| Front page | | Contents | | Previous | | Next |

Mass Flow Analysis of Chromium and Chromium Compounds

3 Use of chromium compounds in Denmark

3.1 Introduction to chromium compounds

Chromium is used in many contexts within the chemical industry. For example, chromium compounds are used for surface treatment in order to prevent corrosion, to improve product durability, in tanning and to manufacture pigments. According to the information available in the Product Register, the chemical industry uses approximately 130 different chromium compounds to manufacture a wide range of products (the Product Register, 2001). As there is no central source of information on consumption of individual chromium compounds, it has not been possible to determine the exact quantities of chromium used within the chemical industry and other industries. For example, the Danish confederation of chemical industries, which numbers 47 members, has no central information about its members' products. Nor does it possess information on the use of chemicals containing chromium among its members.

Table 3.1 shows an overview of the information available from Statistics Denmark on the total import, export, production and supply of chemicals containing chromium during the period 1998–2000.

Table 3.1
Import, export, production and supply of chemicals containing chromium, 1998–2000 (Statistics Denmark, 2001b)

¹ Calculated in Table 3.3

When we compare the information available from Statistics Denmark about the supply of oxides and hydroxides of chromium with the information in the Product Register about the expected maximum import, export and production (i.e. supply), we arrive at an indication of the relative shares accounted for by individual substances. See Table 3.2 below.

Table 3.2
Expected relative shares accounted for by oxides and hydroxides of chromium (%)

Table 3.2 shows that the group consists almost entirely of chromium oxides. It has been assumed that the contributions to the mass balance made by the individual substances can be established by multiplying the supply by the expected percentage indicated above, and then multiplying this figure by the share of the molar weight accounted for by chromium in the relevant substance. See Table 3.3.

Table 3.3
Chromium quantities

The information on surface treatment presented in this section is based on Dahl & Løkkegaard (2000) and Dahl (2002).

Chemical chromium compounds are widely used for metallic surface treatment. Most processes involve the use of Cr(VI) in the form of chromium acid (H₂CrO₄), but in a few cases, chromium may also be added in the form of sodium dichromate. The most common processes are:

1. Chromium plating (typically a 0.25 µm layer of chromium on top of nickel. Also known as decorative chromium plating)
2. Hard chromium plating (a 10–700 µm layer of chromium applied directly on top of steel)
3. Black chromium plating (a 0.1–2.0 µm layer of black chromium applied on top of a layer of nickel)
4. Chromating of zinc surfaces (also known as passivation)
5. Chromating of aluminium (usually as preparation for powder lacquering, possibly finishing)
6. Chromic acid pickling of aluminium
7. Chromic acid pickling of plastic
8. Anodising of aluminium (in strong chromium(VI) oxide)
9. Chromium passivation after phosphatising
10. Miscellaneous processes

A total inventory of chromium consumption, utilisation and waste is shown in Table 3.4.

Table 3.4
Chromium consumption and waste associated with surface treatment in Denmark

With decorative chromium plating, a thin layer of chromium (approximately 0.25 µm) is added onto a layer of nickel (10–15 µm) by means of electrolysis. The process takes place in a solution of CrO₃ (200 g/l) with H₂SO₄ (4 g/l) and small amounts of catalyst. The drag-out of bath chemicals is large compared to the consumption, but most companies have become good at collecting the drag-out in one or more still rinse tanks which can be used to replenish the bath, replacing what is lost due to evaporation from the 35–40°C bath. Without any recovery, the utilisation of CrO₃ would be as low as 2–5%, whereas recovery typically leads to recovery rates of 20–98% depending on the recovery system used.

It is estimated that a total of 75 companies in Denmark carry out decorative chromium plating (nickel plating + chromium plating), and approximately 80% of all nickel-plated surfaces will also be finished by means of chromium plating. If we assume that approximately 125 tonnes of nickel anode is used each year in Denmark, this means that a total surface of 1,170,000 m² is coated by a layer of 12 µm nickel. If we take 80% of this figure, we arrive at a total surface of 936,000 m² which is chromium plated after first being nickel plated. If we assume that the average layer of chromium applied is 0.25 µm, this corresponds to a theoretical consumption of CrO₃ of 3,105 kg. Two companies alone represent almost 45% of all the surface treatment carried out, consuming almost 6 tonnes of chromic acid. Both of these companies use disproportionate amounts of chromium(VI) oxide: theoretically, their consumption should be 1,124 kg, but in actual fact they consume 5,750 kg. The main reason for this is a very low recovery rate for chromium(VI) oxide, particularly at one of the two companies.

If we assume that the average recovery rate for the other manufacturers – which account for the remaining 55% of all production in Denmark – is 40%, the total consumption of chromium(VI)oxide can be estimated to be approximately 10,000 kg/year.

We can theoretically say that out of 10,000 kg chromium(VI) oxide, approximately 3,105 kg (= 1,615 kg Cr) end up on the actual goods. The rest ends up in wastewater or at Kommunekemi as discarded baths or semi-concentrates. We estimate that 25% ends up with Kommunekemi, whereas the rest ends up in the companies' treatment plants. Here, most of the chromium(VI) oxide is deposited to form filter cakes. These filter cakes are sent to Kommunekemi or for reprocessing abroad. A small part is discharged into the sewer system with wastewater. Today, such discharges of wastewater will typically feature chromium concentrations of 0.2 mg/l. The 936,000 m² treated surface mentioned above will probably correspond to wastewater quantities of 50,000 m³ (at a water consumption rate of 50 l/m²). We can then say that 50,000 m³ wastewater containing 0.2 mg/l corresponds to 10 kg of chromium per year. This is to say that 10 kg of chromium is discharged into Danish sewers every year.

In principle, chromium baths can last forever. However, baths will be discarded from time to time because of contamination (typically due to excessive contents of alien metals). Even so, it is unlikely that more than 10 m³ baths are discarded each year. With chromium(VI) oxide contents of 200 g/l, this corresponds to 2,000 kg/year.

3.2.2 Hard chromium plating

Hard chromium plating means that a thick layer of chromium (from 10 to 700 µm) is added directly onto steel by means of electrolysis. This process takes between ½ and 24 hours. The bath typically consists of CrO₃ (300 g/l) and H₂SO₄ (3 g/l), and the bath temperature is typically 55°C. Due to very considerable evaporation losses and low drag-out with the goods (due to long retention times), the goods will often be rinsed with a little deionised water directly above the bath. The goods and tools will then subsequently be rinsed in still rinse tanks. As a result, the drag-out of chromium(VI) oxide to rinsing water and treatment plants is very low, and the quantities of water used for rinsing are similarly low.

Approximately eight Danish companies carry out hard chromium plating, and three of these account for approximately 70% of the total production. Based on interviews with these three companies, the total chromium consumption, etc., associated with hard chromium plating can be estimated for all of Denmark. These estimates are shown in Table 3.5.

Table 3.5
Chromium consumption and chromium waste associated with hard chromium plating in Denmark

3.2.3 Black chromium plating

Black chromium plating means that a layer of black chromium (0.1–2.0 µm) is added onto a layer of nickel by means of electrolysis. Approximately five Danish companies carry out black chromium plating. Just one of these companies uses 85% of all the chromium(VI) oxide used for this process in Denmark, and accounts for 91% of the total surfaces treated in this manner. The chromium bath contains CrO₃ (340–375 g/l) and small amounts of catalyst.

At the main manufacturer described above, substantial amounts of the chromium baths (approximately 90% of the total consumption of chromic acid) are discarded due to contamination. The losses are less substantial among the other companies and are primarily caused by drag-out with the goods. As the bath temperature is low (18–20°C), not much chemical can be returned from the interim rinsing phase. This means that the rinsing water must be taken to Kommunekemi when the concentrations become too high. Table 3.6 provides an overview of chromium consumption and chromium waste associated with black chromium plating in Denmark.

Table 3.5
Chromium consumption and chromium waste associated with black chromium plating in Denmark

3.2.4 Blue passivation of zinc

Chromating (also known as passivation) of zinc surfaces takes place in a weak solution of chromate. Here, a chemical reaction occurs between metallic zinc and chromate. The layer of chromate formed as a result of this reaction contains zinc and Cr(III) and Cr(VI). The chromated goods are considerably more resistant to corrosion than the untreated zinc surface. Today, blue chromating can be done exclusively on the basis of Cr(III) salts. As a result, the process ought to be known as blue passivation. During use, the bath will be contaminated by Cr(III), zinc and ions from the basic material. When this contamination becomes too great, the entire bath is discarded. Discarded baths are usually treated at the companies' own treatment plants.

A total of approximately 600 tonnes of zinc anode is used each year in Denmark. This figure is based on a study from 1996 (Dahl & Løkkegaard, 2000), supplemented by recent inquiries made to some of the largest manufacturers. All electrically zinced goods are chromated, as this final treatment provides better corrosion properties. The goods are treated as items plated in barrels (small items) with layers of 3–10 µm (7 µm on average) and as items plated on racks with layers of 10–20 µm (12 µm on average).

In 1996, most companies still used chromate for blue chromating. Today, more than 95% use a Cr(III) salt, most frequently chromium(III) nitrate, but chromium(III) sulphate or chloride may also be used. As a result, the phrase "blue chromating" is actually inaccurate today. Instead, the process should be known as blue passivation, as no chromates are involved in the process. The baths used for blue passivation contain slightly more chromium than the blue chromate baths used in the past, but the new baths last a lot longer (by a factor of 5). This is a significant improvement in environmental terms, as baths are now discarded much less frequently than before.

Olive and black chromating are treated as one in these calculations, but in actual fact, black chromating is much more widespread than olive chromating. The two processes share very similar process chemistry. Black chromating has become more common in Denmark during the period from 1996 up until today.

The rinsing water is treated directly by means of reduction and precipitation, or it may be concentrated first by means of an ion exchange process. The sludge from the treatment plant is either sent to Kommunekemi or for treatment abroad. The discarded process baths are usually also treated at the companies' own treatment plants, as their metal content is relatively low. Discarded chromating baths for black and olive chromating may also be sent to Kommunekemi for treatment.

Table 3.7 shows estimated, detailed process data for the four types of passivation of zinc.

Table 3.7
Chromium consumption and chromium waste associated with chromium surface treatment on zinc in Denmark.

3.2.5 Chromium treatment of aluminium

This process is very much like the corresponding process for zinc surfaces. It is a chemical process where the aluminium surface reacts with chromium(VI) oxide while forming a layer which contains both Cr(III) and Cr(VI) compounds with aluminium. The layer may also contain phosphate and fluoride depending on the type of chromating chemicals used.

Table 3.8 shows an overview of typical bath compositions.

Table 3.8
Bath compositions for chromating aluminium

The process is carried out at room temperature.

With suitable drag-out with the goods, it is often possible to avoid discarding the bath itself. This is because the drag-out, possibly supplemented by tapping in connection with the addition of new chemicals, removes enough of the bath to avoid accumulation of aluminium and chromium(III) in the bath.

Table 3.9 presents figures from the three largest companies within the industry, accounting for at least 80% of the profile production, as well as from the largest supplier of chemicals.

Table 3.9
Chromium consumption and other parameters for chromating aluminium in Denmark

3.2.6 Chromic acid pickling of aluminium

Acid pickling of aluminium is also known as deoxidation. These days, a nitric acid solution is usually used, but not long ago a chromic acid solution was widely used: CrO₃ (3–4 g/l), NH₄HSO₄ (15–25 g/l), and NH₄F (1 g/l). Ten years ago, 100–200 tonnes of these chemicals were used each year (of which CrO₃ accounted for 20–25%), but today this method has largely disappeared. It is estimated that approximately 10 small-scale companies still use this process, and that the chemical consumption for this purpose is as low as approximately 2 tonnes/year, corresponding to approximately 250 kg Cr/year.

The pickling liquid is dragged out into the rinsing water. When too much chromium(III) and aluminium has accumulated in the bath, the entire vat of pickling liquid is discarded. It will typically be treated at the companies' own treatment plants, but a few companies send the discarded baths to Kommunekemi. It is necessary to reduce, neutralise and precipitate the rinsing water on an ongoing basis.

3.2.7 Chromic acid pickling of plastic

Plastic which is to be chromium plated is normally first pickled in a strong chromic acid solution containing 400 g/l chromium(VI) oxide and 400 g/L sulphuric acid. The pickling liquid will gradually degrade, with chromium(VI) oxide transforming into chromium(III), and eventually the pickling bath has to be discarded. Only one Danish company carries out plastic metallising, and it uses approximately 6,000 kg chromium(VI) oxide for pickling. The total treated surface of the plastic goods is estimated to be approximately 110,000 m²/year.

The discarded process baths are sent to Kommunekemi, but the continuous drag-out to the rinse water is treated at the company's own treatment plant, and the sludge is sent for reprocessing in Germany.

3.2.8 Anodising of aluminium

Anodising of aluminium is almost always carried out in sulphuric acid. Occasionally, however, anodising by means of chromium(VI) oxide is preferred in order to achieve particularly high resistance to corrosion, e.g. within the aviation industry. A chromic acid anodising bath typically contains 50–100 g/l. No more than five Danish companies carry out chromic acid anodising, and they do so on a very small scale. The total consumption of chromium(VI) oxide is estimated to be approximately 200 kg/year. The used baths are discarded when too much aluminium has been accumulated in them, and liquid from the bath is continuously being dragged out into the rinsing water. In principle, all the chromic acid added to the system becomes waste.

The corrosion resistance of phosphatised goods can be improved considerably by means of a final treatment in a weak chromic acid solution (100–500 mg/l of CrO₃) at a temperature of 20–45°C. Only a very small portion (< 5%) of the chromium is bound to the surface of the goods treated, whereas the rest ends up as waste when the solution is discarded. This process is carried out at approximately 30 Danish companies, but an increasing number of these companies (approximately 40%) now use a chromium-free method of passivation which yields the same results. It is very difficult to estimate the total surface area treated by means of chromium passivation.

Rinsing is not normally used after warm chromium passivation, but rinsing with deionised water may be employed after cold passivation. The discarded baths are usually treated at the companies' own treatment plants as the metal concentration is low.

3.2.10 Miscellaneous processes

Solutions which contain chromates can also be used for passivation of steel, brass and copper. These processes are, however, quite rare in Denmark, and it is difficult to establish the exact extent and scope of such production. It is estimated that the chromium consumption for these processes is negligible compared to the other processes described in this survey.

3.3. Pigments in paint and plastic

Some chromium compounds are used as pigments in paint and plastic. Chromium(III) oxides are the most widespread, but chromium(VI) oxides and various types of chromates are also used. According to the records in the Product Register, the industry expected to use a total of more than 80 different chromium compounds in pigments in 2001 (The Product Register, 2001). According to Den Danske Farve- og Lakindustri ("The Danish Paint and Varnish Industry"), consumption of hexavalent chromium compounds is falling or levelling out at low levels, while trivalent chromium is widely used within the industry (FDFL, 2002). In interviews, pigment manufacturers confirmed that consumption of hexavalent chromium compounds has fallen significantly in recent years (Liebeck Chem A/S, 2002; Scan-Rep ApS, 2002; Burcharth's Farve- og Lakfabrik A/S, 2002). For example, one manufacturer stopped using lead(II) chromate in the year 2000, marking a pronounced break with previous practice which involved annual consumption of 5–10 tonnes a year (Burcharth's Farve- og Lakfabrik A/S, 2002).

Previously, the hexavalent chromium compounds were mainly used in industrial paints and varnishes to be used on metal structures (Huse et al., 1992). The pigments used were chromium(III) oxide (for greens) and lead(III) chromate (for yellows, oranges and reds). Chromium(III) oxide is resistant to atmospheric conditions and heat, which makes it excellently suited as a pigment within the glass and ceramics industry and for ink cartridges in printers (Ullmann, 2002).

Lead chromates have excellent properties as pigments. The standard chromate, PbCrO₄, is made by means of precipitation where solutions of lead acetate or lead nitrate are added to potassium or sodium dichromate. Colour graduations are achieved by varying the type of lead chromate used (double salts and water of crystallisation) or by varying the production process (Encyclopædia Britannica, 2002). Lead(II) chromate is primarily used in maritime and industrial paint products. The use of lead(II) chromate in paint products is diminishing rapidly within the Danish market, but lead(II) chromate is still used in products intended for export to certain countries (Hempel, 2002).

Lead chromate has previously been used in the paint used to make red lines on cycle tracks. Such use has been banned in Denmark for several years, but up until 2001, lead chromate could be used in such products if they were intended for export. Up until this final ban entered into force, the annual consumption of lead chromate was slightly less than 1 tonne per year (LKF Vejmarkering, 2002).

In total, it is estimated that today, slightly more than 1 tonne of lead(II) chromate is sold every year to the paint and varnish industry in Denmark. If we go back just two or three years, the quantities sold were ten times higher (Andreas Jennow A/S, 2002). Today, chromates are only available on order, and customers can only order the products if they have permission to use them.

Chromium iron oxide can be used as a heat-resistant brown pigment, for example in oven varnish (Ullmann, 2002). It has not been possible to find any information on chromium iron oxide being used for this purpose in Denmark today. As a result, it is estimated that if such use occurs, the quantities involved must be quite small.

Previously, chromates of zinc and, to a lesser extent, sodium, potassium, strontium, ammonium and barium were used as rust preventives in paints. Today, there exist alternatives to chromates, and this means that chromates are rapidly being replaced (Hempel, 2002).

As was outlined in Chapter 1, one of the reasons behind the reduction in use of chromates in pigments is that chromates are regarded as being carcinogenic. This means that there are requirements on labelling of products which contain chromates, as well as requirements on how these products are handled.

Appendix D lists the information available in the Product Register about reported⁸ substances which contain chromium in active products. Due to the rules on confidentiality applied by the Product Register, the list includes only those substances which are used by more than three manufacturers.

As illustrated in Appendix D, chromium is used in several types of pigments and in highly variable concentrations. Sometimes, chromium is not used as a pigment, but serves another purpose. It may, for example, be used as a rust preventive. It has not been possible to obtain detailed information on the reasons for the occurrence of various chromium compounds for each individual use.

Table 3.10 provides estimates of the chromium content of paints and pigments.

Table 3.10
Import, export, production and supply of paints and pigments which contain chromium, 1998–2000 (Statistics Denmark, 2001b)

As is illustrated in the table above, the consumption of chromium is estimated to be between 12.6 and 116.7 tonnes. It is also estimated that chromium(VI) accounts for 1–2 tonnes of this total consumption. The content of chromium pigments in imported goods/products has not been assessed.

Studies have shown that considerable waste occurs in connection with painting projects. On the basis of Poulsen et al., 2002, it is estimated that 5–30% ends up as waste (which is assumed to be sent for incineration), and that 0.2–11% ends up in the sewers. This means that discharges of chromium to wastewater can be estimated at 0.03–13 tonnes of chromium, of which 0.002–0.2 tonnes are believed to be chromium(VI). At the same time, 0.6–35 tonnes of chromium is incinerated, of which 0.05–0.6 tonnes is estimated to be chromium(VI).

3.3.1 Pigments containing chromium in plastic

Plastic products can also contain chromium-based pigments. A Swiss study, which included approximately 500 types of plastic, showed that 20% of all PVC, 11% of all PP and 4% of all PE contain 100–1,000 mg chromium per kg (Bundesamt für Umwelt, 1995).

Previously, lead chromates were used as pigments in plastic products to create bright reds, yellows and greens. During the 1990s, the use of lead chromates in plastic has been replaced by organic pigments which do not contain any chromium (the PVC Information Council Denmark, 1999). It appears that chromium is not being used in pigments in plastic today, but it has not been possible to confirm this (the PVC Information Council Denmark, 2002; The Danish Plastics Federation, 2002). Chromium may occur in fibreglass-reinforced plastics, but it is likely that this is because of the fibreglass (The Danish Plastics Federation, 2002a).

On this basis, it is estimated that today, chromium is probably not used in pigments in plastic products manufactured in Denmark. We cannot, however, rule out the possibility that imported plastic products may be coloured using pigments which contain chromium. The exact amounts are not known.

3.4 Impregnation agents/Wood preservation

Chromium in the form of chromates and chromium(VI) oxide has previously been used in large quantities within the wood industry to protect wood against fungi and insects. The purpose of chromium in this context is primarily to fix the other active substances (arsenate, borate, fluoride, copper, etc.). During the period 1993–1997, approximately 115,000–145,000 tonnes of wood containing chromium was produced (Hansen et al., 2000).

The use of impregnation agents containing chromium has been reduced very significantly in Denmark through voluntary agreements, and since January 1997, agents which contain chromium may only be used with the appropriate dispensations. Ever since 1997, only a few manufacturers have been allowed to use CCB (copper, chromium and boron) and CCP (copper, chromium and phosphate) agents. In 1998, a total of 17,300 tonnes of wood containing chromium was produced, and approximately 37 tonnes of chromium was used in the process. The quantities produced corresponded to approximately 12% of the total production of impregnated wood (Hansen et al., 2000). At the end of 1999, only a single manufacturer had a licence to use CCP agents (Dansk Imprægneringsstatistik, 2000). Some of the impregnated wood imported into Denmark may still, however, contain chromium. According to Hansen et al., 2000, almost 60 tonnes of chromium were imported as an ingredient in impregnated wood.

According to the Danish EPA's register of pesticides, the sales of wood preservation agents which contain chromium have fallen in Denmark during the period 1998–2000 (The Danish EPA, 2001a). This is consistent with the fact that the number of manufacturers with a licence to use chromium for impregnation has fallen during the same period. Table 3.11 shows statistics for the sales of wood preservation agents in the years 1998–2000.

Table 3.11
Sales of wood preservation agents containing chromium (the Danish EPA, 2001a)

The figures given for sales of wood preservation agents in 1998 in (The Danish EPA, 2001a) are considerably lower than the quantities reported by Hansen, et al., 2000. This may be because not all quantities have been reported, or because the quantities used in production were bought the previous year and placed in storage. No figures have been established for imports of impregnated wood.

Table 3.12
Supply of chromium in impregnated wood in 1998, tonnes (Hansen et al., 2000)

On the basis of the sales illustrated in Table 3.11, it is estimated that production – and hence export – has fallen 20% since 1998, whereas import is deemed to be unchanged. Table 3.13 provides an estimate of the average supply of chromium in impregnated wood for the period 1998–2000.

Table 3.13
Estimated average supply of chromium in impregnated wood during 1998–2000, tonnes

Due to its protection against degradation, impregnated wood often lasts for a long time. This means that impregnated wood made up to fifty years ago is only now being discarded.

A few years ago, a major study on the use of chromium-impregnated wood in Denmark throughout 40 years was prepared (Hansen et al., 2000). In this study, it has been estimated that impregnated wood for building, construction and outdoor applications has a functional lifetime of approximately 40 years. It is also estimated that an additional ten years should be added to this period because a lot of impregnated wood is reused. It should be noted that the functional lifetime of impregnated wood varies greatly. For example, building components may have functional lifetimes of 100 years, whereas fence poles, terrace boards, etc., may have functional lifetimes of 30–40 years (Hansen et al., 2000).

During the use phase, the impregnated wood emits chromium to the environment. The exact quantities emitted depend on many factors, including exposure to water and rain. It is estimated that only small emissions to air occur as the wood dries out, and so this type of emission has not been considered. Only a few studies exist about emission of chromium during the use phase. On the basis of Hansen et al., 2000, it is estimated that emissions of 1–2% of the chromium to soil and the aquatic environment take place every year. Leaching of chromium into the aquatic environment primarily takes place during the first few years. Emissions to water are estimated to be around 0.3–0.6 tonnes chromium(VI) per year, and the emissions to soil are believed to be similar in scope.

Table 3.14 shows statistics on the waste quantities associated with impregnated wood containing chromium for the period 1998–2000.

Table 3.14
Calculated waste quantities of impregnated wood containing chromium for the years 1998–2000 (Hansen et al., 2000).

The waste quantities have been calculated on the basis of the assumption that 70% of the impregnated wood has a functional lifetime of 40 years, while the rest of the wood has a functional lifetime of 25 years. It is also assumed that 2% is wasted during production, and that this waste ends up as reprocessed waste (Hansen et al., 2000).

According to the study's projections on the future waste quantities, the total transport of chromium associated with reprocessed waste, landfilling, incineration and reuse is around 26 tonnes. This corresponds to approximately 0.2% of the quantity of wood (Hansen et al., 2000). Table 3.15 presents the relative shares accounted for by the various types of waste treatment.

Table 3.15
Chromium from impregnated wood to landfills, incineration, reuse and reprocessed waste (Hansen et al., 2000)

Even though only small quantities of wood are impregnated with chromium today, the chromium content in waste from impregnated wood will rise in the years to come. This is because of the long lifetime of impregnated wood. As illustrated in Figure 3.1, the chromium content in waste derived from impregnated wood will rise up until the late 2030s, at which time it will drop sharply to levels similar to those seen today. The drop in the curve around 2030 and the subsequent marked rise may be caused by the fact that the manufacturers have voluntarily phased out all use of impregnation substances which contain chromium, and had to use their stores before the substances became illegal in 1997.

Figure 3.1
Projected chromium contents in waste derived from impregnated wood and distribution by landfilling, incineration and reuse (prepared on the basis of Hansen et al., 2000).

Reprocessed waste has not been included in the figure above, but such waste will account for approximately half a tonne.

Figure 3.1 does not include impregnated wood which is disposed of in unauthorised ways. It should be expected that an unknown percentage of waste from private households is disposed of by means of uncontrolled landfilling, burning of garden waste and burning in household stoves.

Impregnated wood has attracted increasing attention in recent years. Since April 2001, a new requirement has been introduced on a trial basis in Denmark: all impregnated wood must be taken to recycling centres (R98, 2002). If this requirement becomes permanent, unauthorised disposal will decrease in the years to come. Kommunekemi A/S is currently planning a facility for the treatment of impregnated wood; construction is expected to commence within a year. This new plant will use a gasification process to separate out the heavy metals from the wood, allow the metals to be reprocessed and possibly recovered (Kommunekemi, 2002a; b). This means that we can expect a drop in the quantities of wood ending up in landfill if this new plant is established.

Projections on the chromium content in waste deriving from impregnated wood were also made in connection with a study of methods for treatment of various types of waste which contain heavy metals (Malmgren-Hansen et al., 1999). Figure 3.2 below illustrates the result of these projections. Compared to Figure 3.1, the development trend is approximately the same for the next twenty years. Nevertheless, the quantities are expected to be significantly lower (50–60% lower) than the quantities stated in Figure 3.1. As the projection extends further into the future, the figures become widely different. This illustrates the considerable uncertainties associated with such projections.

Figure 3.2
Projected contents of chromium, copper and arsenic in waste derived from impregnated wood, and total quantities of waste deriving from impregnated wood (Malmgren-Hansen et al., 1999).

3.5 Chromium used as a corrosion inhibitor

According to the technical reference work Ullmann, corrosion inhibitors made from sodium dichromate (Cr(VI)) are used in cooling towers and as additives in oil pipes in connection with transport of crude oil (Ullmann, 2002).

In actual fact, however, it turns out that corrosion inhibitor compounds containing chromium are no longer used for cooling towers in Denmark. Chromium compounds have previously been used in open cooling towers, but they have been phased out due to the aerosol formation associated with open cooling towers and the resultant emission of the dissolved Cr(VI) compounds (FORCE Technology, 2002).

Today, it is also rare to see any use of corrosion inhibitors containing chromium in connection with transport of crude oil in pipes. Transport of oil involves a range of auxiliary chemicals in addition to the chemicals used for oil extraction, but these days the products used hardly ever contain chromium (FORCE Technology, 2002).

In 1999, DHI Water & Environment carried out an environmental assessment of the auxiliary chemicals used by DONG in 1998 when transporting crude oil from the North Sea to the oil terminal in Fredericia, Jutland (Rasmussen et al., 2000). In connection with this assessment, the suppliers of chemicals to DONG submitted confidential information to DHI Water & Environment about constituents in the chemical products used for the oil transport. According to the information submitted, none of the chemical products included in the assessment contained chromium. DONG informs us that the chemical products used today are no different from those assessed by DHI Water & Environment in 1998 (DONG, 2002a). On this basis, it is estimated that chromium is not used as a corrosion inhibitor in Danish installations for transport of crude oil.

3.6 Tanning/leather

Leather tanned using chromium will contain chromium throughout its entire lifetime. This means that all import, export and production of leather and leather goods affects the mass balance of chromium in Denmark. Chromium(III) compounds are particularly widely used for chrome tanning.

3.6.1 Leather tanning

In 1999, only a single tannery in Denmark carried out chrome tanning of leather: Elmo Leather in Svendborg on Funen. The company stopped tanning leather using chromium in August 1999 and has focused exclusively on organic tanning since then (Elmo Leather, 2002). According to several sources with ties to the industry, no other active tanneries exist in Denmark (Danish Technological Institute, 2002b; Thomsen, 2002), although a few research tanneries may exist. Such research facilities would not use chromium (Elmo Leather, 2002).

According to Statistics Denmark, the supply of synthetic inorganic tanning agents was 164 tonnes/year during the period 1998–2000. This average is derived from the following quantities for each year: 243, 145 and 105 tonnes/year. According to Elmo Leather, these quantities roughly correspond to their consumption during approximately eight months of 1999 (approximately 170 tonnes of basic chromium(III) sulphate). The higher consumption rate in 1998, covering a whole year, can also be explained with reference to the consumption at Elmo Leather, whereas the supply in 2000 – a total of 105 tonnes – is less easily explained. The quantities consumed by Elmo Leather in 1999 correspond to 40 tonnes Cr₂O₃/year or 27 tonnes Cr(III)/year. Of this quantity, 1% – corresponding to 0.272 tonnes Cr(III)/year – went to a treatment plant where most of it ended up in the sludge. The remaining 99% ended up in the leather (Elmo Leather, 2002). Small quantities of chromium also end up in wastewater, approximately 0.02 tonnes Cr(III)/year, due to the use of metal complex dyes (Elmo Leather, 2002).

Several sources have informed us that a new and very large tannery has been established on Funen (Danish Technological Institute, 2002b). This facility will include chrome tanning among its activities, which means that it may affect the future mass balance of chromium in Denmark.

3.6.2 Leather in finished goods

Leather is imported as part of finished goods (shoes, bags, etc.) or in a pre-processed form which is then used to manufacture products in Denmark.

Many different types of shoes typically contain leather: fashion footwear, working shoes, boots, and sports shoes. Usually, only the uppers are actually made from leather, but some shoes also have leather soles. Whereas uppers are almost always chromium-tanned (Danmarks Skohandlerforening, 2002), leather soles for men's shoes are frequently made from organically dressed leather. Leather soles for ladies' shoes are typically made from chromium-tanned leather (Shoes-international, 2002). Approximately 24–25 million pairs of shoes are sold every year in Denmark (Danmarks Skohandlerforening, 2002). This figure includes all forms of footwear, including sports shoes, Wellington boots, sandals, etc. This corresponds to 4.5–4.7 pairs of shoes per person per year. According to a rough estimate from the industry, approximately 15,000,000 pairs are leather shoes (the interval is set to be 13,000,000 – 18,000,000) (Danmarks Skohandlerforening, 2002).

The vast majority of all the shoes sold within the Danish market are imported (Danmarks Skohandlerforening, 2002). ECCO Shoes is by far the largest manufacturer of shoes in Denmark, producing 10.5 million pairs per year. Even though the company sells considerable quantities of shoes on the domestic market, it only manufactures a relatively small number of shoes in Denmark; approximately 260,000–520,000 pairs per year (ECCO Denmark, 2002). According to our information, Jacoform is the only other Danish shoe manufacturer of any real significance (Danmarks Skohandlerforening, 2002), and that company produces only around 150,000–170,000 pairs per year. This is to say that the total Danish production of leather shoes is estimated at 410,000–690,000 pairs per year.

The incoming supply of leather shoes to Denmark calculated on the basis of data from Statistics Denmark is considerably smaller than the estimated 15 million pairs quoted by the industry. This in spite of the fact that the method of calculation employed by Statistics Denmark entails a risk of overestimating the supply. According to the department for goods statistics at Statistics Denmark, production carried out for a Danish company outside of Denmark is registered as Danish production (sales of Danish products) if the raw materials come from Denmark. At the same time, the products in question are registered as imports if they are shipped to Denmark from production facilities abroad. This means that such goods are included twice in supply statistics.

Table 3.16
Supply of leather shoes (1998–2000) according to Statistics Denmark

On the basis of the statistics and information from the industry, it is assumed that the supply of leather shoes to the Danish market amounts to 10,000,000–15,000,000 pairs of leather shoes per year. Shoes and sandals account for the relative shares illustrated in the table below.

Table 3.17.
Maximum and minimum supplies, divided into shoes and sandals.

On the basis of interviews with the industry (ECCO Denmark, 2002; Jacoform Sko, 2002), we have established that a pair of shoes usually contains approximately 261–378 g leather in the uppers, whereas sandals normally contain around 194–281 g. It is likely that many sandal "uppers" contain less leather than the quantities stated here. However, many ladies' sandals have leather soles, and these are likely to be chromium-tanned (Shoes International, 2002). It is assumed that men's shoes with leather outer soles have organically dressed outer soles, and that all other leather used in shoes is chromium-tanned.

Thus, the total supply in Denmark of chromium-tanned leather associated with shoes is estimated to be 2,455–5,338 tonnes chromium leather/year.

The chromium content in shoe leather is estimated to be 2.2%–5.0% weight/weight Cr₂O₃, but the average is likely to be around 3% weight/weight Cr₂O₃ or 2% Cr (Rydin, 2002). If we base our calculations on the average chromium content, the total supply of chromium into Denmark in the form of shoes can be estimated at 50–109 tonnes Cr/year.

The Danish EPA has measured Cr(VI) in concentrations greater than 3 mg/kg in two out of five pairs of shoes and a maximum concentration of Cr(VI) of 10.4 mg/kg leather. This corresponds to an average of approximately 4–5 mg Cr(VI)/kg. Based on this average, the supply of Cr(VI) associated with shoes can be established as 0.011–0.024 tonnes Cr(VI)/year. This is to say that virtually all the chromium found in shoes is Cr(III).

Shoes have relatively short lifetimes, as demonstrated by the large number of shoes bought by Danes each year. It is assumed that quantities corresponding to the annual supply are disposed of each year, and that discarded shoes are incinerated.

There is a certain supply of gloves, garments, belts and straps made from leather to Denmark. In terms of leather quantities, garments and protective gloves account for most of the supply. Only very small amounts of such goods are manufactured in Denmark, and the leather used to do so is usually imported.

According to Handskemagerlauget ("The Glove-makers' Guild"), 90% of all gloves are chromium-tanned, and leather used to make gloves needs a chromium content of 2–2.2% Cr₂O₃ (1.36–1.50% Cr(III)) (Handskemagerlauget/Randers Handsker, 2002). However, the Danish EPA has measured higher content levels (4.4% Cr₂O₃ or 3.0% Cr) in garments and gloves (Rydin, 2002). As almost all leather goods are imported, these figures are used as the average content of all leather goods.

Table 3.18.
Supply of leather goods (1998–2000) according to Statistics Denmark.

It is assumed that 90% of the leather is chromium-tanned, and so the annual supply of chromium associated with gloves, belts, garments and straps is 32–39 Cr/year. Of this amount, Cr(VI) accounts for 0.005–0.007 tonnes, while the rest is Cr(III).

Some leather garments are sold on as second-hand clothes, a fact which can prolong the leather's lifecycle in Denmark, but ultimately they are incinerated like all other clothes. The second-hand organisations do not usually send clothes outside Denmark (Folkekirkens Nødhjælp, 2002), preferring instead to sell them in Denmark or to send them for incineration. It is estimated that the total disposal of leather in gloves, garments, belts and straps corresponds to the supply.

Leather furniture is most frequently upholstered in chromium-tanned leather, which feels softer and more supple than leather tanned using vegetable agents. Organically dressed leather is not widely used, and is mainly used for hard upholstery (Design Møbler, 2002).

At Statistics Denmark, furniture is not classified according to the materials used for upholstery. This means that our estimates are based on interviews with people from the industry. There is no centrally compiled information about sales of leather furniture from the main associations within the industry: Dansk Møbelindistri and Møbelhandlernes Centralforening. The latter organisation represents 300 furniture retailers, accounting for 80% of all furniture sold to private individuals. They informed us that most leather in leather furniture is chromium-tanned, but that the chromium contents are typically not known. (Møbelhandlernes Centralforening, 2002).

A major Danish furniture retailer with a market share of approximately 24% sells around 24,000 leather suites (sets containing one three-seater and one two-seater sofa) each year and estimates the total sales in Denmark to be 100,000 sets a year (Inbodan, Idé Møbler, 2002). Sofa suites account for approximately 90% of all the leather furniture items sold in Denmark (Actona, 2002), and in terms of the quantities of leather sold, they also account for most of the leather sold as part of furniture in Denmark. In this document, the remaining 10% (of items) are assumed to be easy chairs; another popular type of leather furniture.

Each suite (one three-seater and one two-seater sofa) contains 250 square feet of leather (Inbodan, Idé Møbler, 2002; Actona, 2002), while an easy chair contains 50–60 square feet of leather. This is to say that approximately 30 million square feet of leather is sold in Denmark each year in the form of leather furniture. Assuming a thickness of 1–1.5 mm (Elmo AB, 2002) and a density of 0.86–1.02 tonnes/m³ (Perry et al., 1997), this makes for a total of 2,361–4,359 tonnes of leather/year. If we base our calculations on the industry's estimate that most of this leather is chromium-tanned (80%–100%) and that it contains 3.0%–5.0% Cr₂O₃, the supply of chromium from leather in leather furniture in Denmark is around 51–119 tonnes Cr/year.

It is assumed that leather furniture is disposed of by means of incineration. Leather furniture is replaced with greater frequency in Denmark than in other countries, and it is estimated that the quantities disposed of correspond to the supply.

The information on the supply of luggage, bags, purses, etc., with leather surfaces comes from Statistics Denmark.

Table 3.19.
The supply of luggage, briefcases, bags, and purses (1998–2000) according to Statistics Denmark

It has not been possible to obtain exact information about the relative share accounted for by chromium-tanned leather. We do, however, know that Adax, a major Danish manufacturer of leather accessories, only uses organically dressed leather in their products (Adax, 2002). As leather used for leather accessories does not normally need to be particularly soft, it is assumed that much of the leather used for luggage and handbags is organically dressed (70%–80%). It is also assumed that chromium-tanned leather accounts for a greater percentage of the total quantities of leather used for purses, wallets and small cases (50%–80%). We estimate that leather accounts for 70%–90% of the total material contents of the goods, and that the average chromium content of this leather corresponds to the average chromium content of leather garments, belts and straps. This makes for a total supply into Denmark of 4.0–8.0 tonnes Cr/year in the form of luggage, bags, wallets, cases and similar leather accessories. A very small portion of this chromium may be Cr(VI), while the rest will be Cr(III).

A brief calculation based on the size of the Danish population and the number of bicycles in Denmark shows that the annual supply of leather in the form of bicycle saddles is in the region of two tonnes. This is to say that the potential chromium contents involved are very small. If all leather saddles were chromium-tanned, this would correspond to 0.030–0.090 tonnes Cr/year. It is estimated that the supply of chromium associated with other leather goods such as horse saddles and leather upholstery for cars is quite limited.

3.6.2.6 Leather as a raw material

The leather produced in Denmark or imported as a raw material for production of leather products is included in the statistics on the various uses outlined in the above. As a result, these leather quantities are not addressed in any detail here. On the basis of data from Statistics Denmark, we can, however, see that some leather is imported into Denmark as a raw material. According to the statistics, this is mainly due to sales of domestically produced goods (wet blue chromium-tanned leather). The statistics also indicate major sales of domestically produced goods in 2000, even though the industry states that no production took place in this year. These sales may, however, stem from stored goods produced in previous years.

Table 3.20.
Supply of raw leather (1998–2000) according to Statistics Denmark.

3.7 Accelerators, catalysts, hardeners

According to technical literature on the subject (Ullmann, 2002), compounds containing chromium are used as accelerators and catalysts in the production of a wide range of products. According to the Product Register, such compounds are also used as hardeners in the products themselves. The following is a look at a number of products and processes which involve chromium in the form of accelerators, catalysts or hardeners.

3.7.1 Catalysts for chemical processes

Chromium can catalyse a range of different chemical processes used within the chemical industry. For example, chromium-aluminium catalysts are used for dehydrogenising butane and butadiene, for polymerisation of ethylene, and for aromatising n-alkanes (propane transformed into benzene). Binary oxide catalysts containing chromium can be used for hydrogenising, dehydrogenising, methanol synthesis and shift reaction with water (steam). Chromium can also be used as a catalyst in heterogeneous synthesis of methanol. In the processes mentioned here, the active component is the Cr(III) ion from Cr₂O₃ (Ullmann, 2002). Chromium can also be used in Ziegler-Natta catalysts, which are used for production of polymers (University of Aalborg, 2002). It has not been possible to identify enterprises using chromium as catalysts for these or other processes in Denmark (University of Aalborg, 2002). The association of Danish plastics manufacturers does not know which companies – if any – use chromium catalysts (The Danish Plastics Federation, 2002), and crude plastic is not manufactured in Denmark at all (Statoil, 2002b). Chromium may also be used to crack alkanes, but the only refinery in Denmark (owned by Statoil and located in Kalundborg) does not use chromium as a catalyst (Statoil, 2002).

Data from Statistics Denmark show that there is a relatively large supply of catalyst materials other than nickel and precious metals in Denmark, but at the same time the Product Register lists only few catalysts which contain chromium. Consequently, it is assumed that most of the catalysts occurring in the total supply do not contain chromium.

Haldor Topsøe is the only manufacturer of catalysts in Denmark. This company produces catalysts containing chromium for the water gas shift reaction CO + H₂O = H₂ + CO₂, which is widely used within the chemical industry. A total of 98% of their catalysts are exported, and there are no other major facilities of this type in Denmark, although it is likely that some small ones exist (University of Aalborg, 2002). Unfortunately, time constraints prevented Haldor Topsøe from contributing an estimate of their consumption of chromium and production of catalysts containing chromium. However, as the chromium raw materials are imported and the vast majority of the catalysts containing chromium are exported, the production carried out in Denmark does not have much impact on the supply. A competitor, ICI-Synetix, also makes catalysts for this reaction. Their catalyst, known as Katalco 71–5, is intended for high-temperature shift reactions and typically contains 9% Fe₂O₃ and < 10 ppm w/w Cr(VI) (Synetix-ICI, 2002a). It is expected that these contents also apply to the catalysts produced in Denmark (University of Aalborg, 2002). Catalysts for low-temperature shift reactions do not contain chromium (Synetix-ICI, 2002b; University of Aalborg, 2002). Small facilities for shift reactions are estimated to contain around 25–50 kg catalyst, which is replaced every two or three years (University of Aalborg, 2002). If we assume that there are 100 small facilities in Denmark, this adds up to 61.2–122.4 kg Cr(III)/year.

The Product Register contains a large number of accelerators and catalysts containing chromium. The products contain 15.6–52% Cr(VI) in the form of chromium(VI) oxide or 0.13–0.26% Cr(VI) in the form of strontium chromate.

Statistics Denmark has information on the supply of catalysts without nickel and precious metals, but their chromium content is not specified.

Table 3.21.
The supply of catalysts and reaction starters (1998–2000) according to Statistics Denmark

If we assume that 1–2% of the total supply consists of catalysts which contain chromium and that these catalysts have chromium contents of the type and quantity indicated in the Product Register, the supply of chromium in catalysts adds up to 0.1–100 tonnes Cr(VI)/year. However, one expert estimates the consumption of catalysts containing chromium in Denmark at just a few kg per year (University of Aalborg, 2002), so the actual consumption is estimated to be 0.1–1 tonne.

The emissions to the environment associated with use of catalysts containing chromium are believed to be very small, much less that 1 kg/year. This partly because the use of such catalysts is quite limited, and partly because the catalysts are most likely disposed of in ways which entail very small losses into the environment, e.g. at Kommunekemi.

3.7.2 Accelerators in plastic

It would appear that chromium is not added as an accelerator to any kind of plastic (Kemikalieinspektionen Sverige, 1995; Statens Forurensningstilsyn, 1991; Umweltsbundesamt, 2000; PVC Information Council Denmark, 2002), but it may occur due to impurities entering the plastic during production. This is the case for polypropylene and polyethylene (Statens Forurensningstilsyn, 1991; Ullmann, 2002). The quantities occurring in the form of impurities are believed to be very small. Some chromium contents have been measured in various types of plastic packaging: 670 ppm in plastic trays, 390 ppm in plastic lids, 2,500 ppm in plastic boxes, 2,900 ppm in a plastic beer crate. These occurrences are mainly associated with pigments (Andreasen et al., 1997). As is mentioned in section 3.3.1 above, chromium is not used as a pigment in Denmark. It would appear that no plastic synthesis takes place in Denmark (Statoil, 2002; the PVC Information Council Denmark, 2002), but there is considerable import of plastic raw materials for a wide range of companies which process plastic.

Table 3.22
Supply of polyethylene and polypropylene (1998–2000) according to Statistics Denmark

If we assume that the residual contents of chromium from catalysts do not exceed 2 mg/kg (a value stated in the CN), the maximum supply of chromium associated with unprocessed polyethylene and polypropylene is 0.69 tonnes Cr/year.

3.7.3 Accelerators in paint

Chromium is not used in paints manufactured in Denmark, nor in imported paints registered in the Product Register, except insofar as chromium occurs in pigments. The most common chromium pigments are chromium yellow (PbSO₄, PbCrO₃), chromium oxide green (Cr2O3) and chromium green (PbCrO₄, PbSO₄, FeNH₄Fe(CN)₆) (Poulsen et al., 2002). A 1996 study of chemical substances in paint on the Swedish market shows the same result (Ahlborn et al., 1996). The available literature also fails to present any examples of chromium in paint except in the form of pigments (Bielman, 1993). Nevertheless, the Product Register includes records of 13 "paint and varnish hardeners" which contain some chromium. For some hardeners, chromium contents are said to be as high as 46%. Such chromium takes the form of chromium(III) oxide. The remaining products have small quantities (0–0.46%) of organic compounds containing chromium (possibly pigments) or inorganic Cr(III) compounds. The chromium content of such products is very low, and it is estimated that the use of chromium in pigments is by far the main reason behind chromium contents in paint. Statistics Denmark's survey of foreign trade (by products and country) does not include an inventory of hardeners for paint (Statistics Denmark, 1999; 2000; 2001).

3.7.4 Concrete hardener

The Product Register has a product listed under the group heading H1510 (Concrete hardeners) which contains 0.01% chromium in the form of chromium(III) oxide, Cr₂O₃. When asked, sources within the industry (Cementfabrikkernes tekniske Oplysningskontor, 2002b; Dansk Bykemi, 2002) did not believe that chromium is used for products where concrete is added. Concrete hardeners are not included in Statistics Denmark's survey of foreign trade by product and country (Statistics Denmark, 2001), so the exact supply is not known. It is, however, estimated that the quantities involved are very small.

3.7.5 Fillers, sealants, etc.

The Product Register has a number of products which contain chromium listed under the heading U510 (Fillers, sealants, etc.). Most of these have a chromium content of 0–21% Cr in the form of chromium(III) oxide. Other substances containing chromium can occur, but the information on these substances is confidential according to the rules governing the Product Register. The information has, however, been taken into account when estimating the total supply.

Table 3.23
Fillers, sealants, etc. which contain chromium and are featured in the Product Register. Notification of other substances has been submitted, but the rules governing the Product Register does not allow a detailed account.

Nowhere in the literature is it stated that chromium is used as an agent in fillers and sealants (Evans, 1993; Flick, 1978). Persons within the industry have stated that they do not believe that chromium is used in fillers in Denmark (FOSROC, 2002). A study of a large number of data sheets for fillers and sealants from the companies 3M, Bostik and Alfix A/S (available on the Internet) did not reveal any chromium contents in these products (3M, 2002; Bostik A/S, 2002; Alfix A/S, 2002).

In theory, chromium could occur in fillers in the form of pigments. In actual fact, however, it is rare that customers want the colours which chromium pigments could provide in fillers, and there are no records of use of chromium pigments for this purpose within the industry (FOSROC, 2002; Dansk Bykemi, 2002). The most frequently used pigment in fillers is TiO₂ (Evans, 1993). It has not been possible to identify any filler which contains chromium(III) oxide or zinc chromate. Fillers may, however, contain cement, and so may also contain small quantities of chromium (see section 4.2). If we assume that CN no. 32141 – Sealants – are fillers, and that the cement content of this product group is 25% at most with chromium contents corresponding to those of standard, chromium-reduced cement (less than 2 mg Cr(VI)/kg), the total supply of Cr(VI) associated with fillers will not exceed 0.008 tonnes Cr/year.

Table 3.24
Supply of fillers, sealants and putties (1998–2000) according to Statistics Denmark

3.7.6 Putties

Like fillers, putties also contain cement – and therefore chromium. This category includes floor surfacers (self-levelling or not) (Casco, 2002). In addition to this, data from the Product Register shows that chromium(III) oxide is a common constituent of putties, which may contain up to 21% Cr. This makes for a maximum supply of 2,321 tonnes Cr(III)/year. In view of the fact that interviewees within the industry do not believe that Cr is used in putties at all, this theoretical supply is not realistic. Based on the fact that people within the industry deny any use, 1–2% of the figure stated above seems more likely. This corresponds to 23–46 tonnes Cr(III)/year. The supply of Cr from the cement included in the putties and compounds will not exceed 0.011 tonnes Cr(VI)/year and 0.18 tonnes Cr(III)/year. This means that all in all, the total supply of Cr associated with putties is 23–47 tonnes Cr(III)/year and 0–0.011 Cr(VI)/year.

Table 3.25
Putties which contain chromium and are featured in the Product Register. Notification of other substances has been submitted, but the rules governing the Product Register does not allow a detailed account.

3.7.7 Glue

The Product Register includes records of a number of hardeners which are used for glues and contain chromium. These hardeners contain 0–9% Cr in the form of inorganic Cr(III) or Cr(VI) salts. A study of a large number of data sheets for glues from the companies 3M, Bostik and Alfix A/S (available on the Internet) did not reveal any chromium contents in these companies' products (3M, 2002; Bostik A/S, 2002; Alfix A/S, 2002).

Chromium is, however, used to a limited extent in separate hardeners for white, waterproof PVA glues to be used with wood (Casco, 2002). This type of glue is produced by companies such as Casco and Dana. Normally, hardeners for PVA glue are made by means of an aluminium salt, but the ability to withstand water is increased by means of Cr hardeners. This type of hardener is not produced in Denmark (Casco, 2002). A Danish company with a significant market share (estimated at between 30 and 70%) has calculated that it imports and sells PVA glue hardeners in quantities corresponding to 0.077 tonnes Cr a year, and as a result the total supply is estimated to be around 0.11–0.26 tonnes Cr/year. Confidential information from the Product Register indicates that most of this chromium is Cr(III).

3.8 Textiles

When chromium appears in textiles, it usually does so as part of a dye or pigment added to the textile fibres, as an impurity in a dye/pigment or, for man-made fibres, as impurities in the relevant man-made material.

3.8.1 Chromium in dyes and pigments

Chromium occurs in several kinds of dyes and pigments as complex formers and impurities.

Chromium dyes are mainly used for wool, but also for silk and polyamide. What happens is that potassium dichromate (K₂Cr₂O₇) is added in addition to the dye itself, often an azo dye. Cr(VI) from the potassium dichromate is absorbed into the textile fibre (bound to amino acids) and is reduced to Cr(III). The Cr(III) moves slowly within the fibre, forming complexes with the dye which is then fixed in the fibre. This makes the textile highly washable. Dyes of this kind are not sold in Denmark (Larsen et al., 2000; Ullmann, 2002).

Metal complex dyes are used for wool, silk and polyamide. Within dyes of this type, a metal ion – such as Cr – is complex bound to one or two dye molecules containing –OH, –NH₂ or –COOH groups. When the metal dye complex is added to a textile, it is bound in the same manner as the chromium dyes (Larsen et al., 2000).

Because chromium can act as a catalyst, it is often found as an impurity in dyes and pigments. The content of Cr as an impurity in azo dyes has been measured as being approximately 6 mg Cr/kg dye on average (Burg et al., 1980). Potassium dichromate may be used as an oxidation agent for oxidation of, for example, sulphur dyes, but such use is less common (Ullmann, 2002; Larsen et al., 2000).

3.8.2 Chromium as an impurity in textile fibres

Chromium is used as an accelerator in the production of a number of plastic types. As a result, one might well expect to find small amounts of chromium in textile fibres. However, chromium is mainly used for production of polyethylene and polypropylene, and these materials are not very widely used as textile fibres. While it is true that polypropylene is used for special sports underwear, the quantities involved are small (Larsen et al., 2000).

3.8.3 Supply of chromium with textiles

Chromium pigments are not used to dye textiles in Denmark and most of Western Europe (Danish Technological Institute, 2002a), and the use of metal complex dyes is also very limited (Remmen & Rasmussen, 1999). This means that it is unlikely that textiles made with dyes containing chromium are produced in large quantities in Denmark. Thus, there will be very little export of chromium with textiles produced in Denmark. All this means that chromium associated with textiles will primarily reach Denmark in connection with import of textiles.

Dyes containing chromium are mainly used for wool textiles. Generally speaking, high chromium concentrations can be found in wool. However, very high concentrations have also been found in printed textiles made from other fibres, so the averages for textiles made from wool and other fibres are more or less identical (Larsen et al., 2000). According to a Swiss study, protective clothes may contain high concentrations of chromium (Bundesamt für Umwelt, 1995). The use of chromium pigments in safety colours may be one reason for this. However, the protective clothing made by Kansas – one of Europe's largest producers of protective clothing and a prominent player within the Danish market – does not contain chromium in concentrations which can be detected (Kansas, 2002). As a result, protective clothing is treated like any other clothing in calculations.

On the basis of Larsen et al. (2000), we can make a rough estimate to the effect that the chromium content of wool products is 100–300 mg Cr/kg wool on average. In a number of other textiles – including polyester, silk, and cotton with PVC prints – average values of around 100–300 mg Cr/kg textile were measured for those textiles where the chromium concentrations were above the detection limit (approximately 40%). As regards impurities in azo dyes, the contents can be calculated as being around 0.14–0.22 mg Cr/kg textile (Larsen et al., 2000).

Statistics Denmark divides textiles into categories such as wool and man-made fibres, but does not distinguish between various kinds of man-made fibres. Danish experts cannot provide any data on consumption by fibre type (Dansk Textil og Beklædning, 2002; Danish Technological Institute, 2002a). Consequently, this survey is based on information on consumption by fibre type at EU level (1998); see table 3.26.

Table 3.26
Consumption of fibres for clothing in the EU, by type (EU, 1998).

According to Larsen et al. (2000), the annual consumption of textiles in Denmark is approximately 22 kg/person. Of this amount, textiles for clothing account for 13 kg/person. This corresponds to a total consumption of 116,600 tonnes textiles/year, of which 68,900 tonnes/year are used for clothing.

The relative consumption of fibres by type is not known for fibres other than those used in textiles for clothes. We do, however, know that wool, cotton and various man-made fabrics are used, for example, for furnishing fabrics. It is estimated that synthetic fibres are more widely used within areas other than the clothing industry than within the clothing industry itself. For example, polyester is the most widely used textile fibre in tyres for cars and small lorries (Williams, 2002). As a result, we have applied a slightly different estimated consumption of fibres for purposes other than clothes. This estimated consumption is shown in table 3.27.

Table 3.27
Consumption of fibres for purposes other than clothing, by type (estimated)

By using these figures, we can calculate the supply of textiles in Denmark by fibre type. The results are shown in Table 3.28.

Table 3.28
Supply of fibre types in Denmark

Effort has also been made to calculate the total import and supply of wool by summing up data from Statistics Denmark for all CN entries for garment textiles and carpets made from wool. In 1999, for example, the import was calculated at 3,210 tonnes wool/year and the supply at 3,210 tonnes wool/year. These figures are less than those shown in Table 3.28, which is partly because they do not include all goods made from wool, furnishing textiles, etc. As a result, the calculations are based on the figures in Table 3.28.

We can calculate the supply of chromium associated with textiles by basing our calculations on the estimated contents from section 1.3.1. For these calculations, it is assumed that 40% of the non-wool textiles have chromium contents as measured, and that 50% of all textiles are dyed with azo dyes.

The calculations show that the supply of chromium with textiles to Denmark is around 5.6–16.7 tonnes Cr/year.

3.8.4 Disposal

Danish production of textiles leads to considerable amounts of textile waste, but it is estimated that the chromium content of this waste is very low and hence without significance in this context. It is assumed that the disposal corresponds to the supply less the net export of second-hand clothes. It is also assumed that no accumulation of textiles occurs in Denmark. According to Statistics Denmark, the year 1999 saw net exports of 9,381 tonnes of second-hand clothes (Statistics Denmark, 2000). Thus, we conclude that a total of 107,219 tonnes of textiles are disposed of every year. Textiles are mainly disposed of by means of incineration along with domestic waste, which is to say that around 5.1–15.3 tonnes of chromium from textiles is incinerated each year.

3.9 Electronic storage

3.9.1 Use of chromium in magnetic media

Chromium is used in magnetic media to store sound, images or data. Even though optical media such as CD-ROMs are becoming increasingly popular, the year 1999 still saw considerable use of magnetic tapes of various kinds, some of which contain chromium. The chromium compounds used in magnetic media are CrO₂ (Cr(IV)) and Cr₂O₃ (Cr(III)), which have excellent magnetic properties (Ullmann, 2002; TDK-Scandinavia, 2002; EMTEC, 2002a). There are no manufacturers of magnetic media in Denmark, so all goods of this kind are imported.

The companies Emtec, TDK, Sony and Fuji have been contacted with a view to collecting information about the chromium compounds used in their products – and the quantities used. Chromium is mainly used in VHS video tapes and audio tapes. There are a few other niche products which contain chromium. Chromium can also appear as unwanted impurities in magnetic materials in very low concentrations. One manufacturer tells us that their Mini Discs contain 0,000009 g Cr₂O₃ per Disc, which corresponds to approximately 1 g chromium per 150,000 Mini Discs. The level of chromium in such products can only be described as very low.

Magnetic storage media comprise a wide range of product types. Table 3.29 shows some of the products which fall within this heading. The table has been prepared on the basis of information from manufacturers of storage media (TDK-Scandinavia, 2002; EMTEC 2002a; Sony Denmark, 2002) and the industry associations for electronic products (Brancheforeningen Forbruger Elektronik (BFE)) and Brancheforeningen for Elektronik, 2002). The so-called professional tapes constitute a very varied product group. According to Emtec, chromium is not used in significant quantities in these products (EMTEC, 2002a), but it has not been possible to obtain information about the chromium content in all product types.

According to producers of magnetic storage media, by far the most significant source of chromium in such products is chromium which is added as a component in audio tapes and – particularly – video tapes. Both audio and video tapes are available in versions with and without chromium.

Table 3.29
Various magnetic storage media. Any presence of chromium is indicated.

3.9.2 Chromium in VHS video tapes

By weighing randomly selected VHS tapes, we have established intervals for the weight of pre-recorded tapes (purchased with pre-recorded films or similar) and blank tapes. The result is shown in Table 3.31.

Table 3.31
Weight of randomly selected VHS tapes

According to calculations made by Statistic Denmark, the supply of pre-recorded VHS tapes in Denmark is 1,396 tonnes per year, corresponding to approximately 5.7 million tapes per year with an average weight of 245 g including covers.

Sales of pre-recorded tapes are on the rise and now exceed the sales of blank tapes. Sales of blank VHS tapes amount to approximately 5 million a year, and the sales of pre-recorded tapes are estimated to be around 6–7 million per year (Brancheforeningen for Elektronik, 2002).

On this basis, it is estimated that the supply of VHS tapes in Denmark is 10.7–12 million VHS tapes each year.

According to information from producers, each tape contains 0.16–0.21 g chromium. It is estimated that 95%–100% of all tapes contain chromium. The total quantities of chromium correspond to 1.6–2.5 tonnes of chromium per year, mainly in the form of Cr(III). Cr(IV) occurs less frequently in tapes.

On the basis of sales statistics for VHS and DVD equipment, it is estimated that the sales of both pre-recorded and blank VHS tapes will fall in the long term. The sales of VHS equipment remain stable, whereas DVD equipment is sold in ever greater numbers (Brancheforeningen for Forbrugerelektronik, 2002). This leads to the natural assumption that the supply of VHS tapes will fall.

After use, and as the technology becomes obsolete, video tapes will end up in the waste system.

3.9.3 Chromium in audio tapes

Audio tapes are sold in much smaller quantities than video tapes in Denmark. No reliable surveys of the sales in Denmark are available. The producers estimate the sales to be around 1.0 million tapes per year, of which approximately 10% contain chromium (EMTEC, 2002b; Sony Denmark, 2002). If they contain any chromium at all, audio tapes contain approximately 2 g chromium compounds per tape (confidential information from manufacturers). In audio tapes, CrO₂ is typically used, whereas video tapes typically contain Cr₂O₃. On this basis, the supply of chromium associated with audio tapes has been calculated to be approximately 0.12 tonnes chromium per year, mainly Cr(IV).

The market for audio tapes is dwindling rapidly as audio tapes are replaced by digital technologies such as Mini Disc and CDs.

After use, and as the technology becomes obsolete, audio tapes will end up in the waste system.

3.9.4 Supply of chromium with magnetic media

The total supply of chromium associated with magnetic media is estimated to be around 1.8–2.6 tonnes Cr/year.

3.10 Laboratory chemicals

Chromium is part of a large number of laboratory chemicals. Among other things, it is used as a catalyst, an oxidation agent, and a pH regulator. These chemicals are often sold and used in very small quantities (Bie & Berntsen, 2002; VWR, 2002). As a result, it has not been possible to get a total overview of the quantities consumed in Denmark.

Table 3.32 shows information from the Product Register about the expected uses of chromium compounds as laboratory chemicals and the concentrations in which they are used.

Table 3.32
Laboratory chemicals containing chromium (The Product Register, 2001).

Generally speaking, suppliers of chemicals for laboratories in Denmark supply the chemicals which their customers demand, and this is also true of the chemicals listed in Table 3.32. (Bie & Berntsen, 2002; BASF, 2002; VWR, 2002). It has not been possible to obtain information about the chromium compounds that are actually sold by suppliers today. This is because the quantities involved are small, which means that the sales are not registered centrally. Based on information from suppliers, it is assumed that efforts are made to avoid use of hexavalent chromium compounds due to their harmful impact on health.

Potassium dichromate and chromium oxide are used in laboratories as oxidation agents. In the widely used COD (Chemical Oxidation Demand) measurements, potassium dichromate is used as an oxidation agent to degrade organic matter in water. COD measurements are used to measure oxygen consumption in water, thereby indirectly measuring its content of organic matter. As a result, COD measuring is carried out every day at most Danish sewage treatment plants. On the basis of VWR (2002), it is estimated that 150,000–250,000 COD analyses are carried out every year in Denmark. According to Dansk Standard, 217.5 ml of reagent is used per test, containing 59 mg potassium dichromate. This means that 9–15 kg potassium dichromate is used every year, corresponding to 3–5 kg hexavalent chromium. In a 1998 study of analyses of chemical oxygen demand (COD) and non-volatile carbon (nonVOC) in wastewater, the annual consumption of chromium for COD was estimated to be 2–10 kg (DHI, 2002). It seems unlikely that the COD tests will be replaced by an alternative method anytime soon, so we must expect that the consumption of potassium dichromate for COD measuring will remain unchanged in future.

Chromic sulphuric acid, which is a mixture of 5% potassium dichromate and 95% sulphuric acid, is used to clean laboratory glassware. Today, chromic sulphuric acid is only used to a limited extent because of its dangerous properties. It is estimated that less than 100 litres of chromic sulphuric acid are used each year in Denmark (VWR, 2002), and that this use will cease in the long term.

Chromic sulphuric acid is also used in connection with oxidation of alcohols for carboxyl acids, the so-called Jones reagent (CrO3/H2SO4/H2O) (The Royal Veterinary and Agricultural University, 2001). The use of the Jones reagent is deemed to be limited.

When the chromium content of a metal compound is determined on the basis of atomic absorption, chromium is used as a standard to calibrate the measuring equipment (VWR, 2002), (DHI, 2002; Bie & Berntsen, 2002). It is estimated that very small quantities of chromium are used for this purpose.

In total, it is estimated that laboratory chemicals account for less than 0.1 tonne chromium each year, primarily chromium(VI).

Danish legislation states that after use in laboratories, chemicals which contain chromium must be submitted for special treatment as dangerous waste. Almost 95% of all chemical waste is disposed of at Kommunikemi A/S, while a smaller portion of the laboratory waste is disposed of at Special Waste System in Nørre Alslev (Waste 21; the Danish EPA, 1999).

The dangerous chemical waste from laboratories is mainly disposed of by means of incineration. Table 3.33 below shows the relative shares accounted for by the various treatment methods.

Table 3.33
Special treatment of chemicals from laboratories 1999–2000 (Prepared on the basis of Affaldsstatistik 2000, 2001).

At Kommunekemi, waste incineration takes place at 1,200°C, whereas standard incineration plants only reach temperatures of 900–1,000°C. The flue gas from all incineration carried out at Kommunekemi is cleaned by means of sophisticated technology. Slag and fly ash ends up at a controlled landfill where test samples of the percolate are taken regularly. If the limit values are exceeded, the percolate is returned for incineration (Kommunekemi, 2002a).

3.11 Other uses of chromium compounds

3.11.1 Fireproof products and foundries

Due to its high melting point (2,435°C), chromium(III) oxide is also used in fireproof products such as firebricks, fireproof sand, stone and clay. Such products are used, for example, in melting furnaces and foundry furnaces.

Most mixtures are based on magnesium-chromium ironstone. They are mainly used within the steel, copper and cement industries to line furnaces and similar installations against heat and flame in connection with production.

Table 3.34
Import, export, production and supply of firebricks 1998–2000 (Statistics Denmark, 2001b).

As illustrated in Table 3.34, the use of firebricks is relatively limited in Denmark. Only a few companies in Denmark have the facilities to melt and cast materials and goods. For example, Aalborg Portland and Det Danske Stålvalseværk are the only companies in Denmark which produce cement and steel, respectively. In 2001, Det Danske Stålvalseværk placed 5,000 tonnes of firebricks in their furnaces, and some of these bricks contain chromium. According to the company's own estimates, this corresponds to about two tonnes of chromium (Det Danske Stålvalseværk, 2000b). It has not been possible to obtain further information about the consumption of firebricks, which in turn means that it has not been possible to arrive at figures for the relevant chromium contribution except for those stated in Table 3.34. It is estimated that some firebricks burn away, thereby ending up in the steel products or emissions. The rest are eventually replaced and end up in landfills. From there, no further emissions of chromium take place.

3.11.2 Chromium used in drilling mud when drilling for oil

Chromium lignosulfonates have previously been used in drilling mud as a conditioning and dispersing agent when drilling for oil (Ullmann, 2002; Offshore-environment, 2002) and are still available on the international market. Back when chromium lignosulfonates were used, discarded drilling mud from offshore drilling rigs was usually dumped in the ocean, while drilling mud from land-based drilling rigs was sent to landfills. Use of chromium lignosulfonate in drilling mud is not expected to contribute to chromium contents in the extracted oil, as the drilling mud is removed from the borings before oil extraction commences (Sea Consult, 2002).

In the Danish part of the North Sea, oil extraction is carried out by Maersk Oil, Statoil and Amarada Hess, but Dansk Olie og Naturgas (DONG) carried out the actual drilling work for some of these companies. DONG has built a database of all the drilling chemicals used and their constituents. According to this database, no chromium compounds – and hence no chromium lignosulfonates – occur in the chemicals used (DONG, 2002b). Statoil confirms that they do not use drilling chemicals containing chromium or chromium compounds in connection with their oil activities in the North Sea (Statoil, 2002a). Similarly, Maersk phased out their use of chromium lignosulfonate in the North Sea in the mid-1980s (Sea Consult, 2002).

In 1999, DHI Water & Environment carried out an environmental assessment of the offshore chemicals used in 1993 in quantities greater than 1 tonne (DHI et al., 1999). In this connection, suppliers of chemicals to the Danish part of the North Sea submitted confidential information about the contents of the chemical products used to search for and extract oil. The study comprised 273 chemical products, containing 306 different chemicals. None of these chemicals contained chromium or chromium compounds.

On this basis, the assessment is that chrome lignosulfonate is no longer used in the North Sea in connection with drilling activities. If chrome lignosulfonate is used elsewhere in the world, it will not contribute to chromium levels in crude oil, and so it will not affect the quantities of chromium entering Denmark. It is also estimated that chromium and chromium compounds are not widely used in connection with oil activities in the North Sea, except to produce the stainless steel used at the facilities.

3.12 Summary

Chromium compounds are used for a wide range of functions. Table 3.35 shows estimated figures for consumption and distribution of chromium in connection with compound use in Denmark.

Table 3.35
Estimated supply and distribution of chromium associated with use of chromium compounds in Denmark (tonnes Cr/year).