In the above context, two basic types of material flow-related analyses may be distin- guished according to their primary focus; although in practice a continuum of different approaches exists (Table 8.1). Neither type I nor type II is strictly coincident with the above-mentioned two paradigmatic strategies. However, the importance of the detoxifi- cation concept seems highest in Ia and lowest in IIc. In contrast, the intention to support dematerialization seems highest in analyses of IIc and lowest in Ia. Nevertheless both
complementary strategies are increasingly being combined, especially in Ic and IIa.
Whereas type I analyses are often performed from a technical engineering perspective, type II analyses are more directed to socioeconomic relationships.
Table 8.1 Types of material flow-related analysis
Type of analysis I
a b c
Objects of Specific environmental problems related to certain impacts per unit flow of:
primary interest
substances materials products
e.g. Cd, Cl, Pb, Zn, Hg, e.g. wooden products, e.g. diapers, batteries, N, P, C, CO2, CFC energy carriers, cars
excavation, biomass, plastics
within certain firms, sectors, regions II
a b c
Problems of environmental concern related to the throughput of:
firms sectors regions
e.g. single plants, e.g. production sectors, e.g. total or main medium and large chemical industry, throughput, mass flow companies construction balance, total material
requirement associated with substances, materials, products Source: Adapted from Bringezu and Kleijn (1997).
Type Ia
Substanceflow analysis (SFA) has been used to determine the main entrance routes to the environment, the processes associated with these emissions, the stocks and flows within the industrial system as well as the trans-media flows, chemical, physical, biological transfor- mations and resulting concentrations in the environment (see Chapter 9). Spaciotemporal distribution is of high concern in SFA. Results from these analyses are often used as inputs to further analyses for quantitatively assessing risks to substance-specific endpoints.
A variety of studies have been conducted on toxic heavy metals such as arsenic, cadmium, chromium, copper, mercury, lead and zinc (Ayres, Ayres and Tarr 1994; Ayres and Ayres 1996; Ayres and Ayres 1999a; Reiner et al. 1997; Dahlbo and Assmuth 1997;
Maag et al. 1997; Hansen 1997; Maxson and Vonkeman 1996; Voet et al. 1994; see also Chapters 27 and 28).
Nutrients such as nitrogen and phosphorus are taken into account mainly because of eutrophication problems and the search for effective mitigation measures (Ayres and Ayres 1996; Voet 1996).
Theflow of carbon is studied because it is linked to global warming due to current fossil
fuel dependence. The accounting for carbon dioxide and other greenhouse gas emissions and the study of trends, sources, responsible technologies, possible sinks and measures for abatement have been increasingly reported by statistical services.
Theflow of chlorine and chlorinated substances has been subject to various studies owing to the toxic potential and various pollution problems through chlorinated solvents and persistent organochlorines (Ayres and Ayres 1999a; Kleijn et al. 1997), the ozone- depleting effect of CFCs (Obernosterer and Brunner 1997) and a controversial debate over risks incurred through incineration of materials such as PVC (Tukker 1998).
Type Ib
Selected bulk material flows have been studied for various reasons. Resource extraction by mining and quarrying was studied to assess the geomorphic and hydrological changes due to urbanization (see Chapter 28). The flow of biomass from human production has been studied to relate it to biomass production in natural ecosystems in order to evaluate the pressure on species diversity (Vitousek et al. 1986; Haberl 1997).
On the one hand, metals like aluminum, timber products like pulp and paper, and con- struction aggregates represent important base materials for industrial purposes. On the other hand these flows – although per se rather harmless – may be linkedwith other flows significantly burdening the environment, for example, the ‘red mud’ problem with alumina production and the energy-intensive production of aluminum (Ayres and Ayres 1996).
Base materials such as plastics have been subject to various studies on the potentials and environmental consequences of recycling and cascading use (for example, Fehringer and Brunner 1997; Patel 1999).
Possible effects of alternative technologies and materials management on global warming potential have been studied, for example for construction materials (Gielen 1999). This kind of analysis is related to studies of types Ic and IIb.
Type Ic
When the environmental impacts of certain products and services is the primary interest, the approach is normally denoted life cycle assessment (LCA). The product LCA literature is reviewed in Chapter 12. In general, the system boundary of LCA (‘cradle to grave’) cor- responds with the systems perspective of the anthroposphere, technosphere or physical economy. Some methods of evaluation may be used for LCA and MFA as well (see Chapter 13).
From type Ia to type Ic the primary interest becomes increasingly comprehensive and complex (Table 8.1). It commences with the analysis of selected substances, considered compound materials and progresses to products consisting of several materials. Not only the number of potential objects but also the number of potential impacts per study object increases by several orders of magnitude. The complexity of the associated chain net also grows.
Type IIa
The primary interest may lie in the metabolic performance of a firm or household, a sector or a region. In this case, there may be no or insufficient information about specific envi-
ronmental problems. Often the main task is to evaluate the throughput of those entities in order to find the major problems, support priority setting, check the possibilities for improvement measures and provide tools for monitoring their effectiveness.
Accounting for the physical throughput of a firm is becoming more and more common- place, at least for bigger companies. It is found in corporate environmental reporting.
Materials accounts are used for environmental management (see Orbach and Liedtke 1998 for a review for Germany). Eco-efficiency at the firm level has been indicated in reports (for example, WBCSD 1998, 1999 – method overview and pilot study results;
Verfaillie and Bidwell 2000 – program activities). Flow analyses of materials have been applied for optimization within companies (Spengler 1998). However, the limited scope offirm accounts calls for complementary analyses with a wider systems perspective, either through LCA-type analyses for infrastructures (Bringezu et al. 1996) and main products (for example, Liedtke et al. 1998) or by analyses of higher aggregates of production and consumption, that is analyses of total production sectors or whole economies.
Type IIb
When the primary interest is devoted to certain industrial sectors or fields of activity, MFA may be used to identify the most critical fluxes in terms of quality and/or quantity.
For instance, different industrial sectors may be compared with regard to various inputs and outputs either from other sectors or from the environment (Ayres and Ayres 1998;
Hohmeyer et al. 1997; Windsperger et al. 1997). When the analysis comprises all sectors of a region or national economy in a comparative manner, the accounting is closely related to type IIc; in that case the main interest may still be devoted to the national economy as a whole and the sectoral analysis serves to indicate those sectors which are of prior importance regarding criteria of specific interest (for example, CO2emission inten- sity or resource intensity). In those cases, a top-down approach is usually applied. Certain sectors or activities may be analyzed in detail, for example, the construction sector (Glenck and Lahner 1997; Schandl and Hüttler 1997) or activities such as nutrition, clean- ing, maintaining a dwelling and working, transport and communication (Baccini and Brunner 1991). Analyses of this type may have strong interrelations to type Ib, as when for instance construction material flows are accounted for in a comprehensive manner (Bringezu and Schütz 1998; Kohler et al. 1999).
Type IIc
A major field of MFA represents the analysis of the metabolism of cities, regions and national or supranational economies. The accounting may be directed to selected sub- stances and materials or to total material input, output and throughput.
The metabolism of cities was analyzed in early studies by Wolman (1965) and Duvigneaud and Denayer-DeSmet (1977) and thoroughly for the case of Hong Kong (Boyden 1980; Koenig 1997) and Vienna (Obernosterer et al. 1998). For a review, see Einig (1998). At the regional level a comprehensive milestone study was performed by Brunner et al. (1994) for the Swiss valley, Bünztal. The flow of pollutants was analyzed by Stigliani and Anderberg (1994) for the Rhine basin. The metabolism of the old industrialized German Ruhr region was studied by Bringezu and Schütz (1996b). Economy-wide MFA
at the national level has attracted special attention (see below). The main interest lies in the overall characterization of the metabolic performance of the studied entities, in order to understand the volume, structure and quality of the throughput and to assess the status and trend with regard to sustainability.
The term ‘MFA’ has usually referred to analyses of types Ia, Ib, IIb and IIc. Studies of type Ic are generally considered to fall under the heading of LCA. Accounting of type IIa is mainly related to environmental management. There are also combinations of regional and product-oriented analyses. Accounting for the hidden flows of imports (and exports), that is upstream resource requirements of imported (or exported) products, may be com- bined with the domestic resource requirements of a regional or national economy in order to provide the total material requirements (TMR) (and total material consumption – TMC) indicators (Bringezu et al. 1994; Adriaanse et al. 1997). Nevertheless, all of these analyses use the accounting of material inputs and outputs of processes in a quantitative manner, and many of them apply a systems or chain perspective.