以材料“创造”土地？——中国城市化进程的一个重要特征

中国快速城市化进程的一个重要特征是以土地为载体,通过大量投入钢铁、水泥等建材大规模修建城市建筑和基础设施,创造出大量的城市生产和生活空间。利用1985—2010年中国省级行政单元城市建成区总面积、城市居住用地总面积、城市住宅总面积和城市住宅建筑材料总使用量等数据,识别城市扩张模式,揭示中国城市化进程中土地、建筑面积及其构筑材料三者间的关系。研究表明2000年是中国城市扩张的重要分界点,2000年之前中国各省份的城市建成区总面积、城市住宅总面积和城市住宅建筑材料总使用量均较小且省份间差异不大,2000年之后三者迅速增长且省份间差异逐渐扩大。在地区尺度上,三者均呈现东部地区最高、中部次之、西部最低的特点,地区内部差异则表现为东部地区最大、西部次之、中部最小的特征。大多数省份的城市住宅总面积及其构筑材料总量随着城市建成区的扩张而增长,表明城市在发展初期以扩大建成区和水平扩张为主。随着城市化水平的不断提高,城市内部空间重组和用地置换导致高层建筑逐步替代了原有的单层或低矮建筑,城市扩张的方向由依赖土地的水平扩张转向以大量使用建筑材料为基础的垂直扩张,使得许多省份的城市住宅总面积逐渐超过辖区内居住用地总面积。这种以建筑材料\"创造\"出更多\"土地\"的城市垂直扩张在满足人们对城市生产和生活空间需求的同时,有利于节约土地资源和保护生态空间,但需要以消耗更多的建筑材料并承担建筑材料在开采、制造、运输、使用和废弃过程中所造成的环境影响为代价。     

Lifespan of Commodities,Part I

Lifespan is an essential parameter for the accounting and analysis of material stocks and flows, one of the main research topics in industrial ecology. Lifespan is also important as a parameter that portrays the current and historical situation of industrial metabolism, which is an area of interest to industrial ecologists. In the present article, the available information from various reports on product lifespan was reviewed. Although we found a large number of data for many durables, the definition of lifespan in published articles varied, which limited our ability to compare reported values. We therefore first defined lifespan and then compared the international and historical data. We compiled more than 1,300 data sets from various sources and identified some differences among the types of goods and among regions. With the reviewed data noted in this article, we established a database, named LiVES (Lifespan Database for Vehicles, Equipment, and Structures), and will disclose it on the Internet to share the information.     

The Metabolic Transition in Japan

The notion of a (socio‐) metabolic transition has been used to describe fundamental changes in socioeconomic energy and material use during industrialization. During the last century, Japan developed from a largely agrarian economy to one of the world's leading industrial nations. It is one of the few industrial countries that has experienced prolonged dematerialization and recently has adopted a rigorous resource policy. This article investigates changes in Japan's metabolism during industrialization on the basis of a material flow account for the period from 1878 to 2005. It presents annual data for material extraction, trade, and domestic consumption by major material group and explores the relations among population growth, economic development, and material (and energy) use. During the observed period, the size of Japan's metabolism grew by a factor of 40, and the share of mineral and fossil materials in domestic material consumption (DMC) grew to more than 90%. Much of the growth in the Japanese metabolism was based on imported materials and occurred in only 20 years after World War II (WWII), when Japan rapidly built up large stocks of built infrastructure, developed heavy industry, and adopted patterns of mass production and consumption. The surge in material use came to an abrupt halt with the first oil crisis, however. Material use stabilized, and the economy eventually began to dematerialize. Although gross domestic product (GDP) grew much faster than material use, improvements in material intensity are a relatively recent phenomenon. Japan emerges as a role model for the metabolic transition but is also exceptional in many ways.     

Lifespan of Commodities,Part II

Lifespan of commodities is essential information for material flow analysis and material stock accounting. Lifespan data is available in the literature; however, it varies in definition and in methodology employed. This article reviews and categorizes different types of lifespan distribution and distribution estimation methodologies, and investigates the relationship and differences between lifespan definitions and estimation methodologies. Lifespan distribution of commodities can be classified into five types from two perspectives: base year for which the distribution is drawn, and vertical axis of the distribution. The methodologies for estimating lifespan distribution were classified into four types and the details of each methodology and the relationship to the definition of lifespan were also clarified. This article also examines differences in actual lifespan data—between the types of distribution, the definitions, and the employed methodologies—by comparing reported data in literature. Any of the four methodologies are theoretically applicable and provide the same value of a lifespan; however unless accurate data such as census statistics are available, lifespan data can vary, and therefore we must be very cautious about the representativeness of sample data.     

Probabilistic Assessment of Industrial Synergistic Systems

A probability‐based method is presented for assessing the reliability of synergistic systems and their ability to cope with the uncertainties often associated with two of a company's main types of activities: those carried out by the manufacturing department, and those carried out by the storage department. This method is based on a model focusing on the dynamic simulation of synergistic flows in terms of the mass balance. It differs from previous material flow analysis tools, which do not take into account the temporary failures occurring at the companies involved and the resulting loss of production capacity. The failure events occurring at any of the companies in a synergistic system may result in various levels of synergy failure and a short supply of resources for other companies. We therefore propose to identify the main factors responsible for a lack of synergy. We developed a dynamic stock simulation model for assessing the reliability of synergistic systems as well as that of the individual companies of a system before and after a synergy is set up. We first confirm the validity of this model by comparing the results with those based on the binomial theorem in system reliability analysis, and we then apply the model to the case of an industrial system. We conclude that companies involved in a synergistic system will inevitably be exposed to a higher risk of resource shortage because of the unsteady synergistic and outsourcing flows on which they depend. More efficient stock management methods would prevent the occurrence of the risks often associated with synergistic flows.