Hiroki Hondo

Sensitivity analysis of total CO2 emission intensities estimated using an input-output table

This study addresses the problem of uncertainties of total CO2 emission intensities estimated using an input-output (I-O) table for a life-cycle inventory analysis. The validity of the total CO2 emission intensities has been questioned mainly because the amounts of commodities are measured in monetary units, and because various commodities are produced in a single sector of an existing I-O table. In this study, first, a sensitivity analysis of total CO2 emission intensities estimated using the Japanese I-O table was performed to identify the elements that significantly influence the total CO2 emission intensity. If an influential element identified by sensitivity analysis varies widely, the total CO2 emission intensity is greatly influenced. Secondly, how much total CO2 emission intensities vary associated with the variation of those influential elements was evaluated. It was concluded that the evaluation of uncertainties using a stochastic approach as well as the improvement of accuracy by disaggregating the original I-O sectors, focusing on influential elements, are important.

Derivation of energy-embodiment functions to estimate the embodied energy from the material content

The embodied energy includes the direct and indirect energy consumed for the entire production process. These values are needed to estimate impacts on energy consumption due to changes in consumption patterns. We have developed a model of the economic system to account for every production process. This model illustrates interrelations among production processes by incorporating sectors that produce multiple products. The model is consistent with available input-output coefficients and the material flow in each process. By exploring our model, we derived energy-embodiment functions that evaluate the embodied energy of an arbitrary product in terms of material content.

Energy analysis and carbon dioxide emission of tokamak fusion power reactors

Energy gain and carbon dioxide (CO 2 ) emission of tokamak fusion power reactors are evaluated in this study compared with other reactor types, structural materials, and other Japanese energy sources currently in use. The reactors treated in this study are (1) a conventional physics performance international thermonuclear experimental reactor (ITER), like a reactor based upon the ITER engineering design activity (ITER-EDA), (2) a RS (reversed shear) reactor using the reversed shear safety-factor/plasma current profile, and (3) a ST (spherical torus) reactor based upon the final version of the advanced reactor innovative engineering study ST (ARIES-ST). The input energy and CO 2 emission from these reactors are calculated by multiplying the weight or cost of the fusion reactor components by the energy intensity and/or with the CO 2 intensity data, which are updated as often as possible. The ITER cost estimation is estimated based on the component unit costs. The following results were obtained: (1) The RS and the ST reactor can double the energy gain and reduce CO 2 emission by one-half compared with the ITER-like reactor. (2) Silicon carbide (SiC) used as the structural material of inner vessel components is best for energy gain and CO 2 emission reduction. (3) The ITER-like reactor is slightly superior to a photovoltaic (PV) with regard to CO 2 emission. (4) The energy gain and CO 2 emission intensity of the RS reactor and the ST reactor are as excellent as those of a fission reactor and a hydro-powered generator. These results indicate that a tokamak fusion power reactor can be one of the most effective power-generating technologies both in high-energy payback gains and reduction of CO 2 .

Estimating the embodied carbon emissions from the material content

The embodied carbon emissions includes the direct and indirect carbon emitted for the entire production process. These values are needed to estimate impacts on carbon emissions due to changes in consumption patterns. We have developed a model of the economic system to account for every production process. This model illustrates interrelations among production processes by incorporating sectors that produce multiple products. At each multiple product-producing sector, inputs differ in accordance with the material content of the output product. The model is consistent with available input-output coefficients and the physical law of material flow in each process. By exploring our model, we derived carbon embodiment functions that evaluate the embodied carbon emissions of an arbitrary product in terms of material content. Empirical analysis has been fulfilled using the available 405-sector input-output table of Japan.

The Effect of Local Biomass Projects on Energy Balance and GHG Emission: A Life Cycle Approach

Emerging attention has been given to the use of biomass in local areas for its contribution to reducing fossil fuel dependence and mitigating global warming. The objective of the present study is to develop a method that quantitatively assesses the effects of local biomass projects on fossil fuel consumption and greenhouse gas (GHG) emission. A practical method based on a life cycle approach is proposed and applied to a case of bioethanol project in Miyako Islands of Japan. The project is aiming to produce bioethanol from molasses within the islands, and to replace the entire gasoline consumed in the islands to E3 fuel (i.e., a mixture of 3% ethanol and 97% gasoline by volume). The assessment using the developed method revealed that, first, the complete shift from gasoline to E3 fuel allows for decreases in fossil fuel consumption and GHG emission. Second, the performance of the project is improved by the integration of the ethanol plant and the sugar factory. Moreover, the assessment found that, in small-scale bioethanol projects, the contribution of capital goods to life cycle fuel consumption and GHG emission is not negligible.

Comparative analysis of embodied liabilities using an inter-industrial process model: gasoline- vs. electro-powered vehicles

We developed a model of economy-wide production systems by incorporating a material balance concept into the standard input-output framework. This inter-industrial process model represents the physical flow of materials throughout the industrial network and thus is able to address the entire process involved with the production of a target product according to its material content. The model, which is based on some physically allowable assumptions, was calibrated using the available input-output coefficients for aggregated processes (sectors). We used detailed data on environmentally hazardous emissions and labour requirements for each sector to analyse the liabilities of substitutable products in terms of different factors, origins, and stages of the inter-industrial process network. To empirically examine the model, we applied it to analyse the production of a popular gasoline-powered vehicle and an electro-powered vehicle.

Implementation and Effect of PV-familiarizing Activity in Elementary School in Yokohama City

The present article describes the implementation and effect of school activities that help children get close to photovoltaic (PV) systems in their elementary school, named the “PV-familiarizing activity.” This activity is composed of the following two actions. First, children observe and touch PV panels at their school. Next, for a certain period, they in turn clean PV panels and record the amount of electricity generated by the PV system at their school. The PV-familiarizing activity was implemented in three elementary schools in Yokohama city, Japan. To examine the effect of the PV-familiarizing activity on the school children, questionnaire and interview surveys were conducted to measure changes in emotional affinity to PV system of their school, environmental concern, electricity-saving behavior and so on. The survey results reveal that the PV-familiarizing activity can assist the school children in feeling attachment to the PV system of their school and seeing it as a symbol of their school. In addition, the school children may more strongly feel the importance of electricity, and increase environmental concern and electricity-saving behavior after the PV-familiarizing activity. It is conjectured that the PV-familiarizing activity helps the school children consider global issues of energy and environment as their own problems.