Understanding the structure and functioning of the industrial or societal metabolism is at the core of industrial ecology (Ayres 1989a; see also Chapters 1, 2 and 3). Material flow analysis (MFA) refers to the analysis of the throughput of process chains comprising extraction or harvest, chemical transformation, manufacturing, consumption, recycling and disposal of materials. It is based on accounts in physical units (usually in terms of tons) quantifying the inputs and outputs of those processes. The subjects of the accounting are chemically defined substances (for example, carbon or carbon dioxide) on the one hand and natural or technical compounds or 'bulk' materials (for example, coal, wood) on the other hand. MFA has often been used as a synonym for material flow accounting; in a strict sense the accounting represents only one of several steps of the analysis, and has a clear linkage to economic accounting.
MFA has become a fast-growing field of research with increasing policy relevance. All studies are based on the common paradigm of industrial metabolism and use the methodological principle of mass balancing. However, there are various methodological approaches which are based on different goals, concepts and target questions, although each study may claim to contribute to knowledge of the industrial metabolism. In 1996, the network ConAccount was established to provide a platform for information exchange on MFA (www.conaccount.net). A first inventory on MFA projects and activities was provided (Bringezu et al. 1998a). Several meetings took place (Bringezu et al. 1997, 1998b; Kleijn et al. 1999) and a research and development agenda was defined through an interactive process (Bringezu et al. 1998c).
The diversity of MFA approaches derives from different conceptual backgrounds. The basic concept common to many studies is that the industrial system together with its societal interactions is embedded in the biogeosphere system, thus being dependent upon factors critical for the coexistence of both systems (Ayres and Simonis 1994; Baccini and Brunner 1991, see also Chapter 2). The paradigm vision of a sustainable industrial system is characterized by minimized and consistent physical exchanges between human society and the environment, with the internal material loops being driven by renewable energy flows (for example, Richards et al. 1994). However, different strategies have been pursued to develop industrial metabolism in a sustainable fashion.
One basic strategy may be described as detoxification of the industrial metabolism. This refers to the mitigation of the releases of critical substances to the environment by pollution reduction. In a wider sense, this relates to any specific environmental impact such as toxicity to human beings and other organisms, eutrophication, acidification, ozone depletion, global warming and so on. Regulatory governmental actions in terms of substance bans and restrictions of use represented the first measures of environmental policy (see Chapter 6). The concept of cleaner technology is aimed primarily towards the mitigation of critical releases to the environment (see Chapter 4). It is possible that, as a consequence of the effectiveness of such measures, pollution problems in the spatial-temporal short range could be solved. Transregional and global problems and problem shifting to future generations, however, as well as the complexity of the industrial metabolism, made it necessary to analyze the flows of hazardous substances, selected materials or products in a systems-wide approach; that is, from cradle to grave, and with respect to the interlinkage of different flows.
Another complementary strategy may be regarded as dematerialization of the industrial metabolism. Considering the current quantity of primary resource use by industrial economies, an increase of resource efficiency by a factor of 4 to 10 was proposed (Schmidt-Bleek 1994a, 1994b; Weizsäcker et al. 1997). This goal has been adopted by a variety of international organizations and national governments. On the program level the factor 4/10 concept was adopted by the special session of the United Nations (UNGASS 1997) and the World Business Council for Sustainable Development (WBCSD 1998). The environmental ministers of the OECD (1996a) urged progress towards this end. Several countries included the aim in political programs (for example, Austria, the Netherlands, Finland and Sweden; see also Gardener and Sampat 1998). In Scandinavian countries research was launched to test the broad-scale feasibility of factor 4/10 (Nordic Council of Ministers 1999). In Germany a draft for an environmental policy program (BMU 1998) refers to a factor of a 2.5 increase in productivity of non-renewable raw materials (1993 to 2020). An increase in eco-efficiency is now considered essential by the environmental ministers of the European Union (1999). The review of the Fifth (environmental) Action Programme (Decision No 2179/98/EC) emphasizes resource use and efficiency.
The factor concept aims at the provision of increased services and value-added with reduced resource requirements. Dematerialization of the economy may imply a diminution of all hardware products and thus the throughput of the economy as a whole, comprising the use of primary and secondary materials. However, dematerialization may also be directed more specifically to the reduction of the primary inputs and/or final waste disposal. The concept of eco-efficiency includes not only the major inputs (materials, energy, water, area) but also the major outputs to the environment (emissions to air, water, waste) and relates them to the products, services or benefits produced (EEA 1999a; OECD 1998b; Verfaillie and Bidwell 2000). However, for the environment the reduction of the absolute impacts through material flows is essential. Thus, the quantity of human-induced material flows through the industrial system must also be adjusted to adequate levels of exchange between the economy and the environment.
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Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.