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Spatial differentiation in LCA impact assessment

3. Stratospheric ozone depletion

• 3.1 Introduction
• 3.2 Classification
• 3.3 EDIP2003 and updated EDIP97 characterisation factors
• 3.4 Normalisation

Background information for this chapter can be found in:

• Chapter 2 of "Environmental assessment of products. Volume 2: Scientific background" by Hauschild and Wenzel (1998a).
• Chapter 5 of "Guideline in normalisation and weighting – choice of impact categories and selection of normalisation references" by Stranddorf et al., 2005.

3.1 Introduction

The environmental mechanisms underlying stratospheric ozone depletion are global of nature. This means that the impacts caused by an emission are modelled in the same way regardless where on the surface of the earth, the emission takes place. There is therefore no relevance of including spatial variation in the source and receptor characteristics for this impact category. The characterisation factors are site-generic by nature and will be valid for EDIP97 (as an update) as well as for EDIP2003.

The stratospheric content of ozone is disturbed as a consequence of man-made emissions of halocarbons, i.e., CFCs, HCFCs, halons and other long-lived gases containing chlorine and bromine. These substances increase the breakdown of stratospheric ozone, and the ozone content of the stratosphere is therefore falling, and since 1985 an annually occurring dramatic thinning of the ozone layer has been, often referred to as the "ozone hole", over the South Pole. In the last few years, the breakdown of ozone has also accelerated over the northern hemisphere. As a consequence of the thinning of the ozone layer, the intensity of hazardous ultraviolet radiation at the earth's surface has increased over parts of the southern and northern hemispheres. This can have dangerous consequences in the form of increased frequency of skin cancer in humans and damage to the plants which are the primary producers and hence the foundation of the polar ecosystems.

In spite of a nearly complete abandoning of the main contributors to global warming, the conditions of the stratosphere are not expected to be normalised before the second half of this century.

3.2 Classification

For a substance to be regarded as contributing to stratospheric ozone depletion, it must

• be a gas at normal atmospheric temperatures
• contain chlorine or bromine
• be stable with a life in the atmosphere of a few years to centuries, so that it can be transported up into the stratosphere.

The man-made substances contributing to the stratospheric breakdown of ozone are simple gaseous organic compounds with a substantial content of

chlorine, bromine or possibly fluorine. The most important groups of ozone-depleting halocarbons are the CFCs, the HCFCs, the halons and methyl bromide. In contrast to these, the HFCs are a group of halocarbons containing neither chlorine nor bromine, and which are therefore not regarded as contributors to the stratospheric breakdown of ozone.

As for the greenhouse gases, the list of compounds considered as contributing to the stratospheric breakdown of ozone is manageable and can be regarded as exhaustive. In practice, it will therefore not be necessary to check a substance under the above criteria to decide whether it contributes to ozone depletion. It is sufficient to consult the list of ozone depletion equivalency factors in Table 3.1

3.3 EDIP2003 and updated EDIP97 characterisation factors

The endpoint of this impact category is chosen early in the environmental mechanism at the point of disturbance of the ozone content of the stratosphere, and the EDIP2003 and revised EDIP97 characterisation factors are therefore taken from recommendations of the latest version of the WMO status report. The recommendation for EDIP97 is still to use an infinite time horizon but to check the importance if a short time horizon (5 or 20 years) is applied (characterisation factors for shorter time horizons provided in Wenzel et al., 1997).

Table 3.1. Factors for characterisation of stratospheric ozone depletion (in g CFC-11-equivalents/g). Taken from Montzka, Frazer et al., 2002 with range representing spread of reported results from models and semi-empirical.

3.4 Normalisation

The updated EDIP97 person equivalent for stratospheric ozone depletion is 0.103 kg CFC-11-eq/pers/yr as found in Stranddorf et al., 2005.

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Version 1.0 january 2006, © Danish Environmental Protection Agency