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Weighting Method
Principal MethodName:
Distance to target (DtT)

This weighting method is going to be removed
Method Description:
Normalization assists in assessing which of the potential impacts are large and which are small, by placing them in relation to the impacts from an average person in 1990. But even if the potential impacts for two different impact categories are equally large on normalization, this does not automatically mean that the two potential impacts are equally serious. To be able to compare the potentials for the various impacts, an assessment must first be made of the seriousness of the impact categories relative to one another.

The mutual seriousness of the impact categories is expressed in a set of weighting factors with one factor per impact category within each of the main groups environment, resources and working environment.

The weighting can then be made by multiplying the normalized impact potential or resource consumption, NP(j), by the weighting factor, WF(j), associated with the impact category or resource consumption in question, and the weighted impact potential or resource consumption WP(j) is therefore calculated as:



Where P(j) is either EP(j), RC(j) or WP(j).

Weighting of environmental impact potentials

The weighting factor for an environmental impact must reflect the seriousness of the effect potentially being caused by the impact and the possible consequences of this effect relative to the other environmental effects. The seriousness depends on several characteristics of the environmental effect and the actual condition of the environment. Some of these characteristics are of a purely scientific nature and they should be evaluated in the same way, irrespective of the use to which the LCA will be put. Examples of scientific characteristics include:

How far is the actual impact status from critical threshold values for the impact in the areas affected by the emission?
What types of consequences will result if these threshold values are exceeded?
Will the environmental damage be reversible?
How great an area will be affected by the damage?

Other characteristics are of a more normative or political nature, and depend on the context into which the LCA will enter. If the LCA is to be used by a company to prioritise an initiative in relation to a particular market, normative questions could, for example, be:

What is the perception of the seriousness of the environmental effect among potential buyers of the product or among others of the company's interested parties?
What is the perception among various opinion-leaders in the community in general?

If the LCA is to be used by the authorities, for example to set criteria for assigning an environmental label for this product type, normative questions could be:

What current political plans of action exist for reduction of the impacts which lead to the environmental effect?
What international regulations exist in the area?
The EDIP method's weighting factors were not developed as described above, on the basis of purely scientific weightings followed by more normative weightings. The basis of knowledge of the individual impact categories is simply not good enough to enable such sharp definition of a purely scientific and a more normative weighting. When the above considerations concerning weighting are discussed here, it is to indicate that it is this type of consideration which in principle should be expressed in the weighting factors.
The EDIP method instead seeks to fix the weighting factors so that they:
• as far as possible for each individual environmental impact reflect the scientific circumstances and the relevant normative circumstances in one,
• reflect the official societal priorities as well as possible,
• give the company the best possible assurance of how the impact categories will be ranked by the authorities in the future.
This is achieved by using political environmental targets within the field of each individual impact category as a basis for the weighting.

Weighting on the basis of political environmental targets

The authorities' regulation of society's impact on the environment has naturally enough been focused on those activities which have the greatest environmental impacts. International agreements and nations plans of action have set reduction targets for society's impacts on the environment. Today there are thus politically determined targets for reductions in the most significant contributions to all of the impact categories treated by the EDIP method.

When targets are set for reductions in society's environments impact, this is based on considerations of how serious the consequences of the impact can be, and the costs which will be associated with reducing them. The considerations include such issues as:

• What damage to the environment can be observed today as consequence of the impact?
• What damage to the environment can be expected as a consequence of the impact, and what environmental consequences can result in the short and the long term?
• What costs will this damage impose on society?
• What technological possibilities are available for preventing and repairing the damage?
• Is the public aware of the environmental effect?
• How will the planned measures against the impact affect the national and the international economies and employment?

As a rule, scientific research on an environmental effect would have been going on for a long time before plans of action are initiated or targets for reduction adopted. Plans of action and targets for reductions thus usually have a substantial scientific background.

For the individual environmental impact category, the political setting of reduction targets therefore implies a balancing of scientific, technical and political considerations. No conscious balancing of the seriousness of this environmental impact is made relative to the seriousness of the other impacts to which the environment is exposed. But the targets for reductions are set within society's total economic framework for environmental improvements, and the initiative regarding individual substances and groups of substances is therefore indirectly ranked in relation to the total environmental measures.

On this basis, the political setting of reduction targets can be considered a result of a decision-making process similar to that which should underlie the determination of weighting factors for the environmental impact categories.

The situation is such that

• the authorities have set reduction targets for the most significant of the emissions which contribute to the impact categories entering into the EDIP method,
• many authorities desire a product-oriented environmental policy as a central part of their environmental administration, and thus as a significant means of achieving the reduction targets which have been set.

This argues strongly for determining the weighting factors on the basis of political reduction targets. The authorities will not be able to defend environmental priorities for the product policy other than those which can be deduced from the reduction targets, for in such case the reduction targets from action plans, agreements, etc. and the product-oriented environmental policy will each pull in its own direction. But by using this way of determining weighting factors, the authorities have a powerful instrument to ensure that companies have the correct environmental priorities when developing new products. If the societal reduction targets are changed for certain impacts, the changes can be transferred accordingly to the corresponding weightings in the product-oriented environmental policy. The weighting factors must therefore be adjusted at intervals, for example every fifth year together with the normalization references, to keep them in accordance with the current reduction targets.

In determination of weighting factors for the individual impact categories, the EDIP method is based on the existing Danish political targets for reduction of various categories of environmental impacts.
Political targets for reductions are normally set-for individual substances or groups of substances and not for total contributions to environmental impacts. For example, there is a target in many countries for reduction of society's emissions of CO2, which is the most significant greenhouse gas, but not for a reduction in society's total contribution to the global warming impact, which is also attributable to substances other than CO2. The reduction targets for individual substances can, however, be translated into reduction targets for environmental impacts with the aid of the equivalency factors in the same way that the inventory of environmental exchanges for a product system can be translated into environmental impact potentials.

As a rule, the reduction targets are formulated such that society's emissions of a substance or a group of substances in the selected target year may amount at most to a certain percentage of the emissions in a reference year. But reference year and target year vary for the various substances and groups of substances) depending on the time when the reduction targets are set, and also on the desirable and realistic time frame for achievement of the reductions.

To give a uniform treatment of all environmental impact categories, the reduction targets as harmonized in the EDIP method to apply to the same period for all environmental impact categories before they are used as a basis for calculation of the weighting factors.

Because of the requirement which has arisen for the environmental assessment of products, it can be expected that more work will be directed towards the basis of weighting in the future.


The year 2000 was chosen as the common target year, while 1990, the normalization references' inventory year) was chosen as the common reference year.

An estimate is made of the magnitude of the extrapolation if the target year is before 2000) as target emission if the target year had been 2000. The estimate is made by linear interpolation if the actual target year is beyond 2000.

The weighting factor WF(j) for the type of environmental impact category (j) is defined as the environmental impact potential of the emissions in the reference year 1990, ER(j)90 divided by the environmental impact potential of the target emissions in the year 2000, ER(j)T2000.

WF(j)=Environmental impact potential of emissions in 1990/Envrionmental impact potential of target emission for the year 2000

That is:


The weighting factor thus expresses by how much the normalization reference must be reduced by the year 2000 to be in accordance with the efforts expressed by the reduction targets for the environmental impact in question. The sharper the reduction targets, the greater the weighting factor for the environmental impact.

The choices of target year, reference year and method of interpolation are not objective. They could be selected differently, and this will be of significance for the relative magnitudes of the individual weighting factors. The target year must, however, lie a suitable number of years in the future, so that the weighting factors provide a certain assurance of how the impact categories will be ranked relative to one another when the product eventually enters the market.

With the chosen definition of weighting factor, the weighting can be seen as a type of normalization with the target emissions in the year 2000 as normalization reference, as the weighted environmental impact potential WEP(j) is determined as:




In other words, the weighted environmental impact potential for the product is expressed as a percentage of the person-equivalent which can be expected in the year 2000 if society's plans for reduction are achieved.

The unit is PETWDK2000, which stands for person-equivalent based on target emissions in the year 2000. WDK stands for the weighting of global impact categories on the basis of the accepted global contributions in the year 2000, while the regional and the local impact categories are weighted on the basis of the accepted contributions in Denmark. The word "accepted" should not be taken too literally. It is not supported by statutory requirements, but by national and international conventions and plans of action for the extent of reductions by the year 2000.

Region-specific considerations

The EDIP method admits the option of including region-specific factors in the weighting of regional and local impact categories. Normalization reference and weighting factors are available today only for Denmark and for certain impact categories for the EU, but the method is open to future developments within the area.

From an environmental viewpoint, the weighting should take account of region-specific factors so that the non-global impact potentials are weighted with the acceptable person-equivalent for the area which they affect. The environmentally acceptable person-equivalent is equivalent to the environmental latitude, i.e. the average impact which is acceptable for a person in a sustainable society. When the potential environmental impacts are weighted in this way, they are expressed as fractions of the environmental latitude available in the places where the environmental impacts occur.

The product system can have ramifications in many places on earth, and a region-specific weighting carried out on the potential environmental impacts will therefore require a comprehensive file of environmentally acceptable person-equivalences. A more operational solution could be that for each impact category, all countries on earth are divided up into a limited number of sensitivity classes based on the countries' population densities, technological level and the sensitivity of their natural environments, The task is thus reduced to determining environmentally acceptable person-equivalents for each of these sensitivity classes.

In the absence of regionally determined values for the environmentally acceptable person-equivalent, the second best solution could be politically set reduction targets for environmental impacts in the various regions. The level of environmental ambition reflected by environmental policy is, however, highly diverse in different parts of the world, and this will introduce some uncontrolled distortions in the weighting. For this reason, weighting factors based on Danish environmental policy as described above are being used for the time being.

Weighting of resource consumption

"The weighting factor for a resource must reflect how scarce the resource is relative to consumption of it, i.e. the size of known reserves relative to annual consumption of the resource. This is called the "supply horizon" and it provides a measure of the resource's scarcity.

The supply horizon for a non-renewable resource is the number of years for which current consumption of the resource can continue before known reserves are exhausted. The scarcer the resource relative to consumption, the shorter is the supply horizon. For non-renewable resources the supply horizon can be long or short, but it is always finite. If there is consumption of the resource, reserves will not last forever.
For renewable resources which are not consumed faster than their rate of regeneration, it is meaningless to speak of a supply horizon. If the resource is not plundered, it can in theory be used forever, i.e. the "supply horizon" is infinite. But there can be regions where current use exceeds regeneration. This is the case for forests in large parts of the earth's tropical regions, where the original forest is being cleared and the forested area reduced year by year. A more local example is consumption of water in Denmark. In Denmark's capital city area, the groundwater resource is being overused because of extraction of drinking water, and use of groundwater should therefore be weighted more heavily than if it occurred in Ringkobing County in western Jutland, where extraction of groundwater is much less than regeneration of groundwater.

If a renewable resource is consumed more quickly than it is regenerated, the supply horizon can be defined as the number of years which will elapse before the resource is exhausted at the current ratio between present reserves and the difference between rate of consumption and rate of regeneration. The supply horizon for renewable resources is thus defined on the basis of actual consumption in the local areas where consumption is occurring:


The EDIP method defines the weighting factor for resource consumption as the reciprocal of the supply horizon for the resource, calculated on the basis of consumption, computed reserves and any rate of regeneration in the reference year 1990.

For renewable resources, the weighting factor is defined on the basis of the total consumption where the process is occurring. If the resource is not used faster than it is regenerated, the supply horizon is infinite and the weighting factor is therefore zero.

For non-renewable resources, this definition of the weighting factor means that consumption, R(j), of resource (j) in the product system is compared against reserves of the resource in question at the weighting. The weighted resource consumption, WR(j), is found as:


The weighted resource consumption is given the unit “person-reserve” , PRW90, i.e. the proportion of known reserves per person in the world in 1990, where 'W stands for the world. The weighted resource consumption is typically expressed in mPRw90 and the product's consumption is thus expressed in parts per thousand of known person-reserves in 1990.
Weighting of potentials for impacts on the working environment

The weighting factors for the impact categories for the working environment should reflect the seriousness of the individual types of impacts, as do the weighting factors for the environmental impact categories. The seriousness of an impact category for the working environment is determined by
• the probability that an impact actually results in a work injury, and
• the seriousness of the consequences of such a work injury for the employee.


In the EDIP method, the weighting factor is calculated for each individual type of working environment impact as the relationship between the number of work-related injuries reported for persons exposed to the type of impact in question in Denmark and the total time of exposure in Denmark to the relevant type of impact
in the years around 1990.

The weighting factor expresses the annual average number of work injuries per employee in Denmark per annum for the impact category in question.

The weighted potential for impacts on the working environment WWP(j), is determined as


With this definition of the weighting factor, the weighted potential for impacts on the working environment can be interpreted as a measure of the number of work injuries within the relevant category of impact to be expected as a result of the product system. In the weighting, the potentials for impacts on the working environment are expressed in the unit RWIDK90, reported work injuries based on inventories for Denmark in the years around 1990. Note that the weighting factor with this definition includes only the first of the two aspects noted at the beginning of the section. The seriousness of the consequences of various types of work injuries is difficult to quantify, and it is not attempted in the EDIP method. This is discussed in the section on interpretation of potentials for impacts on the working environment.

Interpretation of weighted impact potentials and resource consumptions

Environmental impact potentials and the environmental space determined by political targets

In the weighting, the environmental impact potentials are expressed as proportions of the person-equivalent corresponding to the policy target for environmental impact in the year 2000. The weighted environmental
impact potentials are measured in PETWDK2000, which stands for the person-equivalent based on target emissions for the world (W) or Denmark (DK) in the year 2000.

As introduced the "environmental space" is the environmental impact available on average to each person in a sustainable society. In the same way, the "environmental space determined by policy targets" for the year 2000 can be defined as the impact which we on average may cause if the targets for reductions are to be fulfilled. The size of the latitude determined by environmental policy targets will gradually approximate the size of the environmental space as the environmental policy targets approximate the requirements for sustainability.

A contribution to acidification of I PETDK2000 is equal to the average annual impact of acidifying substances which can be expected per Dane in the year 2000 if present reduction targets for emissions of acidifying substances are fulfilled. Thus, 1 PETDk2000 can be regarded as the politically-determined environmental space for each individual impact.

This figure is immediately comprehensible. If one buys a car with a global warming potential of 500 mPETW2000, half of one's "ration" for the contribution to global warming has been used for all of the time during which the car is in use.

As discussed above, the weighted environmental impact potential is suitable for supporting decisions because it represents the product's potential impact relative to the best prediction of the community’s future priorities within the environmental field.

Resource consumption and known reserves

In the weighting, resource consumptions are expressed relative to the average global reserves per person in 1990, and they are expressed in the unit PRw90, PR for person-reserve, W for world because the reserves are computed for the entire world, and 90 because the reserves are computed as known quantities in 1990.

These figures are also immediately comprehensible. For example, with a figure of 10 mPRw90, it is possible to buy 100 products of the relevant type, and the "ration" of known reserves has thus been used for the entire future for all generations, i.e. also that portion of the known reserves which were otherwise available for one's children, grandchildren and subsequent generations.

In the weighting of resource consumption, a number of factors apart from the scarcity of the resource can be considered as supplementary weighting criteria:
• Irreversible versus reversible consumption: fossil fuels are burned and disappear entirely as resources, while metals, for example, are only made inaccessible in landfills with some possibility of future recovery. If the consumption is reversible, the weighting can take account of the magnitude of the energy consumption required for regeneration of the resource, for example on a later recovery of the resource from a landfill.

• Usability: oil has more possible uses than other fossil resources such as coal and gas.

• Substitutability: certain metals can be more difficult than others to replace and to do without for the industrialized world, because they are essential to certain applications.

The significance of the above three circumstances is difficult to quantify, and it is not attempted in the EDIP method. The weighting of resource consumption only includes the scarcity on the basis of consumption relative to the size of reserves, and the various resources are accorded an equally large value. In presentation of the weighted resource consumption, care must be taken to ensure that the decision maker knows the weighting principle, and has been presented with the above "missing" weightings.

It should also be noted that the size of the reserves is not absolute, but depends to a high degree on the market price of the resource and on its strategic significance. The more expensive or important the resource, the more intensively it is sought, the more inaccessible the places on earth where it is sought, and the greater is the environmental impact per unit of resource extracted. The known reserves of crude oil have thus been more or less constant over the last few decades despite a continuing large consumption of the resource.

In spite of this situation, the supply horizon defined on the basis of the size of known reserves is the best measure we have for the scarcity of the resource, and thus the best option at present for a weighting factor for resource consumption.

Potential impacts on the working environment and reported work injuries

In the weighting, a potential for impacts on the working environment is expressed as the number of reported work injuries to be expected as a result of the potential. The expectation is based on the relationship which can actually be confirmed between impacts on the working environment and the frequency of reports of work injuries in Denmark. The weighted potentials for impacts on the working environment for the product can thus be interpreted as a measure of the number of work injuries to be expected under Danish conditions as a consequence of the product system. The weighted potentials for impacts on the working environment are expressed in the unit RWIDK90~ reported work injuries in Denmark.
In the weighting of potentials for impacts on the working environment, there are also several other considerations which should be accorded weight, possibly as supplementary weighting criteria:

As the weighting factor is defined above, it does not take account of the fact that the various types of injuries are not equally serious.

The frequency of reporting can vary for the various categories of impacts on the working environment. Allergy is often recorded immediately after the impact which triggered it, and it is therefore easier to identify as an impact on the working environment than cancer, which is only observed years after the impact which triggered it. This means that the impact categories with the lowest relative frequency of reporting are weighted too highly with the weighting factor defined above. For these impact categories, a greater number of work injuries must be expected than predicted by the weighted working environment profile.

• For the types of effects recognized only long after the working environment impact which triggered them, the weighting factor does not reflect the impact in 1990, but for e.g. carcinogenic effects the impact 10-20 years earlier. It can be expected that the total impact on the working environment has changed since then. If the exposure to these impacts on the working environment has decreased in Denmark over the last few decades, the corresponding impact categories are weighted too heavily. If the exposure has increased, they are weighted too lightly.

• When using sector data, the impacts on the working environment are computed directly as reported work injuries. These can include region-dependent distortions in the weighting of various impacts, as the frequency of reporting will be lower for occupational diseases in many developing countries than in industrialized countries. The significance of these considerations is difficult to quantify, and it has not been attempted in the EDIP method. In the presentation of
the working environment profiles, care must be taken to ensure that the decision maker knows the weighting principle and is informed of the existence of these other weighting criteria.

There are, however, very large differences in the weighting factors for resource consumption and potentials for impacts on the working environment. These differences reflect the fact that some resources are much more scarce than others, and that some types of impacts on the working environment result in reported work injuries much more frequently than others.

Consumption of copper is thus more serious than consumption of coal for the production of the electricity used by the TV. A large normalized consumption of water for the high pressure cleaner disappears in the weighting, because a renewable resource is involved which for the areas where the cleaner is used may on average be assumed to be consumed more slowly than it is regenerated. Hearing impairment, injury to the musculo skeletal apparatus and accidents are all working environment effects which are relatively simple to relate to an impact on the working environment, and they gain significance relative to the other impact categories of the working environment in the weighting.

Weighting by company policy

As a final step in weighting, the EDIP method permits a further weighting based on the company's environmental policy. This may be particularly useful when the method is applied in product development or in the company's environmental management. The company's environmental policy must then be expressed in a set of weighting factors.
When a weighting expressing company policy is included, it is possible to let the results of the LCA reflect the priorities determined by management in the company's environmental policy. The LCA thereby becomes a powerful tool in the company's environmental management.

At the same time, the LCA ceases to be in agreement with the authorities' priorities. This will affect public acceptance of the use of company-specific weightings.

If a final company policy weighting is included, it is therefore important:
• That the profiles for environment, resources and working environment are always shown both with and without the company policy weighting.
• That account is taken of where the company policy weighting enters, and how it affects the result.

Literature Reference:
Henrik Wenzel, Michael Hauschild and Leo Alting (1997 ): Environmental assessment of products Vol. 1 Methodology, tools and case studies in product development London Chapman & Hall
Methodological Range:
Geographical range is Denmark and Europe
Temporal range 1990~2000

Weighting Factors
Category Indicator name Quantity Unit Note
Aluminium consumption (EDIP/1997) 1 /kg
Antimony consumption (EDIP/1997) 1 /kg
Beryllium consumption (EDIP/1997) 1 /kg
Brown coal consumption (EDIP/1997) 1 /kg
Cadmium consumption (EDIP/1997) 1 /kg
Cerium consumption (EDIP/1997) 1 /kg
Coal consumption (EDIP/1997) 1 /kg
Cobalt consumption (EDIP/1997) 1 /kg
Copper consumption (EDIP/1997) 1 /kg
EF(ac) (EDIP/1997) 1.3 /kg
EF(etp) (EDIP/1997) 2.4 /m3
EF(etsc) (EDIP/1997) 2.4 /m3
EF(etwa) (EDIP/1997) 2.4 /m3
EF(etwc) (EDIP/1997) 2.4 /m3
EF(hta) (EDIP/1997) 2.4 /m3
EF(hts) (EDIP/1997) 2.7 /m3
EF(htw) (EDIP/1997) 2.7 /m3
EF(N) (EDIP/1997) 1.3 /kg
EF(ne) (EDIP/1997) 1.2 /kg
EF(P) (EDIP/1997) 1.0 /kg
EF(po) (EDIP/1997) 1.2 /kg
Gold consumption (EDIP/1997) 1 /kg
GWP (EDIP/1997) 1.3 /kg
Iron consumption (EDIP/1997) 1 /kg
Lanthanum consumption (EDIP/1997) 1 /kg
Lead consumption (EDIP/1997) 1 /kg
Manganese consumption (EDIP/1997) 1 /kg
Mercury consumption (EDIP/1997) 1 /kg
Molybdenum consumption (EDIP/1997) 1 /kg
Natural gas consumption (EDIP/1997) 1 /kg
Nickel consumption (EDIP/1997) 1 /kg
ODP (EDIP/1997) 23 /kg
Oil consumption (EDIP/1997) 1 /kg
Palladium consumption (EDIP/1997) 1 /kg
Platinum consumption (EDIP/1997) 1 /kg
Silver consumption (EDIP/1997) 1 /kg
Tantalum consumption (EDIP/1997) 1 /kg
Tin consumption (EDIP/1997) 1 /kg
Wood consumption (EDIP/1997) 1 /m3
Zinc consumption (EDIP/1997) 1 /kg