Under the stressed condition, a complex feedback mechanism for stress is activated to maintain homeostasis of the body and secretes several stress hormones. But these stress hormones impair synthesis and secretion of the reproductive hormones, followed by suppression of ovarian function. Cytochrome P450 1A2 (CYP1A2) plays a major role in metabolizing exogenous substances and endogenous hormones, and its expression is recently identified at not only the liver but also several organs with respect to the pancreas, lung and ovary. Although the expression of CYP1A2 can be also affected by several factors, understanding for the changed pattern of the ovarian CYP1A2 expression upon stress induction is still limited. Therefore, CYP1A2 expression in the ovaries from immobilization stress-induced rats were assessed in the present study. The stress-induced rats in the present study exhibited the physiological changes in terms of increased stress hormone level and decreased body weight gains. Under immunohistological observation, the ovarian CYP1A2 expression in both control and the stressed ovary was localized in the antral to pre-ovulatory follicles. However, its expression level was significantly (p < 0.01) higher in the stress-induced group than control group. In addition, stress-induced group presented more abundant CYP1A2-positive follicles (%) than control group. Since expression of the ovarian CYP1A2 was highly related with follicle atresia, increased expression of CYP1A2 in the stressed ovary might be associated with changes of the ovarian follicular dynamics due to stress induction. We hope that these findings have important implications in the fields of the reproductive biology.

Cytochrome P450 1A2 (CYP1A2) is a member of the cytochrome P450 superfamily enzymes in mammals and plays a major role in metabolizing endogenous hormones in the liver. In recent days, CYP1A2 expression has been found in not only the liver but also other tissues including the pancreas and lung. However, little information is available regarding the expression of CYP1A2 in the ovary, in spite of the facts that the ovarian follicle growth and atresia are tightly associated with controls of endocrine hormonal networks. Therefore, the expression of CYP1A2 in the ovaries of prepubertal and pubertal rats was investigated to assess its expression pattern and puberty-related alteration. It was demonstrated that the expression level of CYP1A2 was significantly (p < 0.01) higher in the pubertal ovaries than prepubertal counterparts. At the ovarian follicle level in both groups, whereas CYP1A2 expression was less detectable in the primordial, primary and secondary follicles, the strongly positive expression of CYP1A2 was localized in the granulosa cell layers in the antral and pre-ovulatory follicles. However, the ratio of CYP1A2-positive ovarian follicle was significantly (p < 0.01) higher in the ovary of pubertal group (73.1 ± 3.1%) than prepubertal one (41.0 ± 10.5%). During the Immunofluorescence, expression of CYP1A2 was mainly localized in Fas-positive follicles, indicating the atretic follicles. In conclusion, these results suggested that CYP1A2 expression was mainly localized at the atretic follicular cells and affected by the onset of puberty. Further study is still necessary but we hypothesize that CYP1A2 expresses in the atretic follicles to metabolize residue of the reproductive hormones. These findings may have important implications for the fields of reproductive biology of animals.

A recent study has reported that pluripotent stem cells can be categorized according to their pluripotent state. The first is a “naïve” state, which is characterized by small, round or dome-shaped colony morphologies, LIF and BMP4 signaling pathways and two active X chromosomes in female; mouse ES cells (mESCs) represent this type. A second “primed” state has also been described and is possible in mouse epiblast stem cells (mEpiSCs) or human ES cells (hESCs). These primed state pluripotent stem cells display flattened monolayer colony morphologies, FGF and Nodal/Activin signaling pathways and X chromosome inactivation in female. It has been suggested that, as a non-permissive species, the porcine species undergoes reprogramming into a primed state during the establishment of pluripotent stem cell lines. Meanwhile, a few studies have reported that primed pluripotent stem cell lines could be reverted to a naïve pluripotent state using various exogenous factors including GSK3β and MEK inhibitors, LIF, hypoxic conditions and up-regulation of Oct3 or klf4. Therefore, the purpose of this study was to investigate whether a LIF-dependent naïve pluripotent stem cell line could be derived from porcine embryonic fibroblasts(PEFs) via doxycycline (dox)-inducible reprogramming factors and LIF. In this study, we have been able to successfully induce PEFs into a LIF-dependent naïve pluripotent-like cell line showing a mESC-like morphology and the expression of pluripotent markers. Our results suggest the possibility of reprogramming to naive pluripotent- like stem cells from PEFs in porcine species. * This work was supported by the BioGreen 21 Program (PJ0081382011), Rural Development Administration, Republic of Korea.

Several studies have been conducted with the aim of establishing embryonic stem cell lines from porcine embryos. However, most researchers to date have found it difficult to maintain an ES-like state in derived cell lines, with the cells showing a strong tendency to differentiate into an epithelial or EpiSC-like state. We have also been able to derive cell lines of an EpiSC-like state and a differentiated non-ES-like state from porcine embryos of various origins, including invitro fertilized(IVF), in vivo derived, IVF aggregated and parthenogenetic embryos. In addition, we have generated induced pluripotent stem cells(piPSCs) via plasmid transfection of reprogramming factors (Oct4, Sox2, Klf4 and c-Myc) into porcine fibroblast cells. X chromosome inactivation (XCI) have recently been addressed as a hallmark to determine whether pluripotent cell is naïve or primed state. In this study, we could confirm the X chromosome inactivation status in female cell lines as well as marker expression, pluripotency and of our Epi- SC-like pESC lines along with our piPSC line. All of our cell lines showed AP activity and expressions of the genes Oct4, Sox2, Nanog, Rex, TDGF1, bFGF, FGFR1, FGFR2, Nodal and Activin-A involved in pluripotency and signaling pathways, XCI in female cell lines, in vitro differentiation potential and a normal karyotype, thus displaying similarities to epiblast stem cells or hES cells. Therefore, it may be inferred that, as a non-permissive species, the porcine species undergoes reprogramming into a primed state during the establishment of pluripotent stem cell lines.

In 2018, the Korean government introduced a landfill levy under the Framework Act on Resource Circulation. This was a fiscal measure to ensure that landfill waste disposal is priced so as to reflect its environmental cost and to help promote more sustainable waste management. This study aims to investigate the effectiveness of the landfill levy as a landfill policy instrument in Korea. In this study, a literature survey was conducted on the existing theoretical and empirical insights to the effectiveness of landfill taxes, including experiences in several EU countries. This survey shows that if landfill taxes are to be effective in terms of reducing the amount of waste going to landfills, the tax rate should be put at a fairly high level. It should be noted that the landfill tax rates should be set based on the external cost of landfill disposal. In addition, it appears that the landfill tax has not significantly affected generated waste per capita in the EU. The landfill tax can result in negative effects. Due to the reduction of waste sent to landfills, there is a risk that landfill operators will not be able to fulfil their financial obligations for closure and aftercare. Additionally, after closure and construction of the surface sealing, the emissions potential of the waste body remains more or less constant, resulting in the extended time-scale and uncertain funding of the post-closure period. This is a problem applicable to most landfills that contain inorganic waste. Thus, landfill operators should be stimulated by means of appropriate regulations to stabilize the waste body as much as possible to guarantee the lowest possible emission potential. This requires financial incentives, which are implemented to encourage operators to actively advance the stabilization of landfill waste.

유엔기후변화협약(UNFCC)은 온실가스 배출통계의 중요성을 강조함에 따라 모든 당사국들은 국가 온실가스 인벤토리 산정 보고서를 제출할 의무를 명시하고 있다. 국가 온실가스 인벤토리 분야에는 폐기물 분야도 포함되어 있으며, 특히 메탄배출량의 상당량을 차지하는 폐기물매립지에 대한 온실가스 배출량 산정은 매우 중요시되고 있다. 그럼에도 불구하고 국내 폐기물매립지는 아직까지 GPG(Good practice guidance) 2000에 기반하여 온실가스 배출량을 산정하고 있어 2006 IPCC 가이드라인을 기준으로 매립지 온실가스 배출량을 산정하고 있는 미국과 EU 국가 등과 비교하여 배출량 산정의 정확도가 낮은 문제점을 나타내고 있다. 이에 본 연구에서는 GPG 2000과 2006 IPCC 가이드라인(Tier 1, 2)을 기반으로 국내 폐기물매립지의 온실가스 배출량을 산정 및 비교함으로써 폐기물매립지 온실가스 배출량 산정방법의 문제점 및 개선방향을 제시하고자 하였다. 각 방법별 폐기물매립지의 국가 온실가스 배출량 산정 결과, 2015년 기준으로 2006 IPCC Tier 1의 배출량은 10,885 Gg CO2eq,로 가장 높게 나타났으며, 다음으로 2006 IPCC Tier 2(9,443 Gg CO2eq,), GPG 2000(7,727Gg CO2eq)순으로 나타났다. GPG 2000과 2006 IPCC 가이드라인 모두 FOD 모델을 기반으로 하고 있기 때문에 연도별 배출량 증감은 비슷하였으나 GPG 2000은 매립폐기물 전부를 하나의 단일 성상으로 가정한 반면 2006 IPCC에서는 폐기물 성상별로 배출계수를 적용하도록 하고 있어 배출량의 차이가 발생하였다. 다만 2006 IPCC에서는 국가 배출계수의 적용을 권고하고 있어 향후 이에 대한 지속적 개발 및 검증이 이루어져야 할 것이다.

In 2018 the South Korean Government introduced the Resource Circulation Act that included a landfill levy (tax) in order to reduce the amount of waste going to landfill sites and to promote recycling. The objective of this study is to examine the negative and positive effects of landfill tax on national waste management by reviewing case studies from the European Union (EU). In December 2015, the European Commission proposed the Circular Economy Package that sets ambitious recycling rates of 65% and a maximum 10% landfill rate for municipal wastes by 2030, and the European Commission decided that the landfill tax could help move towards these aims. Indeed since the late 1990s, most of the countries in the European Union have introduced landfill taxes. Landfill rates of these countries showed a tendency to decrease gradually. Currently the landfill rates for the Netherlands, Sweden, Denmark and Norway are less than 5%, and those for the UK, France and Italy have fallen below 30%. However, the landfill tax also had negative effects. In the case of the Netherlands, too little waste was sent to landfills, and private companies can no longer profit. Consequently the companies will not be able to fulfil their financial obligations for closure and aftercare. Thus, based on the results of this study, it is necessary to further consider the landfill levy in Korea.

The objective of this research was to estimate the greenhouse gas (GHG) emission factors for food, paper, and wood wastes through methane (CH4) flow analysis. The GHG emissions from a given amount of landfill waste depend on the carbon (C) flows in the waste: (1) carbon storage in landfills, (2) C in carbon dioxide (CO2) and CH4 generated in anaerobic waste decomposition, (3) C in CO2 and CH4 emitted to the atmosphere through vertical gas wells, (4) C in CO2 from CH4 oxidation through cover soils, and (5) C in CH4 emitted to the atmosphere through cover soils. This study reviews the literature on the ranges for DOCf (the fraction of degradable organic carbon that can decompose) and OX (oxidation factor) values of food, paper, and wood, with a particular focus on the role of lignin. There is an inverse relationship between lignin and the DOCf of paper and wood wastes. In this respect, the lignin content could be used as an abatement indicator for the DOCf of paper and wood. The literature review shows that the average DOCf values for food, paper, and wood were 0.72, 0.61, and 0.12, respectively. The country-specific DOCf value for wood (0.44) is significantly higher than the ranges reported in the literature, which implies that the country-specific DOCf for wood can overestimate GHG emissions compared to the DOCf obtained from the literature. The estimated GHG emissions factors were 1,055 kg-CO2e/ ton-wet waste for food, 1,367 kg-CO2e/ton-wet waste for paper, and 276 kg-CO2e/ton-wet waste for wood. Sensitivity analysis results showed that the most influential parameters were MCF (CH4 correction factor), DOCf, and OX. In order to reduce GHG emissions from landfill in Korea, landfill sites currently in operation should be converted from anaerobic to semi-aerobic.

폐기물매립지에서 함수율은 폐기물의 분해속도뿐만 아니라 폐기물의 분해율에도 영향을 미치는 것으로 알려져 있으며, 이에 매립지 내부의 수분을 인위적으로 증가시켜 매립가스 발생량을 증대시키는 bioreactor 공법이 연구되고 있다. 따라서 향후에는 국내외 매립가스 자원화를 계획 및 진행하고 있는 폐기물매립지를 대상으로 bioreactor 공법이 적용될 것으로 예상되며, 이를 위해 매립지 내부의 함수율 변화에 따른 매립가스 발생특성이 예측되어야 할 것이다. 그러나 기존 연구들에서는 실내실험 및 현장 실증실험을 통하여 bioreactor 공법 적용에 따른 조기안정화 및 매립가스 발생량 증대 효과만을 나타내었을 뿐 함수율 변화가 폐기물의 분해도 및 분해속도에 미치는 영향을 수치적으로 나타내지 않아 bioreactor 공법 적용에 따른 정확하고 신뢰성 있는 매립가스 발생량 예측이 어려운 점이 있다. 이에 본 연구에서는 매립지 내부에서의 함수율 변화가 메탄발생 특성에 미치는 영향을 평가하여 향후 함수율 변화에 따른 메탄발생량 및 발생속도 예측의 기초자료로 이용하고자 하였다. 시료는 가연물 중 매립지에 가장 높은 비율로 매립되는 종이를 대상으로 하였다. 각 반응조별 초기 함수율은 10%, 20%, 30%, 40%, 50%로 설정하였으며, 초기함수율 10~40%의 반응조들은 가스발생이 중지되었을 때 함수율을 10%씩 증가시켜 최종적으로는 모든 반응조의 함수율이 50%에 도달하도록 실험을 진행하였다. 실험결과 메탄발생이 최초 중지되는 시점의 각 반응조별 메탄발생 비율은 50% 반응조 대비 10%는 0.4%, 20%는 0.8%로 메탄발생이 매우 미미하였으며, 30%는 6.5%, 40%는 28.9%로 매우 적은 메탄발생 비율을 나타내었다. 이후 각 반응조마다 메탄발생이 중지되는 시점에 함수율을 10%씩 증가시켜 모든 반응조의 최종 함수율이 50%가 되도록 하였으며, 실험 종료 후 메탄발생 비율은 초기함수율 50% 대비 10%는 3.5%, 20%는 7.0%, 30%는 25.1%, 40%는 49.6%로 나타났다. 이론적으로는 초기 함수율이 낮아도 최종 함수율이 동일하면 유기물의 분해속도는 달라도 최종 함수율이 나타내는 메탄발생량과 동일한 값을 나타내어야 하나 초기함수율 10~40% 반응조 모두 초기함수율 50%가 나타내는 메탄발생량에 훨씬 못미치는 메탄발생량을 나타내었다. 따라서 메탄발생량과 연관하여 초기함수율은 매우 중요 인자이며, 메탄발생이 중지되는 시점에 수분을 추가로 주입하면 메탄발생이 다시 시작되나 최종 메탄발생량은 초기 함수율이 낮을수록 크지 않을 것으로 판단된다.

The objective of this study was to determine the CH4 oxidation factor (%) and the CH4 oxidation rate (g m−2 d−1) in landfill cover soil. To quantify in-situ rates of CH4 oxidation, CH4 and CO2 fluxes were measured on a landfill site using the static chamber technique. The CH4 oxidation factor obtained in this study through the mass balance method ranged between 41% and 61%, which is much higher than the Intergovernmental Panel on Climate Change (IPCC) default value of 10%. The higher CH4 oxidation factor derived in this study can be explained by the CH4 bottom flux in addition to the soil texture. The CH4 oxidation factors were observed to increase with decreases in CH4 bottom flux. Therefore, when CH4 bottom fluxes are high in a landfill, using a gas collection system can enhance CH4 oxidation factor. The CH4 oxidation rates were estimated to range from 16.6 g m−2 d−1 to 20.8 g m−2 d−1. In addition, this study was conducted to evaluate the effects of vegetation on the CH4 oxidation factor. The results showed that the CH4 oxidation factors for bare soil, vegetated soil, and soil adjacent to a gas well were 57%, 70%, and 44%, respectively. The results indicate that vegetation on landfill covers can increase the CH4 oxidation factor because of increasing soil porosity.

The Intergovernmental Panel on Climate Change (IPCC) recommended the first order decay (FOD) model for estimating methane emissions from solid waste landfills. However, selecting appropriate parameter is a major challenge in methane emission modeling. The degradable organic carbon (DOC) and the fraction of degradable organic carbon which decomposes (DOCF) are the two primary parameters in the methane generation potential (L0). The DOC is the amount of organic carbon that can be decomposed by biochemical reactions in microorganisms. Chemical analysis methods are currently available to measure the DOC including using total organic carbon and element analysis methods. However, chemical analysis methods are not appropriate for determination of the DOC, which indicated that the DOC should be measured by biochemical tests. In addition, these methods should consider a fossil carbon content that needs a complex and high cost of analysis. The DOCF is an estimate of the fraction of carbon that is ultimately degraded and released from landfills. However, no methodology is provided for determination of the DOCF in landfills. Therefore, the purpose of this study was to suggest methodologies for the determination of DOC and DOCF in solid waste landfills. A biochemical methane potential (BMP) test could be used to calculate the DOC because the BMP represents an upper limit on the methane potential of a waste, which corresponds to a maximal amount of degraded organic carbon. The calculation was based on the assumption that the DOCF is 100%. In this study, two methodologies were suggested to determine the DOCF in landfills. The first one uses a new equation (DOCF = 2.76W-0.44) with moisture content in the landfill that actual methane flux data are unavailable. Moisture content is a major ecological parameter on the anaerobic biodegradability of the solid waste in the landfill. Another methodology is to use L0,Landfill/L0,BMP ratio. The L0,Landfill could be determined by a regression analysis if methane flux data were available.

The objective of this paper is to assess the applicability of heat recovery at aerobic landfill as a geothermal heat source.This paper presents a case study of installing gas source heat recovery system at an aerobic landfill to collect landfillgas heat. The system consists of three subsystems, i.e., the air injection system including a biofilter, the heat pump systemand the thermal storage tank. A biofilter is necessary to remove the content of harmful compounds in the gas that entersthe heat pump. The field test results showed that temperature for landfill gas was increased slightly from 29 to 38oC inthe phase of aeration because of decomposition of organic carbon. The biofilter effectively treated CH4, H2S and NH3in the gas to prevent the corrosion of the heat pump. The coefficient of performance (COP) of the heat pump was 3.2,which means that 3.2kW of heat energy could be obtained by 1kW of electrical energy used for the heat pump. Thisstudy estimated the energy cost for the different heating systems. As a result, the heat pump can reduce the energy costby 75% compared with kerosene and diesel. Therefore, it is concluded that aerobic landfills are a suitable resource forheat recovery.

Heat is generated from decomposition of wastes as a result of chemical and biological processes in aerated landfills. The purpose of this study was to assess temperature and predict its variations in an aerated landfill. In the phase of aeration, temperature was increased slightly from 30 to 34oC until 65 days and then increased significantly from 34 to 74oC by termination of aeration. It indicates that the amount of oxygen supplied in the starting phase of aeration was insufficient to decompose organic carbon because oxygen supplied in the landfill was only consumed for methane oxidation. Additionally, to minimize the risk of self-ignition, drying and process inhibition, aerated landfills should be operated in a temperature range of 54 ~ 66oC through cooling by water addition and terminating or excessive oxygen supply. In this study, a stoichiometric modeling approach considering methane oxidation and decomposition of organic carbon has been suggested for predicting temperature variations in aerated landfills. As a result, the predicted temperature variations obtained the stoichiometric modeling led to similar results compared with measured temperature in aerated landfill. Therefore, it showed that the stoichiometric approach was appropriate for predicting temperature variation in aerated landfills. In addition, heat generation rates for methane oxidation and decomposition of organic carbon were 89.5 and 387.8 MJ/m3·yr, respectively.

Mathematical models have been developed to evaluate methane emission from landfills. The Intergovernmental Panel on Climate Change (IPCC) and the US Environmental Protection Agency (USEPA) have provided first-order decay (FOD) models to estimate methane emission from landfills. The methane generation potential (L0) and the methane generation rate constant (k) are the two primary parameters in the FOD model. A major challenge in landfill gas modeling is estimating these parameters. The IPCC recommended that every country should develop country-specific emission factors appropriate for its circumstances and characteristics. The k value represents the rate constant associated with waste decomposition. In general, there are two different approaches for estimating a k value for a landfill. One uses actual field data in comparison with modeled data. However, this approach is limited by the spatial and temporal characteristics of landfill. Another approach is to collect samples of landfilled waste and then measure their biodegradability of waste as a function of waste age. As biodegradability is a surrogate for landfilling age, lower biodegradability would be expected in order samples. The objective of this study was to determine a k value using an anaerobic test (GB21). To achieve this objective, the GB21 which is used in Germany was conducted to estimate biodegradability of waste samples, and k value was determined based on FOD equation. Waste samples were collected at a landfill located in A City, Korea. The landfill is a valley-type landfill. It received municipal solid waste from 1990 to 2010. Food and paper wastes were the major fractions, constituting about 62.9% of the total amount disposed. However, the Ministry of Environment in Korea banned direct landfilling of food wastes in 2005, since then, food waste has no longer been disposed into landfills. In this study, the landfill site was separated into four areas based on landfilling age, and four samples were collected from each area. Cumulative biogas production for the waste excavated from the landfill varied from 6.9 to 35.8 Nl/kg-Dry Matter. Cumulative biogas production for landfilling age of 1 year was 35.8 Nl/kg-DM and it decreased to 6.9 Nl/kg-DM after 14 years. The k value obtained from this study was 0.156 yr-1 and was higher than the default k prescribed by the IPCC, which is 0.09 yr-1 in boreal and temperate climates. The higher k values obtained in this study can be explained by the high proportion of food waste disposed into the studied landfill. The default k values of rapidly degrading wastes including food waste and sludge are 0.185 yr-1. In addition a higher k value will result in predictions of more methane generation in the early years after waste burial, resulting in higher estimates of uncollected methane in greenhouse gas inventories. This work contributes to understanding decomposition rate of landfilled waste by examining biodegradability determination and providing k value for landfill.

The IPCC methodology for estimating methane emissions from a solid waste landfill is based on the first order decay (FOD) method. One emission factor in the model is the methane generation potential (L0) that is estimated from the amount of decomposable degradable organic carbon (DOC) in a solid waste landfill. L0 is estimated based on the fraction of DOC in the waste, the fraction of the degradable organic carbon that decomposes under anaerobic conditions (DOCf), methane correction factor (MCF), and the fraction of methane in generated landfill gas (F). The other emission factor is the methane generation rate constant (k). The IPCC recommended that every country needs to develop country-specific key parameters (DOC, DOCf, k) more appropriate for its circumstances and characteristics. The objective of this research was to investigate the greenhouse gas emission factor (k) and parameters (DOC, DOCf) for wood wastes in a solid waste landfill. To investigate DOC, DOCf, and k for wood wastes, the biodegradable rate of wood wastes was determined by comparing the composition of excavated samples (L-1, L-2) with their fresh ones (F-1, F-2). The DOC values were found to be 48.36% and 45.27% for F-1 and F-2, respectively. It showed that the IPCC default value of DOC for wood wastes is appropriate for estimating methane emission. The maximum DOCf (0.17 and 0.18) or each wood waste excavated from G landfill was found to be lower compared with those for IPCC. The IPCC provided that default values of DOCf 0.5. The k values were found to be 0.0055 and 0.0058 year−1 for F-1 and F-2, respectively. The result confirmed that the biodegradation rate of wood wastes was very slow due to its lignin.