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The conversion of lignite into biomethane is of great significance in the field of energy research. However, the yield of biomethane is low. To improve the biomethane yield from lignite, the effects of ultrafine grinding lignite on the biomethanation fermentation system were analyzed. The daily biomethane yield, total biomethane yield, pH, glucose concentration, and volatile fatty acid concentration of lignite were used to determine the optimum particle size of lignite. The results demonstrated that the total biomethane yield of the fermentation group with ultrafine grinding lignite was 14.69 mL·g−1 at a reaction temperature of 50°C and a biomethane fermentation time of 39 d. This was 36.91, 33.42, and 26.75% higher than that of the 40, 150, and 250 mesh lignite biomethane fermentation groups, respectively. The daily biomethane yield reached the peak of the ultrafine grinding lignite fermentation group 1.30 mL·g−1 on the second day, which was 1.96, 1.63, and 1.04 times higher than that of the 40, 150, and 250 mesh lignite fermentation systems, respectively. The research demonstrated that ultrafine grinding of lignite can effectively increase the biomethane yield. This provides an effective method for improving the yield of biomethane from lignite. [ABSTRACT FROM AUTHOR]

This study examined the influence of DES pretreatment using choline chloride and ethyl glycerol with the molar ratio of 1: 1 at different solid:liquid ratios and temperatures on groundnut shells' microstructural arrangement and biomethane yield. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) were used to study the effects of pretreatment on microstructural arrangements, and the pretreated substrate was digested at mesophilic temperature to determine its biomethane potential. The result of SEM analysis indicated that DES pretreatment alters the microstructural arrangement of groundnut shells, and XRD analysis showed an optimum crystallinity index of 20.71% when the substrate with a solid:liquid ratio of 1:2 was experimented at 80°C. The highest theoretical biomethane yield of 486.81 mL CH4/gVSadded was recorded when the substrate with a 1:4 solid:liquid ratio was investigated at 100°C, and the highest biodegradability rate (84.87%) was observed from the substrate treated with a 1:2 solid:liquid ratio at 100°C. The optimum biomethane yield of 365.70 mL CH4/gVSadded, representing a 226.05% increase, was observed from 1:2 of solid:liquid ratios at 100°C. Therefore, DES pretreatment using choline chloride and ethyl glycerol is a bright, low-cost pretreatment method for enhancing the biomethane yield of lignocellulose feedstocks. [ABSTRACT FROM AUTHOR]

The increasing demand for renewable energy sources as a substitute for fossil fuels has driven researchers to develop sustainable processes for biomass energy reuse in biofuel production. Based on this premise, the present study aimed to simulate the production process of synthesis gas (syngas) from vinasse, a by‐product of the sugar and alcohol industry, highlighting the applicability of this gas in transitioning toward a more renewable and sustainable energy future. The simulation was conducted in four distinct stages using the Aspen HYSYS® software. The first stage involved obtaining hydrated ethanol from sugarcane juice, followed by anaerobic digestion of vinasse to produce biogas. The third stage involved purifying the biogas to obtain biomethane. Finally, the simulation of steam methane reforming was performed to generate syngas. The modeling and simulation results demonstrated the feasibility of the process, as it generated 20.68 Nm3 of biogas (~55% vol CH4 and 45% vol CO2) per 1 Nm3 of vinasse, corresponding to 11.66 Nm3 of biomethane (~96.5% mol CH4), which aligns with national regulatory standards and the literature presented. Regarding syngas, both evaluated configurations yielded satisfactory results. The first configuration resulted in syngas with an H2/CO molar ratio of three, making it a viable source of pure hydrogen and a raw material for biofuel production, such as dimethyl ether and methanol. The second configuration, with an H2/CO molar ratio of two, holds great potential for its application in the synthesis of liquid fuels (Fischer‐Tropsch), serving as a direct substitute for gasoline, diesel, and jet fuel. [ABSTRACT FROM AUTHOR]

Synergistic fermentation of coal and corn straw is an effective tool to increase biomethane production. However, a large gap exists between the biomethane production conditions of corn straw filling coal mine goafs and laboratory experiments. In order to determine the effect of the field environment on synergistic biomethane production, biomethane production experiments with coal and corn straw were carried out under different conditions to find the key factors restricting the potential of biomethane production. The obtained results showed that various bacterial sources had significant influences on the biomethane production of coal and corn straw, and domesticated bacterial sources provided fermentation systems with more efficient biomethane production capacities than mine water sources. Biomethane production of coal and corn straw was relatively high under mixed conditions, but it was also promoted under unmixed conditions. Different inorganic minerals had different effects on synergistic biomethane production, which varied. For example, calcite, montmorillonite, and kaolin are common minerals in coal‐bearing strata that significantly enhance synergistic biomethane production of coal and corn straw. However, pyrite was found to significantly inhibit the synergistic biomethane production effect of coal and corn straw. Highly metamorphosed anthracite coal also presented biomethane production potential when stimulated by corn straw as a carbon source. The obtained results revealed the influences of different field conditions on the biomethane production of coal and corn straw and provided a reference for the field application of corn straw filling in coal mine goafs. [ABSTRACT FROM AUTHOR]

Background: Distillers' grain waste (DGW) is the main by‐product in the Baijiu‐making process and its management remains a great challenge for the Baijiu industry. To address this issue, an integrated biobutanol and biomethane production process was established to obtain valuable products from DGW and reduce environmental pollution. Results: In the integrated process, DGW was hydrolyzed and detoxified to produce biobutanol, while the distillery waste derived from solvent extraction process was used for biomethane fermentation. After the optimization of overliming detoxification of DGW hydrolysate by artificial neural network and genetic algorithm, totals of 10.65 ± 0.07 g L−1 butanol and 4.51 ± 0.21 g L−1 isopropanol were attained with negligible amounts of acetone and ethanol (i.e. 0.14 ± 0.00 and 0.52 ± 0.06 g L−1, respectively). Anaerobic digestion of the distillery waste was efficient, and the chemical oxygen demand removal rate approached 92.3 ± 0.1% with a methane yield of 167.8 ± 1.2 mL g−1 TCODremoved. Moreover, the anaerobic digestion effluent could be recycled as a potential substitute for process water in biobutanol fermentation without having any negative effect on enzymatic hydrolysis of DGW, and the butanol production also reached 8.19 ± 0.29 g L−1. Conclusion: The present study provides a new idea for comprehensive utilization of DGW towards energy and resource recovery, without secondary pollution. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Anaerobic digestion produces biogas, which is a proven bioprocess for generating energy, recovering nutrients, and reusing waste materials. Generally, the biogas generated contains methane (CH4) and carbon dioxide (CO2) in a 3:2 ratio, which limits the usage of the biogas to only cooking gas. To further enhance the application of biogas to vehicular fuel and natural gas grids, CO2 must be removed for an enhanced calorific value. This study seeks to lower greenhouse gas emissions by sequestering carbon dioxide from biogas. CO2 sequestration by microorganisms to upgrade the biogas and simultaneously convert the CO2 into acetic acid is a less explored area of research. Therefore, this research focuses mainly on the analysis of CO2 consumption % and acetic acid yield by novel isolated bacteria from fruit waste and mixed consortia obtained from cow dung and digested samples. The research finding states that there was a 32% increase in methane yield shown by isolated strain A1, i.e., CH4% was increased from 60% to 90%, whereas only an 11% increase was shown by consortia, which was an increase from 60% to 80%. The highest biogas upgradation was shown by the A1 strain at 30 °C incubation temperature and pH 8. The A1 strain demonstrated the highest recorded yield of acetic acid, reaching a concentration of 2215 mg/L at pH 8. A pH range of 7–8 was found to be the best-suited pH, and a mesophilic temperature was optimum for CO2 consumption and acetic acid production. The major objective is to create an effective method for improving biogas so that it is acceptable for different energy applications by lowering the carbon dioxide content and raising the methane content. This development signifies a significant advancement in the enhancement of biogas upgradation, as well as the concurrent generation of value-added goods, thereby establishing a sustainable platform technology. [ABSTRACT FROM AUTHOR]

An attractive application of crude glycerol is in the generation of biomethane by means of anaerobic co-digestion. Thus, the objective of this work was to evaluate the potential of neural networks and fuzzy logic to predict the production of biomethane from the anaerobic co-digestion of glycerol and/or sugarcane molasses. Firstly, a reactor model was implemented using Scilab (v. 6.1.1), considering the Monod two-substrate with an intermediate (M2SI) kinetic model proposed by Rakmak et al. (Rakmak, N.; Noynoo, L.; Jijai, S.; Siripatana, C. Lecture Notes in Applied Mathematics and Applied Science in Engineering. Melaka, Malaysia, p. 11–20, 2019), to generate a database for subsequent fitting and evaluation of neural and fuzzy models. The neural network package of Matlab was used. Fuzzy modeling was applied using the Takagi–Sugeno approach available in the ANFIS package of Matlab. The biomethane production data simulated using Scilab were considered in neural network modeling and validation, firstly employing a "generic" network applicable to all eight scenarios, providing a very good fit (R2 > 0.99). Excellent performance was also observed for specific artificial neural networks (one for each condition, again by using validation data generated by the M2SI model). The parameters of the M2SI model for the eight different conditions were also mapped using a neural network, as a function of the organic material composition, providing a fit with R2 > 0.99 when using 25 neurons. In the case of fuzzy logic, an RMSE (Root Mean Squared Error) of 18.88 mL of methane was obtained with 216 rules, which was a value lower than 0.5% of the order of magnitude of the accumulated methane. It could be concluded from the results that fuzzy logic and artificial neural networks offer excellent ability to predict methane production, as well as to parameterize the M2SI kinetic model (using neural networks). [ABSTRACT FROM AUTHOR]

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The organic matter (as an electron donor) could be oxidized at an anode in the bioelectrochemical systems (BESs), to produce electrons and protons with the biocatalysts of electrochemically active microorganisms. Electron acceptors at the cathode could accept them. By combining an anaerobic digestion reactor with BES, the chemical composition of biogas can be improved - the yield of methane can be increased at the expense of carbon dioxide. If an aerobic reactor is included in this combined system, complete decomposition of organic matter, generation of energy (biomethane) and nitrogen removal is achieved. The efficiency of carbon, sulfide and ammonium ions removal during anaerobic digestion of ethanol stillage in an integrated BES system was studied in 5 modes of operation - without BES, microbial fuel cell (MFC) and microbial electrolysis cell (MEC at 0.6, 0.8 and 1.0 V external voltage). In MEC mode, the gas composition is improved (increased amount of methane to 74 %, vol.), and the content of sulfates and hydrogen sulfide is reduced. At 1.0 V external voltage, 94.1 % removal of organic matter and 90.91 % removal of NH4 + are achieved. [ABSTRACT FROM AUTHOR]

To overcome major limiting factors of microbial processes in anaerobic digestion (AD), metal and metal ions have been extensively studied. However, there is confusion about the effects of metals and metal ions on biomethane productivity in previous research. In this study, Zn and Zn2+ were selected as representatives of metals and metal ions, respectively, to investigate the effects on biomethane productivity. After the metals and metal ions at different concentrations were added to the batch AD experiments under the same mesophilic conditions, a Zn dose of 1 g/L and a Zn2+ dose of 4 mg/L were found to cause the highest biomethane production, respectively. The results indicate that metal (Zn) and metal ion (Zn2+) have different mechanisms to improve AD performance. There may be two possible explanations. To act as conductive materials in interspecies electron transfer (IET), relatively high doses of metals (e.g., 1 g/L of Zn, 10 g/L of Fe) are needed to bridge the electron transfer from syntrophic bacteria to methanogenic archaea in the AD process. As essential mineral nutrients, the AD system requires relatively low doses of metal ions (e.g., 4 mg/L of Zn2+, 5 mg/L of Fe2+) to supplement the component of various enzymes that catalyze anaerobic reactions and transformations. This research will provide clear insight for selecting appropriate amounts of metals or metal ions to enhance biomethane productivity for industrial AD processes. [ABSTRACT FROM AUTHOR]

Olive cake, the solid byproduct of three-phase centrifugation olive oil production, has a high organic and polyphenol content, rendering it an environmental threat when landfilled as well as limiting its animal feed potential. This residue can be a good candidate for biomethane production due to its rich polysaccharide content (pectin, hemicellulose, and cellulose). Two strategies were compared to maximize biomethane production: destoning (i.e., removal of the seed fragments via mechanical means) and enzymatic pretreatment of the pulp. After 30 days of batch anaerobic digestion at 35 °C, both enzymatically pretreated and destoned olive cakes produced similar amounts of methane (~295 mL CH4/g volatile solids (VS)), 42% more than the control. A comparison of olive cake's biomethane yields with a broad range of agricultural residues in the literature demonstrated its suitability for biomethane production. Additionally, the digestate recovered from the anaerobic digestion of olive cake had high Kjeldahl nitrogen contents (3.6%, db) and low polyphenol concentrations (0.02 mg gallic acid equivalent (GAE)/g), qualifying it as an ingredient for soil amendment. This study demonstrated olive cake can be diverted from landfills for second-generation biofuel production, and that the resulting digestate may have value for soil amendment. [ABSTRACT FROM AUTHOR]

Vinasse is a residue that remains after the fractional distillation of fermented juice to obtain ethanol. Intended to extend the opportunities for by-product recovery, vinasse could be used as feedstock for biomethane production, departing from the linear focus of vinasse production, treatment, and disposal, to vinasse production and reuse. However, the high concentrations of sulfate and its inhibitory effect on biological activity could lower the yield of biomethane production. To overcome that, it was studied the potential of ultrafiltration membranes to alleviate the concentrations of sulfate from vinasse and concentrate the organic matter, intended to enhance the biomethane production potential. Raw vinasse, ultrafiltration concentrate, and ultrafiltration permeate were subjected to anaerobic digestion experiments and the cumulative biomethane yield was monitored over 70 days. The ultrafiltration concentrate presented the highest degradation rate (μ m : 2.83 ± 0.24 mL/g -VS.d.mL -sample) and longest lag-phase time (λ : 12.31 ± 0.83 d) compared with raw sugarcane vinasse (μ m : 1.44 ± 0.11 mL/g -VS.d.mL -sample ; λ : 6.57 ± 0.93 d) and ultrafiltration permeate (μ m : 1.14 ± 0.04 mL/g -VS.d.mL -sample ; λ : 2.92 ± 0.74 d). The potential for biomethane recovery was complemented by an energetic analysis involved in biomethane production and processing. The biomethane recovery from ultrafiltration concentrate presented the lowest specific energy consumption (3.34 MJ/Nm³-CH 4), followed by raw sugarcane vinasse (3.51 MJ/Nm³-CH 4) and ultrafiltration permeate (3.64 MJ/Nm³-CH 4). The remaining digested streams could still be potentially applied to soils for better use of their nutrients, however without an excessive load of organic matter already consumed during anaerobic digestion. Overall, the study demonstrated an effective alternative to salinity relief in raw sugarcane vinasse by ultrafiltration membranes and an alternative of higher vinasse valorization. [Display omitted] • UF was used as a strategy to enhance the biomethane production from vinasse. • UF applied to vinasse promote organic matter concentration and salinity relief. • UF concentrate has a higher potential for CH 4 production. • Anaerobic digestion produces more energy as CH 4 than consumed for its processing. • Upgrading unit had the greatest contribution to the energy required for processing. [ABSTRACT FROM AUTHOR]

In the context of the current sharp rise in energy prices and frequent weather anomalies caused by climate change, humankind faces two major problems: food supply and energy security, which compels us to look for alternative ways of solving these problems, including the reduction of the dependence on fossil fuels and the development of new technological processes for renewable energy production. The main objectives of this study were to evaluate some agrobiological peculiarities and the quality of harvested biomass from local cultivars: 'Solar' Helianthus tuberosus, 'Ileana' Inula helenium, 'Vital' Silphium perfoliatum, 'Energo' Sida hermaphrodita, 'Vigor' Astragalus galegiformis, 'Titan' Miscanthus giganteus, 'Argentina' Sorghum almum, 'Gigant' Polygonum sachalinense and the prospects of using their biomass as feedstock for renewable energy production. It was found that the studied cultivars, in the second and following growing seasons, were characterised by optimal growth rate and moderate regenerative capacity after being mowed, making it possible to cut by 1-3 times per season, obtaining 4.61-14.25 kg/m2 green mass, which may be used for anaerobic digestion in biogas plants, with biochemical methane potential of 297-336 litre/kg organic matter. Besides, digestate and fugate are believed to be good fertilizers, being rich in plant available nutrients such as nitrogen, phosphate and potash, and could serve as a replacement for fossil based mineral fertilizers in organic farming. The stems of the studied cultivars quickly dehydrate in the autumn-winter period, and can be chopped, milled and used as feedstock for the production by cellulosic ethanol and solid bio fuel. The analysis of lignocellulose composition showed that the dry matter contained 375-517 g/kg cellulose, 211-305 g/kg hemicellulose, 68-134 g/kg acid detergent lignin. The estimated theoretical ethanol yield from cell wall carbohydrates averaged 408-591 L/t. The gross calorific value of stem biomass was 18.63-19.50 MJ/kg. The specific density of densified solid fuel pellets and briquettes meet the quality standard requirements. The obtained results indicate the possibility of using the local cultivars for the creation of energy plantations in the Republic of Moldova. The cultivation and harvesting of these cultivars do not require sophisticated mechanisms and specific equipment like as in forest exploitations. [ABSTRACT FROM AUTHOR]

This study investigates the economic viability at the pre-feasibility level of a hybrid methanol and biomethane plant based on biogas coupled to a photovoltaic (PV) power plant and a proton exchange membrane (PEM) electrolyzer. The reference case settled in Uganda consisted of two units powered by a 200 kW PV plant and grid power: a 25 Nm3/h anaerobic digester and a 140 kW PEM electrolyzer-based methanol plant. Its production of 33.3 tons of methanol and 70.1 tons of biomethane per year can provide cooking fuel for 750 households. Response Surface Methodology was used to evaluate the impact of the three main factors on the simple payback period (PBP). The size of the PV plant had the most significant impact on PBP, followed by the cost of electricity, the interaction between these factors, and the PEM electrolyzer capital cost reduction, in this contribution order. These findings point to energy generation costs as the primary factor affecting the economic viability of these small-scale designs, even more than the PEM's capital cost. The response surface analysis revealed that only in a reduced region of the design space are values found that meet the threshold of 10 years for plant economic viability. [ABSTRACT FROM AUTHOR]

In this work, we studied the upgrading of a mixed gas stream having a typical biogas composition by membrane gas separation with the aim of producing a purified biomethane stream. A polyetherimide/polyimide (PEI-PI) membrane module with an area of 1500 cm2 was used to evaluate the mass transport properties and the influence of water vapour and H 2 S on the separation performance. CO 2 permeance was depleted by the presence of CH 4 contrarily to this latter, whose permeation was enhanced by CO 2. The permeances of both CO 2 and CH 4 were significantly affected by the presence of water vapour, showing a reduction of about 24–27% with respect to dry gas. Long-term analysis lasted about 650 days, showed an overall permeance variation of about 23% for N 2 and 14% for CO 2. The experimental permeance and selectivity values measured in wet conditions were used to simulate a multistep membrane system able to purify a "clean" biogas stream up to 98% of methane. It was found that the increasing number of steps from 3 to 7 allows a significant saving of membrane area, paired to an increment of CH 4 recovery and CO 2 purity. [Display omitted] • Permeation properties of PEI-PI membrane module under dry/wet mixed gas conditions. • Long-term analysis lasted about 650 days under continuous gas exposure. • Biogas purification to biomethane by multistep membrane configurations. • Positive effect of increasing numbers of steps on the separation performance. [ABSTRACT FROM AUTHOR]

Summary: One of the most important problems of the anaerobic digestion (AD) process and the main obstacle to this complex structural conversion is lignocellulose and the difficulty of its biological conversion. One way to disrupt the lignocellulosic composition is using nanoparticles (NPs) with proper concentration. In this study, biomethane potential tests have been used to maximize the biomethane production from anaerobic co‐digestion of municipal solid waste (MSW) and sewage sludge (SS) under different mixing ratios (MSW:SS: 100:0, 50:50, 60:40, 80:20 and 90:10) and different concentrations of iron (Fe) NPs (50, 70, 90 and 110 ppm) to speed up the AD process of the substrate, which increases biomethane production. Increasing the SS ratio up to 40% dramatically increased the biomethane yield, in a way that after 18 days of hydraulic retention time, 90% of methane (270 NmL/g VS) was obtained. The results showed that the highest biomethane yield (based on the optimal mixing ratio obtained in the first experiment, MSW:SS: 60:40) was obtained by adding 90 ppm Fe NPs using the statistical analysis (Duncan test) compared to the control (P < 0.05). Also, using iron NPs (Fe NPs) led to an increase in cellulose by 83%, a decrease in lignin by 62% and a decrease in hemicellulose by 32%, indicating an increase in the degradability due to the presence of NPs. Most of the biomethane was produced at 90 ppm Fe NPs concentration, showing an increase of 44% compared to control, and the maximum reduction in total solids and volatile solids were 36% and 28%, observed in this reactor, compared to the control sample. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this study was to evaluate some agrobiological peculiarities, the quality of harvested fresh mass, ensiled mass and prepared hay of the local ecotypes of white sweetclover, Melilotus albus, and yellow sweet clover, Melilotus officinalis, grown in pure culture in an experimental field of the National Botanical Garden (Institute), Chișinău, Republic of Moldova. Common sainfoin, Onobrychis viciifolia, was used as control. In the year when the experiments started, the plants of Melilotus albus and Melilotus officinalis were characterized by slower growth and development rates as compared with the control, and in the second year, the development rate was optimal, which allowed to reach a productivity of 3.78-4.31 kg/m2 fresh mass or 1.17-1.20 kg/m2 dry matter. It was found that the59utrientt content and fodder value were: 132-179 g/kg CP, 330-381 g/kg CF, 81-118 g/kg ash, 331-386 g/kg ADF, 473-567 g/kg NDF, 44-64 g/kg ADL, 72-86 g/kg TSS, 287-322 g/kg Cel, 142-181 g/kg HC, 58.8-63.1 % % DDM, RFV=97- 124, 11.66-12.42 MJ/kg DE, 9.57-10.20 MJ/kg ME, 5.59-6.22 MJ/kg Nel. The ensiled mass had specific smell, pH=4.42-4.52, 24.0- 40.5 g/kg organic acids, 3.4-5.1 g/kg acetic acid, 20.0-35.4 g/kg lactic acid, it contained 127-178 g/kg CP, 348-414 g/kg CF, 99-103 g/kg ash, 333-407 g/kg ADF, 462-581 g/kg NDF, 38-58 g/kg ADL, 62-70 g/kg TSS, 285-349 g/kg Cel, 129-174 g/kg HC, 57.2-63.0 % DDM, RFV=92-I29, 9.34-10.19 MJ/kg ME and 5.30-6.20 MJ/kg Nel. The hay prepared from yellow sweet clover, Melilotus officinalis, contained 150 g/kg CP, 34 g/kg CF, 83 g/kg ash, 385 g/kg ADF, 493 g/kg NDF, 56 g/kg ADL, 80 g/kg TSS, 317 g/kg Cel and 163 g/kg HC with 59.6 % DDM, RFV=103, 9.69 MJ/kg ME and 5.70 MJ/kg Nel. We found that the fresh and ensiled mass substrates for anaerobic digestion had C/N=17-25 and optimal amount of lignin and hemicelluloses, the biochemical methane potential of the studied substrates varied from 267 to 353 1/kg ODM, but in the control it was about 291-311 1/kg ODM. The local ecotypes white sweetclover, Melilotus albus, and yellow sweet clover, Melilotus officinalis, have optimal productivity and nutrient concentration, can be serve as alternative fodder crops, as well feedstock in biogas generators for the production of renewable energy. [ABSTRACT FROM AUTHOR]

As Europe faces the dual challenge of decarbonizing its energy sector while ensuring energy security, REPowerEU reinforces the ambitious targets outlined in the Green Deal, complementing the "Fit for 55" package. This work analyses sustainable biomethane production in Europe, with a specific focus on Italy, and its conversion into sustainable fuels. Under the light of existing policy targets and regulatory instruments, the study explores innovative and sustainable agro-energy chains, with biomethane as energy vector for producing sustainable aviation fuels (SAF) and methanol for maritime. Decentralized biomass digestion and centralized biomethane conversion in refinery are combined, considering three key Gas-to-Liquid (GTL) pathways: Fischer-Tropsch and methanol synthesis, and gas fermentation/alcohol-to-jet. A simulation model was used to estimate the performances of these routes, providing insights on process yields and energy balances. Additionally, preliminary investment cost estimates are considered by reviewing existing references and extrapolating unit-specific cost data. As by 2030 biomethane in Europe could supply 38 bcm, the routes analysed could cover 4 to 11% of jet fuel demand, and from 25 to 56% of maritime fuel needs. By 2050, with a potential EU biomethane supply of 91 bcm, these pathways might meet 9–25% of jet fuel demand, and 48–105% of maritime fuel demand. In Italy, by 2030, 5.6 bcm of biomethane could enable these pathways to meet 7–18% of jet fuel demand, and a remarkable 69–152% of maritime fuel demand. By 2050, with 8.2 bcm of biomethane, these routes might cover 8–22% of jet fuel demand, and potentially satisfy 91–198% of maritime fuel demand. Moreover, these pathways would also yield other added-value by-products (e.g. naphtha, diesel, waxes, hydrogen, gasoline), which should be considered in comparing them. The average investment costs for each route were estimated at 791,970 USD/t/day for the Fischer-Tropsch based GTL plant, 130,275 USD/t/day for the methanol-based GTL plant, and 669,740 USD/t/day for the GTL plant involving gas fermentation/alcohol-to-jet conversion. [Display omitted] • Decentralized biomethane-centralized Gas-to-Liquid can decarbonize EU aviation and maritime sectors. • By 2030, GTL routes may satisfy 4–11% jet fuel and 25–56% of maritime fuel EU demands. • By 2050, 9–25% of jet and 48–105% of maritime fuel EU needs could be covered by these paths. • 2030 Italian jet fuel (7–18%) and maritime (69–152%) demands could be met by these routes. • At 2050, 8–22% of jet fuel and 91–198% of maritime needs could be satisfied for Italy. [ABSTRACT FROM AUTHOR]

In recent years, industries such as oil and gas production, waste management, and renewable natural gas/biogas have made a concerted effort to limit and offset anthropogenic sources of methane emissions. However, the state of emissions, what is emitting and at what rate, is highly variable and depends strongly on the micro-scale emissions that have large impacts on the macro-scale aggregates. Bottom-up emissions estimates are better verified using additional independent facility-level measurements, which has led to industry-wide efforts such as the Oil and Gas Methane Partnership (OGMP) push for more accurate measurements. Robust measurement techniques are needed to accurately quantify and mitigate these greenhouse gas emissions. Deployed on both fixed-wing and multi-rotor unmanned aerial vehicles (UAVs), a miniature tunable diode laser absorption spectroscopy (TDLAS) sensor has accurately quantified methane emissions from oil and gas assets all over the world since 2017. To compare bottom-up and top-down measurements, it is essential that both values are accompanied with a defensible estimate of measurement uncertainty. In this study, uncertainty has been determined through controlled release experiments as well as statistically using real field data. Two independent deployment methods for quantifying methane emissions utilizing the in situ TDLAS sensor are introduced: fixed-wing and multi-rotor. The fixed-wing, long-endurance UAV method accurately measured emissions with an absolute percentage difference between emitted and mass flux measurement of less than 16% and an average error of 6%, confirming its suitability for offshore applications. For the quadcopter rotary drone surveys, two flight patterns were performed: perimeter polygons and downwind flux planes. Flying perimeter polygons resulted in an absolute error less than 36% difference and average error of 16.2%, and downwind flux planes less than 32% absolute difference and average difference of 24.8% when flying downwind flux planes. This work demonstrates the applicability of ultra-sensitive miniature spectrometers for industrial methane emission quantification at facility level with many potential applications. [ABSTRACT FROM AUTHOR]

Methane from biogas is a promising option for the transition to a circular economic system based on renewable and sustainable energy. Currently, there is a wide variety of technologies capable of efficiently extracting the impurities contained in biogas in order to produce biomethane. In the present study, work was carried out in a pilot plant for cleaning and upgrading real biogas from anaerobic digestion by means of the chemical absorption method. In contrast to other technologies, chemical absorption stands out for having the lowest CH4 losses, which was crucial for this study. The objective was to purify and upgrade the biogas from anaerobic digestion of a WWTP to achieve a high concentration of methane and use it as biofuel in vehicles. The two aqueous solutions used as absorbents were mono-ethanolamine (MEA) and N-methyldiethanolamine (MDEA), both at 20% and 40% concentrations. It was found that the most effective solution was the MEA at 20% concentration, since it has the highest CO2 removal efficiency (94%) and, therefore, CH4 richness (96%). Finally, for every 100 m3 of biomethane generated after the chemical absorption process, 62 Nm3 of biofuel were obtained. [ABSTRACT FROM AUTHOR]

The primary objective of this research is to study ways to increase the potential of energy production from food waste by co-production of bioethanol and biomethane. In the first step, the food waste was hydrolysed with an enzyme at different concentrations. By increasing the concentration of enzyme, the amount of reducing sugar produced increased, reaching a maximum amount of 0.49 g/g food waste. After 120 h of fermentation with Saccharomyces cerevisiae, nearly all reducing sugars in the hydrolysate were converted to ethanol, yielding 0.43-0.50 g ethanol/g reducing sugar, or 84.3-99.6% of theoretical yield. The solid residue from fermentation was subsequently subjected to anaerobic digestion, allowing the production of biomethane, which reached a maximum yield of 264.53 ± 2.3 mL/g VS. This results in a gross energy output of 9.57 GJ, which is considered a nearly 58% increase in total energy obtained, compared to ethanol production alone. This study shows that food waste is a raw material with high energy production potential that could be further developed into a promising energy source. Not only does this benefit energy production, but it also lowers the cost of food waste disposal, reduces greenhouse gas emissions, and is a sustainable energy production approach. [ABSTRACT FROM AUTHOR]

Biomethane is a renewable product that can directly substitute its fossil counterpart, although its synthesis from residual biomasses has some hurdles. Because of the complex nature of both biomasses and the microbial consortia involved, innovative approaches such as mathematical modeling can be deployed to support possible improvements. The goal of this study is two-fold, as we aimed to modify a part of the Anaerobic Digestion Model No. 1 (ADM1), describing biomethane production from activated sludge, matching with its actual microbial nature, and to use the model for identifying relevant parameters to improve biomethane production. Firstly, thermodynamic analysis was performed, highlighting the direct route from glucose to biomethane as the most favorable. Then, by using MATLAB® and Simulink Toolbox, we discovered that the model fails to predict the microbiological behavior of the system. The structure of the ADM1 model was then modified by adding substrate consumption yields in equations describing microbial growth, to better reflect the consortium behavior. The updated model was tested by modifying several parameters: the coefficient of decomposition was identified to increase biomethane production. Approaching mathematical models from a microbiological point of view can lead to further improvement of the models themselves. Furthermore, this work represents additional evidence of the importance of informatics tools, such as bioprocess simulations to foster biomethane role in bioeconomy. [ABSTRACT FROM AUTHOR]

Biomethane upgraded from biogas had been proven as a potential renewable energy. Utilizing the metabolic activity of enriched hydrogenotrophic methanogens was regarded as a new way to upgrade biogas. The optimal reaction pH and mixed gas (H2 and CO2) injection time for enriching hydrogenotrophic methanogens were identified, and the performance of upgrading raw biogas produced from food wastes anaerobic digestion was assessed in this study. In the optimal experiment, the results showed that the maximum methane content reached 61.01% when pH was 8 and injection time was 5 min. In all groups, the concentration of acetic acid showed a trend of increasing followed by decreasing during this process. High-throughput sequencing indicated that Methanobacterium and Methanoculleus belonging to hydrogenotrophic methanogens were the dominated genus. The maximum methane content reached 91.43% in the biogas upgrading stage when it was combined with anaerobic digestion stage. At the end of the experiment, the methane content of the upgrading stage was 36.66% higher than that of the raw biogas produced from anaerobic digestion stage. Microbiological analysis showed that hydrogenotrophic methanogens were also the predominant genus. [ABSTRACT FROM AUTHOR]

Residual Fermented Solid (RFS) is the used biocatalyst obtained after enzymatic biodiesel production carried out applying the fermented solid (FS) with lipase activity. Approximately 350 g of RFS are generated for each liter of biodiesel produced from palm residues fermented solid. In this study, this residue was used for the first time as a raw material for biological hydrogen production through dark fermentation and sequential application of the hydrogen production liquid waste (HPLW) for methane obtainment via anaerobic digestion. The RFS was composed mostly of oils and fats (60% wt.%), and carbohydrates, such as mannose, glucose, and xylose. Hydrogen yield reached 239 ± 44 mL H 2 /L after 24 h of fermentation using 31 g RFS /L at the beginning of the process. Additionally, 204 ± 13 mL CH 4 /g COD were produced through the anaerobic digestion of HPLW, which represented 61% of efficiency. [Display omitted] • Residual Fermented Solid is an attractive raw material for H 2 and CH 4 production. • 239 ± 44 mLH 2 /L were obtained after 24 h of fermentation using 31 g RFS /L. • 204 ± 13 mLCH 4 /gCOD were produced from H 2 production effluent. • Methane production with the hydrogen effluent reached 61% efficiency. • A biorefinery approach of the palm oil industry through the use of residues. [ABSTRACT FROM AUTHOR]

• Acclimation to increasing levels of H 2 helped to improve H 2 utilisation rate. • The accumulation of C2–C4 VFA was reversed. • Up to 81% CH 4 was obtained by in-situ biomethanation against 65% without H 2. • Up to 65% potential increase in energy return on investment is obtainable. • Increased carbon savings potential of 52–59% is obtainable. The increasing rate of food waste (FW) generation globally, makes it an attractive resource for renewable energy through anaerobic digestion (AD). The biogas recovered from AD can be upgraded by the methanation of internally produced carbon dioxide, CO 2 with externally sourced hydrogen gas, H 2 (biomethanation). In this work, H 2 was added to AD reactors processing FW in three successive phases, with digestate from preceding phases recycled in succession with the addition of fresh inoculum to enhance acclimation. The concentration of H 2 was increased for succeeding phases: 5%, 10% and 15% of the reactor headspace in Phase 1 (EH1), Phase 2 (EH2) and Phase 3 (EH3), respectively. The H 2 utilisation rate and biomethane yields increased as acclimation progressed from EH1 through EH3. Biomethane yield from the controls: EH1_Control, EH2_Control and EH3_Control were 417.6, 435.4 and 453.3 NmL-CH 4 /gVS added accounting for 64.8, 73.9 and 77.8% of the biogas respectively. And the biomethane yield from the test reactors EH1_Test, EH2_Test and EH3_Test were 468.3, 483.6, and 499.0 NmL-CH 4 /gVS added , accounting for 77.2, 78.1 and 81.0% of the biogas respectively. A progressive in-situ biomethanation could lead to biomethane production that meets higher fuel standards for gas-to-grid (GtG) injections and vehicle fuel – i.e. >95% CH 4. This would increase the energy yield and carbon savings compared to conventional biogas upgrade methods. For example, biogas upgrade for GtG by in- situ biomethanation could yield 7.3 MWh/t FW energy and 1343 kg-CO 2 e carbon savings, which is better than physicochemical upgrade options (i.e., 4.6–4.8 MWh/t FW energy yield and 846–883 kg-CO 2 e carbon savings). [ABSTRACT FROM AUTHOR]

This study presents a techno-economic and environmental analysis of biogas upgrading processes. Biogas upgrading, with the removal of acid gases (CO 2 , H 2 S) from biogas produced from municipal solid wastes, can reduce air pollutant emission and increase the heat of combustion of the final product, thus promoting biogas use as a transport fuel while mitigating landfill disposal in urban areas. Among technically feasible routes, amine scrubbing results in relatively low methane loss and a renewable methane-enriched product. In this study, diglycolamine and methyldiethanolamine with diethanolamine were considered as solvents. Simulations were carried out using Aspen Plus, in which process variables were evaluated for different process conditions, with the restriction to attend product regulatory specifications. The results indicate that the diglycolamine-based upgrading route can remove up to 99% of the carbon dioxide from the biogas, generating a biomethane product with 91% methane. Net present value (NPV) was calculated for both cases, under economically feasible conditions, considering a biomethane price of 0.38 US$/Nm3. An environmental evaluation based on Life Cycle Assessment (LCA) estimates a reduction of ca. 95% in CO 2 equivalent emissions for the upgraded biomethane. • Design of amine scrubbing for biogas upgrading. • Techno–economic and environmental analysis for 99% CH 4 recovery and 91% CH 4 purity. • Life cycle assessment estimates ca. 95% of reduction in CO 2 equivalent emissions. [ABSTRACT FROM AUTHOR]

The generation of biomethane in geological history is primarily influenced by multi-stage tectonic uplift and diverse groundwater charging conditions. To investigate and simulate this process, we conducted laboratory experiments involving cyclic addition of nutrients. The results demonstrate that continuous nutrient supplementation is a viable approach for achieving sustained biomethane production, with yields ranging from 1191.53 to 1316.90 μmol/g over three biodegradation cycles. Fitzhugh models prove to be the most suitable for predicting biomethane production. Biodegradation induces rearrangement of coal's pore structure, leading to increased pore sizes and numbers, facilitating the infiltration of biological enzymes, and enhancing methanogenesis rates. Our study elucidates the mechanisms underlying biomethane generation in geological history and offers strategies to expedite the practical application of coalbed methane bioengineering. • The effect of coal functional group on kinetic property was studied. • The cyclic biodegradation for the first time in coal. • Different chemical structure contributes to the performance parameter of bio-methanogenic differently. • Pore structure of coal rearrangement again and again by microorganism. [ABSTRACT FROM AUTHOR]

• Plants of 500 tons/d of Agave bagasse to produce methane and power were simulated. • Biological, enzymatic, dilute acid, and steam explosion pretreatments were considered. • The capital expenses (CAPEX) and operative expenses (OPEX) were analyzed. • Pretreatment and anaerobic digestion parameters were based on experimental data. • The energy produced was two times the energy consumed in all the scenarios. Agave bagasse is an agricultural residue that has the potential to be used as feedstock biorefineries. However, its complex structure requires a pretreatment step to facilitate the accessibility to carbohydrates for its subsequent conversion. In this study, the capital and operative expenses (CAPEX and OPEX) were simulated for industrial plants processing 500 ton/d of Agave bagasse using different pretreatment platforms for methane production and power generation on experimental data. The scenarios consisted of i) biological, ii) enzymatic, iii) dilute acid, and iv) steam explosion pretreatments and a case-based scenario without pretreatment. All these scenarios included milling, pretreatment, anaerobic digestion, and cogeneration stages. The results showed that those pretreatments carried out under soft conditions (biological and enzymatic) decreased between 2.1 and 2.8 times CAPEX compared to the highest value obtained in the diluted acid and case-based scenarios. The steam explosion, a pretreatment carried out under severe conditions, was less effective reducing CAPEX by only 1.2 times compared to the highest value. Furthermore, compared to the case-base scenario, only the biological pretreatment reduced the OPEX by a factor of 2, whereas the other pretreatments resulted in OPEX that were 2.0 to 3.5 times higher. Among the utilities (cooling water, steam generation, and energy) the steam generation contributed 47% to 76% of the total OPEX. The energy produced (kW⋅h/yr) was approximately twice the energy consumed for all scenarios. A sensitivity analysis demonstrated the robustness of the platforms since fluctuations in the prices of feedstock and raw materials did not impact the total production cost of methane, except for biological and enzymatic pretreatments. For all platforms, the solid loading was the process parameter with the highest impact on the production cost of methane. Overall, the study showed that biological and enzymatic pretreatments had the best economic performance. However, low substrate conversion and the high cost of enzymes and equipment, respectively, remained the main challenges to address in future research. [ABSTRACT FROM AUTHOR]

The high potential of food waste (FW) as a substrate in the anaerobic digestion (AD) raises the dilemma between producing added value bioproducts such as volatile fatty acids (VFA) or biomethane. This work assessed the scale-up of producing VFA from FW. At lab-scale (5 L), pH 7 and organic loading rate (OLR) of 10 g COD/L/d were selected as the best conditions, obtaining a VFA yield of 36.6 % g COD-VFA/g COD substrate and a rate of 3.9 g COD-VFA/L/d. Afterwards, a semi-industrial pilot plant (1.5 m3) was operated under these conditions, showing VFA production indicators in line with those of lab scale, with acetic acid as main VFA (50 % mass basis), followed by propionic and butyric (20 % each). The economic comparative between the production of VFA and biomethane concluded that revenues from VFA production (22.9 €/t FW) are considerably higher than those from biomethane (11.7 €/t FW). [Display omitted] • Scale-up of VFA production process with food waste (FW) from lab to pilot scale was assessed. • Best operating conditions for VFA production were identified at laboratory scale. • pH 7 and OLR 10 g COD/L/d were the optimum for maximising VFA yield and rate. • Pilot plant operation reported comparable results to those at lab scale. • Net profit of VFA is higher than that of biomethane (22.9 vs 11.7 €/t FW). [ABSTRACT FROM AUTHOR]

[Display omitted] • Material-focused strategy achieves 54% more carbon credit than the energy-focused. • Carbon credit from biogas energy recovery drop by 23% and 38% in 2030 and 2060. • Carbon credit from biogas material recovery boost by 35% and 59% in 2030 and 2060. • Material-focused biogas strategies better align with climate change goals. Two novel biogas upgrading strategies that recover high-value chemicals or CO 2 liquid fertilizer from biogas besides biomethane were evaluated from the view of global warming potential (GWP) through life cycle assessment in comparison with conventional approaches. Results show that the scenarios producing biomethane with nano calcium carbonate or CO 2 liquid fertilizer from biogas present significantly lower GWP (–3.4 kgCO 2 -eq/Nm3-biogas and –4.4 kgCO 2 -eq/Nm3-biogas, respectively), compared to combined heat and power scenario (–2.4 kgCO 2 -eq/Nm3-biogas) and biogas upgrading by high pressure water scrubbing scenario (–1.3 kgCO 2 -eq/Nm3-biogas). The carbon sequestration and utilization from CO 2 -rich water significantly enhanced carbon reduction in overall biogas management. Furthermore, considering cleaner electricity in the future, strategies focusing on managing biogas for materials will align more with climate change goals than energy-focused strategies. This study provides insight for decision-makers in developing roadmaps for carbon reduction pathways in biogas-relating sectors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Process simulation and a techno-economic analysis for the AD of vinasses was assessed. • Deterministic and stochastic modelling were used to assess the economic performance. • Power generation showed the best economic performance in the Cuban scenarios. • High incentive values are required to get profit in biomethane alternatives. • Minimum milling capacities of 10,800 t cane /d are required for biomethane projects. This paper presents a process simulation model in Aspen Plus® and a techno-economic assessment for the anaerobic digestion of Cuban sugarcane vinasses considering three scenarios for biogas application: electricity production (S_1), biomethane as vehicle fuel (S_2), and biomethane for gas grid injection (S_3). From the simulation model, non-significant differences (p_value ≥ 0.1779) between experimental and simulation results were found. S_1 showed the best economic performance among the assessed biogas applications. From the sensitivity analysis, the mean electricity price leading to a net present value of zero for S_1 was 90 USD/MWh, while for S_2 and S_3 the mean incentive required was 0.33 USD/m3 biomethane and 0.67 USD/m3 biomethane , respectively. The uncertainty analysis showed a chance for investment failure in S_1 less than 10%, whereas for S_2 and S_3 it ranged between 31–37%. The minimum scale required (milling and distillery capacities, ethanol yield) for getting profits from biomethane projects was targeted at 10,800 t cane /day, 108 m3 ethanol /d at 10 L ethanol /t cane , respectively. To this end, Cuban plants should significantly increase their average capacities; otherwise, a centralized biomethane production by limiting the number of biomethane plants to one or two per province could be implemented. [ABSTRACT FROM AUTHOR]

Hydrothermal treatment can facilitate hydrolysis of biomass wastes such as algae and livestock manures, by converting high-molecular weight carbohydrates and proteins to monosaccharides and amino acids. However, further decomposition and reciprocal reaction of monosaccharides and amino acids are usually accompanied with hydrothermal treatment, which have negative impacts on microbial fermentation performance. In this study, glucose and glycine were used as model substrates during hydrothermal treatment coupled with semi-continuous hydrogen and methane fermentation. The results showed that thermal decomposition of glucose was stronger than glycine, due to the binary interactions between carbonyl group and amino group. Acidic condition could suppress conversion of intermediate compounds to polymers, thereby improving 5-HMF concentration to 7.59 g/L. Hydrothermal by-products had adverse impacts on hydrogen fermentation stability, resulting in a wide fluctuation of hydrogen production rate of around 0.55 L/L/d. Adding sulfuric acid for treatment would increase the competition of sulphate reducing bacteria, and cause a stuck methane fermentation. Additionally, by-products degradation promoted the growth of hydrogenotrophic and mixotrophic methanogens. • Hydrothermal treated substrates were used for H 2 and CH 4 fermentation. • Acidic condition suppressed conversion of intermediate compounds to polymers. • Hydrothermal by-products adversely affected the hydrogen fermentation stability. • Sulphate reducing bacteria competition may cause a stuck methane fermentation. • Inhibitor degradation promoted hydrogenotrophic and mixotrophic methanogens. [ABSTRACT FROM AUTHOR]

Energy and waste disposal issues are calling for advanced recycling methods such as conversion of organic waste into biohydrogen and biomethane. Here we review factors that influence yields, such as pH, temperature, substrate composition, biocatalyst, nutrient content, volatile fatty acids concentration, organic loading rate, hydraulic retention time and C/N ratio. The optimum pH is 5.5–6 for hydrogen production, and 6.8–7.2 for methane production. Hydrogen yield improved highly after reducing the retention time from 72 to 20 h. The highest methane productivity was achieved with C/N ratio of 16–27. We also discuss methods to improve efficiency such as co-digestion, pre-treatment, application of additives and optimal digester design. Co-digestion synergizes the effects on microbial communities, balances the nutrients, reduces the inhibitory effects and improves the economic viability. Co-digestion has enhanced the productivity by 25–400% compared to mono-digestion. Acid pre-treatment is the best method for lignocellulose hydrolysis, followed by enzyme pre-treatment. Microwave pre-treatment enhances the biomethane production 4–7 times. The batch mode improves the substrate degradation efficiency and hydrogen production by 25% compared to the continuous mode. The addition of trace metals alters the hydrogenase activity during anaerobic fermentation. Reaction kinetics and metabolomics, bioaugmentation, digestate recirculation, frequent feeding and development of bioreactor systems for two-stage anaerobic digestion are also presented. [ABSTRACT FROM AUTHOR]

This study involves continuous co-digestion of swine manure and pineapple waste mixture using two-stage anaerobic reactors and examines hydraulic retention time (HRT) and substrate heat pre-treatment. The maximum hydrogen and methane production rates of 1488.62 and 991.57 mL/L/d, respectively, reached optimal HRTs of 4.5 h in the hydrogen production fermenter (HPF) and 9 d in the methane production fermenter (MPF) using heat pre-treatment. Acetic acid is a dominant volatile fatty acid of the soluble metabolites with values 70%–73% under all the tested conditions and increased values under heat pre-treatment and high HRT. Firmicutes and Euryarchaeota are the main bacteria species detected in HPF and MPF, respectively. The optimal total energy of 196.47 kJ/L/d and chemical oxygen demand (COD) removal efficiency of 90% were obtained by a complete anaerobic co-digestion process at a high substrate concentration of 105 g COD/L and low HRT of 4.5 h. This shows that the two-stage co-digestion process could increase the COD removal efficiency, hydrogen production rate, and net energy gains and produce high quality biogas and significantly reduce fermentation time. Image 1 • Two-stage of Continuous Biohythane Production Process was developed. • Pretreatment and HRTs affected biohydrogen and biomethane productions. • Heat-pretreatment with lower HRT gave high H 2 and energy production, respectively. • Firmicutes and Euryarchaeota dominated phylum in the HPF and MPF, respectively. [ABSTRACT FROM AUTHOR]

Featured Application: AD applied to brackish water fish sludges can be a promising treatment process with quite good methane productions, increasing the economic and environmental sustainability of the sector. The development of intensive aquaculture is facing the challenge of the sustainable management of effluents. The reproductive sectors (i.e., hatcheries) mainly use water recirculation systems (RAS), which discharge a portion of wastewater. Anaerobic digestion (AD) could reduce the environmental impact of this waste stream while producing biogas. The study is focused on the biochemical methane potential (BMP) of brackish fish hatchery sludges. Wastewater was concentrated by microfiltration and sedimentation and thickened sludges were treated in a BMP system with different inoculum/substrate (I/S) volatile solids ratios (from 50:1 to no inoculum). The highest I/S ratio showed the highest BMP (564.2 NmL CH4/g VS), while different I/S ratios showed a decreasing trend (319.4 and 127.7 NmL CH4/g VS, for I/S = 30 and I/S = 3). In absence of inoculum BMP resulted of 62.2 NmL CH4/g VS. The kinetic analysis (modified Gompertz model) showed a good correlation with the experimental data, but with a long lag-phase duration (from 14.0 to 5.5 days) in particular with the highest I/S. AD applied to brackish water sludges can be a promising treatment with interesting methane productions. For a continuous, full-scale application further investigation on biomass adaptation to salinity and on retention times is needed. Further experimental tests are ongoing. [ABSTRACT FROM AUTHOR]

This paper defines the roles of biomethane for a double-green transition, through the integration of an effective management of renewable energy and municipal waste. The authors perform an assessment of the potential transition of the municipality of Rome to a more sustainable transport system, based on the economic feasibility of production of biomethane as analysed with the Discounted Cash Flow methodology. The potential reduction of emissions is quantified considering biomethane, to be used as vehicle fuel instead of natural gas. The provision of subsidies is found to be an essential condition to support the development of the biomethane sector. The subsidies must be coordinated with other policies such as the construction and operation of new fuelling stations and the increase of vehicles fuelled by biomethane. Several economic indicators are used to support investors by defining the conditions in which the profitability and economic opportunities are quantified. The transformation of bio-wastes into clean energy, closes the loop and helps societies to make progress toward becoming circular economies, which can contribute to decarbonizing the transport sector. Results of these analyses are applicable in other municipalities, which are currently under-utilizing their organic wastes and by-products. Image 1 • Biomethane supports the development of CE models. • Biomethane can contribute to a double green transition.. • A total NPV varies from 4.6 million € to 63.3 million €. • Do Nothing cost varies from 365 thousand € to 2872 thousand €. • The decrease of GHG emissions ranges from 43 to 51 thousand ton CO2eq/year. [ABSTRACT FROM AUTHOR]

Cotton straws are one of the most produced agricultural wastes in Turkey and getting attention by not being consumed as animal feed or an industrial stock and having a huge potential in clean energy production. In this study, different pretreatment methods for the conversion of cotton straw to sugar then biohydrogen and biomethane production from cotton straw were examined. The energy potential of cotton straw in case of an evaluation of these biomass residues was also determined using fuel cell technology. Acid pretreatment provided the highest yield in biogas formation as well as sugar extraction from the raw sample. The highest biohydrogen and biomethane production were obtained as 33 mL H 2 /g VS and 83 mL CH 4 /g VS, respectively. Concomitantly, the maximum power peaks in PEM fuel cell studies were observed as 0.45 W/cm2 and 0.23 W/cm2 with current densities of 1.086 A/cm2 and 0.522 A/cm2 when the fuel cell was fed with pure H 2 and biogas, respectively. This suggested that acid pretreatment is more suitable for cotton straw management in sustainable and renewable ways and the results demonstrated that PEM fuel cell is a promising clean technology for energy generation from cotton straw. Image 1 • Cotton straws were extracted by using three different pretreatment methods. • Acid pretreatment was ~2 times effective than other methods in sugar extraction. • The highest bioH 2 and bioCH 4 production was 33 and 83 mL/g VS, respectively. • The biohydrogen was used as fuel in PEM fuel cells for clean energy generation. • The maximum power and current density in PEMFC were 23 W/cm2 and 0.522 A/cm2. [ABSTRACT FROM AUTHOR]

The shift from straw incorporation to biofuel production entails emissions from production, changes in soil organic carbon (SOC) and through the provision of (co‐)products and entailed displacement effects. This paper analyses changes in greenhouse gas (GHG) emissions arising from the shift from straw incorporation to biomethane and bioethanol production. The biomethane concept comprises comminution, anaerobic digestion and amine washing. It additionally provides an organic fertilizer. Bioethanol production comprises energetic use of lignin, steam explosion, enzymatic hydrolysis and co‐fermentation. Additionally, feed is provided. A detailed consequential GHG balance with in‐depth focus on the time dependency of emissions is conducted: (a) the change in the atmospheric load of emissions arising from the change in the temporal occurrence of emissions comparing two steady states (before the shift and once a new steady state has established); and (b) the annual change in overall emissions over time starting from the shift are assessed. The shift from straw incorporation to biomethane production results in net changes in GHG emissions of (a) −979 (−436 to −1,654) and (b) −955 (−220 to −1,623) kg CO2‐eq. per tdry matter straw converted to biomethane (minimum and maximum). The shift to bioethanol production results in net changes of (a) −409 (−107 to −610) and (b) −361 (57 to −603) kg CO2‐eq. per tdry matter straw converted to bioethanol. If the atmospheric load of emissions arising from different timing of emissions is neglected in case (a), the change in GHG emissions differs by up to 54%. Case (b) reveals carbon payback times of 0 (0–49) and 19 (1–100) years in case of biomethane and bioethanol production, respectively. These results demonstrate that the detailed inclusion of temporal aspects into GHG balances is required to get a comprehensive understanding of changes in GHG emissions induced by the introduction of advanced biofuels from agricultural residues. [ABSTRACT FROM AUTHOR]

The aim of this work was to evaluate biomethane production by anaerobic digestion using aqueous phase from Fast Pyrolysis of Douglas Fir Wood as substrate. The effect of biomass acid treatment and condensation temperature on the bio-oil chemical composition and aqueous phase separation with a fractional condensation system coupled to Auger reactor during pyrolysis at 500 °C was reported. As the first condenser temperature was augmented from 40 and 80 °C, the bio-oil yield obtained decreased from 30 to 16 wt% and the aqueous phase yield in the second condenser (kept at 25 °C) increased from 27 till 37 wt%. When the untreated biomass was pyrolyzed, the aqueous phase collected in the second condenser (at the first condenser operated at 80 °C) was anaerobically digested at 100 ppm for 400 h results in 31.3 NmL of CH4/batch. However, the best result was attained after washed biomass with acetic acid (10%) previously to fast pyrolysis, obtaining 86.8 NmL of CH4/batch using just 10 ppm, perhaps due to halved of formed hydroxyacetaldehyde and estimated levoglucosan content increases by more than three times at this condition. Thus, the attained results confirmed the viability of the adopted strategy to improve the anaerobic digestion of the aqueous phase obtained by fractional condensation systems for biomethane production. [ABSTRACT FROM AUTHOR]

• The first report on alkaline recovery of biogas absorbent by thermal decomposition. • CO 2 and H 2 S separation efficiency during thermal decomposition was 36.87 % and 100 %. • Maximum pH of 10.5 was recovered from the spent absorbent. • Alkaline recovery rate in semi pilot thermal decomposition reactor was investigated. • Biogas upgrading efficiency was not affected by using the recovered absorbent. A process to upgrade a biogas product to biomethane has been investigated. Recycling of an absorbent is important for low-cost upgrading of biogas by chemical absorption. This study investigated the alkaline recovery of absorbent solution by thermal decomposition at various temperatures (75, 85 and 95 °C) and various vacuum levels (0.2, 0.4 and 0.6 bar). During heating, CO 2 and H 2 S were released from the absorbent solution, which increased the pH. The highest pH 10.58 was reached for NaHCO 3 solution from initial pH 8.86 when treated at 95 °C and 0.6 bar vacuum level (gauge pressure). The mass fraction of CO 3 2− in the solution increased from 0.06 to 0.78. Experiments on H 2 S removal from NaHS solution gave the highest pH 10.38 at 95 °C and 0.6 bar vacuum pressure. Moreover, the performance of the recovered alkaline solution was tested in biogas absorption. The results show that CO 2 and H 2 S removal efficiencies of alkaline solution before and after recovery were similar, at 80 and 99 % respectively. This study demonstrated that thermal decomposition has high potential for recovering the alkaline used absorbent, for recirculation back into the absorption process. [ABSTRACT FROM AUTHOR]

With the invasion of green tide, there were millions of tons of Enteromorpha prolifera (Enteromorpha) that need to be disposed of. An efficient microecological system for Enteromorpha fermentation was constructed using Saccharomyces cerevisiae (S. cerevisiae) and granular sludge at mesophilic condition (35 °C). In order to investigate the influence of S. cerevisiae dosage on fermentation, biomethane production and variations in dissolved organic matter (DOM) were investigated. The results indicated that the microecosystem with added S. cerevisiae exhibited improved fermentation capacity. Specifically, biomethane production was improved by 18%, with a maximum methane yield of 331 mL/g VS, and the time required to reach 90% methane yield was reduced by 41%. There were positive linear relationships between S. cerevisiae dosage and the efficiency of hydrolysis, acidogenesis, acetogenesis, and methanogenesis (R2 > 0.9). According to theoretical calculations, there was a positive effect of lower S. cerevisiae dosage (less than 0.93 g/g TS) on biomethane production, and excess dosage (more than 0.93 g/g TS) led to a negative effect due to volatile fatty acid (VFA) accumulation. The excitation–emission matrix (EEM) indicated that the humification index (HIX) and fulvic acid (FA) percentage of fluorescence regional integration in the system were decreased because the quinone and ketone groups of the FA accepted electrons from S. cerevisiae. These findings suggested that this microecosystem can accelerate fermentation speed (41%) and increase biomethane output (18.2%). [ABSTRACT FROM AUTHOR]

Laboratory findings on the reactions of ash from solid municipal waste from aluminium-containing packages of typical food products indicate that the thermodynamic conditions in landfills and the metabolism of various bacterial strains lead to the formation of biomethane. In addition, laboratory measurements have shown that one kilogram of the waste ashes monitored generates 182 l of methane on average, which considering its relative radiation power corresponds to 9.0 kg of burnt brown coal. This implies the substantial influence of the resulting biomethane on the greenhouse effect when these waste ashes are landfilled. [ABSTRACT FROM AUTHOR]

• A novel technology using a superacid solvent is proposed to purify biogas streams. • Superacid solvent eliminates COVNMs, siloxanes, H 2 S and partially CO 2 from biogas. • Process simulations and hydrodynamic analyses confirm the technology feasibility. • Superacid process shows lower energy demands than other solvents (methanol and MEA). A novel purification technology for raw biogas streams is proposed and it is based on the use of a superacid solution within a bubble column reactor. The solvent is a mixture of sulfuric acid (H 2 SO 4(aq) , 95.0 -->wt.%) and acetic acid glacial (CH 3 COOH (l) , ≥ 99.8 -->vol.%), both commercial grades. A mixture with a molar ratio of 9/1 for H 2 SO 4(aq) , / CH 3 COOH (l) respectively, leads to the interesting physical and chemical absorption properties for biogas treatment. Process simulations of the technology within a frequently used biomethane production process showed simultaneous capabilities for H 2 S elimination, CO 2 absorption and, siloxanes and volatile organic compounds (NMVOCs) complete degradation. A single bubble column reactor was designed for treating 500 N m 3 / h of raw biogas with H 2 S content between 400 and 1500 -->ppmv (dry basis) and for handling a solvent volume flow between 10.23 and 23.39 -->L/min, depending on the H 2 S gas content. Proper functioning and hydrodynamic stability of this unit were evaluated in order to avoid possible issues related to bubbles coalescences or break-up, liquid backmixing and mass transfer limitations. Comparison of the proposed technology with methanol-based and monoethanolamine (MEA (aq))-based absorption processes allowed proving the low energy demands of the proposed unit and the feasible implementation of the technology. [ABSTRACT FROM AUTHOR]

Biogas is a promising renewable energy resource produced by using anaerobic digestion of organic substrates and it is mainly used to generate electricity by means of biogas engines. Other potential utilisations are growing, e.g. grid injection and biofuels production but, generally, a treatment aimed to increase its quality is mandatory and greater investments are generally required to produce upgraded biogas (biomethane). Despite the increasing of interest on these applications, a lack of information is still present from an economic point of view. The present paper performs an extended economic assessment of upgrading and selling biogas starting from a typical farm-based anaerobic digestion plant in Northern Ireland assumed as reference. Several economic indexes have been considered to assess the economic performance of the upgraded anaerobic digestion plant, namely net present value, pay-back period, profitability index and internal rate of return. Moreover, different scenarios in terms of fossil fuel prices have been analysed. The results show that producing and selling biomethane can be economically feasible if an adequate market is fostered. Optimum anaerobic digestion sizes between 26.9 and 64.4 tonne/y have been found, with correspondent net present value and pay-back period values in the range of £6.7–64.4M and 2.8–7.5 years, respectively, depending on the price scenarios analysed and the economic index chosen. Generally, adopting the net present value as objective function of the optimisation leads to greater anaerobic digestion size than the other indexes for any price scenarios considered. Finally, tougher market conditions (i.e. higher fossil fuel prices) lead to better economic performances of the upgraded anaerobic digestion configuration. [ABSTRACT FROM AUTHOR]

Dual-fuel engines present an opportunity to increase the electric efficiency and fuel flexibility of combined-heat-and-power (CHP) units. It is becoming increasingly important to find alternative liquid fuels, which can be used as a pilot fuel is such units. While being able to be produced from renewable sources, polyoxymethylenedimethylethers (PODE , OME or POMDME) also provide promising combustion characteristics, such as reducing particle matter emissions (PM). However, little knowledge exists regarding the utilisation of these fuels in full-scale engines, as used in CHP-units. Therefore, we investigated the performance, combustion behaviour and exhaust emissions of a dual-fuel CHP-engine operating with biomethane as main fuel and a 50/50-PODE-blend and neat diesel as pilot fuel. The injection behaviour of the PODE -diesel-blends was investigated on a common-rail-injection test-bench. When replicating small injection quantities, as required for pilot injection, the injection rate was found to be almost identical when comparing diesel and the PODE -diesel-blend. The pilot fuel quantity showed to be decisive for performance and emissions of the engine. When keeping the injected energy equal between the PODE-blend and diesel, the NO X -emissions increased by up to 45% and the PM-emissions decreased by up to 67%, while the efficiency of the engine increased by up to 2.5%. • Dual fuel CHP unit running on biomethane and PODE-diesel blend as pilot fuel. • Almost identical injection rate of diesel and PODE-blend when injecting small quantities. • Decrease of PM emissions when using PODE-diesel-blend as pilot fuel. • Increase of BTE when using PODE-diesel blend as pilot fuel. • Gas combustion is faster when PODE-diesel-blend is used as pilot fuel. [ABSTRACT FROM AUTHOR]

Opuntia ficus-indica can grow in arid and semi-arid environments characterized by low water and nutrients availability. These features make it a more sustainable alternative to the common energy crops for biorefinery purposes. This work focused on the potential benefits of anaerobic processes applied to this plant. Specifically, it considered i) the substrate preparation, demonstrating the effect of the apparent viscosity on the process; ii) the evaluation of biomethane, Volatile Fatty Acids (VFAs), and caproic acid production in semi-continuous mode at different hydraulic retention times; iii) the purification of the Fatty Acids-rich output through pressure-driven membrane filtration. The rheology analysis found that a 5 %w/w water dilution of the substrate is needed to lower the apparent viscosity to 173 cP, which is below the acceptable apparent viscosity level of 200 cP for a good bioreactor mixing. Keeping this condition, the semi-continuous trials with the best biomethane performance was at HRT of 20 days, with 210 mLCH 4 /gVS and 232 mLCH 4 /gCOD in of production and specific yield, respectively. The VFAs and caproic acid production reached their best at Hydraulic Retention Time 5, with 26 and 7.9 gCOD/L of VFAs and caproic acid, corresponding to specific yields of 79 and 30 % respectively. Pressure-driven filtration at 330 kDa allowed to obtain a permeate with a VFAs and caproic acid content of 96.72%w/w. Finally, the adsorption and desorption tests allowed to separate caproic acid from the permeate and to concentrate it from about 7.5 g COD /L to about 26 g COD /L. [Display omitted] • Opuntia Ficus Indica was valorized for multiple bioproducts and biofuels productions. • Caproic acid and methane were maximized at HRT 5 and 20 days, respectively. • The yields of VFAs and caproic acid were of 79 % and 30 % on COD base, respectively. • 300 kDa filtration allowed to obtain a medium of about 97 % of only VFAs. • Activated carbons led to a complete separation of caproic acid from the other VFAs. [ABSTRACT FROM AUTHOR]

• Methane-based fuels prospects in the Brazilian market. • Engine bench testing across varied load conditions and compression ratios. • Performance evaluation across conventional fuels like ethanol and gasoline. • Assessing combustion characteristics and emissions among tested fuels. • Economic viability analysis based on cost per kWh for each fuel. Brazil has a long history of using biofuels in the transport sector, especially due to the 40 years widespread use of ethanol and almost 20 years of biodiesel. Nevertheless, more efforts are needed to reduce even further the carbon emissions of the transport sector. In addition to ethanol, gaseous fuels such as biogas and biomethane are gaining ground due to their great potential to be obtained through biomass processing. To prospect the potential use of biomethane as a vehicle fuel in Brazil, compressed natural gas (CNG), another methane-based fuel with similar composition to biomethane, was tested and had its performance and emissions compared to hydrous ethanol and Brazilian gasoline at three different operating conditions in two different compression ratios: 3.0 bar, 6.0 bar and 9.0 bar IMEP at 1800 rpm, exploring compression ratios of 11.6:1 and 14.3:1. With CNG, engine operation at MBT was possible with both compression ratios. Ethanol presented border knock near MBT for the highest compression ratio and load, while the gasoline spark timing was knock-limited for both compression ratios at the highest load. Indicated efficiency of CNG was higher than that of gasoline and lower than that of hydrous ethanol. ISCO emissions were lower for CNG, while ISTHC and ISNO X were similar to gasoline. Due to the lower LHV of biomethane, a reduction in the ISNOX value could be expected with possible increase in methane slip. Regarding cost, biomethane is the fuel with the cheapest operating cost per kWh when considering the final price for industrial consumers in Brazil. It is still difficult to estimate large-scale production cost of biomethane, but its use in partial replacement of CNG would still be able to keep fuel market competitiveness, while reducing the carbon footprint. [ABSTRACT FROM AUTHOR]

The generation of bioenergy from thin stillage in a corn ethanol mill provides a new perspective for the use of by-products in a circular economy concept. Alternative technological routes for the corn ethanol by-products energy and nutrients recovery must be investigated to assess present and future decision-making toward economic and environmental indicators. The theoretical biogas production from an up-flow anaerobic sludge blanket (UASB) reactor in a corn-ethanol mill and the potential thermal and electrical power generation along with the avoided greenhouse gas (GHG) emissions were estimated for a large-scale industrial facility. This work aimed to assess the anaerobic digestion (AD) contribution to techno-economic indicators of a corn ethanol mill in three scenarios: 1) Standard corn-to-ethanol mill; 2) AD-CHP - thin stillage AD to produce biogas and its burning in a combined heat and power (CHP) system; 3) AD-BU - biogas purification to obtain and commercialize biomethane. The existent Brazilian market and fuels and biofuel policies place the system without AD in a slightly better position when analyzing financial indicators related to investment return. In contrast, the global energy and mass balances considering thin stillage AD showed that in the AD-CHP scenario, processing 1 ton of thin stillage would produce 10.37 m³ of biogas, which could generate 119.9 MJ of heat and 24.7 kWh of electricity in a CHP system, favoring a greener energy scenario. The energy recovered from biogas returns to the industry, supplying 7.15% of the heat required for steam production and 52.74% of the electricity requirement for industrial processing. As a renewable energy source, biogas would replace fossil sources for energy generation avoiding GHG emissions. Extrapolating the results of the present work to the Brazilian national scale, the biogas yield from the corn-to-ethanol industry would be 179.68 million m³ , the thermal energy generation from biogas could mitigate 125,574.42 ton CO 2eq , and the electricity replacement could mitigate 58,193.02 ton CO 2eq. Besides the mentioned energy generation and environmental benefits, the financial indicators for the examined scenarios showed that the Brazilian market and public policies related to biogas/biomethane are constraints to overcoming to larger adoption of AD by the corn-to-ethanol industry. [Display omitted] • Biogas production could be an option for corn-to-ethanol mill's. • Thermal energy could supply 7.15% of the heat required for steam production. • Electric energy could supply 52.74% of the requirement for the mill. • All the studied scenarios are profitable. [ABSTRACT FROM AUTHOR]