Toyohiko Nakakubo

Applying value of information methods to prioritize elements for water quality management with an example of linear alkylbenzene sulfonate in the Yodo River, Japan

Abstract Narrowing the decision space is crucial in water quality management at the meso-scale for developing countries, where a lack of data and financial budgets prevent the development of appropriate management plans and result in serious water quality degradation in many rivers. In this study, a framework for handling this task is proposed, comprising a lumped water quality model, with sensitivity and uncertainty analyses, and a management domain, including loss estimation and value of information analysis. Through a case study with linear alkylbenzene sulfonate (LAS) in the Yodo River, it is found that non-point sources and flow rate are factors that influence LAS concentration at the hot spot location. By considering the entire process of water quality management planning, we identify that the definition of the cost function of LAS treatment determines the appropriate estimation for the expected loss in reducing LAS under uncertain water quality conditions. The value of information analysis with “expected value of including uncertainty” and “expected value of perfect information” further helps estimate the benefit of including uncertainty in decision-making and the financial cost for obtaining more information regarding inputs that have been previously prioritized.

Scenario Analysis on the Impact of Diffusion of Next Generation Vehicles on Material Consumption and GHG Emissions

In this study, we developed an automobile cohort model to evaluate the effect of the diffusion of next generation vehicles such as hybrid electric vehicles and electric vehicles on material consumption and GHG emissions. This model comprises three submodels: the cohort survival submodel, the GHG emissions estimation submodel, and the material consumption estimation submodel. Comparison of three diffusion scenarios (baseline, optimistic, and pessimistic) using this model showed that more diffusion of next generation vehicles induces large material consumption while low diffusion encourages more GHG emissions.

Characterization and local practices of urban-rural symbiosis

National and local governments have begun constructing low-carbon societies by setting medium- and long-term goals for each sector of concern. Design of regional systems for circulating natural resources across urban and rural boundaries is a promising measure for decreasing greenhouse gas (GHG) emissions as well as extending co-benefits, such as pollution prevention and social development, into rural areas. However, primary sectors with weak economic bases are exempt from requirements to set GHG emission reduction targets. In addition, resource exchange between rural and urban areas is insufficient. For example, in Japan, up to a century ago, considerable amounts of night soil generated in urban areas were collected and transported to rural areas for use as fertilizer. Then agricultural products such as rice and vegetables grown with this fertilizer were consumed by people in urban areas, later becoming night soil again. However, because of urbanization and the prevalence and effectiveness of chemical fertilizer etc., this resource-circulating system fell into disuse. Urban-rural issues are also becoming important outside Japan. For example, in China the income gap between urban and rural areas has been increasing simultaneously with rapid economic growth and urbanization. Therefore, as a measure for building low-carbon societies, we should reconsider the relationship between urban and rural areas and propose plausible forms of partnership between them. For this purpose, it is necessary to model and assess these partnerships, estimate the potential reduction of GHG emissions made possible by such partnerships and describe images and visions of the desired societies that would result from them.