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5. EXTERNAL COSTS OF WASTE MANAGEMENT

This chapter reviews existing literature concerning the external costs of waste management. Chapter 6 takes forward some of the lessons learned to generate what are still highly-flawed estimates of the external costs of waste management options.

5.1 Linear and Circular Flows of Materials

Unlike options such as landfill and combustion, which are final treatments, recycling (and reuse) result in material being returned to production processes, either in closed loop processes (where the material is made into the same, or similar product from which the material arose) or in processes where the waste material is fashioned into something completely different. This means that, for the economy as a whole, there is a reduced need for primary extraction, and hence there is a reduction in the environmental effects from the production, processing and transport of the raw material. To accurately assess the difference in impacts of the options recognition needs to be given to the reduction in the overall level of primary production, but also to the increase in environmental impacts associated with recycling itself.

Recovery of energy from waste can do the same thing indirectly by reducing the need for consumption of energy sources, but it can do this only once. Although recycling cannot occur indefinitely (for example, owing to shortening of fibres in newsprint recycling), the recycling can usually take place more than once. There is, therefore, an element of circularity in the recycling process that distinguishes it from landfill and incineration. For the sake of convenience only, landfill and incineration will be referred to henceforth as 'linear waste management options.'¹⁵

[¹⁵ Note however that some have proposed storing materials in landfills until suitable uses / technologies can be found to justify 'mining' them. Whilst this may seem fanciful, past consultations have shown that at least one power company has considered mining its own landfills for previously landfilled ash which it is now able to sell commercially.]

The change in environmental impacts as a result of recycling comprise not just those associated directly with the alternative materials processed themselves but also those associated with primary extraction, transport and production of the virgin material. Only the environmental impacts arising between the point at which the primary and secondary materials are combined, and the wastes are separated, are common to the linear and circular pathways, and need not be assessed for the purposes of a comparative analysis.

An analysis comparing two linear waste management options for instance incineration compared to landfill would only need to assess the post-consumption costs of the two options since the pathways up to that point are entirely common between the two options. Neither landfill nor incineration offers any means of reducing the need for primary extraction of the material concerned though both may lead to recovery of energy. Figure 2 below makes this point.

Figure 2: Contrast Between Linear and Circular Waste Management Options

If 30% of the material that is used is recycled then only 70% of the amount of raw material (or slightly more allowing for wastage in materials recycling) needs to be extracted and processed into material for use in final consumption. This reduces the rate at which primary resources are run down, and reduces the disruption of land surface and water pollution caused during the extractive process for the economy as a whole.

Of course recycling also has environmental effects. Energy is consumed in separating, transporting, cleaning and processing the recycled material to the point at which it is combined with the primary material stream. Greenhouse gases and particulates, as well as dioxins are emitted in the process. However, if the process of primary production is more energy intense than secondary production, recycling reduces the rate of energy consumption.

It is, as we shall see, a characteristic of waste management options that (apart from minimisation) no option performs better than another on all accounts. Because that is not the case, the decision as to which option is 'the best' requires some way of making decisions regarding waste management. One such way is to trade off the different pros and cons of the approaches through economic valuation of the different effects. This is, it should be added, only one of a number of approaches to 'valuation', some of which have been summarised in Powell et al (1995). It is important, at this point, to emphasise that waste minimisation is beyond the scope of this analysis. We are, therefore, ignoring some very interesting debates about materials consumption in modern lifestyles (we are implicitly assuming consumption continues as today).

5.2 Review of Existing Studies

A number of studies have sought to address the external costs and benefits of different waste management options through the combined process of LCA and economic valuation.

In what follows, we make much of the inadequate treatment, or appreciation of, uncertainty in the scientific domain where economic valuation is concerned. It is important in this respect to distinguish between uncertainty, risk, and error. Uncertainty is frequently used in contexts of description of exposure to hazards, and in the context of measurement. In the former case, it is worth juxtaposing the terms 'risk' and 'uncertainty'. A risk can be considered as a quantifiable probability of a particular consequence occurring. Throwing the number 'one' on an unweighted die can be ascribed a probability owing to the intrinsic characteristics of the die. The probability of a road accident occurring can be ascribed a probability on the basis of actuarial approaches using statistical data. When there is less in the way of past experience to guide us, or where a particular problem raises new questions which are not amenable either to some fundamental law, or to actuarial analysis, then uncertainty is likely to characterise our understanding of that problem. We are frequently not, in these cases, able to know exactly what the outcomes of particular processes or changes might be, still less to know the probability of certain specified outcomes. Uncertainty is the battlefield on which scientists do what scientists should do, that is to say, dispute in objective fashion the available evidence and interpretations thereof. It can be argued that we are slowly beginning to recognise that this is the normal state of affairs in science rather than an occasional exception to a world of much-cherished certainties.

Where measurements are being made, errors can arise owing to imperfections in measurement instrumentation, or to statistical variation where observations are distributed around a particular value. Sometimes, the term 'uncertainty' is used interchangeably with what appears to be error. On the other hand, in the context of valuation, there are certainly disputes as to the epistemological basis for certain approaches to measurement of the value of, say, a species under threat of extinction. For the purposes of this study, one could interpret this as methodological uncertainty. Again, as we shall see below, the debate around how to value life might be said to be dogged both by scientific uncertainty as well as those of an epistemological nature which translate into methodological uncertainties. Application of these methodologies, even if one was to accept their methodological credentials, are also likely to incur errors in measurement. Attempts to value, for example, the effects of dioxin on human health (see AEA 1997) face the rather daunting task of having to deal with both uncertainty and error where valuation is attempted.

As regards the conventions used in what follows, we are reporting externalities. Negative numbers represent negative externalities (disbenefits) whilst positive numbers are used to represent positive externalities (benefits).

5.2.1 CSERGE et al (1993)

This work is particularly well known as it was used in the run-up to the introduction of the Landfill Tax and was influential in the decisions ultimately made concerning the level at which the tax should be set. The aim was to understand the externalities associated with landfill and incineration. The study made clear that the potential benefits which might accrue if materials were recycled were outside the remit of the study rather than considered unimportant per se. Also, although the study undertook a review of work carried out elsewhere in assessing disamenity associated with landfills, these were omitted in the quantification of the external costs, though the study noted these could be 'significant' and therefore their omission would affect the results. Brisson and Pearce (1995) later suggested that employing benefits transfer techniques from US studies would make a figure of £160 (about £173 in 1999 terms) per household per annum not unreasonable for houses within a 4 mile radius of a landfill (which they also suggest is more or less equivalent to 3% depreciation on house values).¹⁶

[¹⁶ The lack of consideration of disamenity is more comprehensible when one sets the study in its policy context. In informing the level of a landfill tax being levied on waste, the fixed rather than variable nature of the disamenity externality could be used to justify not including the disamenity externality.]

The results of the study are as indicated in Table 15.

Table 15: Externality Values for Landfill and Incineration (£/tonne waste other than disamenity)

Notes:

^a L1 is an existing urban landfill without energy recovery;

^b L2 is a new urban landfill with energy recovery;

^c L3 is an existing rural landfill without energy recovery;

^d L4 is a new rural landfill with energy recovery;

^e I1 is a new urban incinerator with energy recovery;

^f l2 is a new regional incinerator with energy recovery;

^g Conventional air pollution damage including UK based damage only;

^h Conventional air pollution damage including UK based as well as that in the rest of the ECE region;

^j Mean values do not necessarily reflect midpoint of ranges due to use of specific statistical techniques.

Note that the study sought to measure the external costs associated with typical tonnes of waste being landfilled or incinerated in different types of plant, and then averaged externalities across types of plant to arrive at a UK figure. It is clear from these results that the relative rates of energy recovery from the two facilities are crucial determinants of their external costs as reported here. This is due to the significance of the pollution displacement assumed to occur as a consequence of that recovery. The study assumed recovery of 664 kWh/tonne MSW for incineration and only 79 kWh/tonne MSW for landfills with energy recovery. We return to this issue in the next chapter.

The external costs that were covered were:

• For landfill: emissions of CO₂ and CH₄, casualties as well as CO₂, NOx and TSP from transport, and reductions in CO₂, NOx, SO₂, TSP and CH₄ from displaced energy sources. A limited attempt was made to estimate leachate externalities whilst acknowledging the limitations of the exercise.

• For incineration: emissions of CO₂, NOx, SO₂, TSP, casualties as well as CO₂, NOx and TSP from transport, and reductions in CO₂, NOx, SO₂, TSP and CH₄ from displaced energy sources.

As such, omitted variables in the valuation work (apart from disamenity) were:

• For landfill: arguably, a full consideration of leachate (BOD, COD, heavy metals and SS), particulates from landfill gas (burned and not burned), and CFCs. There is some discussion of the role of landfills in causing birth defects but the evidence can be considered to be at the level of 'not proven' at present. It is important to note however that some modern engineered landfill sites (e.g. Nant y Gwyddon and Trecatti) are the focus of some of the keenest concern regarding health effects in the UK.¹⁷

[¹⁷ We have not mentioned the fact that the study omitted congestion costs because congestion is not a characteristic of the process per se and should probably be treated in a separate transport module.]

• For incineration: CO, and air toxics such as dioxins, and heavy metals. In addition, to the extent that flue gas is being 'cleaned', the fact that such cleansing simply tends to move the pollutant from one medium to another (from air to water or land depending on the cleaning technology) means that the not quantifying externalities associated with discharges to water or land implies that some pollutants whose impact could be significant escape the analysis. More generally, the benefits of flue gas cleaning would be exaggerated under such an approach. Lastly, external benefits associated with the recovery of metals were ignored.¹⁸

.[¹⁸ See previous footnote]

Note that the study did not ignore these since many were discussed in considering the emissions from landfill and incineration. The problem arises in seeking to quantify impacts associated with these emissions.

The 'omission' of air toxics is an important one, as we shall see, as indeed might be the lack of accounting for materials recovery. With regard to the former, the report noted that 'This component of economic damage is therefore left unvalued in the current exercise, with the balance of probability being that such a value would be close to zero or zero' (our emphasis). The statement is based upon the views of the 1993 Royal Commission on Environmental Pollution report on incinerators that comply with (the then) Her Majesty's Inspectorate of Pollution standards. There is a respectable body of science which contradicts this view. The wording of the statement is also somewhat misleading since the truth content of statements which refer to matters of scientific uncertainty will not, in the general case, be amenable to any 'balance of probability' (see above). There may be a majority view among experts, but experts are not always correct 'on the balance of probability'.

Transport externalities were incorporated into the process of incineration and landfill (through use of typical distances). This makes it difficult to understand the implications of changing distances travelled or modes of transport used. For example, although incinerators may be close to urban centres, larger incinerators may accept waste from more distant conurbations as well. It is somewhat debatable whether consideration of externalities related to waste management facilities should consider transport externalities as part of the 'process related' externality (implying that, in some way, a particular facility always has associated with it a more or less well understood transport externality). To the extent that transport externalities can be altered through changed transportation modes as well as distances, such an analysis appears to obscure the possibilities for improvement, or indeed, for their being addressed by transport policies. Indeed, a number of instruments, notably the fuel duty escalator, have been introduced since the CSERGE work was undertaken. These effectively internalise transport related externalities to some extent.

This suggests an approach which separates out transport externalities from the more 'process specific' ones. This is especially important in considering the potential changes that could occur over time in collection logistics (including vehicle design) and transport modes that might reduce the transport-related externalities associated with waste transport over time. Admittedly, this is more likely to be of importance in the case of recycling, but it is not unimportant in the case of the two options considered by the study.

The study thought that a treatment that differentiated between biogenic and non-biogenic carbon would be better, but that the likely impact upon the results was negligible. This is true if the carbon related externalities are small and known with certainty. It is not true if the estimates are subject to uncertainty (in which case, by definition, we may not be able to assume that they are small). It is clear from the review by Fankhauser and Tol (1995) that attempts to value climate change costs vary with (amongst other things) the discount rate used and the degree to which models incorporate the sorts of low probability high consequence event which are being deployed as a mechanism for 'dealing with' uncertainty.

Another comment worth making is that the study only used a range for the externality adders associated with carbon dioxide and methane, though a range was also used for the valuation of incidents of mortality. In other words, for all other pollutants, only one valuation figure was used. This gives the impression of a level of certainty that is not really warranted given methodological and scientific uncertainties involved, as well as 'measurement' error (in some of the emissions data, for example - see below). On the other hand, the study being an early attempt to generate estimated externalities, the availability of other relevant work was rather less than it is today.

5.2.2 Brisson and Powell 1995

This work updated the CSERGE work discussed above. The results are shown in Table 16.

Table 16: Externality Values for Landfill and Incineration (£/tonne waste other than disamenity)

^a  L1 is an existing urban landfill without energy recovery

^b  L2 is a new urban landfill with energy recovery

^c L3 is an existing rural landfill without energy recovery

^d  L4 is a new rural landfill with energy recovery

^e I1 is a new urban incinerator with energy recovery

^f  I2 is a new regional incinerator with energy recovery

^g Conventional air pollution damage including UK based damage only

^h Conventional air pollution damage including UK based as well as that in the rest of the ECE region

Source: Brisson and Powell 1995

Note especially the source of the major differences between landfill and incineration. These are:

•  leachate;

• the negative externality for methane from landfills, though this is counterbalanced by a higher externality figure for carbon dioxide emissions from incinerators; and

•  crucially, as mentioned above, the pollution displacement effects associated with energy recovery.

We will return to the discussion concerning pollution displacement below. Here, we merely point out that the underlying assumptions concerning both the amount of energy generated per tonne of waste, and the source of energy which is being displaced, appear to be absolutely critical in determining the overall externality. As we shall see, the fact that methane emissions from landfill and associated energy generation from those with energy recovery are subject to some variation makes it difficult to be so certain that the relative benefits lie so strongly in favour of incineration as these figures seem to suggest. The point is reinforced by the fact that the study does not evaluate air toxics.

5.2.3 Coopers and Lybrand / CSERGE 1996

The study carried out by Coopers and Lybrand and CSERGE is of particular interest because it has almost the same focus as our own. The report was conducted for the EU 12 and the base year is early 1990 (1993). Some issues were not considered in the analysis of external costs, for example, the environmental costs associated with different MSW management options, toxic air pollutants from incineration and landfill, and disamenity impacts and leachate (similar points are made by RPA and Metroeconomica 1999).

Factors deemed to be important for determining external costs were:

• composition of waste stream

• size of the disposal site or facility

• physical characteristics of the disposal site

• age of the disposal site, or facility

• spatial location of the disposal site

• level of pollution abatement in a facility

An updated version of the study's results (from DETR 1999a) is shown in Table 17. The ranking of waste management options by total economic (financial and external) costs and by external costs alone is shown in Table 18.

The important step that this study tried to make was the inclusion of recycling in the comparative assessment of waste management options. It is notable that recycling of all materials with the exception of plastic film generates positive externalities. Under the assumptions made by the study, these positive externalities are very large compared to the magnitude of those (positive and negative externalities) associated with landfilling and incineration.

Table 17: External Costs and Benefits of Different Waste Management Options

Source: Adapted from Coopers & Lybrand et al (1997), in DETR (1999a)

Table 18: Ranking of Waste Management Options by Specific Criteria

Source: Coopers & Lybrand et al (1997)

5.2.4 Brisson 1997

Brisson (1997), who was involved in the Coopers and Lybrand study, also assessed the external costs of waste management in the UK under certain conditions. These are shown in Table 19. These were added to the private financial costs discussed in Chapter 3 so as to arrive at total financial and external cost figures for the UK. For recycling, these are shown in Table 20 for the different materials studied.

Again, the significance of assumptions concerning energy recovery is revealed through the assessment of externalities from incineration as displayed in Table 19. In particular, the question as to what energy source is being displaced is shown to be an important one. As with the other studies discussed above, there appears to be little or no attention given to the recovery of metals from incinerators. Given the high value of the positive externalities estimated for each tonne of ferrous metal (see Table 20), these could be expected to have an important effect, even though ferrous metal represents a small fraction of all MSW.

Table 19: External Costs Associated With MSW Management Practices In The UK

uoSource: Brisson (1997)

1.       Table 20: Total External and Financial Costs of Recycling in the United Kingdom

Source: Brisson (1997)

Note that at the material specific level, the external costs vary enormously. This is a characteristic of studies that have been undertaken thus far and indeed, was suggested by earlier work undertaken for us by CSERGE in the context of a study for DETR (ECOTEC 1999).

In addition, one should point out that some materials which are frequently included in household collections, such as textiles, are rarely analysed in this way. As mentioned in Chapter 4 above, the rationale for schemes to collect one or other material varies from scheme to scheme. To our knowledge, no scheme bases this decision on an assessment of external costs (though one scheme we interviewed had carried out such an analysis on the basis of numbers reported in ECOTEC 1999), since more pragmatic approaches and the application of logical principles tends to suffice. Such principles might include a desire to prevent inappropriate disposal of, for example, paints, or oils, or batteries.

5.2.5 Powell et al 1996

The study by Powell et al (1996) is exceptional in that it looks at specific recycling systems. A comparison was made not only between recycling and landfill, but also between two different types of recycling scheme, a kerbside operation in Milton Keynes and a bring system in South Norfolk. The former employed a MRF to separate materials. It is notable that the MRF, whilst not exclusively used for the purpose, was used principally for the separation of plastics from the mixed recyclables (see comments at the close of Chapter 4).

One of the assumptions - that the distance each tonne of each material is transported is the same - appears questionable. Presumably, the overall distance travelled in the kerbside collection ought to be apportioned across materials in relation to the densities of collection. In this case, the distance travelled per tonne of paper collected tends to be much less than that for plastics. This is certainly what one witnesses in reality, and it is this that influences decisions as to whether or not to collect specific materials (if not in terms of the external costs of doing so, then certainly in the private costs).

Another assumption made was that the energy used in the MRF can be apportioned equally across materials (with the exception of glass). Whilst less questionable in the context of the scheme, the discussion at the close of Chapter 4 speculates that the inclusion of plastics may be an important (though by no means the only) factor in arriving at decisions as to whether or not to operate a MRF. Again, it should be noted that the study chose to use only one externality adder in the computation of external costs (i.e. no ranges were used).

The key results of the comparison between the two schemes are shown in Table 21 below. These suggest that on the basis of this analysis, the kerbside scheme performs somewhat better than the bring scheme. However, one should note that the figures in respect of private costs that the study uses for the two schemes are quite different to those which are found elsewhere in the literature (see above, and also Audit Commission 1997; Atkinson, Barton and New 1993). The study itself notes this and suggests that when different figures are used for the private costs, the ranking of the schemes could change.

Table 21: Comparison Of Kerbside And Bring Schemes' External, Private And Total Costs (£ Per Tonne Material)

Source: Powell et al 1996

In the comparison between landfill and recycling, the same study suggested that net benefits from recycling arise in the case of aluminium, paper, steel, and glass but that small net disbenefits arise in the context of recycling HDPE, PVC and PET (see Table 22).

Table 22: Economic Valuation of Environmental and Social Impacts Associated with the Use of Primary Materials and Landfilling Waste, And the Use of Secondary Materials and Recycling (£/Tonne Each Material)

Source: Powell et al 1996

It is interesting that the study does consider variation in private costs but not around the adders used to assess external ones. There is sensitivity analysis conducted around the issues of transport distance and emissions related to recycling and secondary processing, respectively, but the adders appear to have been given a special status in the analysis, despite the fact that uncertainty here is significant.

Note also that the percentage reductions associated with secondary materials processes are closely correlated with energy use. This reflects only partly the significance of energy. More precisely, it reflects both the significance of energy use in materials processing relative to transport energy, and the fact that the externalities assessed have been limited to gaseous emissions and transport.

5.3 Studies Concerning Paper

There have been a number of studies, not only focused on the UK, which have sought to answer the question of what to do with paper. The life-cycle debate here is especially awkward since so any of the key effects are not at all well suited to treatment through life-cycle approaches. The loss of biodiversity associated with the replacement of natural forests with plantations cannot adequately be captured by a technique which at best quantifies land disturbance, but more generally, focuses only on inputs and outputs to a process (as opposed to losses contingent upon certain activities taking place). The valuation of biodiversity loss and / or types of landscape are especially problematic, but extremely high values are frequently found in the literature so these are important impacts. It is also worth stating that they do occur since there have been attempts to downplay the impact of the paper industry on biodiversity. Some of these issues are discussed in Leach et al (1997), Ecologika (1998), and Pearce (1997) amongst others (see also Carrere and Lohmann 1997).

5.4 Summary

In the main, the studies reviewed have indicated a favourable view of recycling on environmental grounds. In the US, a study by Ruston and Denison (1996) has made similar claims for recycling in the sense of the benefits in respect of resource conservation, pollution reduction, and energy conservation (as much as £110 per tonne of waste recycled, though like the studies discussed here and own, which follows, this could not be termed a complete analysis).

However, a lengthy list of caveats ought to be attached to any attempt to derive firm conclusions from the analysis in these studies. None of the studies are 'complete' and most have flaws. Some important inter-related points, which arise from the consideration of existing studies, are made below:

·         There is likely to be some difficulty in measuring and specifying the emissions from different waste treatment plants, as well as from the activities which are 'avoided' through the recovery of energy and materials. This is because a) plants are not uniform (and different pollution control measures determine the media to which emissions are ultimately sent); and b) the composition of waste entering the facilities will vary and this will affect emissions (and different plants are more or less sensitive to fluctuating composition of inputs). Hence emissions may fluctuate across plants, and within a given plant, over time.

·         Equally importantly, to the extent that one might wish to use such analyses for policy making, the 'typical', or 'average' performance of a specific type of plant will change over time. Life cycle inventories provide snapshots of what may be happening at a given moment in time, but technological change can alter the picture quite quickly. LCA, with limits as mentioned above, provides a static picture the utility of which for decision-making purposes falls with the longevity of the installations being considered (because it is impossible to understand how alternatives will evolve over the period).

·         Changing policies can affect the significance of analyses undertaken in the past. To the extent that past studies incorporated transport externalities within the externalities associated with a given process, policies designed to internalise these presumably affect the policy conclusions that might be drawn from those earlier studies. Hence, to the extent that the work by CSERGE et al (1993) was used to inform the decision as to the level of the landfill tax, and because this attributed transport-related externalities to waste treatment processes, consistency might have suggested that the landfill tax should have fallen as fuel duty increased. That government chose to do the opposite suggests, possibly, a welcome departure from the somewhat rigid view that taxes must somehow be justified by economic valuation, especially since it is known that such valuations are rarely complete or free from significant uncertainties.

·         The state of knowledge concerning the effects of all the pollutants examined, atmospheric and otherwise, is typically in a state of flux. The effects of particulates on health, for example, are now suspected to be greater than had hitherto been assumed. Carbon monoxide is another pollutant whose impacts are believed to be in need of re-appraisal in the context of air quality debates (not just inside the home). Recent studies of stratospheric ozone depletion may also implicate carbon dioxide in the process. There is an ongoing debate about the health effects of landfills. The role of NOx (through related ozone production) may be very important in terms of impacts on human health.

·         A general criticism, and an extremely important one that follows from the above point, is that the many studies appear to take only one value of the externality adder for a number of the pollutants examined. Given that a number of such estimates are available (many of which themselves use ranges for the pollutants concerned) the studies are assuming that the level of accuracy of such estimations is beyond what can realistically be accepted. The danger in such an approach is that where the possible range of externality adders is high, or where the environmental effect is not understood with any certainty, one is implicitly introducing an entirely subjective element into the studies. Indeed, the valuation of specific effects approaches a sort of 'lucky dip' in which one's choice of externality adder / dose response function inevitably influences the study's conclusions. In defence of studies undertaken, the earlier works had rather less to draw on in the way of work undertaken in the field. This would have been another reason to stress caution in interpretation of results, especially where it was intended to base policy upon them (as appears to have happened in the case of the Landfill Tax).

·         None of the studies comes remotely close to being 'complete' in the sense of valuing all impacts associated with all emissions to all media from all options (arguably once again reflecting a lack of research in the area). One reason one could venture for this, related to the previous point, is that they couldn't hope to do this with any degree of certainty. There is an 'air emissions' bias to those studies undertaken. Even here, however, few studies look beyond SO₂, CO₂, NO_x, and PM₁₀. They tend to concentrate upon a relatively narrow range of atmospheric pollutants for which externality adders, or dose-response relationships (in respect of damage to health, buildings and crops) are readily available (if not always entirely 'cast-iron' in their scientific validity). This means that assumptions concerning the displaced energy source are also extremely influential (see next point). One can say that 'valuation does what valuation can'.

·         As regards landfill and incineration, the suggestion from past studies is that the data concerning the amount energy recovered, as well as the assumptions concerning what environmental burdens might be being avoided, are crucial in determining the externalities, such as they have been measured, from these two technologies. Note that, with regard to the landfill tax, there would appear to have been a strong rationale for differentiating between those landfill sites accepting biodegradable waste that had no gas collection equipment in place, and those that did. This will become less relevant in the future since the Landfill Directive will require installation of gas collection equipment at such sites. Even now, this approach could speed up the introduction of this technology. It will seem odd, perhaps even bizarre, to many observers that the externalities from landfill or incineration are so heavily contingent upon one's assumptions about what is (or is not) going on somewhere else. At least in the case of recycling, the decision is somewhat more clear cut. However, even here, matters will become more complex once recovered materials of one type replace primary materials of another (as would happen under some of the more positive market development scenarios - see IWA 2000; Enviros - RIS 1999).

·         The externalities associated with recycling of specific materials vary from one material to another. Because of the way these studies have been carried out (specifically, the air emissions bias), the favourable view of recycling (and the differences between materials) is closely related to the issue of energy saving.

·         The impacts of reduced materials extraction - the most obvious of the benefits generated by recycling - is almost routinely ignored as an environmental benefit in the valuation context. One reason for this is that such quantification would be extremely difficult to do. Hence, the results of valuation studies concerning waste management do not necessarily reflect the actual environmental burdens that are related to the approaches under examination. Most studies address these externalities only through assessing the scarcity of resources, and the assumption usually employed is that market prices accurately reflect scarcity.

·         Because most studies account for transportation effects though a specific level of transport externality, the potential for reducing environmental impacts through measures which have next to nothing to do with the actual processes to which the waste is ultimately subjected is made more obscure. Equally, the significance of policies designed to already address transport effects might be overlooked. Ecologika's (1998) work is a good example of a study that explicitly recognises the need for planning in relation to transport at the same time as one plans for waste since each has implications for the other.

·         No study has taken a look at the whole range of materials which kerbside collections collect. These can include oil, paints, and almost always, textiles. It would be extremely difficult to look at textiles in the LCA context given the diversity of materials (and their origins) used in manufacture. Secondary clothing exports may also have ramifications for local textile manufacturers where they effectively compete in local markets (giving rise to social effects through the price depressing effect this may have).

In response to some of these criticisms, commentators might claim that, for example, the most significant pollutants are those related to health and that most of the more significant ones are covered in the studies. However, this is certainly not the case where air toxics are concerned (a laudable exception in that it seeks to tackle air toxics, is AEA's (1997) study, and the same study applies more than the normal level of caveats. ERM's (1998) study, taking its cue very strongly from the AEA work, also included these impacts). Furthermore, to the extent that the emissions of certain pollutants to water may lead to damage to aquatic ecosystems, the externalities may not be small. Certainly, just because little is known about these externalities, there is no obvious reason to assume this implies negligible magnitude, especially given the (likely) location specific nature of the impacts. This is important since, for example, in the case of incineration, what would otherwise become air pollutants are being extracted from flue gas and discharged to other media. Under the current state of the art, this would lead to on overstated benefit (associated with cleaning flue gas emissions) in economic terms since valuation work aimed at understanding what the impact of discharging these pollutants to land or water might be has not progressed very far. This partly reflects the particular problems one encounters concerning benefits transfer in this field.

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