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Methane, Volume 3, Issue 3 (September 2024) – 9 articles

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33 pages, 1750 KiB  
Review
Biohydrogen Produced via Dark Fermentation: A Review
by 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
Viewed by 2452
Abstract
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 [...] Read more.
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. Full article
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15 pages, 3871 KiB  
Article
Development of Artificial Intelligence/Machine Learning (AI/ML) Models for Methane Emissions Forecasting in Seaweed
by Clifford Jaylen Louime and Tariq Asleem Raza
Methane 2024, 3(3), 485-499; https://doi.org/10.3390/methane3030028 - 4 Sep 2024
Viewed by 1007
Abstract
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, [...] Read more.
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. Full article
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19 pages, 3462 KiB  
Review
Copper-Based Metal–Organic Frameworks Applied as Electrocatalysts for the Electroreduction of Carbon Dioxide (CO2ER) to Methane: A Review
by 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
Viewed by 1454
Abstract
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 [...] Read more.
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. Full article
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10 pages, 251 KiB  
Communication
Sub-Antarctic Macroalgae as Feed Ingredients for Sustainable Ruminant Production: In Vitro Total Gas and Methane Production
by 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
Viewed by 1302
Abstract
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 [...] Read more.
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. Full article
19 pages, 5539 KiB  
Article
Rapid Screening of Methane-Reducing Compounds for Deployment via Water with a Commercial Livestock Supplement Using In Vitro and FTIR-ATR Analyses
by 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
Viewed by 1911
Abstract
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 [...] Read more.
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. Full article
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16 pages, 2029 KiB  
Article
Long-Term Anaerobic Structured Fixed-Bed Reactor Operation for Domestic Sewage Treatment: Performance and Metal Dynamics
by 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
Viewed by 783
Abstract
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 [...] Read more.
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. Full article
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11 pages, 5899 KiB  
Article
Application of Digestate from a Methane Fermentation Process for Supplying Water and Nutrients in Sweet Potato Cultivation in Sandy Soil
by Yoshiaki Kitaya, Siqinbatu, Ryosuke Endo and Toshio Shibuya
Methane 2024, 3(3), 410-420; https://doi.org/10.3390/methane3030023 - 4 Jul 2024
Viewed by 888
Abstract
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 [...] Read more.
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. Full article
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13 pages, 1434 KiB  
Article
Pathways toward Climate-Neutral Red Meat Production
by Bradley Ridoutt
Methane 2024, 3(3), 397-409; https://doi.org/10.3390/methane3030022 - 3 Jul 2024
Cited by 2 | Viewed by 1432
Abstract
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) [...] Read more.
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. Full article
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17 pages, 1727 KiB  
Article
Photoperiod Regulates Aerobic Methane Emissions by Altering Plant Growth and Physiological Processes
by Mirwais M. Qaderi and Kate Burton
Methane 2024, 3(3), 380-396; https://doi.org/10.3390/methane3030021 - 28 Jun 2024
Viewed by 1061
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 [...] Read more.
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. Full article
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