• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.1
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• pp.57-68
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• 2023

In this study, coffee waste was recycled into nitrogen-doped porous carbon fibers as an active material for high-energy EDLC (Electric Double Layer Capacitors). The coffee waste was mixed with polyvinylpyrrolidone and dissolved into dimethylformamide. The mixture was then electrospun to fabricate coffee waste-derived nanofibers (Bare-CWNF), and carbonization process was followed under a nitrogen atmosphere at 900℃. Similar to Bare-CWNF, the as-synthesized carbonized coffee waste-derived nanofibers (Carbonized-CWNF) maintained its fibrous form while preserving the composition of nitrogen. The electrochemical performance was analyzed for carbonized coffee waste (Carbonized-CW)-, carbonized PAN-derived nanofibers (Carbonized-PNF)-, and Carbonized-CWNF-based electrodes in the operating voltage window of -1.0-0.0V, Among the electrodes, Carbonized-CWNF-based electrodes exhibited the highest specific capacitance of 123.8F g^-1 at 1A g^-1 owing to presence of nitrogen and porous structure. As a result, nitrogen-contained porous carbon fibers synthesized from coffee waste showed excellent electrochemical performance as electrodes for high-energy EDLC. The experimental designed in this study successfully demonstrated the recycling of the coffee waste, one of the plant-based biomass that causes the environmental pollution into high-energy materials, also, attaining the ecofriendliness.

• Journal of the Korea Organic Resources Recycling Association
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• v.12 no.4
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• pp.130-138
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• 2004

Food wastes with different regional origins were mixed with bulking agent such as paper mill sludge or night soil, and aged for 21 days or 28 days. And aged food wastes were fed to the earthworm(tiger worm, Eisenia fetida) for 60 days. There were no significant physico-chemical differences among the food wastes with different regional origins. EC values and NaCl concentrations in food wastes were too high for earthworms to survive. Food wastes mixed with paper mill sludge were vermicomposted more efficiently than food wastes mixed with night soil, but the over-all vermicomposting rates on the food wastes were much lower than that on paper mill sludge because EC values and NaCl concentrations were still high for earthworm to compost the feeds. Earthworm population did not increase its biomass on the food wastes mixed with paper mill sludge or night soil, whereas earthworm population fed with paper mill sludge increased its biomass by 20% for 60 days. It could be concluded that a solution for reducing NaCl concentrations in food waste should be developed to vermicompost food waste.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.10
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• pp.672-678
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• 2014

In this study, variations of fermentative hydrogen production and microbial community were investigated with different nitrogen concentration of food waste. Optimum hydrogen production rate was acquired at 200 mg/L nitrogen concentration of the food waste. Which was eqivalent to 83.43 mL/g dry biomass/hr. However, bio-hydrogen production was inhibitedly reduced at over 600 mg/L of nitrogen concentration whereas proportional relation between hydrogen production and B/A ratio were not observed. Most dominant specie of the microbial community analyzed was Clostridium sp. throughout PCR-DGGE analysis of 16S rDNA. It revealed that most contributing microorganism producing hydrogen were Enterococcus faecium partial, Klebsiella pneumoniae strain ND6, Enterobacter sp. NCCP-231, and Clostridium algidicarnis strain E107 in this experiment.

• Carbon letters
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• v.11 no.3
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• pp.224-234
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• 2010

Four activated carbons were produced by two-stage process as followings; semi-carbonization of indigenous biomass waste, i.e. cotton stalks, followed by chemical activation with KOH under various activation temperatures and chemical ratios of KOH to semi-carbonized cotton stalks (CCS). The surface area, total pore volume and average pore diameter were evaluated by $N_2$-adsorption at 77 K. The surface morphology and oxygen functional groups were determined by SEM and FTIR, respectively. Batch equilibrium and kinetic studies were carried out by using a basic dye, methylene blue as a probe molecule to evaluate the adsorption capacity and mechanism over the produced carbons. The obtained activated carbon (CCS-1K800) exhibited highly microporous structure with high surface area of 950 $m^2/g$, total pore volume of 0.423 $cm^3/g$ and average pore diameter of 17.8 ${\AA}$. The isotherm data fitted well to the Langmuir isotherm with monolayer adsorption capacity of 222 mg/g for CCS-1K800. The kinetic data obtained at different concentrations were analyzed using a pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. The pseudo-second-order model fitted better for kinetic removal of MB dye. The results indicate that such laboratory carbons could be employed as low cost alternative to commercial carbons in wastewater treatment.

• Microbiology and Biotechnology Letters
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• v.22 no.2
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• pp.197-202
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• 1994

Microalga, Spirulina platensis has been cultivated in a pilot scale photo-bioreactor to treat wastewater and to produce high protein feedstocks from swine waste containing medium. 0.31(1/day) of specific growth rate and 0.170 of bioenergeric yield were obtanined from batch cultivation in 30% waster containing medium, compared to 0.71(1/day) and 0.545 from clean culture. An optimal dilution concentration was decided as 20% of working volume, based upon the cell growth and biomass productivity. The removal rate of nitrates in the wastewater was decreased as the adding concentration of wastewater was increased while the decrease of total phosphates was reversed, showing 0.33(1/day) and 0.30(1/day) of rate constants for nitrate removal in 10% addition and for phosphate removal in 30% addition, respectively. The chemical composition and amino acid profile of the biomass were superior to those of commerically available health food product, Spirulina sp.

• Analytical Science and Technology
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• v.31 no.3
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• pp.112-121
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• 2018

The hydrothermal carbonization method has received great attention because of the conversion process from biomass. The reaction produces various products in hydrochar, bio-liquid, and gas. Even though its yield cannot be ignored in amount, it is difficult to find research papers on bio-liquid generated from the hydrothermal carbonization reaction of biomass. In particular, the heterogeneity of feedstock composition may make the characterization of bio-liquid different and difficult. In this study, bio-liquid from the hydrothermal carbonization reaction of food wastes at $230^{\circ}C$ for 4 h was investigated. Among various products, fatty acid methyl esters were analyzed using two different extraction methods: liquid-liquid extraction and column chromatography. Different elutions with various solvents enabled us to categorize the various components. The eluents and fractions obtained from two different extraction methods were analyzed by gas chromatography with a mass spectrometer (GC/MS). The composition of the bio-liquid in each fraction was characterized, and seven fatty acid methyl esters were identified using the library installed in GC/MS device.

• Journal of Microbiology and Biotechnology
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• v.33 no.9
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• pp.1238-1249
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• 2023

In this study, we sought to investigate the production and optimization of biosurfactants by soil fungi isolated from petroleum oil-contaminated soil in Saudi Arabia. Forty-four fungal isolates were isolated from ten petroleum oil-contaminated soil samples. All isolates were identified using the internal transcribed spacer (ITS) region, and biosurfactant screening showed that thirty-nine of the isolates were positive. Aspergillus niger SA1 was the highest biosurfactant producer, demonstrating surface tension, drop collapsing, oil displacement, and an emulsification index (E₂₄) of 35.8 mN/m, 0.55 cm, 6.7 cm, and 70%, respectively. This isolate was therefore selected for biosurfactant optimization using the Fit Group model. The biosurfactant yield was increased 1.22 times higher than in the nonoptimized medium (8.02 g/l) under conditions of pH 6, temperature 35℃, waste frying oil (5.5 g), agitation rate of 200 rpm, and an incubation period of 7 days. Model significance and fitness analysis had an RMSE score of 0.852 and a p-value of 0.0016. The biosurfactant activities were surface tension (35.8 mN/m), drop collapsing (0.7 cm), oil displacement (4.5 cm), and E₂₄ (65.0%). The time course of biosurfactant production was a growth-associated phase. The main outputs of the mathematical model for biomass yield were Yx/s (1.18), and µ_max (0.0306) for biosurfactant yield was Y_p/s (1.87) and Y_p/x (2.51); for waste frying oil consumption the So was 55 g/l, and Ke was 2.56. To verify the model's accuracy, percentage errors between biomass and biosurfactant yields were determined by experimental work and calculated using model equations. The average error of biomass yield was 2.68%, and the average error percentage of biosurfactant yield was 3.39%.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.11
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• pp.80-85
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• 2021

The gasification of coffee leaves, which are a type of biomass waste, was conducted on a pilot of a downdraft fixed gasification system to investigate the gasification characteristics. The experiment was performed using a coffee leaf pellet size and a batch-type gasification system consisting of a gasifier, cooling cyclone, scrubber, and bag filter. It was found that the air-to-fuel ratio was 2.32 Nm³/kg·h and the reaction temperature was 700 ℃-900 ℃. However, the air flow rate changed to 0.45 Nm³/min, which was lower than the initial starting value depending on the temperature change during the gasification process. It was concluded that coffee leaves can be converted from biomass waste into useful synthetic gas as an alternative energy source.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.1
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• pp.37-44
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• 2000

Laboratory experiments were conducted to investigate the performances of anaerobic filters packed with ceramic tube and pall-ring media treating a dairy waste. The media packing volume was 65% of effective volume of anaerobic filter. Organics removals of anaerobic filters were maintained above 80% even at an organics loading rate of $10kgCOD/m^3/d$, and this was comparable to aerobic treatment of organic wastes. Organics removals of the ceramic tube anaerobic filters were always lower than those of the pall-ring anaerobic filters due to intrinsic physical property of ceramic tube, especially lower void space which caused to clogging and entrapment of biogas, substrate transfer limitation, and irregular evolution of biogas leading to loss of solids and biomass. This was clearly observed in higher concentration of TSS in the effluent from the ceramic tube anaerobic filter despite of higher retention capacity of TSS compared with pall-ring media. Vertical distribution of organics and solids in the filters showed above 90% of organics and solids in influent were removed below 20% of reactor height, and 50% of remaining organics and solids were removed though media packing zone. Effluent quality from the anaerobic filter was heavily depended on media itself as well as suspended biomass formed below media. It is therefore concluded that the type of media played an important role in biomass accumulation arid gas-liquid-solid separation efficiency. Type of media did not affect the start-up behaviors of the anaerobic filter, and supernatant from anaerobic digested sludge showed a good performance as a seeding materials.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.10
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• pp.704-710
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• 2014

Biomass is considered an alternative energy which can solve an greenhouse gas problem like $CO_2$ which is a major contributor to global warming. The biomass can be converted to various energy sources through thermochemical conversion. In this study, a continuous gasifier was engineered for a wood biomass gasification. The biomass was used a waste wood. The experiments of $CO_2$ gasification were achieved as the gasification temperature, moisture content and input $CO_2$ concentration. The results showed that the yield of producer gas increased with an increasing the gasification temperature. The amount of the light tar increased due to the decomposition of gravimetric tar by the thermal cracking, and the char was confirmed pore development through the SEM analysis. The CO concentration was increased with an increased input $CO_2$ concentration from Boudouard reaction. Through the parametric screening studies, the hydrogen and carbon monoxide concentration were 32.91% and 48.33% at the optimal conditions of this test rig.