by
Nghia Duc Tin Nguyen and Gautham Krishnamoorthy
Methane 2024, 3(1), 65-85; https://doi.org/10.3390/methane3010005 - 24 Jan 2024
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A Computational Fluid Dynamic study was carried out to match the measured outer ash deposition rates associated with the combustion of petroleum coke (PC)–natural gas in AIR and O2/CO2 (70/30 vol%, OXY70). The fly ash PSD associated with high-fixed-carbon, non-porous
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A Computational Fluid Dynamic study was carried out to match the measured outer ash deposition rates associated with the combustion of petroleum coke (PC)–natural gas in AIR and O2/CO2 (70/30 vol%, OXY70). The fly ash PSD associated with high-fixed-carbon, non-porous fuel was estimated using a shrinking sphere burnout model and employed in conjunction with particle kinetic energy (PKE), particle viscosity (µP), and a critical Weber-number-based capture criterion. Deposition rate predictions were sensitive to the fly ash composition employed for estimating µP due to the significant enrichment of Fe in the deposits. Predictions were insensitive to the specific µP model formulation employed or whether the V2O5 in the ash was assumed to play the role of a glass former or a glass modifier. OXY70 scenario impaction rates were significantly lower than the measured deposition rates when the fly ash PSD associated with the AIR scenario was employed in the calculations. This necessitated an ad hoc modification of the OXY70 fly ash PSD to a coarser range to match the measurements and attributing it to agglomeration resulting from longer residence times and higher temperatures. This shift in PSD was in line with AIR and OXY70 fly ash PSD measurements reported previously.
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Open AccessArticle
High-Pressure Hydrogenation: A Path to Efficient Methane Production from CO2
by
Maitê L. Gothe, Adolfo L. Figueredo, Laís R. Borges, Ruben Ramos, Andreia F. Peixoto and Pedro Vidinha
Methane 2024, 3(1), 53-64; https://doi.org/10.3390/methane3010004 - 15 Jan 2024
Cited by 1
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Methane has a rather relevant role in the “Power-to-Gas” concept, which is central in the current paradigm of climate change and renewable energies. Methane, the main component of natural gas, can be produced by catalytic hydrogenation reactions, particularly of CO2. A
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Methane has a rather relevant role in the “Power-to-Gas” concept, which is central in the current paradigm of climate change and renewable energies. Methane, the main component of natural gas, can be produced by catalytic hydrogenation reactions, particularly of CO2. A very effective catalyst in this reaction, hydrotalcite-derived nickel nanoparticles supported on alumina, Ni/Al2O3-HTC, can be employed in a high-pressure flow reactor to convert CO2 and H2 into CH4 at 100% selectivity and 84% conversion, whereas at atmospheric pressure, methane can be obtained with up to 90% selectivity. The high-pressure aspect also allows fast-paced production—over 5 m3·h−1·kgcat−1 of CH4 can be generated.
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Open AccessReview
A Review on Dry Anaerobic Digestion: Existing Technologies, Performance Factors, Challenges, and Recommendations
by
Umer Hayyat, Muhammad Usman Khan, Muhammad Sultan, Umair Zahid, Showkat Ahmad Bhat and Mohd Muzamil
Methane 2024, 3(1), 33-52; https://doi.org/10.3390/methane3010003 - 15 Jan 2024
Abstract
With the increase in the growing rate of municipal solid waste throughout the world and due to the high moisture and organic components of the organic fraction of municipal solid waste, dry anaerobic digestion has become the future direction to cope with this
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With the increase in the growing rate of municipal solid waste throughout the world and due to the high moisture and organic components of the organic fraction of municipal solid waste, dry anaerobic digestion has become the future direction to cope with this waste while reducing the impact on the environment, including climate change. Dry anaerobic digestion has become a promising technology that converts the organic fraction of municipal solid waste into combustible biogases, which can be used as an alternative energy source. However, the technology faces several challenges that must be addressed to enhance its performance and adoption. This paper provides a comprehensive analysis of the current technologies used for dry anaerobic digestion in OFMSW and delves into the various factors that influence the performance of these technologies. This review paper also identifies and discusses the challenges faced in optimizing and scaling up these technologies, such as feedstock pretreatment requirements, characteristics of inoculum, and other crucial parameters.
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(This article belongs to the Special Issue Anaerobic Digestion Process: Converting Waste to Energy)
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Open AccessFeature PaperArticle
The Trade-Off between Enteric and Manure Methane Emissions and Their Bacterial Ecology in Lactating Cows Fed Diets Varying in Forage-to-Concentrate Ratio and Rapeseed Oil
by
Babak Darabighane, Ilma Tapio, Saija Rasi, Ari-Matti Seppänen, Lucia Blasco, Seppo Ahvenjärvi and Ali R. Bayat
Methane 2024, 3(1), 12-32; https://doi.org/10.3390/methane3010002 - 9 Jan 2024
Cited by 1
Abstract
An experiment was conducted to examine how dietary interventions reducing enteric methane (CH4) emissions influence manure CH4 emissions in biogas production (as biochemical methane potential (BMP)) or under static conditions mimicking natural manure storage conditions. Experimental treatments consisted of a
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An experiment was conducted to examine how dietary interventions reducing enteric methane (CH4) emissions influence manure CH4 emissions in biogas production (as biochemical methane potential (BMP)) or under static conditions mimicking natural manure storage conditions. Experimental treatments consisted of a factorial arrangement of high (HF: 0.65) or low (LF: 0.35) levels of forage and 0 or 50 g of rapeseed oil per kg of diet dry matter. Oil supplementation reduced daily enteric CH4 emissions, especially in the HF diet, by 20%. Greater dietary concentrate proportion reduced CH4 yield and intensity (6 and 12%, respectively) and decreased pH, increased total volatile fatty acids, and molar proportions of butyrate and valerate in feces incubated under static conditions. Oil supplementation increased daily BMP and BMP calculated per unit of organic matter (OM) (17 and 15%, respectively). Increased dietary concentrate had no impact on daily BMP and BMP per unit of OM, whereas it reduced daily CH4 production by 89% and CH4 per unit of OM by 91% under static conditions. Dietary oil supplementation tended to decrease fecal CH4 production per unit of digestible OM (23%) under static conditions. Diets had no impact on the alpha diversity of ruminal prokaryotes. After incubation, the fecal prokaryote community was significantly less diverse. Diets had no effect on alpha diversity in the BMP experiment, but static trial fecal samples originating from the HF diet showed significantly lower diversity compared with the LF diet. Overall, the tested dietary interventions reduced enteric CH4 emissions and reduced or tended to reduce manure CH4 emissions under static conditions, indicating a lack of trade-off between enteric and manure CH4 emissions. The potential for increasing CH4 yields in biogas industries due to dietary interventions could lead to a sustainable synergy between farms and industry.
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(This article belongs to the Special Issue Anaerobic Digestion Process: Converting Waste to Energy)
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