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From an environmental point of view, MF indicators – whether they reflect material inputs, material consumption or material outputs – inform about anthropogenic, i.e. man-made pressures on the environment. They inform about the direct or proximate environmental pressures that are associated with:

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The extraction of resources. These indicators complement other natural resource indicators, such as those describing the intensity of use of water or forest resources, or those describing energy intensities and efficiencies. They relate to issues concerning the environment's "resource function" (OECD, 1993) and can be associated with natural resource management policies and approaches. The most commonly used material extraction indicator is domestic extraction used (DEU). DEU gives a partial overview of the environmental pressure of materials extraction and needs to be complemented with information on the unused domestic extraction (UDE).

N.B. The extraction of raw materials from natural resources is not always environmentally significant in its own right, but is useful to track changes in the quantities and value of materials produced against future declines and to provide some insight into the scale of the pressure of extraction. It has been used to provide insights into the cumulative burden associated to MF of production and consumption.

♦ Indicators reflecting internal versus external impacts can be derived from economy-wide MF accounts, as well as from individual MF accounts and material system analysis.

♦ Data on unused and indirect material

flows associated with the extraction and import of materials are however not yet sufficiently developed and require further work on conversion factors and calculation methods.

♦ Indicators reflecting intentional versus unintentional releases to the

environment can be derived from economy-wide MF accounts, as well as from individual MF accounts and material system analysis.

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The discharge of pollutants and waste materials. This is the case of indicators that reflect the outputs of residual materials to nature. These indicators complement other environmental indicators describing pollution or waste generation intensities. They are closely related to the environment's "sink capacity" and to environmental quality issues, such as biodiversity, toxic contamination, waste, air quality, climate change. (OECD, 1993). The advantage of output indicators derived from MFAcc is that they help relate material inputs into an economy or an activity to its material outputs and to calculate coherent pollution and waste intensity ratios. MF indicators also inform about the indirect or underlying

activities or factors that cause direct environmental pressures and that are associated with the use and the accumulation of materials in the economy. This is the case of indicators that reflect material inputs and consumption and related intensities, and of indicators that describe material stocks and the physical trade balance of an economy. Materials accumulate in the economy in the form of housing and transport infrastructure, or in the form of durable and semi-durable goods. These materials are sooner or later released back to the environment in the form of demolition waste, end-of-life vehicles, e-waste, bulky household waste, etc..

Generic EW-MF indicators are however not sufficient to reflect issue-specific environmental impacts. Research to develop material flow indicators that more closely relate to actual

environmental impacts, and hence to well recognised environmental policy concerns is in progress. It can be done by using indicators that focus on flows raising specific environmental concerns individually or as a group with respect to air pollution, loss of biodiversity, toxic contamination, human health, climate change, etc. At the very detailed level, when MF

indicators focus on specific hazardous substances and are applied at the micro level, these relationships are easier to establish. At these levels there is a closer link between the weight of the flow and its potential environmental impact. MF data can also be related to results from local environmental monitoring networks and associated with SFA, and can add value to other information tools, e.g. pollutant release and transfer registers.

Reflecting the environmental burden of materials use can also be done by aggregating materials by common characteristics so as to reflect their environmental burden profile or by weighing selected materials or substances according to their potential environmental impact or toxicity.

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Indicators derived from and associated with material system analysis, e.g. on iron & steel, can show, which processes from extraction to final disposal are

associated with the highest resource inputs on the one hand, and the highest waste and pollutant releases to the environment on the other hand. They are particularly useful when the issue of concern is environmental hot-spots of the processing network and can be used in combination with impact indicators derived from life cycle analysis (LCA). (Box 11)

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Indicators reflecting the environmentally weighted material consumption can be used to inform about the overall environmental burden arising from the use of selected materials (see below);

Environmental pressures describe pressures from human activities exerted on the environment, including natural resources. “Pressures” cover underlying or indirect pressures (i.e. human activities themselves and trends and patterns of environmental significance, often referred to as "drivers") as well as proximate or direct pressures (i.e. the use of resources and the discharge of pollutants and waste materials).

Indicators of environmental pressures are closely related to production and consumption patterns; they often reflect emission or resource use intensities, along with related trends and changes over a given period. They can be used to show progress in decoupling economic activities from related environmental pressures, or in meeting national objectives and international commitments. (OECD, 1993, 2003)

Depending on the approach taken, and the primary interest of the study, the data input needed to calculate macro-level indicators reflecting environmental impacts can come from material flow or substance flow accounting, used together with other tools. Examples are:

♦ Economy-wide MF accounts, associated

with LCA

♦ Individual MF accounts and material

system analysis, associated with LCA

♦ Substance flow accounts and analysis

♦ Environmental monitoring data

♦ Pollutant Release and Transfer

Registers (PRTRs) and emission inventories

In the case of indices that weigh materials according to their environmental impact, a combination of data sources and types of analysis is required.

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Indicators derived from and associated with SFA can show which processes are associated with the highest losses of hazardous substances to the environment (when the flow of the critical substance is the indicator), and hence be used to support pollution prevention and control policies, chemicals management and the control of toxic substances. They are particularly relevant when the issue of concern is toxic contamination and when applied at the local or micro level, but can also be applied at a larger scale. (Box 11, Box 12)

Environmentally weighted MF indicators

There have been a few attempts to weight material flows according to their environmental impacts. The impact-based weights might distinguish between large flows with little impact per unit of flow (inert or bulk materials) and small flows having large impacts per unit of flow (highly toxic or persistent materials)43_{. A recent example is environmentally weighted material consumption (EMC)} that combines data from material flow analysis (MFA) and impact coefficients from life cycle analysis (LCA). EMC has been calculated for a group of European countries and for the Netherlands. (Box 13). Work in this area is progressing, but there are still problems of data availability and weighing methods that constrain a systematic development of such indicators at the international level. Developing environmentally weighted measures of materials flows requires a consensus about the validity of the conversion factors used, about the criteria to be used to select the materials to be covered and about the weights to be allocated to each material and to each impact group. This is not an easy task, but can be more easily achieved within a country, in particular at local level, than at international level. The narrower the geographic scope, the greater the homogeneity in spatial and environmental characteristics, and the easier the interpretation of the indicators. Weighted MF indicators appear therefore to be more useful when applied at the national or the local level, or when applied to a homogenous group of countries for which they can give a representative picture. Work towards developing recommended impact coefficients and assessment methods is proceeding within the European Union (http://lca.jrc.ec.europa.eu), and is promoted by the UNEP/SETAC Life Cycle Initiative

(http://www.unep.fr/scp , http://www.setac.org/).

Box 11. Monitoring the environmental impacts of materials: Indicator examples (1) Overview of the "environmental hot-spots" of the iron & steel system, European Union, 2000 (million tonnes)

3.9 CO2

material input (ore plus overburden) 5.8 CO2 (indirect electricity)

738.5 421.6 overburden 121.0 other mining waste

9.4 slag iron ore & ferro-alloys coal

121.3 59.7

111.8 CO2

30.2 CO2 (indirect electricity)

0.09 SOx scrap for recycling 60.2 slag, dust, sludge

84.9

steel* 147.2

75.4 CO2 ('weight'-allocated)

0.07 SOx ('weight'-allocated)

scrap to disposal 25.4 'new' goods*

29.1 scrap 134.7 end-of-life goods* 86.5 * steel content Mining & Refinement (domestic + imports) Production (domestic) Manu- facturing (domestic) Waste management Use (stock)

In this example, the iron and steel system of the EU was analysed on a life-cycle wide basis to address the "environmental hot-spots" along the production-consumption chains.

The figure presents the resulting indicators reflecting major resource inflows, critical emissions and recycling of the extended process network. The study showed that the environmental pressures of primary steel exceed those of secondary steel significantly (ore vs. scrap based supply). The analysis, however, revealed that, even complete recycling (i.e. 100% of the currently generated scrap) would not fulfill current demand for steel and that scrap levels will not meet the level of iron & steel demand before 25 years in the future (an insight that would not have been reached without a MFA model). The results suggested technology improvements and indicated the need for higher materials efficiency in the sectors that use iron& steel as a base material (e.g. construction and automotive sectors).

Source: Moll et al. 2005 Data from substance flow analysis, the Netherlands

FOREIGN COUNTRIES

In document Sistema para la medida de parámetros de la columna de agua (página 59-67)