Search results for: specific methane production

Authors: S. Jaikeaw, S. Chavadej

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The objective of this study was to determine the effects of COD loading rate on hydrogen and methane production and micronutrient transportation using a two-stage upflow anaerobic sludge blanket (UASB) system under mesophilic temperature (37°C) with a constant recycle ratio of 1:1 (final effluent flow rate: feed flow rate). The first (hydrogen) UASB unit having 4 L liquid holding volume was controlled at pH 5.5 but the second (methane) UASB unit having 24 L liquid holding volume had no pH control. The two-stage UASB system operated at different COD loading rates from 8 to 20 kg/m³d based on total UASB working volume. The results showed that, at the optimum COD loading rate of 13 kg/m³d, the produced gas from the hydrogen UASB unit contained 1.5% H₂, 16.5% CH₄, and 82% CO₂ with H₂S of 252 ppm and also provided a hydrogen yield of 1.66 mL/g COD removed (or 0.56 mL/g COD applied) and a specific hydrogen production rate of 156.85 ml H₂/LRd (or 5.12 ml H₂/g MLVSS d). Under the optimum COD loading rate, the produced gas from the methane UASB unit mainly contained methane and carbon dioxide without hydrogen of 74 and 26%, respectively with hydrogen sulfide of 287 ppm and the system also provided a maximum methane yield of 407.00 mL/g COD removed (or 263.23 mL/g COD applied) and a specific methane production rate of 2081.44 ml CH₄/LRd (or 99.75 ml CH₄/g MLVSS d). Under the optimum COD loading rate, all micronutrients markedly dropped by the sulfide precipitation reactions. The reduction of micronutrients mostly appeared in the methane UASB unit. Under the studied conditions, both Co and Ni were found to be greatly precipitated out, causing the deficiency to microbial activity. It is hypothesized that an addition of both Co and Ni can improve the methanogenic activity.

Keywords: hydrogen and methane production, ethanol wastewater, a two-stage upflow anaerobic blanket (UASB) system, mesophillic temperature, microbial concentration (MLVSS), micronutrients

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Authors: Abdelatif Gadoum, Djilali Benyoucef, Mouloudj Hadj, Alla Eddine Toubal Maamar, Mohamed Habib Allah Lahoual

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Hydrogen occurs naturally in the form of chemical compounds, most often in water and hydrocarbons. The main objective of this study is 2D modeling of hydrogen production in inductively coupled plasma in methane at low pressure. In the present model, we include the motions and the collisions of both neutral and charged particles by considering 19 species (i.e in total ; neutrals, radicals, ions, and electrons), and more than 120 reactions (electron impact with methane, neutral-neutral, neutral-ions and surface reactions). The results show that the rate conversion of methane reach 90% and the hydrogen production is about 30%.

Keywords: hydrogen production, inductively coupled plasma, fluid model, methane plasma

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Authors: Yun-Ho Ahn, Hyery Kang, Dong-Yeun Koh, Huen Lee

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In this study, we demonstrate the production of natural gas hydrates from permeable marine sediments with simultaneous mechanisms for methane recovery and methane-air or methane-air/carbon dioxide replacement. The simultaneous melting happens until the chemical potentials become equal in both phases as natural gas hydrate depletion continues and self-regulated methane-air replacement occurs over an arbitrary point. We observed certain point between dissociation and replacement mechanisms in the natural gas hydrate reservoir, and we call this boundary as critical methane concentration. By the way, when carbon dioxide was added, the process of chemical exchange of methane by air/carbon dioxide was observed in the natural gas hydrate. The suggested process will operate well for most global natural gas hydrate reservoirs, regardless of the operating conditions or geometrical constraints.

Keywords: air injection, carbon dioxide sequestration, hydrate production, natural gas hydrate

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Authors: Ahn Yun-Ho, Hyery Kang, Koh Dong-Yeun, Huen Lee

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In this study, we demonstrate the production of natural gas hydrates from permeable marine sediments with simultaneous mechanisms for methane recovery and methane-air or methane-air/carbon dioxide replacement. The simultaneous melting happens until the chemical potentials become equal in both phases as natural gas hydrate depletion continues and self-regulated methane-air replacement occurs over an arbitrary point. We observed certain point between dissociation and replacement mechanisms in the natural gas hydrate reservoir, and we call this boundary as critical methane concentration. By the way, when carbon dioxide was added, the process of chemical exchange of methane by air/carbon dioxide was observed in the natural gas hydrate. The suggested process will operate well for most global natural gas hydrate reservoirs, regardless of the operating conditions or geometrical constraints.

Keywords: air injection, carbon dioxide sequestration, hydrate production, natural gas hydrate

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Authors: E. Al-Essa, R. Bello-Mendoza, D. G. Wareham

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Anaerobic batch experiments were conducted to investigate the effect of magnetite-supplementation (7 mM) on methane production from digested sludge undergoing two different microbial growth phases, namely fresh sludge (exponential growth phase) and degassed sludge (endogenous decay phase). Three different particle sizes were assessed: small (50 - 150 nm), medium (168 – 490 nm) and large (800 nm - 4.5 µm) particles. Results show that, in the case of the fresh sludge, magnetite significantly enhanced the methane production rate (up to 32%) and reduced the lag phase (by 15% - 41%) as compared to the control, regardless of the particle size used. However, the cumulative methane produced at the end of the incubation was comparable in all treatment and control bottles. In the case of the degassed sludge, only the medium-sized magnetite particles increased significantly the methane production rate (12% higher) as compared to the control. Small and large particles had little effect on the methane production rate but did result in an extended lag phase which led to significantly lower cumulative methane production at the end of the incubation period. These results suggest that magnetite produces a clear and positive effect on methane production only when an active and balanced microbial community is present in the anaerobic digester. It is concluded that, (i) the effect of magnetite particle size on increasing the methane production rate and reducing lag phase duration is strongly influenced by the initial metabolic state of the microbial consortium, and (ii) the particle size would positively affect the methane production if it is provided within the nanometer size range.

Keywords: anaerobic digestion, iron oxide, methanogenesis, nanoparticle

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Authors: Cristina Rodriguez, Abed Alaswad, Zaki El-Hassan, Abdul G. Olabi

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This study investigates the effect on methane production from the waste paper when co-digested with macroalgal biomass as a source of nitrogen. Both feedstocks were previously mechanically pretreated in order to reduce their particle size. Methane potential assays were carried out at laboratory scale in batch mode for 28 days. The study was planned according to two factors: the feedstock to inoculum (F/I) ratio and the waste paper to macroalgae (WP/MA) ratio. The F/I ratios checked were 0.2, 0.3 and 0.4 and the WP/MA ratios were 0:100, 25:75, 50:50, 75:25 and 100:0. The highest methane yield (608 ml/g of volatile solids (VS)) was achieved at an F/I ratio of 0.2 and a WP/MA ratio of 50:50. The methane yield at a ratio WP/MA of 50:50 is higher than for single compound, while for ratios WP/MA of 25:75 and 75:25 the methane yield decreases compared to biomass mono-digestion. This behavior is observed for the three levels of F/I ratio being more noticeable at F/I ratio of 0.3. A synergistic effect was found for the WP/MA ratio of 50:50 and all F/I ratios and for WP/MA=50:50 and F/I=0.2. A maximum increase of methane yield of 49.58% was found for a co-digestion ratio of 50:50 and an F/I ratio of 0.4. It was concluded that methane production from waste paper improves significantly when co-digested with macroalgae biomass. The methane yields from co-digestion were also found higher that from macroalgae mono-digestion.

Keywords: anaerobic co-digestion, biogas, macroalgae, waste paper

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Authors: Khalid Elbadawi Elshafea, Mahmoud Hassan Onsa

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This paper presents the results of the experiments to measure the impact of pasteurization cows dung on important parameter of anaerobic digestion (retention time) and measure the effect in daily production rate of biogas, were used local materials in these experiments, two experiments were carried out in two bio-digesters (1 and 2) (18.0 L), volume of the mixture 16.0-litre and the mass of dry matter in the mixture 4.0 Kg of cow dung. Pasteurization process has been conducted on the mixture into the digester 2, and put two digesters under room temperature. Digester (1) produced 268.5 liter of methane in period of 49 days with daily methane production rate 1.37L/Kg/day, and digester (2) produced 302.7-liter of methane in period of 26 days with daily methane production rate 2.91 L/Kg/day. This study concluded that the use of system pasteurization cows dung speed up hydrolysis in anaerobic process, because heat to certain temperature in certain time lead to speed up chemical reactions (transfer Protein to Amino acids, Carbohydrate to Sugars and Fat to Long chain fatty acids), this lead to reduce the retention time an therefore increase the daily methane production rate with 212%.

Keywords: methane, cow dung, daily production, pasteurization, increase

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Authors: S. H. Nguyen, L. Li, R. S. Hegarty

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Two experiments were conducted assessing the effects of presence or absence of rumen protozoa and dietary nitrate addition on rumen fermentation characteristics and methane production in Brahman heifers. The first experiment assessed changes in rumen fermentation pattern and in-vitro methane production post-refaunation and the second experiment investigated whether addition of nitrate to the incubation would give rise to methane mitigation additional to that contributed by defaunation. Ten Brahman heifers were progressively adapted to a diet containing coconut oil distillate 4.5% (COD) for 18 d and then all heifers were defaunated using sodium 1-(2-sulfonatooxyethoxy) dodecane (Empicol). After 15 d, the heifers were given a second dose of Empicol. Fifteen days after the second dosing, all heifers were allocated to defaunated or refaunated groups by stratified randomisation. On d 48, an oral dose of rumen fluid collected from unrelated faunated cattle was used to inoculate 5 heifers and form a refaunated group so that the effects of re-establishment of protozoa on fermentation characteristics could be investigated. Samples of rumen fluid collected from each animal using oesophageal intubation before feeding on d 48, 55, 62 and 69 were incubated for 23h in-vitro (experiment 1). On day 82, 2% of NO3 (as NaNO3) was included in in-vitro incubations (experiment 2) to test for additivity of NO3 and absence of protozoa effects on fermentation and methane production. It was concluded that increasing protozoal numbers were associated with increased methane production, with methane production rate significantly higher from refaunated heifers than from defaunated heifers 7, 14 and 21 d after refaunation. Concentration and proportions of major VFA, however, were not affected by protozoal treatments. There is scope for further reducing methane output through combining defaunation and dietary nitrate as the addition of nitrate in the defaunated heifers resulted in 86% reduction in methane production in-vitro.

Keywords: defaunation, nitrate, fermentation, methane production

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Authors: Lazic Marina, Sugden Scott, Sharma Kanta Hem, Sauvageau Dominic, Stein Lisa

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Methane is a highly potent greenhouse gas mostly released through anthropogenic activities. Methane represents a low-cost and sustainable feedstock used for the biological production of value-added compounds by bacteria known as methanotrophs. In addition to methane, these organisms can utilize methanol, another cheap carbon source that is a common industrial by-product. Alphaproteobacteria methanotrophs can utilize both methane and methanol to produce the biopolymer polyhydroxybutyrate. The goal of this study was to examine the effect of methanol on polyhydroxybutyrate production in Methylocystis sp. Rockwell and to identify the optimal methane: methanol ratio that will improve PHB without reducing biomass production. Three methane: methanol ratios (4, 2.5., and 0.5) and three nitrogen source (ammonium or nitrate) concentrations (10 mM, 1 mM, and 0.1 mM) were combined to generate 18 growing conditions (9 per carbon source). The production of polyhydroxybutyrate and biomass was analyzed at the end of growth. Overall, the methane: methanol ratios that promoted polyhydroxybutyrate synthesis without reducing biomass were 4 and 2.5 and the optimal nitrogen concentration was 1 mM for both ammonium and nitrate. The physiological mechanism behind the beneficial effect of combining methane and methanol as carbon sources remain to be discovered. One possibility is that methanol has a dual role as a carbon source at lower concentrations and as a stringent response trigger at higher concentrations. Nevertheless, the beneficial effect of methanol and optimal nitrogen concentration for PHB production was confirmed, providing a basis for future physiological analysis and conditions for process scale-up.

Keywords: methane, methanol, methanotrophs, polyhydroxybutyrate, methylocystis sp. rockwell, single carbon bioconversions

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Authors: N. Lovanh, J. Loughrin, G. Ruiz-Aguilar

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Animal wastes can serve as the feedstock for biogas production (mainly methane) that could be used as alternative energy source. The green energy derived from animal wastes is considered to be carbon neutral and offsetting those generated from fossil fuels. In this study, an evaluation of system parameters on methane production from anaerobic digesters utilizing poultry rendering plant wastewater was carried out. Anaerobic batch reactors and continuous flow system subjected to different operation conditions (i.e., flow rate, temperature, and etc.) containing poultry rendering wastewater were set up to evaluate methane potential from each scenario. Biogas productions were sampled and monitored by gas chromatography and photoacoustic gas analyzer over six months of operation. The results showed that methane productions increased as the temperature increased. However, there is an upper limit to the increase in the temperature on the methane production. Flow rates and type of systems (batch vs. plug-flow regime) also had a major effect on methane production. Constant biogas production was observed in plug-flow system whereas batch system produced biogas quicker and tapering off toward the end of the six-month study. Based on these results, it is paramount to consider operating conditions and system setup in optimizing biogas production from agricultural wastewater.

Keywords: anaerobic digestion, methane, poultry rendering wastewater, biotechnology

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Authors: Ahmed I. Osman, Jehad K. Abu-Dahrieh, Jillian M. Thompson, David W. Rooney

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Natural gas (the main constituent is Methane 95%) is considered as an alternative to petroleum for the production of synthetics fuels. Nowadays, methane combustion at low temperature has received much attention however; it is the most difficult hydrocarbon to be combusted. Co/Mo and (4:1 wt/wt) catalysts were prepared from a range of different precursors and used for the low temperature total methane oxidation (TMO). The catalysts were characterized by, XRD, BET and H2-TPR and tested under reaction temperatures of 250-400 °C with a GHSV= 36,000 mL g-1 h-1. It was found that the combustion temperature was dependent on the type of the precursor, and that those containing chloride led to catalysts with lower activity. The optimum catalyst was Co/Mo (4:1wt/wt) where greater than 20% methane conversion was observed at 250 °C. This catalyst showed a high degree of stability for TMO, showing no deactivation during 50 hours of time on stream.

Keywords: methane low temperature total oxidation, oxygen carrier, Co/Mo, Co/Mn

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Authors: Philip Vercoe, Ali Hardan

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Samples of 29 Australian wild natives and exotic plants were tested in vitro batch rumen culture system for their methanogenic characteristics and potential usage as feed or antimicrobial to enhance sustainable livestock ruminant production system. The plants were tested for their in vitro rumen fermentation end products properties which include: methane production, total gas pressure, concentrations of total volatile fatty acids, ammonia, and acetate to propionate ratio. All of the plants were produced less methane than the positive control (i.e., oaten chaff) in vitro. Nearly 50 % of plants inhibiting methane by over 50% in comparison to the control. Eremophila granitica had the strongest inhibitory effect about 92 % on methane production comparing with oaten chaff. The exotic weed Arctotheca calendula (Capeweed) had the highest concentration of volatile fatty acids production as well as the highest in total gas pressure among all plants and the control. Some of the acacia species have the lowest production of total gas pressure. The majority of the plants produced more ammonia than the oaten chaff control. The plant species that produced the most ammonia was Codonocarpus cotinifolius, producing over 3 times as much methane as oaten chaff control while the lowest was Eremophila galeata. There was strong positive correlation between methane production and total gas production as well as between total gas production and the concentration of VFA produced with R² = 0.74, R² = 0.84, respectively. While there was weak positive correlation between methane production and the acetate to propionate ratio as well as between the concentration of VFA produced and methane production with R² = 0.41, R² = 0.52, respectively.

Keywords: in vitro Rumen Fermentation, methane, wild Australian native plants, forages

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Authors: Md. Nurul Islam Siddique, A. W. Zularisam

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The effect of gradual increase in organic loading rate (OLR) and temperature on biomethanation from petrochemical wastewater treatment was investigated using CSTR. The digester performance was measured at hydraulic retention time (HRT) of 4 to 2d, and start up procedure of the reactor was monitored for 60 days via chemical oxygen demand (COD) removal, biogas and methane production. By enhancing the temperature from 30 to 55 ˚C Thermophilic condition was attained, and pH was adjusted at 7 ± 0.5 during the experiment. Supreme COD removal competence was 98±0.5% (r = 0.84) at an OLR of 7.5 g-COD/Ld and 4d HRT. Biogas and methane yield were logged to an extreme of 0.80 L/g-CODremoved d (r = 0.81), 0.60 L/g-CODremoved d (r = 0.83), and mean methane content of biogas was 65.49%. The full acclimatization was established at 55 ˚C with high COD removal efficiency and biogas production. An OLR of 7.5 g-COD/L d and HRT of 4 days were apposite for petrochemical wastewater treatment.

Keywords: anaerobic digestion, petrochemical wastewater, CSTR, methane

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Authors: Syazwani Idrus, S. Charles J. Banks, Sonia Heaven

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The study compared the performance of upflow anaerobic sludge blanket (UASB) reactors and anaerobic filters (AF) for the treatment of wheat straw washwater (WSW) which has a high concentration of Potassium ions. The trial was conducted at mesophilic temperatures (37 °C). The digesters were started up over a 48-day period using a synthetic wastewater feed and reached an organic loading rate (OLR) of 6 g COD L^-1 day^-1 with a specific methane production (SMP) of 0.333 L CH4 g^-1 COD. When the feed was switched to WSW it was not possible to maintain the same loading rate as the SMP in all reactors fell sharply to less than 0.1 L CH4 g^-1 COD, with the AF affected more than the UASB. On reducing the OLR to 3 g COD L^-1 day^-1 the reactors recovered to produce 0.21 L CH4 g^-1 CODadded and gave 82% COD removal. A discrepancy between the COD consumed and the methane produced could be accounted for through increased maintenance energy requirement of the microbial community for osmo-regulation as K+ was found to accumulate in the sludge and in the UASB reached a concentration of 4.5 mg K g^-1 wet weight of granules.

Keywords: anaerobic digestion, osmotic stress, chemical oxygen demand, specific methane production

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Authors: Passkorn Khanthongthip, John T. Novak

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Many studies have been reported that the nZVI and MgO NPs were often found in waste activated sludge (WAS). However, little is known about the impact of those NPs on WAS stabilization. The aims of this study were to investigate the effects of both NPs on WAS anaerobic digestion for methane production and to examine the change of metanogenic population under those different environments using qPCR. Four dosages (2, 50, 100, and 200 mg/g-TSS) of MgO NPs were added to four different bottles containing WAS to investigate the impact of MgO NPs on methane production during WAS anaerobic digestion. The effects of nZVI on methane production during WAS anaerobic digestion were also conducted in another four bottles using the same methods described above except that the MgO NPs were replaced by nZVI. A bottle of WAS anaerobic digestion without nanoparticles addition was also operated to serve as a control. It was found that the relative amounts, compared to the control system, of methane production in each WAS anaerobic digestion bottle adding 2, 50, 100, 200 mg/gTSS MgO NPs were 98, 62, 28, and 14 %, respectively. This suggests that higher MgO NPs resulted in lower methane production. The data of batch test for the effects of corresponding released Mg2+ indicated that 50 mg/gTSS MgO NPs or higher could inhibit methane production at least 25%. Moreover, the volatile fatty acid (VFA) concentration was 328, 384, 928, 3,684, and 7,848 mg/L for the control and four WAS anaerobic digestion bottles with 2, 50, 100, 200 mg/gTSS MgO NPs addition, respectively. Higher VFA concentration could reduce pH and subsequently decrease methanogen growth, resulting in lower methane production. The relative numbers of total gene copies of methanogens analyzed from samples taken from WAS anaerobic digestion bottles were approximately 99, 68, 38, and 24 % of control for the addition of 2, 50, 100, and 200 mg/gTSS, respectively. Obviously, the more MgO NPs appeared in sludge anaerobic digestion system, the less methanogens remained. In contrast, the relative amount of methane production found in another four WAS anaerobic digestion bottles adding 2, 50, 100, and 200 mg/gTSS nZVI were 102, 128, 112, and 104 % of the control, respectively. The measurement of methanogenic population indicated that the relative content of methanogen gene copies were 101, 132, 120, and 112 % of those found in control, respectively. Additionally, the cumulative VFA was 320, 234, 308, and 330 mg/L, respectively. This reveals that nZVI addition could assist to increase methanogenic population. Higher amount of methanogen accelerated VFA degradation for greater methane production, resulting in lower VFA accumulation in digesters. Moreover, the data for effects of corresponding released Fe2+ conducted by batch tests suggest that the addition of approximately 50 mg/gTSS nZVI increased methane production by 20%. In conclusion, the presence of MgO NPs appeared to diminish the methane production during WAS anaerobic digestion. Higher MgO NPs dosages resulted in more inhibition on methane production. In contrast, nZVI addition promoted the amount of methanogenic population which facilitated methane production.

Keywords: magnesium oxide nanoparticles, methane production, methanogenic population, nano zerovalent iron

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Authors: Washaya Soul, Mupangwa John, Mapfumo Lizwell, Muchenje Voster

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Ruminant animals contribute a considerable amount of methane to the atmosphere, which is a cause of concern for global warming. Two studies were conducted in beef and goats where the studies aimed to determine the enteric CH₄ levels from a herd of beef cows raised on semi-arid rangelands and to evaluate the effect of supplementing goats with forage legumes: Vigna unguiculata and Lablab purpureus on enteric methane production. A total of 24 cows were selected from Boran and Nguni cows (n = 12 per breed) from two different farms; parity (P1 – P4) and season (dry vs. wet) were considered predictor variables in the first experiment. Eighteen goats (weaners, 9 males, 9 females) were used, in which sex and forage species were predictor variables in the second experiment. Three treatment diets were used in goats. Methane was measured using a Laser methane detector [LMD] for six consecutive days and repeated once after every three months in beef cows and once every week for 6 weeks in goats during the post-adaptation period. Parity and breed had no effects on CH₄ production in beef cows; however, season significantly influenced CH₄ outputs. Methane production was higher (P<0.05) in the dry compared to the wet season, 31.1CH₄/DMI(g/kg) and 28.8 CH₄/DMI(g/kg) for the dry and wet seasons, respectively. In goats, forage species and sex of the animal affected enteric methane production (P<0.05). Animals produce more gas when ruminating than feeding or just standing for all treatments. The control treatment exhibited higher (P<0.05) methane emissions per kg of DMI. Male goats produced more methane compared to females (17.40L/day; 12.46 g/kg DMI and 0.126g/day) versus (15.47L/day, 12.28 g/kg DMI, 0.0109g/day) respectively. It was concluded that cows produce more CH₄/DMI during the dry season, while forage legumes reduce enteric methane production in goats, and male goats produce more gas compared to females. It is recommended to introduce forage legumes, particularly during the dry season, to reduce the amount of gas produced.

Keywords: beef cows, extensive grazing system, forage legumes, greenhouse gases, goats Laser methane detector.

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Authors: W. Ait Ahmed, M. Aggour, M. Naciri

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Extracting energy from biomass is an important alternative to produce different types of energy (heat, electricity, or both) assuring low pollution and better efficiency. It is a new yet reliable approach to reduce green gas emission by extracting methane from industry effluents and use it to power machinery. We focused in our project on using paper and mill effluents, treated in a UASB reactor. The methane produced is used in the factory’s power supply. The aim of this work is to develop an electronic system using Arduino platform connected to a gas sensor, to measure and display the curve of daily methane production on processing. The sensor will send the gas values in ppm to the Arduino board so that the later sends the RS232 hardware protocol. The code developed with processing will transform the values into a curve and display it on the computer screen.

Keywords: biogas, Arduino, processing, code, methane, gas sensor, program

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Authors: Uchenna Egwu, Paul Jonathan Sallis

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Perennial ryegrass is an abundant renewable lignocellulosic biofuel feedstock for biomethane production through anaerobic digestion (AD). In this study, six anaerobic continuously stirred tank reactors (CSTRs) were set up in three pairs. Each pair of the CSTRs was then used to study the effects of operating temperatures – psychrophilic, mesophilic, and thermophilic, and optimum pH on the specific methane production (SMP) of the ryegrass during AD under discontinuous daily feeding conditions. The reactors were fed at an organic loading rate (OLR) ranging from 1-1.5 kgVS.L⁻¹d⁻¹ and hydraulic residence time, HRT=20 days for 140 days. The pH of the digesters was maintained at the range of 6.8-7.2 using 1 M NH₄HCO₃ solution, but this was replaced with biomass ash-extracts from day 105-140. The results obtained showed that the mean SMP of ryegrass measured between HRT 3 and 4 were 318.4, 425.4 and 335 N L CH₄ kg⁻¹VS.d⁻¹ for the psychrophilic (25 ± 2°C), mesophilic (40 ± 1°C) and thermophilic (60 ± 1°C) temperatures respectively. It was also observed that the buffering ability of the reactors increased with operating temperature, probably due to an increase in the solubility of ammonium bicarbonate (NH₄HCO₃) with temperature. The reactors also achieved a mean VS destruction of 61.9, 68.5 and 63.5%, respectively, which signifies that the mesophilic reactors achieved the highest specific methane production (SMP), while the psychrophilic reactors achieved the lowest. None of the reactors attained steady-state condition due to the discontinuous daily feeding times, and therefore, such feeding practice may not be the most effective for maximum biogas production over long periods of time. The addition of NH₄HCO₃ as supplement provided a good buffering condition in these AD digesters, but the digesters failed in the long run due to inhibition from the accumulation of free ammonia, which later led to decrease in pH, acidification, and souring of the digesters. However, the addition of biomass ash extracts was shown to potentially revive failed AD reactors by providing an adequate buffering and essential trace nutrient supplements necessary for optimal bacterial growth.

Keywords: anaerobic digestion, discontinuous feeding, perennial ryegrass, specific methane production, supplements, temperature

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Authors: Assal E. Haddad

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Food waste samples from Irbid were collected from 5 different sources for 12 weeks to characterize their composition in terms of four food categories; rice, meat, fruits and vegetables, and bread. Average food type compositions were 39% rice, 6% meat, 34% fruits and vegetables, and 23% bread. Methane yield was also measured for all food types and was found to be 362, 499, 352, and 375 mL/g VS for rice, meat, fruits and vegetables, and bread, respectively. A representative food waste sample was created to test the actual methane yield and compare it to calculated one. Actual methane yield (414 mL/g VS) was greater than the calculated value (377 mL/g VS) based on food type proportions and their specific methane yield. This study emphasizes the effect of the types of food and their proportions in food waste on the final biogas production. Findings in this study provide representative methane emission factors for Irbid’s food waste, which represent as high as 68% of total Municipal Solid Waste (MSW) in Irbid, and also indicate the energy and economic value within the solid waste stream in Irbid.

Keywords: food waste, solid waste management, anaerobic digestion, methane yield

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Authors: Jerome Blackman, Pamela Franklin, Volha Roshchanka

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The US coal mining sector accounts for 6% of total US Methane emissions (2021). 60% of US coal mining methane emissions come from active underground mine ventilation systems. Abandoned mines contribute about 13% of methane emissions from coal mining. While there are thousands of abandoned underground coal mines in the US, the Environmental Protection Agency (EPA) estimates that fewer than 100 have sufficient methane resources for viable methane recovery and use projects. Many abandoned mines are in remote areas far from potential energy customers and may be flooded, further complicating methane recovery. Because these mines are no longer active, recovery projects can be simpler to implement.

Keywords: abandoned mines, coal mine methane, coal mining, methane emissions, methane mitigation, recovery and use

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Authors: Ajay Dwivedi, M. Suresh Kumar, A. N. Vaidya

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The problem of fruit and vegetable waste management is a grave one and with ever increasing need to feed the exponentially growing population, more and more solid waste in the form of fruit and vegetables waste are generated and its management has become one of the key issues in protection of environment. Energy generation from fruit and vegetables waste by dark anaerobic fermentation is a recent an interesting avenue effective management of solid waste as well as for generating free and cheap energy. In the present study 17 vegetables were characterized for their physical as well as chemical properties, these characteristics were used to determine the hydrogen and methane potentials of vegetable from various models, and also lab scale batch experiments were performed to determine their actual hydrogen and methane production capacity. Lab scale batch experiments proved that vegetable waste can be used as effective substrate for bio hydrogen and methane production, however the expected yield of bio hydrogen and methane was much lower than predicted by models, this was due to the fact that other vital experimental parameters such as pH, total solids content, food to microorganism ratio was not optimized.

Keywords: vegetable waste, physico-chemical characteristics, hydrogen, methane

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Authors: Seyed Mohamad Rasool Mirkarimi, David Chiaramonti, Samir Bensaid

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Catalytic methane decomposition (CMD, reaction 4) is a one-step process for hydrogen production where carbon in the methane molecule is sequestered in the form of stable and higher-value carbon materials. Metallic catalysts and carbon-based catalysts are two major types of catalysts utilized for the CDM process. Although carbon-based catalysts have lower activity compared to metallic ones, they are less expensive and offer high thermal stability and strong resistance to chemical impurities such as sulfur. Also, it would require less costly separation methods as some of the carbon-based catalysts may not have an active metal component in them. Since the regeneration of metallic catalysts requires burning of the C on their surfaces, which emits CO/CO2, in some cases, using carbon-based catalysts would be recommended because regeneration can be completely avoided, and the catalyst can be directly used in other processes. This work focuses on the effect of biochar as a carbon-based catalyst for the conversion of methane into hydrogen and carbon. Biochar produced from the pyrolysis of poplar wood and activated biochar are used as catalysts for this process. In order to observe the impact of carbon-based catalysts on methane conversion, methane cracking in the absence and presence of catalysts for a gas stream with different levels of methane concentration should be performed. The results of these experiments prove conversion of methane in the absence of catalysts at 900 °C is negligible, whereas in the presence of biochar and activated biochar, significant growth has been observed. Comparing the results of the tests related to using char and activated char shows the enhancement obtained in BET surface area of the catalyst through activation leads to more than 10 vol.% methane conversion.

Keywords: hydrogen production, catalytic methane decomposition, biochar, activated biochar, carbon-based catalyts

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Authors: D. M. Bassuney, W. A. Ibrahim, Medhat A. E. Moustafa

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Appropriate start-up of an anaerobic baffled reactor (ABR) is considered to be the most delicate and important issue in the anaerobic process, and depends on several factors such as wastewater composition, reactor configuration, inoculum and operating conditions. In this work, the start-up performance of an ABR with working volume of 30 liters, fed continuously with synthetic food industrial wastewater along with semi-batch study to measure the methangenic activity by specific methanogenic activity (SMA) test were carried out at various organic loading rates (OLRs) to determine the best OLR used to start up the reactor. The comparison was based on COD removal efficiencies, start-up time, pH stability and methane production. An OLR of 1.8 Kg COD/m3d (5400 gCOD/m3 and 3 days HRT) showed best overall performance with COD removal efficiency of 94.44% after four days from the feeding and methane production of 3802 ml/L with an overall SMA of 0.36 gCH4-COD/gVS.d

Keywords: anaerobic baffled reactor, anaerobic reactor start-up, food industrial wastewater, specific methanogenic activity

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Authors: Muhammad Adeel Arshad, Faiz-Ul Hassan, Yanfen Cheng

Abstract:

According to FAO, enteric methane (CH4) production is about 44% of all greenhouse gas emissions from the livestock sector. Ruminants produce CH4 as a result of fermentation of feed in the rumen especially from roughages which yield more CH4 per unit of biomass ingested as compared to concentrates. Efficient ruminal fermentation is not possible without abating CO2 and CH4. Methane abatement strategies are required to curb the predicted rise in emissions associated with greater ruminant production in future to meet ever increasing animal protein requirements. Ecology of ruminal methanogenesis and avenues for its mitigation can be identified through various genomic and transcriptomic techniques. Programs such as Hungate1000 and the Global Rumen Census have been launched to enhance our understanding about global ruminal microbial communities. Through Hungate1000 project, a comprehensive reference set of rumen microbial genome sequences has been developed from cultivated rumen bacteria and methanogenic archaea along with representative rumen anaerobic fungi and ciliate protozoa cultures. But still many species of rumen microbes are underrepresented especially uncultivable microbes. Lack of sequence information specific to the rumen's microbial community has inhibited efforts to use genomic data to identify specific set of species and their target genes involved in methanogenesis. Metagenomic and metatranscriptomic study of entire microbial rumen populations offer new perspectives to understand interaction of methanogens with other rumen microbes and their potential association with total gas and methane production. Deep understanding of methanogenic pathway will help to devise potentially effective strategies to abate methane production while increasing feed efficiency in ruminants.

Keywords: Genome sequences, Hungate1000, methanogens, ruminal fermentation

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Authors: Dupe Olufunke Ogunbosoye, Thaofik Badmos Mustapha, Lanre Shaffihy Adeaga, R. O. Imam

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Efforts have been made to reduce ruminants' methane emissions while improving animal productivity. Hence, an experiment was conducted to investigate the in vitro fermentation pattern, methane production, and performance of West African dwarf (WAD) rams-fed diets at graded levels of ginger. Sixteen (16) rams were randomly allocated into four dietary treatments with four animals per treatment in a completely randomized design for 84 days. Ginger powder was added at 0.00%, 0.25%, 0.50% and 0.75% as T1, T2, T3 and T4 respectively. The results indicated that at the 24-hour diet incubation, gas production, methane, metabolizable energy (ME), organic matter digestibility (OMD), and short-chain fatty acids (SCFA) concentrations decreased with the increasing level of ginger. Conversely, the sheep-fed T4 recorded the highest daily weight gain (47.61g/day), while the least daily weight gain (17.86g/day) was recorded in ram-fed T1. The daily weight gain of the rams fed T3 and T4 was similar but significantly different from the daily weight gain in T1 (17.86g/day) and T2 (29.76g/day). Daily feed intake was not significantly different across the treatments. T4 recorded the best response regarding feed conversion ratio (18.59) compared with other treatments. Based on the results obtained, rams fed T4 perform best in terms of growth and methane production. It is therefore concluded that the addition of ginger powder into the diet of sheep up to 0.75% enhances the growth rate of WAD sheep and reduces enteric methane production to create a smart nutrition system in ruminant animal production.

Keywords: enteric methane, growth, in vitro, sheep, nutrition system

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Authors: Yang Li, Mingkai Liu, Qiong Rao, Zhongrui Gai, Ying Pan, Hongguang Jin

Abstract:

Hydrogen is an ideal and potential energy carrier due to its high energy efficiency and low pollution. An alternative and promising approach to hydrogen generation is the chemical looping steam reforming of methane (CL-SRM) over iron-based oxygen carriers. However, the process faces challenges such as high reaction temperature (>850 ℃) and low methane conversion. We demonstrate that Ni-mixed Fe-based oxygen carrier particles have significantly improved the methane conversion and hydrogen production rate in the range of 450-600 ℃ under atmospheric pressure. The effect on the reaction reactivity of oxygen carrier particles mixed with different Ni-based particle mass ratios has been determined in the continuous unit. More than 85% of methane conversion has been achieved at 600 ℃, and hydrogen can be produced in both reduction and oxidation steps. Moreover, the iron-based oxygen carrier particles exhibited good cyclic performance during 150 consecutive redox cycles at 600 ℃. The mid-temperature iron-based oxygen carrier particles, integrated with a moving-bed chemical looping system, might provide a powerful approach toward more efficient and scalable hydrogen production.

Keywords: chemical looping, hydrogen production, mid-temperature, oxygen carrier particles

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Authors: A. Alkattib, M. Boumaza

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Steam reforming is industrially important as it is incorporated in several major chemical processes including the production of ammonia, methanol, hydrogen and ox alcohols. Due to the strongly endothermic nature of the process, a large amount of heat is supplied by fuel burning (commonly natural gas) in the furnace chamber. Reaction conversions, tube catalyst life, energy consumption and CO2 emission represent the principal factors affecting the performance of this unit and are directly influenced by the high operating temperatures and pressures. This study presents a simulation of the performance of the reforming of methane in a primary reformer, through a developed empirical relation which enables to investigate the effects of operating parameters such as the pressure, temperature, steam to carbon ratio on the production of hydrogen, as well as the fraction of non-converted methane. It appears from this analysis that the exit temperature Te, the operating pressure as well the steam to carbon ratio has an important effect on the reforming of methane.

Keywords: reforming, methane, performance, hydrogen, parameters

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Authors: D. Lepe-Cervantes, E. Leon-Becerril, J. Gomez-Romero, O. Garcia-Depraect, A. Lopez-Lopez

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In this study, raw coffee wastewater (CWW) was used as a complex substrate for anaerobic digestion. The inoculum adaptation stage, microbial diversity analysis and biomethane potential (BMP) tests were performed. A fast inoculum adaptation stage was used by the replacement of vinasse to CWW in an anaerobic sequential batch reactor (AnSBR) operated at mesophilic conditions. Illumina MiSeq sequencing was used to analyze the microbial diversity. While, BMP tests using inoculum adapted to CWW were carried out at different inoculum to substrate (I/S) ratios (2:1, 3:1 and 4:1, on a VS basis). Results show that the adaptability percentage was increased gradually until it reaches the highest theoretical value in a short time of 10 d; with a methane yield of 359.10 NmL CH₄/g COD-removed; Methanobacterium beijingense was the most abundant microbial (75%) and the greatest specific methane production was achieved at I/S ratio 4:1, whereas the lowest was obtained at 2:1, with BMP values of 320 NmL CH₄/g VS and 151 NmL CH₄/g VS, respectively. In conclusion, gradual replacement of substrate was a feasible method to adapt the inoculum in a short time even using complex raw substrates, whereas in the BMP tests, the specific methane production was proportional to the initial amount of inoculum.

Keywords: anaerobic digestion, biomethane potential test, coffee wastewater, fast inoculum adaptation

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Authors: Jozef Mindas, Jana Skvareninova

Abstract:

Wetlands are a main natural source of methane emissions, but they also represent the important biodiversity reservoirs in the landscape. There are about 26 thousands hectares of wetlands in Slovakia identified via the wetlands monitoring program. Created database of wetlands in Slovakia allows to analyze several ecological processes including also the methane emissions estimate. Based on the information from the database, the first estimate of the methane emissions from wetlands in Slovakia has been done. The IPCC methodology (Tier 1 approach) has been used with proposed emission factors for the ice-free period derived from the climatic data. The highest methane emissions of nearly 550 Gg are associated with the category of fens. Almost 11 Gg of methane is emitted from bogs, and emissions from flooded lands represent less than 8 Gg.

Keywords: bogs, methane emissions, Slovakia, wetlands

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Authors: K. Abdul Halim, E. L. Yong

Abstract:

Palm oil industry is a major revenue earner in Malaysia, despite the growth of the industry is synonymous with a massive production of agro-industrial wastewater. Through the oil extraction processes, palm oil mill effluent (POME) contributes to the largest liquid wastes generated. Due to the high amount of organic compound, POME can cause inland water pollution if discharged untreated into the water course as well as affect the aquatic ecosystem. For more than 20 years, Malaysia adopted the conventional biological treatment known as lagoon system that apply biological treatment. Besides having difficulties in complying with the standard, a large build up area is needed and retention time is higher. Although anaerobic digester is more favorable, this process comes along with enormous volumes of sludge and methane gas, demanding attention from the mill operators. In order to reduce the sludge production, denitrifiers are to be removed first. Sulfate reducing bacteria has shown the capability to inhibit the growth of methanogens. This is expected to substantially reduce both the sludge and methane production in anaerobic digesters. In this paper, the effectiveness of sulfate reducing bacteria in minimizing sludge and methane will be examined.

Keywords: methane reduction, palm oil mill effluent, sludge minimization, sulfate reducing bacteria, sulfate reduction

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