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Substance Flow Analysis for Dioxin 2002

7 Total picture for Denmark

7.1 Formation and consumption

The dioxin brought into circulation in the Danish society and emitted to the environment in Denmark partly originates from processes taking place in Denmark and partly from raw materials extracted and manufactured in Denmark or imported.

Table 7.1 summarises the available estimates regarding formation of chlorinated dioxins in Denmark and the extent to which these estimates are based on Danish investigations or literature values.

The calculation of formation of dioxins by each activity or process takes into account the amount emitted to air and water as well as the amount collected and disposed of with waste products including waste products being exported. Formation does in principle also include the amount created in the products manufactured, but no information has been available to allow estimates of these quantities that to the best of knowledge regarding chlorinated dioxins are also insignificant in Denmark, but could well be important to brominated dioxins in plastics containing brominated flame retardants.

The total formation of chlorinated dioxins in Denmark in 2000 - 2002 is estimated at 72-689 g I-TEQ/year. The most important activity is waste treatment and disposal activities of which municipal waste incineration is the dominant source for dioxin generation. Several other activities are, however, also adding significantly to the total formation. These activities include private wood stoves and other smaller biomass combustion plants, as well as fires, both accidental fires and other fires like the dominant Danish bonfire event - sankthansaften (midsummer day).

The formation of dioxins is widespread in the society, as it e.g. is connected to all types of combustion processes. It is noted that for several activities the formation cannot be quantified due to lack of data. It is, however, believed that the results presented in this report cover all major activities relevant in this context.

The large intervals given for most activities in table 7.1 reflect the uncertainty of the estimates. These uncertainties are partly related to the absence of reliable Danish data making it necessary in many cases to rely on international literature data. As dioxin formation is extremely process specific, this calls for a very critical attitude to all available data and in particular to whether the data available are representative to the process in question. However, the uncertainties also reflect the fact that for several important activities, e.g. fires, the knowledge available is actually inadequate, and the estimates presented may in reality only be justified by the need for obtaining an impression of the significance of such activities. It would be fair to conclude that dealing with dioxins is a matter of dealing with a host of uncertainties.

To make the picture complete, it is also necessary to consider the amount of dioxins brought into circulation by raw materials extracted and manufactured in Denmark or imported to Denmark. In table 7.2 the available estimates on this topic are summarised.

As stated in table 7.2 around 10 -1110 g I-TEQ/year should be expected to be in circulation of chlorinated dioxins alone. To this figure may be added brominated dioxins that are primarily brought into circulation by the use of brominated flame retardants in plastics.

Table 7.1
Formation of chlorinated dioxins by activities/processes in Denmark 2000 - 2002

Table 7.2
Presence of dioxins in products brought into circulation in the Danish society 2000 - 2002

The dominant part of the quantity stated in table 7.2 will most likely be destroyed by heating or incineration processes, thus never being emitted to the environment. This is the case for dioxins in clay that are dominantly used for tiles, bricks and insulation materials manufactured of hightemperature processes. This is also the case for the dominant part of brominated dioxins, as they should be expected as plastics to be directed to municipal waste incineration.

However, this fate is certainly not the case for all types of products. Dioxins in feedstuff will partly be re-circulated to farmland by manure, dioxins in paper and cardboard will likely continue to be re-circulated for paper/cardboard manufacturing and preserved wood and leather may to some extent remain in the society, and slowly release dioxins to air by evaporation. A new measurement of air emission from a Danish edible fish industry has shown a dioxin level of 0.001 ng I-TEQ/Nm³. The source to the measured dioxin is difficult to explain as no combustion processes take place. The air emission can however indicate that some of the dioxin in the fish might be measured in the air emission.

The assessment of the consumption of dioxins by products should for many reasons be regarded as premature. An important reason is that so far insignificant efforts internationally have been devoted to products, and measurements are generally few and old and in no way systematic. The recognition of the presence of dioxins in natural clay is mainly due to a larger investigation reported recently. The question naturally arises whether dioxins might not be present in other sedimentary materials like e.g. lime or chalk. Despite these uncertainties, it is deemed relevant to bring forward these estimates in order to illustrate the magnitude of the dioxin flows in question.

7.2 Emissions to the environment

Table 7.3 summarises the estimates made with respect to emissions to the environment and quantities directed to depots in Denmark.

7.2.1.1 Emissions to air

In 1999 incineration of hazardous waste was a significant source as well, but the contribution from this source has been heavily reduced since 2000 due to redesign of ovens and installation of dioxin abatement. Other sources for emission that could be significant include cable scrap reclamation, lime and cement manufacturing, traffic, and landfills that in this context cover fires in temporary depots for combustible waste.

Concerning municipal waste incineration more plants are in the process of installing special dioxin abatement and the dioxin emission to air must thus be expected to decrease in the years to come. All municipal waste incineration plants must comply with the limit value of 0.1 ng I-TEQ/Nm³ before 2005. By the end of year 2002 2/3 of the Danish waste was incinerated at waste incineration plants which are capable of complying with the new limit value for dioxin of 0.1 ng I-TEQ/Nm³/Danish EPA 2002/. Most of the remaining waste incineration plants are planning to install dioxin abatement before the end of year 2004.

Biomass combustion in small units without flue gas cleaning like wood stoves, farm boilers and stoker boilers is deemed an important source although the estimates are subject to significant uncertainty. For wood stoves it is known that burning of pure wood only is hardly a serious problem. However, adding other materials like paper, milk cartons, plastics or treated wood into the stove should be believed to promote dioxin formation e.g. due to the use of copper pigments in such materials. Considering that around 370,000 wood stoves are being used in Denmark by households, one should be prepared to accept a high level of variation with respect to the materials burned. With respect to the use of treated wood attention should e.g. be paid to the fact that very few people - if any - are able, without measurements, to determine whether the disposable pallet cut to pieces to be used as firewood has actually been treated with PCP or not. One may also discuss how many Danes actually have knowledge enough to care.

The Danish Environmental Protection Agency has in 2001 introduced an information campaign on private wood stoves and dioxin. The effect of this campaign can however not be evaluated as measurements on flue gas from private wood stoves is not present on a larger scale. The focus on dioxins from combustion of biomass has also led to several new measurements on residues from larger biomass combustion plants have been made in 2002 by the National Environmental Research Institute, and these results decrease the interval for residues from 0.04 - 36 g I-TEQ/year to <0.001 - 0.04 g ITEQ/ year.

Concerning farm boilers existing measurements have shown high variation of dioxin emission, and there is certainly a need for a better understanding of the factors causing this variation. As for wood stoves, one should be prepared to accept that also farm boilers are used for a number of other materials besides pure straw.

The contribution from other larger biomass combustion plants equipped with flue gas cleaning seems to be small compared to wood stoves, farm boilers and stoker boilers. In this context the larger plants should be expected to benefit from considerably better control of the materials burned and of operations in general. However, the number of other types of measurements carried out so far is still small and may not necessarily be representative to the total number of plants in operation.

Concerning evaporation from PCP-preserved wood the dominant part of the emission is due to old construction wood (from before 1980) in houses etc. all over Denmark. This emission will continue, until the wood in question has been naturally replaced. This should be expected to take place within the next 20 years, in which period the emission will gradually decrease. However, emission from PCP-preserved materials will continue taking place, as long as PCP is produced and used in the world. Dioxins are a natural contaminant in PCP and the increasing globalisation ensures that chemical substances used for industrial production in other regions of the world to some extent also will end up in Denmark.

Table 7.3
Estimated emissions/losses to the environment and depots in Denmark 2000 - 2002

Accidental fires etc. are a source recognised, but not quantified in most dioxin inventories, as the factual knowledge available is small and all estimates thus are highly uncertain. The basic problem is that it is difficult to undertake realistic experiments or to undertake actual measurements of the emission to air. Still the significance of fires for dioxin formation and emission should not be underestimated. It should be noted, that fires cover accidental fires in building, vehicles etc. for which a mixture of many different materials containing all the elements needed for dioxin formation are present, as well as bonfires, garden fires etc. dominantly based on pure wood but occasionally involving other materials, too.

Steel and aluminium reclamation together with incineration of hazardous waste and perhaps also cable scrap reclamation, cement and lime manufacturing are examples of single plant sources that should be considered significant at least in the perspective that one is dealing with the emission from a single plant. It should be noted that emissions from these companies can always be debated, based on the fact that spot measurements - even based on a standard procedure of 6-hours sampling - will normally not represent the total emission from such plants, and little experience exist to allow the importance of deviating process conditions to be assessed. This issue is further elaborated below. Concerning the estimated emission from steel reclamation in Denmark, the choice has been made to rely mainly on the company's own measurements.

A special source developed in Denmark in the last years is fires in temporary depots of combustible awaiting adequate incineration capacity to be established. This source is in table 7.3 included under "landfills". The comments relevant to this source correspond by and large to the comments given above on accidental fires etc.

The sometimes very large ranges given for most emissions reflect to the best judgement of the authors of this report the uncertainty actually related to the estimates presented. An issue, however, not necessarily fully covered by the ranges presented, is the consequences of deviating process conditions. As dioxin formation is extremely process dependent and the actual formation may differ considerably from "normal" process conditions to "deviating" process conditions, deviating process conditions may contribute significantly to the total dioxin formation and emission. E.g. even if deviating process conditions only rules 5% of the total operation time for a specific plant the dioxin formation during this time could perhaps be 10-100 times higher than under normal process conditions. It is the impression of the authors that most of the emission factors reported reflect normal process conditions and thus do not include the consequences of deviating process conditions. In this report the consequences of deviating process condition have been considered in relation to steel reclamation and to one municipal waste incineration plant. Only little factual knowledge is available on this issue, but the significance to the total emission should not be overlooked.

On the basis of the measurements on brominated dioxins in flue gas from Kommunekemi and Vestforbrænding the annual emission of brominated dioxins is estimated to be approximately <0.01 - 0.1 g I-TEQ/year. This estimate is very uncertain because of the few measurements and the variable processes used for waste incineration and cleaning of flue gasses. Furthermore there is no official method for calculating an I-TEQ-value, and the estimate does not include all measured congener groups, as it has only been possible to calculate I-TEQ-value for the specific congeners. The non specific congener groups are therefore not included in the interval of 0.01 - 0.1 g ITEQ/year. This emission value represents with certainty an under estimate of the reel emission, but any estimate of the reel emission value must be regarded as highly uncertain. Based on an anlysis of the chromatographies for the congeners it is estimated that the reel estimate can be up to approximately a factor 5 higher, but most likely not a factor 100 /Vikelsøe, 2003a/. This value is not a part of the total emission to air and figure 7.1 because of the uncertainty of the estimate.

Emissions to water

The total emission to water environment is estimated at 0.4 - 1.4 g ITEQ/ year. The estimate should be regarded as uncertain, as only few measurements are available.

Based on the available knowledge the most important source for dioxins in Danish waste and storm water seems to be atmospheric deposition (reference is made to table 5.5), but observed congener profiles for dioxins in sewage sludge only partly correlate to profiles for atmospheric deposition. Some correlation to congener profiles for textiles may also be argued. A definite conclusion on sources for dioxins in wastewater and sewage sludge should however so far be considered premature.

Emissions to soil

The total direct emission of dioxins to the soil environment is estimated at 0.7 - 42 g I-TEQ/year. The dominant sources are residues from miscellaneous fires and manure from domestic animals applied to farmland.

Other minor sources seem to be the use of pesticides and sewage sludge. It is, however, strongly emphasised that all estimates apart from sewage sludge are highly uncertain, as they are generally based on very few data of which most originates from foreign investigations. One must be prepared to accept that further and more detailed investigations could change the picture considerably. E.g. knowledge of the content of dioxins in pesticides should be regarded as almost non-existing, and more detailed investigations could perhaps identify pesticides as a significant source.

The focus on ash from wood stoves relates to that ash may frequently be directed to garden composts or directly spread on the soil in gardens. Similar behaviour should be expected for farmers operating farm boilers.

Residues from fires deal with ash etc. from other fires than accidental fires - e.g. garden fires and bonfires - not removed from the place of the fire and in time mixed into the soil.

Manure from domestic animals is generally applied to farmland and will contain dioxins originating from the feedstuff. As detailed investigations of the turnover of dioxins in the Danish agricultural sector are not available, the estimated supply should be regarded as a rough first estimate indicating the relevant order of magnitude.

Losses to depots

The total quantity of dioxins directed to landfills and other types of depots in Denmark is estimated at 5 - 126 g I-TEQ/year. Municipal waste incineration is no longer the dominant source because the flue gas treatment residues are exported. The major sources are dioxin residues in PCP-treated wood and residues from coal combustion however neither residues from steel and aluminium reclamation, biomass combustion nor fires should be overlooked. The significant quantities of dioxins ending on landfills naturally call for more knowledge of what is actually happening to dioxins within landfills.

Export

The data in the category "export" cover products and residues which have been exported from Denmark. The total amount of exported dioxin in the Danish society equals approximately 55 - 413 g I-TEQ/year. This amount has grown because of the export of flue gas treatment residues from the Danish waste incineration plants.

Uncertain estimates

Comparing table 7.3 and 7.4 it is clear that it is the emission to air and depots that is considerably influenced by the uncertainty from the abovementioned categories.

2000 - 2002 emission compared with 1998-1999 emission

Table 7.5 shows the estimated annual dioxin emission in the period 1998 1999. /Hansen, 2000/. Comparing the results from SFA 2000 with the results in table 7.3 it is clear that the data quality has been improved, especially for industry and waste treatment processes. However it is primarily dioxin emission to air that has been investigated during the past two years, and this means that the estimates of emissions to soil and water have not been improved.

Looking at the total dioxin emission to air there has been a reduction in the best estimate from 95 g I-TEQ/Nm³ in 1998 - 1999 to 87 g I-TEQ/Nm³ in the period 2000 - 2002. This reduction is caused by lower emission levels primarily for steel and aluminium reclamation, cable scrap reclamation, hazardous waste and municipal waste. Especially the dioxin emission from the municipal waste incineration companies has decreased. The main reason behind the decreased emission is improved dioxin cleaning caused by installation of dioxin abatement.

The categories Municipal waste, Steel- and aluminium reclamation, Fires, Evaporation from PCP-preserved wood and Biomass combustion were in 1999 considered to cause considerable dioxin emission. Out of these five categories new measurements have only been available for Municipal waste and Steel and aluminium reclamation. The new data from Steel and aluminium reclamation have resulted in the fact that this category no longer can be seen as a dominant source because of the reduction of the emission level.

Table 7.5:
Estimated emissions/losses to the environment and depots in Denmark 1998-1999.

1998-1999 emission compared with 1995 emission

In SFA 2000 /Hansen, 2000/ a comparison between the results from 1998- 1999 and 1995 emissions was made. This comparison is maintained in the update of the substance flow analysis for dioxins to show the development in emission sources and emission level.

The figures presented in table 7.5 may be compared to previous estimates of dioxin emissions in Denmark presented in table 7.6. The main differences between the previous estimates and the present are due to the following:

That the previous estimates have generally been expressed as "best estimates" giving relatively little consideration to the significant uncertainties connected to the estimates.

That the present estimates have included a number of sources previously not quantified, e.g. fires and PCP-treated wood

That the present estimates benefit from the significant knowledge developed internationally and in Denmark in the recent years and e.g. has included all measurements known to be available from Denmark.

Other differences may be due to different interpretation of the available data. It should e.g. be noted, how the estimates of biomass consumption and in particular wood stoves fluctuate.

Whereas Denmark emits dioxins to the air, Denmark also receives dioxin from the air by atmospheric deposition. The deposition on the Danish land area is on the basis of measurements from The National Environmental Research Institute estimated at 13 - 130 g I-TEQ/year assuming a total land area of 44,000 km² (reference is made to chapter 6). The given interval does not include:

The uncertainty coming from the fact that the measurements originate from only two locations and in addition that the measurements encompasses only one single year. This uncertainty is at the time being very difficult to assess.

Uncertainty coming from the fact that no measurements so far have been carried out in urban areas and in the vicinity of point sources.

The calculated total contribution from dioxin sources to waste water is approximately of 0.4 - 4.8 g I-TEQ/year of which atmospheric deposition from the Danish land area served by sewage systems, equals 0.4 - 4 g ITEQ/ year. The interval for dioxin sources should be taken as comparable to the estimated total content in discharged waste and storm water of 0.4 - 1.4 g I-TEQ/year and the calculated total content in sewage sludge of 1.2 - 2.3 g I-TEQ/year (reference is made to section 5.7.2). These observations indicate that the contribution to waste water treatment plants in Denmark is at least 1.6 - 3.7 g I-TEQ/year and it also indicates that the stated deposition level is a realistic estimate.

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