In this study, the efficiency of the anaerobic co-digestion of three categories of rural organic waste (animal manure, slaughterhouse waste, and agricultural by-products) and different mixtures of them was investigated. In addition, the relationship between digestion efficiency and the carbon/nitrogen (C/N) ratio was also conducted. Five different mixtures of feedstock including animal manure as a control were estimated by the biochemical methane potential (BMP) test. The results indicate that the biodegradability of the feedstock mixtures was in the range of 62 ~ 75%, which was at least 1.4 times higher than that of single digestion (43%), while the methane yield was increased by almost twice that of single digestion (0.14 to 0.24 ~ 0.41 ㎥ CH4/kg VSadd). After the BMP test, four feedstock mixtures were selected for a lab-scale reactor, including animal manure as a control sample. The highest methane yield of 0.355 ㎥ CH4/kg VSadd was obtained from the A4-mixture sample. With regard to the C/N ratio, the mixture materials showed an increase in methane yield by at least 1.2 times (13.4 to 16.4 ~ 21.3%), which means that the C/N ratio had an effect on the performance of co-anaerobic digestion.
In this research, we present a new methodology to indirectly assess the concentration levels of the biochemical oxygen demand (BOD) and total nitrogen (T-N) of dewatered cake by evaluating the amounts of the volatile solids (VS) and total solids (TS). Information regarding the BOD and T-N concentrations of dewatered cake could then be used to estimate the Greenhouse Gas (GHG) emissions caused by sewage treatment. To this end, regression equations were derived by considering the relationship between the product of two solid terms: (TS × VS) and BOD/T-N levels of digested sludge. The optimal regression equations for BOD and T-N were computed as y = 152425x (R2= 0.969, p < 0.05) and y = 128378x (R2= 0.970, p < 0.05), respectively. For the purposes of verification, the applicability of the regression equations was tested using the data for other periods not considered in the regression analysis. Accordingly, the differences between the measured and estimated concentration data (derived using the regression equations) were within the standard deviation of the measured concentrations. However, the concentrations estimated by regression equations were quite different from those obtained by conventional methods. Nonetheless, such differences did not significantly change GHG emissions, thus we conclude that the plant specific regression equations can be derived from the methods presented in this study, although more efforts are needed for its validation in various respects.
The amount of ferro-nickel slag powder produced by the Fe-Ni industry has grown in conjunction with the increase in demand for stainless steel materials. In this study, we investigated the effects of ferro-nickel slag powder on the flow, strength, and microstructure of polymer mortar. Ferro-nickel slag powder was used to replace CaCO3 at ratios of 0%, 25%, 50%, 75%, and 100% by volume. The flow and the compressive and flexural strength of the polymer mortar were measured, and both scanning electron microscopy (SEM) and hot resistance testing were performed. The test results indicate that the flow of the polymer mortar with more than 25% CaCO3 replacement decreased as the ferro-nickel slag powder content increased. The compressive strength of the polymer mortar mixes with ferro-nickel slag powder was relatively higher than that of the control mix. From the results of the hot resistance test, the strength improved compared with that before the test and increased as the powder replacement ratio was increased.
This study deals with inorganic Carbon dioxide Capture Utilization (CCU) by using seawater-based industrial wastewater. Industrial wastewater, which contains plenty of cations such as Ca2+ and Mg2+, is considered as a cation source for mineral carbonation. Modeled industrial wastewater was used to study the tendency of mineral carbonation on various condition. Cation concentration of industrial wastewater was modified at various levels and then reacted with fully CO2- absorbed 30wt.% monoethanolamine (MEA) solution. A metal carbonate precipitated as a result of the reaction, and the same experiment was performed with 1/3, 2/3 CO2-absorbed MEA solution to study the tendency of carbonation under different CO32- conditions. The amount of precipitate was increased proportionally to the cation concentration and the amount of absorbed CO2. Most of the precipitate was calcium carbonate (CaCO3), although other metal carbonates were also formed. Most of the CaCO3 was found in calcite form, but vaterite and aragonite were also formed under specific conditions. Based on the experimental results, we conclude that by controlling the concentration of cations and CO32-, we were able to optimize mineral carbonation conditions. We also noticed that low CO32- concentration in MEA solutions is advantageous for producing high quality calcium carbonate crystals. Inductively Coupled Plasma (ICP), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) analyses were performed to analyze the precipitate.
In this study, we analyzed all of the waste streams associated with household waste to provide a basis for incorporating the individual characteristics of municipalities in setting targets for waste-to-resource circulation. Toward this end, we examined how household waste is treated based on the disposal method (mixed waste disposed of in standard volumerate garbage bags, separation recyclable waste, and food waste) and the amount of residuals generated at their respective treatment facilities. The actual recycling rate or actual waste-to-energy conversion rate was calculated as the ratio of the actual amount of waste that is recycled or converted to energy against the amount of waste intake at waste treatment facilities. The conversion factor of actual recycling rates at 17 municipalities showed an average of 63.9% for public material recovery facilities (MRFs) with those for individual municipalities ranging from 50.4% to 93.2%, and an average of 93.8% for private and public food waste treatment facilities with slightly higher rates found for public facilities (70.4 ~ 100%) than private facilities (63.3 ~ 100%). The actual waste-to-energy conversion factor was 59.3% on average for combustible waste-to-energy facilities (17.2 ~ 72.3%) and 92.0% on average for biological waste-to-energy facilities (77.1 ~ 99.5%). To achieve the national target for the actual recycling rate, additional strategies for recycling or converting the residuals generated at recycling or combustible waste-to-energy facilities into resources are needed. The actual recycling and waste-to-energy conversion rates provided in this study based on a full examination of household waste streams hold valuable insights for incorporating the individual situations of municipalities in setting their targets for wasteto- resource circulation indicators and creating new strategies for improving the actual recycling rate.
The aim in this study was to remove Cl-, which can be problematic in the recycling of bottom ash, by identifying the optimum operating conditions for a soil electrolysis apparatus with spiral paddles and to use these as the base data in removing contaminants from various polluted soils using electrolysis. Unprocessed bottom ash collected from the openair storage yard at thermoelectric power plant H in Gyeong sang nam - do Province was used as the experimental material. The experimental methodology was to identify the optimum operating conditions to remove Cl- contained in the bottom ash using the following variables: use or not of spiral paddles, application or not of electrolysis, change of concentration of the electrolyte solution, electrolysis application time, and the voltage level during electrolysis. From the results, the highest removal efficiency of 91.4% was shown under the following conditions: use of the spiral paddles, use of 0.3% NaOH electrolyte solution, 20 min of electrolysis; and a voltage level of 5 V during electrolysis. It is evident that application of the soil electrolysis apparatus for removal of Cl- from bottom ash could be valuableas base data for purification of polluted soils in the future.
According to “Korea Environment Corporation (KECO): Statistical data of specified waste generation and treatment,” the amount of designated waste generated in 2015 was 4,691,532 tons, which is 51.7% higher than the 3,092,591 tons generated in 2005, and the annual output is steadily increasing by 3.25%. Therefore, in order to properly manage the specified wastes, it is necessary to divide them according to the type of industry and waste type and to evaluate the trend of specified waste generation in advance and establish a specified waste management plan. However, due to the statistical data collection and administrative procedures, the timing of the publication of national statistical data is somewhat delayed after the actual generation of specified waste. Since the “National Waste Comprehensive Plan” assumes that GDP and manufacturing output will increase by 4% every year and predicts the amount of specified waste generation in the future, there is a great deal of pressure to use this in the actual field. In this study, we analyzed the correlation between the production index, which is an economic index indicating the change in the output of the products produced by the industry, and the specified waste generation amount. Based on the actual production index, the specified waste statistics for 2017 were predicted and compared with the estimated amount and the actual amount for the 2010 ~ 2015 period.
In this study, a lab-scale experiment was conducted to derive the optimal torrefaction conditions for upscaling food waste torrefaction to generate solid fuel. Basic characteristic analyses (a proximate analysis, elemental analysis, calorific value and thermogravimetric analysis) were conducted and further used to develop experimental conditions during upscaling. Based on the characteristics analysis, the experiments were conducted by varying the heating rates by 5, 10 and 15℃/min, varying the torrefaction temperature from 200 to 550℃ at an interval of 50℃ and varying the torrefaction residence time from 0 to 50 minutes at an interval of 10 minutes. The heating rates were varied and only carried out for the combustion experiments of the torrefied product at a temperature range of 50 to 800℃. The results show that the optimal torrefaction temperature and residence time of food waste torrefaction were 250 ~ 350℃ and 30 ~ 40 minutes, respectively.
Biomass as a renewable energy source has several limitations in terms of the potential for steady supply and its thermal characteristics. This study conducted a thermal weight change analysis and determined its kinetics to address this problem. Sawdust was chosen as the biomass, and PE and PP were the plastics used. Based on the result of thermogravimetric analysis (TGA), the kinetic characteristics were analyzed using Kissinger, Ozawa, and Friedman methods, which are the most common methods used to obtain reaction coefficients and activation energy. The methods used to determine the thermal degradation kinetics were considered feasible for evaluating the pyrolytic behavior of the materials tested. The experimental results of this study provided insights into mixed biomass/plastics pyrolysis kinetics and their optimal operation conditions.
Waste lead-acid batteries accounted for 83% (470,000 tons) of the licensed waste imported into the country in 2015, which was the largest percentage of imported waste in Korea. In addition, there is the problem of negligent management or waste circulation related to international conventions. Therefore, it is necessary to grasp the current status of domestic recycling management and the management of waste batteries. In this study, the current status of domestic and foreign management of waste lead-acid batteries, which is the largest component of imported waste, was investigated. In addition, we examined the import/export regulations, inadequate management or distribution of waste related to international treaties such as the Basel Convention and the Organization for Economic Co-operation and Development (OECD) regulations, and the problem of appropriate treatment management, especially considering waste lead-acid batteries. We studied the proper management method and system for waste lead-acid batteries treatment in Korea, and investigated and compared domestic and foreign laws and treatment guidelines for domestic waste, including those for imported and exported waste. We established a safe resource waste-recycling management system to help the utilization of the basic data necessary for waste management law and business support in relation to international treaties.