| Front page | | Contents | | Previous | | Next |

Waste Indicators

4 Calculation method and assumptions

In this chapter the general assumptions for the calculation method for the indicators, resources, energy and landfill requirement are presented. In addition, data for the relevant treatment options for paper, glass and aluminium, serving as calculation examples, are reviewed. In Appendix C concrete data and assumptions for the indicator calculations are reviewed in more detail for each of the three examples.

4.1 Calculation method and assumptions for indicators

In the calculation of indicator values, waste quantities for the individual fraction and treatment option are multiplied by the related LCA impact factor. This is done for each of the three indicators.

The starting point for indicator calculations is quantitative data and indicator factors, both structured as in the below Table 4.1. The contents in each cell in the table with quantitative data (Table 5.1) are multiplied by the corresponding indicator factor (Table 4.3). The calculated values for each indicator are added together into a collective indicator value for the management of a material fraction. See the example in Table 4.1, where the quantity of glass packaging (in 1998), disposed of in different ways, is multiplied by the corresponding factors. The results for each of the four treatment options are added together and constitute the resource indicator value for waste management of glass. Indicator values for primary energy and landfill requirement are calculated in a similar way.

Table 4.1
Example of indicator calculation for glass packaging, 1998

Indicator factors are based on life-cycle data for the individual material and on data for waste management of materials. In the following the most essential assumptions in the statement of quantitative data and for calculation of factors for the different fractions are summed up.

As stated in Chapter 2, the grouping of materials is not necessarily identical to waste fractions in the ISAG. The waste fraction "paper and cardboard" in the ISAG only covers paper and cardboard collected for recycling, whereas other paper is included in mixed fractions, for example "burnable waste". For the material "paper" it will be necessary to make an estimate of total quantities of paper, including the amount of paper and cardboard included in the mixed waste fractions for incineration or landfilling.

In order to carry out calculations for all waste fractions it is necessary to break down the mixed waste fractions into material fractions. The composition of, for example, "burnable waste" thus must be broken down into material fractions such as: paper and cardboard, plastic, glass, different metals, compostable waste, etc. which to a certain extent can be done based on different data sources, and for some fractions based on estimates.

Thus part of the assessment of the extent of an indicator calculation for the entire waste management field is also to determine how it is possible to break down waste into material fractions on the basis of ISAG statistics and other accessible data. It must be anticipated that the break-down of mixed material fractions can only be carried out every five or ten years, so that in the intervening periods constant distributions of the fractions are used.

If indicators are to be used to follow developments from one year to the next, it is essential to ensure that indicators are sensitive to the differences that may be extracted from annual statistics (the ISAG and supplementary statistics), and not only reflect developments in total waste quantities.

For the three materials for which calculations have been carried out, it has been possible to provide data by combining ISAG statistics with other data sources (see Appendix C).

4.1.2 LCA data and allocation of recycled materials

The establishment of the three factors of resources, energy and landfill requirement is based on the fact that material taken out of circulation upon disposal must be substituted with virgin primary material (see Chapter 2.3). Thus, if 1 kg of glass is landfilled, 1 kg of virgin glass must be manufactured, which is a defendable consideration as long as society has a constant or increasing consumption, which is the case for paper and cardboard, glass and aluminium.

In addition, if it is a question of waste treatment of recycled materials, some of the value of this material will be lost in the previous use. To take this into account, the EDIP project’s loss of utility value (see Glossary) has been applied. Thus, for each material the extent to which the landfilled/incinerated material consists of recycled material has been assessed. For example, in Table 4.2 it is stated that paper and cardboard is a mixture of primary/recycled paper and cardboard – an estimated 50/50 distribution for the parts incinerated/landfilled. For the recycled part there has already been 20% loss of utility value, which is why in total there is only 90% loss of resources of paper consumption upon landfilling/incineration. For paper going to recycling, in return, a 20% loss of utility value is used in the calculation, which appears as a loss of 20% assigned to landfilling. A large part concerns filler materials in the paper.

Calculations are based on data from the EDIP project and the EDIP PC tool database. Unit processes are designed in general so that they add together resource consumption and environmental impact from the production of 1 kg of material. By considering the system from a waste disposal perspective it has therefore been necessary to adapt unit processes in cases where there is a material loss from recycling. For example, the unit process in the EDIP PC tool database /8/ shows that around 1.15 kg of paper is used for the production of 1 kg of recycled paper. This means that 1 kg of waste paper for recycling only gives 0.87 kg of recycled paper, and therefore an additional production of 0.13 kg primary paper is required before the system balances.

For all materials, statistics on quantities collected for recycling cannot indicate whether material collected is from recycled or primary materials. Therefore in most cases it has been necessary to calculate with estimated mixtures of primary and recycled materials.

For aluminium there is the special situation that upon incineration aluminium oxide is formed as a residue. Residues are around double the quantity incinerated, which is the reason for the value 190% for landfilling upon incineration of aluminium. This assumption derives from the EDIP project’s data on incineration of aluminium. Subsequently the issue has been investigated, and it has appeared that most aluminium for incineration is not ignited, but just ends up in slag. Therefore, the value should be adjusted downwards in a subsequent indicator calculation for the entire waste management field. Similarly, the value of 10% for loss of utility value for glass, also deriving from the EDIP, may be too high and should be investigated in a later survey.

The specific percentages applied to the different materials and disposal processes are stated in Table 4.2 and explained in Appendix C. Table 4.3 shows factors deriving from the calculations. Values from the tables are illustrated in graphic form in Chapter 5, and results are commented on.

Table 4.2
Table with outline of unit processes and percentages used

4.2 New LCA data

When the calculation examples were made, it was necessary to a minor extent to update or provide new data.

The basic principle in the EDIP method used to calculate the LCA-based indicators is that items are made comparable by converting resource consumption and environmental impacts into person-equivalents (see Glossary). Normalised values thus achieved can then be multiplied by a weighting factor stating to which extent the resource consumption or the environmental impact in question is considered problematic.

Neither the EDIP project nor the EDIP PC tool database contains normalisation references or weighting factors for energy consumption or for landfill requirement for total waste quantities.

Table 4.3
Calculated factors (normalised)

In the calculation of indicators, weighting is omitted of normalised data, as it would not make sense to aggregate them further. In particular it is not expedient to gather the factors resources and energy into one indicator, as the former also covers energy resources, meaning that an aggregation would count energy twice. Furthermore, a weighting would cause unnecessary discussion of the validity of indicators.

The lack of weighting means that indicators based on the three parameters are to be considered as a set of indicators, where much caution should be taken in making comparisons between the three indicators.

Another practical function of the normalisation of indicators is the fact that indicators may be presented on the same scale (and thus in the same figure), and that in some contexts it is easier to explain their meaning. If the purpose is just to obtain the same scale it would also be possible to index indicators. This would make it possible to put them on the same scale without a prior normalisation – but conversely normalisation would not prevent a subsequent indexation. In the presentation of results in Chapter 5, both approaches are used.

4.2.1 Normalised resource consumption

Resource consumption associated with the processes covered by the calculation is first stated in absolute figures in the unit tonnes. To allow for comparison and aggregation of consumption of several raw materials, a calculation method has been developed under the EDIP method, where the consumption of each single raw material is related to the size of the reserve.

In the EDIP method the term "weighted resource consumption" stated in person reserves is used (see Glossary). In reality this corresponds to normalising in relation to global reserves, for metals and minerals for which statements of global reserves are available.

For the renewable resources wood and water, the EDIP method uses local normalisation references based on an assessment of present consumption and supply perspective in a continuous depletion of reserves. For example, supply perspectives for wood and groundwater have been set at several hundred years, so such renewable resources will normally not dominate statements.

In Table 4.3 the total value for renewable and non-renewable resources is shown, but calculations are made so that results may be divided into the two groups by checking in the result tables of Appendix D (not translated).

For sand, gravel and other minerals extracted and used regionally, there are generally no statements of global reserves in the EDIP/the EDIP PC tool database, and therefore in this project it has been relevant to make an estimate for some of these resources: sand and gravel as well as sulphur in its pure form. For sand and gravel the study indicated that factors for these in comparison to other resources will be very insignificant. Considerations of this issue are stated in Appendix C.

4.2.2 Normalisation of energy consumption

Energy consumption for different processes cannot be found directly in the EDIP PC tool database, as energy consumption in the EDIP method is represented with associated resource consumption and environmental impacts. The primary energy consumption (see Glossary) for processes covered by the calculation can be calculated, however, on the basis of calorific value of energy resources used. In the conversion, a distinction has been made between renewable and non-renewable energy resources, and data for each single resource can be found in the background material. Only a total value has been shown in Table 4.3. The normalisation reference for energy consumption is calculated on the basis of Danish total primary energy consumption in 1998.

Concerning waste incineration it has been relevant to estimate the specific consequences of waste incineration for primary energy consumption at other energy supply plants supplying power and heating in Denmark. Considerations to this effect are part of the EDIP project, but it has been necessary to update data in connection with this project, as for some materials it may be a decisive parameter. At the same time, in recent years large changes have taken place in the area. Calculations and underlying considerations are discussed in Appendix C.

4.2.3 Landfill requirement

First, landfill requirement is stated in absolute figures in tonnes. In the EDIP there are four different categories of waste to landfill, normalised in relation to total waste quantities for each of the four waste categories. For the indicator calculations it has been decided to establish a collective landfill factor for all fractions as a whole. The normalisation reference for landfilling is set at total landfill requirement in Denmark in 1999.

It may seem unnecessary to state landfill requirement as an independent parameter, as total quantities landfilled already appear from waste statistics. However, another entity is calculated here, since landfill requirement is calculated in a life-cycle perspective. This means that, for example, landfilling of waste from extraction of raw materials is also included in landfill requirement.

A drawback of this indicator, however, is that landfilling of 1 kg is calculated with the same value whether the material landfilled is lead or glass. As long as in the LCA-context no weighting factor (based on impact factors) has been developed that can be used to state the degree of problems relating to landfilling of the different materials, it is beyond the scope of this trial to make a weighting. The EDIP project’s division into four categories cannot solve this problem either, so we have chosen to just calculate one overall value for landfilling.

4.3 Calculation in practice

Environmental impacts and resource loss upon landfilling and alternative treatment options are calculated on the basis of EDIP data using a database programme that can calculate and manage the many intermediate results. For this purpose a programme has been used that has been developed by I/S ØkoAnalyse in connection with the project "Environmental impacts in the family" /14/.

The calculation is carried out so that the different contributions to all parameters for environmental impact and resource use can be traced back to the different processes. In Appendix D (not translated) tables are presented of unit processes and waste quantities included in the calculations. Other tables show characterised and normalised values (see Glossary) for the three indicators, distributed on the three material fractions, both for kilos of waste and for total waste quantities.

After an assessment of data quality, an aggregation has been made of the selected factors stated in Table 4.3. This makes it possible to survey whether significant contributions are missing. Once the assessment has been made, it is possible to use the aggregated data for calculating resource, energy and the landfill factors for the different materials to be multiplied by the relevant waste quantities.

For the different forms of presentation of the results – including the two basically different models, a further calculation has been made of the calculated factors and amounts in a spreadsheet. Appendix D (not translated) presents data used and results, and it is also possible to find results broken down into energy resources and other resources, as well as renewable and non-renewable sources of energy.