Bengt Steen

The focus of this chapter is on evaluation of impacts from emissions, resource extractions and other interventions from human activities and technical systems on our environment. The analysis of technical systems is only briefly touched upon. The term 'evaluation' is used to represent a subjective view on descriptions of processes and states in objective physical terms. This means that both physical parameters and human attitudes and preferences are included.

Evaluation of environmental impacts from human activities is made in several contexts in society and several evaluation methodologies or methodological frameworks exist. Sometimes these are called 'tools' and thought of as being part of a 'toolbox'. When needed, the appropriate tool is picked out of the toolbox and used for impact evaluation. In reality the flexibility of the various tools is such that they overlap in many applications. The tools have many similarities but their focus and terminology vary.

The oldest tool is probably risk assessment (RA). There are three types of risk assessment: for human health, for ecological health and for accidents. The first two are mostly used for chemicals and the third for industrial activities (including chemical manufacturing). They all are carried out in a similar way: first there is a hazard identification step, second there is a risk estimation step (hazard impact times probability) and third there is a risk communication step. The RA methodology has been strongly influenced by several major industrial accidents (notably Seveso and Bhopal) though it has evolved in the direction of assessing risks of chemicals being introduced or used in a market context. The information gained from risk assessment is intended to be used to support a decision about issuing a permit or for formulating rules or restrictions about its use. In short, risk assessment aims at identifying risks and decreasing them to an acceptable level.

A similar aim lies behind environmental impact assessment (EIA), but the object of study is usually not a chemical substance but the building and operation of an industrial plant or other large-scale technological projects. Compared to the situation when making a risk assessment, there is a known location of the activity and the amounts of various substances involved are fairly well known. An EIA therefore involves compiling an inventory and description of the surroundings and dispersion modeling of emissions from the plant.

Measures to reduce environmental impacts are often evaluated by economic techniques. The best-known technique is called cost-benefit analysis (CBA). CBA analysis may vary much in depth with regard to the impact evaluation. Sometimes the economic value of an impact is determined by just asking people how much they are willing to pay (known as WTP) to reduce the pollutant concentrations by some amount (say, by half). There is a symmetric technique, called willingness to accept (WTA) in which people are asked how much they would be willing to accept in exchange for some defined reduction in environmental amenity. A rather different approach, known as 'hedonic' analysis, attempts to account for the price or asset value of a complex good, by disaggregation into contributions from different attributes (Pearce 1993; Herriges and Kling 1999). Thus real estate values in otherwise similar areas may reveal an implicit valuation for (avoiding) sulfur dioxide pollution from a nearby plant. Sometimes the valuation modeling is more elaborated, as in the ExternE project of the European Commission (1995). Other techniques include environmental cost accounting, environmental accounting and life cycle costing (LCC). All these may be included under the rubric of 'environmental economics'.

In life cycle assessment (see Chapter 12.5) and its subprocedure life cycle impact assessment (LCIA), the object of study is a product or service. The goal of an LCA may vary but, mostly, the LCIA is intended to be used - sooner or later - in a choice between two products or processes. The comparative element in LCIA requires a comprehensive approach, in which the focus is different from risk assessment and EIA. Besides studying each impact type separately, the weighting of various impacts becomes an issue. The LCIA procedure is standardized by the International Standards Organization (ISO) and described in the ISO 14042 standard. A technical report (ISO TR 14047) is at present being worked out with examples on how the standard may be implemented (ISO 2000).

Engineering science and natural science make different demands on LCIA. In engineering science the product's overall performance is the focus. The product is intended to function as well as possible in a number of situations. In natural science, the theory is central. The theory is intended to function as well as possible in a number of situations. The inclusion of uncertain models or data in a natural science-oriented context may be objectionable, whereas omission of it would be objectionable to the engineering scientist, as it would be tantamount to neglecting a likely problem. Experience, in particular from the LCA area, has revealed many such methodological conflicts.

From a system analysis point of view, all impact evaluation techniques may be seen to deal with the technical, natural and the social subsystems (Figure 13.1). The technical system may be further divided into a foreground and a background system. The foreground system is the one you know and can specify in detail. The background system includes, for instance, market behavior and infrastructure.

Figure 13.1 An impact evaluation combining scenarios for technique, environment and human attitudes

In industrial ecology (IE) you will need a toolbox for different types of impact evaluations. But instead of describing the different tools as they mostly are used, one by one, some procedural steps, which are common to all tools, will be used to structure the text of this chapter:

• formulation of goal and scope;

• selection of impact indicators;

• modeling or recognizing interactions between technical system indicators and impact indicators;

• comparing different types of impacts and evaluation of total impact;

• analysis of uncertainty and sensitivity;

• data documentation and reporting.

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