Objective. Coal has been the important primary energy in China. Coal-fired power generation stays on the significant position due to the rich coal resources. The coal flow depends on the railways and coastal shipping because energy producing and consuming regions are geographically distinct. Thus, it is necessary to reduce CO2 emission not only in generating electricity but also in coal transportation. This study is aimed to estimate CO2 emission reduction potential in coal transportation in China. Directions of coal transportation were evaluated using a geographic information system (GIS). In this study, a liner programming (LP) analysis model is used for the optimization of coal transportation for minimizing its CO2 emission and costs. We have also evaluated in the case of ultra super critical power plant (USC) as advanced thermal power generation technology. Results and Discussion. From the result of current flow, the coal transportation from the north of the inland which is a coal production region to the east of the coastal place that is a coal consuming area is supposed to be a mainstream. On the other hand, the south area that coal production is poor has a big consumption in Guangdong. Therefore, the coal has been carried from all areas except the northeast to the south area by coast transportation. South-eastern coastal regions such as Zhejiang and Guangdong have high dependency on the coastal transportation show twice higher CO2 emission in coal transportation than other regions. In the case of the optimization with the restriction on coastal transportation to reduce CO2 emission, the amount of emissions in coal transportation becomes smaller and gets to be minimum amount of 12.3 Mt-CO2 under the CO2 emission minimization analysis. Moreover, replacing USC for existing conventional thermal power plants makes the CO2 emission reductions in transportation much smaller amount, 8.1 Mt-CO2, because of not just shortening transportation distance and shift in transportation but decreasing amount of transportation due to less coal consumption of USC. Conclusions. From the results obtained by minimizing CO2 emission in transportation, the amount of CO2 emission reductions is 6.0 Mt-CO2 from the current coal transportation. The amount of CO2 emission reductions in transportation is estimated to be higher, 10.2 Mt-CO2, in case that USC is replaced for existing conventional thermal power plant with less coal consumption.
Objective and Method. The implementation of biomass projects requires sufficient assessment of environmental impacts based on life cycle thinking. Since inventory analysis, in particular for plant construction, is labor-intensive, the development of a practical method that needs little manpower is required. The objective of the present study is to explore an effective method to estimate greenhouse gas (GHG) emissions from biomass plant construction. GHG emissions for two existing biomass plants in Japan are estimated with the following these three methods: a bottom-up method using material data and two input-output (IO) methods using detailed and its aggregated cost data. The three methods are assessed from three aspects, namely, the accuracy of estimated values of GHG emissions from plant construction, the manpower for inventory analysis and the influences of the estimated value on life cycle GHG emissions. Results and Discussion. First, in terms of GHG emissions from plant construction, the estimated value of the bottom-up method was approximately 50% smaller than that of the IO method using detailed cost data. On the other hand, both the bottom-up and IO methods required large manpower for the GHG estimation. Second, the estimated value of the IO method using aggregated cost data was approximately 20% smaller than that of the IO method using detailed cost data. When the aggregated cost data was used, less manpower was required for the GHG estimation compared to the detailed cost data. Third, the influences of the differences between the two IO methods on life cycle GHG estimation were assessed. Although the manpower for the two IO methods were different as mentioned above, a significant difference in the influences on life cycle GHG estimation was not observed. Conclusions. The results show that, from a practical viewpoint, the IO method using aggregated cost data is effective to estimate GHG emissions associated with biomass plant construction. Future studies are required to develop a practical method using IO tables to assess various environmental and socio-economic impacts of biomass projects based on a life cycle approach.
Objective. The purpose of this research is to compute the CO2 emissions during the sales process of foods, and to offer information convenient for consumers. Using operating data offered by 8 stores, we calculated the CO2 emissions for each food and store from electricity and gas use, waste disposal, plastic tray production, resource waste material recycling, customer automobile use, and the amount of recyclable waste collected from customers. Results and Discussion. The main CO2 emission factors during the sales process of goods are supermarket electricity and gas use and customer automobile use. The amounts depend on the characteristics of the store in which the foods are sold, for example, the area of the store, the sales numbers per unit area, the distance from the store to the closest station, the percentage of customers from surrounding neighborhoods, average customer spend, age-group of main customers. At present the CO2 reduction effect by recycling of resource waste material is relatively small. According to our simulation analysis, electricity and gas-saving measures through energy management contributes greatly to the reduction of CO2 emitted during the sales process of goods. Conclusions. To reduce CO2 emission during sales process, it is important for the store to take measures to reduce consumption of both electricity and gas, and to control the extent of customer automobile usage. If consumers know CO2 emission factors as well as stores' managers, they can understand what they must do. It's desirable to make the information of CO2 emissions during the sales process as best we are able. This paper shows an example of such information. This research clearly shows that the operating data companies collect daily can be very useful in calculating CO2 emitted during the sales process of goods.
Objective. An extended water footprint (EWF) and an occupied water footprint (OWF) are proposed in this study as indices of water resource consumption. EWF represents the burden of water resource consumption in flow base, and has a unit of area in which the water supply equals to the subject consumption. Similarly, OWF is derived in stock base and has a unit of area multiplied by occupied time period. They are based on the concept of acceptable delay of water use, instead of fixed period such as a month and a year which is the basis of conventional water footprint. EWF and OWF enable us to analyze the sustainability of water resource consumption in higher detail, in particular in temporal variation. Similar to an ecological footprint, the regional and temporal differences in water scarcity are comparable to the total carrying capacity. In addition to being exact water footprint indices, EWFs and OWFs can be treated as impact categories in midpoint analysis of life cycle assessment (LCA), similar to land use and land occupation with the same dimensions. To evaluate the possibility of using the EWF and the OWF in the assessment of water use in agricultural production, sugarcane production for biofuel on Tokunoshima Island was examined as a case study. Results and Discussion. EWF exhibited a higher value in blue water (BW) in comparison to green water (GW). In particular, higher values were shown during the summer, when evapotranspiration was active. The EWF exceeded the actual cultivation area in some periods, and it was eight times higher at its maximum, which indicates temporal unsustainability. However, the total annual OWF was less than the actual land occupation, showing that the process can be sustainable with adequate water resource management. The corresponding value from conventional water footprint calculation showed significant variation by day, which indicates the difficulty of analyzing the daily variation in water stress using conventional methods. An analysis of all the processes of bioethanol production showed that the impact of sugarcane cultivation dominated them in terms of water resource consumption. Conclusions. The current work showed the potential of EWFs and OWFs as new indicators for analyses of water resource consumption. They are expected to be utilized as impact categories in LCA, especially in fine-grained analysis, although some challenges remain with regard to both database preparation and analysis methodologies.
Objective. Although slag produced by the sewage sludge melting process offers the advantage of reducing the final volume that must be landfilled, such recycling also presents an important disadvantage due to emission of abundant greenhouse gases. A trade-off exists in the waste management sector between the life extension of landfill sites and global warming, and appropriate solutions are required to find an appropriate balance between these factors. This study aims to evaluate the environmental impact of slag produced by the sewage sludge melting process and to investigate conditions to promote slag production under trade-off condition. Results and Discussion. This study evaluates two cases: (1) slag is produced from sewage sludge and recycled for use in construction materials, and (2) sewage sludge is incinerated and the incineration ash is landfilled. Case studies at a particular treatment plant were conducted for comparative evaluation, and environmental loads of CO2 and final disposal were targeted. CO2 emissions of 1,400 and 500 kg-CO2/tonne were determined for cases (1) and (2), respectively. Then, a comprehensive evaluation of the trade-off between the life extension of the landfill site and global warming was conducted using the distance-to-target method. The indicator value was 89% lower for case (1) than for case (2) when the reduction target of final disposal from FY2011 to FY2030 was 67%. However, this result supposes that all of the slag produced was recycled. Assuming effective utilisation of slag (68%), the difference in the final volume between the two cases would drop to 45%. A sensitivity analysis using distance-to-target method was conducted to investigate the percentage of the final disposal reduction or greenhouse gas target that would be required to revive the results of cases (1) and (2). The results indicated effective utilisation of slag has advantageous comparing with case (2). Conclusions. The present study indicates that slag produced by the sewage sludge melting process is important to address the trade-off between life extension of landfill sites and global warming. Moreover, effective utilization of slag is a key factor in determining the effectiveness of slag recycling. Therefore, finding ways to increase the effective utilization should be made a priority.