Yeon-woo Jeong , Sang-kyu Choi , Yeon-seok Choi , So-young Han , Quynh Van Nguyen

DOI:10.9786/kswm.2021.38.6.473

Abstract

Co-pyrolysis of coffee ground and waste polystyrene foam was performed to produce pyrolysis oil in a tilted-slide reactor. The pretreated waste polystyrene foam was mixed in the ratios of 0%, 25%, 50%, 75%, and 100% with the dried coffee ground by weight. The yield and characteristics of the pyrolysis oil were compared at various mixing ratios. The pyrolysis oil yield increased almost linearly with the mixing ratio of the waste polystyrene foam, and it was 96.95wt% in the case of 100% waste polystyrene foam. The higher heating value of the pyrolysis oil also increased up to 41.44 MJ/kg. Mixing at least 25% of waste polystyrene foam to the coffee ground could significantly reduce the pyrolysis oil viscosity. It can be an efficient method to improve the quality of the pyrolysis oil by enhancing the heating value, and by reducing the viscosity.

Key Words

Co-pyrolysis, Coffee ground, Waste polystyrene foam, Tilted-slide reactor, Pyrolysis oil

정재훈 Jae-hoon Jeung , 이시진 Si-jin Lee

DOI:10.9786/kswm.2021.38.6.483

Abstract

In this paper, we studied the efficiency of reducing sulfur inhibition during anaerobic digestion using biochar. The study was conducted using a batch test called the biochemical methane potential test in which various concentrations of Na2S were injected to determine the effects of sulfur. This experiment used leached food wastewater as the feedstock, and the composition of the experiment was divided into three sets; In Set 1, only Na2S was injected except for control, based on sulfur concentration (20-1,000 mg/L). In Set 2, biochar (BC, 5 g/L) were additionally injected to the Set 1 conditions. For comparison, FeCl₃ (24 g/ L) was injected together with Na₂S in Set 3. The experiment indicated that overall the concentration of H₂S in the generated biogas was significantly lower than that of other sets in Set 3 (injected with FeCl₃). Furthermore, the concentration of H2S in Set 2 (injected with biochar) was found to be lower than that of Set 1 in the low-concentration range of Na₂S. However, there was no significant difference from Set 1 in the high concentration range of Na₂S. This result indicates that biochar can reduce the inhibition of sulfur; however, the efficiency decreases as the concentration increases. Furthermore, Set 3 yielded lower methane compared to the other sets, where the lowest biogas yield and methane yield were found to be 200+Fe in Set 3 as 0.046 m³/kgVS and 0.021 m³/kgVS, respectively. On the other hand, the highest biogas yield and methane yield were found to be 25+BC in Set 2 as 0.308 m³/kgVS and 0.166 m³/kgVS, respectively. This result indicates that Fe can reduce the effects of sulfur; however, it cannot enhance the efficiency of biogas production. Meanwhile, biochar has been seen to enhance both sulfur control and biogas production efficiency and hence can be used as a valuable material.

Key Words

Anaerobic digestion, Sulfur inhibition, Biochar, FeCl₃

최자형 Ja-hyung Choi , 이선주 Sun-ju Lee , 김용준 Yong-jun Kim , 강영렬 Young-yeul Kang , 전태완 Tae-wan Jeon , 엄남일 Nam-il Um

DOI:10.9786/kswm.2021.38.6.493

Abstract

This study presents an improvement plan for the crushed sand manufacturing process (CSMP) through hazard assessment, utilization of CSMP waste, and process risk management. In Korea, the wet method has been applied to most CSMPs because of the technical aspects, production volume, and efficiency. To assess the harmfulness of wet CSMP waste, the analysis methods of leaching toxicity information on flocculants were investigated. Furthermore, to evaluate the risks of waste from CSMP due to its high moisture content, a fluidity test was conducted. The results indicated that there is no effect on the harmfulness of the target waste. However, it is difficult to guarantee unconditional safety because of the lack of detailed ecotoxicity information of the flocculant used for the washing process in the CSMPs. Finally, based on these results, the improvement plan of CSMPs was suggested. This plan includes the design operation guidelines to enable consistent process operation through standardized cleaning and dewatering process. In addition, the basic data with an effective management system of CSMP waste for increasing recycling was also suggested.

Key Words

Crushed sand, Stone waste, Flocculant, Recycling

홍준석 Jun Suk Hong , 박중구 Jung Gu Park

DOI:10.9786/kswm.2021.38.6.506

Abstract

This article analyzes the direct relationship between R&D input and the economic outcome of Korean environmental companies, and examines the impact of government policy and technological output that play a mediating role in this process. To this end, a questionnaire survey was conducted on 201 Korean environmental companies, and the analysis was based on SPSS and AMOS. The results form the analyses indicated the following : ① the increase in companies’ R&D input did not directely affect their economic outcome, ② the government policy did not efficiently medicate the relationship between the R&D input and the economic outcome of environmental companies. ③ technological output positively mediated the relationship between the R&D input and the economic outcome. ④ the government policy and technological output have sequential mediating effects in the process that the R&D input ultimately resulted in the economic outcome. According to these results, the policy implications are as follows : ① Korean environmental companies need to make sincere efforts to increase the effectiveness of R&D input. ② it is necessary to design and implement government policy that considers not only technical output but also economic outcome. ③ government policy needs to expand corporate R&D input and increase the efficiency between R&D input and technological output. ④ it is necessary to design government policy and management strategies that take into consideration the process from R&D input to the economic outcome. Some of the limitations of this thesis are as follows ① the analyses were based on the data from survey ② it has not analyzed by sectors, such as water, air, and waste. Finally, an in-depth and multilateral analysis of environmental companies is required according to the newly defined green industry classification in Korea.

Key Words

Korean environmental companies, R&D input, Technological output·economic outcome, Mediating effects, Government policy

이상철 Sang-chul Lee , 김관용 Gwan-yong Kim , 정득준 Deuk-jun Jung

DOI:10.9786/kswm.2021.38.6.520

Abstract

This study deals with developing materials using waste leather and binders for sustainable material development by replacing butyl rubber, which is currently entirely dependent on imports. Since butyl rubber has few double bonds, the production efficiency is low because of the slow speed in the vulcanization process. Since the temperature of the process must be increased, an alternative material is required. Industries and research institutes are currently studying outsole pattern application and rubber mixing to replace butyl rubber, but technology development using recycled products is currently unavailable. This study developed an outsole material according to the type of rubber binder and the fibrous length of the leather waste. The bonding characteristics, crosslinking characteristics, abrasion resistance, and slip characteristics of the developed material were studied.

Key Words

Waste leather, Out-sole, Non-slip, Fiber phase structure

심소영 So Young Sim , 왕지유 Zhi Rou Wang , 장현민 Hyun Min Jang

DOI:10.9786/kswm.2021.38.6.529

Abstract

Over the past decade, thermophilic aerobic digestion (TAD) has been considered a practical approach to treating highstrength wastewater because of its several advantages. In this study, batch-mode TAD of sewage sludge was conducted using a lab-scale bioreactor to evaluate the changes in solid and soluble organic compounds. The TAD process achieved rapid degradation of the solid compound at 55oC. The removal efficiency of volatile suspended solids (VSS) increased rapidly at the early operation stage and achieved 25% at 48 h. Then, the VSS removal efficiency increased gradually up to approximately 40% at the end of the digestion (168 h). As a result of VSS degradation, the soluble chemical oxygen demand (SCOD) increased significantly up to 12 g/L at 36 h and then showed a slow decline pattern. Furthermore, the pattern of protease activity was similar to that of the SCOD. This result indicates that the rapid degradation of VSS is highly linked to the increase of protease activity and thermophilic conditions. This study used acetic acid and propionic acid. The variation patterns were similar under both acetic acid and propionic acid. The concentrations of acetic acid and propionic acid rapidly increased up to 3.05 g COD/L at 48 h and 2.51 g COD/L at 36 h, respectively. Then, major volatile fatty acids concentrations declined sharply and became undetectable after 144 h. Similar to the SCOD variation pattern, the soluble total nitrogen and NH4+-N also decreased sharply after 72 h. This might be because ammonia stripping is enhanced by pH rising and continuous aeration during the TAD.

Key Words

Thermophilic aerobic digestion, Sewage sludge, Soluble organic compound, Protease activity

김종범 Jong Bum Kim , 류재용 Jae Yong Ryu

DOI:10.9786/kswm.2021.38.6.535

Abstract

The cement industry is a typical energy-intensive industry that emits massive greenhouse gases during decarboxylation and calcination with high energy consumption per unit of value-added production. As a result, the pressure for mandatory reduction of cement production increases, which leads to a considerable economic loss. Since the marginal cost of greenhouse gas reduction is high, it is necessary to apply the development of economical greenhouse gas reduction measures and technologies. Sulfur hexafluoride (SF₆) is a greenhouse gas with a very high global warming potential, it is mainly used for insulating materials and semiconductors for electric power and transmission facilities with heavy electric fields. This study aims to decompose SF₆ gas which gets discarded after being used as an insulator for heavy electric devices in high temperatures by fixating it into free calcium oxide (CaO) in cement kilns and using it as a supplementary material like fluorspar and plaster. Based on results from previous research, in this study the discarded SF⁶ was fixated it into the bead type of CaO under a fixation temperature of 1000℃. The fixation rate calculated using the concentration difference between the front end and the hinder end of the decomposed by-products was 95% on average. The bead type of the fixated by-product was largely composed of calcium fluoride, anhydrite, and portlandite as the main composition minerals. Therefore, it is considered that if sulphur hexafluoride can be decomposed in high temperatures and fixated into free CaO in cement kilns, it can be used as supplementary minerals like fluorspar and plaster.

Key Words

Sulfur hexafluoride, Plasma, High-Temperature, Pyrolysis, Immobilization

이소라 Sora Yl

DOI:10.9786/kswm.2021.38.6.545

Abstract

This study examines the amount of waste generated by tourists at popular tourist destinations through the case of Jeju Special Self-governing Province (Jeju) in South Korea. First, the population of the local residents and that of inbound tourists and their length of stay were considered in the computation of municipal waste generation in Jeju to differentiate the amount of municipal waste generated by local residents and that by tourists. Next, to calculate the amount of waste generated by tourism-related activities and tourists on a daily basis (kg/person/day), this study chose major sources of tourism waste in the marine and air transport sectors (ferry and port, airline and airport, car rental and bus charters), wholesale and retail sectors (duty-free shops), lodging and restaurant industries (lodgings and in-house facilities and restaurants), and tourism industry (tourist attractions) and compiled the data on commercial waste generation from tourist sites through written surveys and field research. When the waste generated by tourists was considered in the municipal waste generated per capita in Jeju (1.77 kg/person/day), the amount generated by the residents of Jeju was found to be 1.42 kg/person/day, and approximately 19.5% of the total municipal waste originated from tourists. Moreover, daily tourism-related commercial waste generation per person was calculated to be 0.66 kg/person/day on average, with one tourist generating 1.01 kg/person/ day of tourism waste when assuming that an average tourist visits 1.3 tourist attractions per day. The study’s findings reveal the need to enforce strict measures for businesses that generate large amounts of waste, as well as enforcing waste discharge reporting and limiting the type of businesses that are allowed to take their waste to designated waste collection points. The results of this study can be used as a base data for introducing green taxes that apply the “polluter pays” principle to individual emitters. Furthermore, the analysis results provided a basis for designing efficient policies and strategies for improving waste treatment systems and reducing waste generation at popular tourist destinations.

Key Words

Tourism waste, Municipal waste, Commercial waste, Daily waste generation per person

전수민 Soomin Jeon

DOI:10.9786/kswm.2021.38.6.555

Abstract

The recycled coarse aggregates for concretes that meet the quality standards set by the Ministry of Land, Infrastructure, and Transport are certified based on the audit and test results. After certification, follow-up management which includes audits and tests are conducted every year. In this paper, the correlation between the audit and the test results was examined. Specifically, it was examined whether the audit of coarse aggregates conducted in 2020 had a significant relationship with the suitability of each inspection item and the quality test results. Finally, it was found that there was a significant relationship between the overall audit results and the test results.

Key Words

Recycled aggregate, Coarse aggregate, Certified aggregate, Follow-up management

원민희 Minhee Won , 이재영 Jai-young Lee

DOI:10.9786/kswm.2021.38.6.561

Abstract

As an alternative to a new and renewable energy source, bio-coal is generated through hydrothermal carbonization (HTC) which is a novel renewable energy production technology using waste. Therefore, bio-coal was generated through HTC reaction using wood waste, which is the most used biomass raw material and requires a recycling method and confirmed its possibility as a solid fuel. It can be seen that the higher the reaction temperature and the longer the reaction time, the higher is the fixed carbon content, which affects the heating value. At 300℃ and 4 h, the lowest heating value was 6841.23 Kcal/kg. In addition, the fuel ratio at 300℃ was 1.3 ~ 1.6, which indicates a higher fuel ratio range than that of low-grade coal, and it can be seen from the van krevelen diagram that the biomass region is closer to the lignite region.

Key Words

Hydrothermal Carbonization(HTC), Wood waste, Bio-Coal