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Methane, Volume 3, Issue 4 (December 2024) – 5 articles

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22 pages, 6085 KiB  
Article
Technical–Economic Analyses of Electric Energy Generation by Biogas from Anaerobic Digestion of Sewage Sludge from an Aerobic Reactor with the Addition of Charcoal
by Cornélio Ribeiro Garcia, Michael Danilo Vargas Hincapie, Regina Mambeli Barros, Maxi Estefany Huamán Córdova, Hellen Luisa de Castro e Silva, Ivan Felipe Silva dos Santos, Electo Eduardo Silva Lora, Geraldo Lucio Tiago Filho, João Victor Rocha de Freitas, Adriele Maria de Cássia Crispim and Aylla Joani Mendonça de Oliveira Pontes
Methane 2024, 3(4), 595-616; https://doi.org/10.3390/methane3040034 (registering DOI) - 2 Dec 2024
Viewed by 171
Abstract
This study aimed to obtain the energy recovery potential of the biogas produced from anaerobic digestion (AD) of the sludge from a wastewater treatment plant (WWTP), including the use of biochar as an additive for substrate co-digestion and catalyst for methane production. We [...] Read more.
This study aimed to obtain the energy recovery potential of the biogas produced from anaerobic digestion (AD) of the sludge from a wastewater treatment plant (WWTP), including the use of biochar as an additive for substrate co-digestion and catalyst for methane production. We carried out the following steps: chemical–physical laboratory analyses of sludge samples; the building, operation, and monitoring of an experimental prototype of a batch bioreactor of 2.5 L for the AD of the sludge (with and without the addition of charcoal); qualitative measurements of biogas; the study of charcoal morphology; and the projection of useful energy generation from the AD sludge after treatment. A study on the economic viability and avoided greenhouse gas (GHG) emissions was performed based on the experimental results. The substrate showed alterations in all the physicochemical parameters evaluated after AD, such as a reduction of 35% in the biochemical oxygen demand (BOD) analysis; the experiment carried out using biochar showed positive results regarding the speed of CH4 production and a greater potential for energy recovery. Enterprises from 2000 kW onwards would present an internal rate of return (IRR) equal to or higher than the minimum attractiveness rate (MAR) of 15%. The USD 95.28/MWh tariff presented economic feasibility for the studied scenarios. WWTPs that produce enough sludge to generate power of 2000 kW would need to process the waste of 117,200 inhabitants with charcoal addition and 136,000 without charcoal. It would be possible to avoid the emission of 2307.97 tCO2/year (2000 kW). According to the results obtained, this study revealed that using alternative energies based on anaerobic digestion and biochar can generate positive results regarding methane production, and its application as an energy source in a WWTP proved to be economically viable at a specific level of power production. Full article
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11 pages, 353 KiB  
Article
Damage Effect and Injury Range of Shock Waves in Mine Methane Explosion
by Zhenzhen Jia, Qing Ye, Wei Xiong and Jialin Liu
Methane 2024, 3(4), 584-594; https://doi.org/10.3390/methane3040033 - 14 Nov 2024
Viewed by 348
Abstract
During the process of mining underground coal, the coal emits a large amount of methane into the mining space, which may lead to methane accumulation and exceed explosion safety limits When the methane encounters a fire source, a methane explosion may occur. The [...] Read more.
During the process of mining underground coal, the coal emits a large amount of methane into the mining space, which may lead to methane accumulation and exceed explosion safety limits When the methane encounters a fire source, a methane explosion may occur. The forceful impact caused by a methane explosion in an underground roadway can cause serious damage to the roadway structures and even lead to the collapse of the ventilation system. At the same time, the explosion impact may result in the death of workers and cause physical injury to the surviving workers. Therefore, it is necessary to study the damage effect and injury range of methane explosions. On the basis of the damage criteria and damage characteristics of methane explosions, according to the overpressure distribution of shock waves in the propagation process of a methane explosion, the explosion hazard range is divided into four ranges (from inside to outside): death range, serious injury range, minor injury range, and safety range. Four injury degrees of shock wave overpressure to personal body (slight, medium, serious injury, death), and seven damage degrees of overpressure to structures are also analyzed. The thresholds of their damage (destruction) are determined. On this basis, an experimental system and numerical simulation are constructed to measure damage characteristics, the overpressure value, and the range distance of a methane explosion with different initial explosion intensities. According to the experimental and numerical results, the attenuation formula of a methane explosion shock wave in the propagation process is derived. The research results show that the overpressure and impulse of shock waves are selected as the damage criteria for comprehensive evaluation, and the overpressure criterion is suitable of determining the injury (failure) range over long distances. The four injury ranges are in line with the actual situation and are reasonable. The injury degree also conforms to the medical results, which can be used to guide the injury degree of mine methane explosions. The injury range caused by methane explosions with different initial explosion intensities is reasonable and is basically consistent with the on-site situation. The derived attenuation formula and calculated safety distance are in good agreement with the experimental and numerical results. The research results can provide guidance and help in the escape, rescue, and protection of coal mine underground person. Full article
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15 pages, 1846 KiB  
Article
Methane Generation Potential of the Easily Degradable Group of Landfilled Municipal Solid Waste
by Cíntia Minori Takeda, Francisco Weshley Maciel-Silva, Tânia Forster-Carneiro and Miriam Gonçalves Miguel
Methane 2024, 3(4), 569-583; https://doi.org/10.3390/methane3040032 - 7 Nov 2024
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Abstract
Municipal solid waste (MSW) remains in sanitary landfills for many years. To maintain a circular economy, assessing the feasibility of reinserting MSW excavated from sanitary landfills into the production chain is important. This reduces environmental impacts, helping to minimize soil, water, and air [...] Read more.
Municipal solid waste (MSW) remains in sanitary landfills for many years. To maintain a circular economy, assessing the feasibility of reinserting MSW excavated from sanitary landfills into the production chain is important. This reduces environmental impacts, helping to minimize soil, water, and air pollution resulting from the decomposition of waste in landfills. In addition, it promotes economic benefits from the energy recovery of waste, such as biomass, which can generate electricity and heat, contributing to a sustainable energy matrix. The present study aimed to evaluate the easily degradable MSW group with 24 years of landfilling (ED-24) regarding its potential for methane generation. The ED group consisted of putrescible organic matter, wood, paper, cardboard, and pruning landfilled at a sanitary landfill in Southeastern Brazil. The feasibility of valuing ED-24 as a substrate for anaerobic digestion was assessed by analyzing its physical, chemical, and biochemical characterization and calculating its theoretical methane yield (TMY). The total volatile solids (TVS) and holo-cellulose contents of ED-24 were 73.45% and 61.39%, respectively, on a dry-weight basis. These values were in the range of those determined for non-landfilled lignocellulosic materials. Thus, 24 years of landfilling partially degraded the anaerobically lignocellulosic materials. The TMY of ED-24 was 233.41 mL CH4/g TVS, indicating a potential to generate methane. Despite the high lignin value, ED-24 can be valued as a substrate for anaerobic digestion. Full article
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8 pages, 1813 KiB  
Article
How Scheduled Maintenance Affects Anaerobic Digester Supervision Through Modelling: A Practical Approach
by Andrés Donoso-Bravo, María Constanza Sadino-Riquelme, Martín Vicencio, Fernando Zorrilla, Bastián Valdebenito and Felipe Hansen
Methane 2024, 3(4), 561-568; https://doi.org/10.3390/methane3040031 - 23 Oct 2024
Viewed by 618
Abstract
Anaerobic digestion plays a crucial role in the transition toward a circular economy. Incorporating system supervision through mathematical modelling can enhance control and resilience. This study aims to assess the impact of scheduled digester maintenance on the effectiveness of modelling as a tool [...] Read more.
Anaerobic digestion plays a crucial role in the transition toward a circular economy. Incorporating system supervision through mathematical modelling can enhance control and resilience. This study aims to assess the impact of scheduled digester maintenance on the effectiveness of modelling as a tool for monitoring and control. Data from a pilot-scale plug-flow digester were analyzed using an adapted ADM1 model. The maintenance involved halting the digester and removing sedimented solids. Model calibration indicated solid retention in the first two zones of the reactor, while the hydrolysis coefficient and biogas potential remained at 0.122 d−1 and 100.4 mL CH4/gVS, respectively. The average biogas production decreased from 156 to 109 mL/gVS pre- and post-maintenance. Simulations showed a decline in the model’s predictive accuracy after maintenance. To improve model fit, the initial conditions, solids retention, and kinetic parameters were adjusted. Optimal performance was achieved with khyd at 0.045 d−1 and B0 at 52.28 mL gVS−1, revealing an issue with the digester’s heating system. In conclusion, maintenance can significantly alter digester conditions, requiring model recalibration to maintain its effectiveness as a digital copilot for process supervision. Full article
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28 pages, 9185 KiB  
Article
Rapid Screening of Methane-Reducing Compounds for Deployment in Livestock Drinking Water Using In Vitro and FTIR-ATR Analyses
by Ryan J. Batley, Alex V. Chaves, Joel B. Johnson, Mani Naiker, Simon P. Quigley, Mark G. Trotter and Diogo F. A. Costa
Methane 2024, 3(4), 533-560; https://doi.org/10.3390/methane3040030 - 8 Oct 2024
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Abstract
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 [...] Read more.
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. Full article
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