김기영 Gi-yeong Kim , 김연수 Youn-su Kim , 이채영 Chae-young Lee

DOI:10.9786/kswm.2020.37.6.375

Abstract

This study exploits a biodegradability analysis method to evaluate the methane produced by the anaerobic digestion of food waste. Four different types of food waste were considered as substrates. The results revealed that the contents of lipids and carbohydrates varied considerably with the substrate type. Prior to anaerobic digestion, two types of food waste, named S1 and S2, exhibited high carbohydrate content (56.9% and 66.3%) but low lipid content (13.5% and 9.4%). By comparison, the other two types of food waste, named S3 and S4, had high levels of lipids (36.1% and 35.9%) but low carbohydrates content (29.4% and 25.4%). Protein levels were similar (32.1 ~ 39.7%) across all in the four types of food waste. Batch anaerobic digestion tests elucidated that S3, which had high lipid content, yielded the highest ultimate methane production (UMY) (490.8 mL CH₄/g VS) that was 1.2 times greater than the UMY associated with S2 (413.1 mL CH₄/g VS), which had higher carbohydrate content. Further biodegradability analyses established that the composition of organic matter was more advantageous than elemental composition in evaluating the amount of methane generated from the anaerobic degradation of food waste. The Dual-Gompertz equation is advantageous in calculating the maximum methane generated from the amount of food waste because evaluates the maximum methane generation rate and the maximum methane generation rate by uniquely classifying the decompositions of carbohydrate, protein, and fat decomposition. Moreover, the Dual-Gompertz equation is anticipated more effectively predict cumulative methane generation based on the injected substrate versus the modified Gompertz equation.

Key Words

Anaerobic digestion, Food waste, Theoretical methane production, Biodegradability analysis method

윤주형 Joohyeong Yoon , 김상범 Sangbum Kim , 김종수 Jongsu Kim , 구본진 Bonjin Koo , 박진원 Jinwon Park , 류태우 Taeu Yu , 김범종 Beomjong Kim

DOI:10.9786/kswm.2020.37.6.383

Abstract

The thermal transformation, including incineration and pyrolysis, of combustible waste is an effective technique to reduce the volume of waste, and has been widely used to treat waste with low levels of radioactivity. These processes generate ash composed of inorganic compounds such as solid oxides (SiO₂, Al₂O₃, TiO₂, Fe₂O₃), alkali metals (Na, K, Mg, Ca, Cs), and nonmetallic compounds (S, P, Se). For combustible waste with low levels of radioactivity, it is critical to limit the emission of Cesium(Cs), which is radioactive, into the environment. The present study develops new understanding of the evaporation behaviors of Cs during thermal transformation. Instead of using Cs, which is hazardous, this study investigates S and Se because these elements exhibit evaporation temperatures and pressures that are similar to Cs near the pyrolysis temperature of 400℃. Thermogravimetric analysis (TGA) enabled the quantification of the evaporation rates of S and Se based on their molecular weights and temperatures. The present study demonstrates the accurate predictions of the evaporation rates of S and Se based on molecular weight and evaporation pressure at specific locations in the reactor during thermal transformation, as long as the temperature is known.

Key Words

Evaporation rate, TGA, DTG analysis, Molecular weight, Vapor pressure, Behavior

김용준 Yong-jun Kim , 김교근 Kyeo-keun Kim

DOI:10.9786/kswm.2020.37.6.390

Abstract

This study seeks to establish the appropriateness of recycling for waste that includes catalysts and bauxite-treated residue. Samples of these wastes were subjected to chemical composition, elution, and contents analyses as well as experiments to identify hazardous properties. Waste that included catalysts had concentrations of Hg that exceeded the regulated limits stated of the Waste Management Act in Korea. Moreover, analyses revealed that catalyst waste had oil contents of 3.7% and thus was flammable. Elemental analyses of samples of bauxite-treated residue revealed concentrations of Cd, Pb, Cu, As, and Hg that met the criteria for area 1 of soil contamination. However, pH of the eluate was 10.1, which is relatively high, and so was judged to be corrosive. These results necessitated that bauxite-treated residue with high Na, Mg, and Al contents be assayed for reactivity with water. If metal content exceeds 5% in bauxite-treated residues, then our study suggests that the waste be assessed for flammability and spontaneous combustion.

Key Words

Environmental hazardous impact, Hazardous properties, Recycling possibility, Waste resources

Ziyao Li , Sangmok Kang

DOI:10.9786/kswm.2020.37.6.401

Abstract

This article analyzes the technical and environmental efficiencies of the MSW incineration industry across 16 cities and provinces in South Korea. The empirical results show significant variations in environmental efficiency, which range from 0.275 to 0.989 with a mean value of 0.912. The Gyeonggi-do region is the most environmentally efficient, while Busan is the least efficient. Moreover, some cities, such as Busan and Daegu, exhibit high technical efficiencies yet have dramatically low environmental efficiencies. Similarly, Seoul and Gwangju perform excellently in terms of environmental efficiency but have the lowest technical efficiencies. The output elasticity was calculated for each input, and the average output elasticity for CO₂ is 0.090. Finally, the scale elasticity in the waste incineration industry was lower than 1.

Key Words

Environmental efficiency, Technical efficiency, MSW incineration, Stochastic frontier production function

한지현 Ji-hyun Han , 서형석 Hyoung-suk Seo , 정진도 Jin-do Chung

DOI:10.9786/kswm.2020.37.6.411

Abstract

By-products such as waste and sludge that are generated from food processing can sometimes be used as fertilizers or feed, but a majority is treated as waste, which makes it challenging to recycle resources. In this study, food waste materials were interrogated for by-products that had antioxidant activities. Waste samples included polyphenols, DPPH, flavonoids, ABTS+ radical, and FRAP. Results showed that the total polyphenols had a high content of Aronia Marc extract (27.58 μg/g) in the ethanol extract and Rice bran (21.29 μg/g) in the water extract. DPPH Radical Eradication was 94.71% in the ethanol extract and 94.71% in the water extract, with the best antioxidant effect observed for Punica granatum. The total flavonoid contents included Isatidis folium (9.69 μg/g) in the ethanol extract and Citrus sinensis Marc (9.88 μg/g) in the water extract. Wheat bran from the ethanol extract at both 100 μg/mL and 500 μg/mL neutralized 99.70% of ABTS+ radical function, while Rice husk at 1,000 μg/mL neutralized 99.27% of ABTS+ radical function. The water extract of 1,000 μg/mL, 500 μg/mL, and 100 μg/mL contained 100% of red ginseng. High FRAP reducing capabilities were observed for Wheat bran at 100 μg/mL of ethanol extract (304.03 abs), red ginseng at 500 μg/mL (590.52 abs) or 1,000 ug/mL (979.24 abs) in water extract. Moreover, the FRAP reducing capabilities of Red ginseng marc at 100 μg/ mL, 500 μg/mL and 1,000 μg/mL of water extract were 342.32 abs, 586.93 abs, and 961.98 abs. As a by-product that suppresses oxidation caused by radicals, it is believed that vegetable waste that can use antioxidant materials and recycle resources can be used as a friendly preservative.

Key Words

Total polyphenol, DPPH radical, Total flavonoid, ABTS+ radical, FRAP

김완수 Wan Su Kim , 이경원 Kyung Won Lee , 동종인 Jong In Dong

DOI:10.9786/kswm.2020.37.6.419

Abstract

Mercury emissions are an important health concern, which led to the international convention on mercury. South Korea strengthened its air pollutant emission standards to stringent levels (0.04 to 0.1 mg/m³). These strongstandards make it important to properly manage mercury emissions from major sources, such as cremation facilities. This study evaluates the mercury-removing performance of injecting CuCl₂ into the activated carbon and zeolite at cremation facilities. The CuCl₂-doped activated carbon materials reduced mercury emissions with 100% efficiency at temperatures below 200˚C, while the zeolite material reduced mercury emissions at efficiencies of 87% to 100% at the tested temperature. When inlet gases included NOx, NH₃, CO, and O₂, the activated carbon showed mercury removal efficiencies of 97.5% while the zeolite showed sufficient elimination efficiencies at 200˚C. Further analyses demonstrated that the performance of the activated carbon material was insensitive to moisture, while the zeolite material had a reduced efficiency of mercury removal following exposure to water. This study found that zeolite catalysts are more effective than A/C catalysts to remove mercury in cremation furnace facilities.

Key Words

Crematorium, Mercury compounds, De-NOx, Elemental mercury, Mercury removal

유내녕 Naining Liu , 김산 San Kim , 정진도 Jin-do Chung

DOI:10.9786/kswm.2020.37.6.429

Abstract

This work determined the optimal conditions for the gasification of cow manure solid fuel using the numerical analysis method. The efficiency of the production of CO and H₂ gases were analyzed using the generaed gas. Among many process variables involved in the gasification reaction, the Equivalence ratio (ER), the ratio of steam to feedstock (S/F ratio), and the temperature of the air that was sent into the gasification reactor were considered as process variables in the numerical analysis. The results of the numerical analysis presented that the highest efficiency was achieved when the ER was 0.2 while gasifying the cow manure in solid state. Further, it was observed that when a lot of air was injected, the syngas was reduced due to the active combustion reaction inside the gasification reactor. Furthermore, the S/F ratio was 0.2 higher than that reported in the literature. It was also found that the gasification reaction was most active when the temperature of the air was 500°C and the efficiency of the generated gas was the highest.

Key Words

Cow manure, Gasification, Plasma, Syngas, Numerical simulation

김훈제 Hoon Jae Kim , 동종인 Jong In Dong

DOI:10.9786/kswm.2020.37.6.435

Abstract

The foul odors from the sewage sludge treatment facilities have been issues. In order to solve the foul odor issuesfrom the sewage sludge treatment facilities, drying of the sewage method was adopted. As of 2016, 76 out of 100 sewage sludge treatment facilities have adopted the drying facilities. In this study, the characteristics and effects of the odors that are generated while drying the sewage sludge were investigated. From the results, it was found that the methyl mercaptan and organic acids contributed significantly to the odor emission. However, it was observed that the organic acids and the aldehydes were high in the final air pollution control equipment facility such as the wet scrubbers. The wet scrubbers are capable of removing organic acids effectively. In addition, it was found that the carbon dioxide that was discharged due to the direct drying method restricted the use of NaOH, which implies that the organic acids were not removed completely. Hence, a combustion method or a microbial deodorization method is suggested in this study. From the results of these methods, it was observed that they removed the organic acids and aldehydes effectively and also reduced the environmental impact that was caused due to the emission of the malodorous substances. Therefore, the combustion method and the microbial deodorization method are suggested over the direct drying method in order to control the emission of the foul odor from the sewage sludge treatment facilities and to reduce the environmental impact caused by the emission of malodorous substances.

Key Words

Sewage sludge, Odor substance, Sludge drying, Odor characteristics