Faculty Profiles - TANIKAWA, Hiroki

MATERIAL STOCK AND FLOW ESTIMATION BY IDENTIFYING ROAD INFRASTRUCTURE BETWEEN GENERATIONS IN AICHI PREFECTURE Open Access

KIKO Hibiki, HASEGAWA Masatoshi, SHIRAKAWA Hiroaki, TANIKAWA Hiroki

Japanese Journal of JSCE Vol. 81 ( 26 ) page： n/a 2025

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

The recycling rates of construction by-products such as concrete debris and asphalt concrete debris have steadily improved due to efforts toward establishing a sound material-cycle society and introduction of laws. However, the actual use of recycled materials, primarily within road infrastructure, has only been estimated at the municipal level. As Japan faces an accelerating population decline, the supply-demand balance of recycled materials is expected to fluctuate significantly. Therefore, examining this balance from a spatial perspective is critically important for maintaining a sound material-cycle society. In this study, we developed a method for identifying road segments and estimating the amount of construction materials input into road infrastructure, with the aim of laying the groundwork for clarifying the spatial supply-demand balance. As a result, the estimated construction material input showed consistency with statistical data, indicating that the approach is effective for capturing the spatial distribution and trends of material usage. However, the restricted scope of estimation targets and challenges in validity assessment remain, which constitutes a limitation of the proposed method.

DOI： 10.2208/jscejj.25-26008

SPATIAL ANALYSIS OF CLIMATE CHANGE ADAPTATION MEASURES USING FLOOD RISK AND BUILDING RENEWAL SCENARIOS Open Access

OKADA Hiroto, HASEGAWA Masatoshi, SHIRAKAWA Hiroaki, TANIKAWA Hiroki

Japanese Journal of JSCE Vol. 81 ( 26 ) page： n/a 2025

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

The importance of watershed flood control is increasing due to the frequency of extreme events caused by climate change. In this study, the amount of damage caused by floods to houses, the amount of river channel excavation, and the percentage of wooden houses rebuilt were estimated and spatially analyzed for all of Japan, and the feasibility of adaptation measures was examined. The results show that the damage to houses by floods is estimated to be about 180 trillion yen in the base climate, about 194 trillion yen in the SSP1-2.6 climate and about 212 trillion yen in the SSP5-8.5 climate in the future climate, indicating an increasing trend of damage in the future. The possibility of introducing a pilotis structure for the reconstruction of detached wooden houses is about 24% in the case of SSP1 and about 26% in the case of SSP5 in 2050. In urban areas, the rebuilding of houses with large damage is likely to proceed, making it easy to implement countermeasures, while in non-urban areas, rebuilding may not proceed even if damage is large, delaying the implementation of countermeasures.

DOI： 10.2208/jscejj.25-26004

Assessment of theResearch Paper Impact on Future Construction Material Inflow and CO2 Emissions due to Changes in the Retention Time of Buildings Reviewed Open Access

FUJIKAWA Nana, YAMASHITA Naho, SHIRAKAWA Hiroaki, TANIKAWA Hiroki

Environmental Information Science Vol. 53 ( 4 ) page： 66 - 73 2024.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Center for Environmental Information Science

Buildings and infrastructures require a large amount of construction materials and the strategic management of those material stock accumulated in urban structures is very important to realize decarbonized society and material-cycle society. This study aims to estimate the amount of material stock and flow of buildings in the entire Japan and evaluate the impact of lifespan extension of buildings on the future material circulation and CO2 emissions. As results, it was found that the scenario expecting the lifespan extension of in-use stocks, the amount of CO2 emissions in 2100 will be reduced by about 50% compared with the scenario which keeps the current lifespan of buildings. On the other hand, there were no differences among scenarios due to the management of the obsolete stock.

DOI： 10.11492/eis.53.4_66

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

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

SUSTAINABLE PRODUCTION AND CONSUMPTION Vol. 52 page： 314 - 323 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Global material flows and resource productivity: The 2024 update Reviewed

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 Vol. 28 ( 6 ) page： 2012 - 2031 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：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

From expansion to efficiency: Machine learning-based forecasting of Japan's building material stocks under demographic declines Reviewed International coauthorship

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

SCIENCE OF THE TOTAL ENVIRONMENT Vol. 951 page： 175634 - 175634 2024.11

Language：English Publishing type：Research paper (scientific journal) Publisher：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

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

Zhiwei Liu, Jing Guo, Ruirui Zhang, Yuya Ota, Sota Nagata, Hiroaki Shirakawa, Hiroki Tanikawa

Remote Sensing Vol. 16 ( 13 ) 2024.7

Dynamic analysis of carbon emissions from construction and demolition activities in Japan: Revealed by high-resolution 4D-GIS modeling Reviewed International coauthorship

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

JOURNAL OF ENVIRONMENTAL MANAGEMENT Vol. 360 page： 121099 - 121099 2024.6

Language：English Publishing type：Research paper (scientific journal) Publisher：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

将来の人口変化とインフラの退蔵化リスク Reviewed Open Access

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 Vol. 53 ( 1 ) page： 132 - 132 2024.4

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 Reviewed Open Access

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 Vol. 53 ( 1 ) page： 121 - 121 2024.4

Mapping and modelling global mobility infrastructure stocks, material flows and their embodied greenhouse gas emissions Reviewed 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 Vol. 434 2024.1

Language：English Publishing type：Research paper (scientific journal) Publisher：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 CO<inf>2</inf>eq/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

Indicator Development and Integrated Assessment of Environmental, Economic, and Social Aspects for Establishing a Sound Material-cycle Society Open Access

HASHIMOTO Seiji, KONDO Yasushi, AOKI-SUZUKI Chika, TANIKAWA Hiroki, TAKAGI Shigesada, NAKANISHI Shotaro, TANIGUCHI Yuri

Journal of Life Cycle Assessment, Japan Vol. 20 ( 1 ) page： 19 - 28 2024

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Institute of Life Cycle Assessment, Japan

This article provides a summay of research supported by Environment Research and Technology Development Fund (JPMEERF20193002). First, the study proposed a group of material flow and stock indicators based on six cross-sections of material life cycle: resource input from the environment, raw material input to production processes, raw material utilization in production processes, product use, end-of-life product treatment, and waste emissions to the environment. After material flow database were developed for major materials, the proposed indicators were applied to demonstrate their usefulness. Second, the study developed methodologies to evaluate integrated efforts for the environment, economy, and society. As for a methodology based on input-output analysis, it was applied to major resource recycling efforts to demonstrate its usefulness. As for an indicator "market size of business for a Sound Material-cycle Society," the study proposed the new target business and its classification with the trial estimations. Third, the circular economy indicators used in the major European countries were reviewed to provide a database of indicators and discuss improvement in international comparability. The indicator database includes definitions, calculation methods, and necessary data. Differences in the definitions of major indicators in Japan and Europe were examined and necessary measures to improve comparability were proposed.

DOI： 10.3370/lca.20.19

IMPACT ASSESSMENT OF CLIMATE CHANGE ON DISASTER DEBRIS POTENTIAL USING SHARED SOCIOECONOMIC PATHWAYS Open Access

HIRAYAMA Nagahisa, SHIRAKAWA Hiroaki, YAMASHITA Naho, TANIKAWA Hiroki

Japanese Journal of JSCE Vol. 80 ( 26 ) page： n/a 2024

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

In this study, the impact of climate change and land use change on disaster debris potential was assessed using inundation depth data from flood inundation analysis by socioeconomic scenario, SSP (Shared Socioeconomic Pathway). As a result, it was pointed out that climate change can increase the amount of disaster debris potential from 1.10 to 1.30 in 2031 to 2050 and from 1.06 to 1.43 in 2081 to 2100, compared to the 1981 to 2000 base climate. The effect of population distribution on the amount of disaster debris potential was analyzed, and it was indicated that the amount of disaster debris potential due to climate change decreases due to population decrease, however, the disaster risk in terms of the amount of disaster debris per capita can increase.

DOI： 10.2208/jscejj.24-26002

Spatiotemporal Analysis of Material Stock and Flow on Construction Sector in Flood Hazard Areas Open Access

HOSOKAWA Riko, NAGATA Sota, SHIRAKAWA Hiroaki, TANIKAWA Hiroki

Japanese Journal of JSCE Vol. 80 ( 26 ) page： n/a 2024

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japan Society of Civil Engineers

Understanding the stock and flow on construction sector in flood hazard areas is important for assessing future flood damage and considering land use regulations in flood hazard areas. This study estimated material stock and flow on construction sector at the individual building level and revealed the trends in flood hazard areas. As a result, the building stock in flood hazard areas increased from 2003 to 2020, accounting for approximately 42% of the total national building stock. Especially, the stock of non-durable low-rise wooden buildings in hazard areas with flooding depth of over 3 meters had reached over 195 million tons nationwide by 2020. It was evident that the stock turnover rate is similar both inside and outside flood hazard areas, indicating that buildings have been constructed without considering flood risk.

DOI： 10.2208/jscejj.24-26023

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

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

山下奈穂, 白川博章, 谷川寛樹

環境情報科学論文集 Vol. 53(4) page： 66 - 73 2024

Ruirui Zhang, Naho Yamashita, Zhiwei Liu, Jing Guo, Yuki Hiruta, Hiroaki Shirakawa, Hiroki Tanikawa

Science of The Total Environment Vol. 903 page： 166632 - 166632 2023.12

Obsolescence Risk Assessment of Infrastructure Stocks: A Case Study of Japan's Sewer Pipes Reviewed Open Access

YAMASHITA Naho, MATSUSHIRO Tatsuki, HIRUTA Yuki, SHIRAKAWA Hiroaki, TANIKAWA Hiroki

Papers on Environmental Information Science Vol. ceis37 ( 0 ) page： 70 - 77 2023.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Center for Environmental Information Science

The aging of urban structures such as buildings and infrastructures has been getting serious in these years. Those material stocks should be appropriately maintained for a long period of time, however, budget constraints and labor shortage due to population decline seem to make the situation more difficult. This study aims to estimate the amount of Japan's sewer pipe stock and compare the obsolescence risk with combinations of soundness of the existing stock and population forecast among prefectures. As results, the amount of sewer pipe stock was estimated to be 115 million t in 2018, and the rates of aged stock requiring urgent maintenance were 29% for concrete pipes and 13% for PVC pipes, respectively. Obsolescence risk was high in Hokkaido, Nara, Yamaguchi, Miyazaki and Kagoshima, indicating that those especially need deliberate countermeasures for a long-term stock management.

DOI： 10.11492/ceispapers.ceis37.0_70

Material Stock and Flow Estimation by Identifying the Congruency of Urban Structures between Generations Reviewed Open Access

OTA Yuya, YAMASHITA Naho, HIRUTA Yuki, SHIRAKAWA Hiroaki, TANIKAWA Hiroki

Papers on Environmental Information Science Vol. ceis37 ( 0 ) page： 195 - 201 2023.12

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Center for Environmental Information Science

The accumulation of material stocks within cities raises concerns about the potential future generation of a significant volume of waste. That is caused by the aging of urban structures and the increasing occurrence of natural disasters caused by climate change. Quantifying urban structures stock plays an imperative role in predicting future inflows and outflows, as well as formulating appropriate maintenance and management plans. In this study, Geographic Information System (GIS) was utilized to estimate and reveal the spatiotemporal dynamics of construction material stocks in buildings and infrastructures across Japan. The estimated material stock in buildings was 11,800 million tons, while infrastructure accounted for 7,400 million tons in 2020. Moreover, the newly constructed floor area of buildings in a year was 117 million square meters, with 76 million square meters of demolished floor area over the period from 2016 to 2020.

DOI： 10.11492/ceispapers.ceis37.0_195

Sustainable assessment and resource recycling opportunities identification for China's pig industry: Integrating environmental, economic and social perspectives Reviewed

Bai, YY; Zhai, YJ; Zhang, TZ; Ren, K; Jia, YK; Zhou, XY; Cheng, ZY; Tanikawa, H; Hong, JL

SUSTAINABLE PRODUCTION AND CONSUMPTION Vol. 39 page： 425 - 437 2023.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Sustainable Production and Consumption

Livestock plays a vital role in the livelihoods and nutritional security of people worldwide and leads to significant environmental challenges. Manure management is a major hurdle for sustainable livestock development and serves as a critical source of natural fertilizer and green energy. Given that pork accounts for the highest meat production and consumption share, this study systematically evaluates China's pig production and main manure resource utilization scenarios from life-cycle environmental, economic, and social perspectives. Results show that China's pig production poses considerable potential environmental risks, primarily in the categories of fossil depletion, freshwater ecotoxicity, particulates formation, global warming, and water depletion. Feed production coupled with traditional manure treatment scenario contributes to 94.4 %–98.4 % of the key environmental impact categories and socioeconomic impact, with 32.0 % to 38.3 % of the economic costs also stemming from feed costs. In the energy utilization scenario, the potential benefits of fossil depletion and global warming categories resulting from the replacement of synthetic fertilizers with manure-based organic fertilizers in the traditional pig manure treatment scenario could be expanded by 89.6 % and 39.2 %, respectively. China's pig production contributed 0.72 % of the national carbon emissions in 2020. Fully utilizing energy potential and organic fertilizer from pig manure would achieve 0.63 % of national carbon reduction potential, as well as an economic benefit of $1.45 × 1012 and a social benefit of $8.89 × 109. Precision feeding technology, rebuilding the spatial connection between pig farms and arable land, and internalizing external costs were recommended to ensure the sustainable development of China's pig industry.

DOI： 10.1016/j.spc.2023.05.018