研究者詳細 - 谷川　寛樹

CO2 uptake estimation in Japan's cement lifecycle 査読有り Open Access

Sawa, D; Yamashita, N; Tanikawa, H; Daigo, I; Maruyama, I

JOURNAL OF CLEANER PRODUCTION 486 巻 2025年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Cleaner Production

Carbon dioxide (CO2) uptake by cement-containing products has attracted significant interest as an important source of CO2 absorption. This study provides an advanced estimation of CO2 uptake during the cement lifecycle in Japan by incorporating dynamic material stock-flow analysis into the model. Concrete stock-flow and CO2 uptake from 1870 to 2070 are estimated by reflecting country-specific characteristics such as concrete mix design, surface-to-volume ratio of buildings, presence or absence of coating resins and/or covering materials, and exposure climate. Annual CO2 uptake in the cement lifecycle was estimated to be 2.6 million tonnes/year in 2020, corresponding to 13.9% of CO2 emissions from calcination during cement production. Annual CO2 uptake by in-use concrete accounted for 86.8% of the total in 2020, whereas that by end-of-life concrete was relatively small throughout the estimation period. CO2 uptake is expected to increase slightly in the late 2020s, then decrease to 2.3 to 2.4 million tonnes/year by 2070. Our results were lowered by comparing those of previous studies, suggesting that the most critical aspect was affected by the local climate. The high-precision analysis highlighted the importance of integrating local climate factors, surface-to-volume ratio of structures based on the domestic design guidelines and examples, and modeling of end-of-life concrete, providing fundamental knowledge for incorporating CO2 uptake into the carbon-neutral strategy of Japanese cement industry.

DOI： 10.1016/j.jclepro.2024.144542

建築物の滞留年数の変化による将来の主要建設資材の投入量及びCO2排出量への影響評価査読有り Open Access

藤川奈々, 山下奈穂, 白川博章, 谷川寛樹

環境情報科学 53 巻 ( 4 ) 頁： 66 - 73 2024年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人環境情報科学センター

建築物や社会基盤施設などの都市構造物には大量の建設資材が投入，蓄積されており，これらの物質ストックを長期間にわたりどのように維持管理するかが脱炭素・循環型社会を実現する上で大きな課題である。本研究では，日本全国の建築物のストック・フローを推計し，建築物の滞留年数の変化による将来の主要建設資材の投入量とCO2排出量への影響を検討した。結果，本研究で設定したシナリオ条件では，現役ストックの耐用年数の延長により，2100年の主要建設資材の投入量とCO2排出量は現状の耐用年数を維持するシナリオと比較して約5割減少すると見込まれた。一方，退蔵ストックの処理の違いによるシナリオ間の差は見られなかった。

DOI： 10.11492/eis.53.4_66

Global material flows and resource productivity: The 2024 update 査読有り Open Access

Schandl, H; Marcos-Martinez, R; West, J; Miatto, A; Lutter, S; Lieber, M; Giljum, S; Lenzen, M; Li, MY; Wang, HM; Tanikawa, H; Krausmann, F; Eisenmenger, N; Fischer-Kowalski, M

JOURNAL OF INDUSTRIAL ECOLOGY 28 巻 ( 6 ) 頁： 2012 - 2031 2024年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Industrial Ecology

Accurate assessments of global primary material extraction, trade of primary materials and products, material use, waste, and emissions support the development of policies that facilitate the decoupling of economic activity, natural resource use, and related environmental impacts. Here, we quantify all crucial aspects of global and country-by-country material requirements needed to fuel economic activities, covering both territorial- and demand-based indicators. These data have been assembled by a consortium of research partners that compile the global material flow and resource productivity online database for the International Resource Panel, which contributes to the global dataset for the System of Environmental–Economic Accounting (SEEA) framework and is employed to monitor progress for the Sustainable Development Goal (SDG) indicators 8.4 and 12.2. We present the main findings of the 2024 update, including methodological improvements and result differences, and discuss the main findings and limitations. Since the last update, we have identified a slowing of global materials extraction since about 2014, a continuation of solid growth in direct trade of materials and products, persistent inequality in resource use between high- and low-income countries, and a prolonged improvement in global material productivity. The full dataset used herein can be downloaded from the Global Material Flow Database hosted by the United Nations Environment Program International Resource Panel.

DOI： 10.1111/jiec.13593

An interlinked dynamic model of timber and carbon stocks in Japan's wooden houses and plantation forests 査読有り Open Access

Yamashita, N; Fishman, T; Kayo, C; Tanikawa, H

SUSTAINABLE PRODUCTION AND CONSUMPTION 52 巻頁： 314 - 323 2024年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Sustainable Production and Consumption

Carbon absorption in growing trees is an important element of a carbon-neutral society, and the long-term storage of carbon stocks is a crucial sustainability challenge. Previous studies have focused on either live-biomass carbon stocks in plantation forests or anthropogenic carbon stocks in man-made objects. For a comprehensive nature-based climate solution, an analytical framework, dataset, and scenario setup for modeling the interrelationship between timber supply and demand are required. This study developed an interlinked material flow analysis model in which the timber demand for wooden houses is connected with timber supply from managed plantation forestry. We demonstrate the model by quantifying both live-biomass and anthropogenic carbon stocks and their potentials in Japan. We compared multiple scenario-runs of the model for wooden house demands estimated by population change with varying combinations of house types, structures, and lifespans. Our results show that carbon stocks will reach a maximum amount of 1.1 billion t-C by 2050 in a scenario of high demand for wooden detached houses with lifespan extensions. On the other hand, we also found that the aging of plantation forests and their reduced carbon-stocking capacities appear inevitable in any scenario owing to the limited demand for timber. Notably, despite the widely different settings of the various scenarios, our results exhibited narrow variances in future potential carbon storage in Japan. This can be explained by the unique population characteristics and building demographics of Japan. These counterintuitive findings highlight the need for interrelated modeling of the forestry and construction sectors. Our model and its scope are versatile and applicable to other case study areas, estimation periods, and target materials.

DOI： 10.1016/j.spc.2024.11.003

From expansion to efficiency: Machine learning-based forecasting of Japan's building material stocks under demographic declines 査読有り

Wang, L; Zhang, RR; Liu, ZW; Shirakawa, H; Tanikawa, H

SCIENCE OF THE TOTAL ENVIRONMENT 951 巻頁： 175634 2024年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Science of the Total Environment

Japan's unique demographic trajectory, marked by population decline and aging, coupled with continued urbanization, presents distinct challenges for aligning built environment capacity with resource efficiency. This study aims to investigate the historical evolution and project future scenarios of building material stock (MS) and their spatial distribution across Japan's three major metropolitan areas. Through a comprehensive material flow and stock analysis, the historical accumulation of building materials from 2009 to 2020 was quantified, revealing a dominance of concrete and an increasing overall stock. The contributions of various driving factors to changes in construction areas were explored, identifying population dynamics as the predominant influence. Leveraging shared socioeconomic pathway scenarios (SSPs), this research forecasted building floor area and MS until 2050 under five distinct SSPs. The results indicated an overall reduction across all scenarios, yet with a continued concentration in high-density urban cores. The substantial gap between the highest and lowest projected MS scenarios highlighted opportunities for material conservation and emission reductions through sustainable practices. Sustainable urban development in densely populated regions necessitates a balance between infrastructure provision and environmental conservation, while in sparsely populated areas, the focus shifts to the efficient management and utilization of vacant properties and materials to cope with the impacts of significant population declines. By offering insights into the building floor area and MS implications of Japan's demographic changes, this study underscores the necessity of sustainable urban planning and resource management strategies to navigate the challenges posed by demographic shifts, ultimately contributing to sustainable development and environmental conservation goals.

DOI： 10.1016/j.scitotenv.2024.175634

Dynamic analysis of carbon emissions from construction and demolition activities in Japan: Revealed by high-resolution 4D-GIS modeling 査読有り

PubMed

Adaptive Nighttime-Light-Based Building Stock Assessment Framework for Future Environmentally Sustainable Management 査読有り Open Access

Liu, ZW; Guo, J; Zhang, RR; Ota, Y; Nagata, S; Shirakawa, H; Tanikawa, H

REMOTE SENSING 16 巻 ( 13 ) 2024年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Remote Sensing

The accumulation of artificially built environment stock during urbanization processes has been actively involved in altering the material and energy use pattern of human societies. Therefore, an accurate assessment of built environment stock can provide insights for decision makers to implement appropriate environmentally sustainable retrofitting strategies. This study presents a building stock estimation enhancement framework (BSEEF) that leverages nighttime light (NTL) to accurately assess and spatially map building stocks. By innovatively integrating a region classification module with a hybrid region-specified self-optimization module, BSEEF adaptively enhances the estimation accuracy across diverse urban landscapes. A comparative case study of Japan demonstrated that BSEEF significantly outperformed a traditional linear regression model, with improvements ranging from 1.81% to 16.75% across different metrics used for assessment, providing more accurate building stock estimates. BSEEF enhances environment/sustainability studies by enabling precise spatial analysis of built environment stocks, offering a versatile and robust framework that adapts to technological changes and achieves superior accuracy without extensive reliance on complex datasets. These advances will make BSEEF an indispensable tool in strategic planning for urban development, promoting sustainable and resilient communities globally.

DOI： 10.3390/rs16132495

Bai, YY; Yamashita, N; Guo, J; Nagata, S; Shirakawa, H; Tanikawa, H

JOURNAL OF ENVIRONMENTAL MANAGEMENT 360 巻頁： 121099 2024年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Environmental Management

To meet the 2050 decarbonization target of the global buildings and construction sector, more attention is needed to reduce carbon emissions from construction and demolition. However, current national carbon accounting studies for these activities remain limited in spatial granularity and localized applicability. This study developed a bottom-up spatiotemporal database of carbon emissions from building construction and demolition in Japan via integrating a geographic information system-based building stock model, statistical data, and survey information. Focusing on municipal-level emissions, the Logarithmic Mean Divisia Index approach was used to decompose spatiotemporal variations and identify the contributing factors. Results indicate that carbon emissions from Japan's construction and demolition activities fell by more than 50% between 2005 and 2020, largely due to declining new/demolished-to-stock ratio, suggesting a transition to a stock-based society. Central cities' reliance on carbon-intensive buildings positively contributed to spatial variations in their construction emissions, underscoring the importance of sustainable materials and timber designs. Differences between prefectures in demolition emission intensity highlighted the strategic placement of recycling facilities in key regions to curb transportation-related emissions. Overall, these findings provided data reference for local governments to devise tailored policies for managing construction and demolition emissions.

DOI： 10.1016/j.jenvman.2024.121099

PubMed

将来の人口変化とインフラの退蔵化リスク査読有り

喜古響, 蛭田有希, 山下奈穂, 白川博章, 谷川寛樹

環境情報科学 53 巻 ( 1 ) 頁： 132 - 132 2024年4月

気候変動を考慮した洪水ハザードエリアに賦存する建築物ストックの将来推計査読有り

細川莉来, 蛭田有希, 山下奈穂, 白川博章, 谷川寛樹

環境情報科学 53 巻 ( 1 ) 頁： 121 - 121 2024年4月

Mapping and modelling global mobility infrastructure stocks, material flows and their embodied greenhouse gas emissions 査読有り Open Access

Wiedenhofer, D; Baumgart, A; Matej, S; Virag, D; Kalt, G; Lanau, M; Tingley, DD; Liu, ZW; Guo, J; Tanikawa, H; Haberl, H

JOURNAL OF CLEANER PRODUCTION 434 巻 2024年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Cleaner Production

Roads and rail-based mobility infrastructures are the basis for mobility services and underpin several Sustainable Development Goals, but also induce material use and greenhouse gas emissions. To date, no stock-flow consistent study has assessed globally accumulated stocks of mobility infrastructures, associated material flows and emissions, and their spatial patterns. We present global findings on material stocks for all roads, rail-based infrastructures, incl. tunnels and bridges, and model associated material flows and their embodied emissions for the year 2021. The stock-flow consistent model combines crowd-sourced Open Street Maps data with archetypical infrastructure designs, material compositions, assumptions on lifetimes and network growth rates, incl. uncertainty ranges. We derive spatially explicit, national-level stock estimates for 180 countries, map them at a resolution of 5 arcminutes, and derive material flows and their embodied emissions at the country-level. We find that 314 [218–403] Gt of materials (41 [28–53] tons/cap) have accumulated in global mobility infrastructure, the majority in roads as aggregates and asphalt. Stocks are unequally distributed between countries, from averages of 23 [16–30] tons/cap in low income countries, to 130 [89–164] tons/cap in high income countries. Spatial inequality of per capita stocks per area differs by orders of magnitude, from 101-104 between rural, suburban, and dense urban areas. We find that 8 [4–16] Gt/year of material flows are due to expansion and maintenance, amounting to 6 [3–10] % of global resource extraction. These translate into 0.36 [0.19–0.69] Gt CO2eq/year, or 1 [0.5–1.9] % of global GHG emissions in 2021. Approximately two-thirds of these flows result from maintenance and replacement of stocks, indicating an important lock-in of resource use due to already existing infrastructure stocks. These findings support the crucial role of improving spatial planning, limiting stock expansion and (sub-)urbanization, to achieve more sustainable resource use and mitigate climate change.

DOI： 10.1016/j.jclepro.2023.139742

循環型社会形成のための指標開発と環境・経済・社会の統合的評価

橋本征二, 近藤康之, 粟生木千佳, 谷川寛樹, 高木重定, 中西翔太郎, 谷口友莉

日本LCA学会誌 20 巻 ( 1 ) 頁： 19 - 28 2024年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：日本LCA学会

本稿は、環境研究総合推進費（JPMEERF20193002）による研究成果の概要を報告するものである。当該研究では、第 1 に、物質ライフサイクルの 6 つの断面（環境からの資源投入、生産工程への原材料投入、生産工程での原材料利用、製品の使用、使用済み製品の処理、環境への廃物廃棄）に基づいて物質フロー・ストックの指標群を提案した。主要な素材について物質フローデータベースを構築し、主要な指標を適用してその有用性を示した。第 2 に、環境・経済・社会に対する統合的な取組を評価する手法を開発した。産業連関分析に基づく手法については、これを主要な資源循環の取組に適用し、その有用性を示した。また、「循環型社会ビジネスの市場規模」指標について、新たな対象事業とその分類を提案し、推計例を示した。第 3 に、ヨーロッパの主要国で使用されている循環経済の指標をレビューし、指標のデータベースを提供するとともに、国際比較可能性の向上に向けた検討を行った。指標のデータベースには、その定義、計算方法、必要なデータが含まれる。また、日本と欧州における主要な指標の定義の違いを検証し、比較可能性を高めるために必要な措置を提案した。

DOI： 10.3370/lca.20.19

洪水ハザードエリアにおける建設資材ストック・フローの時空間分析 Open Access

細川莉来, 永田聡太, 白川博章, 谷川寛樹

土木学会論文集 80 巻 ( 26 ) 頁： n/a 2024年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人土木学会

洪水ハザードエリアの建設資材ストック・フローを把握することは，将来の洪水被害予測や洪水ハザードエリアの土地利用規制を検討する際に重要である．本研究では，日本全国で建築物一棟単位から建設資材ストックの推計を行い，洪水ハザードエリアの建設資材ストック・フローを明らかにした．結果，洪水ハザードエリア内の建設資材ストックは2003年から2020年にかけて増加しており，全国の建設資材ストックの約42%を占めていた．浸水深3m以上のハザードエリア内の低層木造建築物由来のストックは2020年に全国で1.95億トンであった．全国的にハザードエリア内外で建設資材ストックの更新率が同程度となった．洪水被害を受ける可能性の高い建設資材ストックが年々増加しており，建物立地を決定する際に洪水リスクが考慮されていない可能性が示された．

DOI： 10.2208/jscejj.24-26023

共有社会経済経路を用いた気候変動による災害廃棄物ポテンシャル量への影響評価 Open Access

平山修久, 白川博章, 山下奈穂, 谷川寛樹

土木学会論文集 80 巻 ( 26 ) 頁： n/a 2024年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人土木学会

本研究では，社会経済シナリオであるSSP（共有社会経済経路）別の洪水氾濫解析による浸水深データを用いて，気候変動と土地利用変化による災害廃棄物ポテンシャル量への影響評価を行った．その結果，気候変動によって，1981年から2000年の基準気候と比較して，2031年から2050年では1.10〜1.30，2081年から2100年では1.06〜1.43と災害廃棄物ポテンシャル量が増大しうることを示した．また，人口分布の変化による災害廃棄物ポテンシャル量への影響について分析した結果，人口減少により気候変動による災害廃棄物ポテンシャル量は減少するが，一人当たりの災害廃棄物ポテンシャル量という災害リスクは増大しうると示した．

DOI： 10.2208/jscejj.24-26002

Paving the way to the future: Mapping historical patterns and future trends of road material stock in Japan 査読有り

Zhang, RR; Yamashita, N; Liu, ZW; Guo, J; Hiruta, Y; Shirakawa, H; Tanikawa, H

SCIENCE OF THE TOTAL ENVIRONMENT 903 巻頁： 166632 - 166632 2023年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Science of the Total Environment

Roads are a fundamental component of societal infrastructure, whose decades-long lifespan has far-reaching implications for developmental decisions. The road construction and development have profound impacts on economic growth, social dynamics, and environmental sustainability. Therefore, comprehensive measurement of the current road material stock (MS) and the projection of expected future road scale based on regional socio-economic scenarios that can reflect unique local conditions are necessary. This study examined the historical changes and progression patterns of the road network across Japan from 1965 to 2020 through material flow and material stock analysis. By using the road MS time series, along with explanatory socioeconomic variables, several models including Autoregressive Integrated Moving Average with explanatory variables (ARIMAX), Support Vector Regression (SVR), hybrid ARIMAX-SVR, Multiple Linear Regression (MLR), Artificial Neural Networks (ANN), and Random Forest (RF) were compared. After comparison analysis, ARIMAX and hybrid ARIMAX-SVR models were employed to forecast expected road MS in each prefecture of Japan by 2050 based on national shared socioeconomic pathways (SSP) scenarios. The study found that the total road MS of Japan increased 5.5-fold over 55 years. Aggregate was the dominant material, comprising over 70 % among the four materials of the total road MS. The forecast results for each prefecture were classified into three different patterns. Expected MS in most prefectures still displayed increasing trends in the five scenarios, but the projection of road MS in eight prefectures revealed a notable downward trend across each SSP scenario. For most prefectures, SSP5 displayed the highest expected road MS, followed by SSP1. SSP3 was the scenario with the lowest MS. This approach provided a more thorough understanding of the likely evolution of road MS across different SSP scenarios and could help inform decisions for resource allocation and policy formulation concerning road infrastructure management.

DOI： 10.1016/j.scitotenv.2023.166632

下水道管渠を対象とした社会資本ストックの退蔵化リスク評価査読有り

山下奈穂, 松代竜毅, 蛭田有希, 白川博章, 谷川寛樹

環境情報科学論文集 ceis37 巻 ( 0 ) 頁： 70 - 77 2023年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人環境情報科学センター

<tt>近年，建築物や社会基盤施設の老朽化が課題となっており，限られた人的資源や財源によってこれら物質ストックを計画的に維持管理・更新していく必要がある。本研究では，全国の下水道管渠を例として，管渠の健全度及び人口予測に基づき将来退蔵化するリスクを検討した。推計結果から，全国の下水道管渠ストック量は</tt>2018 <tt>年に</tt>115 <tt>百万</tt>t <tt>であり，改築が必要な老朽管渠の割合はコンクリート管，塩ビ管でそれぞれ</tt>29%<tt>，</tt>13%<tt>であった。退蔵化リスクは北海道，奈良県，山口県，宮崎県，鹿児島県で高く，これらの地域では特に将来の経費回収率の低下や労働力不足を踏まえた計画的な対策が必要であると示唆された。</tt>

DOI： 10.11492/ceispapers.ceis37.0_70

都市構造物を対象とした世代間の同一性判定による建設資材ストック・フロー推計査読有り

太田裕也, 山下奈穂, 蛭田有希, 白川博章, 谷川寛樹

環境情報科学論文集 ceis37 巻 ( 0 ) 頁： 195 - 201 2023年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人環境情報科学センター

<tt>耐用年数を迎えた都市構造物や気候変動による自然災害の増加によって，都市に蓄積された物質ストックが将来大量に廃棄物として発生することが懸念される。都市構造物ストックの定量化は，将来の新規投入・排出フローの予測や今後の適切な維持管理計画を検討する上で重要な役割を果たす。本研究では，地理情報システムを活用し，日本全国の建築物と社会基盤施設の建設資材ストックを推計し，経時的な物質動態を明らかにした。</tt>2020 <tt>年の建築物の建設資材ストックは</tt>11,800 <tt>百万</tt>t<tt>，社会基盤施設は</tt>7,400 <tt>百万</tt>t <tt>と推計された。また，建築物の着工床面積は</tt>1 <tt>年あたり</tt>117 <tt>百万</tt>m2<tt>，滅失床面積は</tt>76 <tt>百万</tt>m2 <tt>であった。</tt>

DOI： 10.11492/ceispapers.ceis37.0_195