Integrating lifecycle assessment and urban metabolism at city level: Comparison between Spanish cities

Urban systems are important consumers of resources and producers of wastes derived from the lifestyles and daily needs of their citizens. The quantification of environmental impacts arising from urban metabolism (UM) plays a key role in the design of more sustainable cities and in the development of decision‐making strategies into more effective urban policies. This article combines UM and lifecycle assessment methodology to quantify mass and energy flows within the city limits and derived urban environmental pressures, thus prioritizing the environmental perspective of sustainability. This methodology is applied to the two very different Spanish cities of Bilbao and Seville. The results acquired in this study identify the consumption of construction materials, electricity, fossil fuels, and food and beverages as environmental hotspots. The results are primarily affected by differences in the climate (extreme conditions), which mainly affect the consumption of fossil fuels, and differences in purchasing power, which mainly influence the intake of foodstuffs. Further research should focus on data management and quality as well as on designing more efficient cities (e.g., through the introduction of more energy‐efficient buildings, sustainable building materials, and public transport) in order to create improvements in their environmental profiles.     

城市与区域生态关联研究进展

城市及其周边区域正在面临日益严峻的环境污染、生态恶化、资源短缺等问题。这些问题的出现,与长期以来城市发展过程中忽视城市与区域的生态关联密切相关。研究城市与区域的生态关联,对于解决城市与区域的生态环境问题、指导新型城镇化建设具有重要的理论意义与实践价值。主要从以下3个方面系统总结了城市与区域生态关联的研究进展:(1)城市发展对周边区域的生态环境影响,包括直接的胁迫和间接的影响;(2)区域对城市发展的生态支撑;(3)城市与周边区域社会、经济、生态关联的相互作用机制。指出了当前城市与区域生态关联研究中存在的问题和不足:1)城市对周边区域生态环境直接影响的研究较多,且多侧重城市对周边区域的负面影响,对其间接影响的研究较为缺乏;2)周边区域对城市发展生态支撑作用的研究相对缺乏、认识不够深入;3)对城市与周边区域生态关联作用机制的研究较为缺乏。未来的研究要将城市和区域作为统一整体,进一步完善城市与区域生态关联的理论框架,耦合社会经济的相互作用,定量解析城市与区域的生态关联,为城市与区域的可持续发展提供科学依据。     

Drivers of urban metabolism: Toward a framework for urban transformations

The environmental and social crises in cities call for radical future visions that can incite transformative change. Yet, urban metabolism research typically adopts an explanatory, retrospective approach to the drivers of urban flows and stocks, resulting in conservative, business-as-usual future outlooks. In this study, we present the results of a narrative literature review on drivers and futures of urban metabolism, and consequently use these results to propose and apply a framework that can be used by researchers (i) to systematically identify the drivers of urban metabolism, and (ii) to critically engage with these drivers for the development of transformative future visions. The framework comprises seven thematic categories of drivers (demographic, economic, cultural, political, technological, environmental, and infrastructural) and an eighth category (power) to be used as the lens through which the interactions between drivers, activities, and flows in the city are critically examined. Applying the framework to the case study of biowaste management in Rennes, France, we found it useful for the systematic identification of often overseen drivers. The proposed framework, allowing for a combined analysis of flows and drivers, can become a useful tool toward a solution-oriented urban metabolism research.     

The Changing Metabolism of Cities

Data from urban metabolism studies from eight metropolitan regions across five continents, conducted in various years since 1965, are assembled in consistent units and compared. Together with studies of water, materials, energy, and nutrient flows from additional cities, the comparison provides insights into the changing metabolism of cities. Most cities studied exhibit increasing per capita metabolism with respect to water, wastewater, energy, and materials, although one city showed increasing efficiency for energy and water over the 1990s. Changes in solid waste streams and air pollutant emissions are mixed.
The review also identifies metabolic processes that threaten the sustainability of cities. These include altered ground water levels, exhaustion of local materials, accumulation of toxic materials, summer heat islands, and irregular accumulation of nutrients. Beyond concerns over the sheer magnitudes of resource flows into cities, an understanding of these accumulation or storage processes in the urban metabolism is critical. Growth , which is inherently part of metabolism, causes changes in water stored in urban aquifers, materials in the building stock, heat stored in the urban canopy layer, and potentially useful nutrients in urban waste dumps.
Practical reasons exist for understanding urban metabolism. The vitality of cities depends on spatial relationships with surrounding hinterlands and global resource webs. Increasing metabolism implies greater loss of farmland, forests, and species diversity; plus more traffic and more pollution. Urban policy makers should consider to what extent their nearest resources are close to exhaustion and, if necessary, appropriate strategies to slow exploitation. It is apparent from this review that metabolism data have been established for only a few cities worldwide, and interpretation issues exist due to lack of common conventions. Further urban metabolism studies are required.     

Surveying the Environmental Footprint of Urban Food Consumption

Assessments of urban metabolism (UM) are well situated to identify the scale, components, and direction of urban and energy flows in cities and have been instrumental in benchmarking and monitoring the key levers of urban environmental pressure, such as transport, space conditioning, and electricity. Hitherto, urban food consumption has garnered scant attention both in UM accounting (typically lumped with “biomass”) and on the urban policy agenda, despite its relevance to local and global environmental pressures. With future growth expected in urban population and wealth, an accounting of the environmental footprint from urban food demand (“foodprint”) is necessary. This article reviews 43 UM assessments including 100 cities, and a total of 132 foodprints in terms of mass, carbon footprint, and ecological footprint and situates it relative to other significant environmental drivers (transport, energy, and so on) The foodprint was typically the third largest source of mass flows (average is 0.8 tonnes per capita per annum) and carbon footprint (average is 2.1 tonnes carbon dioxide equivalents per capita per annum) in the reviewed cities, whereas it was generally the largest driver of urban ecological footprints (average is 1.2 global hectares per capita per annum), with large deviations based on wealth, culture, and urban form. Meat and dairy are the primary drivers of both global warming and ecological footprint impacts, with little relationship between their consumption and city wealth. The foodprint is primarily linear in form, producing significant organic exhaust from the urban system that has a strong, positive correlation to wealth. Though much of the foodprint is embodied within imported foodstuffs, cities can still implement design and policy interventions, such as improved nutrient recycling and food waste avoidance, to redress the foodprint.     

中国内陆河流域城市景观过程对涉水生态系统服务的影响评价研究进展

掌握我国内陆河流域城市景观过程对涉水生态系统服务的影响评价研究现状,对于提高内陆河流域人类福祉和促进区域城市可持续发展具有重要意义。系统综述了我国内陆河流域城市景观过程对涉水生态系统服务的影响评价。结果表明:相关中英文论文数量与被引频次整体呈上升趋势,研究对象侧重于水源涵养、水质净化和淡水供给服务,研究方法主要包括价值量评价法和物质量评价法,研究结果则表明城市景观过程已造成涉水生态系统服务总量下降和空间异质性增加,同时还加剧了服务间的权衡关系。相关研究为深入理解内陆河城市景观过程对涉水生态系统服务的影响奠定了良好基础,但在揭示影响机理、模拟未来影响、分析服务权衡、协同与供需流关系以及探索可持续的内陆河流域综合优化管理等方面还存在不足。因此,未来应基于"机理-过程-可持续性"的思路建立内陆河流域城市景观过程对涉水生态系统服务影响评价框架,开展综合评价研究,为我国内陆河流域城市与山水林田湖草综合优化管理提供帮助。     

Ecology and urban planning

Urban areas harbour diverse nature ranging from semi-natural habitats to wastelands, parks and other highly human-influenced biotopes with their associated species assemblages. Maintenance of this urban biodiversity for the residents and for its intrinsic value in the face of increasing population and expanding cities requires that ecological knowledge should be better integrated into urban planning. To achieve this goal understanding of ecological patterns and processes in urban ecosystems is needed. The first step in the necessary urban ecological research is to find out what kind of nature exists in cities. Second, knowledge about ecological processes important in urban nature is required. Although ecological processes in cities are the same as in rural areas, some of them, such as invasion by alien species, are more prevalent in urban than in rural conditions. Third, based on ecological knowledge, management schemes maintaining the diversity of urban nature should be designed. These procedures should also include protection of urban nature, e.g. in urban national parks. Finally, as ecology alone cannot provide the complex information about human influence on urban ecosystems, interdisciplinary research involving natural and social sciences is imperative for a holistic approach to integrating ecology into the process of urban planning.     

Urbanization and Socioeconomic Metabolism in Taipei

The analysis of socioeconomic metabolism has largely been dominated by quantification of material flows on a mass basis. This neglects the energetic dimensions of the urban metabolism and makes analysis that integrates material and energy flows difficult. The present research applies Odum's emergy concept to integrate energy and material flows for the study of the socioeconomic metabolism of the Taipei area. We also take into consideration the urban sprawl in the Taipei area to study its relationship to the change of socioeconomic metabolism. We interpret SPOT satellite images from 1992 and 2002 to provide a deeper understanding of the whole urban system; results show that Taipei's urban areas increased in size during the past decades. Emergy-based indicators show decreasing empower densities (total emergy use per area) of undeveloped and agricultural areas, whereas the empower density of urban areas has increased, which signals a convergence of resource flows toward urban areas. Such an increase of empower density is mainly due to fossil fuel use and translates into increased environmental loading and decreased sustainability. An analysis of the relationship between urbanization and socioeconomic metabolism indicates that changes in land use affect the characteristics of socioeconomic metabolism in Taipei. The effects of urban sprawl on Taipei's urban sustainability are also discussed.     

The metabolism of U.S. cities 2.0

In the fifty years since Abel Wolman first published an estimate of U.S. urban metabolism, the field of urban metabolism has begun to thrive, with cities outside the United States being much of the focus. As cities attempt to meet local and international sustainability goals, it is time to revisit the metabolism of cities within the United States. Using existing empirical databases for material flows (the Freight Analysis Framework) and a published database on urban water flux, we provide a revised estimate of urban metabolism for the typical U.S. city. We estimate median values of metabolism for a city of one million people, considering water resources, food, fuel, and construction materials. Food consumption and waste production increased substantially to 3,800 metric tons per day and 4,900 metric tons per day, respectively. To facilitate a second generation of urban metabolism, we extend traditional analyses to include the embedded energy required to facilitate material consumption with important implications in determining sustainable urban metabolism. We estimate that a city of one million people requires nearly 4,000 gigajoules of primary energy per day to facilitate its metabolism. Our results show high heterogeneity of urban metabolism across the United States. As a result of the study, we conclude that there is a distinct need to promote policies at the regional or city scale that collect data for urban metabolism studies. Urban metabolism is an important educational and decision‐making tool that, with an increase in data availability, can provide important information for cities and their sustainability goals.     

From the urban metabolism to the urban immune system

Urban areas face mounting risks from many sources. Cities pursue myriad tactics to resist, recover from and adapt to shocks and stresses, but little is known about how these approaches relate across the scales of a city nor how cities compare in their abilities. Part of the challenge in addressing these gaps is that the risk to cities is typically studied with an emphasis on one or a few hazards or through the lens of a singular sector. This paper proposes a framework, dubbed the Urban Immune System (UIS) to coalesce and expand industrial ecology research on urban risk management. In the same way that Urban Metabolism (UM) is a unifying framework for urban environmental sustainability, UIS can be a unifying framework for urban resilience, especially related to climate change. Herein, UIS is defined, its many capabilities are dissected and linked to disparate studies; and opportunities for application of the concept are provided. The paper concludes by examining the relationship between UIS and climate change and by identifying those attributes of the UIS that are expected to be of increasing importance under climate change.     

Using spatially explicit commodity flow and truck activity data to map urban material flows

To analyze and promote resource efficiency in urban areas, it is important to characterize urban metabolism and particularly, material flows. Material flow analysis (MFA) offers a means to capture the dynamism of cities and their activities. Urban‐scale MFAs have been conducted in many cities, usually employing variants of the Eurostat methodology. However, current methodologies generally reduce the study area into a “black box,” masking details of the complex processes within the city's metabolism. Therefore, besides the aggregated stocks and flows of materials, the movement of materials—often embedded in goods or commodities—should also be highlighted. Understanding the movement and dispersion of goods and commodities can allow for more detailed analysis of material flows. We highlight the potential benefits of using high‐resolution urban commodity flows in the context of understanding material resource use and opportunities for conservation. Through the use of geographic information systems and visualizations, we analyze two spatially explicit datasets: (1) commodity flow data in the United States, and (2) Global Positioning System‐based commercial vehicle (truck) driver activity data in Singapore. In the age of “big data,” we bring advancements in freight data collection to the field of urban metabolism, uncovering the secondary sourcing of materials that would otherwise have been masked in typical MFA studies. This brings us closer to a consumption‐based, finer‐resolution approach to MFA, which more effectively captures human activities and its impact on urban environments.     

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.     

城市生物多样性分布格局研究进展

城市生物多样性分布格局由自然生态环境和城市化过程所决定;其动态和机理与自然生态系统迥然不同.城市生物多样性为城市生态系统提供了诸多生态系统功能和服务,对改善城市环境、维持城市可持续发展有着重要的意义和作用.城市化过程深刻改变了城市的生物多样性分布格局,导致了诸如本地物种多样性降低、外来物种多样性增加、物种同质化等一系列问题.近年来,城市生物多样性受到学界高度关注,大量研究结果既回答了一些关键性问题,又提出了诸多新的论题和挑战.分析了当前城市生物多样性分布格局研究的若干热点问题,总结了影响城市生物多样性格局的主要因素,探讨了城市生物多样性格局研究方法的关键问题,指出了未来城市生物多样性研究的发展方向,特别强调了城市生物多样性的生态系统功能研究在未来城市生物多样性研究中的重要地位.     

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.     

城市热岛的生态环境效应

城市热岛效应(Urbanheatislandeffect,简称UHI)是一种由于城市建筑及人类活动导致热量在城区空间范围内聚集的现象,是城市气候最显著的特征之一。热岛引起地表温度的提高,必将强烈地影响着城市生态系统的物流、能流,改变城市生态系统结构和功能,产生一系列生态环境效应,影响着城市气候、城市水文、城市土壤理化性质、城市大气环境、城市生物习性、城市物质循环、城市能量代谢以及城市居民健康等。提高能量利用效率、优化城市格局、建设绿色屋顶、采用高反射率地表材料以及增加城市绿地均可有效地控制城市热岛效应。利用遥感手段和数值模型技术,开展多尺度的城市热岛生态环境效应研究,为改善城市生态环境、实现城市可持续发展提供理论依据。     

African Urbanization: Assimilating Urban Metabolism into Sustainability Discourse and Practice

Shaping sustainable, equitable African cities requires strengthened investigations into the cities’ current resource flows, infrastructure systems, and future resource requirements. The field of urban metabolism (UM) offers multiple forms of analysis with which to map, analyse, and visualize urban resource profiles. Challenges in assessing UM in African cities include data scarcity at the city level, difficulty in tracking informal flows, lack of standardized methods, and the open nature of cities. However, such analyses are needed at the local level, given that city practitioners cannot rely purely on urban planning traditions of the global North or the typically broad studies about urban Africa, for supporting strategies toward sustainable urban development. This article aims to draw together the concepts of sustainable development and UM and explore their application in the African context. Further, the article estimated resource profiles for 120 African cities, including consumption of biomass, fossil fuels, electricity, construction materials, and water, as well as emissions of carbon dioxide. These resource profiles serve as a baseline from which to begin assessing the current and future resource intensity of these cities. It also provides insights into the cities’ relative resource impact, future consumption trends, and potential options for sustainability interventions.     

Why academics should study the supply chains of individual corporations

Although fields such as industrial ecology have advanced our understanding of how cleaner technologies, recycling, and lifestyle changes can reduce the impacts of production and consumption on people and planet, environmental deterioration and social injustices stubbornly persist. New strategies are needed to achieve change in an era of increasing urgency. This paper proposes that academics study the supply chains of individual corporations and link them to environmental and social impacts in geographically specific areas. Nongovernmental organizations (NGOs) have used this approach successfully, issuing reports about corporate activity related to deforestation, sweatshops, and other issues of social concern. But academics, by and large, have studied generic products, industries, and sectors. To verify this, after reviewing approximately 11,000 studies on supply chains, we identified just 27 academic papers that focused on individual corporations. These were primarily by NGOs and social scientists, with no studies by industrial ecologists meeting our review criteria. To uncover corporate supply chains, researchers used two distinct methodological approaches: in situ (interviews, surveys, and surveillance) and ex situ (trade data, document analysis, and maps). In this paper, we explain why and how academics should study the supply chains of individual corporations. This is done by combining approaches from industrial ecology, with those from geography, sociology, and other social sciences to develop a political‐industrial ecology of supply chains. This both physically links actual product flows with their environmental impacts, and explores how they affect justice, equity, and welfare. The work we propose offers clear collaborative linkages with NGOs, industry, and the media.     

A Hybrid Approach for Assessing the Multi‐Scale Impacts of Urban Resource Use: Transportation in Phoenix,Arizona

Life cycle assessment (LCA) and urban metabolism (UM) are popular approaches for urban system environmental assessment. However, both approaches have challenges when used across spatial scales. LCA tends to decompose systemic information into micro‐level functional units that mask complexity and purpose, whereas UM typically equates aggregated material and energy flows with impacts and is not ideal for revealing the mechanisms or alternatives available to reduce systemic environmental risks. This study explores the value of integrating UM with LCA, using vehicle transportation in the Phoenix metropolitan area as an illustrative case study. Where other studies have focused on the use of LCA providing upstream supply‐chain impacts for UM, we assert that the broader value of the integrated approach is in (1) the ability to cross scales (from micro to macro) in environmental assessment and (2) establishing an analysis that captures function and complexity in urban systems. The results for Phoenix show the complexity in resource supply chains and critical infrastructure services, how impacts accrue well beyond geopolitical boundaries where activities occur, and potential system vulnerabilities.     

A new physical accounting model for material flows in urban systems with application to the Stockholm Royal Seaport District

Sustainable urbanization requires streamlining of resource management in urban systems which in turn requires understanding of urban metabolism (UM). Even though various methods have been applied for UM analysis, to date there is no standardized method for comprehensive accounting of material flows in urban systems. Moreover, the accounting of material flows is rarely implemented with a bottom‐up approach that can provide a thorough analysis of UM. This article presents the Urban Accounting Model (UAM) which aims to allow comprehensive accounting of urban material flows based on a bottom‐up approach. The model comprises two interlinked sub‐models. The first was developed by integrating a new physical input output table (PIOT) framework for urban systems into a three‐dimensional structure. The second comprises a set of physical accounts for systematic accounting of material flows of each economic sector in the system in order to support the compilation of the PIOTs. The functions of the UAM were explored through its application to two urban neighborhoods in the Stockholm Royal Seaport district. The application highlighted that the UAM can describe the physical interactions between the urban system and the environment or other socioeconomic systems, and capture the intersectoral flows within the system. Moreover, its accounts provide information that allow an in‐depth analysis of the metabolism of specific sectors. Overall, the UAM can function as a useful tool for UM analysis as it systematizes data collection and at the same time depicts the physical reality of the urban system.     

转型期城市生态学前沿研究进展

城市是一类以人类活动为中心听社会－经济－自然复合生态系统。城市人类活动对局地、区域和全球环境的胁迫效应,自然生态系统的响应机制,城市时、空、量、构、序的耦合规律、动力学机制和控制论方法是当前国际社会和学术界关注的热点。介绍了转型期城市人类生态影响研究的一些主要国际科学计划,如ＳＣＯＰＥ及ＩＨＤＰ等,综述了城市生态学研究三大前沿领域的国际研究动向和案例,即人居生态学、产业生态学和城镇生命支持系统生态