Stefan Bringezu
The environmental performance of human activities is widely determined by the quantity and quality of the associated material flows. Whereas information on the specific impacts of the various materials is lacking in most cases, the volumes of the different flows can be analysed in a systematic way to indicate the environmental pressure of national or regional economies. In a first step, the Material Input to the economy taken from the domestic environment and the Material Output to the domestic environment (from the economy) are quantified in a balanced manner. The domestic material flow account for Germany (1991) provides a structured and policy relevant information basis. In a second step, the 'ecological rucksack' of the imports is considered in order to approximate the global Total Material Input (TMI) of the German economy. TMI is regarded as a highly aggregated indicator of environmental pressure associated with the physical basis of an economy. In order to reflect the burden on the global environment due to domestic consumption, the Total Material Consumption (TMC) of a national economy can be accounted for. Thus, material flow accounting may provide structured information that goes beyond singular indicators, but also allows for the deriving of overview indicators to monitor the global environmental pressure associated with an economy.
MATERIAL FLOW RELATED TARGETS FOR SUSTAINABLE DEVELOPMENT
Huge amounts of primary materials are taken from nature annually. The turnover between raw material extraction and final waste management represents the current status of industrialized countries: the 'throughput economy' (Daly 1992; Ayres/Simonis 1994 ).
In order to proceed towards sustainable development, the industrialized world must progressively reduce its material and energy throughput (Schmidt-Bleek 1994; Weizsäcker et al. 1995; see also Meadows et al. 1992; Weterings and Opschoor 1992). The Factor 10 Club (1994) states that there is no fixed relationship between the total value of our economic activity and material throughput. We should work towards cutting in half present global non-renewable material flows, including minerals, fresh water and non-renewable energy carriers. To achieve this, a political commitment to a tenfold increase in the average resource productivity of current industrialized countries would be a prerequisite for meeting the goal of long-term global sustainability. As this strategy is based on present conditions, increases in world population and further economic expansion in the industrialized world would obviously require a factor higher than 10. The OECD environmental ministers (1996) noted the existence of studies which suggest that efficiency improvements of a factor of ten are both necessary and achievable in the next thirty years. Examples of successfully increased resource productivity are given by Weizsäcker et al. (1995, 1997) and Bierter et al. (1996).
Irrespective of the specific degree of dematerialization that will have to be agreed upon by political institutions, there is a need for instruments to monitor the actual throughput of materials and energy on a national level, and to account for the global physical basis of regional or national economies.
MATERIAL FLOWS AND ENVIRONMENTAL PRESSURE
In order to operationalize the environmental pressure of human-induced material flows, two basic questions are of primary interest:
(1) How to indicate the specific environmental pressure caused by material flows that have already been evaluated as 'harmful' ?
Environmental policy has evaluated certain themes to be of prior importance (e.g. global warming). These can be related to the associated material flows (e.g. fossil energy carriers--CO2). Specific pressure indicators can be based on known cause-effect relationships and can be operationalized on the basis of test data (e.g. Global Warming Potential). All existing knowledge about the property of certain materials and specific substances should be used to derive data for the specific impact per unit of material flow.
In that case, a specific problem is the aggregation of the different impact potentials of the different flows (e.g. global warming and eutrophication potentials) in order to get a sufficient overview of the total environmental pressure. This problem can only be solved by personal or societal weighing. Proposals have been presented, e.g. by Adriaanse (1993), Hammond et al. (1995), and further approaches to pressure indices are underway (see Box 2A).
(2) How to indicate the environmental pressure of material flows in a general way, if it is not (yet) known specifically, or is not related to specific substances?
This situation seems to be the norm rather than the exception. For most of the toxic, nutritional, mechanical, structural, and physico-chemical effects associated with material flows, a standardized method for reproducible quantification does not exist. The impacts may result from extracting materials from the environment (e.g. drainage of mines) or from adding something to nature. Some impacts are rather nonspecific with respect to the chemical nature of the materials (e.g. the devastation of landscape and the mechanical destruction of organisms due to the extraction of non-renewable or the harvest of renewable raw materials). Moreover, from a scientific point of view, it is generally impossible to foresee all possible impacts of human-induced material flows that may be of relevance in the future.
Thus, in most cases there is only information available about the volume and the classification of the material flows themselves, and the question mentioned above may also be formulated: Does the accounting of material flow volumes yield any information about the environmental pressure of those flows? Indeed, any material flow induced by humans does change the environment in a more or less unpredictable manner. Therefore, any flow account will indicate the actual situation of environ- mental pressure. Regardless of the unknown impacts per unit of flow, any flow account may be interpreted by assuming the pressure will increase with the amount of the accounted flow (unless specific knowledge is available to prove otherwise ).
If the material flows induced by humans are accounted for in a system-wide approach 'from cradle-to-grave' they can be used to indicate the order of magnitude of environmental pressure related to products and services (Schmidt-Bleek 1993). The Material Input per Service unit (the MIPS) can also be applied to whole economies (Bringezu 1993), and this contribution presents some results.
In this case, a specific problem is the aggregation of different flows of diverse materials. One may, for example, be interested in the total material consumption of an economy, analogous to the total energy consumption, and the question thus arises whether the result should be aggregated into one, or three to five figures (the latter will be proposed in this paper).
Here the second question is addressed because environmental management requires overall information before it can deal with detailed problems. Nevertheless, the data basis for the physical account presented may also be used to indicate specific pressures. A pragmatic approach is proposed based on the available information of integrated economic and environmental accounting.
THE DOMESTIC THROUGHPUT SYSTEM
The Wuppertal Institute has contributed to the development of a domestic overall material flow account for Germany. It has recently been published by the Federal Statistical Office as a part of integrated environmental and economic accounting (Schütz and Bringezu 1993, Kuhn et al. 1994, Bringezu and Schütz 1995, FSO 1995, Radermacher and Stahmer 1996). The method of national material balancing has been developed independently in Austria (Steurer 1992), Japan (Japanese Environmental Agency 1992), and Germany. Bringezu (1993) proposed the establishment of a domestic material flow account as a basis for deriving indicators for sustainability.
The focus is on those flows linked to economic activities. The domestic overall material flow account of Germany comprises the physical mass balance of the domestic extraction from the environment, the domestic deposition and release to the environment as well as imports and exports.
The aim is to provide an overview of the physical basis of the economy and to combine information from different statistics (e.g. production statistics and environmental statistics) to form a coherent framework. Hence, a structured information base can be established to monitor progress towards sustainability.
The throughput of water always dominates the domestic flow balance. In 1991 about 70 billion tonnes of water were derived from natural water paths within Germany (either for use or drainage) which is more than ten times beyond the input of other materials. Thus, water should be treated separately, because any aggregation with other material flows would only be meaningful in terms of water use.
The domestic flow balance of all materials, excluding water, is presented as a flow diagram for Germany 1991 (Figure 1: right side). This overview provides the following major points of information:
With respect to the management of those resource flows, two implications are important:
(1) the input can be taken as a volume indicator for the throughput because any input will become an output.
(2) From a long term perspective, the pressures that are directly related to the outputs (emissions, wastes etc.)1 can only be diminished successfully if the input of primary materials to the economy will be reduced.
However, the extraction of primary materials that are used for domestic purposes is not confined to the national territory. The imports of every country are linked to material flows that burden the environment in other regions. Any shift from the domestic extraction of raw materials to the import of semi or final manufactures may lead to even higher loads on the global environment. For example, a shift of environmental burden due to reduced domestic electricity generation and increased import of electricity would remain undiscovered if the material flows linked to the imports were not accounted for.
The concept of sustainability is a global one, and material flows do not end at the border of any country. If the environmental pressure associated with the physical basis of a national (or regional) economy is indicated with respect to its sustainability, then global material flows interlinked with domestic activities must be considered.
INDICATING THE TOTAL MATERIAL INPUT OF A NATIONAL ECONOMY
In order to account for those material flows that are interlinked with the production of the imports on a cradle-to-border basis, quantitative approximations have been performed (Figure 1-left side). These data have been accounted by conservative calculations based on available statistics (Schtütz and Bringezu 1995). They document minimum values mainly representing the non-saleable extraction interlinked with the production of non-renewable raw materials and the erosion on agricultural land for the production of renewables in the countries of origin.
One result of the preliminary account is that the transnational Material Input has nearly the same order of magnitude as the domestic extraction from the environment (without water and air). Thus, the transnational material flows interlinked with the German economy cannot be neglected when monitoring the global environmental pressure of the national activities.
The Total Material Input (TMI) may be regarded as a highly aggregated indicator that relates to the global environmental pressure associated with the physical basis of an economy. It comprises the domestic and foreign extraction of raw materials taken from nature that is associated with that economy in a certain period (usually one year). Depending on actual technology, no economy would work without the yearly input of materials, either from domestic or foreign origin. Thus, TMI can be interpreted as an indicator for the environmental pressure associated especially with the production of the economy. For practical reasons, TMI should be confined to materials other than water and air.
TMI may be used as a basis to indicate the overall material productivity of an economy. The relation of GDP and TMI provides the material productivity of GDP. This indicator can be interpreted as a measure for eco-efficiency (Bringezu 1993). However, increasing numbers of that indicator do not necessarily reflect a reduction of the absolute environmental pressure. Preliminary data indicate that the order of magnitude of TMI per capita remained nearly constant from 1975 to 1990, while GDP increased more or less steadily (Figure 2). This resulted in an increase of the material productivity of GDP. After the re-unification of Germany the lignite production in the eastern part resulted in somewhat increased TMI. In 1991 TMI was about 90 tonnes per capita (materials without water and air).
The approximation of TMI in the time series was conducted under the assumption of constant ratios of Material Input per product imported to the Federal Republic of Germany (based on 1991 values). Material Input data for raw materials and semi manufactures are also preliminary. Final products have only been accounted with their own mass. Nevertheless, the data quality seems to be sufficient to document, in a first approach, some main trends. The results indicate a possible decoupling of the global Material Input and the economic performance. But the development of absolute environmental pressure due to the material flow basis of the economy is far from a declining tendency which would be necessary for sustainability.
One may argue that any country is responsible for the environmental burden of its exports and that the material flows should not be assigned to the importing country. Indeed, material flow accounting allows for the calculation of the global Total Material Consumption (TMC) of a national or regional economy by considering also those cradle-to-border flows that are associated with the exports (Bringezu 1993). In Figure 3 the calculation of the Material Input of exports is based on the assumption that there is no basic difference in the ecological rucksack2 of products consumed within Germany and exported products (latest results of Behrensmeier and Bringezu (see Box 3D) indicate that the material productivity of the production of exports is about 1.2 times less than the material productivity for the domestic consumption based on relation to GDP or labour). Preliminary accounts indicate an order of magnitude for the German TMC of 70 tonnes per capita in 1991 (materials other than water and air).
CONCLUSIONS
NOTES
1 Of course, there are also environmental pressures that are directly and indirectly associated with the inputs (e.g. due to the extraction of water and materials).
2 The ecological rucksack of a product is the portion of the Material Input used for its production that is not incorporated within the product
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