Miljøprojekt, 971 – Livscyklusvurdering af deponeret affald

Lifecycle Assessment of Depositied Waste

Summary and conclusion

Part I (Subproject 1)
Part II (Subproject 2)
Area use and resource use
Conclusion

In life cycle assessments according to the EDIP –method (Environmental Design of Industrial Products), the deposit of waste, including residue products from incineration, has up till now been calculated only as an amount of waste in one of the four categories:

bulky waste (not dangerous)
dangerous waste
slag and ashes
radioactive waste

This means that potential environmental impacts caused by the deposit of waste have not been considered. The aim of this project is to develop a method that makes it possible to incorporate the potential environmental impacts. The environmental impacts from the deposit of waste derive from:

Emissions
- from deposited waste
- from processes related to operation etc. of the deposit plant
  (e.g. transport of waste to deposit plant, digging of cells)
Resource use related to e.g. operation of deposit plants and treatment of residue products
Occupation of an area of land.

In Denmark as well as internationally, in connection with LCA there is a certain agreement that emissions from deposit plants should be evaluated from two different perspectives:

What will happen in the first 100 years ("foreseeable future")?
What will happen in the long term - in principle an indefinitely long term?

The two sub-projects, carried out as a part of this project, cover point 1. and 2. respectively.

Part I (Sub-project 1)

Part I of this report covers sub-project 1, which includes mapping of data for treatment and deposit of residue products from incineration and residues from combined power-heat production. Furthermore, principles for calculation of product specific emissions in the first 100 years after deposit as well as principles for incorporation of land use as an environmental impact category. In data mapping and in the calculation principles, the percolate from different methods of recycling of the residue products is addressed in parallel to deposit. Originally, the deposit of waste not suitable for incineration was included. However, this type of waste turned out to vary too much in order to develop general product specific models for emissions from waste deposits.

The models and the development of methods in this project are based on existing surveys and models developed by COWI, Danish Hydraulic Institute (DHI), the Institute for Product Development (IPU) and Techwise A/S.

The environmental effects, which have not been considered satisfactorily in the existing method, are the emissions of persistent toxic substances and land use (which is, however, represented by an amount of deposited waste). It has, thus, been decided both - as part of this report - to calculate product specific emissions from deposit plants in the first 100 years and their potential contribution to toxic effects, and to introduce to new effect categories - deposited human toxicity and deposited eco-toxicity – which, together, represent the environmental impact of the deposit plant in a longer perspective.

These effect categories are described further in sub-project 2 (see the following). Furthermore, it has been decided to let the land use be expressed by the occupied area of land multiplied by the time of occupation.

The data mapping has, thus, been focused on emissions of persistent toxic substances, especially metals. Data for metals are, indeed, available.. The other types of compounds (especially salts) where accessible data has been found, have not been estimated to have any considerable environmental impacts. The survey of emissions from deposited waste fractions has primarily been made by method development based on a comparison of theoretical knowledge and actual observations of percolate from deposit plants (if they exist) and results of laboratory percolation tests on the deposited materials.

The substances included in waste incineration are Cadmium (Cd), Chromium (Cr), Copper (Cu), Lead (Pb), Arsenic (As), Nickel (Ni) and Zinc (Zn). For the substances Aluminium (Al), Barium (Ba), Molybdenum (Mo), Antimony (Sb), Selenium (Se) is has not been possible to make the calculation for the entire system due to lack of data from sub-processes.

For energy production the following substances are included: Cadmium (Cd), Chromium (Cr), Arsenic (As), Molybdenum (Mo), Selenium (Se), Vanadium (V), Magnesium (Mg), Lead (Pb) and Zinc (Zn).

It has been evaluated that the most problematic substances are included, but it cannot be excluded that emissions from other substances may contribute considerably to the environmental impact. During the completion of the project it has turned out that the amount of metals that are washed out during the first 100 years is only a very small part (0.00006-0.2%) of the amount that the residue products contain. By calculation, this small part, however, has some importance for the impact categories and their toxicity. If an LCA includes a product that contains one or several of the seven metals, it is recommended to include the leachate in the first 100 years by using the developed model.

To a large extent this project is based on the very relevant results of two previous projects, i.e. life cycle assessment of Danish electricity and power/heating, where residue products from electricity and heat production are listed, and LCAGAPS, where a calculation model for product specific emissions from waste incineration was developed. As the results from these projects have been available it has been possible to limit the data mapping to a system, which includes treatment, transport and deposit of the residue products.

Data has been calculated as average scenarios for Danish deposit plants, i.e. location of the plant (near coasts), recipient, depth of deposit, precipitation (and infiltration) are average calculations. This means that an average ratio between the liquid that infiltrates the deposit plant and the amount of substance that is infiltrated (L/S relation) and data from intensified washout tests can be used.

The collected data are the basis of a worksheet, where it is possible to calculate emissions and consumption based on the chemical composition of a material, as well as remaining amount of persistent substances in deposit after 100 years, by incineration of the material and treatment and deposit of the residue products.

For the electricity and heating production a work sheet has also been elaborated, where, based on a specific technology composition, it can be calculated which emissions and consumption are related to treatment and deposit of the residues.

Part II (Sub-project 2)

Part II of this report covers sub-project 2, which describes how, after the first 100 years, deposit plants may cause environmental impacts. When it is a question of the long time perspective it should generally be expected that all materials added to deposit plants, given sufficient moisture and time, will be converted and decomposed so that their content of environmentally dangerous persistent substances can be released. For all materials it is possible to point at mechanisms that in principle can make this possible.

The report arguments that toxic and persistent substances deposited today will, sometime in future, be released to the environment and, thus, potentially impact the environment and health of future generations. The discharge may take place over several years with percolate from the deposit plants, but may also take place more suddenly as a result of earthquakes, Ice Ages or another form of erosion of the deposit plant. To this is added the dispersion resulting from the fact that waste slag and other residue products being reused in e.g. noise walls and other plants may be removed or spread in the environment to a larger or smaller extent. The accumulated content of metals and persistent substances in the deposit plants will be released and spread in the environment. The time horizons for a complete dispersion of environmentally dangerous chemical substances from deposit plants must be estimated to be thousand to many million years, depending of course on the substances involved and the design and location of the deposit plants.

Our knowledge today about the future destiny of persistent environmentally toxic substances in deposit plants is that there are many mechanisms that can or will cause a dispersion of deposited environmentally toxic substances. It should therefore be considered likely that an important part of the environmentally toxic substances which today are added to deposit plants will some time in the future be spread in the environment.

The effect of this dispersion will, however, in many cases be difficult to predict, as it depends on the dilution in each case and, thus, on local conditions and the dispersion mechanisms of relevance in each case. It should therefore be noted that for each deposit plant, the content of environmental persistent substances represents a toxicity potential that will not necessarily come to its full effect. It is, thus, not evident that all deposit plants, with their content of substances and materials, will be spread entirely in the environment. Furthermore, that even though the environmentally toxic persistent substances are washed out or in some other way spread in the environment, dilution is so important that dispersion does not involve toxic effects.

To this should be added the subjective assessment of whether an impact, taking place sometime in the future, should be given the same weight as an impact taking place today.

It has thus been chosen to let the potential toxicity from the deposit plants be represented by the two new environmental impact categories "deposited human toxicity" and "deposited eco-toxicity" (with sub-categories in water and soil and for human toxicity also air). The two categories are in principle calculated like the other environmental impact categories relating to toxicity. The actual impact on the environment will vary with the location of the deposit plant and the event that causes the release. In the calculation of the deposited toxicity it is suggested the entire content of toxic substances of the deposit plant is released at the same time and that the emission is divided, 50% to water and 50% to soil. As opposed to the product-specific modelling of the emissions in the first 100 years, it should in the long perspective be assessed that all persistent substances in the deposed materials can be released. The deposed toxicity can, thus, be calculated on the basis of the product/material's content of such substances. This means that the deposed toxicity of all products/materials can be calculated, incl. the fractions of waste that are left out in sub-project 1, if the content of persistent toxic substances is known.

The quantification of two environmental impact categories causes that the decision maker partly has a quantitative target for the size of the problem and partly has the possibility to choose which importance this environmental impact should have compared to the traditional environmental impact categories.

The new impact categories should be considered an extension of the existing impact categories for human and eco-toxicity in EDIP. Even though two new categories have been introduced it is not the intention that they should have more importance compared to the other categories in EDIP, such as greenhouse effect, etc. On the contrary, the calculation of toxicity has a broader approach, because it is now possible to consider whether, in connection with production, use or destruction of products, is a deposit of persistent environmentally toxic chemical substances which will have a potential for a hazardous impact sometime in the future. Since deposited human toxicity and eco-toxicity represent a possible hazardous impact sometime in the future, whereas ordinary human toxicity and eco-toxicity represent a toxic impact taking place today, it is recommended that, generally, greater importance should be given to ordinary toxicity than to deposited toxicity. A proposal for an interpretation procedure has also been given, which is in accordance with this recommendation.

In the report the new impact categories are used to a large extent. Normalisation references have been elaborated for Denmark, and key figures have been given that can be used in the calculation of the potential for the fractions placed in a waste deposit after having been treated in an incineration plant.

The normalisation references have been elaborated on the basis of mass flow analyses, supplemented by analysis of a number of specific waste fractions with a large toxicity potential. Through this calculation of the normalisation references, we may get an impression of how large the potential emissions are, and, further, it is possible to identify the most important sources for each normalisation reference.

The normalisation references show that for certain sub-categories, i.e. human toxicity in soil, the deposited toxicity is considerably higher than the contribution from the "present" emissions (i.e. the emissions which are related to present activities in the society and which are part of the calculation of human toxicity and eco-toxicity in EDIP). For human toxicity via air, the contribution from the "present" activities is on the other hand 10,000 times larger, whereas for human toxicity via water it is a question of contribution of the same size from "present" emissions and deposits.

For deposited eco-toxicity it appears that a potential for eco-toxic effects is deposited via water with a factor 10 times bigger than the potential deriving from "present" activities. As opposed to this, the deposited eco-toxicity via soil is a factor 1000 lower, mainly due to the large contribution from pesticides to the ordinary normalisation reference.

The future work with the new impact categories may take several directions. It seems obvious to try to illustrate the importance of different substances and substance groups at a more detailed level than it has been possible in this project. An important element in this work is to develop effect factors for several persistent substances, e.g. brominated flame retardants, as this is a prerequisite for precise calculations. When the necessary information is available, the calculation is relatively simple, and at the same time, as a useful perspective is obtained on the long term significance of the use of environmentally dangerous persistent substances in industrial products compared to other environmental impacts related to the products.

Land use and resource use

Land use and resource use are briefly discussed in sub-project 1.

The occupation of land for deposit plants is another considerable environmental impact. The use of land is listed by time and deposit area (m²*year). It has not been solved in this project how the qualitative change of the site should be represented in the environmental impact category, even though this aspect is important for the development of normalisation references for land use.

The use of resources for waste deposit is related to establishment and operation of the deposit plant as well as consumption by e.g. treatment of residue products.

Conclusion

In the calculation of an example it turned out that the emissions and consumption included via the new calculations have an effect at the environmental impact assessment. Even though the amounts of persistent substances emitted during the first 100 years are small, they increase the potential for persistent toxicity. The largest differences are, however, that the new effect categories, deposited human toxicity and deposited eco-toxicity, dominate the environmental impact potential.

The project shows that the EDIP method in its present form leaves out a considerable contribution to the environmental impact potential, and it is recommended to introduce the results in the new LCA tool GaBi.

At the same time it should be concluded that a basis for a quantification of the environmental impacts from waste management has been provided, as an operational alternative to the practise so far where waste is calculated as an amount. The developed models for the first 100 years as well as normalisation references for deposited toxicity are, however, specific for Danish conditions, and it is not possible to entirely eliminate an amount of waste as an impact category. In the following it is recommended how the new methods could be implemented in the LCA work in Denmark.