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Input/Output analysis - Shortcuts to life cycle data?

11. The statistical basis for integration of the working environment in LCA

Anders Schmidt, dk-TEKNIK

11.1 Introduction

The present paper gives a short overview of the basic statistical information used in the development of a new methodology for life cycle assessment of the working environment (WE-LCA) and for establishing the database used together with the methodology.

The new methodology is based on two types of Danish statistical information regarding economic sectors, i.e. information on the amounts being produced (in weight units) in a number of sectors, and information on the number of reported work-related diseases and damages in the same sectors. By combing these statistics, it is possible to calculate working environmental impacts per produced unit, which can be used as a supplement to information on the impacts on the external environment.

The general methodology uses two types of statistical information to derive the database:

The basic equation used to derive the information for a sector can be expressed in the following way:

In practice, a five-step procedure was used to derive the information. The five steps are described in the following and to some extent exemplified. For a detailed description of the methodology, the reader is referred to the Technical Report and the Guidelines from Subproject 3 in the Danish LCA-methodology and Consensus-project, which is under publication by the Danish Environmental Protection Agency.

11.2 The five-step procedure

The five steps in the procedure have the following headings

11.2.1 Step 1 - Selection of sectors

The first step is selecting sectors and sub-sectors with a significant number of work-related accidents and diseases. By choosing sectors with a significant impact on the working environment the statistical uncertainty regarding the number of impacts is reduced.

Another important criterion is that the sector can be characterised by one or more unit processes that are of interest in relation to LCA. The sector "Production of plastics packaging" (NACE-code 252200) thus comprises processing of almost all types of plastics using extrusion, injection moulding etc., but it is not possible to achieve a higher level of detail. Another example is the sector "Production and first processing of lead, zinc and tin" (NACE-code 274300) which - as the title indicates - comprise both production and processing of all three materials.

11.2.2 Step 2 - Specifying the production in the sector

The second step is to identify in the goods statistics the products that are being produced in the selected sectors. The products are identified by an 8-digit code that is unequivocally related to an economic sector. As an example, products made in the sector "Production and first processing of lead, zinc and tin" (NACE-code 274300) all start with the numbers 78 (lead), 79 (zinc) and 80 (tin), respectively.

It is strongly suggested that this step - and the subsequent calculations in step 3 - is performed by a professional statistician from a governmental statistical agency with access to the basic statistics given by the companies.

11.2.3 Step 3 - Calculating the total weight of the produced amounts in a sector

The third step is to produce an aggregate of the produced amounts (in tons) for all goods in the chosen sectors. The basic information in the goods statistics is exemplified in Table 11.1.

Table 11.1
Example of basic statistical information from the goods statistics used in the calculation of produced amounts in a sector.

When information on the weight of the products was not available, e.g. as indicated by the questionmarks in Table 11.1 additional information from the foreign trade statistics was used to calculate the weight of the production. Information from the companies to be used in the foreign trade statistics must contain information on the weight and the value of exported products, and the average value per weight unit of the export was used to calculate the weight of the total production of a given product:

This additional information was necessary for all those products where the produced amounts are reported in other units than weight in the goods statistics, most pronounced in the textile sector.

With the additional information from the foreign statistics, the weight of the produced amount in a sector can be calculated by simple addition.

11.2.4 Step 4 - Accounting for the working environmental impacts

The sixth step is not a calculation, but simply accounting for the work-related injuries and damages for the activities in the same sector as the produced volume was calculated for.

In Denmark, all notified occupational accidents and occupational diseases are recorded by the Registry of Occupational Injuries, which is a part of the Danish National Labour Inspection Service. The information is treated statistically and is published annually on a 2- or 3-digit DB93/NACE-code level. The Danish National Labour Inspection Service is however able to specify the statistics in more detail upon request, i.e. on the 4- or 5-digit level, and this detailed information was used in the calculation procedure.

Although the work related accidents and damages are sorted and registered into 15, respectively 18 different categories, only nine categories are used in the calculations. The reason for this is that the frequency of some types of damages is very low, causing uncertainties in the subsequent interpretation of the results. The included impact categories are:

Accidents

Diseases

11.2.5 Step 5 - Calculating the impacts per functional unit (weight unit)

The seventh and final step is to calculate the working environmental impacts per functional unit by dividing the information from step 4 with the information from step 3.

In order to minimise the statistical uncertainties, an average for the years 1995-1997 is used for both the produced amounts and the accidents/damages in a sector.

11.3 Discussion

The methodology outlined in the paper exemplifies that it is possible to combine information from two statistical sources in an input/output analysis in order to produce meaningful results in a LCA.

When the inventory calculations have been made, it is possible to obtain an overview of what processes or materials contribute most to each of the impact categories. It is also possible to present figures for the absolute contribution to the different impacts, e.g. how many accidents can be expected during the production of an office chair. Following normalisation, where the impacts in the life cycle of the products are compared to the average work-related impacts on a Danish citizen, it can be demonstrated what working environmental impacts are most affected

Obviously, the results should be interpreted in view of the inherent uncertainties. A major uncertainty in relation to LCA is that average values for large sectors are used in the calculations. Thus it is not possible to achieve or use knowledge about the working environmental impacts from specific companies. However, the goal of the methodology, i.e. to give the possibility of examining whether environmental product improvements are implemented at the expense of a deteriorated working environment, is fulfilled by the methodology.

The method is recommended as a general assessment of the changes in working environmental impacts induced by changes in the choice of materials and processes. This knowledge can subsequently be combined with more specific knowledge about potential hazards in relevant sectors and form the basis for a dialogue between the actors in a product chain. WE-LCA can thus be seen as a natural component in the efforts for development of products with less impact on the environment and human health.

In relation to the use of available statistics for other LCA-purposes, the procedure for calculation of produced amounts outlined in the present paper is recommended. The produced amounts can be calculated for about 300 sectors with a relatively high degree of precision. This gives the possibility of relating information on different types of environmental impacts to a wide variety of sectors and – eventually – also to a large number of product groups. However, neither the level of detail nor the precision can match that obtained by performing a regular LCA.

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