김란희 Ran-hui Kim , 이남훈 Nam-hoon Lee , 이영민 Young-min Lee , 박진규 Jin-kyu Park

DOI:10.9786/kswm.2023.40.1.1

Abstract

Although the 2006 IPCC guidelines provided the first-order decay (FOD) model to estimate the amount of greenhouse gas emissions from waste landfill, the default values of emission factors applied to the FOD model do not reflect individual landfills’ characteristics. Therefore, to examine the model’s limitations, this study compared actual measurement results with those of the FOD model for the Sudokwon landfill in Korea. In addition, cases from the United States have been analyzed to consider improvements in estimating greenhouse gas emissions at municipal solid waste (MSW) landfill sites in Korea. The comparison reveals that the model results were overestimated compared to on-site measurement results. To overcome the limitations of the FOD model, the United States has calculated landfill gas emissions by installing landfill gas recovery systems at MSW landfills and applying a capture efficiency of 75% based on the measured landfill gas recovery data. By applying this calculation method to the Sudokwon landfill, the estimation results for landfill gas emissions based on landfill gas recovery data were similar to those of on-site measurements. Therefore, based on the measured landfill gas recovery data, MSW landfills with landfill gas recovery systems in Korea should estimate landfill gas generation by applying the capture efficiency. For landfills without landfill gas recovery systems, the greenhouse gas emissions of MSW landfills can be estimated using the FOD model. Such improvement measures are expected to improve the accuracy and reliability of greenhouse gas emission measurements at Korean MSW landfills rather than only applying the FOD model.

Key Words

Municipal solid waste, Landfill, Methane emission, FOD model

최성원 Sung-won Choi , 이재영 Jai-young Lee

DOI:10.9786/kswm.2023.40.1.12

Abstract

An accurate forecasting of waste generation is important to establish an efficient waste management. Although the patterns of waste generation are changing due to the COVID-19 pandemic, which started in 2020, there has been no accurate analysis and evaluation. Therefore, this study aims to assess the effects of COVID-19 on household waste generation using machine learning-based neural networks (ANN, LSTM, RNN, and GRU). This study partitioned data into training data (January 2017 - June 2021) and verification data (July 2021 - May 2022) and predicted future waste generation for June 2022 - December 2028. The results showed excellent prediction performance except for high-volatility recyclable waste. Forecasting based on household waste not by type can guarantee predictive performance. In addition, the impact of COVID-19 on household waste generation was a 4.65% increase in garbage waste, a 9.4% increase in food waste, and a 15.53% decrease in recyclable waste.

Key Words

Household waste generation, Forecasting model, Machine learning, Neural Network

송현진 Hyeon-jin Song , 서병돌 Byong-dol Seo , 최우석 Woo-suk Choi , 김동필 Dong-pil Kim , 송명신 Myong-shin Song

DOI:10.9786/kswm.2023.40.1.21

Abstract

Low-temperature calcined cement is a required solution in the cement industry for reducing energy requirements and CO₂ emissions. 12CaO·7Al₂O₃ (hereinafter C₁₂A₇) is a calcium aluminate-based mineral that has properties of rapid hardening, expansion, and ultra-high strength. C₁₂A₇ is mainly produced by the high-temperature melting method, but applying the low-temperature synthesis method (the hydrate sintering method) of C₃A can enable its low-temperature production without any melting process. In this study, C₁₂A₇ was synthesized using waste limestone and waste alumina that was decarboxylated at 900℃ for one hour and then calcined at 1,200℃ for one hour (this process was repeated twice) to study the hydration properties of the synthesized C₁₂A₇. The synthesis yield of the synthesized C₁₂A₇ was ≥70% and the setting time for the synthesized C₁₂A₇ hydrates finished within one minute but the setting time of the synthesized C₁₂A₇ substituted for 50% gypsum was 158 minutes. The compressive strength of the synthesized C₁₂A₇ substituted for 20% gypsum was 8.2 MPa.

Key Words

Waste lime, Waste alumina, Calcium aluminate compounds, C_12A7

이웅걸 Woong-geol Lee , 한래봉 Lae-bong Han , 조성현 Sung-hyun Cho , 이평수 Pyeong-su Lee , 송명신 Myong-shin Song

DOI:10.9786/kswm.2023.40.1.29

Abstract

Treating hydrogen sulfide in landfills generates a large amount of bio-sulfur. Bio-sulfur is mainly used in agriculture because of its small particle size and excellent hydrophilicity. However, the actual amount used is very small and it is piled up in a landfill. Therefore, as a basic study for expanding the utilization of bio-sulfur, this study examines the effect of dried bio-sulfur on the physical properties and hydration reaction of ordinary Portland cement. The hydrate of cement with bio-sulfur at the start of aging was the same as that of plain cement, and sulfur was additionally confirmed. At curing age of 28 days, magnesium sulfate hydrate and kuzelite were also confirmed. As the amount of bio-sulfur added increased, the setting time decreased while the hydration heat tended to decrease. When cured in water, the compressive strength of the mortar with bio-sulfur was reduced compared to that of plain cement. For dry curing, the compressive strength was increased at the initial curing age and remained the same as plain cement at 28 days.

Key Words

Bio-sulfur, Sulfur, Curing condition, Cement hydration

윤석표 Seok-pyo Yoon , 권선우 Seon Woo Kwon , Chenghao Zhu , 김태희 Taehee Kim , 오승준 Seung Jun Oh

DOI:10.9786/kswm.2023.40.1.37

Abstract

In this study, to obtain basic data for the proper treatment of super absorbent polymer ice packs, we conducted an experiment on the evaporative rate of ice packs at different temperatures, thermogravimetric analysis (TGA), qualitative analysis using FTIR, and calorific analysis of dried ice pack contents. The weight ratio of the ice pack component is 1.4% vinyl cover, 0.5% polymer, and 98.1% water. It was calculated that an approximate calorific value of 422.5 kcal/kg is required to evaporate the moisture in the ice pack due to the calorific value of the vinyl cover and polymer. Considering annual amount of waste incineration and disposal of ice packs of a small and medium-sized city in South Korea, the loss of heat due to water evaporation during incineration is only 0.0101% of the total amount of incineration waste, so it would be better to end concerns about microplastics by incinerating at a high temperature.

Key Words

Super absorbent polymer, Ice pack, Waste treatment, TG analysis, FTIR

김재용 Jae Yong Kim , 한신철 Sin Cheol Han

DOI:10.9786/kswm.2023.40.1.44

Abstract

Recently, various studies have been actively conducted for the protection of indigenous freshwater fish species and reduction of ecological disturbances that caused by foreign species. The Ministry of Environment has designated and managing foreign species such as Micropterus salmoides (Largemouth bass), Lepomis macrochirus (Blue gill) and Salmo trutta (Brown trout) as species that disrupt the ecosystem. In particular, the Micropterus salmoides, the top-rated predator without natural enemies which is a carnivorous fish, spreads quickly through our water system. This predaceous and fish net-eluding major risk factor for the ecosystem is continuously extending its habitat nationwide by predating on smaller indigenous fishes. Controlling the population of largemouth bass is inevitable to protect our native fishes and maintain the balance of the freshwater ecosystem. The largemouth bass is a great source of protein and minerals. If the repulsion against foreign, invasive, ecosystem-disturbing fish gets in the way of direct consumption, we should find indirect way to solve this problem by making the fish as a part of preferring food such as fruits and vegetables. In this study, the high-grade amino acids and other nutrients extracted from largemouth bass, an invasive species that disturbed the ecosystem, applied in organic and general agriculture to find out the effectiveness on the growth of crops and plants was evaluated. Furthermore we try to introduce the educational facility for specializing in freshwater ecological environment improvement.

Key Words

Largrmouth bass, Liquid fertilizer, Amino acid, Plant growth, Educational facility

박지형 Ji-hyoung Park , 이한솔 Han-sol Lee , 황용우 Yong-woo Hwang , 김영춘 Young-chun Kim

DOI:10.9786/kswm.2023.40.1.56

Abstract

The present study aims to assess the environmental impacts of 1EA diesel particulate filter (DPF) manufacturing and particulate matter reduction using the life cycle assessment (LCA) analysis. To achieve this objective, the pollutant amounts emitted from the manufacturing process of DPFs were compared with those reduced by attaching to the produced DPFs and production equipment following the entire production process. The comparative analysis of emissions from the DPF manufacturing process and reduced particulate air pollutant amounts during the production process revealed particulate air pollutants emissions of 86 kg during the DPF raw material acquisition and manufacturing process. Whereas the total amount of particulate air pollutants reduced by DPFs over three years of production was 2,940 kg, indicating a reduction effect on particulate air pollutants in the entire production process except for the disposal stage. In addition, the analysis result of global warming obtained using the LCA analysis indicated emissions of 11,700 kg CO₂-eq from the manufacturing process of 1EA DPA.

Key Words

Diesel particulate filter, LCA, Life cycle assessment, Particulate matter, Reduction effect

권안규 Ankyu Kwon , 정진도 Jindo Chung

DOI:10.9786/kswm.2023.40.1.64

Abstract

In this study, biomass fuel was injected into a domestic 200 MW fluidized bed boiler to study the characteristics of the boiler’s flow state and performance changes. As the biomass mixing ratio increased, the temperature of the upper part of the boiler increased and combustibility increased. As the amount of biomass increased, the amount of fuel (coal) relatively decreased, and the temperature of the cyclone outlet decreased; it was confirmed that the combustibility increased. As the amount of the circulation flow substance of small particulate matter (ash) increased to the upper part, the upper pressure determines that heat transfer due to the conduction of the water wall tube increased and combustibility improved. It was determined that the heat absorption amount of the rear heat transfer part to the heat exchanger increased and the heat distribution due to the amount of exhaust gas increased.

Key Words

Biomass, CFBC, Superheater, Reheater, Cyclone

이가영 Gayeong Lee , 김나원 Nawon Kim , 김용진 Yong-jin Kim

DOI:10.9786/kswm.2023.40.1.71

Abstract

The amounts of waste plastics continue to increase rapidly each year. Recycling, incineration, and landfilling are the main treatment and disposal processes of waste plastics. Indeed, although incineration has been used to decompose and remove plastic products, it is considered one of the main sources of microplastics (MPs). In recent years, various methods for extracting MPs from environmental media have been proposed by researchers. However, there is still no standardized method for the extraction of MPs. In this study, therefore, in order to efficiently extract MPs from incineration ash (i.e. bottom and fly ashes), separation solution, stirring method, and number of extraction were investigated. Except for the saturated NaCl saturated, good recovery rates were observed in the separation experiments with Oil + 5 g-NaCl/L and ZnCl₂ solutions, ranging from 63 to 80%. In addition, a good recovery rate was observed when using a magnetic stirrer, except for experiments with the ZnCl₂ solution. However, although the extraction was carried out three times in this study, MPs were still detectable, suggesting incomplete extraction of MPs. The obtained recovery rates were not higher than those reported in previous related studies, which might be due to the differences in the samples and the characteristics of MPs with different densities. During the separation process of supernatants, it is necessary to pay attention to the handling process of containers in contact with the samples, as MPs tend to stick to the container walls. Therefore, further related studies are required to develop effective methods for extracting MPs from incinerator ashes.

Key Words

Municipal solid waste, Microplastics, Extraction, Incineration, Bottom ash

신병철 Byung-chul Shin , 장근용 Geun-yong Jang , 최준철 Joon-chul Choi

DOI:10.9786/kswm.2023.40.1.82

Abstract

In this study, an environmental evaluation of a mechanical seal manufacturing process involving recycled silicon from end-of-life PV panels was conducted using the life cycle assessment (LCA) approach. The β-phase silicon carbide (β-SiC), which was synthesized from recycled silicon and carbon through a direct carbonization method, exhibited a high crystallite size range of 18 ~ 21 μm and purity of 99.9%, suggesting its suitability as a raw material for the manufacture of mechanical seals. The wet method of fine grinding and mixing of raw materials was improved to a dry method without using a solvent. Global warming emissions and photochemical oxidants were decreased from 40 to 27.6 kg-CO₂/kg-SiC and 2.23 to 0.124 kg-C₂H₄/kg-SiC, corresponding to decreasing rates of 31.1 and 94.5%, respectively, following the mixing of ground SiC with carbon (C) and the improvement of β-SiC granulation using a dry method. Whereas recycling Si of end-of-life PV panels reduced the resource depletion- and global warming-associated environmental impacts by 61.9 and 64.1%, respectively. On the other hand, weight analysis showed a reduction of the overall environmental impacts by 54.3%, while those related to resource depletion, global warming, and photochemical oxidant formation were reduced by 40.8, 35.7, and 19.4%, respectively, even though only the global warming potential (GWP) exhibited very high values in the characterization results. The obtained results demonstrated the contributions of electricity consumption during the β-SiC synthesis process and high-temperature calcination to global warming. Moreover, SiC chunk results in resource depletion and global warming, while hydrogen peroxide generates photochemical oxidants. The LCA analysis was useful in this study for quantitatively assessing the effects of the improved environmental impacts. Recycling SiC from end-of-life PV panels could be a valuable approach to ensuring sustainable development due to the low carbonization and clean manufacturing process.

Key Words

PV panel, Silicon, Mechanical seal, Life cycle assessment, Global warming