サステイナビリティ評価へ向けた環境影響と社会影響の分析-日本のリン肥料におけるリン鉱石とリサイクルリンの比較

学位の種別: 課程博士審査委員会委員 : （主査）東京大学准教授 小貫 元治, 東京大学教授 味埜 俊, 東京大学准教授 井原 智彦, 東京大学特任准教授 Miguel Esteban, 東北大学教授 松八重 一代University of Tokyo(東京大学

Incorporating External Effects into Project Sustainability Assessments: The Case of a Green Campus Initiative Based on a Solar PV System

We demonstrated that a green campus initiative can reduce the carbon footprint of a university and improve the disaster resilience of the local community. A project sustainability assessment framework was structured to support the initiative. First, an on-campus solar photovoltaic (PV) system was designed. The project performance in terms of financial cost and greenhouse gas (GHG) emissions was assessed using life cycle cost analysis (LCC) and a life cycle assessment (LCA), respectively. Then, we explored the incorporation of positive social impacts on the local community in the context of natural disaster-prone Japan. Indicators for improving the disaster resilience of the residents were defined based on the Sendai Framework. Our results showed that the proposed solar PV system could provide an electricity self-sufficiency rate of 31% for the campus. Greenhouse gas emissions of 0.0811 kg CO2-eq/kWh would decrease the annual emissions from campus electricity use by 27%. Considering the substituted daytime electricity purchase, a payback period of 12.9 years was achievable. This solar PV system could serve as an emergency power source to 4666–8454 nearby residents and 8532 smart city residents. This external effect would encourage stakeholders like local government and developers to participate in the project

Support Phosphorus Recycling Policy with Social Life Cycle Assessment: A Case of Japan

Producing phosphorus (P) fertilizers with recycled P is desirable for efficient use of P resource. However, the current cost of P recycling facilities in Japan strongly discourages the government from adopting this practice. To expand consideration for a P recycling policy, the concept of social externality was introduced. Social issues, such as the violation of human rights in P mining in the Western Sahara, have been identified in recent studies; nevertheless, a systematic approach towards accountability was lacking. Therefore, the purpose of this study was to support a P recycling policy with a social life cycle assessment (SLCA) by contrasting the social impacts associated with mineral and recycled P fertilizers using the case study of Japan. We developed a framework based on the UNEP-SETAC SLCA Guidelines with a supplementary set of P-specific social indicators. The results showed that the marginal social impact associated with recycled P was much less relative to mineral P; however, even if we factored in the maximum recycling capacity, a mandate of P recycling policy in Japan would not mitigate the impacts significantly relative to the current situation because only 15% of P rocks could be substituted. In short, we showed that a semi-quantitative SLCA framework would be useful to communicate the wide spectrum of social impacts to policymakers

Experiential Knowledge Complements an LCA-Based Decision Support Framework

A shrimp farmer in Taiwan practices innovation through trial-and-error for better income and a better environment, but such farmer-based innovation sometimes fails because the biological mechanism is unclear. Systematic field experimentation and laboratory research are often too costly, and simulating ground conditions is often too challenging. To solve this dilemma, we propose a decision support framework that explicitly utilizes farmer experiential knowledge through a participatory approach to alternatively estimate prospective change in shrimp farming productivity, and to co-design options for improvement. Data obtained from the farmer enable us to quantitatively analyze the production cost and greenhouse gas (GHG) emission with a life cycle assessment (LCA) methodology. We used semi-quantitative graphical representations of indifference curves and mixing triangles to compare and show better options for the farmer. Our results empower the farmer to make decisions more systematically and reliably based on the frequency of heterotrophic bacteria application and the revision of feed input. We argue that experiential knowledge may be less accurate due to its dependence on varying levels of farmer experience, but this knowledge is a reasonable alternative for immediate decision-making. More importantly, our developed framework advances the scope of LCA application to support practically important yet scientifically uncertain cases

Removal and simultaneous reduction of Cr(VI) by organo-Fe(III) composites produced during coprecipitation and coagulation processes

Composites formed during the coprecipitation and/or coagulation of ubiquitous dissolved organic matter (DOM) and Fe in natural and waste water systems might be potential scavengers for Cr(VI) in terms of sorption and reduction. Our objective here was to determine sorption and simultaneous reduction of Cr(VI) on organo-Fe(III) composites (OFC) in relation coprecipitated pH and C/(C + Fe) ratios. Results showed the greatest Cr sorption of 51.8 mg g−1 on the OFC sample that was precipitated at pH 3 and contained the C/(C + Fe) molar ratio of 0.71. Wherein the Cr(VI) removal subsequent to the coprecipitation was dominated by the sorption on Fe hydroxides. Although amounts of total sorbed Cr decreased with increasing C/(C + Fe) molar ratio, the reverse trend on Cr(VI) reducibility compensated the Cr(VI) removal capability of OFC samples. With C/(C + Fe) molar ratios ≥ 0.89, the increasing amounts of coprecipitated organic matter that homogeneously distributed with Fe domains on OFC surfaces could trigger a significantly pronounced Cr reduction. Collectively, our results suggested an alternative method for Cr(VI) remediation by manipulating C/Fe ratios in suspensions. After the sorption of most Cr(VI) on Fe hydroxides, increasing C/Fe ratio in systems could further improve the Cr(VI) removal efficiency by the reduction of remaining Cr(VI) to Cr(III)

Redox reactions between chromium(VI) and hydroquinone: Alternative pathways for polymerization of organic molecules

Chromium (VI) reduction by organic compounds is one of the major pathways to alleviate the toxicity and mobility of Cr(VI) in the environment. However, oxidative products of organic molecules receive less scientific concerns. In this study, hydroquinone (H2Q) was used as a representative organic compound to determine the redox reactions with Cr(VI) and the concomitant oxidative products. Spectroscopic analyses showed that Cr(III) hydroxides dominated the precipitates produced during redox reactions of Cr(VI) and H2Q. For the separated filtrates, the acidification induced the oxidative polymerization of organic molecules, accompanied with the complexation with Cr(III). The aromatic domains dominated the chemical structures of the black and fluffy organic polymers, which was different to the natural humic acids due to the shortage of aliphatic chains. Results of linear combination fitting (LCF) for Cr Kedge X-ray absorption near edge structure (XANES) spectra demonstrated that up to 90.4% of Cr inventory in precipitates derived after the acidification of filtrates was Cr(III) complexed with humic-like polymers, suggesting that Cr(III) possibly acted as a linkage among organic molecules during the polymerization processes of H2Q. This study demonstrated that Cr(VI) may lead to the polymerization of organic molecules in an acidic solution, and thus, it could raise scientific awareness that the oxidative decomposition of organic molecules may not be the only pathway while interacting with the strong oxidant of Cr(VI)

Capacity and recycling of polyoxometalate applied in As(III) oxidation by Fe(II)-Amended zero-valent aluminum

Arsenic remediation is often initiated by oxidizing As(III) to As(V) to alleviate its toxicity and mobility. Due to the easy availability, zero-valent Al (ZVAl) like Al can was considered as potential alternatives to facilitate As(III) oxidation. This study determined the capability and recycling of polyoxometalate (POM) to catalyze As(III) oxidation in Fe(II)-amended ZVAl systems. POM acquired electrons from ZVAl more effectively at pH 1 than at pH 2. While 76% of the reduced POM [POM(e-)] reacted with O2(g) to generate H2O2 at pH 1, only 60% of POM(e-) was used to produce H2O2 at pH 2. The remaining POM(e-) was oxidized by the generated H2O2. Such additional consumption of POM(e-) and H2O2 led to the incomplete As(III) oxidation in the system without residual ZVAl and emphasized the need for a continuous electron supply from ZVAl to compensate the depletion of POM(e-). After the hydrolyzation at pH 6.0, the XANES data evidenced that not only As(V) but WO4 released from the POM retained on surfaces of Al/Fe hydroxides. The competition for sorption sites on Al/Fe hydroxides between As(V) and WO4 led to the incomplete As removal. Despite the loss of WO4, the POM re-polymerized at pH 1 still showed the comparable capability to catalyze As(III) oxidation with original POM. This study revealed electron transfer pathways from ZVAl to As(III) as catalyzed by POM and evidenced the effective POM recycling after As removal, which lowers the cost of POM application and turns the ZVAl/Fe(II)/POM/O2 system into a practical strategy for As remediation

Adsorption of tetracycline on Fe (hydr)oxides: effects of pH and metal cation (Cu2+, Zn2+ and Al3+) addition in various molar ratios

Iron (Fe) (hydr)oxides control the mobility and bioavailability of tetracycline (TC) in waters and soils. Adsorption of TC on Fe (hydr)oxides is greatly affected by polyvalent metals; however, impacts of molar metal/TC ratios on TC adsorptive behaviours on Fe (hydr)oxides remain unclear. Results showed that maximum TC adsorption on ferrihydrite and goethite occurred at pH 5-6. Such TC adsorption was generally promoted by the addition of Cu2+, Zn2+ and Al3+. The greatest increase in TC adsorption was found in the system with molar Cu/TC ratio of 3 due to the formation of Fe hydr(oxide)-Cu-TC ternary complexes. Functional groups on TC that were responsible for the complexation with Cu2+shifted from phenolic diketone groups at Cu/TC molar ratio  1 as excess Al3+ led to the competitive adsorption with Al/TC complexes. For the Zn2+ addition, no significant correlation was found between TC adsorption capacity and molar Zn/TC ratios