Objective. This paper overviews current knowledge on emissions of methane（CH4）and nitrous oxide（N2O）from agricultural land.
Results and Discussion. Agricultural land use is identified to be a major source for atmospheric CH4 and N2O. It is pointed out that extended cultivation of paddy rice and dramatic increase in the consumption of fertilizer nitrogen have been significantly increased emission rates of CH4 and N2O, respectively. An emission database of rice fields in Asian countries were compiled and analyzed by a statistical approach. A large number of field measurements for CH4 and N2O conducted at various sites in the world was compiled as databases. Statistical analysis of these databases developed methodologies for estimating regional and global emission rates, such as those in the IPCC Guidelines. Results of the field measurement experiments also suggested promising mitigation options for agricultural emissions of CH4 and N2O.
Conclusions. The review of the research advance indicates the effects of agricultural emissions of CH4 and N2O on global warming and the potentials of mitigation options. Further studies and actions are needed to develop practical systems for extending the mitigation options to local farmers.
Soil organic carbon（SOC）is a huge and important component of the global carbon cycle. Agricultural soils can be either a sink or a source of atmospheric CO2, depending on the balance between the input of carbon（C）to soils and the output of C through decomposition. We can change this balance by changing agricultural soil management, understanding the mechanisms of SOC turnover. Not only the quantity but also the quality of input C affects SOC balance, and environmental conditions such as temperature and moisture of soils as well as inherent properties of soils such as texture affect the decomposition rate of SOC. Since there are many factors affecting SOC balance, SOC turnover models are very useful tools to evaluate the effect of management practices on SOC balance. The RothC model, one of leading SOC models in the world, was validated against long-term experiments in Japan and Thailand, and modified RothC models for paddy soils and for Andosols was developed. The country scale potential of soil carbon sequestration was estimated, then, by using the RothC model for Japanese arable lands. The use of LCA, which includes not only changes in SOC, but also CO2 emissions from the use of fossil fuel in agricultural production processes, is effective and essential in evaluating the effects of agricultural management practices on climate change mitigation. It is important, too, to include other green house gases（CH4 and N2O）, other environmental impacts（e.g. nitrate nitrogen in soils and water）, and impacts on agricultural productivity, in evaluation of agricultural management practices.
Forest ecosystems are expected to contribute to sequestering atmospheric CO2 as strongly related to global warming. In recent research activities on forest productivity, much effort have been made to understand carbon stocks and carbon flow in various forest ecosystems. This paper overviews recent knowledge of carbon sequestration into forest ecosystems, then discusses the role of carbon cycling in forest ecosystems. Ordinarily managed sugi（Crypromeria japonica）plantation forests in Japan generally sustain biomass carbon of about 150 ton/ha at around 100 years of age. Under preferred environmental conditions, massive forests with gigantic tree height and biomass could rarely appear. It is reported that the biggest forest in biomass carbon is 360 ton/ha in Japan, whereas 1,730 ton/ha in California, USA. Highest biomass values could be referred to the potential of forest carbon stock. In tropical rain forests, photosynthesis shows higher performances because of preferable conditions with moist and warm environment, which promotes carbon sequestration into forest biomass compared with other forest ecosystems. However, due to the higher decomposition rate, the soils in tropics show lower carbon stocks. On the contrary, although boreal forests sustain fewer carbons in biomass, the soil carbon contents exhibit higher values than tropical rain forests because of lower decomposition rate of soil organic matter under lower temperature. Evaluating carbon sequestration into forest ecosystem, carbon flows and carbon stocks in ecosystems is essential to be quantified as influenced by environmental conditions such as temperature, moisture, water and nutrient availability. In addition, we should quantitatively understand and model the ecophysiological processes in forest dynamics and carbon cycles in order to explain the variation of carbon allocation and realized carbon stocks in various forest sites.
Objective. The purpose of this paper is to review recent trends in the development of life cycle inventories（LCI）for agricultural production systems and to introduce an LCI database for agricultural production and biomass utilization in Japan called the NARO LCI database.
Results and Discussion. Agricultural production systems differ in several important respects from industrial production systems and it necessitates the introduction of special features into LCI database construction. Although several agricultural LCI databases were already developed, there are many projects for developing LCI data for agricultural production. The NARO LCI database includes inventories for agricultural crops, seeds and seedlings, fertilizers and pesticides, bioenergy, agricultural work processes, machinery and buildings, and direct field emissions.
Conclusions. The development of the LCI database for agricultural production systems will facilitate the applicability of LCA to agriculture, although attention has to be paid to how to draw appropriate comparisons for decision making through the application of LCA.
The inventory database is essential for implementing of Life Cycle Assessment（LCA）. However, the inventory data based on a process analysis isn’t fulfilling demands of LCA practitioners. Hence, we developed the inventory database（Inventory Database for Environmental Analysis: IDEA）. IDEA is covered all of products except of service activity, and IDEA collects whole of environmental load about impact categories of global warming, acidification and resource consumption. In this paper, we showed how to develop inventory data of agricultural crops in IDEA. The system boundary of inventory data included cultivation, dissemination, fertilizer application, pesticides scatter, ingathering, shipment preparations and transportation. IDEA doesn’t take account of inventory data of capital assets and fatigue uniform. And each data is presented input/output per weight of crops. The inventory data was developed by using national statistics and reports. The amounts of energy and water supply were cited from each farmer’s costs per shipping volume and the amounts of fertilizer per crop acreage were cited from each local government reports. In addition, we confirmed consistency of data. The results concluded that the application inventory data in IDEA to LCA doesn't cause major problems. As a result, we developed 83 inventory data of agricultural crops in IDEA. The data have a limitation of data quality because the data developed by using statistics and reports. Therefore, it is necessary to update data by actual survey. In addition, it is necessary to collect about the import crops in future.
The potential risks of biofuel production for food security, biodiversity and the environment are extensively debated and are thus important issues for consideration. The development of sustainability criteria for biofuel production is an important measure for increasing the positive and decreasing the negative impacts. This article showed state and trends of sustainability for biofuel production in EU, UK, USA, Japan, and international organizations etc., and problems and future perspectives. In the case of Japan, the sustainability criteria of biofuels are based on the act on the Promotion of the Use of Non-Fossil Energy Sources and Effective Use of Fossil Energy Source Materials by Energy Suppliers. Contribution to CO2 emission reductions identified by LCA, supply stability as a source of energy, and coping with competition between food and fuel are the key aspects of the Japanese sustainability criteria for biofuels. The LCA-based reduction standard set by Japan is 50%. Biodiversity, as well as environmental and social impacts needed to be considered during procurements. The criteria of 50% reduction is an obstacle for biofuel production in Japan. Supply chain management and certification system are important issues for procurement.
Objective. In this paper, we focus on the environmental administration of local government and the environmental activities of consumers. First, using the National Survey of Family Income and Expenditure for the City of Yokohama, we analyze the existing consumption activities of citizens and the associated CO2 emissions. Next, we calculated CO2 emissions by utilizing the CO2 emission factor which is equivalent to the carbon-footprint for each expense item. Finally, we estimate price elasticities for each item and simulate the effect of environmental policies, such as the promotion of organic farming, the eco-point system, and price changes for electricity and fuels. Results and Discussion. We found that different consumers react differently to such environmental policies depending on their expenditure patterns. If the information concerning carbon-footprints for various goods and items is readily available in the future, policy assessments and simulation analysis will become increasingly accurate. Conclusions. Our paper shows that the role of local government is essential in carrying out environmental policies. This especially holds true for policies affecting consumers. Local governments can ascertain the current status of individual households much better than the national government can, so they will have a more important role in creating a sustainable consumption society.
Background, Aim, and Scope. Matrix-based life cycle inventory (LCI) analysis can be effectively used to evaluate the environmental impact of a product system including closed loops (e.g. reuse and recycling). However, the matrix-based method has not yet been widely used because most life cycle assessment (LCA) practitioners find it complicated and difficult to satisfactorily construct a regular coefficient matrix from a large amount of input/output data collected from all the processes that compose a product system. The authors aim to develop a method to construct a regular coefficient matrix, which would enable the widespread use of the matrix method. The method proposed in the authors’ previous paper can be used to redescribe a product system as a geometrical figure and construct a regular coefficient matrix using graph theory. However, the method cannot be used when the geometrical figure corresponding to a product system is a non-planar graph. The objective of the present study is to improve and generalize the method so that it can be used with an arbitrary product system. Methods. First, a product system is redescribed as a geometrical figure by using the five basic components as is done in the previous paper. The redescribed geometrical figure can be expressed as a graph that consists of abstract concepts of nodes and edges in the graph theory. Then, a coefficient matrix for the product system is constructed from the constraint conditions of the product system (e.g. the balance of energy and materials). Because the coefficient matrix must be a regular matrix, the constraint conditions are required to be linearly independent of each other. A combination of linearly independent equations can be found by using a spanning tree that is constructed from the graph corresponding to the product system. A spanning tree can be constructed from every connected graph irrespective of whether the connected graph is planar or not; therefore, a regular coefficient matrix can be constructed from an arbitrary product system. Results and Discussion. A general method was developed to construct a regular coefficient matrix for an arbitrary product system based on graph theory. The validity of the developed method was demonstrated by using two simple numerical examples. The authors would like to emphasize that the developed method contributes to the generalization and the widespread use of the matrix-based LCI analysis. The generalized algorithm proposed in the present study enables us to construct a regular coefficient matrix and carry out LCI analysis using computer software. The authors plan to create such software, which would enable LCA practitioners to easily carry out the matrix-based LCI analysis without having to manually construct a coefficient matrix.
Objective. Recycling of glass from end-of-life vehicles (ELV) has been of interest since the enforcement of Law on Recycling of End-of-Life-Vehicles. The objective of this work is to investigate the environmental and economic aspects of the recycling system of glass sheets from ELV. Life cycle inventory analysis was conducted to analyze the reduction potential of CO2 emissions by recycling the grass sheets from ELV. Cash flow analysis (CFA) was applied to the recycling system, in which internal rate of return, IRR, was used as an index of the economic feasibility. Sensitivity analyses were conducted to investigate the effect of the transport distances of collected glass sheets from ELV on CO2 emissions and IRR, respectively. Results and Discussion. It was found that the reduction potential of CO2 emissions by recycling the grass sheets from ELV was 17 kg-CO2/ELV, which was mainly attributable to the reduction of CO2 emissions in production of glass sheet by the use of glass cullet and by avoidance of the treatment of automobile shredder residue (ASR). From the results of MFA by the authors reported in the previous paper, this result would be valid as long as the amount of glass cullet recovered from ELV would not exceed to 124 thousand t/year. CFA showed that the amount of inverse onerous contract, loading ratio of truck transport and collection area of glass sheets from ELV had significant effect on IRR. Conclusions. This work has proved that there is a certain reduction potential of CO2 emissions by recycling glass from ELV. The economical feasibility is significantly dependent on the amount of inverse onerous contract, loading ratio of truck transport, collection area, and prices of recovered materials, so it is recommended that stakeholders should discuss how to manage the recycling glass from ELV. This case study also shows integration of LCA, MFA and CFA is very effective when we assess environmental and economic aspects of recycling materials from end-of-life products.
Objective. This study proposes a comprehensive method for calculating transporting distance on ecoMA. Moreover, as an example of the method’s application, the study conducted a simulation of material flow that meets the fresh concrete demand in four prefectures of Kanto region and calculated CO2 emissions from the process of production and transportation. Results and Discussion. The share of CO2 emissions from transportation was 5.7% for road distance, which was 1.2% higher than when linear distance was used. It was understood that total amount of CO2 emissions from transportation is 1.3 times that of emissions when linear distance was used. Looking at the transportation of crushed stone, sand, cement (cement service station – fresh concrete factory) and cement (cement factory – cement services station), road distance was between 1.30 and 1.43 times greater than linear distance. For transportation of products other than fresh concrete, it was understood CO2 emissions for road transportation are much higher than those for linear transportation. Furthermore, for cement (cement factory – cement service station), the ratios of CO2 emissions for linear distance and road distance were large compared to crushed stone and sand, which are often transported over long distances from the suburbs to urban centers, and therefore it was understood that transportation distance caused by use of road distance depending on material types as well as geographic characteristics. Conclusions. By providing an example of ecoMA with a calculation module that can take road distance into account, this study demonstrated that it is possible to calculate CO2 emissions accurately with consideration for road distance. As a result, it has become possible to quantitatively calculate how much larger CO2 emissions are for road distance when compared to linear distance.
Objective. Environmental education is an important tool for raising awareness of sustainability and environmental issues and ultimately, changing behavior to create a sustainable society. The authors have developed a novel environmental education program using LCA (Life Cycle Assessment)software, which addresses global warming as one of the global environmental problems. This program aims to making learners (1)realize the “link” between daily life and global warming through the life cycle of consumer products (e.g. mobile phones, notebooks, pens), and (2)explore ways to reduce CO2 emissions in daily life based on life cycle thinking. The objective of the present study is to analyze the influences of the program on learners’ environmental awareness and attitude as well as their pro-environmental behavior intention. Results and Discussion. The program was implemented in three classes of second-year high school students in Kanagawa prefecture, Japan. Questionnaire surveys were conducted with 126 students to analyze the effects of the program. Pretest-posttest design was used to measure the changes in sense of the “link,” key determinants of behavioral intention (e.g. a sense of responsibility), and pro-environmental behavior intention. Pass analysis was performed using the survey data to reveal a mechanism that explains the change in pro-environmental behavior intention caused by the implementation of the program. Results of the analysis suggested that the realization of the “link” between daily life and CO2 emission based on life cycle thinking seems to increase a sense of responsibility, and then the increase mainly seems to induce the formation of or the increase in behavioral intention towards CO2 reduction. In addition, after implementing the program, another survey was conducted to collect data on students’ impression of the program. Most students answered that the use of LCA software left strong impression on them. Qualitative analysis of students’ description about the reasons why it was impressive suggested that the calculation using LCA software contributes to not only understanding life cycle thinking in general but also realizing the “link” between their own actions and CO2 emissions, and the effectiveness of their own behavioral changes. Conclusions. The environmental education program that the authors developed is effective to enhance pro-environmental behavior intention by making students realize the “link” between daily life and global warming based on life cycle thinking. Especially the use of the LCA software that is the core of the program contributes to making students realize that their own actions in daily life is closely connected to global warming.
Background and Objective. Material recycling of waste plastics is generally categorized into “closed-loop recycling”, where waste plastic products are recycled into resin material used for the same kind of products, and “open-loop recycling”, where waste plastic products are recycled into resin material used for other kinds of products. When life-cycle assessment (LCA) is applied to evaluate material recycling of waste plastics, a crucial factor is what material is actually substituted by recycled material from the investigated products: (i) virgin material, (ii) recycled material from other kinds of products, or (iii) no material at all in case recycled material is used for functions that would otherwise not be generated. The mix of materials (i)-(iii) substituted by an increased outflow of recycled material depends on how the market reacts to it. In this study, the methodology of LCA for closed-loop and open-loop recycling of waste plastics was summarized according to the substituted materials (i)-(iii) in terms of simplified system boundaries, and then a framework of LCA for material recycling of waste plastics based on market substitutability were presented. The framework was applied to a case study of material recycling of post-consumer polyethylene terephthalate (PET) bottles. Results and Discussion. The mixed share of substituted materials (i)-(iii) affected by an increased outflow of closed-loop or open-loop recycled material was formulated on the basis of the price elasticity of supply of and demand for recycled and virgin materials. The results of the case study showed that the share of open-loop recycled material which substitutes no material depended on the price elasticity of supply of and demand for non-bottle grade PET resin, and as a result, CO2 emission and fossil resource consumption of open-loop recycling could be larger than those of closed-loop recycling and incineration of post-consumer PET bottles. In addition, the uncertainty regarding the final products of open-loop recycling for which recycled PET resin were used could be important for the results of LCA based on market substitutability. Conclusions. The essential difference between closed-loop and open-loop recycling in the framework of LCA based on market substitutability lies in whether the demand for the whole material including recycled and virgin material is increased or not with an increase in the outflow of recycled material. If the demand for the material can be assumed to be constant against an increase in the outflow of closed-loop recycled material, closed-loop recycling which substitutes virgin material of the same kind has advantage over open-loop recycling which possibly substitutes no materials.