• Asian-Australasian Journal of Animal Sciences
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• v.21 no.1
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• pp.144-154
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• 2008

The rumen microbial ecosystem produces methane as a result of anaerobic fermentation. Methanogenesis in the rumen is thought to represent a 2-12% loss of energy intake and is estimated to be about 15% of total atmospheric methane emissions. While methanogenesis in the rumen is conducted by methanogens, PCR-based techniques have recently detected many uncultured methanogens which have a broader phylogenetic range than cultured strains isolated from the rumen. Strategies for reduction of methane emissions from the rumen have been proposed. These include 1) control of components in feed, 2) application of feed additives and 3) biological control of rumen fermentation. In any case, although it could be possible that repression of hydrogen-producing reactions leads to abatement of methane production, repression of hydrogen-producing reactions means repression of the activity of rumen fermentation and leads to restrained digestibility of carbohydrates and suppression of microbial growth. Thus, in order to reduce the flow of hydrogen into methane production, hydrogen should be diverted into propionate production via lactate or fumarate.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.4
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• pp.293-305
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• 2017

This experiment was conducted to evaluate the effect of leachate replacement frequency on solid state anaerobic digestion (SSAD) of dairy manure using 22 L volume lab-scale digesters at mesophilic temperature ($37^{\circ}C$) in batch mode. Three different leachate replacement strategies (no replacement, once every three days, and once every nine days) were applied and three digesters per each treatment were operated for 45 days. Results showed that leachate replacement test unit every nine days resulted in 1.6 times more methane production ($53.8N{\cdot}mL\;g^{-1}{\cdot}VS$) from SSAD compared to test unit every three days ($34.0N{\cdot}mL\;g^{-1}{\cdot}VS$). No leachate replacement strategy applied group showed slightly higher methane production ($56.3N{\cdot}mL\;g^{-1}{\cdot}VS$) than every nine days replaced one. When added the methane production potential of replaced leachate itself to the methane produced from digester, leachate replacement every nine days resulted in quite similar methane production ($56.5N{\cdot}mL\;g^{-1}{\cdot}VS$) to no leachate replacement group. Even though methane production potential of replaced leachate itself added to the methane produced from digester, every three days replacement showed only $34N{\cdot}mL$ methane production per gram of volatile solids. These results suggest that farmers do not need to replace leachate during SSAD of dairy manure and sawdust mixture in order to maximize methane production. If there are any concerns with accumulation of inhibiting substances in the digester, the 9-day cycle leachate replacement is appropriate.

• Journal of Korean Society on Water Environment
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• v.40 no.5
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• pp.215-228
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• 2024

Lakes are one of major sources of methane gas due to anaerobic decomposition of organic matter in sediments. Since methane released from lakes is a greenhouse gas, it is necessary to investigate factors affecting methane production of lakes. This study conducted field and incubation experiments in Lake Asan in August and October to determine effects of thermal stratification and sediment organic matter characteristics on methane production. Field experiments measured temperature and dissolved oxygen to determine the formation of thermal stratification of lakes. Methane and organic matter characteristics were analyzed using gas chromatography, Total Organic Carbon (TOC) analyzers, and fluorescence spectroscopy. Incubation experiments under anaerobic conditions used sediment and water samples from the same site. Field results showed higher methane fluxes in August and increased Dissolved Organic Carbon (DOC) concentration closer to Asan Bay seawall. Elevated methane fluxes and DOC concentration resulted from intensified anaerobic decomposition formed by thermal stratification. Incubation results indicated that sediment organic matter characteristics influenced methane flux between sites. Statistical analysis revealed that thermal stratification could be a primary factor affecting methane production of lakes. Characteristics of sediment organic matter with respect to quantity and quality could be factors influencing methane production of lakes. Results of this study can serve as fundamental data for predicting methane emissions from lakes due to climate change and for mitigating lake's contributions to global warming.

• Korean Journal of Environmental Agriculture
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• v.41 no.2
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• pp.71-81
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• 2022

BACKGROUND: Animal manures are one of the biggest sources of greenhouse gases and improper manage-ment of animal wastes contributes to the increasing greenhouse gases in the atmosphere. Con-verting greenhouse gases generated from animal manures to energy is one way of contributing to the net-zero carbon emissions. METHODS AND RESULTS: The potential for methane production from cow manure (CM) was studied by measuring the methane yield using the biochemical methane potential (BMP) test. In particular, the effect of co-digestion using rice straw (RM) on the methane production was studied. The methane yields from the co-digestion of CM and RS were statistically similar to that from the mono-digestion of CM or RS. But there was a synergy effect at the CM:RS ratio of 1:2 and 1:1. This can be attributed to the increased C/N ratio. The changed microbial community structure with the addition of substrates (CM, RS) probably led to the increase in the methane produc-tion. CONCLUSION(S): The methane production potential of the particular CM used in this study was not improved by the addition of RS as a co-substrate. The addition of substrates to the anaerobic sludge promoted the increase in the microbial species having synergetic relationship with methano-gens, and this can partially explain the increase in the methane production with the addition of substrates. Overall, there are needs for further studies to improve the methane yield from CM.

• Journal of Environmental Science International
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• v.33 no.2
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• pp.121-129
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• 2024

The study investigated the effect of thermo-alkaline pretreatment on the solubilization of polyhydroxybutyrate (PHB) and its potential to enhance of thermophilic anaerobic digestion, focusing on biochemical methane potential (BMP) and methane production rate, using two different particle sizes of PHB (1500 ㎛ and 400 ㎛). Thermo-alkaline pretreatment tests were conducted at 90 ℃ for 24 hours with varying NaOH dosages from 0-80% (w/w). BMP tests with untreated PHB exhibited methane production ranging from 150.4~225.4 mL CH₄/g COD and 21.5~24.2 mL CH₄/g VSS/d, indicating higher methane production for smaller particle sizes of PHB, 400 ㎛. Thermo-alkaline pretreatment tests achieved a 95.3% PHB solubilization efficiency when 400 ㎛ PHB particles were treated with 80% NaOH dosage at 90 ℃ for 24 hours. BMP tests with pretreated PHB showed substantial improvement in thermophilic anaerobic digestion, with an increase of up to 112% in BMP and up to 168% in methane production rate. The results suggest that a combined pretreatment process, including physical (400 ㎛ PHB particles) and thermo-alkaline (90 ℃, 40-80% NaOH dosage, and 24 hours reaction time), is required for high-rate thermophilic anaerobic digestion of PHB with enhanced methane production.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.9
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• pp.1255-1259
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• 2004

The objective of this study was to evaluate the effects of halogenated compounds, organic acids, unsaturated fatty acids and their mixtures on in vitro methane production and fermentative characteristics of mixed rumen microorganisms. Agents used in two in vitro experiments were bromoethanesulfonic acid (BES) and pyromellitic diimide (PMDI) as halogenated compound, fumarate and malate as organic acid, and linoleic acid and linolenic acid as unsaturated fatty acid sources. Ruminal fluid collected from a Holstein steer fed tall fescue and concentrate mixtures was incubated at $39^{\circ}C$ for 48 h with addition of those materials. Single supplementation of halogenated compounds, organic acids or unsaturated fatty acids decreased in vitro methane production (p<0.05). The second experiment was designed to investigate effects of combination of one of halogenated compounds and either organic acids or fatty acids on methane production. Lower concentration of methane and lower A:P ratio were observed with PMDI compared with BES (p<0.01). In general medium pH, VFA, total gas and hydrogen production, and dry matter degradability were affected by addition of the same compounds. In addition, PMDI+malate treatment resulted in the highest molar proportion of propionate, and lowest A:P ratio and methane production (p<0.01). Hydrogen production was highest in PMDI+linolenic acid and lowest in BES+malate treatment (p<0.01). PMDI+malate combination was the most recommendable in reducing methane production without too much influence on digestibility under conditions of present studies.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.7
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• pp.1043-1047
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• 2009

Three experiments were conducted to determine the conversion rate of formic and acetic acids into methane in the gastrointestinal tracts of geese. In experiment I, two sets of two 4-month-old male White Roman geese were allocated to one of two treatment groups. Each set of geese was inoculated either with formic acid or with phosphate buffer solution (PBS). After the acid or the PBS was inoculated into the esophagi of the geese, two birds from each treatment were placed in a respiratory chamber as a measurement unit for 4 h in order to determine methane production rate. In experiment II and III, 6- and 7-wk-old male White Roman goslings were used, respectively. Birds were allocated to receive either formic acid or PBS solution injected into the ceca in experiment II. Acetic acid or PBS solution injected into the cecum were used for experiment III. After either the acids or the PBS solution were injected into the cecum, two birds from each treatment were placed in a respiratory chamber as a measurement unit for 3 h; each treatment was repeated 3 times. The results indicated that formic acid inoculated into the oesophagi of geese was quickly converted into methane. Compared with the PBS-injected group, methane production increased by 5.02 times in the formic acid injected group (4.32 vs. 0.86 mg/kg BW/d; p<0.05). Acetic acid injected into the ceca did not increase methane production; conversely, it tended to decrease methane production. The present study suggests that formic acid may be converted to methane in the ceca, and that acetic acid may not be a precursor of methane in the ceca of geese.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.12
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• pp.1698-1707
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• 2013

Optimization of the dietary formulation is the most effective way to reduce methane. Nineteen feed ingredients (brans, vegetable proteins, and grains) were evaluated for their potential to generate methane and change methanogen diversity using an in vitro ruminal fermentation technique. Feed formulations categorized into high, medium and low production based on methane production of each ingredient were then subjected to in vitro fermentation to determine the real methane production and their effects on digestibility. Methanogen diversity among low, medium and high-methane producing groups was analyzed by PCR-DGGE. The highest methane production was observed in Korean wheat bran, soybean and perilla meals, and wheat and maize of brans, vegetable protein and cereal groups, respectively. On the other hand, corn bran, cotton seed meal and barley led to the lowest production in the same groups. Nine bacteria and 18 methanogen 16s rDNA PCR-DGGE dominant bands were identified with 83% to 99% and 92% to 100% similarity, respectively. Overall, the results of this study showed that methane emissions from ruminants can be mitigated through proper selection of feed ingredients to be used in the formulation of diets.

• Asian Journal of Atmospheric Environment
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• v.2 no.2
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• pp.116-124
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• 2008

In this study, the Tier 2 method recommended by the Intergovernmental Panel on Climate Change (IPCC) was used to predict the methane generation rate at two landfill sites, designated as Y and C for purposes of this study, in South Korea. Factors such as the average annual waste disposal, methane emissions ($L_0$) and methane gas generation rate constant (k) were estimated by analyses of waste and the historical data for the landfills. The value of k was estimated by field experiments and then the changes in the methane generation rate were predicted through the year 2050, based on the value of k. The Y landfill site, which was in operation until the year 2008, will generate a total of 17, 198.7 tons by the end of 2018, according to our estimations. At the C landfill site, which will not be closed until the end of 2011, the amount of methane gas generated in 2011 will be 3,316 tons and the total amount of gas generated by 2029 will be 61,200 tons. The total production rate of methane gas at the C landfill is higher than that of the Y landfill. This indicates that the capacity of a landfill site affects the production rate of methane gas. However, the interrelation between the generation rate of methane and the value of k is weak. In addition, the generation of methane gas does not cease even when the operations at a landfill site come to a close and the methane gas production rate is at its highest at end of the operating life of a landfill site.

• Journal of Korean Society on Water Environment
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• v.26 no.5
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• pp.810-815
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• 2010

Ultrasonic sludge pre-treatment has been studied to enhance the performance of anaerobic digestion by increasing sludge hydrolysis which is regarded as the rate-limiting-step of anaerobic digestion. In this study, the effect of ultrasonic pre-treatment on sludge hydrolysis (solubilization) and methane production was investigated. Sludge solubilization efficiency increased with ultrasonic energy input. However, it is uneconomical to apply more than 720 kJ/L as the solubilization efficiency per energy input declines afterwards. Volatile fatty acids concentration increased after the ultrasonic sludge hydrolysis. Anaerobic batch digestion showed that methane volume reached 64.7 and 84.5 mL after 18 days of incubation with the control sludge and ultrasonically hydrolyzed sludge, respectively. Methane production potential, maximum methane production rate, and the lag time of modified Gompertz equation were changed from 70 mL, 6.4 mL/day, and 1.2 days to 89 mL, 9.6 mL/day, and 0.5 day, respectively, after the ultrasonic sludge treatment. The results proved that ultrasonic pre-treatment contributed significantly not only for the methane production but also for the reduction of anaerobic digestion time which is critical for the performance of anaerobic sludge digestion.