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Substance Flow Analysis for Dioxin 2002

2 Formation and turnover by industrial activities

2.1 Chemicals

Manufacturing of chemicals in Denmark is dominated by pharmaceuticals, pesticides, cleaning agents and food additives. Only few manufacturing processes utilise temperatures above 200 C and involve an intended presence of halogens, such as chlorine. Based on contact to the relevant Danish companies, it seems that the dominant potential process for dioxin formation in Danish chemical industries would be elimination of gases vented from manufacturing processes by high-temperature burning (800-1000 C). This process is relevant to one pesticide manufacturing company and one pharmaceutical company. To the best of knowledge, the use of chlorine for industrial processes in Denmark is dominated by 3 major companies including the two companies mentioned above. The third company in question deals with vitamin manufacturing and is discussed in section 2.8.

There are no indications of potential dioxin formation in Danish industries involved in manufacturing of cleaning agents or food additives.

2.1.1 Pesticide manufacturing

The pesticide manufacturing company uses chlorine in the production, and the air is before emission burned in a ceramic filter at 800-850 C. In 1991 the dioxin emission was measured to 1 ng total dioxin/Nm³ corresponding to a total emission of 0.4-0.5 g total dioxin per year. No recordings of collected filter dust have been made, as the quantity is assumed marginal.

The dioxin concentration in the air flow after the burning process has been measured again in June 2001. The measurement showed a concentration of 0.006 ng I-TEQ/Nm³. The airflow is estimated at 400 million Nm³/year, and the emission per year is therefore approximately 0.8-7.1mg I-TEQ/year. No knowledge from similar processes abroad is available.

The company furthermore practices combustion of wastewater and flash drying of sludge. Air emission from combustion of wastewater has been shown in 1995 to contain < 1 pg N-TEQ/ Nm³ equalling an emission of < 90 m g N-TEQ per year. Drying of sludge from production processes takes place in a flash drier by 750-900° C warm air heated by burning of natural gas. The air passes a filter bag at about 130 C. Filter dust is returned to the sludge that after drying is utilised for agricultural purposes. No measurements of dioxin in air emission nor dried sludge have been carried out. No knowledge from similar processes abroad is available. The airflow is approx. 80 million Nm³/year, but in absence of actual measurements it is not possible to make an estimate of the emission to air from the process. It is not possible either based on the existing knowledge to assess the potential amount of dioxin directed to farmland with sludge.

The present knowledge may be summarised to the following: Some emission of dioxins takes place to air besides that dioxins are applied to farmland by sludge or directed to landfills as filter dust. As the existing measurements are incomplete and old, and thus may not be reliable, it is not possible to quantify the emissions in question.

2.1.2 Manufacturing of pharmaceuticals

The pharmaceutical company uses chlorine in the production, and the off-gases are before emission burned in a sand filter at 900-1000 C. No measurements of dioxin emission have been undertaken. The airflow through the filter is approx. 600 million Nm³/year. Again no recordings of collected filter dust have been made, as the quantity is assumed marginal. In absence of actual measurements it is not possible to make estimates of the emission to air or the amount of dioxins directed to landfill as filter dust.

2.1.3 Chemical products

It is known, that a number of chemical products may contain dioxins:

Bleaching agents

Bleaching agents containing hypochlorite salts may contain 5 pg I-TEQ/litre /Jensen 1997/. The use of hypochlorite and similar chemicals in Denmark is dominated by sodium and potassium hypochlorite, and the consumption of sodium and potassium hypochlorite in the middle of the eighties has been estimated at around 15,000 tons/year /Danish EPA 1989/. Assuming that the consumption of bleaching agents has remained unchanged, the consumption of dioxins may be roughly estimated at <1 mg I-TEQ/year. This consumption will primarily end in wastewater.

Pesticides

Dioxin has been registered in a number of pesticides, and other pesticides are suspected to contain dioxins due to formation during manufacture. The relevant pesticides are listed in /Costner 1999/ and /Jensen 95/. Of these pesticides the following were used in Denmark in 2001 /Bekæmpelsesmiddelstatistik 2001/:

Table 2.1
Danish consumption of pesticides confirmed or suspected to contain dioxins, 2001

Investigations of the content of dioxins in pesticides sold in Denmark are scarce. In Danish investigations from 1987 (quoted in /Jensen 95/) the dioxin content of dichlorprop was measured to 0.35 µg I-TEQ/kg, whereas the dioxin content of MCPA and mechlorprop was determined to 0 µg I-TEQ/kg, as only non-toxic congeners were present in MCPA and mechlorprop.

Assuming that other pesticides than MCPA and mechlorprop would have the same dioxin content as dichlorprop, the consumption of dioxin with pesticides in Denmark was in 1998 roughly calculated to be 56 mg I-TEQ/year. As the annual amount of pesticides has been reduced from 1998 to 2001, it is still reasonable to expect that the consumption of dioxin with pesticides is still less than 1 g I-TEQ/year, taking all uncertainties related to lack of complete and updated information into account. This consumption will primarily end in soil.

Brominated flame retardants

Brominated flame retardants are suspected to be a significant source for brominated dioxins. Brominated dioxins occur in the commercial brominated flame redardants and are furthermore created by manufacturing and other processing (including recycling) of plastic products based on flame retarded resins /IPCS 1998/. Brominated dioxins are also formed by burning of plastic products containing brominated flame retardants /IPCS 1998/.

Brominated flame retardants form a diverse group of compounds and the dioxin content is highly varying among the specific compounds. According to the IPCS review, the highest levels of PBDDs/PBDFs are found in materials flame retarded with PBDEs (polybrominated diphenyl ethers) exceeding the dioxin levels of other polymer/flame retardants systems by several orders of magnitude. The levels of PBDDs/PBDFs in polymers with PBDEs were in the range of several thousands mg/tonne. The review, however, does not give any information on the dioxin congener patterns of the specific polymer/flame retardants systems. Other information, however, indicates that the content of the toxic congeners in polymers is significantly higher in polymers flame retarded with PBDE. The German Dioxin Ordinance specifies the maximum allowable concentration of a number of 2,3,7,8-substituted PBDDs/PBDFs in products marketed in Germany. As a consequence of the ordinance, PBBs (polybrominated biphenyls) and PBDEs have been replaced by other flame retardants in the German industry, because the dioxin content of the PBDE containing polymers often exceeded the maximum allowable (ZVEI 1988). Until July 1999 the Ordinance prohibited any product containing more than 10 mg/tonne ppb of the sum of four congeners: 2,3,7,8 TBDD; 2,3,7,8 TBDF; 1,2,3,7,8 PeBDD and 2,3,4,7,8 PeBDF whereas the sum of eight other congeners was not to exceed 60 mg/tonne (ppb). By July 1999, the limits were lowered to 1 and 5 ppb, respectively. In terms of toxicity equivalence factors, the actual requirements of the German Dioxin Ordinance correspond to a maximum of less than 2 mg I-TEQ/tonne for the 12 congeners, whereas the requirement before July 1999 corresponded to <20 mg I-TEQ/tonne.

About 90% of the consumption of BFRs with finished products in Denmark is imported, and the flame retardants used in products on the Danish market are most probably the same as in products marketed in Germany.

Dioxins have been detected in PVC, ethylene dichloride and hydrogen chloride /Carroll et al 1999 quoted by Greenpeace 2000/ and dyestuffs /Jensen 1997/. It is deemed likely that dioxins will be present in other products containing chlorine. However, the knowledge available does not allow an estimate of the consumption of dioxins and the release to the environment in Denmark to be made.

2.2 Materials manufactured by high-temperature processes

2.2.1 Raw materials

An investigation of 33 samples of natural clay of various origin (mainly kaolin-clay) has revealed a median content of dioxin of 154 ng I-TEQ/kg dry matter with a variation of 3.9-1132 ng I-TEQ/kg dry matter /Jobst & Aldag 2000/. Parallel to this analysis of kaolin-clay, moler and other materials used as binders in feedstuff in Denmark have shown dioxin content of normally 10-400 pg I-TEQ/kg at 88% dry matter /Plantedirektoratet 2000/. A single sample, however, was measured to 16738 pg I-TEQ/kg at 88% dry matter /Plantedirektoratet 2000/. For moler originating from Denmark was on 5 samples measured an average of 139 pgI-TEQ/kg with a variation of 90-173 pg I-TEQ/kg at 88% dry matter /Plantedirektoratet 2000/. It should be noted that EU has established an emission limit value for dioxin in kaolin-clay for feedstuff of 500 pg WHO-TEQ/kg /Plantedirektoratet 2000/, meaning that the Danish investigations described above for kaolin etc. can only be taken as representative to materials used for feedstuff and not for clay in general.

The origin of the dioxin measured is not known, but may be volcanic eruptions or natural fires in ancient times. It must be assumed that other clay deposits in Denmark and internationally may contain dioxin in small concentrations, although no knowledge of the actual concentrations is available. In the following the concentrations reported above are used for estimating the consumption of dioxin with clay-like raw materials used for manufacturing of construction materials etc. No knowledge exists and no estimate is made regarding the content of dioxin in raw materials like lime and chalk.

Quantities of raw materials

Based on the Danish manufacturing and trade statistics /Danmarks Statistik 2001a and 2001b/, Danish production, import and export of the relevant commodity items in 2001 is summarised as stated in table 2.2 below.

Table 2.2
Statistical data for clay-like raw materials, 2001

Dioxin balance

Assuming dioxin concentrations as follows

The dioxin balance for clay-like raw materials can be calculated as stated in table 2.3.

Table 2.3
Dioxin balance for clay-like raw materials

The balance indicates, despite the substantial uncertainties related to the calculations that the flow of dioxin with clay-like raw materials should be considered significant.

However, apart from the quantities used as feedstuff additives, paper manufacturing and for decoration or educational purposes all clay-like materials in their further life cycle will undergo a burning process at high temperatures likely to destroy most if not all of dioxins present in the materials. The hypothesis has been presented that dioxins present in clay might partly evaporate during the heating process prior to the burning /Ferrario & Byrne 2000 quoted by Greenpeace 2000/. No precise knowledge is, however, available concerning the significance of such evaporation on the emission of dioxins from clay-based manufacturing processes and the extent to which this potential source of dioxins has been considered by the measurements from clay-based manufacturing activities referred in the following section. It is noted that the existing measurements of air emission from clay-based manufacturing processes do not support the hypothesis (reference is made to section 2.2.2 and 2.2.3) that evaporation of dioxins from clay is a significant source for release of dioxins to the environment. Is should be noted, that no measurements of the dioxin content in clay based end products like tile and bricks exist. Thus it is not known, whether some of the dioxin present in the raw materials may survive the heating process and be present in the end products.

Regarding feedstuff and paper product, the content of dioxins in such products is assessed in section 2.4.4 and 2.7.2 respectively.

Regarding clay for decoration and educational purposes, no exact figures of the consumption are available. Assuming as a rough estimate that between 10 and 50% of the supply of "clay-others" stated in table 2.2 corresponding to approx. 900 – 4600 tonnes is used for decoration and educational purposes, the dioxin consumption for these purposes may be roughly estimated at 0.004 – 5 g I-TEQ/year. Clay used for these purposes should be expected to be disposed of partly to household waste directed to incineration and partly to inert waste directed to land-filling.

2.2.2 Clay-based insulation materials

Clay-based insulation materials are manufactured by one Danish company only. Clay is burned at a high temperature in a rotary kiln, in which the materials are heated by warm air. The emission into air contains around 13% O₂ (because of massive surplus of air) and is cleaned by passing an electrostatic precipitator. The temperature in the filter is around 200 C. Clay naturally contains organic matter and chloride, including traces of dioxin (reference is made to section 2.2.1).

Plant activity

Filter-dust is re-circulated into the rotary kiln. Thus no filter dusts for disposal are generated. Production volume figures are confidential.

Dioxin formation and disposal

No measurements of dioxin formation have been carried out by the company. Based on information from the company on air emission volumes and assuming emission rates equal to tile- and brick-working (reference is made to German investigations reported in the European Dioxin Inventory /Landesumweltamt Nordrhein-Westfalen 1997/), the air emission may be estimated (best estimate) at around 0.009 g I-TEQ per year and most likely within the range of 0.0006 - 0.24 g I-TEQ/year.

2.2.3 Tile and bricks based on clay

There are 3 major and about 22 smaller tile and brickworks in Denmark. They use tunnel kilns, where the materials are heated by warm air. The maximum temperature is 1,000-1,050 C that decreases through the tunnel. At the point of emission, the air temperature is in the range of 150-200 C. The content of oxygen in the air stream varies within 10 and 12% in the heating zone and 15 and 18% at the point of emission. Only two of the works have filters. Apart from the natural organic matter in clay, sawdust (about 1%) is added to the clay for yellow bricks (Murværkscentralen 2000). Dioxin formation has been confirmed by foreign investigations (see below).

Plant activity

According to the statistics the total production of clay based tiles and bricks in Denmark in 1998 added up to approximately 450 million pieces /Danmarks Statistik 1999b/. Assuming an average weight of approx. 2 kg/piece the total production volume in 1998 may be estimated at approx. 900,000 tonnes/year.

Dioxin formation and disposal

No measurements of dioxin formation have been carried out in Denmark. Based on German investigations the European Dioxin Inventory calculated an emission factor of emission to air of 0.018 g I-TEQ/ton of material and a variation of 0.001 – 0.23 µg I-TEQ/ton (Landesumweltamt Nordrhein-Westfalen 1997), whereas no figures for filter dust from air cleaning are available.

Based on these figures the turnover of dioxins by tile and brick manufacturing in Denmark may be estimated as follows:

2.2.4 Cement

Cement is manufactured by one plant only in Denmark. The plant operates 7 kilns, of which 3 including the largest are used for grey cement and the rest for white cement. The raw materials for grey cement are sand, chalk and fly ash from power stations, whereas chalk, sand, kaolin and spent catalyst is used for white cement. Cement manufacturing typically involves temperatures up to around 1500° C.

The largest kiln is heated by a mixture of petcoke, coal and industrial waste including plastic (non-PVC), and sludge from paper manufacturing and textiles from tyres. Meat and bone meal is now also being used as alternative fuel for the kiln. Waste containing more than 0.1% chlorine is not accepted. The air emission from this kiln is cleaned in an electrostatic precipitator at 130° C before directed to the chimney. Coal and oil only heat the other grey kilns, and the off-gases are cleaned by an electrostatic precipitator at around 250° C. The air emission from the 4 kilns used for white cement is cleaned first in an electrostatic precipitator at around 300 C and afterwards by a scrubber.

Plant activity:

Based on information from the company a total of approx. 2.6 million tonnes of cement were manufactured in 2001.

In the largest kiln approx. 1.7 million tonnes cement with an airflow of 3150-3500 million Nm³/year was manufactured. In the other kilns approx. 0.9 million ton cement with an airflow of around 3200 million Nm³/year was manufactured, and a discharge of cleaned scrubber water of approx. 400,000 m³ water/year.

Filter dust from electrostatic precipitators is recycled into the largest kiln. Scrubber water is cleaned and the content of solids used for gypsum manufacturing.

Dioxin formation and disposal

Measurements of dioxin emission to air from the large kiln have shown values of <0.6-2.7 pg I-TEQ/Nm³ equalling an emission of 0-9.5 mg I-TEQ/year. The figures reflect normal operation, and should thus be representative of 98-99% of the total production time. In 2001 a new measurement has been carried out at the same kiln. The sample was made while using meat and bone meal as a part of the fuel. The measurement resulted in an emission of 0.035 ng I-TEQ/Nm³ or 0.0001 mg I-TEQ/ton manufactured. The annual emission calculated on the basis of this measurement is approximately 167 mg I-TEQ/year, and this indicate that the dioxin emission increases, when meat and bone meal is used as an alternative fuel in the cement production. This conclusion is however not definitive, as only one measurement has been taken - there may be other influencing conditions.

In 1995 a measurement was made on one of the smaller kilns. The measurement showed a dioxin emission of 0.15 ng N-TEQ/Nm³, which means an annual emission of 162 mg N-TEQ/year. The emission factor is approximately 0.0005 mg N-TEQ/ton. There have not been made any measurements on the relevant kiln since 1995.

No measurements have been undertaken for the other kilns and scrubber water.

The best possible estimate is assumed to be based on the company’s own measurements, although only one measurement has been made on one of the small kilns back in 1995. Using the value from this measurement at the 0.9 million tonnes manufactured on the smaller kilns and the emission factor 0.00001 mg I-TEQ/ton for the 1.7 million tonnes manufactured at the large kiln, the total annual emission is estimated to be in the range of 156 - 1401 mg I-TEQ/year. This interval is calculated assuming an uncertainty of ± factor 3. (reference is made to section 1.5)Best estimate is 467 mg I-TEQ/year.

In SFA 2000 /Hansen, 2000/ the dioxin emission from production of cement was estimated to be approximately 0.045 - 0.92 g I-TEQ/year.

2.2.5 Lime

Burned lime is produced by one company in Denmark. The process takes place in a rotary kiln at 1200 - 1250 C for 2-3 hours (1-2% oxygen at the end of the kiln). The air from this process is used in a cyclone pre-heater at about 700° C. From here the air flows into another cyclone (about 400 C) before it passes through an electrostatic precipitator and out the chimney at about 280° C. The oxygen concentration through these last processes is 8-9%. Dust collected in the electrostatic precipitator and the other cyclone is included in products for flue gas treating e.g. by municipal waste incineration plants. The goods pass the cyclone pre-heater, before it goes into the rotary kiln. From here it goes into a cooler, where the temperature of the goods declines from about 1000 C to about 175 C in one hour. The sources for heating are fuel oil, natural gas and coke. Lime is made from limestone, which being a sedimentary material naturally contains chloride and traces of copper and organic materials. Dioxin formation has been confirmed by measurements at foreign plants.

Plant activity

In 2001 approx. 90,000 tonnes of burned lime was produced /Danmarks Statistik 2001b/.

Dioxin formation and disposal

One measurement of dioxin emission to air from the burning process has been carried out in spring 2001.The measurement was made with combustion of 100 % coal, and the sampling lasted 7.5 hours. The result of the measurement showed a concentration of 0.01 ng I-TEQ/Nm³. This concentration corresponds to an emission factor of approximately 0.02 µg I-TEQ/ton.

Based on this emission factor the current Danish emission is estimated to be approximately 0.6 - 5.4 mg I-TEQ/year, assuming an uncertainty of ± factor 3 of the measurement. (reference is made to section 1.5)

In SFA 2000 /Hansen, 2000/ the dioxin emission from production of lime was estimated to be approximately 0.001 - 2.6 g I-TEQ/year.

European measurements indicate emission factors in the range of 0. 01-29 g I-TEQ/ton /Landesumweltamt Nordrhein-Westfalen 1997/.

Simultaneously with the measurement of the air emission the dioxin concentration in the filter dust was also measured. This measurement showed a concentration < 0.006 I-TEQ/m³, which gives an emission factor less than approximately 0.0009 mg I-TEQ/ton filter dust. The total amount of filter dust is estimated to be approximately 6 tons per year, which results in emission of approximately 0.002 - 0.02 mg I-TEQ/year, assuming ± factor 3 as the uncertainty of the measurement.

Other comments

In 1999 control measurements revealed that lime used in citrus pulp pellets imported to Europe from Brazil to be used as feedstuff was heavily contaminated by dioxins. Further investigations disclosed that the lime used in the actual case was not natural lime, but a waste product from chemical manufacturing /Malish et al 1999/

2.2.6 Other materials

Activity in Denmark

Based on statistics /Danmarks Statistik 1999b/ and other relevant sources the yearly activity in Denmark can be summarised as follows:

Dioxin formation and disposal

Three Danish production sites for insulation materials have made measurements of the dioxin emissions from the production.

One of the plants has measured the dioxin emission in 2000. The measurement was taken in the central smoke stack. The measurement in an emission of 0.012 ng I-TEQ/Nm³ or approximately 25 mg I-TEQ/year This corresponds to an emission factor of approximately 0. 0007 mg I-per ton insulation material produced.

The second plant has measured dioxin concentration in air emission, fly and ash from cyclone cleaning in 2001. The dioxin concentration in the air from the smoke stack was 0.3 ng I-TEQ/Nm³, whereas the content in the ash was 9 ng I-TEQ/kg dry substance. The dioxin concentration in the ash from cyclone cleaning was 109 ng I-TEQ/kg dry substance. The amount of cyclone ash and fly ash is not known, so it has not been possible to estimate annual emission.

At the third plant the dioxin emission to air has been measured in 2001 resulting in an emission of 0.2 ng I-TEQ/Nm³. Based on information from inspection authorities this measurement corresponds to an emission factor approximately 0.0002 mg I-TEQ/ton produced.

It has not been possible to estimate the emission factors for some of the measurements because of lacking information. The two emission factors on 0.0002 mg I-TEQ/ton produced and 0.0007 mg I-TEQ/ ton produced are therefore used to calculate the annual dioxin emission from production of insulation materials.

Using the highest and lowest emission factors and assuming an uncertainty ± factor 3 (reference is made to section 1.5), the annual dioxin emission be estimated to be 12 - 305 mg I-TEQ/year.

The European Dioxin Inventory (section on Germany) and UNEP give air emission factors for glass production in the range of 0.005 – 0.032 g I-TEQ/tonnes of material /Landesumweltamt Nordrhein-Westfalen 1997; UNEP 1999/. No emission factors are available with respect to insulation materials and china/ceramics, but it is assumed that the factor for glass the correct order of magnitude also for these materials. No figures are available for filter dust from air cleaning operations. The dioxin emission to air from production of glass and china and cheramics, is on the basis of assumptions estimated to be approximately 0.003 - 0.02 g I-TEQ/year.

Based on these figures the turnover of dioxins by other high-temperature materials in Denmark may be estimated as follows:

In SFA 2000 /Hansen, 2000/ the dioxin emission from production of insulation materials, glass, china and cheramics was estimated to be approximately 0.004 - 0.024 g I-TEQ/year.

2.3 Metal manufacturing

The assessment presented in the following is focused on metal casting, hot-dip galvanising and metal reclamation, as they are the only Danish metal manufacturing operations so far believed to develop significant quantities of dioxin. It should, however, be noted that dioxin formation by welding and soldering and similar processes has been documented /Menzel et al 1996 and Menzel et al 1998 quoted by Greenpeace 2000/

2.3.1 Metal casting

Metal casting in Denmark is mainly related to the metals iron, copper, aluminium and lead.

Iron casting takes place at around 12-15 plants, and the process conditions will typically be as follows: The iron is mixed with carbon (3-3.5%), silicone and other alloying elements and is melted by electricity. Whereas the temperature of the iron in the melting zone is around 1,300-1,400 C, the air temperature in the melting chamber will normally be around 200 C. The air is renewed continually before being cleaned by a bag filter at a temperature level of 30-40° C. The melted iron is poured into casting moulds made out of sand, bentonite, water and coke. The sand used for casting moulds is normally of inland origin, but may occasionally also come from beaches. To the extent the sand is of marine origin it may contain chloride. The raw material may be scrap iron, but without paint, galvanisation or other kind of surface treatment.

Casting of copper and aluminium and alloys of these metals takes place at approx. 50 plants, whereas lead casting is dominated by 2 larger Danish companies manufacturing batteries and electrical cables. However, a number of smaller companies involved in manufacturing of yacht keels, roof plates and fishing equipment are also active in field of lead casting. No efforts have been invested to obtain further details of manufacturing processes.

Activity

The activity related to iron casting can, based on information from a number of companies, be outlined as follows: The total production comes up to approx. 75,000 tonnes of iron per year. The amount of filter dust generated by the melting process can be estimated at approx. 200 tonnes/year. Approx. ¾ of this quantity is exported, whereas the rest is directed to Kommunekemi as hazardous waste. Casting mould and other waste products counts for a waste quantity of the same size as the amount of iron produced, that is to say around 75,000 tonnes per year and is either landfilled or reused for other purposes /Lemkow et al 1992; Danish EPA 2000e/.

For other metals the material consumption for casting processes is /Lassen et al 1996; Lassen & Hansen 1996; Hansen et al 1999/:

Dioxin formation and disposal

For one iron casting company dioxin emission to air was measured in 1999. The production volume for this company equals approx. 20% of the total Danish production. The production is based on scrap iron. Process air and ventilation is mixed before being emitted through a bag filter. The emission factor was determined to 0.411 µg I-TEQ/ton of material /Fyns Amt 2000/. This may be compared to air emission factors given by UNEP for electrical iron and steel foundries of 0.032 µg I-TEQ/ton of material /UNEP 1999/. Based on local conditions, the Danish measurement is considered a better estimate than the UNEP value.

In the past two years dioxin measurements have been carried out in two Danish aluminium foundries. For one of the productions the measurements showed an emission of 0.002 ng/Nm³, which corresponds to an emission of approximately 0.04 mg I-TEQ/year. This measurement was made in 2001 and gave an emission factor at 0.04 ng I-TEQ/ton aluminium manufactured.

In the second aluminium foundry a dioxin emission of 0.03 ng I-TEQ/Nm³ was measured in 2001. The measurement applies to an annual emission of approximately 0.05 mg/Nm³ and an emission factor of 0.01 ng I-TEQ/ton aluminium manufactured.

For other activities no measurements of dioxin formation have been carried out in Denmark. The European Dioxin Inventory (section on Germany) gives air emission factors for smelting of copper and copper alloys in the range of 0.0008 – 0.84 µg I-TEQ/ton of material and for other non-ferrous metals (tin, cobalt, chromium, nickel, silver, zinc and aluminium) in the range of 0.15-2.4 µg I-TEQ/ton of material /Landesumweltamt Nordrhein-Westfalen 1997/.

Based on the Danish measurements it is chosen to lower the interval for the emission of dioxin to air by metal casting in Denmark to <1 mg I-TEQ/year - 10 mg I-TEQ/year. The estimated upper interval limit has been reduced compared to the 60 mg I-TEQ/year used in SFA 2000 /Hansen, 2002/ because of the low emission level shown by the Danish measurements. No knowledge of dioxin content of filter dust from flue gas cleaning and other waste products seems to be available. It is not known whether any dioxin formation takes place in the casting moulds during the process.

In SFA 2000 /Hansen, 2000/ the dioxin emission from metal casting was estimated to be approximately 0.032 - 0.06 g I-TEQ/year.

2.3.2 Hot-dip galvanising

About 15 companies in Denmark carry out hot-dip galvanising. First the iron is cleaned of organic pollution by the use of tensides, HCl and occasionally also sand blasting. Then the iron is treated with NH₃Cl and afterwards dried, before it is drawn through a zinc-bath of a temperature of 450 C. Despite the efforts to remove organic matter, it is known that the ash layer typically formed on the surface of the zinc-bath will contain organic matter. One company found 6-13% organic matter in this ash. This makes dioxin formation likely. Dioxin formation has been confirmed by measurements abroad.

Plant activity

Based on information from Danish companies, the total production can be estimated at approx. 100,000 tonnes galvanised product per year, whereas the air emission comes up to approx. 33,000 Nm³/tonnes product.

Generation of filter dust from air cleaning varies, as some plants have no cleaning facilities at all (emission of 50 mg dust/Nm³), whereas larger plants generally are equipped with bag filters allowing an air emission of less than 0.5 mg dust/Nm³. It is known that one major company produces 8-10 tonnes of filterdust per year. The quantity of filter dust generated may thus be assumed to be somewhat between 20 and 165 tonnes/year.

Filter dust is directed to land-filling or temporarily stored.

Dioxin formation and disposal

No measurements of dioxin formation have been carried out in Denmark. The European Dioxin Inventory (section on Germany) gives air emission factors for hot-dip galvanising plants in the range of 0.007 – 0.132 ng I-TEQ/m³, whereas the content of dioxins in filter dust is in the range of 2.15-9.6 ng I-TEQ/kg /Landesumweltamt Nordrhein-Westfalen 1997/.

Based on these figures the turnover of dioxins by hot-dip galvanising in Denmark may be estimated as follows:

It is not known whether the air emission factors quoted above include emission with dust in case no cleaning of off-gases is employed. If not, the air emission may be higher than calculated. However, the figures for dioxins collected with filter dust seem to indicate that emission of dioxins with emission of dust may be insignificant.

2.3.3 Steel reclamation

Until 2002 one company in Denmark has carried out reclamation of iron and steel scrap. This production has however been closed down since early summer 2002, but has re-opened on a smaller scale in November 2002. In the future, production will focus on purchased slabs and billets. There are at the time being no plans to re-open the steelmaking plant.

It is chosen still to include steel reclamation in the report, as the production has been ongoing in most of the period from 2000 - 2002. The estimated emission is therefore a picture of the dioxin emission before the production ceased. It is not known how the emission will be for the re-opened production. The production quantity has not been updated since SFA 2000. The reason is that it has not been possible to get new information, as the factory is closed.

The production process as it has been in the main period from 2000-2002 can be described as the following:

The scrap is melted in an electric arc furnace at around 1,600 C. The raw steel bars produced will later after re-heating be processed into plates, bars and other profiles. The air passes a filter bag at about 80 C. Due to the high temperatures and the fact that the scrap received will contain residues of organic materials as well as copper dioxin formation due to "De Novo synthesis" is likely. It is generally accepted that dioxin formation depends strongly on operation conditions, such as the temperature in the flue gas cleaning system and the extent to which scrap is preheated /Det Danske Stålvalseværk A/S 2000b; Landesumweltamt Nordrhein-Westfalen 1997/.

Plant activity

Based on information from the company, the activity of the plant can be summarised as follows (1998-figures - /Det Danske Stålvalseværk 1999; Det Danske Stålvalseværk A/S 2000a/):

Of the total production waste, slag from the kiln constitutes about 47%. Slag is reused for asphalt. Other ways of recycling are iron oxide, ferrosilicium, sludge to be used in cement manufacturing etc. /Det Danske Stålvalseværk A/S 1999/. Filter dust is exported to Spain via Germany for recovery of zinc etc.

Dioxin formation and disposal

During the past two years the factory has made an effort to minimize and control the emission of dioxin and other hazardous substances from production. In January 2001 two measurements were taken from the smoke stack. The measurements showed a dioxin emission of 0.16 ng I-TEQ/Nm³ and 0.042 ng I-TEQ/Nm³, which correspond to approx. 1000 and 300 ng I-TEQ/ton manufactured steel respectively. This emission level is lower than the earlier made measurements, and if the two new measurements are considered representative of the total emission from the production, the total dioxin emission will be approximately 0.1 - 2.4 g I-TEQ/year, assuming a production of 800,000 tons/year and ± factor 3 of the two measurements.

In SFA 2000 /Hansen, 2000/ the dioxin emission from the steel reclamation production was estimated to be approximately 1.1 - 2.3 g N-TEQ/year. The amount of filter dust, which is exported, was in SFA 2000 /Hansen, 2000/ expected to be 5.0 - 10.5 g I-TEQ/year. These values are maintained in this report.

No measurements of the content of dioxins in other production residues have been undertaken. Also no measurements from other countries or other plants are available. For blast furnace slag values of 0.001-0.18 g N-TEQ/t slag has been given (Swedish data quoted in /Dyke et al 1997/). Assuming these values to be valid also to other production residues from steel reclamation in Denmark, and assuming that I-TEQ is equal to N-TEQ, the amount of dioxin deposited or used for asphalt, cement etc. may be roughly be estimated as:

It is emphasised that these estimates are very uncertain, and should only be regarded as a preliminary first assessment of the potential dioxin flow by these routes.

No information exists indicating that release of dioxin by wastewater emissions from electric arc furnaces in steel reclamation should be significant. The emission by wastewater is consequently assessed as zero. As this assessment is not supported by actual measurements, it must be regarded as uncertain.

2.3.4 Aluminium reclamation

In Denmark one company only carries out reclamation of aluminium scrap. Aluminium scrap received at the plant is melted in a salt bath composed of mainly KCl and NaCl to protect the metal from being directly exposed to the natural gas flame used for heating. The company policy is not to accept scrap significantly polluted by grease, oil, plastics or other sorts of organic materials. However, organic matter will be present in the processed materials and can hardly be avoided. As the melting point for aluminium is around 660ºC dioxin formation should be assumed likely.

Plant activity

Based on information from the company, the activity of the plant in the period 2000-2001 can be summarised as follows:

No discharge of industrial wastewater took place.

Dioxin formation and disposal

In November 2000 a high dioxin concentration was registered in the air outlet from the production. The dioxin emission was measured to be 183 ng I-TEQ/Nm³. This value considerably exceeded the limit value then in force, which was 1 ng I-TEQ/Nm³/Vejle Amt, 2000/. After this measurement two additional measurements were made, which showed 113 and 14 ng I-TEQ/Nm³. To lower the dioxin emission the company promptly established dioxin abatement. Three measurements have been carried out after dioxin abatement has been installed. These measurements have resulted in an average emission of 0.88 ng I-TEQ/Nm³ and are ranging from <0.001 ng I-TEQ/Nm³ to 2.4 ng I-TEQ/Nm³ when a 90 % confidence level is used. The latest measurement complies with the new Danish limit value of 0.1 ng I-TEQ/Nm³.

The measurements November 2000 till December 2001 correspond to emission factors within the range of approximately 0.0001 mg I-TEQ/ton product manufactured to 1.8 mg I-TEQ/ton product manufactured.

The emission at 183 ng I-TEQ/Nm³ would result in an emission of approximately 60 g I-TEQ/year, if the emission was representative of a whole year. Best estimate of the actual annual emission after dioxin abatement is 290 mg I-TEQ/year, corresponding to the range <0,001 - 792 mg I-TEQ/year when a 90 % confidence level is used. It is likely that the annual emission will be in the lower end of the interval, because the measured emission has consistently decreased considerably from measurement to measurement. It is noted that the limit value of 0.1 ng I-TEQ/Nm³ corresponds to an annual emission of 30 mg I-TEQ/year. However in this assessment the range <0.001 - 792 mg I.TEQ/year will be used.

A measurement of the dioxin concentration in the filter dust has also been made showing a dioxin concentration of 5120 ng/kg filter dust. Using the amount of filter dust from 1998 the annual amount of dioxin in filter dust can be estimated to be approximately 1 - 3 g I-TEQ/year.

In SFA 2000 /Hansen, 2000/ the dioxin emission from aluminium reclamation was estimated to be approximately 0.43 - 4.8 g I-TEQ/year, of which 0.17 - 3.3 g I-TEQ/year was dioxin emission to air.

2.4 Feedstuff

2.4.1 Fish oil and meal

There are four plants in Denmark of varying size. No production processes exceed 200ºC. However, process off-gases are burned at 850 – 1000ºC.

Two techniques for burning of off-gases are employed. One is heating in one second at 850ºC. The air passes through a ceramic filter both before and after the heating. This ensures fast cooling of the air the temperature of which is lowered to about 110ºC, when it leaves the ceramics. From here the air passes through a scrubber with seawater. In the other process the air (that either is filtered through a bag filter or through a scrubber) passes the boiler at 1000ºC, before it flows unfiltered out of the chimney at about 150ºC.

The raw materials (fish) will contain dioxin and organochlorine contaminants due to the general contamination of the marine environment. Furthermore, the possibility exists that the burning of off-gases will lead to dioxin formation by the "De Novo synthesis" or by formation from precursors.

Plant activity

Based on data from a major Danish company the activity of the fish oil and meal sector in Denmark is estimated as follows:

Dioxin formation and disposal

The dioxin emission to air from one of the Danish plants has been measured in 2001. Three measurements were made on process air after passing through a thermal combustion facility (the boiler principle). The measurements showed dioxin emissions ranging from 0.0008 to 0.003 ng I-TEQ/Nm³, equalling an annual emission of less than 15 mg I-TEQ/year. No Danish measurements from ceramic filter units are available.

The dioxin emission to air from production of fish and oil meal was in SFA 2000 /Hansen, 2000/ with high uncertainty estimated to be around zero.

Several measurements of dioxin content in products are available. According to the industry the dioxin content of the raw materials is recovered in the products, indicating no net uptake or release of dioxin. The Danish consumption of dioxins with fish oil and meal is discussed in section 2.5.4.

One plant has measured (January 2000) a dioxin concentration in the scrubber water of <0.6 pg I-TEQ/l. Assuming this figure to be applicable to the total discharge of scrubber water, the total dioxin emission to sea can be estimated at <0.01 g I-TEQ/year.

2.4.2 Meat and bone meal

There are 4 plants for production of meat and bone meal based on dead animals and other animal residues in Denmark. Information exists from one company operating 3 of these plants covering round 75% of the total production of meat and bone meal in Denmark. In 2 of the plants the production process involves a spray drying process at around 230ºC, in which the warm air is re-circulated through the heating chamber and directly exposed to the flame. Spraying is e.g. used for processing of blood-based products. The third plant, in order to minimise smell from manufacturing processes, operates a treatment unit in which offgases before emission is treated by burning at 850ºC.

The raw materials will contain dioxin due to the content of dioxin in feedstuff (reference is made to section 2.5.4). Furthermore, the possibility exists that the spray drying and the smell elimination processes will lead to dioxin formation by the " De Novo synthesis".

Plant activity

The total production of meat and bone products in Denmark can be estimated at around 408,000 tonnes per year. 307,000 tons are exported and 130,000 tonnes is imported to the country. This means that around 75% of the Danish production is assumed exported. /Danmarks Statistik, 2002a/ and

/Danmarks Statistik, 2002b/. The airflow exposed to burning before emission from the relevant plant is expected to be 620 million Nm³/year.

Dioxin formation and disposal

No measurements of dioxin emission to air exist neither from Denmark nor literature. Measurements by the companies of dioxin content in products reported concentrations varying between 19 pg I-TEQ/kg dry matter for meat residues to 1.540 pg I-TEQ/kg for the fat fraction. Meat meal manufactured without spray drying had a dioxin content of 36 - 260 pg I-TEQ/kg dry matter, whereas the dioxin content in a product from the spray drier was only 19 pg I-TEQ/kg dry matter /Andreasen 2000/. Thus, it seems unlikely that significant dioxin formation takes place by the spray drying process.

Based on the data available, it is assumed likely that air emission of dioxin related to spray drying is mainly related to burning of fossil fuels and will be covered by the estimates made in section 3.1 and 3.2. However, no data are available with respect to burning of offgases, but it is estimated that the emission per Nm³ will be nearly the same as for burning off-gases from production of fish oil and meal. On the basis of this assessment and taking the uncertainty in consideration, the annual emission is considered to be less than 10 mg I-TEQ/year.

The content of dioxin in manufactured products can, based on the figures stated above, be estimated at 0.008 – 0.63 g I-TEQ/year, of which approximately 0.006 – 0.5 g I-TEQ/year is exported.

2.4.3 Green feed drying

12 - 15 plants for green feed drying exist in Denmark. The drying process is based on warm air having a temperature of 500 - 700ºC. Most of the existing plants use a technology, by which part of the warm air is recycled via the heating chamber, where it is directly exposed to the flame. The energy source will typically be natural gas, but in a few cases the energy source is coke or fuel oil. The dry grass is typically separated from the air by a cyclone that typically is the only kind of air cleaning equipment employed /Mogensen 2000/. The grass will contain dioxin due to atmospheric deposition. However, it cannot be ruled out that the drying process in itself will lead to dioxin formation by the "De Novo synthesis".

Plant activity

Danish companies estimate the total production of dried green feed in Denmark at around 150,000 - 200,000 t/year.

Dioxin formation and disposal

No measurements of dioxin emission have been undertaken in Denmark. The European dioxin inventory (section on Germany) gives an emission factor for emission to air of 0.1 µg (min./max. 0.02 - 0.21) I-TEQ/t material (Landesumweltamt Nordrhein-Westfalen 1997). Assuming these figures to be valid also to Danish plants, the emission of dioxin to air can be estimated at 0.02 (0.004 – 0.04) g I-TEQ/year.

The European dioxin inventory gives no information of the energy source used. It should be noted that the emissions factor stated above is close to the emissions factor adopted for burning of natural gas itself (reference is made to section 3.2). This may well indicate that the source of dioxin actually is the combustion process and not dioxin from the grass or the drying process.

Measurements of grass pills and meal (11 samples) showed an average of 263 pg I-TEQ/kg product (88% dry matter) and min./max. values of 111/1097 pg I-TEQ/kg product (88% dry matter) /Plantedirektoratet 1999b/. The total amount of dioxin contained in the Danish production of grass pills and meal can thus be estimated at approx. 0.05 g I-TEQ/year.

2.4.4 Feedstuff products

The quantity of dioxins in feedstuff consumed in Denmark has been estimated in table 2.4. This estimate is mainly based on literature values for dioxin content in relevant feedstuff categories. The estimate includes intake with grass consumed by animals directly in the fields in the summer season or as silage and hay in stables during the winter season. Most of the categories listed in table 2.4 should be characterised as secondary sources or circulation of nature. This covers fish products, grass, cereals, straw and grass pills etc. Oil cakes and meal, however, is generally based on import, whereas meat and bone meal as well as milk products should be characterised as recycling within the agricultural sector.

It is emphasised that the estimates should be regarded as rough estimates aimed at indicating the relevant order of magnitude for the dioxin flows taking place. It is outside the scope of this substance flow analysis to undertake a detailed analysis of the dioxin flow within the agricultural sector in Denmark. The existing knowledge regarding deposition of dioxin in Denmark is presented in section 6.

A significant part of the estimated consumption should be expected to be recycled to farmland by manure. No exact knowledge of the amount of dioxins in question is available. As a rough estimate the quantity is here estimated at less than 10 g I-TEQ/year taking into account that feedstuff for trout farming may partly end up in the trouts produced as well as sludge being directed to landfills, whereas feedstuff for pets partly ends up in waste. No attempt has been made in this report to assess the metabolism of dioxin in domestic animals and fish. A significant part of the Danish production of trouts is exported.

Table 2.4
Consumption of dioxins with feedstuff - estimate based mainly on literature values from Europe.

2.5 Food products

Similar to feedstuff food products will contain dioxins mainly due to the content of dioxins in raw materials. No manufacturing processes should be suspected to develop dioxins, as the process temperatures involved seldom will exceed 200° C. The experience available for spray drying processes (reference is made to section 2.4.2) does not give evidence for regarding spray drying as a dioxin generating process.

A measurement from a Danish fish processing factory shows a dioxin emission of 0.001 ng I-TEQ/Nm³ in the air flow or approximately 0.1 - 1 mg I-TEQ/year from the plant in question. This corresponds to an emission factor of approximately 16 ng I-TEQ/ton fish processed.The air flow comes from the process, where the skin is removed from the fish and from cooking. The dioxin content in the air flow must relate to the natural dioxin in the fish, as no combustion is taking place during these processes. If the dioxin emission is compared to the dioxin content in one ton fish, the dioxin emission per ton fish processed is approximately 0.2 % of the dioxin content in one ton fish.

The quantity of dioxins in food products consumed in Denmark has been estimated in table 2.6. This estimate is mainly based on literature values for dioxin content in relevant food product groups. It is emphasised that the estimates should be regarded as rough estimates aimed at indicating the relevant order of magnitude for the dioxin flows taking place. It is outside the scope of this substance flow analysis to undertake a detailed analysis of the human intake of dioxins in Denmark, and the figures presented in table 2.6 are not aimed at that kind of discussion.

It is noted, that the estimate of 0.26 g I-TEQ/year (min./max. values of 0.06 – 0.44 with food products presented in table 2.6 is in good agreement with the most recent estimate of human intake of 1.5 pg WHO-TEQ/kg body weight per day in Denmark developed by the Ministry for Agriculture, Food Products and fishery /Fødevaredirektoratet & Plantedirektoratet 1999/. Assuming a total Danish population of 5.2 million citizens and an average body weight of 70 kg, the estimate of 1.5 pg WHO-TEQ/kg body weight per day corresponds to a total human dioxin intake of 0.2 g WHO-TEQ/year.

All of the product groups listed in table 2.6 should be characterised as secondary sources or circulation of nature. It has not been tried to estimate the exchanges taking place to and from other countries by import and export of food products.

A significant part of the estimated consumption should be expected to end up in sewage. A part will also end up as domestic waste and be disposed of either by waste incineration or by biological waste treatment.

Table 2.6
Consumption of dioxins with food products - estimate based mainly on literature values from Europe.

2.6 Pentachlorophenol

Pentachlorophenol and its derivatives are generally accepted as precursors for dioxin and will naturally contain traces of dioxin developed during the formation process of pentochlorophenol. The main derivatives of commercial interest are sodium pentachlorophenolate and pentachlorophenyl laurate. In this section the abbreviation PCP is used for pentachlorophenol as well as its main derivates.

The dioxin content of PCP depends on the formation process and primarily consists of octa-, hepta- and hexachlorinated compounds. Based on data available in /WHO 1987/ and /Christmann et al. 1989 quoted in Jensen 1995/, the dioxin content in technical PCP commercially available in the seventies and the beginning of the eighties may be roughly estimated at 0.16 – 7 mg I-TEQ/kg PCP.

It should be recognised that these figures may well be discussed with respect to whether they are representative. Analyses of samples of technical PCP commercially available in Denmark in the seventies (described in /Danish EPA 1977/) indicate that the content of dioxin in PCP used in Denmark should be in the low end of the range 0.16 – 7 mg I-TEQ/kg PCP. On the other hand the investigations of /Christmann et al. 1989 quoted in Jensen 1995/ show an average of commercial wood preservation solutions of approx. 20 mg I-TEQ/kg PCP. Other examples of high concentrations of dioxins in wood preservation solutions have also been reported /Dobbs & Grant 1981 quoted in Jensen 1995/.

Based on /Eduljee 1999/ it can be estimated that restrictions imposed by USEPA in 1987 and EU in 1991 on the content of dioxins in PCP have reduced the dioxin content to 0.11 - 4.2 mg I-TEQ/kg PCP.

PCP has been used widely for preservation and conservation purposes. Important fields of application have been and are wood preservation, leather tanning and preservation of textiles etc. The following assessment is limited to these applications, as no other applications are likely to be important in this context.

PCP has not been manufactured in Denmark, and consumption in Denmark has been based on import of chemical products and goods treated with PCP. In Denmark, restrictions on the content of dioxins in PCP was introduced in 1977 / Bylaw 582-1977/. This restriction actually functioned as a ban eliminating by and large all intended use and consumption of PCP in Denmark except for laboratory purposes and other special uses able to obtain dispensation for the general restriction. This restriction was followed by a ban in 1996 on sale of chemical substances and products containing 0.1% PCP or higher concentrations and a ban on sale, import, export and use of goods containing 5 ppm PCP or higher concentrations /Bylaw 420-1996/. As an exception, countries with ocean coast (France, Ireland, Portugal, Spain and the United Kingdom) can choose to use products with more than 0.1% PCP until the end of year 2008. This exception can only be used in industrial plants for treatment of wood (for outdoor) and waterproofing of fibres and heavy textiles. The total content of HCDD in PCP must however not exceed 2 ppm in preparations used for this purpose./European Commission, 1999/

An issue essential to assessing the fate of dioxins present in products due to the use of PCP is the extent to which dioxins are likely to evaporate or otherwise migrate out of the products in question. However, no investigations addressing this issue have been found. Estimates of the relevant order of magnitude for these processes may in lack of better documentation be based on analogy considerations to PCBs used as plasticizer in joint foam for construction purposes etc. For such uses it has been estimated that 10 - 20% of the original PCB content would evaporate during the useful life of the product depending on the actual product and use etc. /Nisbeth & Sarofim 1972 quoted in COWIconsult 1983/. For products with lives in the range of 20 - 40 years, these rates of evaporation will correspond to a yearly evaporation rate of approx. 0.5% of the original content of PCB in the products.

It is noted, that /Bremmer et al 1994/ based on considerations on the physicochemical characteristics of dioxins has estimated a half-life of dioxin in wood of 150 years corresponding to an average yearly evaporation of 0.33% of the original content 0.45% calculated over the quantity that remains in the wood. This estimate is based on the assessments that the half-life for PCP in wood is 15 years and that the evaporation of dioxins from wood, on average, is 10 times slower than for PCP /Bremmer et al 1994/.

Leaching of dioxins from PCP-treated poles is considered a potentially significant route for exposure in the US /Greenpeace 2000/. However, leaching from poles and other products should not be considered an issue in Denmark, as the use of PCP for many years has been banned. PCP has, furthermore, never been an important substance for treatment of wood in contact with soil, as either creosote or As-Cr-Cu compounds always have dominated this market in Denmark.

2.6.1 PCP in wood

To what extent PCP-preserved wood is still in use in Denmark there is no precise knowledge. Assuming an average life of PCP-preserved wood of around 20 years, a minimum of 10 years, a maximum of 40 years and a linearly development, the amount of wood still in use by year 2000 in Denmark should equal a PCP quantity of approx. 680 tons. Assuming the dioxin content of the PCP used in this period to be in the range of 0.16 – 7 mg I-TEQ/kg PCP, 680 tons of PCP should equal an amount of dioxin of 110 – 4800 g I-TEQ.

By now most of PCP in preserved wood still in use in Denmark would probably be evaporated /Borsholt 2000/. No precise knowledge exists as to what extent all the dioxin has evaporated as well. Assuming an evaporation of 10% of the original content over a period of 20 years (reference is made to the introduction of section 2.6) would mean that the amount of dioxin still present in wood should be in the range of 85% of the original content equalling 90 – 4100 g I-TEQ. The yearly emission would - parallel to this - be around 0.5 % of the original content per year. This emission rate should equal an actual emission to air in Denmark of 0.5 - 20 g I-TEQ/year.

Furthermore, dioxins will probably be present in wood directed to waste incineration in Denmark. As a rough estimate one should assume a figure in the range of 5 - 200 g I-TEQ/year, meaning that the stock of PCP-preserved wood remaining in the Danish society would be completely disposed of within the next 20 years.

It is emphasised that several of the assumptions stated above may be discussed, and that the results should only be considered as an indication of the relevant order of magnitude for the dioxin flows in question.

Current import of wood preserved by PCP

The European consumption of PCP (sodium-PCP) in 1996 has been estimated at 380 tons used dominantly in France, Portugal and Spain for anti-sap-stain control of wood used for construction and single-use pallets for transport purposes /ERM 1998/. The use of PCP for preservation of wood (and likely also anti-sap-stain control) is widespread in the US and is also used in Asian countries like Malaysia for wood types as nyatoh /ERM 1998; Henriksen 2000; Wilkinson 2000/. No information is available regarding the situation in Russia and Eastern Europe.

The import of PCP with anti-sap-stain treated wood to Denmark was for 1983 estimated at 5 - 25 tons /COWIconsult 1985/. This estimate referred to a situation, when PCP was still used for anti-sap-stain control in Finland, being traditionally a very large exporter of wood to Denmark.

Today import of PCP treated wood to Denmark is banned /Bylaw 420-1996/, and the use of PCP has for long been stopped in all the Nordic countries. The amount of wood imported to Denmark and potentially treated with PCP will not exceed 100,000 m³ corresponding to approx. 20% of the amount assumed potentially treated in 1983 /Danmarks Statistik 1999a; COWIconsult 1985/. As the direct import of wood to Denmark from countries like France, Portugal, Spain, Malaysia, the US and Canada is relatively small. The countries of concern should rather be Russia, Poland, Estonia, Latvia and Lithuania /Danmarks Statistik 1999a/. However, no precise knowledge with respect to the use of pentachlorophenol in these countries is available.

It follows from these considerations, that the import of PCP with PCP treated wood today should be expected to be in the range of 1 - 10 tons PCP yearly. This estimate inter alia takes into account that part of the PCP used for single-use pallets in the rest of Europe also will enter Denmark with miscellaneous goods imported.

The content of dioxins in the PCP used will have changed during this period (reference is made to the beginning of section 2.6). Assuming a content of 0.11 - 4.2 I-TEQ/kg PCP as for the period after 1987/1991, the import of 5 - 25 tons PCP in 1983 should equal a dioxin import of 0.6 - 105 g I-TEQ/year. Similarly should an import of 1 - 10 tons PCP in 2000 equal an import of 0.11 - 42 g I-TEQ/year.

As no detailed assessment of the flow of wood and wood products in Denmark is available, the following considerations concerning the fate of the imported dioxin must be limited to a primarily qualitative assessment.

Single-use pallets imported to Denmark must be assumed dominantly to be burned shortly after the import, although a minor part may be reused for other purposes (e.g. construction of playhouses etc.) delaying its final disposal for a couple of years. It should be considered a source of dioxin to municipal incineration plants as well as to private and industrial wood stoves. For ordinary citizens they will appear untreated thereby not calling for attention when used in a wood stove for heating purposes. As a rough estimate 0.5 - 5 tons of PCP corresponding to 0.05 - 21 g I-TEQ is assumed to follow this route.

Other types of wood must be assumed mainly to be used for construction purposes thereby given a useful life in the range of 5 - 100 years depending on the actual use. For assessment purposes an average life of 20 years is assumed in the following. Again 0.5 - 5 tons of PCP corresponding to 0.05 - 21 g I-TEQ is assumed to follow this route.

Considering that anti-sap-stain treatment of wood is done on reasonably fresh wood and typically affects the top 1.5 mm of the wood, it seems logical to assume, that the dominant fate for the content of PCP would be emission to air by evaporation. Again, the fate of dioxins may best be predicted by assuming, that only 10% of the original content will evaporate during 20 years corresponding to an emission rate of 0.5% of the original content per year.

Assuming that the import of PCP and dioxin caused by anti-sap-stain treatment of wood has developed linearly over the years, the current dioxin emission to air may be estimated as follows:

10%((0.5+0.05)/2 – (105+21)/2 g I-TEQ/year) = 0.03 – 6 g I-TEQ/year

Considering only imports after 1980, the amount of dioxin contained in construction wood currently directed to waste incineration may be roughly estimated at 0.1 - 42 g I-TEQ/year and the present stock of dioxins in wood to somewhat in the range of 4 - 840 g I-TEQ. Again, the possibility, that part of the wood will be combusted in private and industrial wood stoves, cannot be ruled out.

It is emphasised that the above calculations are extremely uncertain and should only be considered as an indication of the relevant order of magnitude for the dioxin flows in question.

Summary on PCP-treated wood

The estimates developed for the turnover of dioxins by preserved wood in Denmark is summarised in table 2.7.

It is noted that part of the estimated emission to air could be carried away by rainwater falling on the surface of the wood and thus be carried away as storm water. The amount in question should be expected to be included in the estimated contribution from atmospheric deposition to wastewater and storm water in Denmark (reference is made to table 5.5 in section 5.7.1).

Table 2.7
Estimated turnover of dioxins by PCP-preserved wood in Denmark

2.6.2 PCP in leather

Conservation of leather with PCP ceased in Denmark by the end of 1985 (COWIconsult, 1985). The current regulation in Denmark as well as the rest of EU does not permit import, sale and use of goods containing ³ 5 ppm PCP.

Of 26 leather samples bought and analysed in Germany in the period 1994 - 96 6 samples exceeded the emission limit value of 5 ppm, whereas the average for all samples was 7 mg PCP and around 50 ng I-TEQ per kg leather /Klasmeier & McLachlan 1999/. The dominant source for dioxin in all samples seemed to be PCP. However, for a few samples the congener pattern indicated other sources as well. The trend for use of PCP for leather conservation seems to be decreasing, and today likely not more than 5% of all samples would exceed the 5 ppm limit (Klasmeier 2000). It should be noted that PCP preservation of leather in order to be effective must allow for a content of at least 50 ppm (Frendrup 2000).

Import of tanned leather to Denmark comes up to around 10,000 tons per year /Danmarks Statistik 1999a/. Assuming an average dioxin content of 50 ng I-TEQ/kg leather, this import equals an import of dioxin of approx. 0.5 g I-TEQ/year.

The fate of the imported dioxin will vary with the products in question. Due to a relatively small quantity, no effort has been invested in detailed investigations of the circulation of the imported leather, and the following description is limited to a primarily qualitative assessment.

Roughly 50 – 70% of the import covers items like footwear, gloves and bags with a relatively short lifetime. For such items one should expect the major part of the dioxin content still to be present in the items at the time of disposal which in Denmark today means waste incineration.

The remainder of the import covers mainly leather in bulk likely to be used inter alia for furniture and coats with a life of perhaps 10 - 20 years. For these items evaporation may take place, emitting dioxins to indoor as well as outdoor air. Again assuming that 10% of the original content will evaporate during the useful lifetime, the yearly emission to air can be estimated at less than 0.05 g I-TEQ/year, which in this context should be considered insignificant. The dominant route of disposal will again be waste incineration.

2.6.3 PCP in textiles

The main uses of PCP related to textiles seem to be:

Preservation of so-called "Heavy duty textiles", like tents and tarpaulins for outdoor purposes.

Preservation of cotton and textiles made of cotton for storage and sea transport.

Conservation of fluids used for sizing of textiles.

To the best of knowledge PCP is not used for any of these purposes in Denmark today.

However, in the eighties PCP was widely used in Denmark for preservation of cotton textiles for outdoor purposes. The amount of PCP applied was typically 5 - 15 g PCP/kg textile and the total consumption of PCP in Denmark for this purpose was estimated at 2.5 - 9 t/year (COWIconsult 1985). Today in Europe PCP is used for this purpose only in the UK and mainly for military equipment /O’Neil 2000/ but to some extent also for tarpaulins, tents and similar public applications /Thomas 2000/. The consumption of PCP for this purpose in the UK in 1996 was 28 tons /ERM 1998/. Considering the limited consumption and the Danish ban on import of such materials, any import to Denmark of dioxins in this context is deemed insignificant.

Preservation of cotton and cotton textiles in the Far East may be done simply by spraying PCP into the closed containers in which the textile balls are stored and transported /Kemi 1997/. This way of applying PCP will naturally result in high variations in the content of PCP and dioxin to be observed in finished textile products.

A Danish investigation of dioxin and PCP content in cotton T-shirts (24 samples) showed an average of 0.35 ng N-TEQ/kg with a min.-max. range of 0.02 - 2.6 ng N-TEQ/kg textile. However, no correlation between dioxin and PCP content in the textiles was found /Vikelsøe & Johansen 1996/. German investigations (131-samples) on textiles of various materials indicate an average around 2 ng I-TEQ/kg and a min.-max. range of ~0 – 82 ng I-TEQ/kg /Klasmeier & McLachlan 1997/. In the German investigation the highest values were found in cotton textiles. As the average is highly influenced by few samples with a high level of contamination, the German study in this context is deemed the most reliable, although the Danish study may be more represenative to Danish textiles. It should be noted, that the dioxin content observed may be caused not only by the use of PCP, but could also be influenced by other sources like chlorine bleaching and dyestuffs based on chlorinated compounds like chloroanilins.

In 1998 the total import of textile products to Denmark came up to approx. 260.000 tons. An average content of dioxin of 2 ng I-TEQ/kg would equal a dioxin import of approx. 0.5 g I-TEQ/year.

2.7 Use of chlorine for bleaching and disinfecting

2.7.1 Use in Denmark

Apart from the industrial uses of chlorine mentioned in section 2.1, chlorine and chlorinated products are widely used for bleaching and disinfecting purposes in Denmark. Bleaching operations in Denmark includes paper manufacturing, textile manufacturing and laundry, whereas disinfecting is related to water supply, cooling water, wastewater, swimming pools and several industrial processes, in particular within the food industry.

Whereas dioxin formation has been well documented with respect to the use of chlorine in the paper industry, almost no data are available for other processes involving the use of chlorine and chlorinated compounds like bleaching and disinfecting agents.

One investigation only is known to deal with dioxin formation in drinking water. Adding 0.3 g Cl₂/l to drinking water developed a dioxin amount equal to 37 pg I-TEQ/l /Rappe 89 quoted in Jensen 95/. Adding the same amount of chlorine to two times distillated water developed 8 pg I-TEQ/l, meaning that some dioxin or precursors must have been present in the gas itself.

A Russian investigation of dioxin formation by chlorination of purified wastewater from biological wastewater treatment by sodium hypochlorite reported no difference in the content of dioxins before and after chlorination /Khizbullin et al 1999/.

The consumption of chlorine and chlorinated products for bleaching and disinfecting is known with some uncertainty. Based on /Danish EPA 1989; COWI & CETOX 2000/ the consumption can be estimated as follows:

Chlorine gas is assumed primarily to be used for bleaching of textiles and to some extent also for disinfecting of raw surface water to be used as drinking water and disinfecting of swimming pools whereas sodium hypochlorite is the main agent for cleaning and disinfecting purposes.

It should be noted, that bleaching in the paper industry in Denmark today is mainly done by hydrogen peroxide and to a lesser extent by sodium hypochlorite, and no measurements of dioxin content in wastewater and sludge from the manufacturing process are available /Dalum 2000/.

2.7.2 Bleached products (cork and paper)

This section is focused on cork and paper/carton products as textiles are assumed to be covered by the assessment made in section 3.6.3.

Cork

Cork may be bleached as well as treated with PCP. A German study /Fromberger 1991 quoted in Fiedler 1999 – no further reference/ showed a dioxin content in cork for sealing of wine bottles of 0.18 - 0.26 ng BGA-TEQ/kg and 12.6 ng BGA-TEQ/kg in cork-based wall covering. In case of cork sealings the congener pattern indicated bleaching as the source, whereas the congener pattern indicated use of PCP as the source with respect to the wall covering.

The quantity of cork sealings imported to Denmark comes up to approx. 350 tons/year, whereas import of other cork items apart from natural cork and waste comes up to around 800 tons/year /Danmarks Statistik 1999/.

Assuming that BGA-TEQ is equal to I-TEQ, the worst case import to Denmark of dioxins with cork may be calculated to approx. 0.01 g I-TEQ/year. The real import shall here be estimated as <0.01 I-TEQ/year. The content of dioxin should be assumed to be disposed of to waste incineration sooner or later. Although a minor emission of dioxin to air may be expected to take place from cork used as floor or wall coverings etc, this emission are probably insignificant.

Paper/cardboard

Dioxin developed by chlorine bleaching will partly be adsorbed to the paper manufactured. Furthermore, it should be expected that dioxin once formed and attached to paper fibres to some extent might remain attached also during recycling operations. Dioxins in paper may thus continue to circulate in the society for several years depending on the life of individual paper products. To this should be added that internationally PCP has also been used as a pesticide in paper manufacturing, and PCP is actually registered in paper products in concentrations op to 0.7 ppm /Maff 1997/.

No investigations of the content of dioxin in paper products have been carried out in Denmark. A German study /FLV 1993 quoted in Fiedler 1999/ investigated virgin paper as well as recycled materials. In virgin newspaper the dioxin content was generally around 1 ng I-TEQ/kg or below. In secondary paper materials dioxin content of 0.8 - 3.2 was found whereas in cardboard materials and wrapping paper a content of 4.5 – 11.5 was registered.

Based on these findings a rough dioxin balance for Denmark with respect to paper and cardboard materials have been established in table 2.8.

The balance should be regarded as an attempt to illustrate the relevant order of magnitude for a number of relevant dioxin flows related to paper and cardboard materials. The size of the flows indicates that some emissions to water or loss to paper sludge and other residues from paper recycling in Denmark could well take place. However, no data is available to confirm or de-confirm this hypothesis. As paper sludge in Denmark generally are re-utilised for cement manufacturing; the dioxin directed this way should be expected to be destroyed due to high temperatures of cement manufacturing.

Of the total supply of paper and cardboard in Denmark, around 50% is presently collected for recycling, whereas the rest is directed for waste incineration /Papirstatistik 1998/. Thus one would expect around 1.5 - 3.3 g I-TEQ/year to be directed for recycling and a similar quantity to waste incineration.

Table 2.8
Dioxin balance for paper and cardboard materials

2.8 Other industrial processes

A number of other industrial processes that may be suspected to develop dioxins exist in Denmark. The available knowledge related to these processes is presented in the following. The list of processes is not necessarily exhaustive.

Vitamin manufacturing

Vitamin manufacturing is one of the major uses of chlorine in Denmark. The manufacturing process, however, is going to be changed to a chlorine-free process by the end of 2001. No measurements for dioxins have been carried out, as the manufacturing process is not believed to generate dioxins. This assessment is based on the facts that the chlorine before being in the manufacturing process is transformed into hypochlorite, and the temperatures used in the process do not exceed 67ºC. It is thus deemed unlikely that the process will develop or cause emission of dioxins to any significant extent.

Spray drying and roasting processes

Spray drying is used in a number of manufacturing processes and in particular within the food industry on products like coffee, milk powder etc. No measurements for dioxin emission related to such industries have been carried out in Denmark. No data are to the best of knowledge available from the literature either. Spray drying processes generally takes at above 200ºC, typically by hot air recirculated through a flame fed by natural gas. The experience from spray drying of meat and bone meal (reference is made to section 3.4.2) indicates however that it is unlikely that spray drying in general will generate dioxin to any significant extent. Whether this assessment also applies to roasting processes like roasting of coffee beans etc. cannot be said. Although one would expect the formation and emission to be small, no measurements are available.

Asphalt preparation and recycling

Asphalt preparation and recycling is assumed to be a potential source of dioxin, in particular in countries doing extensive recycling and using ordinary salt (chloride) for preventing icy roads during the wintertime.

The total production of asphalt for road construction and other purposes in Denmark in 2001 came up to approx. 2,700,000 tons /Danmarks Statistik 2002b/, of which approx. 870,000 tons are reused or recycled materials (the estimated number for 2000) /Dall et al., 2002/.

Measurements from 1999 of the dioxin emission to air from a Danish asphalt mixing plant (virgin asphalt) gave an emission factor of 2.2 ng I-TEQ/tonnes product /Fyns Amt 2000/.

No measurements of the emission from recycling plants from Denmark exist. From Dutch investigations an emission factor for recycling plants of 47 ng I-TEQ/tonnes of asphalt is reported. The Dutch figure is, however, likely to be an overestimate compared to Danish plants, as most Danish plants are using the so-called "cold recycling" in which only stones are heated and then mixed with the rest of the components (not preheated), whereas the Dutch plant were heating all the components.

Anyway, accepting the given figures as representing the relevant range (the high figure is only used for recycled materials), dioxin emission to air from asphalt plants in Denmark can be roughly estimated at less than 41 mg I-TEQ/year.

In SFA 2000 /Hansen, 2000/ the dioxin formation from production of other industrial materials was with some uncertainty estimated to be less than 0.04 g I-TEQ/year.

Coal tar production

According to /Danmarks Statistik 2002b/ the production of coal tar in Denmark is approximately 79,000 tons per year.

In connection with the production of coal tar an incinerator is used for quenching the noncondensible gasses from the coal tar distillation plant. This process was assumed to be a potential source for dioxin and a measurement was therefore made in 1999. The measurement of dioxin to air gave an emission factor of 0.21 ng I-TEQ/tonnes products /Fyns Amt 2000/.

No international measurements have been found for production of coal tar, but on the basis of the Danish measurement the annual emission from production of coal tar is estimated to be within the range of 0.008 mg I-TEQ/year to 0.03 mg I-TEQ/year.

Flaring

By initiation of crude oil extraction from new production wells the operators will often need to burn off (flare) the natural gas present in the oil. In order to emission from the flaring operation seawater is added. Whereas minimise NO_x natural gas in itself by burning generates dioxin in small quantities (reference is made to section 3.2), adding of seawater could make an increased dioxin emission likely. However, no measurements are to the best of knowledge available, and it is not possible to give any estimate of the emission. The source is relevant to Denmark due to the Danish oil extraction activities in the North Sea.

Oil refining

There are two oil refineries in Denmark, both of which use catalysts in the refining process. The catalysts are made of platinum on a base of aluminium oxide. The catalysts require hydrogen chloride on the surface for its operation that is obtained by adding tetrachloroethene under normal operation of the catalyst. Under normal operation the catalyst is covered by water, and formation of dioxins should not be possible. Gasses are passed through a desulphurizing installation, before it is burned off in the boiler, from where it goes out unfiltered. Whether dioxins are generated during the final burning operation is not known.

During production the platinum catalyst achieves a layer of coke. During regeneration of the catalyst the plant is closed for several days. The coke is burnt off whereas organic chlorine compounds are added. The air from this process is neutralised with NaOH in water before it goes out unfiltered. Dioxin formation by similar processes has been confirmed by investigations Canada /Jensen 1995/. Based on information from the refineries, the amount of coke burned this way can be estimated at approx. 26 tonnes/year. However, no measurements of dioxin emission have been undertaken, and no data is available to allow an estimate of the emission.

2.9 Summary

The assessments and estimates related to formation and turnover of dioxins by industrial activities in Denmark by the end of nineties and presented in sections 2.1 to 2.8 are summarised in table 2.9.

Table 2.9
Summary of formation and turnover of dioxins by industrial activities in Denmark