• Journal of the Korea Organic Resources Recycling Association
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• v.30 no.1
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• pp.13-21
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• 2022

Mushroom waste medium refers to the waste biomass generated after mushroom cultivating. And, the burden of treatment on mushroom farmhouse is increasing due to the absence of appropriate treatment method and increase of treatment costs of the mushroom waste medium. In this study, in order to assess the energy value of mushroom waste medium by an anaerobic digestion, methane potential and anaerobic organic matter decomposition characteristics were investigated. The theoretical methane potential(B_th) of mushroom medium(MM) was 0.481 Nm³-CH₄/kg-VS_added, and the B_th of mushroom waste medium(MWM) was 0.451 Nm³-CH₄/kg-VS_added. The biochemical methane potential(B_u-exp) of MWM was increased by 18% from 0.155 for MM to 0.183 Nm³-CH₄/kg-VS_added for MWM. In the reaction kinetics analysis by the Modified Gompertz model, the maximum methane production rate(R_m) was increased from 4.59 for MM to 7.21 mL/day for MWM and the lag growth phase time(λ) was decreased from 2.78 for MM to 1.96 days for MWM. In the reaction kinetics analysis by the parallel first order kinetics model, the easily degradable organic matter(VS_e) content was increased by 5.89% and the persistently degradable organic matter(VS_p) content was 2.03% in MWM, and the non-degradable organic matter(VS_NB) content was decreased by 7.85%. Therefore, it was evaluated that the anaerobic digestion efficiency of MWM was increased. The anaerobic digestion efficiency of MWM was assessed to be more improved than that of MM.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.4
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• pp.13-28
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• 2023

This study assessed the biochemical methane potential (B_u-P) of three grass species-Poa pratensis (PP), Zoysia japonica (ZJ), and Agrostis stolonifera (AS). B_u-P values were determined as 0.330 Nm³/kg-VS_added for PP, 0.297 Nm³/kg-VS_added for ZJ, and 0.261 Nm³/kg-VS_added for AS. Notably, PP exhibited superior suitability for methane production. The investigation also examined the impact of silage storage duration on PP grass clippings, revealing a 19% decline in B_u-P from an initial value of 0.269 Nm³/kg-VS_added on day 0 to 0.217 Nm³/kg-VS_added on day 180. Throughout the storage period, there were significant increases in neutral detergent fiber (NDF), acid detergent fiber (ADF), and crude protein (CP) contents, rising from 67.59%, 39.68%, and 3.02% on day 0 to 77.12%, 54.65%, and 6.24% on day 180, respectively. These findings highlight the influence of storage duration on the anaerobic digestibility of PP grass clippings. To effectively utilize grass clippings as a renewable resource for methane production, further studies considering factors such as initial moisture content, pretreatment methods, and potential effects of residual pesticides are necessary to optimize anaerobic digestion efficiency for herbaceous biomass.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.1
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• pp.35-45
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• 2017

In order to improve the anaerobic digestion efficiency of the sewage sludge, the methane potential of the hydrolysate generated from the hydro-thermal reaction at 170, 180, 190, 200, 210, $220^{\circ}C$ was analyzed and the constitutional characteristics of the organic materials were estimated by dividing organic materials of hydro-thermal hydrolysate into easily biodegradable, decomposition resistant, and non-biodegradable organic materials applying the parallel first order kinetics model. The ultimate methane potential of sewage sludge hydro-thermal hydrolysate increased to 0.39, 0.39, 0.40, 0.44, 0.45, and $0.46Nm^3/kg-VS_{added}$ as hydro-thermal reaction temperature increased from 170, 180, 190, 200, 210, $220^{\circ}C$. It has been shown that the organic matter of sewage sludge is solubilized to increase the content of biodegradable organic material($VS_B$). The easily degradable organic matter($VS_e$) content was highest at hydro-thermal reaction temperature of 200 and $210^{\circ}C$, and optimum hydro-thermal reaction temperature for organic matter solubilization of sewage sludge was in the range of $200{\sim}210^{\circ}C$. In addition, the amount of biodegradable organic material($VS_B$) and easily biodegradable organic matter ($VS_e$) in the hydrolysate of sewage sludge was the highest at hydro-thermal reaction temperature of $200^{\circ}C$.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.2
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• pp.51-58
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• 2016

In the Integrated Two-Phase Anaerobic Digestion (ITPAD) process, acid and methane fermentation take place in one reactor, which has advantages to cope with organic load variation and reduce foot-print required, compensating disadvantages of Conventional Separated Two-Phase Anaerobic Digestion (CSTPAD). In the present work, organic matter degradation efficiency and biogas generation amount and other performance parameters of the ITPAD fed with food waste leachate were analyzed. In addition, feasibility study on the ITPAD method was performed by comparing its digestion efficiency with that of the CSTPAD. Organic matter alteration and biogas generation of the integrated method were examined for approximately 130 days based on the 5ton/day scaled pilot plant. Experiment results revealed that organic matter removal rate was 80% for mean food waste leachate input amount of $4.1m^3/day$. The biogas generation rate was $63.0m^3$ per ton of food waste leachate input, corresponding to the input VS amount of $0.724m^3/kg-VS_{added}$, and methane content of generated biogas was approximately 61.3%. The ITPAD has a comparable or higher organic matter removal efficiency compared to the conventional separated two-phase anaerobic digestion method. Consequently, the ITPAD method has a great need to commercialize a food waste leachate treatment technology against highly concentrated organic waste leachate.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.5
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• pp.341-345
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• 2009

Continuous dry anaerobic digestion of organic solid wastes (30% TS, Total Solids) comprised of food waste and paper was performed under mesophilic condition. During the operation, hydraulic retention time (HRT) was decreased as follows: 150 d, 100 d, 60 d, and 40 d, which corresponded to the solid loading rate of 2.0, 3.0, 5.0, and 7.5 kg TS/$m^3$/d, respectively. Volumetric biogas production rate ($m^3$/$m^3$/d) increased as HRT decreased, and the highest biogas production rate of 3.49${\pm}$0.31 $m^3$/$m^3$/d was achieved at 40 d of HRT. At this HRT, high volatile solids (VS) reduction of 76% was maintained, and methane production yield of 0.25 $m^3$/kg $TS_{added}$ was achieved, indicating 67.4% conversion of organic solid waste to bioenergy. The highest biogas production yield of 0.52 $m^3$/kg $TS_{added}$ was achieved at 100 d of HRT, but it did not change much with respect to HRT. For the ease feed pumping, some amount of digester sludge was recycled and mixed with fresh feed to decrease the solid content. Recirculation volume of 5Q was found to be the optimal in this experimental condition. Specific methanogenic activity (SMA) of microorganisms at mesophilic-dry condition was 2.66, 1.94, and 1.20 mL $CH_4$/g VS/d using acetate, butyrate, and propionate as a substrate, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.10
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• pp.730-736
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• 2013

This study was conducted to examine the effects of the salt concentration in seafood wastewater on the high-rate anaerobic digestion process. In the general high-rate anaerobic process test, the TCODcr removal efficiency at 6 hr or more HRT was 81.1~0.7%, and the optimal HRT for seafood wastewater process was found to be 6 hr or more. The methane content in the biogas was 70.1~76.8% during the operation, and was hardly affected by the change in the influent load. The results of the anaerobic digestion efficiency according to the salt concentration showed that the removal efficiency of TCODcr was 83.4~89.2% below a $4,000mgCl^-/L$ salt concentration, and mid-70% at a $5,000mgCl^-/L$ salt concentration. Therefore, the salt concentration had to be kept below $4,000mgCl^-/L$ to ensure stable treatment efficiency. Below a $3,000mgCl^-/L$ salt concentration, the methane generation was 0.2999~0.346$m^3CH_4/kgCODrem.$, which was similar to the theoretical methane gas generation in STP condition ($0.35m^3CH_4/gTCODrem.$). The methane content in the biogas was 64.7~73.3% below a $3,000mgCl^-/L$ salt concentration, but decreased with an increase in the salt concentration, to 50.1~56.9% at a $4,000mgCl^-/L$ concentration.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.125-131
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• 2024

In this study, synthesized Ni/Ce_xZr_1-xO₂ catalysts were coated on the surface of honeycomb metalic monoliths to investigate catalytic activity in steam reforming of methane reactions. Supports with varying Ce/Zr ratios were synthesized to observe their behavior in the reforming reaction, and catalysts with Ni contents ranging from 5 wt% to 20 wt% were prepared to analyze the effect of Ni loading contents on catalytic activity. The catalysts were characterized by XRD, BET, TPR, and SEM. The TPR analysis indicated the formation of Ni-Ce-Zr oxide with a strong interaction between the active metal Ni and CeO₂-ZrO₂ support. The 15 wt% Ni/Ce_0.80Zr_0.20O₂ catalyst exhibited the highest activity and stability in the steam reforming of methane reaction. Catalysts with enhanced activity and stability were synthesized by manufacturing composite materials using excellent oxygen storage and donor properties of CeO₂ and the thermal properties of ZrO₂.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.367-370
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• 2003

This study was carried out to investigate the possibility for reuse of solid organic wastes such as saccharified newspapers and boxes by two-phase anaerobic fermentation system. When 15g of newspaper and box wastes were digested for 24 days by batch fermentation, tCOD removal rate were found to be 60.9 and 62.4%, respectively. During this period, the amounts of biogas produced were 6.95 and 6.43L. The removal efficiencies of total solid were 34.8 and 33.4%, and those of volatile solid were 40.0 and 39.2%, respectively. That pH was around 7.5 after 20-days operation means methane fermentation is well advanced. In case of semicontinuous reaction, tCOD removal efficiencies of newspaper and box wastes were 64.7 and 65.0%, respectively for 14-days operation. It has been shown that each of the average biogas amounts produced after 25 days operation (stabilization stage for methane fermentation) was 0.31 and 0.30L/g dry wt./day, respectively, and each methane contents was 57.3 and 56.2%, respectively. After the reaction continued for 25 days, pHs in the anaerobic acidogenic and methanogenic fermenters were shown to be 5.0 and 7.5, respectively.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.4
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• pp.74-85
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• 2015

Recently, the number of anaerobic digestion facility for livestock manure is on the rise in Korea. All of the livestock manure anaerobic digestion facilities in operation use pig manure slurry as a substrate for anaerobic digestion. Generally, pig manure slurry is composed of 97% water and 3% solids. The particulate matter, such as corn in the form of particles that is undigested by pig is contained in the pig manure slurry. Particulate matter is a factor reducing the effectiveness of biogas production in the anaerobic digestion process. In this study, mechanical grinding treatment was applied to analyze the effect of methane production from pig manure slurry by reducing the particle size of the slurry. On the other hand, the effect of the solid concentration levels on methane production and methane content of the biogas was analyzed. The fine particle concentration in the pig manure slurry was increased by the mechanical grinding treatment. And methane production and methane content of the biogas were higher in grinded pig manure slurry than untreated raw slurry.

• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.103-109
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• 2010

Anaerobic digestion has been widely used for the treatment of sludge, which is generated from the municipal and industrial wastewater treatment, for its volume reduction and methane production. Many researches on sludge pre-treatment have been carried out in order to enhance the performance of anaerobic digestion by increasing the hydrolysis of sludge which is the rate limiting step of anaerobic digestion. In this study, the effect of pre-treatment on sludge hydrolysis(solubilization), methane production and sludge reduction by anaerobic digestion after thermal, ultrasonic, and thermal-alkali sludge treatment were compared. Thermal-alkali treatment showed 67 and 70% solubilization with municipal and industrial wastewater sludge, respectively, while ultrasonic treatment and thermal treatment gave similar solubilization efficiency of 40% or more. Methane content of the anaerobic digestion gas reached 45~70% and pretreated sludge gave higher methane content than the control sludge. Methane production of thermal, ultrasonic, and thermal-alkali pre-treatment gave 2.6, 2.7, 3.5 times of municipal control sludge and 3.5, 4.1, 4.2 times of industrial control sludge, respectively. Sludge reduction of pre-treated sludge after anaerobic digestion gave 5~19% point higher than that of control sludge, and thermal-alkali treatment showed higher reduction efficiency than thermal and ultrasonic treatment. The results proved that pre-treatment contributed significantly not only for the methane production but also for the cost reduction of sludge treatment and disposal, and thermal-alkali treatment gave the best performance for the sludge treatment.