Tracking Construction Material over Space and Time: Prospective and Geo‐referenced Modeling of Building Stocks and Construction Material Flows

Construction material plays an increasingly important role in the environmental impacts of buildings. In order to investigate impacts of materials on a building level, we present a bottom‐up building stock model that uses three‐dimensional and geo‐referenced building data to determine volumetric information of material stocks in Swiss residential buildings. We used a probabilistic modeling approach to calculate future material flows for the individual buildings. We investigated six scenarios with different assumptions concerning per‐capita floor area, building stock turnover, and construction material. The Swiss building stock will undergo important structural changes by 2035. While this will lead to a reduced number in new constructions, material flows will increase. Total material inflow decreases by almost half while outflows double. In 2055, the total amount of material in‐ and outflows are almost equal, which represents an important opportunity to close construction material cycles. Total environmental impacts due to production and disposal of construction material remain relatively stable over time. The cumulated impact is slightly reduced for the wood‐based scenario. The scenario with more insulation material leads to slightly higher material‐related emissions. An increase in per‐capita floor area or material turnover will lead to a considerable increase in impacts. The new modeling approach overcomes the limitations of previous bottom‐up building models and allows for investigating building material flows and stocks in space and time. This supports the development of tailored strategies to reduce the material footprint and environmental impacts of buildings and settlements.     

Enabling Future Sustainability Transitions

This synthesis article presents an overview of an urban metabolism (UM) approach using mixed methods and multiple sources of data for Los Angeles, California. We examine electric energy use in buildings and greenhouse gas emissions from electricity, and calculate embedded infrastructure life cycle effects, water use and solid waste streams in an attempt to better understand the urban flows and sinks in the Los Angeles region (city and county). This quantification is being conducted to help policy‐makers better target energy conservation and efficiency programs, pinpoint best locations for distributed solar generation, and support the development of policies for greater environmental sustainability. It provides a framework to which many more UM flows can be added to create greater understanding of the study area's resource dependencies. Going forward, together with policy analysis, UM can help untangle the complex intertwined resource dependencies that cities must address as they attempt to increase their environmental sustainability.     

Urban Metabolism and the Energy Stored in Cities

Using the city of Toronto as a case study, this article examines impacts of energy stocks and flexible demand in the urban metabolism on the resilience of the city, including discussion of directions for further study of the resiliency of the urban metabolism. An important element developed is the nominal residence time of the energy stocks. This value defines how long an energy stock lasts under typical patterns of energy use. The findings suggest that the residence times of many sources of energy overcome vulnerability when energy supply shocks last on the order of hours or a few days, but that the measure is limited to assessing only certain types of commonly used energy sources in aggregate terms. Discussion is included on the uncertainty of this measure and on the metabolic and resiliency implications of new technologies intended to reduce energy use and improve sustainability of cities and the use of the urban metabolism as a means of comparison. The methodology employed highlights how waste energy could be used to increase the resiliency of the city's water supply, but also how the study of the urban metabolism would benefit from a more disaggregate form in the study of sustainable and resilient cities.     

Estimating Materials Stocked by Land‐Use Type in Historic Urban Buildings Using Spatio‐Temporal Analytical Tools

The construction industry is an important contributor to urban economic development and consumes large volumes of building material that are stocked in cities over long periods. Those stocked spaces store valuable materials that may be available for recovery in the future. Thus quantifying the urban building stock is important for managing construction materials across the building life cycle. This article develops a new approach to urban building material stock analysis (MSA) using land‐use heuristics. Our objective is to characterize buildings to understand materials stocked in place by: (1) developing, validating, and testing a new method for characterizing building stock by land‐use type and (2) quantifying building stock and determining material fractions. We conduct a spatial MSA to quantify materials within a 2.6‐square‐kilometer section of Philadelphia from 2004 to 2012. Data were collected for buildings classified by land‐use type from many sources to create maps of material stock and spatial material intensity. In the spatial MSA, the land‐use type that returned the largest footprint (by percentage) and greatest (number) of buildings were civic/institutional (42%; 147) and residential (23%; 275), respectively. The model was validated for total floor space and the absolute overall error (n = 46; 20%) in 2004 and (n = 47; 24%) in 2012. Typically, commercial and residential land‐use types returned the lowest overall error and weighted error. We present a promising alternative method for characterizing buildings in urban MSA that leverages multiple tools (geographical information systems [GIS], design codes, and building models) and test the method in historic Philadelphia.     

Maintenance and Expansion: Modeling Material Stocks and Flows for Residential Buildings and Transportation Networks in the EU25

Material stocks are an important part of the social metabolism. Owing to long service lifetimes of stocks, they not only shape resource flows during construction, but also during use, maintenance, and at the end of their useful lifetime. This makes them an important topic for sustainable development. In this work, a model of stocks and flows for nonmetallic minerals in residential buildings, roads, and railways in the EU25, from 2004 to 2009 is presented. The changing material composition of the stock is modeled using a typology of 72 residential buildings, four road and two railway types, throughout the EU25. This allows for estimating the amounts of materials in in‐use stocks of residential buildings and transportation networks, as well as input and output flows. We compare the magnitude of material demands for expansion versus those for maintenance of existing stock. Then, recycling potentials are quantitatively explored by comparing the magnitude of estimated input, waste, and recycling flows from 2004 to 2009 and in a business‐as‐usual scenario for 2020. Thereby, we assess the potential impacts of the European Waste Framework Directive, which strives for a significant increase in recycling. We find that in the EU25, consisting of highly industrialized countries, a large share of material inputs are directed at maintaining existing stocks. Proper management of existing transportation networks and residential buildings is therefore crucial for the future size of flows of nonmetallic minerals.     

Toward a low-carbon and circular building sector: Building strategies and urbanization pathways for the Netherlands

Buildings are an important part of society's environmental impacts, both in the construction and in the use phase. As the energy performance of buildings improve, construction materials become more important as a cause of environmental impact. Less attention has been given to those materials. We explore, as an alternative for conventional buildings, the use of biobased materials and circular building practices. In addition to building design, we analyze the effect of urbanization. We assess the potential to close material cycles together with the material related impact, between 2018 and 2050 in the Netherlands. Our results show a limited potential to close material cycles until 2050, as a result of slow stock turnover and growth of the building stock. At present, end-of-life recycling rates are low, further limiting circularity. Primary material demand can be lowered when shifting toward biobased or circular construction. This shift also reduces material related carbon emissions. Large-scale implementation of biobased construction, however, drastically increases land area required for wood production. Material demand differs strongly spatially and depends on the degree of urbanization. Urbanization results in higher building replacement rates, but constructed dwellings are generally small compared to scenarios with more rural developments. The approach presented in this work can be used to analyze strategies aimed at closing material cycles in the building sector and lowering buildings' embodied environmental impact, at different spatial scales.     

Energy simulation and LCA for macro-scale analysis of eco-innovations in the housing stock

Purpose

Energy consumption of buildings is one of the major drivers of environmental impacts. Life cycle assessment (LCA) may support the assessment of burdens and benefits associated to eco-innovations aiming at reducing these environmental impacts. Energy efficiency policies however typically focus on the meso- or macro-scale, while interventions are typically taken at the micro-scale. This paper presents an approach that bridges this gap by using the results of energy simulations and LCA studies at the building level to estimate the effect of micro-scale eco-innovations on the macro-scale, i.e. the housing stock in Europe.

Methods

LCA and dynamic energy simulations are integrated to accurately assess the life cycle environmental burdens and benefits of eco-innovation measures at the building level. This allows quantitatively assessing the effectiveness of these measures to lower the energy use and environmental impact of buildings. The analysis at this micro-scale focuses on 24 representative residential buildings within the EU. For the upscaling to the EU housing stock, a hybrid approach is used. The results of the micro-scale analysis are upscaled to the EU housing stock scale by adopting the eco-innovation measures to (part of) the EU building stock (bottom–up approach) and extrapolating the relative impact reduction obtained for the reference buildings to the baseline stock model. The reference buildings in the baseline stock model have been developed by European Commission-Joint Research Centre based on a statistical analysis (top–down approach) of the European housing stock. The method is used to evaluate five scenarios covering various aspects: building components (building envelope insulation), technical installations (renewable energy), user behaviour (night setback of the setpoint temperature), and a combined scenario.

Results and discussion

Results show that the proposed combination of bottom–up and top–down approaches allow accurately assessing the impact of eco-innovation measures at the macro-scale. The results indicate that a combination of policy measures is necessary to lower the environmental impacts of the building stock to a significative extent.

Conclusions

Interventions addressing energy efficiency at building level may lead to the need of a trade-off between resource efficiency and environmental impacts. LCA integrated with dynamic energy simulation may help unveiling the potential improvements and burdens associated to eco-innovations.

     

Refurbishment of office buildings in New Zealand: identifying priorities for reducing environmental impacts

Purpose

In recent years, the building sector has highlighted the importance of operational energy and efficient resource management in order to reduce the environmental impacts of buildings. However, differences in building-specific properties (building location, size, construction material, etc.) pose a major challenge in development of generic policy on buildings. The aim of this study was to investigate the relationship between energy and resource management policies, and building-specific characteristics on environmental impacts of refurbished office buildings in New Zealand.

Methods

Life Cycle Assessment (LCA) was performed for 17 office buildings operating under seven representative climatic conditions found in New Zealand. Each building was assessed under four policy scenarios: (i) business-as-usual, (ii) use of on-site photovoltaic (PV) panels, (iii) electricity supply from a renewable energy grid, and (iv) best practice construction activities adopted at site. The influence of 15 building-specific characteristics in combination with each scenario was evaluated. The study adopted regression analysis, more specifically Kruskal-Wallis and General Additive Modeling (GAM), to support interpretation of the LCA results.

Results and discussion

All the chosen policies can significantly contribute to climate change mitigation as compared to business-as-usual. However, the Kruskal-Wallis results highlight policies on increasing renewable energy sources supplying national grid electricity can substantially reduce the impacts across most environmental impact categories. Better construction practices should be prioritized over PV installation as use of on-site PV significantly increases the environmental impacts related to use of resources. The GAM results show on-site PV could be installed in low-rise buildings in regions with long sunshine hours. The results also show the strong influence of façade elements and technical equipment in determining the environmental performance of small and large buildings, respectively. In large multi-storied buildings, efficient HVAC and smaller window area are beneficial features, while in small buildings the choice of façade materials with low embodied impacts should be prioritized.

Conclusions

In general, the study highlighted the importance of policies on increasing renewable energy supply from national grid electricity to substantially reduce most of the impacts related to buildings. In addition, the study also highlighted the importance of better construction practices and building-specific characteristics to reduce the impacts related to resource use. These findings can support policy makers to prioritize strategies to improve the environmental performance of existing buildings in New Zealand and in regions with similar building construction and climate.

     

城市住宅建筑系统流量-存量动态模拟——以北京市为例

地面建筑物的累积与更新是城市化过程的结果与显性特征之一。城市建筑系统在不同层面上与外部环境系统进行着物质能量交换,对这种交互产生的资源压力与环境胁迫的关注,使其成为城市代谢研究领域中的热点问题。系统分析与模拟城市建筑物流量-存量的动态变化过程及其资源环境响应,对于揭示城市建筑系统代谢机理,提高城市总体规划精准性、强化资源系统韧性管理、提升废弃物处置效率等宏观战略具有重要意义。以北京市为例,基于Stella建模平台,构建了城市居民住宅建筑系统流量-存量的动态模拟模型,定量模拟了不同管理情景下钢材需求量与建筑拆除垃圾产生量的变化区间。结果表明:(1)基准情景下,北京住宅建筑新建流量前期增速较快,2005年达到峰值3024.1万m~2,而拆除流量约于2057年达到峰值,拆除面积为2073.14万m~2;城市住宅建筑存量最高值出现在2075年左右,面积为7.51亿m~2;(2)与基准情景相比,如果人均住宅建筑面积提高到45 m~2,从现在到模拟期结束(2019—2100)将增加钢铁需求量3251.65万t;而如果延长住宅建筑寿命至设计值,同期可减少钢铁需求量3022.9万t;(3)基准情景、大面积情景以及长寿命情景下,北京市城镇住宅建筑拆除垃圾峰值产生量分别为0.29亿t、0.39亿t、0.20亿t,政府管理部门应采取有针对性的应对措施,提前做出综合利用和处理处置方案。     

Integrating triple bottom line input–output analysis into life cycle sustainability assessment framework: the case for US buildings

Purpose

With the increasing concerns related to integration of social and economic dimensions of the sustainability into life cycle assessment (LCA), traditional LCA approach has been transformed into a new concept, which is called as life cycle sustainability assessment (LCSA). This study aims to contribute the existing LCSA framework by integrating several social and economic indicators to demonstrate the usefulness of input–output modeling on quantifying sustainability impacts. Additionally, inclusion of all indirect supply chain-related impacts provides an economy-wide analysis and a macro-level LCSA. Current research also aims to identify and outline economic, social, and environmental impacts, termed as triple bottom line (TBL), of the US residential and commercial buildings encompassing building construction, operation, and disposal phases.

Methods

To achieve this goal, TBL economic input–output based hybrid LCA model is utilized for assessing building sustainability of the US residential and commercial buildings. Residential buildings include single and multi-family structures, while medical buildings, hospitals, special care buildings, office buildings, including financial buildings, multi-merchandise shopping, beverage and food establishments, warehouses, and other commercial structures are classified as commercial buildings according to the US Department of Commerce. In this analysis, 16 macro-level sustainability assessment indicators were chosen and divided into three main categories, namely environmental, social, and economic indicators.

Results and discussion

Analysis results revealed that construction phase, electricity use, and commuting played a crucial role in much of the sustainability impact categories. The electricity use was the most dominant component of the environmental impacts with more than 50 % of greenhouse gas emissions and energy consumption through all life cycle stages of the US buildings. In addition, construction phase has the largest share in income category with 60 % of the total income generated through residential building’s life cycle. Residential buildings have higher shares in all of the sustainability impact categories due to their relatively higher economic activity and different supply chain characteristics.

Conclusions

This paper is an important attempt toward integrating the TBL perspective into LCSA framework. Policymakers can benefit from such approach and quantify macro-level environmental, economic, and social impacts of their policy implications simultaneously. Another important outcome of this study is that focusing only environmental impacts may misguide decision-makers and compromise social and economic benefits while trying to reduce environmental impacts. Hence, instead of focusing on environmental impacts only, this study filled the gap about analyzing sustainability impacts of buildings from a holistic perspective.     

Urban development and sustainability challenges chronicled by a century of construction material flows and stocks in Tiexi,China

Construction materials are considerable forces of global environmental impacts, but their dynamics vis‐à‐vis urban development are poorly documented, in part because their long lifespans require elusive and sometimes nonexistent decade‐long high‐resolution data. This study analyzes the construction material flow and stock trends that shaped and were shaped by the development, decline, and renewal of the Tiexi district of Shenyang, a microcosm of China's urban transformations since the early 20th century. Chronicling building‐by‐building the material flows and stock accumulations involved in the buildup of this area, we shed light on the physical resource context of its socioeconomic history. We find that 42 million tonnes of construction materials were needed to develop the Tiexi district from 1910 to 2018, and 18 million tonnes of material outflows were generated by end‐of‐life building demolition. However, over 55% of inflows and 93% of outflows occurred since 2002 during a complete redevelopment of the district. Only small portions of end‐of‐life materials could have been reused or recycled because of temporal and typological mismatches of supply and demand and technical limitations. Our analysis reveals a dramatic decrease in median building lifetimes to as low as 6 years in the early 21st century. These findings contribute to the discussion of long‐term environmental efficiency and sustainability of societal development through construction and reflect on the challenges of urban renewal processes not only in China but also in other developing and developed countries that lost (or may lose) their traditional economic base and restructure their urban forms. This article met the requirements for a Silver/Silver JIE data openness badge described at http://jie.click/badges .     

Anthropogenic Carbon Stock Dynamics of Pulp and Paper Products in Germany

Carbon‐based materials (CBMs) for energetic and material purposes combine biogenic and anthropogenic carbon cycles. In the latter, numerous manufactured products with various in‐use lifespans accumulate as anthropogenic carbon stocks. Understanding the behavior of these stocks is an important requirement to estimate not only future waste amounts, source for secondary raw materials, but also the impacts and effects in carbon emissions and carbon management. Previous models have estimated material stock changes; however, a lack of research in carbon stocks is perceived. Moreover, studies follow in‐use lifespan estimation approaches, such as decay functions, which do not coincide with observed consumption and waste treatment patterns. In the first part of this article, we present a carbon stock‐flow model to analyze inter‐relationships between carbon flows and stocks from raw materials to waste treatment processes considering a consumer perspective, where the dynamics of anthropogenic carbon stocks are completely described. In the second part, we study the pulp and paper industry in Germany under a scenario approach to analyze the behavior, development, and impacts of paper stocks and flows between 2010 and 2040. The model provided coherent results, with industrial data estimating 33.9 million metric tons in 2010 in paper stocks, equivalent to 410 kilograms per person. Consumption per capita and in‐use lifespan of products were identified as the most significant variables in carbon stock building. Model simulations show a sustained growth in stocks for the next 30 years, with increase in waste and carbon emissions. But in combination with recycling and reuse mechanisms and consumption patterns, environmental impacts are reduced.     

Estimates of Lost Material Stock of Buildings and Roads Due to the Great East Japan Earthquake and Tsunami

This article describes research conducted for the Japanese government in the wake of the magnitude 9.0 earthquake and tsunami that struck eastern Japan on March 11, 2011. In this study, material stock analysis (MSA) is used to examine the losses of building and infrastructure materials after this disaster. Estimates of the magnitude of material stock that has lost its social function as a result of a disaster can indicate the quantities required for reconstruction, help garner a better understanding of the volumes of waste flows generated by that disaster, and also help in the course of policy deliberations in the recovery of disaster‐stricken areas. Calculations of the lost building and road materials in the five prefectures most affected were undertaken. Analysis in this study is based on the use of geographical information systems (GIS) databases and statistics; it aims to (1) describe in spatial terms what construction materials were lost, (2) estimate the amount of infrastructure material needed to rehabilitate disaster areas, and (3) indicate the amount of lost material stock that should be taken into consideration during government policy deliberations. Our analysis concludes that the material stock losses of buildings and road infrastructure are 31.8  and 2.1 million tonnes, respectively. This research approach and the use of spatial MSA can be useful for urban planners and may also convey more appropriate information about disposal based on the work of municipalities in disaster‐afflicted areas.     

High-resolution mapping of 33 years of material stock and population growth in Germany using Earth Observation data

Global societal material stock in buildings and infrastructure have accumulated rapidly within the last decades, along with population growth. Recently, an approach for nation-wide mapping of material stock at 10 m spatial resolution, using freely available and globally consistent Earth Observation (EO) imagery, has been introduced as an alternative to cost-intensive cadastral data or broad-scale but thematically limited nighttime light-based mapping. This study assessed the potential of EO data archives to create spatially explicit time series data of material stock dynamics and their relation to population in Germany, at a spatial resolution of 30 m. We used Landsat imagery with a change-aftereffect-trend analysis to derive yearly masks of land surface change from 1985 onward. Those served as an input to an annual reverse calculation of six material stock types and building volume-based annual gridded population, based on maps for 2018. Material stocks and population in Germany grew by 13% and 4%, respectively, showing highly variable spatial patterns. We found a minimum building stock of ca. 180 t/cap across all municipalities and growth processes characterized by sprawl. A rapid growth of stocks per capita occurred in East Germany after the reunification in 1990, with increased building activity but population decline. Possible over- or underestimations of stock growth cannot be ruled out due to methodological assumptions, requiring further research.     

A bottom-up modeling of metabolism of the residential building system in China toward 2050

This study predicted the metabolic process of the residential building system in China toward 2050 by addressing the detailed provincial patterns and urban–rural disparity and the characterizing metabolisms of building materials in detail. The results show that after a rapid growth during 1980–1990, the in-use stocks of residential buildings in China are expected to slow down in around 2030, reaching 75 billion m² in 2050. Urban regions will account for 80% of total stocks, and provinces in the eastern and southern coastal areas will have the largest share. As demolition lags construction, the end-of-life residential buildings will continue to grow steadily with huge urban–rural and provincial differences, reaching 1.4 billion m² by 2050. Regarding the metabolism of building materials, the inflow of most materials will decrease after 2030, while the outflow will increase steadily toward inflow. Based on the recycling outlook of construction and demolition waste and the corresponding environmental benefit, it is indicated that under the Chinese government's ambitious planning and vigorous promotion, prior to the middle of the century, the building system has the potential to transition to a sustainable future that meets residents’ housing needs with a remarkable decreasing input of raw materials thereby notably decreasing pressures on the environment, which will significantly benefit the goal of carbon neutrality in China.     

Construction Matters: Comparing Environmental Impacts of Building Modular and Conventional Homes in the United States

Modular construction practices are used in many countries as an alternative to conventional on‐site construction for residential homes. While modular home construction has certain advantages in terms of material and time efficiency, it requires a different infrastructure than conventional home construction, and the overall environmental trade‐offs between the two methods have been unclear. This study uses life cycle assessment to quantify the environmental impacts of constructing a typical residential home using the two methods, based on data from several modular construction companies and conventional homebuilders. The study includes impacts from material production and transport, off‐site and on‐site energy use, worker transport, and waste management. For all categories considered, the average impacts of building the home are less for modular construction than for conventional construction, although these averages obscure significant variation among the individual projects and companies.     

Incorporating the impacts of climate change into infrastructure life cycle assessments: A case study of pavement service life performance

Climate change is expected to impact both the operational and structural performance of infrastructures such as roads, bridges, and buildings. However, most past life cycle assessment (LCA) studies do not consider how the operational/structural performance of infrastructure will be affected by a changing climate. The goal of this research was to develop a framework for integrating climate change impacts into LCA of infrastructure systems. To illustrate this framework, a flexible pavement case study was considered where life‐cycle environmental impacts were compared across a climate change scenario and several time horizons. The Mechanistic‐Empirical Pavement Design Guide (MEPDG) was utilized to capture the structural performance of each pavement performance scenario and performance distresses were used as inputs into a pavement LCA model that considered construction and maintenance/rehabilitation materials and activities, change in relative surface albedo, and impacts due to traffic. The results from the case study suggest that climate change will likely call for adaptive design requirements in the latter half of this century but in the near‐to‐mid term, the international roughness index (IRI) and total rutting degradation profile was very close to the historical climate run. While the inclusion of mechanistic performance models with climate change data as input introduces new uncertainties to infrastructure‐based LCA, sensitivity analyses runs were performed to better understand a comprehensive range of result outcomes. Through further infrastructure cases the framework could be streamlined to better suit specific infrastructures where only the infrastructure components with the greatest sensitivity to climate change are explicitly modeled using mechanistic‐empirical modeling routines.     

GIS‐based Analysis of Vienna's Material Stock in Buildings

The building stock is not only a huge consumer of resources (for its construction and operation), but also represents a significant source for the future supply of metallic and mineral resources. This article describes how material stocks in buildings and their spatial distribution can be analyzed on a city level. In particular, the building structure (buildings differentiated by construction period and utilization) of Vienna is analyzed by joining available geographical information systems (GIS) data from various municipal authorities. Specific material intensities for different building categories (differentiated by construction period and utilization) are generated based on multiple data sources on the material composition of different building types and combined with the data on the building structure. Utilizing these methods, the overall material stock in buildings in Vienna was calculated to be 380 million metric tonnes (t), which equals 210 t per capita (t/cap). The bulk of the material (>96%) is mineral, whereas organic materials (wood, plastics, bitumen, and so on) and metals (iron/steel, copper, aluminum, and so on) constitute a very small share, of which wood (4.0 t/cap) and steel (3.2 t/cap) are the major contributors. Besides the overall material stock, the spatial distribution of materials within the municipal area can be assessed. This research forms the basis for a resource cadaster, which provides information about gross volume, construction period, utilization, and material composition for each building in Vienna.     

Dynamic Modeling of In‐Use Cement Stocks in the United States

A dynamic substance‐flow model is developed to characterize the stocks and flows of cement utilized during the 20th century in the United States, using the generic cement life cycle as a systems boundary. The motivation for estimating historical inventories of cement stocks and flows is to provide accurate estimates of contemporary cement in‐use stocks in U.S. infrastructure and future discards to relevant stakeholders in U.S. infrastructure, such as the federal and state highway administrators, departments of transportation, public and private utilities, and the construction and cement industries. Such information will assist in planning future rehabilitation projects and better life cycle management of infrastructure systems. In the present policy environment of climate negotiations, estimates of in‐use cement infrastructure can provide insights about to what extent built environment can act as a carbon sink over its lifetime. The rate of addition of new stock, its composition, and the repair of existing stock are key determinants of infrastructure sustainability. Based upon a probability of failure approach, a dynamic stock and flow model was developed utilizing three statistical lifetime distributions—Weibull, gamma, and lognormal—for each cement end‐use. The model‐derived estimate of the “in‐use” cement stocks in the United States is in the range of 4.2 to 4.4 billion metric tons (gigatonnes, Gt). This indicates that 82% to 87% of cement utilized during the last century is still in use. On a per capita basis, this is equivalent to 14.3 to 15.0 tonnes of in‐use cement stock per person. The in‐use cement stock per capita has doubled over the last 50 years, although the rate of growth has slowed.     

Assessment of Environmental Impacts of an Aging and Stagnating Water Supply Pipeline Network

Aging urban infrastructure is a common phenomenon in industrialized countries. The urban water supply pipeline network in the city of Oslo is an example. Even as it faces increasing operational, maintenance, and management challenges, it needs to better its environmental performance by reducing, for instance, the associated greenhouse gas emissions. In this article the authors examine the environmental life cycle performance of Oslo's water supply pipelines by analyzing annual resource consumption and emissions as well as life cycle assessment (LCA) impact potentials over a period of 16 years, taking into account the production/manufacture, installation, operation, maintenance, rehabilitation, and retirement of pipelines. It is seen that the water supply pipeline network of Oslo has already reached a state of saturation on a per capita basis, that is, it is not expanding any more relative to the population it serves, and the stock is now rapidly aging. This article is part of a total urban water cycle system analysis for Oslo, and analyzes more specifically the environmental impacts from the material flows in the water distribution network, examining six environmental impact categories using the SimaPro (version 7.1.8) software, Ecoinvent database, and the CML 2001 (version 2.04) methodology. The long‐term management of stocks calls for a strong focus on cost optimization, energy efficiency, and environmental friendliness. Global warming and abiotic depletion emerge as the major impact categories from the water pipeline system, and the largest contribution is from the production and installation phases and the medium‐size pipelines in the network.