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 20.1 days after submission; acceptance to publication is undertaken in 18.9 days (median values for papers published in this journal in the first half of 2024).
- Recognition of Reviewers: APC discount vouchers, optional signed peer review, and reviewer names published annually in the journal.
Latest Articles
Rapid Screening of Methane-Reducing Compounds for Deployment in Livestock Drinking Water Using In Vitro and FTIR-ATR Analyses
Methane 2024, 3(4), 533-560; https://doi.org/10.3390/methane3040030 - 8 Oct 2024
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Several additives have been shown to reduce enteric methane emissions from ruminants when supplied in feed. However, utilising this method to deliver such methane-reducing compounds (MRCs) in extensive grazing systems is challenging. Use of livestock drinking water presents a novel method to deliver
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Several additives have been shown to reduce enteric methane emissions from ruminants when supplied in feed. However, utilising this method to deliver such methane-reducing compounds (MRCs) in extensive grazing systems is challenging. Use of livestock drinking water presents a novel method to deliver MRCs to animals in those systems. This work evaluated 13 MRCs for suitability to be deployed in this manner. Compounds were analysed for solubility and stability in aqueous solution using Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Furthermore, aqueous solutions of MRCs were subjected to variations in temperature and starting pH of water used to assess solubility and stability of the MRCs in simulated water trough conditions, also using FTIR-ATR spectroscopy. In vitro batch culture fermentations were carried out using a medium-quality tropical grass feed substrate, to simulate pastures consumed by cattle in extensive grazing systems. Measurements were made of total gas and methane production, in vitro dry matter digestibility (IVDMD), and volatile fatty acid (VFA) concentration. Of the MRCs tested, 12 were found to be soluble and stable in water using the FTIR method employed, whilst the other could not be measured. Of the 12 soluble and stable MRCs, one containing synthetic tribromomethane (Rumin8 Investigational Veterinary Product) reduced methane production by 99% (p = 0.001) when delivered aqueously in vitro, without a reduction in IVDMD (p = 0.751), with a shift towards decreased acetate and increased propionate production and decreased total VFA production (p < 0.001). Other compounds investigated also appeared suitable, and the methods developed in this study could be used to guide future research in the area.
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Open AccessReview
Biohydrogen Produced via Dark Fermentation: A Review
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Marcela Moreira Albuquerque, Gabriela de Bona Sartor, Walter Jose Martinez-Burgos, Thamarys Scapini, Thiago Edwiges, Carlos Ricardo Soccol and Adriane Bianchi Pedroni Medeiros
Methane 2024, 3(3), 500-532; https://doi.org/10.3390/methane3030029 - 14 Sep 2024
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Hydrogen (H2) is a highly efficient and clean energy source with the potential for renewable energy. The production of H2 from biological routes such as biophotolysis, photofermentation, dark fermentation, and bioelectrochemical production is characterized as a renewable alternative to current
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Hydrogen (H2) is a highly efficient and clean energy source with the potential for renewable energy. The production of H2 from biological routes such as biophotolysis, photofermentation, dark fermentation, and bioelectrochemical production is characterized as a renewable alternative to current production, which is mainly based on energy-intensive electrochemical and thermochemical processes and responsible for the emission of high amounts of environmentally harmful compounds. Dark fermentation is the most efficient and cost-effective method for producing biohydrogen, making it a key research focus. This article offers a comprehensive overview of the dark fermentation process with the aim of enhancing hydrogen productivity and yields. Aspects related to the main substrates used, the inoculum sources and their pretreatment, and physical-chemical parameters of the process are covered. Furthermore, this manuscript addresses topics such as process integration, genetic and metabolic engineering of fermentative microorganisms, and the main types of bioreactors aimed at greater yields and productivity of biohydrogen to enable its production through dark fermentation on a larger scale.
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Open AccessArticle
Development of Artificial Intelligence/Machine Learning (AI/ML) Models for Methane Emissions Forecasting in Seaweed
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Clifford Jaylen Louime and Tariq Asleem Raza
Methane 2024, 3(3), 485-499; https://doi.org/10.3390/methane3030028 - 4 Sep 2024
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This research project aimed to address the growing concern about methane emissions from seaweed by developing a Convolutional Neural Network (CNN) model capable of accurately predicting these emissions. The study used PANDAS to read and analyze the dataset, incorporating statistical measures like mean,
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This research project aimed to address the growing concern about methane emissions from seaweed by developing a Convolutional Neural Network (CNN) model capable of accurately predicting these emissions. The study used PANDAS to read and analyze the dataset, incorporating statistical measures like mean, median, and standard deviation to understand the dataset. The CNN model was trained using the ReLU activation function and mean absolute error as the loss function. The model performance was evaluated through MAPE graphs, comparing the mean absolute percentage error (MAPE) between training and validation sets and between true and predicted emissions, and analyzing trends in yearly greenhouse gas emissions. The results demonstrated that the CNN model achieved a high level of accuracy in predicting methane emissions, with a low MAPE between the expected and actual values. This approach should enhance our understanding of methane emissions from Sargassum, contributing to more accurate environmental impact assessments and effective mitigation strategies.
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Open AccessFeature PaperReview
Copper-Based Metal–Organic Frameworks Applied as Electrocatalysts for the Electroreduction of Carbon Dioxide (CO2ER) to Methane: A Review
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Jesús Antonio Cruz-Navarro, Fabiola Hernández-García, Arturo T. Sánchez-Mora, María Esther Moreno-Narváez, Viviana Reyes-Márquez, Raúl Colorado-Peralta and David Morales-Morales
Methane 2024, 3(3), 466-484; https://doi.org/10.3390/methane3030027 - 27 Aug 2024
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The electrochemical reduction of carbon dioxide (CO2) to methane (CH4) holds tremendous potential in mitigating greenhouse gas emissions and producing renewable fuels. Thus, this review provides a comprehensive overview of the utilization of copper-based metal–organic frameworks (Cu-MOFs) as catalysts
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The electrochemical reduction of carbon dioxide (CO2) to methane (CH4) holds tremendous potential in mitigating greenhouse gas emissions and producing renewable fuels. Thus, this review provides a comprehensive overview of the utilization of copper-based metal–organic frameworks (Cu-MOFs) as catalysts for this transformative process. Diverse key aspects of Cu-MOFs that make them ideal candidates for CO2 reduction are discussed, including their high surface areas, tunable pore sizes, and customizable active sites. Furthermore, recent advances in the design and synthesis of Cu-MOFs tailored specifically for enhanced catalytic activity and selectivity towards CH4 production are highlighted. Additionally, mechanistic insights into the CO2 reduction process on Cu-MOF catalysts are examined. Moreover, the recent application of diverse Cu-MOFs and derived materials in electrochemical reduction systems is discussed, and future research directions and potential applications of Cu-MOFs in sustainable energy conversion technologies are outlined. Thus, this review provides valuable insights into the current state of the art and the prospects for utilizing Cu-MOFs as efficient catalysts for the electrochemical conversion of CO2 to CH4, offering a pathway towards a greener and more sustainable energy future.
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Open AccessCommunication
Sub-Antarctic Macroalgae as Feed Ingredients for Sustainable Ruminant Production: In Vitro Total Gas and Methane Production
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Lizbeth E. Robles-Jimenez, Navid Ghavipanje, Ashley Ulloa, Ali Rivero, Pablo Gallardo and Manuel Gonzalez Ronquillo
Methane 2024, 3(3), 456-465; https://doi.org/10.3390/methane3030026 - 27 Aug 2024
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The sustainable meeting of the global quest for ruminant intensification dictates the need to identify alternative, eco-friendly, and safe feed ingredients. In this sense, macroalgae offer a new paradigm in sustainable ruminant feed supply. This study aimed to investigate the potential of sub-Antarctic
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The sustainable meeting of the global quest for ruminant intensification dictates the need to identify alternative, eco-friendly, and safe feed ingredients. In this sense, macroalgae offer a new paradigm in sustainable ruminant feed supply. This study aimed to investigate the potential of sub-Antarctic macroalgae, including Lessonia flavicans, Macrocystis pyrifera, Gigartina skottbergii, and Ulva Lactuca, regarding their chemical composition, in vitro gas production, and CH4 production. A completely randomized design consisted of a 96 h (h) incubation that included four different species and a control (alfalfa hay) with buffered rumen fluid. In vitro total gas, fermentation characteristics, and CH4 production were evaluated. The highest and the lowest crude protein (CP) contents were for U. lactuca (185.9 g/kg) and G. skottsbergi (86 g/kg), respectively (p < 0.0001). All macroalage had lower levels of natural detergent fiber (NDF) and acid detergent fiber (ADF) compared to alfalfa hay (p < 0.0001). The highest potential of gas production (b) was for M. pyriphera (162.8 mL gas/g DM), followed by alfalfa (119.3 mL gas/g DM). However, G. skottsbergi and M. pyriphera showed the highest dry matter degradability at 96 h (68.49 and 67.62 mg/100 mg, respectively; p < 0.0001) and microbial crude protein (679.8 and 669.8 mg/g, respectively, p < 0.0001). All four tested algae produced lower amounts of methane compared to alfalfa hay (p < 0.0001). After 24 h of incubation, M. pyriphera, L. flavicons, G. skottsbergi, and U. lactuca reduced CH4 by 99.7%, 98.6%, 92.9%, and 79.8%, respectively, when compared with the control. Also, all tested algae had lower (p = 0.0001) CH4 production (ml CH4/g Dry matter degradability, DMD) than alfalfa hay. The current results suggest that M. pyriphera and L. flavicons are promising feed additives for ruminants with eco-friendly production and acceptable CP content and DMD that could effectively mitigate CH4 emissions. Overall, these findings suggest that macroalgae hold promise as a substitute feed source for sustaining ruminant production at the onset of global warming.
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Open AccessFeature PaperArticle
Rapid Screening of Methane-Reducing Compounds for Deployment via Water with a Commercial Livestock Supplement Using In Vitro and FTIR-ATR Analyses
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Ryan J. Batley, Elieder Prates Romanzini, Joel B. Johnson, William Luiz de Souza, Mani Naiker, Mark G. Trotter, Simon P. Quigley, Guilhermo Francklin de Souza Congio and Diogo Fleury Azevedo Costa
Methane 2024, 3(3), 437-455; https://doi.org/10.3390/methane3030025 - 2 Aug 2024
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The addition of methane-reducing compounds (MRCs) to livestock drinking water presents an alternative method for enteric methane mitigation in extensive systems where these compounds cannot be fed through the diet. This work evaluated several such compounds with the potential to be deployed in
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The addition of methane-reducing compounds (MRCs) to livestock drinking water presents an alternative method for enteric methane mitigation in extensive systems where these compounds cannot be fed through the diet. This work evaluated several such compounds with the potential to be deployed in this manner. Methane-reducing compounds were selected based on the existing literature and likelihood of dissolution when combined with a commercially available water-based nutrient supplement (uPRO) (uPRO ORANGE®, DIT AgTech, QLD, Australia). This, in turn, would demonstrate the capacity for MRCs to be administered through animal drinking water when such supplements are in use. This technique requires the analysis of MRC solubility and stability in solution, which was completed via Fourier transform infrared-attenuated total reflectance spectroscopy. The uPRO supplement is comprised of urea, urea phosphate, and ammonium sulfate, providing nitrogen, phosphorus, and sulfur—limiting nutrients for ruminants grazing extensive systems during drier periods of the year. Accordingly, medium-quality Rhodes grass hay was used in fermentation runs to simulate a basal diet during the dry season. Methane-reducing compounds were assessed in accordance with each variable measured (gas/methane production, dry matter digestibility, stability under different environmental conditions) along with existing research in the field to determine the most suitable compound for co-administration. Whilst most compounds examined in this study appeared to retain their structure in solution with uPRO, fermentation results varied in terms of successful methane mitigation. The additive Agolin Ruminant L emerged as the most promising compound for further in vivo investigation.
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Open AccessFeature PaperArticle
Long-Term Anaerobic Structured Fixed-Bed Reactor Operation for Domestic Sewage Treatment: Performance and Metal Dynamics
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Julliana Alves da Silva, Adriana F. M. Braga, Larissa Quartaroli, Fernando G. Fermoso, Marcelo Zaiat and Gustavo H. R. da Silva
Methane 2024, 3(3), 421-436; https://doi.org/10.3390/methane3030024 - 30 Jul 2024
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To achieve optimal performance, anaerobic digestion (AD) requires well-balanced operation conditions, steady physical–chemical conditions, and adequate nutrient concentrations. The use of anaerobic structured-bed reactor (ASTBR) presents these conditions. However, several additional investigations are required to elucidate robustness to treat domestic sewage (DS). This
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To achieve optimal performance, anaerobic digestion (AD) requires well-balanced operation conditions, steady physical–chemical conditions, and adequate nutrient concentrations. The use of anaerobic structured-bed reactor (ASTBR) presents these conditions. However, several additional investigations are required to elucidate robustness to treat domestic sewage (DS). This pioneering study investigated the performance of an ASTBR in treating DS across four decreasing hydraulic retention times (HRTs) (12, 8, 6, and 5 h). The study aimed to assess organic matter removal, the influence on physical–chemical parameters, and the monitoring of trace metals (TMs) during long-term operation (614 days). Overall, the results underscore the viability of employing ASTBR for DS treatment, achieving an average chemical oxygen demand (COD) removal efficiency of 70%. The system demonstrated consistent long-term operation over 614 days, maintaining stability even with decreasing hydraulic retention times (HRTs). The average effluent concentration of volatile fatty acids (VFAs) was 20.4 ± 3.3 mg L−1, with a pH value averaging 7.2 ± 0.1. TM concentrations at an HRT of 12 h exhibited higher levels in the effluent compared to the influent, gradually decreasing over the course of operation and ultimately stabilizing at levels similar to those observed in the influent. The concentrations of metals, including Ba, Cr, Fe, Mn, Ni, Pb, Se, and Zn, monitored in the effluent samples adhered to the allowable discharge thresholds as stipulated by Brazilian regulations.
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Open AccessFeature PaperArticle
Application of Digestate from a Methane Fermentation Process for Supplying Water and Nutrients in Sweet Potato Cultivation in Sandy Soil
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Yoshiaki Kitaya, Siqinbatu, Ryosuke Endo and Toshio Shibuya
Methane 2024, 3(3), 410-420; https://doi.org/10.3390/methane3030023 - 4 Jul 2024
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To develop technology to efficiently utilize digestate from methane fermentation in agricultural production, the application of digestate from methane fermentation for supplying nutrients in sweet potato cultivation was investigated in sandy soil. Different strengths of diluted digestate with water were applied to sweet
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To develop technology to efficiently utilize digestate from methane fermentation in agricultural production, the application of digestate from methane fermentation for supplying nutrients in sweet potato cultivation was investigated in sandy soil. Different strengths of diluted digestate with water were applied to sweet potato plants as water and nutrient supplies to determine the appropriate strength of digestate from methane fermentation for sweet potato production in sandy soil. The growth of sweet potato cultivated with diluted digestate was also compared with that of sweet potato cultivated with a commercial chemical nutrient solution. The growth rate of the tuberous roots with the strength of 1/20 of the digestate was greatest among the treatments with different digestate strengths (1/80–1/2) and commercial nutrient solutions (1/4–1). Consequently, we proposed a sweet potato production system using a bottom irrigation method with digestate from methane fermentation, which will be applicable in semiarid regions. In conclusion, the results of this study can be effectively used in a regional agricultural system combined with a methane fermentation system and can contribute to increasing food production as well as the establishment of a resource recycling society.
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Open AccessFeature PaperArticle
Pathways toward Climate-Neutral Red Meat Production
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Bradley Ridoutt
Methane 2024, 3(3), 397-409; https://doi.org/10.3390/methane3030022 - 3 Jul 2024
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Ruminant livestock industries can support the climate stabilization ambitions of the Paris Agreement through interventions that reduce GHG emissions (predominantly biogenic methane) and sequester carbon in landscapes. This study explored pathways for the Australian red meat industry (grazing, feedlot finishing, and domestic processing)
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Ruminant livestock industries can support the climate stabilization ambitions of the Paris Agreement through interventions that reduce GHG emissions (predominantly biogenic methane) and sequester carbon in landscapes. This study explored pathways for the Australian red meat industry (grazing, feedlot finishing, and domestic processing) to become climate neutral, whereby the radiative forcing (RF) footprint is plateaued and there is no additional forcing contribution. Emissions timeseries (CO2, N2O, CH4) were compiled for 1990 to 2020 and projected to 2030 under a business-as-usual scenario (including an 18% increase in sheep and 13% increase in beef cattle) and with a range of production system and vegetation management interventions. The RF footprint peaked in 2018 at 7.13 mW/m2 and decreased to 7.07 mW/m2 in 2020. With the future expansion of the herd/flock and under business-as-usual conditions, the RF footprint is projected to increase by 2.8% by 2030. However, with a combination of interventions, production has the potential to increase with a decreasing RF footprint, a condition that can be described as climate neutral. The Australian red meat industry has made an historical contribution to global RF increase. However, with ongoing RF management, it is possible to increase food production within climate-neutral limits.
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Open AccessArticle
Photoperiod Regulates Aerobic Methane Emissions by Altering Plant Growth and Physiological Processes
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Mirwais M. Qaderi and Kate Burton
Methane 2024, 3(3), 380-396; https://doi.org/10.3390/methane3030021 - 28 Jun 2024
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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
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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
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Felipe Anchieta e Silva and Thenner Silva Rodrigues
Methane 2024, 3(2), 359-379; https://doi.org/10.3390/methane3020020 - 11 Jun 2024
Cited by 1
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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
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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
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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
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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
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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
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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.
Full article
(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
Cited by 1
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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
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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
Cited by 1
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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
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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
Cited by 4
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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
Cited by 1
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
Abstract
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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
by
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
Abstract
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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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