• Journal of Environmental Science International
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• v.2 no.4
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• pp.311-316
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• 1993

Methane production from grain dust was studied using a 3 L laboratory-scale anaerobic plug flow digester. The digester was operated at; temperature of 35, 45, and 55$^{\circ}C$; hydraulic retention time(HRT) of 6 and 12 days; and influent concentration($S_o$) of 7.8 and 9.0 % total solids(%TS). With ten different operation conditions, this study showed the significant effects of temperature, hydraulic retention time, and influent concentration on methane production. The highest methane-production rate achieved was 1.903 (L methane) /(L digester)(day) at 55$^{\circ}C$, 6 days HRT, and $S_0$ of 7.8 %TS. A total of 3.767 L of biogas per day with a methane content of 50.57 % was obtained from this condition. The ultimate methane yield($B_0$) was found to be a function of temperature and influent concentration, and was described as : $B_0$ = 0.02907T-0.1263-0.00297(T-10)(%TS), where TS is the total solids in the liquid effluent, and T is temperature($^{\circ}C$). Our results showed that thermophilic condition is better than mesophilic for grain dust stabilization in an anaerobic plug flow digester.

• Journal of Environmental Science International
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• v.32 no.1
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• pp.47-55
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• 2023

This study evaluated the biochemical methane potential (BMP) of primary sludge, secondary sludge, and food waste in batch anaerobic mono-digestion tests, and investigated the effects of mixture ratio of those organic wastes on methane yield and production rate in batch anaerobic co-digestion tests, that were designed based on a simplex mixture design method. The BMP of primary sludge, secondary sludge and food waste were determined as 234.2, 172.7, and 379.1 mL CH₄/g COD, respectively. The relationships between the mixing ratio of those organic wastes with methane yield and methane production rate were successfully expressed in special cubic models. Both methane yield and methane production rate were estimated as higher when the mixture ratio of food waste was higher. At a mixing ratio of 0.5 and 0.5 for primary sludge and food waste, the methane yield of 297.9 mL CH₄/g COD was expected; this was 19.4% higher than that obtained at a mixing ratio of 0.3333, 0.3333 and 0.3333 for primary sludge, secondary sludge, and food waste (249.5 mL CH₄/g COD). These findings could be useful when designing field-scale anaerobic digersters for mono- and co-digestion of sewage sludges and food waste.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.6
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• pp.893-906
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• 2011

The effect of ultrasound pretreatment on sludge degragability was investigated at different condotions: ultrasonic frequency(28, 40, 50kHz), intensity(10, 25, 50W), sonication time(10, 20, 30, 60min). Total suspended solid(TSS) and soluble chemical oxygen demand(SCOD) concentration were measured for the evaluation of pretreatment efficiency. The pretreated sludge was used as the feedstock for anaerobic digestion process. Biogas production and volatile suspended solid(VSS) removal were determined for evaluating the process performance. 1. TSS concentration of the sludge decreased at a constant rate as sonication operation was applied. The degradation rate of TSS increased when ultrasound frequency was decreased from 50kHz to 28kHz and intensity was increased from 10W to 50W. Efficiency of TSS degradation per input energy increased as ultrasonic frequency and intensity were decreased. At the frequency of 28 and 40kHz, SCOD concentration rapidly increased during the initial 30min of sonication time, and then it gradually increased. At 50kHz, SCOD concentration constantly increased for 60min of the sonication time. The SCOD production rate increased with increasing intensity under all ultrasound frequencies. 2. The optimum condition of ultrasound treatment was 28kHz, 50W and 60min for maximizing the biogas production, methane fraction, VSS removal. The highest values in biogas production, methane fraction in biogas, VSS removal were 370ml, 70%, 2.45g, respectively. Methane production rate per input energy increased at ultrasonic frequency and intensity decreased. 3. When raw sludge was pretreated at the condition of ultrasonic frequency of 28 and 40kHz in series, sequential-frequency sonication, intensity of 50W and 60min, biogas production, methane fraction, VSS removal were about the same that of 28kHz single-frequency sonication. When sequential-frequency sonication of 28 and 50kHz was applied in series, biogas production, methane fraction, VSS removal were 356 ~ 423ml, 69 ~ 71%, 2.41 ~ 2.78g, respectively. The pretreatment efficiency of 28-50kHz sequential-frequency sonication which sonication time of 28kHz and 50kHz was 40min and 20min was higher than that of 28kHz single-frequency sonication.

• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.583-588
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• 2004

This research examined the treatment efficiency and methane production rate in treating slurry-type swine waste using UASB (upflow anaerobic sludge blanket) reactor. The UASB reactor was operated at an organics volumetric loading rate (VLR) of $2.6-15.7kgCOD/m^3/day$. A stepwise increase of the VLR resulted in a temporary deterioration in the COD removal rate in UASB reactor but recovered quickly. The COD removal rate were 65-70% for VLR up to $5 kgCOD/m^3/day$. When organics VLR was $10kgCOD/m^3/day$, the COD removal rate decreased sharply and there was loss of 17.537g of the seeding biomass due to sludge washout. This result indicated that the UASB system cannot be adapted to more than $10kgCOD/m^3/day$ of VLR. As the organic load increased from 2.6 to $15.7kgCOD/m^3/d$, the biogas production rate varied from 3.2 to 10.8 L/d and the methane conversion rate of the organic matter varied from 0.30 to $0.23m^3CH_4/kg\;COD_{removed}$. The methane content showed the range of 70.1-81.5% during the experimental period. The volatile solids (VS) removal efficiency was similar at the low VLR (< $5 kgCOD/m^3/day$), but it decreased sharply at the high VLR (> $5 kgCOD/m^3/day$). The VS reduction rate was, moreover, large those of COD. The result shows that hydraulic retention time above 2 days is essential in case of treating wastewater containing 1% of solids.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.3
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• pp.75-82
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• 2016

Objective of this experiment was to predict the potential methane production with crop residues at different loading rates. Anaerobic digestion of barley and rapeseed straw substrates for biogas production was performed in Duran bottles at various biomass loading rates with crop residues. Through kinetic model of surface methodology, the methane production was fitted to a Gompertz equation. For the biogas production at mesophilic digestion with crop residues, it was observed that maximum yield was 37.2 and 28.0 mL/g at 6.8 and 7.5 days after digestion with 1% biomass loading rates of barley and rapeseed straws, respectively. For the methane content of mesophilic digestion, there were highest at 61.7% after 5.5 days and 75.0% after 3.4 days of digestion with barley and rapeseed straw on both 5% biomass loading rates, respectively. The maximum methane production potentials were 159.59 mL/g for 1% barley straw and 156.62 mL/g for 3% rapeseed straw at mesophilic digestion. Overall, it would be strongly recommended that biomass loading rate was an optimum rate at mesophilic digestion for using 1% barley and 3% rapeseed straws for feed stocks.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.3
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• pp.154-159
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• 2006

It is essential to understand the decomposition characteristics for developing the optimum anaerobic digestion system of organic wastes. In this study, BMP (Biochemical Methane Potential) test using serum bottle was conducted to evaluate the anaerobic degradability of fish offal. 3 different groups of fish offal including waste from mackerel and hairtail handling except viscera and fish viscera were chosen for the substrates. Grinded fish offal was transferred anaerobically to serum bottle in amounts of 50 ml, 100 ml and 150 ml, respectively. BMP test was carried out in triplicate. Cumulative methane production and methane production rate depending on incubation time were evaluated. These results varied depending on substrate characteristics. The average values of ultimate methane yield ranged between $420ml{\cdot}CH_4/g{\cdot}VS$ and $490ml{\cdot}CH_4/g{\cdot}VS$, and the methane production and degradation rate of viscera were higher than those of other parts of fish offal. According to the analysis of elemental composition, average C/N ratio of fish offal used in this study was 5.2. Theoretical ultimate methane yield calculated from elemental composition was $522ml{\cdot}CH_4/g{\cdot}VS$. Biodegradability was calculated as 0.847.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.3
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• pp.11-22
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• 2014

The buffer capacity of food waste lowers during the collecting and transportation period. Food waste usually shows deficiency of micro nutrients especially molybdenum(Mo) and cobalt(Co). Therefore, food waste can be considered as a good mixture of livestock waste to enhance methane production. The objective of this study was to investigate the correlation between properties of substrates (local food waste and livestock manure) and methane yields for successive anaerobic fermentation process and its stable management. Food wastes were taken at an intermediate storage or treatment system provided by eight local authorities (Gangnam, Gangdong, Gwanak, Guro, Dongjak, Songpa, Yeongdeungpo, and Younsan) in Seoul. The solid content and potential methane yield of food wastes were average of 16% and $446.6STP-m{\ell}/g-VS$ (range from 334.8 to $567.5STP-m{\ell}/g-VS$) respectively. As for the beef cattle manure, the solid content and potential methane yield had an average of 26% and $280.6STP-m{\ell}/g-VS$ respectively. Potential methane yield had a positive correlation with fat content, and hydrogen content and a negative correlation with carbohydrate content ($r^2&gt;0.8$). Therefore, the potential methane yield can be predicted based on the substrate characterization results with reasonable accuracy. Further research may be needed to investigate the relation of the properties of the mixture substrate and methane production rate. The mixtures may include food waste, livestock waste, and bulking agents (saw dust, rice hull, or agricultural byproducts etc.) to determine best combination of these substrates for maximum methane production rate.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.1
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• pp.1-7
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• 2022

Interest in hydrogen productions that do not emit carbon dioxide and can produce hydrogen at a low price is increasing. Reforming and electrolysis are widely used, but they have limitations, such as carbon dioxide problems and costs. The methane can be decomposed as hydrogen and solid carbon without carbon dioxide emission at high temperatures. In this research, the methane pyrolysis experiment was conducted at 1,200℃ and 1,400℃ in a ceramic tube. The composition of the produced gas was measured by gas chromatography before carbon blocked the tube. The methane conversion rate and hydrogen selectivity were calculated based on the results. The hydrogen selectivity was derived as 60% and 55% at the highest point at 1,200℃ and 1,400℃, respectively. The produced solid carbon was expected to be carbon black and was analyzed using scanning electron microscope.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.328-334
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• 2000

The hybrid catalytic(catalytic+thermal) combustor of a lean methane-air mixture on platinum catalyst was investigated numerically using a 2-D boundary layer model with detailed homogeneous and heterogeneous chemistries. For the more accurate calculations, the actual surface site density of monolith coated with platinum was decided by the comparison with experimental data. It was found that the homogeneous reactions in the monolith had little effect on the change of temperature profile, methane conversion rate and light off location. However, the radicals such as OH and CO were produced rapidly at exit by homogeneous reactions. Thus the homogeneous reactions were important to predict the productions of CO and NOx exactly. In thermal combustor, the production of $N_2O$ was more dominant than that of NO due to the relative important of the reaction $N_2+O(+M){\to}N_2O(+M)$. Finally the production of CO and NOx by amount of methane addition were studied.

• Journal of Animal Environmental Science
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• v.19 no.2
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• pp.191-196
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• 2013

In this study, the mixture ratio included 20% (GLY 20), 40% (GLY 40), and 60% (GLY 60) based on VS with the control group (GLY 0) with no crude glycerin added. Maintaining stable pH, GLY 20 and GLY 0 showed the highest total output of biogas (1.24 L/L/d) and methane(0.78 L/L/d) as its volatile solids reduction rate was 53.56%. In case of GLY 40 and GLY 60, their pH was rapidly reduced after seven days of the study, so that their anaerobic digestion was all stopped.In the results of the study, it is desirable to add crude glycerin less than 20%, and it would be necessary to have the future researches on more detailed organic loading rate of each ratio, and analysis on economic feasibility.