Patrick Hofstetter

Midpoints versus endpoints: The sacrifices and benefits

On May 25–26, 2000 in Brighton (England), the third in a series of international workshops was held under the umbrella of UNEP addressing issues in Life Cycle Impact Assessment (LCIA). The workshop provided a forum for experts to discuss midpoint vs. endpoint modeling. Midpoints are considered to be links in the cause-effect chain (environmental mechanism) of an impact category, prior to the endpoints, at which characterization factors or indicators can be derived to reflect the relative importance of emissions or extractions. Common examples of midpoint characterization factors include ozone depletion potentials, global warming potentials, and photochemical ozone (smog) creation potentials. Recently, however, some methodologies have adopted characterization factors at an endpoint level in the cause-effect chain for all categories of impact (e.g., human health impacts in terms of disability adjusted life years for carcinogenicity, climate change, ozone depletion, photochemical ozone creation; or impacts in terms of changes in biodiversity, etc.). The topics addressed at this workshop included the implications of midpoint versus endpoint indicators with respect to uncertainty (parameter, model and scenario), transparency and the ability to subsequently resolve trade-offs across impact categories using weighting techniques. The workshop closed with a consensus that both midpoint and endpoint methodologies provide useful information to the decision maker, prompting the call for tools that include both in a consistent framework.

The ECO-indicator 98 explained

The Eco-Indicator 98 project aims at a complete revision of the Eco-Indicator 95 methodology. Like its predecessor, the target is to develop single scores for designers. The method now includes resources and land use. Important improvements are: the use of fate analysis, the much better definition of the damage categories concerned with human health and ecosystem health, using the PAF (Potentially Affected Fraction) and DALY (Disability Adjusted Life Years) concept, and a completely new approach to modelling resources and land use. Perhaps the most fundamental improvement is the management system for value choices. The result of this management system is that there will be three instead of one indicator. Each version is based on a different cultural perspective. The method should be updated continuously. It is proposed to set up an independent organisation to guide this future development.

Modelling the valuesphere and the ecosphere: Integrating the decision makers’ perspectives into LCA

Methods for Life Cycle Impact Assessment have to cope with two critical aspects, the uncertainty in values and the (unknown) system behaviour. LCA methodology should cope explicitly with these subjective elements. A structured aggregation procedure is proposed that differentiates between the technosphere and the ecosphere and embeds them in the valuesphere. LCA thus becomes a decision support system that models and combines these three spheres. We introduce three structurally identical types of LCA, each based on one coherent but different set of values. These sets of values can be derived from the Cultural Theory and are labeled as ‘egalitarian’, ‘individualistic’, and ‘hierarchic’. Within Life Cycle Impact Assessment, a damage oriented assessment model is complemented with both a newly developed precautionary indicator designed to address unknown damage and an indicator for the manageability of environmental damages. The indicators for unknown damage and for manageability complete the set of indicators judged to be relevant by decision makers. The weights given to these indicators are also value-dependent. The framework proposed here answers the criticisms that present LCA methodology does not strictly enough separate subjective from objective elements and that it fails to accurately model environmental impacts.

Einstein's lessons for energy accounting in LCA

The role and meaning of accounting for energy, including feedstock energy, is reviewed in connection to Einstein’s special theory of relativity. It is argued that there is only one unambiguous interpretation of the term energy-content: The one that corresponds tome The implications for life cycle inventories is that all discussions concerning upper heating value, lower heating value, feedstock energy, etc. are pointless as long as the motivation for choosing one or the other is not specified in relation to the safeguard subjects defined for a particular analysis (LCA or energy analysis). The subjective aspects of energy accounting schemes, even though based on mere thermodynamics, are highlighted. In inventory analysis, it is recommended that energy carriers should be accounted separately and in mass terms.For illustrative purposes, energy statistics and energy assessment are discussed in view of the safeguard subjects underlying the accounting procedures. Based on a set of theses, one possible energy accounting scheme as an indicator of the “consumption of non-renewable energy resources” within the impact assessment of LCA is sketched. It is emphasised that energy accounting schemes do not reflect environmental impacts caused by the energy sources, and the characteristics of the indicator “consumption of non-renewable energy resources” introduced here are highlighted.

The MIIM LCA Ph.D. Club : Presentation and introduction

During 1998, the number of completed Ph.D.s on Life Cycle Assessment (LCA) seemed to be larger than any previous year. In order to mark this achievement, a special series is being published in the International Journal of LCA. In this introductory paper, the Class of MUM outline the results of their research work over the last few years. A number of common points and tendencies have emerged through this work. First of all, the scope-dependency of LCA models: some of us have discerned in particular the need to distinguish between descriptive and change-oriented LCAs. Secondly, a number of the theses focus on the interaction between LCA and decision-making. Thirdly, the benefits of pluralism in impact assessment and allocation have been advocated in some of the theses. Finally, it may be noted that in these theses structuring the management of controversial issues seems to be preferred to eliminating such issues by a process of harmonisation. Future papers will map out the intellectual journeys undertaken in the development of these theses and discuss key findings in more detail.

Modelling the Valuesphere and the Ecosphere

Methods for Life Cycle Impact Assessment have to cope with two critical aspects, the uncertainty in values and the (unknown) system behaviour. LCA methodology should cope explicitly with these subjective elements. A structured aggregation procedure is proposed that differentiates between the technosphere and the ecosphere and embeds them in the valuesphere. LCA thus becomes a decision support system that models and combines these three spheres. We introduce three structurally identical types of LCA, each based on one coherent but different set of values. These sets of values can be derived from the Cultural Theory and are labeled as ‘egalitarian’, ‘individualistic’, and ‘hierarchic’. Within Life Cycle Impact Assessment, a damage oriented assessment model is complemented with both a newly developed precautionary indicator designed to address unknown damage and an indicator for the manageability of environmental damages. The indicators for unknown damage and for manageability complete the set of indicators judged to be relevant by decision makers. The weights given to these indicators are also value-dependent. The framework proposed here answers the criticisms that present LCA methodology does not strictly enough separate subjective from objective elements and that it fails to accurately model environmental impacts.

Modelling the Ecosphere by the Structured Aggregation Procedure

While Chapter 3 described the model of the valuesphere, this one will discuss, explore, and finally describe how the ecosphere is to be modelled. After a specification of the problem setting, we propose to model the sphere by the three different aspects ‘damage’, ‘unknown damage’ and ‘manageability’ (Section 4.2). For each of them, a separate structure will be suggested which leads through aggregation to an index (Sections 4.3 to 4.5). As already argued in Section 2.1, the ecosphere can only be modelled by assuming an underlying valuesphere. Therefore, the relevance of the three indices depends on the cultural perspective adopted. The value choices within the single indices are suggested separately for each cultural perspective. An overview of the whole structured aggregation procedure is provided in Section 4.6. The prescriptions for the final rules of composition and aggregation have to be seen as preliminary at this stage of their development. Empirical work with decision makers may well alter the results of this last step.

DALYs — An Index for Human Health Assessment

The structured aggregation procedure presented in Chapter 4 has been designed to measure the importance of environmental problems by three main criteria: the magnitude of damage they generate, the manageability of these damages, and the unknown damage. Suggestions for how these criteria could be operationalised and concepts for doing so have already been given in Sections 4.3 to 4.5. This chapter is limited to a further elaboration of the way the magnitude of damage to human health can be measured. It focuses exclusively on the problem of aggregating different health outcomes and introduces a health index for this purpose. This limited focus allows for going into details and looking at the problems likely to occur when the damage assessment introduced in Section 4.3 is put into practice. The same level of detail is likely to be needed when one would want to look at the criterion of manageability or develop an index for damage to ecosystem health in greater detail than has been done so far in Section 4.3. An important difference between the areas of human and ecosystem health is that, in the former, there is extensive literature available from medical science and health policy which goes back many decades, while the literature on environmental health is less comprehensive because of a more recent origin and the coverage of only a limited range of issues.

Damage to Human Health from Environmental Chemicals that Cause Cancer

The objective of this chapter is to demonstrate the quantitative feasibility of the framework introduced in Chapters 3 to 5, evidenced by the example of environmental chemicals causing cancer in humans. The damage to human health will be assessed by the modelling of an impact pathway starting with the fate or exposure analysis following an emission, the effect analysis following an exposure of human beings, and an analysis of the resulting diseases due to tumours. The causal relationship between emissions to air or water and damage to human health will be presented in terms of disability adjusted life years (DALYs) per kg substance emission. Further, the index for manageability will be assessed following the proposal in Section 4.5. Both, the resulting index for the magnitude of damage and the index for manageability will be derived in dependence of the cultural perspective applied, i.e., they look differently for the individualists, egalitarians, or hierarchists perspective.

Damage to Human Health from Respiratory Effects

The choice of impact categories for operationalisation has been justified in Subsection 4.3.6. In this chapter we operationalise the impact category ‘respiratory effects in human beings’. Effects in humans due to the different acting agents are assessed through the construction of damage factors. Damage factors are composed of the fate factors to calculate exposure due to emissions (Section 7.2), of the effect factors to determine expected effects in humans (Section 7.3), and of the disability adjusted life years lost due to the assessed effects (Section 7.4).