1.2.1 Treatment options

Table 1.1:
Treatment options for paper and cardboard

1.2.2 Environment and resources

Environmental issues associated with waste treatment and recycling of paper and cardboard have been analysed in detail in a number of reports on environmental economics for paper and cardboard cycles /12/.

The basic question is whether paper should be recycled directly, avoiding some of the environmental impacts from production of new paper, but leading to other environmental impacts from collection and reprocessing of paper bulk, or whether it should be incinerated, ensuring recovery of the calorific value of paper.

In addition to wood, a number of chemicals are used in paper production for bleaching, boiling, and deinking (of recycled paper bulk), just as paper is mixed with glue and fillers such as lime and kaolin. Recycling paper requires less use of chemicals than production of virgin paper.

Table 1.2:
Significant environmental issues for incineration compared to recycling paper

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

Overall, energy-derived environmental impacts are in focus in the two most important treatment options for waste paper. Particularly, issues associated with substituted energy resources may be significant. Resource consumption for the production of paper primarily covers wood; a renewable resource, so this is of minor importance.

Eutrophication of the aquatic environment may be significant, if wastewater from paper production is not treated. Wastewater treatment in paper production is generally very good at Nordic paper manufacturers.

For emissions of toxic substances to the environment a significant reduction has taken place in recent years, as bleaching with chlorine has been substituted by processes with less impact on the environment. However, there is still a risk of emission of toxic substances, for example from deinking of paper for recycling.

Working environment impacts from separation of paper for recycling may be significant, but the data basis for such an assessment is insufficient.

1.2.3 Data basis

Table 1.3:
Data sources for waste paper

It appears from the above that it will be possible to obtain an annual, updated statement of consumption, incineration and rates of recycling for paper. For 1998 this rate reached 50%. In addition, it will be possible to some extent to obtain a continuous statement of application of paper.

1.3 Bottles and glass

Bottles and glass covers all products of glass, except from glass in electrical and electronic equipment. The reason for this distinction is that special problems occur in the treatment of technical glass.

1.3.1 Treatment options

For bottles and glass it is relevant to distinguish between the following treatment options:

Table 1.4:
Treatment options for bottles and glass

1.3.2 Environment and resources

The manufacture of glass from raw materials or remelting of cullet into new glass requires energy. Also direct reuse of bottles for example requires energy for transportation and washing.

Upon reuse of bottles, resources can be saved for manufacture of virgin glass. The most important raw materials for glass manufacture are soda, sand and lime, but in addition a number of auxiliary substances are used. Substitution of raw materials will be ensured through both reuse and recycling of glass.

Table 1.5:
Significant environmental issues for incineration compared to recycling of glass and bottles

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

Upon landfilling or recycling in the form of slag from waste incineration, glass must be considered to substitute raw materials such as gravel and sand, having less resource value than glass for remelting. Recycling of slag from waste incineration for construction purposes requires that glass is incinerated together with other wastes that do not give rise to environmental contaminants in slag, such as heavy metals.

Energy-derived environmental impacts are in focus in the differences between reuse and recycling of cullet and in landfilling, or through slag from incineration plants. However, differences are not very significant in the choice between reuse and remelting.

Resource consumption for manufacture of virgin glass primarily covers resources that are found in Denmark in large quantities. For glass contained in slag used for construction purposes, the resource sand will be recovered, as slag substitutes other use of sand. Landfilling, however, will lead to loss of resources.

For reuse of bottles, the bottles must be washed, and this may cause eutrophication from wastewater discharges. In Denmark, however, this problem is mitigated through wastewater treatment.

To a minor extent, toxic substances may be used in connection with washing bottles. In the manufacture of virgin glass the use of mould oil and other auxiliary substances may cause a (minor) impact from toxic substances.

Glass for landfilling – either directly or in the form of slag from waste incineration – will increase the total volume of waste and thus landfill requirements. Landfilled glass without heavy metal contents is not assumed to have long-term toxic impacts, but when mixed with other waste fractions it will contribute to total volumes.

1.3.3 Data basis

Table 1.6:
Data sources for bottles and glass

1.4 Plastics

Plastics constitute a very complex group, since many types of plastic, in addition to the raw polymer contain a large number of additives: stabilisers, flame retardants, softeners, pigments etc. Thus, there are a number of important factors that will be different from one type of plastic to another, and this makes it difficult to discuss plastics jointly. PVC differs from the other types, as it causes special problems.

1.4.1 Treatment options

For plastics it is relevant to distinguish between the following treatment options:

Table 1.7:
Treatment options for plastics

1.4.2 Resource and environment associated with plastics (except from PVC)

Environmental profiles for different plastic types, for example PET /7/, have been drawn up by the Association of Plastics Manufacturers in Europe - APME. In the manufacture of plastics, in addition to energy-related environmental impacts, there may be a significant contribution to photochemical ozone formation (VOC emission) and waste problems associated with, for example, sulphur and heavy metals that are removed from crude oil in the manufacture of plastics raw materials. In both reuse and recycling of plastics environmental and resource savings are possible.

In indirect recycling of plastics, expedient exploitation of additives contained in waste plastic types often does not happen. For heavy metals and resource consumption for the production of additives it will therefore be relevant to set indirect recycling equal to landfilling.

Special problems are associated with recycling plastic types containing heavy metals or other undesired substances, as upon recycling substances are kept in circulation and potentially spread to the surroundings.

Upon incineration, recovery of the energy contained in plastics is ensured to some extent, but for some plastic types energy consumption for the manufacture of plastics may be significantly larger than the energy recovered. Apart from PVC, only a modest number of plastics contain halogens in the polymer structure, but halogenated additives are widespread, particularly in the form of chlorinated and brominated flame retardants. Upon incineration of plastics, emissions of problematic substances may thus occur, particularly dioxin, just as in connection with flue-gas cleaning, considerable amounts of flue-gas cleaning products will be generated that are added to neutralise the acids formed.

Both upon incineration and landfilling of plastics with heavy metal containing pigments (lead, cadmium, copper, zinc) there may be long-term toxic effects.

Upon recycling there is a considerable loss of plastics: one quarter of plastic packaging collected is treated as waste in connection with recycling /28/. This indicates that in a calculation it will be also necessary to include the destiny of materials led to recycling.

1.4.3 Environment and resources for PVC

Chlorine contents in PVC cause a number of specific environmental impacts both in connection with the manufacture of chlorine and in waste treatment. Upon incineration, dioxins and hydrochloric acid are formed, and upon flue-gas cleaning larger amounts of residues are generated than the amount of PVC incinerated.

In addition, hard PVC often contains stabilisers such as lead, cadmium and other heavy metals that cause problems in waste treatment.

Due to these issues PVC will be stated apart at first, as it is expected that environmental benefits from direct recycling are more pronounced for PVC than for other plastic types. This assumption, however, must be verified.

Table 1.8:
Significant environmental issues for incineration compared to recycling of plastics.

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

In an overall assessment of environment and resource-related differences between recycling and incineration of plastics, several aspects are of importance. Resource and energy consumption for manufacture of plastics is important, as upon recycling into new plastic products energy resources may be saved, as plastics are manufactured from oil. Upon incineration of plastics, energy recovery will lead to substitution of other energy. Overall, from an energy and resource point of view there are probably no significant differences between recycling and incineration of plastics.

Emissions and waste associated with treatment of plastics, however, may be significant – particularly concerning PVC. As regards emissions, especially the content of acidifying substances (HCL) causes problems – which may be "converted" into a waste problem concerning landfilling of flue-gas cleaning products. Most plastic types may contain heavy metal residues from dyes and additives. PVC furthermore may cause formation of dioxins, so toxic effects from plastics incineration is a very significant issue.

In addition to landfilling of flue-gas cleaning products, plastics that are not clean or cannot be sorted are also landfilled upon recycling. The rate may be significant.

Finally it should also be mentioned that upon separation of plastics for recycling, there may be problems associated with the working environment, an issue that has not been studied sufficiently.

1.4.4 Data basis

Table 1.9:
Data sources for plastics

*) In the Plastic packaging statistics figures are stated for plastic packaging collection, broken down by the plastic types: LDPE, HDPE, EPS, PP, PET, PS and "Other plastics" /28/. The rate of collection, and thus amounts of plastic packaging that are not collected for recycling are calculated in the statements by comparing collected quantities with supply of plastic packaging.

At European level, plastic packaging accounts for around 57% of total amounts of plastic waste incl. PVC /28/. For other waste plastic types no continuous statistics are made, but this plastic is almost exclusively incinerated or landfilled today.

No regular statement of incineration and landfilling of PVC is made, but collection rates for PVC in building and construction waste have been estimated in several PVC studies. However, the most recent statement covers 1996 /3/.

1.5 Food waste and other organic waste

1.5.1 Treatment options

For food waste and other organic waste that is source separated, it is relevant to distinguish between the following treatment options:

Table 1.10:
Treatment options for food waste etc.

1.5.2 Environment and resources

Organic waste collected from professional sources primarily consists of food waste that can be used directly as animal fodder. This consumes energy for reprocessing, but far less than what is used for manufacture of fodder from virgin raw materials.

Household waste to a large extent consists of organic material. However, today only a limited amount of household waste is source-separated, but this area has been given high priority in Waste 21. The largest part is used for composting, but as a trial a minor part is used in anaerobic gasification plants. Finally, a large part of organic household waste may be home composted. This treatment does not recover energy contents in waste, but it saves energy for waste transportation.

From an energy and resource point of view, gasification ensures the best recovery, as energy is recovered and nutrients in materials are recovered as a fertiliser without any significant contents of heavy metals and similar. Methane gas released from the gasification process and from incomplete burning of gas may contribute significantly to global warming.

Table 1.11:
Significant environmental issues for incineration compared to recycling of food waste

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

Incineration of food waste gives a poor energy yield due to the high contents of water that may lead to poor incineration. Furthermore, contents of chlorine, for example in table salt, may cause formation of environmentally harmful substances in the incineration process.

Overall, there seems to be energy and resource-related advantages from recycling food waste into animal fodder, as the manufacture of new fodder requires energy, and incineration of food waste contained in household waste does not give large energy yields. The possibility of treating food waste together with other organic waste in anaerobic gasification may also provide a good exploitation, as both energy and nutrient resources are recovered. In return, gasification may contribute significantly to global warming.

In the incineration of food waste the contents of table salt may increase the risk of very toxic dioxin formation.

Finally, there may be important working environment issues associated with the management of food waste that have not been studied.

1.5.3 Data basis

Table 1.12:
Data sources for food waste etc.

The ISAG system contains data on amounts collected for animal fodder from enterprises and institutions as well as source-separated domestic waste. Potentials of organic waste in household waste are considerable, but no continuously updated statements are available. The most recent statement dates from 1994 /5/, where food waste is stated to constitute 36% of domestic waste. Waste Centre Denmark regularly prepares compost statistics that estimate amounts of home-composted household waste /4/.

1.6 Branches, leaves, grass etc. (and compost)

1.6.1 Treatment options

For treatment of collected branches, leaves, grass etc. a distinction is made between the following treatment options:

Table 1.13:
Treatment options for branches and leaves etc..

1.6.2 Environment and resources

For the environment and resources there are significant differences among recovery for chips or compost, and incineration with or without energy recovery. In an energy statement, the need for transportation associated with the different treatment options should also be included.

Upon incineration in the open land energy and resources are lost. As open burning does not give optimum incineration, pollution with, for example, PAH may be significant.

Upon storage and composting, materials to some extent will decompose, forming methane gases that contribute to global warming.

Table 1.14:
Significant environmental issues upon incineration compared to recycling of garden waste

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

The focal point of the assessment will be energy, as the resource in question is renewable. But in a life-cycle perspective energy considerations may be rather involved. For example, recovery upon incineration may reduce consumption of other non-renewable resources, whereas utilisation as compost or chips may reduce consumption of fertilizer the production of which also requires energy.

All organic material may contribute to global warming if it is stored in a way that allows a gasification process to start – or for example in home composting.

1.6.3 Data basis

Table 1.15:
Data sources for garden waste

The ISAG system contains data on collected amounts of materials as well as statistics of used (removed) amounts of compost and chips. In 1997 more than 90% of composted waste was used in the same year, the remainder being stored. Over half was used in private gardens.

Bark and wood chips is not registered in the ISAG if it is treated and used directly on the site of generation, for example in parks and churchyards etc.

1.7 Iron and metals

1.7.1 Treatment options

For iron and (other) metals it is relevant to distinguish between the following treatment options:

Table 1.16:
Treatment options for iron and metals

1.7.2 Environment and resources

Upon recycling, in addition to resource and energy savings, a reduction in environmental impacts associated with extraction of metals is achieved. Significant environmental impacts include spreading heavy metals upon raw material extraction, acidification, greenhouse effect, occupation and long-term deterioration of land. In extraction, large waste quantities are often generated. For example, around 300 tonnes of waste are generated for each tonne of copper. For metals it is thus very important to include these early phases of the life-cycle.

All iron and metals collected are led to recycling. However, there will be a certain loss in connection with recycling. Metals are often used in alloys, and in recycling a loss of utility value may occur, as the qualities added by alloy elements to the alloy are not exploited in the secondary material. In addition, alloy elements may instead become polluting elements in the secondary material, for example, in the remelting of steel or aluminium. These utility value losses must be considered as resource losses of alloy elements.

Table 1.17:
Significant environmental issues for incineration compared to recycling waste metal

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

For metals incinerated or landfilled it may be significant to distinguish between heavy metals (lead, mercury, cadmium etc.) and other metals (iron, aluminium, magnesium).

In general, environmental impacts associated with resource and energy will be in focus for all metals, but in connection with raw material extraction and processing of raw materials there will be a large number of environmental impacts that are specific for the different metals. For example, carcinogens (PAH) and acidifying substances are released in connection with melting aluminium.

For heavy metals, in addition to a significant resource dimension, there is also an important problem associated with long-term toxic effects of heavy metals led to landfilling or included in slag used for construction purposes. Some of the heavy metals may also end up in filter dust, for example in connection with incineration of metal parts. This filter dust must be landfilled.

Seen from a life-cycle perspective, landfilling metals instead of recycling them will create a landfill requirement not only in connection with waste treatment but also to a high extent in connection with extraction of virgin materials, since mining often generates large waste quantities.

Regarding working environment, no overall statements have been made of advantages and disadvantages from the manufacture of virgin metals compared to recycling. However, some data is available on the manufacture of virgin metals, where mining, for example, may cause many accidents /19/.

1.7.3 Data basis

Table 1.18:
Data sources for metals

Current waste statistics state total amounts of iron and metal scrap collected for recycling under iron and metal scrap. There is no information on individual metals, and the rate of collection has not been calculated. Waste Statistics 1997 state that the rate of recycling for iron and metal scrap exceeds 90%. The high rate of collection is due to the fact the rate of collection for iron and steel is very high, and iron and steel make up by far the major proportion of total amounts of metal. The rate of collection for most other metals, according to mass-flow analyses, is in general below 90%.

A precondition for detailed calculations of resource and environmental consequences of waste treatment of iron and metals is that specific information is available on management of the different metals, or at least the most important metals. Preliminary calculations can be based on mass-flow analyses that have been prepared for most metals.

Overall, due to the available statistical basis it is difficult to make a detailed statement for iron and metals.

1.8 Automobile rubber

1.8.1 Treatment options

For treatment of automobile rubber (tyres) a distinction is made between the following treatment options:

Tabel 1.19:
Treatment options for automobile rubber

1.8.2 Environment and resources

Automobile rubber is manufactured primarily from artificial rubber with relatively high energy consumption for manufacture of the rubber material. Waste tyres are primarily reprocessed at one enterprise in Denmark. Tyres of good quality may be retreaded, and the rest granulated. Upon granulation metal parts of stainless steel, containing nickel for example, are separated.

Upon incineration of granulated artificial rubber only around 20-25% of energy from original production is recovered.

Upon retreading energy is saved compared to the production of new tyres.

Recycling of rubber as a paving material often substitutes other materials whose production requires far less energy. However, it also has some special properties that are requested for different purposes.

Table 1.20:
Significant environmental issues for incineration compared to recycling of tyres

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

The focal point of an assessment of environmental differences between reuse, recycling and incineration of tyres is energy and resource issues, as the production of new tyres requires energy and raw materials in the form of oil and nickel for stainless steel.

Upon incineration of tyres without prior granulation or upon landfilling, resources contained in stainless steel are lost.

1.8.3 Data basis

Table 1.21:
Data sources for tyres etc.

The ISAG system contains information on automobile rubber. It can be supplemented with the Danish Tyre Trade Environmental Foundation’s statistics on the take-back scheme and statistics on retreading and granulation for rubber powder /40/. Large tyres (trucks and tractors etc.) have only been covered by the rules since 1999, and therefore they only appear in statistics since that year.

1.9 Concrete and tiles

1.9.1 Treatment options

For concrete and tiles the following treatment options are available:

Table 1.22:
Treatment options for concrete and tiles

1.9.2 Environment and resources

Tiles and bricks can be reused to some extent after cleaning and separation, if demolition is conducted carefully. The process is labour-intensive, but from an energy and resource point of view it is a good solution, as energy for production of new bricks is saved.

Indirect recycling through crushing recycles resources as a substitution for gravel etc. Upon use as aggregate for new concrete, the hardening properties of concrete are not exploited, and this use thus substitutes resources such as gravel and pebbles.

Resources used for reinforcement in concrete may be recycled upon crushing, but reinforced concrete parts are probably often used as harbour filling material etc., thus losing the resources contained in reinforcement iron.

Table 1.23:
Significant environmental issues for incineration compared to recycling of concrete and tiles.

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

Energy consumption for crushing and transportation must be seen in comparison to excavation and transportation of new backfilling material, and it is estimated to be of a similar order. Upon reuse of tiles, which only takes place to a very limited extent, a slightly larger energy benefit is achieved.

Good source separation of construction and demolition waste is important to avoid contamination with toxic substances, for example in pressure-impregnated wood, PVC and electrical equipment. Such separation is already practised extensively, and focus on environmentally correct design will contribute to ensuring that this will also be possible in the future.

From a landscape point of view, recycling through crushing is of advantage, partly as it saves excavation of virgin materials, and partly as it reduces landfill requirements.

1.9.3 Data basis

Table 1.24:
Data sources for concrete and tiles

Amounts of recycled materials appear from the ISAG system. Waste Centre Denmark prepares special statistics on construction and demolition waste /32/. These statistics indicate annual amounts generated, giving the basis for calculating the rate of recycling for construction and demolition waste. In 1997 more than 91% was used for backfilling.

1.10 Asphalt

1.10.1 Treatment options

For asphalt the following treatment options exist:

Table 1.25:
Treatment options for asphalt

1.10.2 Environment and resources

Asphalt is recovered to a large extent; either after demolition of paving, or directly in connection with "milling off" paving, where crushing, heating and mixing with additional bitumen takes place. This is done either in stationary treatment plants or in mobile plants. Even if energy is required for heating and transportation, environmental and resource-related advantages compared to manufacture of new asphalt are evident, and the method is used extensively. Only asphalt mixed with other materials – such as concrete – is landfilled or crushed for backfilling.

Table 1.26:
Significant environmental issues for landfilling compared to recycling of asphalt

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

Upon recycling waste, energy and resources are saved, but primarily landfill requirements are saved for waste asphalt. The typical treatment options for waste asphalt do not seem to imply significant differences in pollution with toxic substances.

1.10.3 Data basis

Table 1.27:
Data sources for asphalt

Quantities treated at stationary plants are registered in the ISAG system. Upon direct reuse of asphalt for new paving on site, quantities treated must not be reported as waste to the ISAG. Waste Centre Denmark has prepared a very detailed analysis of management of waste asphalt. From this it appears that almost all waste asphalt is recycled /32/.

1.11 Other construction and demolition waste

This group consists of mixed construction and demolition waste such as wood, insulation material, glass, metals, cardboard, plastics and problem wastes (for example electrical installations), and clean soil.

1.11.1 Treatment options

For mixed construction and demolition waste the following treatment options may be relevant:

Table 1.28:
Treatment options for other construction and demolition waste

1.11.2 Environment and resources

To the extent that materials are not separated and recycled, a 100% resource loss will occur from landfilling.

In so-called selective demolition materials are separated during demolition. This allows for a very high rate of recycling (more than 90%). If the structure contains asbestos, working environment precautions must be taken upon demolition.

Building materials may furthermore contain environmentally harmful substances, for example in pressure-impregnated wood or electrical components. This concerns in particular various heavy metals. Apart from materials of wood or paper, other materials do not decompose in a short-term perspective, and waste will require space for landfilling.

Table 1.29:
Significant environmental differences between landfilling, incineration and recycling of construction and demolition waste

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

Upon separation of construction and demolition waste a reduction in landfill requirements is achieved, and this also allows for reductions in long-term toxic effects from landfilling the environmentally most harmful part of waste.

There are also energy and resource-related advantages from better separation of construction and demolition waste, even if they are not in focus in the different treatment options for this fraction.

1.11.3 Data basis

Table 1.30:
Data sources for other construction and demolition waste

The group is covered by the ISAG system, and Waste Centre Denmark has carried out detailed studies of construction and demolition waste. However, the composition of the mixed ISAG fraction "other construction and demolition waste" has not been studied. Waste 21 establishes the objective that a larger proportion of construction and demolition waste should be source-separated. In particular environmentally harmful material fractions such as impregnated wood and electrical equipment should be separated.

1.12 Wood

1.12.1 Treatment options

This fraction consists of wood collected from industry and commerce, and building and construction activities. Wood used for packaging is also covered. For wood the following treatment options are possible:

Table 1.31:
Treatment options for wood

1.12.2 Environment and resources

Wood is a renewable resource, and if it is incinerated it substitutes other energy sources. Upon reuse or direct recycling, energy for tree felling, transportation and processing is saved, and the resource can still substitute energy for heat etc. upon waste incineration.

Impregnated wood constitutes a particular environmental problem, and its use and waste quantities are increasing significantly. Wood impregnated with creosote and fungicides may be crushed and incinerated at high temperatures. However, if impregnation agents are heavy metals, controlled landfilling is required for environmental reasons. However, methods are being developed that may recover heavy metals by crushing and electrolytic treatment, after which residual materials may be incinerated.

Table 1.32:
Significant environmental differences between landfilling, incineration and recycling of waste wood

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

For wood, a distinction must be made between clean wood and impregnated wood. Clean wood in waste is mostly used as an energy resource. However, pigmentation in paints may constitute a problem with toxic substances.

From an environmental point of view, for impregnated wood managing toxic substances used for impregnation is crucial. If substances can be rendered harmless through incineration it saves energy resources. If landfilling is necessary there is a long-term risk of release of, for example, heavy metals, to the surroundings.

1.12.3 Data basis

Table 1.33:
Data sources for wood

Wood collected for reprocessing is included as an ISAG fraction.

Waste Centre Denmark has published statistics on production, consumption and treatment of impregnated wood /3/. Calculations of amounts of wood for treatment are difficult, as many years may pass from use to waste treatment.

1.13 Soil and stone

1.13.1 Treatment options

For soil and stone the following treatment options are possible:

Table 1.34:
Treatment options for soil and stone

1.13.2 Environment and resources

Direct recycling upon remediation for oil contamination, for example, takes place in either stationary or mobile plants or by treatment without excavation. In the use of mobile plants and treatment without excavation, energy consumption for transportation is reduced.

Treatment options range from bacteriological treatment, washing, heating or incineration, and energy and environmental issues associated with these treatment options differ widely. The choice of treatment option also depends on the type of contamination.

Without going into detail on treatment options, it may be concluded that excavation and transportation to treatment plants is expensive and energy-intensive. In return, the most significant contamination is removed and this would otherwise be washed out into groundwater. Excavating and landfilling contaminated soil requires secure facilities of a considerable size, and consequently soil remediation is definitely the preferred option.

In on-site treatment, with or without excavation, much transportation energy can be saved compared to treatment at stationary plants. On-site treatment options are not always sufficiently efficient or fast, and consequently transportation to a treatment plant is often preferred.

Table 1.35:
Significant environmental issues for incineration compared to recycling soil and stone.

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

The most significant environmental problem associated with treatment of contaminated soil is the risk of release of toxic substances to the surroundings. Upon landfilling space is taken up, and if soil is contaminated with heavy metals, the problem is merely postponed.

Upon remediation of soil, transportation to a treatment plant will require energy, and furthermore some treatment options are energy-intensive.

1.13.3 Data basis

Table 1.36:
Data sources for soil and stone

Both clean soil used for covering and exempt from taxation and taxable soil for remediation or landfilling are included in the ISAG system. By contrast, clean soil for disposal in gravel pits is not included.

1.14 Other recyclables

1.14.1 Treatment options

This group covers waste for subsequent separation and treatment, for example scrapped vehicles or dry household waste.

Table 1.37:
Treatment options for "other recyclables"

1.14.2 Environment and resources

Manual separation of recyclable dry, but mixed household waste entails so many working environment problems that it is not carried out in Denmark. Instead, mechanical crushing and drying of waste may be carried out, and waste can subsequently be pressed into a so-called "dry-stabilate" to be transported, stored and used for subsequent incineration.

The other large item in this fraction is vehicle scrap in temporary storage. This fraction is currently treated after shredding and further reprocessing of metal parts. The large problem associated with this option is shredder waste consisting mostly of mixed plastics that is today landfilled, as incineration gives severe risk of contamination with a number of organic and heavy-metal-containing compounds.

Table 1.38:
Significant environmental issues for landfilling compared to recycling of other recyclables.

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

The fraction consists of dry household waste, which is temporarily landfilled, as well as vehicle scrap, particularly shredder waste, for subsequent treatment. Energy and resource problems associated with subsequent treatment of waste products will be in focus here.

Since landfilling is temporary, this is not the most decisive environmental issue. After separation there may be a residual fraction that is re-registered in the ISAG into waste suitable for incineration.

Vehicle scrap may contain environmental contaminants such as waste oil, cooling and brake fluids. Upon reprocessing of vehicle scrap by shredding there will be a resource benefit. However, there will be a residual fraction, particularly of mixed waste plastics, that may cause a toxic impact on the environment upon incineration or landfilling. As no acceptable treatment options are available today, shredder waste is temporarily landfilled.

1.14.3 Data basis

Table 1.39:
Data sources for materials for recycling landfilled temporarily.

The ISAG system contains data on temporarily stored amounts that are recyclable. Since summer 2000 there has been a special premium and subsidy scheme for end-of-life vehicles as well as an approval scheme for plants receiving vehicle scrap.

1.15 Health-care risk waste

1.15.1 Treatment options

This group consists of waste with a risk of infection. The only relevant treatment option therefore is incineration, with or without energy recovery.

Table 1.40:
Treatment options for health-care risk waste

1.15.2 Environment and resources

Incineration, particularly of PVC-containing materials will cause environmental problems. For all resources in this fraction a 100% loss takes place, but to some extent energy is recovered upon incineration.

Minimisation of waste quantities and choice of less environmentally harmful materials instead of PVC seem to be the only alternatives at present. Waste quantities in question are relatively small.

Table 1.41:
Significant environmental issues upon incineration of health-care risk waste

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

Energy recovery from waste incineration is the most important issue in waste management. Upon incineration of PVC toxic substances may be formed, which however can be limited through optimisation of the incineration process.

1.15.3 Data basis

Table 1.42:
Data sources for health-care risk waste

The ISAG system registers quantities of health-care risk waste from hospitals, nurseries and clinics etc.

1.16 Mixed waste for incineration

1.16.1 Treatment options

This is one of the largest fractions registered in the ISAG system. It covers a large proportion of domestic waste and most other waste led to incineration.

Table 1.43:
Treatment options for mixed waste for incineration

1.16.2 Environment and resources

Manual separation of recyclable dry, but mixed household waste entails so many working environment problems that it is not carried out in Denmark. But it is possible to increase source separation and collect more paper for reprocessing /30/.

If waste is collected in a mixed state, mechanical crushing and drying of waste may take place instead, and waste can subsequently be pressed into a so-called "dry-stabilate" to be transported, stored and used for subsequent incineration.

Even if trials have been made with gasification and composting of mixed domestic waste, residues from this treatment still constitute an environmental problem. Such treatment options are mostly practised for the source-separated, organic part of waste where the residual product is much more suitable for use as compost. If waste is stored without treatment (or is landfilled) the material will start gasifying, leading to methane gas being emitted to the surroundings.

Table 1.44:
Significant environmental issues upon incineration compared to recycling of burnable household waste

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

In the assessment of resource and environmental advantages from incineration, both landfilling and incineration of waste must be compared with fuel consumption and environmental impacts from energy generation without waste incineration.

Table 1.45:
Data sources for mixed waste for incineration

The ISAG system registers waste quantities received at waste incineration plants. A more detailed statement of composition of waste may be found in "Domestic waste from private households" /5/. This publication presents results of a separation trial of a number of domestic waste bags in 1992/93.

The Association of Danish District Heating Plants publishes an annual statement analysing energy resources by waste incineration and other sources at the different plants /2/. In the assessment of substitution of energy with waste incineration such information is essential. However, statistics do not contain information on waste heat from waste incineration that is not recovered.

1.17 Mixed waste not suitable for incineration

1.17.1 Treatment options

This group consists of waste separated from industrial waste and bulky waste that is not suitable for incineration. It may be burnable waste that is not incinerated for environmental reasons, such as shredder waste, or it may be unburnable waste.

Table 1.46:
Treatment options for waste not suitable for incineration

1.17.2 Environment and resources

This is mixed waste for which no suitable treatment option exists today. This material cannot be used for backfilling, and therefore an essential environmental parameter is space for landfilling. The material is relatively stable, as it contains no organic materials in significant quantities, but its composition has not been studied sufficiently for assessing how fast the different components are decomposed. The material contains a number of environmentally harmful substances, such as heavy metals in additives for plastics.

Perspectives for future treatment may include better separation and incineration methods for some parts of this waste.

Table 1.47:
Significant environmental issues for landfilling compared to recycling of mixed waste not suitable for incineration.

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

Separation of this waste may save resources, and the need for landfilling may be reduced. This may reduce the risk of release of toxic compounds. Working environment issues associated with better separation have not been studied sufficiently.

1.17.3 Data basis

Table 1.48:
Data sources for waste not suitable for incineration

Waste is registered as a fraction in the ISAG system, and no further analyses of waste composition are known of.

1.18 Sludge

1.18.1 Treatment options

Sludge from wastewater treatment plants and industry may in principle be treated in the following ways:

Table 1.49:
Treatment options for sludge

1.18.2 Environment and resources

The largest problem associated with sludge is its contents of environmental contaminants such as heavy metals and eco-toxic organic compounds such as decomposition residues from tensides etc. Substances derive from sewage from industry and households. Requirements for contents of substances in sludge before spreading on farmland are becoming increasingly strict, whereas it seems difficult to reduce contents of environmental contaminants in wastewater. This means that an increasing amount of sludge is landfilled instead of being used as a soil improver and nutritious material.

Sludge may be treated by composting or gasification before spreading on farmland, but it still requires a low content of environmental contaminants, unless sludge is landfilled after gasification.

Upon gasification, energy contained in sludge is recovered, which counts on the positive side in a life-cycle perspective, as the fertilising value of sludge can still be exploited. However, there will also be a certain emission of methane gas – either from storage of sludge or in connection with the gasification process. Methane gas contributes to global warming.

Upon incineration of sludge, the fertilising value is lost. By contrast, some of the environmental problems of landfilling may be minimised or removed. The incineration process normally gives only a small energy surplus, as evaporation of water contained in sludge requires much energy. Furthermore, it is difficult to achieve incineration that does not cause serious environmental problems relating, for example, to PAH, just as the contents of heavy metals in sludge are merely removed to the flue gas from the incineration process.

Table 1.50:
Significant environmental issues for incineration or landfilling compared to recycling sewage sludge.

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

The critical issue for sewage sludge is whether it contains toxic compounds that makes it unsuitable for spreading on farmland.

Incineration is another treatment option, entailing instead a risk of problems of CO₂ and PAH emissions without any significant energy benefit, as most energy will be used for drying sludge. If sludge is stored, gasified or composted, it will release methane gases contributing to global warming.

1.18.3 Data basis

Table 1.51:
Data sources for sludge

Sludge is registered in the ISAG system and in individual registration of sludge from wastewater treatment plants. Sludge quantities and contents of environmental contaminants have been surveyed in detail in recent years.

1.19 Sand and screenings

1.19.1 Treatment options

Treatment residues from wastewater treatment plants – various waste from pre-filtering and precipitated sand.

Table 1.52:
Treatment options for sand and screenings

1.19.2 Environment and resources

As long as it is possible to separate into further fractions, such as metal, burnable materials and sand, it will be possible to recycle some resources and save landfilling space. No detailed survey of the composition of this fraction is known of.

Table 1.53:
Significant environmental issues for landfilling compared to recycling of sand and screenings

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

This waste is landfilled today, and the environmental focus is on landfill requirements.

1.19.3 Data basis

Table 1.54:
Data sources for sand and screenings

Data appears from the ISAG system, but constitutes only a small quantity.

1.20 Slag, fly-ash and flue-gas cleaning products

1.20.1 Treatment options

The following covers all residues from waste incineration plants and coal-fired power plants.

Table 1.55:
Treatment options for slag and fly-ash etc.

1.20.2 Environment and resources

Slag from waste incineration plants is used extensively for backfilling /40/, but due to contents of heavy metals it must be ensured that no leaching to groundwater takes place. In contrast, flue-gas cleaning products are not sufficiently stable to be recycled and are temporarily landfilled either in Denmark, Norway or Germany. Trials are taking place to stabilise residues, and when a method has been found residues can be landfilled permanently. This will save energy resources for transportation and management of materials.

Table 1.56:
Application of residues from coal-fired power plants (The Danish Environmental Protection Agency, 1997)

* DDP: Dry desulphurisation product
Source: Waste 21. Note that the table does not cover residues from waste incineration plants

Residues from coal-fired power plants account for very large quantities that are, however, decreasing. The recycling rate for the different residues is very high. Table 1.56 shows quantities recycled in 1997. Only 27% was landfilled, and the objective in Waste 21 is that landfilling should cease before 2004.

Table 1.57:
Significant environmental issues for landfilling compared to recycling of slag etc.

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

Upon recycling of residues, energy and resources for manufacture of similar materials from virgin materials (sand and gypsum) are saved, and landfill space for residues is saved.

For slag and residues from incineration, contents of heavy metals are often too high for them to be recycled in the same way as residues from power plants. If possible, slag is used for backfilling in roads etc., but it is often landfilled after separation of metals for recycling.

1.20.3 Data basis

Table 1.58:
Data sources for slag and fly-ash etc.

Data appears from the ISAG system divided into slag, fly-ash and flue-gas cleaning products from waste incineration and residues from coal-fired power plants. As early as in 1997 around 75% of residues from power plants and waste incineration were recycled /37/. Flue-gas cleaning products from incineration are landfilled as hazardous waste.

1.21 Dust-emitting asbestos

1.21.1 Treatment options

Table 1.59:
Treatment options for dust-emitting asbestos

1.21.2 Environment and resources

Asbestos is non-decomposable waste. Asbestos is divided into three categories, of which dust-emitting asbestos (Category 1), due to the dangers to health from dust, is encapsulated (normally with plastic film) to allow for management and transportation to final disposal. Upon landfilling this material is very stable, and there is very little risk of leaching of environmentally harmful substances.

Table 1.60:
Significant environmental issues upon landfilling of dust-emitting asbestos.

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

After landfilling asbestos will not cause significant environmental impacts.

1.21.3 Data basis

Table 61:
Data sources for dust-emitting asbestos

Appears from the ISAG system, but constitutes very small quantities.

1.22 Oil and chemical waste

1.22.1 Treatment options

This fraction consists of a number of waste products. Oil and chemical waste is discussed in this report as an individual fraction, corresponding to the former systematics of the ISAG system. Since the Statutory Order on Waste from 1998, waste has been registered in far more detail than hitherto. Today around 50% is treated at the hazardous waste treatment plant of Kommunekemi.

Table 1.62:
Treatment options for oil and chemical waste

1.22.2 Environment and resources

Consists of a large number of environmental contaminants of which only a few are reprocessed for recycling – particularly batteries containing lead, nickel and cadmium where resources can be recycled. Thus, landfilling of heavy metals is avoided, and the loss of resources is reduced.

To a certain extent waste oil is cleaned for recycling. However this can only be done for some fractions of waste oil. Some waste oil is cleaned for water and can subsequently be utilised at district heating plants.

Upon incineration of waste oil and other chemicals at Kommunekemi with subsequent flue-gas cleaning and special landfilling of slag, waste heat is used for heat and power generation.

Table 1.63:
Significant environmental issues for incineration compared to recycling of oil and chemical waste

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

A very large proportion of oil and chemical waste causes toxic impacts on the environment. As the group is large, consisting of many substances and products, only a few specific environmental issues will be discussed here.

For lead and Ni/Cd accumulators a collection scheme has been established, ensuring recycling of resources and avoiding spreading of heavy metals in the environment.

Cleaning and combustion of waste oil gives an energy benefit. A number of surveys have been launched with a view to recycling different fractions of hazardous waste.

1.22.3 Data basis

Table 1.64:
Data sources for oil and chemical waste

Data appears from the ISAG system. Since 1998 hazardous waste has been classified and registered in far more detail than hitherto. In waste statistics 1999 /40/ hazardous waste is now registered in 60 to 70 categories, and the Statutory Order on Waste contains even more categories /35/.

1.23 Electrical equipment

1.23.1 Treatment options

This group consists of two types of product that are discussed under one group in this report: Electrical and electronic equipment (EEE) and refrigeration equipment. Both groups are covered by special waste management schemes.

Table 1.65:
Treatment options for WEEE (Waste electrical and electronic equipment)

1.23.2 Environment and resources

Electrical equipment contains a number of different plastic, glass and metal parts as well as electronic components. In addition, refrigeration equipment marketed in Denmark before 1994 may contain ozone-depleting CFCs.

Refrigeration equipment can be disassembled, and CFCs from the cooling system and insulation material can be collected. Metal parts can then be sent for recycling or shredding together with other metal scrap. In this process, metal parts are separated from plastic parts.

For electronic components, new requirements for take-back and reprocessing aim at dismantling appliances. Cathode ray tubes and a number of electronic components must subsequently be treated at specialised plants, whereas metal parts can be reprocessed together with metal scrap. Plastic parts may contain brominated flame retardants or be made of PVC, both causing dioxin formation upon incineration.

Table 1.66:
Significant environmental issues for incineration or landfilling compared to recycling of WEEE.

*) All resource consumption and environmental impacts excl. contribution from energy consumption
xx: significant, x: less significant, nil: insignificant

For refrigeration equipment there is a large risk of release of ozone-depleting substances - CFCs.

For electronics in general there is a risk of release of heavy metals and persistent substances such as PCBs from electronic components.

In addition, products contain a number of relatively rare metals that are lost upon landfilling. Upon reprocessing of electronic components these metals may be recovered.

1.23.3 Data basis

Table 1.67:
Data sources for electrical equipment

Data appears from the ISAG system. From 1998 and 2000 current statements will be made of refrigeration equipment and WEEE covered by the take-back scheme.