| Contents |

Environmental Project no. 793, 2003

Mass Flow Analysis of Chromium and Chromium Compounds

Contents

Preface

The report was submitted to the Confederation of Danish Industries (DI) for consultation.

Summary and conclusions

Introduction

A mass flow analysis of chromium and chromium compounds has been carried out. This survey updates the previous mass flow analysis of chromium and chromium compounds (Tørsløv & Hansen, 1985). The new analysis has been carried out on the basis of information from Statistics Denmark, the Danish Product Register, previously completed mass flow analyses, and information from importers and manufacturers. The work presented in this survey has been ranked in order of priority on the basis of general knowledge about the use and occurrence, hazardousness and potential exposure of chromium as well as on the basis of a preliminary analysis of statistical information about the chromium supply to the community via goods and products.

Thus, a detailed survey of the use of chromium for surface treatment and in wood preservatives, pigments, leather tanning, laboratory chemicals, accelerators/catalysts/hardeners, corrosion inhibitors and textiles has been carried out. In contrast, the survey of the use of chromium as an alloy metal in connection with iron, aluminium and copper as well as in electronic storage media has been carried out at a general level. Special emphasis has been placed on identifying consumption and diffusion of chromium(VI) compounds (hexavalent chromium).

The balance presented covers imports, production and exports for the year 1999, calculated as an average for the years 1998, 1999 and 2000. In cases where discrepancies between data from the three years were observed, the most probable data were included in the calculations.

Occurrence and production of chromium and chromium compounds

Chromium occurs naturally as red lead ore (PbCrO₄, crocoite) and as chromium ironstone (FeO, Cr₂O₃). Metallic chromium is produced by reducing chromium oxide (Cr₂O₃) with aluminium. Chromium deposits are found in countries such as South Africa, Kazakhstan, India, Brazil, Finland, Turkey and Zimbabwe. These countries account for more than 90% of the total production. Metallic chromium is used as an alloy metal in iron, aluminium and copper and for surface treatment. The Danish Product Register includes records of approximately 130 chromium compounds, and chromium(III) oxide, chromium(VI) oxide, metallic chromium and lead(II) chromates account for more than 95% of the total registered consumption. No production of chromium compounds takes place in Denmark.

Chromium balance for Denmark

Figure 1 shows a simplified chromium balance for Denmark. The balance is described and discussed in section 6.3, "Chromium balance for Denmark 1998–2000".

Figure 1
Chromium balance for Denmark 1999

Chromium is imported in metallic form with iron and iron alloys, aluminium and aluminium alloys as well as copper and copper alloys. Chromium also occurs as an impurity in these metals. Chromium is exported as metal scrap; such export is carried out with a view to recycling.

Chromium compounds are imported with a view to production of finished goods in Denmark, and as ingredients in finished goods. In most products, the chromium content is not sufficiently high to warrant labelling or any other special attention. As a result, we do not have a great deal of knowledge about which products contain chromium compounds, nor about the relevant contents of chromium compounds in those products.

Below is a summary of the consumption of finished goods containing chromium and of emissions into the environment.

Consumption

Consumption of chromium as an alloy metal, chemical compounds and as a trace constituent has been analysed for Denmark for 1999 (average for the years 1998, 1999 and 2000).

Table 1 shows an overview of the consumption of chromium and chromium compounds in Denmark, by field of application. The survey of different fields of application has been carried out at different levels of detail as described in section 1.4, "Prioritisation of the survey". The survey was carried out on the basis of information from Statistics Denmark, the Danish Product Register, previous mass flow analyses, and information provided by selected trade associations, importers and manufacturers.

Table 1
Consumption of chromium, chromium compounds and chromium as a trace constituent in Denmark in 1999 (average for the years 1998, 1999 and 2000), by field of application. Figures on the consumption of Cr(VI) are also provided for relevant applications.

In the survey of the consumption of chromium compounds, emphasis has been placed on identifying consumption and emissions of chromium(VI) compounds, as they represent a significantly greater risk to the environment and health than other chromium compounds. The use of chromium(VI) compounds is subject to a number of restrictions, which explains the drop in consumption within some fields of application.

Chromium, metallic

Metallic chromium mainly occurs as an impurity and alloy metal in iron, aluminium and copper. This is also the reason why the survey of metallic chromium is primarily based on updates of previous mass flow analyses of these substances. This particular field of application accounts for more than 97% of the total consumption of chromium in Denmark. Metallic chromium is also used as a coating/surface treatment, for example, for metals and plastic in the form of chromium plating. The actual process is described under the section on chromium compounds below. Metallic chromium in iron, aluminium and copper is recycled. A substantial part of all recycled metallic chromium is exported in the form of alloy steel sent for recycling.

Chromium compounds

Chromium compounds are used in a wide variety of products, e.g. for surface treatment, colour pigments, leather tanning, wood impregnation, textiles, etc. Chromium compounds are no longer used in wood preservatives, but because of the long lifetime of such products, disposal of impregnated wood will be a source of chromium in waste flows for many years to come. Chromium compounds are not recycled as such.

Chromium as a trace constituent

Chromium occurs as a trace constituent in considerable amounts in cement and fossil fuels (primarily in coal). Recycling of residual products (fly ash) in cement contributes to chromium content in cement, as do other raw materials.

Emissions to the environment

Table 2 contains an overview of the information available about disposal and emissions of chromium into the environment in Denmark in 1999. Emissions to various recipients are discussed below.

Emissions to air

Chromium and chromium compounds are stable compounds with a high melting point/boiling point. This means that emissions to air are mainly associated with thermal processes. Thermal processes occur in connection with waste incineration, energy conversion, and production and reprocessing of iron, aluminium and copper, including alloying of these metals. Primary production of these metals or alloys does not take place in Denmark, but reprocessing might well do so, as might recycling of metals. Energy conversion is regarded as the most important general source of emissions of chromium to air.

Discharges to water

Discharges of chromium and chromium compounds into the aquatic environment occur, for example, through the discharge of process chemicals from surface treatment processes or wastewater from the paint/varnish industry. During the use phase, discharges to water will primarily take place through corrosion of iron, steel, aluminium and copper, through use of paints containing chromium pigments, through leaching from impregnated wood or through disposal of laboratory chemicals. The greatest secondary sources of chromium discharges into water are emissions via atmospheric deposition and/or discharges from municipal wastewater treatment plants.

Emissions to soil

During the use phase, emissions of chromium and chromium compounds will primarily take the form of corrosion of iron, steel, aluminium and copper, leaching from impregnated wood and painted surfaces as well as peelings from chromium-plated products. The largest secondary sources of chromium emissions to soil are via atmospheric deposition and/or sludge from municipal wastewater treatment plants.

Landfill

Chromium and chromium compounds end up in landfill as part of a range of products. It is estimated that the most significant sources are iron and stainless steel, and residual products from waste incineration. Furthermore, smaller amounts are added to landfill with construction waste, leather and textiles.

Table 2
Disposal and dispersal of chromium to the environment in Denmark, 1999

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Summarizing evaluation

The total consumption of chromium is calculated at 25,000–30,000 tonnes/year, of which metallic chromium accounts for more than 97%. Chromium compounds and trace constituents account for the remainder. Chromium(VI) compounds are estimated to account for 50–53 tonnes per year. It is estimated that the consumption of chromium(VI) compounds will fall as a result of the restrictions on their use. Metallic chromium in waste is recycled extensively with iron, aluminium and copper, while there is no recycling of chromium compounds.

The most substantial emissions to air come from energy conversion processes, while the most substantial contributions to the water environment come from atmospheric deposition. The most substantial emissions to soil come from atmospheric deposition and reprocessing as well as use and disposal of iron and steel.

1 Introduction

1.1 Objective of the analysis

Due to the health risks associated with chromium(VI) compounds (hexavalent chromium), efforts have been made to identify all flows of this substance.

1.2 Method and scope

A mass flow analysis is based on the principle of substance balance over a given period of time. This principle states that:

Input + formation = accumulation + output + degradation

Chromium is an element, which means that it will neither form nor be degraded. As a result, the mass flow is simple: the quantities entering the community (input) equal the sum of the quantities leaving the community (output) and the accumulated mass. See Figure 1.1.

Figure 1.1
The principle of mass flow analysis

The survey of the mass flow for chromium is based on statistics from Statistics Denmark about imports and exports (Statistics Denmark, 1999a; 2000a; 2001a) and sales of domestically produced goods in Denmark for 1998–2000 (Statistics Denmark, 1999b; 2000b; 2001b). This information has been supplemented with information from the Product Register about the supply and composition of products containing chromium and their use within various functions. Among other things, the information from the Product Register is used to identify CN¹ numbers for chromium and products containing chromium for which Statistics Denmark has compiled figures on import, export and production. Efforts have been made to confirm the statistic information by contacting relevant industry organisations, companies and the like.

The mass flow analysis looks at the flows of chromium and chromium compounds in Denmark during a single year. In order to take fluctuations in sales into account, average figures from Statistics Denmark have been used. These average figures are for import, export and sale of domestically-produced goods in Denmark in the years 1998, 1999 and 2000. More years have also been included in the analysis in order to determine development trends as regards the use of chromium.

When we look at the data basis from Statistics Denmark, we see examples of significant variations in the sales of goods between the years 1998–1999 and 2000. One of the reasons for this is that in 2000, Statistics Denmark made an extra effort to have companies report quantities which they had not previously felt able to report information on (Statistics Denmark, 2002).

This means that 2000 may be a more accurate reference year than the preceding ones, as reports on quantities of chromium and chromium compounds have been made for more items in 2000 than ever before. On the other hand, the reports on these hitherto unreported quantities may not be entirely accurate. This uncertainty has to do with the fact that they cannot be compared with previous reports, and the people supplying the new information may not be used to doing so, and may make mistakes as a result of their lack of experience.

If, for example, we look at item no. 74122000, "Pipe fittings made from copper alloys", the statistics tell us that a total of 54,325 tonnes of this product were sold in Denmark in 2000. This seems unlikely, as it would mean that every citizen in Denmark bought approximately 10 kg of pipe fittings. One explanation for this mistake might be that the report has been made using the wrong unit, e.g. "pieces" instead of "tonnes". In cases where the quantities stated for a year (primarily 2000) appear obviously unrealistic, the year in question has been disregarded in the calculations of the average quantities for 1998–2000².

1.3 Chromium and chromium compounds

1.3.1 Occurrence and use of chromium

Chrome is a shiny, very hard and brittle metal. It belongs to the group of heavy metals and is the 13^th most common element on Earth. It occurs in nature as red lead ore (PbCrO₄, crocoite) and as chromium ironstone (FeO, Cr₂O₃). Metallic chromium can be produced by reducing chromium(III) oxide (Cr₂O₃) with aluminium.

Chromium is used in many contexts, either in metallic form or in chemical compounds. The Danish Product Register includes records of approximately 130 chromium compounds, and chromium(III) oxide, chromium (VI) oxide, metallic chromium and lead(II) chromates account for more than 95% of the total consumption if we take a worst case scenario view³.

As metallic chromium is very chemically stable, it is often used to cover the surface of less durable metals. This is known as chromium plating. Chromium is also widely used as an ingredient in metallic alloys. Among other things, it is used in ferrous chromium, a carboniferous 60% chromium-iron alloy, in chromium steel with 12–13% chromium, in 18/8 steel (18% chromium and 8% nickel), and in particularly heat-resistant special steel (25–30% chromium and up to 15% nickel).

Among other things, chromium compounds are used as pigments in paints, printing colours, artists' colours, and similar products. Particularly popular are lead chromate and zinc chromate – both of them yellow – and the greenish chromium oxide. Tanning of leather involves chromium in the form of chrome alum, a double salt consisting of potassium sulphate and chromium sulphate. Within the chemical industry, the reactive chromium(VI) is used as an oxidising agent, particularly in the form of chromic sulphuric acid (potassium dichromate and concentrated sulphuric acid) and in catalysts.

1.3.2 Physical/chemical characteristics

The environmental and health-related characteristics of chromium and chromium compounds depend on the relevant oxidation level. As a result, a brief description of the electrochemical characteristics of chromium in the environment is given. The most significant physical-chemical characteristics of chromium and a number of inorganic chromium compounds are presented in tables 1.1 and 1.2.

Table 1.1
Physical-chemical characteristics for chromium and selected inorganic chromium compounds

Table 1.2
Physical-chemical characteristics for chromium and selected inorganic chromium compounds

1) Alkaline lead chromate (18454-12–1; 1344-38-3) also occurs.

1.3.3 Electro-chemicals characteristics

Chromium occurs within the oxidation levels 3, 6 and 2, listed in order of decreasing stability. Cr(VI) can be reduced to Cr(III) by Fe(II). In all likelihood, soluble Cr(III) complexes are formed with the organic ligands. Similarly, Cr(VI) is reduced in soil with high humus contents and in connection with microbial activity.

The conditions for reduction of Cr(VI) are not good in surface water, in sea water, in aerobic soil and in sediment. Cr(VI) will, however, often be mobile. As a result, it may reach anaerobic areas (such as lower layers of sediment) where reduction can occur.

It is not very likely that oxidation of Cr(III) to Cr (VI) will occur in nature. Oxidation is only to be expected under aerobic conditions and when MnO₂ is present.

At pH< 1, Cr(VI) will appear as H₂CrO₄; at 2< pH <6 it will appear as an equilibrium between HCrO₄ and Cr₂O₇^2–, and at pH>7 it will appear as CrO₄^2–. Similarly, in acid liquids Cr(III) will appear as Cr³⁺, Cr(OH)²⁺, Cr(OH)₂⁺, Cr(OH)₃ and Cr(OH)₄^– as pH values increase. At pH>5, however, Cr(III) is deposited as Cr(OH)₃, even though complex formation with organic ligands may compete with this process, thereby increasing solubility. Chromium compounds are not volatile. In the atmosphere, they will mainly occur in association with aerosols and particles.

1.3.4 Classification of chromium compounds

The classification of chromium compounds on the basis of their inherent characteristics is of great significance to the use – and limitations on use – of the substances in question. Table 1.3 shows the classifications of the most frequently used chromium compounds.

Table 1.3
Classification of the most frequently used types of chromium and chromium compounds

Due to their classification as carcinogenic and mutagenic, chromium(VI) oxide, lead(II) chromate and the other chromates are all subject to a number of limitations on sale and use (The Danish Ministry of the Environment, 2000). The substances are not available in retail shops and may only be sold to buyers who submit requisitions in accordance with specific rules. Limitations have been introduced for the use of products which contain hexavalent chromium compounds. These limitations include a requirement for notification of the Danish institute for occupational safety and health, the National Working Environment Authority (the Ministry of the Environment, 1997). The limit value for chromic acids and chromates in the working environment is 0.005 mg/m³. (National Working Environment Authority, 2000).

1.4 Prioritisation of the survey

1.4.1 Hazardousness and potential exposure

Chromium primarily occurs as metallic chromium and as chromium compounds, where chromium has an oxidation level of 3 or 6. The toxicological and eco-toxicological properties of chromium depend on the chemical combinations in question. Due to their high bio-availability and highly oxidising properties, Cr(VI) compounds are far more toxic to biological systems than Cr(III) compounds. This means that Cr(VI) compounds are far more hazardous than Cr(III) compounds (EU, 2000a). Generally speaking, metallic chromium is not available for absorption in organisms in nature and is generally held to present little hazard and little potential for exposure.

The risk of being exposed to chromium is particularly high for people working in industries where chemicals containing chromium are used. Cigarette smokers are also at risk⁴. For most people, however, food will be the greatest source of chromium intake (ATSDR, 2000). Occurrences of chromium in products can, however, lead to direct human exposure which is not work-related. Examples include chromium in dust from brake linings and cement dust. People working with wastewater from chromium-plating industries, tanning, textile industries and waste containing chromium also risk exposure. Chromium might occur in drinking water as the result of pipes made from alloys containing chromium in the supply system; this does not, however, seem likely, as such chromium alloys are very stable. Contamination from landfills is another possible source of chromium in drinking water. Finally, exposure to chromium may occur due to incineration of products which contain chromium, e.g. impregnated wood and fossil fuels (ATSDR, 2000).

As was the case for human exposure, the main source of potential environmental problems is exposure to Cr(VI) due to the toxic effects and high bio-availability of this substance. Cr(VI) is relatively stable in water, a fact which increases the risk of critical exposure. It is estimated that the aquatic environment is mainly subjected to exposure through wastewater from companies using chemicals which contain chromium, but household wastewater and atmospheric deposition can also be sources of exposure. Alloys containing chromium are not expected to cause significant exposure as far as the aquatic environment is concerned, as the chromium is firmly bound in these alloys. Small amounts of chromium may be released into the aquatic environment in connection with oxidation of steel alloys in water (rust).

Significant chromium exposure must be expected for organisms in soil due to leaching of chromium from impregnated wood, waste deposits/landfills and spills of chemicals containing chromium. Atmospheric deposition and wastewater sludge will also give rise to more diffuse exposure. It is expected that Cr(VI) in soil is rapidly reduced to Cr(III), and this reduces the risk of impacts (EU, 2000a). As was the case for the aquatic environment, release of chromium from alloys is held to be of little significance in terms of soil exposure.

To sum up, chromium exposure from alloys which contain chromium is regarded as unproblematic for human beings and the environment. It is estimated that environmental exposure mainly comes from impregnated wood and wastewater from industries using chemicals which contain chromium, as well as from disposal in the form of incineration and landfilling.

1.4.2 Chromium supply via goods and products

Based on the information about use of chromium and chromium compounds appearing in various materials and products, the list of CN numbers (the Combined Nomenclature, Statistics Denmark) has been studied with a view to identifying product groups which may contain chromium.

Information on import, export and production has been obtained for the selected CN numbers. This information covers the years 1998, 1999 and 2000.

As far as possible, "tonnes" have been used as the preferred unit when collecting information on product quantities. For some product groups, however, Danish production is measured in other units (pieces or m²). In such cases, the figures for production in tonnes are estimated on the basis of the assumption that values per weight unit are the same for goods manufactured in Denmark as for exported/imported goods. This approach could not be used with a few product groups. In those cases, weight per unit or m² has been estimated on the basis of actual testing and weighing or studies of the available literature. Worst-case scenarios were applied in all cases to make sure that chromium contributions from the relevant product groups were not underestimated.

The results of the preliminary data processing are presented as the supply of chromium within product groups (Table 1.4). The table also states the oxidation level for chromium within the various product groups and provides estimates of the potential exposure and hazardousness.

Table 1.4
Supply of chromium within product groups, oxidation levels (stated as 0, II or VI) and estimates of the potential exposure and hazardousness (ranked as L for Low, M for Medium or H for High).

1) Chromium-plated iron and steel products are included in this product group
2) Preliminary calculation of the chromium supply in Denmark

The results of the preliminary data processing indicate that chromium in alloys is the most significant category: iron and steel, copper, aluminium and goods made from these metals. Next in line is chromium in the form of chemical compounds: accelerators etc., pigments and chromium compounds. The ranking of specific products indicates that special attention should be paid to stainless steel sheets (>600 mm>), pipes and hollow profiles, tanks, vats and similar containers, products made by means of hot rolling, wire mesh, and copper and copper products.

1.4.2.2 The Product Register

Three different searches of the Product Register were made:

1. A search for substances containing chromium
2. A search for import, export and production of substances containing chromium (inventory as at 1999, 2000 and 2001⁵); the supply was calculated and minimum and maximum values have been given
3. A search for the contents of specific chromium compounds in specific goods/functions

The first part of the search resulted in a list of approximately 900 names of substances which contain chromium. The second part of the search revealed that notification of use has been submitted for approximately 130 of these substances. Statistics on the supply of the 130 substances in question have been converted into a value for chromium supply, based on maximum chromium content in the relevant compounds. Thus, the figure for chromium supply through chromium compounds represents the maximum quantities possible according to the information in the Product Register. Table 1.5 illustrates the supply for the 15 chromium compounds accounting for the greatest supply, ranked in order of the quantities supplied. We see that chromium(III) oxide, chromium(VI) oxide, chromium, "not specified"⁶ and lead(II) chromate account for more than 95% of the chromium supply registered in the Product Register.

Table 1.5
Supply of the 15 chromium compounds accounting for the greatest supply in Denmark, calculated as an average of the supply during the period 1998–2000. The figures are based on statistics from the Product Register and reflect the maximum possible content.

The grey areas have been blanked out due to confidentiality. This is to say that they have been reported within less than 3 functions.

These are followed by a number of less frequently seen hexavalent chromium compounds: potassium dichromate (0.51 tonnes of chromium), zinc chromate (0.35 tonnes of chromium), sodium dichromate dihydrate (0.17 tonnes of chromium) strontium chromate (0.13 tonnes of chromium), ammonia dichromate (0.12 tonnes chromium), and more.

1.4.3 Summary

The survey has been prioritised as illustrated in Table 1.6. This prioritisation is based on the discussion on hazardousness and exposure outlined above, as well as on information from Statistics Denmark and the Product Register.

Table 1.6
Survey priorities

Electronics and glass are examples of product groups which were not accorded high priority on the basis of the initial survey. It may be relevant to include these product groups in connection with any subsequent studies.

1.5 International market and development trends

According to information from the international industry association for chromium (International Chromium Developing Association – ICDA), approximately twenty countries in the world extract chromium today. Of these, South Africa accounts for almost half of all the chromium extracted (47%), Kazakhstan accounts for 18%, and India accounts for 13%. The total extraction carried out in Brazil, Finland, Turkey and Zimbabwe amounts to 16%, and a total of 12 other countries account for the remaining 6%. In total, approximately 15 million tonnes of chrome iron ore were extracted in 2000 (ICDA, 2002).

According to the ICDA, chromium consumption worldwide is distributed as follows: 85% of all chromium is used within the metal industry, 8% is used within the chemical industry, and 7% is used for fireproof products and foundries.

2 Chromium use in Denmark

2.1 Iron and steel

Chromium is used as an alloy metal in ferrous chromium, a metal which contains very large amounts of chromium. It is also used in iron and various types of steel, primarily stainless steel. The use of metallic chromium in Denmark has been determined on the basis of information from Statistics Denmark on the registered foreign trade in Denmark and the registered sales in Denmark of products of Danish manufacture. The consumption of metallic chromium in industrial products has been determined on the basis of supply information from the Statistics Bank provided by Statistics Denmark. This information was divided into so-called Broad Economic Categories (BEC).⁷ The information from the Statistics Bank has been compared with information about stainless steel contents in various product types (The Danish EPA's Product Database). All figures are for the period 1998–2000. Table 2.1 shows the supply of metallic chromium on the basis of production, import and export of finished goods, raw materials and semi-finished goods made from iron, steel and ferrous chromium.

2.1.1 Products and semi-finished goods made from iron and steel

Ferrous chromium is a chromium-iron alloy with a chromium content of 60–65%. It is produced by reducing chrome iron ore with coke and/or silicon at high temperatures in furnaces. This alloy is primarily used in the manufacture of stainless steel, a process accounting for up to 90% of the total consumption of ferrous chromium.

The designation stainless steel covers a wide variety of alloys, including chromium steel (which contains 12–13% chromium), the widely used austenitic steel or 18/8 steel (18% chromium and 8% nickel), and particularly heat-resistant special steel containing 25–30% chromium and up to 15% nickel. Austenitic steel accounts for 70–90% of the stainless steel used in Denmark (Sandvik Steel Denmark, 2002; Avesta Polarit, 2002; Aco-drain, 2002).

As stainless steel contains relatively large quantities of chromium, certain significant product groups containing stainless steel have been included in the calculations of the metallic chromium supply in Denmark. Large portions of the finished goods which contain steel are included in calculations along with many other materials. As a result, the estimated flows in and out of Denmark are subject to considerable uncertainty.

The designation alloyed steel covers hundreds of steel types where steel is alloyed with other metals. The main reason for alloying steel is a desire for greater hardness and strength. Many types of alloyed steel contain chromium, but the relative quantities vary from 0.1% to 12.5%. A US study sets the chromium contents in the steel alloys used at 0.68+0.11% (US Bureau of Mines, 1994). It has not been possible to confirm this figure with people within the iron and steel industry in Denmark. The reason was that none of the people asked felt able to offer an estimate for the average chromium content in alloyed steel due to the many types of alloys found in the market. As the information from Statistics Denmark on import, export and production of alloyed steel does not provide any details about the types of alloyed steel found within the individual product groups, we have chosen to apply an average chromium content of 0.5–0.8% in alloyed steel.

The group of iron and unalloyed steel which is chromium-plated comprises products which are coated with a layer of chromium.

Iron and unalloyed steel contains chromium as an impurity. It is estimated that the chromium content due to such impurities is in the region of 0.05%. (Det Danske Stålvalseværk, 2002a/b).

Table 2.1
Import, export and Danish production of goods, raw materials and semi-finished goods

Stainless steel is not produced in Denmark. Scrap stainless steel is exported in order to be used as a raw material once again. According to Avesta Polarit (2002), the total production of new stainless steel is made up of 95% recycled steel and 5 % new raw iron.

Det Danske Stålvalseværk was the only manufacturer of steel in Denmark. Approximately 75% of the total quantities produced there were used for export (Det Danske Stålvalseværk, 2001). This steel was made from 90% scrap steel and 10% new raw iron (Det Danske Stålvalseværk, 2002a). The scrap steel primarily comes from Danish scrap merchants, whereas the raw iron comes from Russia and Poland. A total of 20% of the steel used in Denmark comes from the Stålvalseværk, while the rest is imported (Det Danske Stålvalseværk, 2002a; Stålforeningen, 2002).

Scrap metal and iron ore only contains small quantities of chromium – around 0.01% (Kjeldgaard, 1991). Naturally, this chromium will reappear in the steel materials made. Suppliers of scrap steel are good at sorting out scrap made from alloyed steel and cast steel, as these types of steel attract higher prices. This means that the chromium content in the steel produced remains low. As the steel is manufactured, it is monitored for levels of chromium and other substances. If the chromium levels are too high, the steel is diluted by means of additional raw iron (Det Danske Stålvalseværk, 2002a). During the production process, ferrous chromium is added to harden the steel. In 2001, for example, ferrous chromium was added in quantities corresponding to approximately 580 tonnes of pure chromium. Chromium sand is also used to transport the finished steel out of the furnaces. In 2001, a total of 170 tonnes of chromium sand was used, corresponding to approximately 16 tonnes of pure chromium (Det Danske Stålvalseværk, 2002b).

In 2001, Det Danske Stålvalseværk produced approximately 750,000 tones of raw steel. Approximately 665,000 tonnes were used for steel products (Det Danske Stålvalseværk, 2002b). Table 2.2 presents the mass balance for heavy metals in general and specifically for chromium per tonne of raw steel in connection with steel production.

Table 2.2
Mass balance for chromium and heavy metals in general in connection with production of 1 tonne of raw steel (calculated on the basis of Det Danske Stålvalseværk, 2001; 2002b)

This means that production of 750,000 tonnes of raw steel entails disposal / deposit of 2.25 tonnes of chromium. Table 2.3 shows the discharges of chromium into water associated with production of sheets and bars, respectively, at Det Danske Stålvalseværk.

Table 2.3
Discharges of heavy metals into water associated with production of steel at Det Danske Stålvalseværk (Det Danske Stålvalseværk, 2001)

In 2000, a total of 326,000 tonnes of steel sheets and 223,000 tonnes of bar steel was produced. This corresponds to discharges of heavy metals into water in the region of 0.34 tonnes per year. We do not know the exact quantities of chromium involved, but on the basis of the information in Table 2.2 it is estimated that chromium accounts for between 5 and 10% of all the heavy metals. This corresponds to discharges of between 0.017 and 0.034 tonnes chromium each year. The chromium content of the landfill at Det Danske Stålvalseværk has not been assessed.

If the same assumption is applied to a calculation of chromium emissions to air, we arrive at the following figure: emissions of 0.12–0.24 g per tonne raw steel or 0.09–0.18 tonnes chromium per year from production at Det Danske Stålvalseværk.

2.2 Aluminium

Metallic aluminium may contain small amounts of chromium, mainly in the form of impurities. In the Combined Nomenclature (CN), metallic aluminium is divided into unalloyed and alloyed aluminium, and these categories are divided into five product groups: bars, profiles, wire, sheets/strip/foil and pipes. In the CN, one of the characteristics of unalloyed aluminium is that is has a limit value of 0.1 per cent (by weight) for ingredients other than aluminium. Naturally, this includes chromium. Alloys of aluminium are defined by having greater contents of other ingredients than unalloyed aluminium.

A life cycle analysis of chromium carried out on behalf of US authorities included calculations of the chromium contents in aluminium (US Bureau of Mines, 1994). The study used two methods to calculate the average chromium content of aluminium in general. One of these methods used an average of the chromium contents in aluminium alloys, categorised by alloy class, and this yielded a result of 0.02–0.06% chromium. The other method was based on the average chromium content in the aluminium alloys actually used. The result of this method was 0.13–0.21% chromium. It is, however, believed that the latter method results in too high a chromium content, as it only includes types of aluminium for which the chromium contents have been specified.

Based on the chromium contents in aluminium mentioned above, it is assumed that the chromium contents for unalloyed and alloyed aluminium as a whole are between 0.02% and 0.1%.

Table 2.4 shows information from Statistics Denmark about import, export, production and supply of aluminium for the years 1998–2000. This information is listed by CN nos. in Appendix B.

Table 2.4
Import, export and production of raw materials and semi-finished goods made from metallic aluminium (Statistics Denmark, 2001b)

In a mass flow analysis made for aluminium for 1994, the supply of raw materials and semi-finished goods made from metallic aluminium and aluminium alloys is calculated to be 140,095 tonnes (Hansen et al., 1999). Compared to the supply for 1994, the average supply for 1998–2000 is approximately 20% higher. This is consistent with the fact that there has been a general increase in the use of aluminium (the Secretariat for Aluminium and Environment, 2002).

Table 2.5 shows the mass balance for aluminium in Denmark as an average of 1998–2000. The figures have been rounded up. This mass balance was established on the basis of an assumption that the aluminium balance has remained unchanged in 1998–2000 compared to 1994. This assumption is subject to some uncertainty, but is deemed to be acceptable. This is because the contribution from aluminium to the mass flow of chromium in Denmark is of minor significance compared to other sources of chromium, partly due to the amounts involved, and partly because the chromium involved is metallic-bound chromium which will not appear as hexavalent chromium if it enters the environment. In order to counteract the uncertainty associated with extrapolating current values on the basis of 1994 figures, the interval quantities include the 1994 situation and a 20% increase in quantities.

Table 2.5
Mass balance for aluminium in Denmark 1998–2000 (Statistics Denmark, 2001b; Hansen et al., 1999)

2.3 Copper

Like aluminium, metallic copper contains certain amounts of chromium. In the Combined Nomenclature (CN), copper is divided into the following eight product groups: refined copper; copper alloys; master alloys; bars and rods; profiles, wire; plates/sheets/strip/foil; and tubes and pipes. The contents of copper within the product groups vary from approximately 12% for copper foil to 99.9%, for example, for refined copper pipes.

In the Combined Nomenclature, refined copper is characterised by having a limit value for chromium of 1.4% by weight, whereas copper alloys and master alloys may have higher chromium contents. The chromium contents are not described in any more detail for the rest of the product groups.

The chromium content of copper has been calculated in the US authorities' life cycle analysis (US Bureau of Mines, 1994). These calculations are partly based on the average chromium contents of copper alloys based on alloy classes. They are also based on the average chromium content of the actual quantities consumed of copper alloys with specific chromium contents. In both cases, the result of the calculations was chromium contents of 0.024–0.026%.

As it has not been possible to distinguish between different types of copper, it has been assumed that refined copper and copper alloys in general have a chromium content of 0.024–0.026%.

The table below shows statistics on the import, export and production of raw materials and semi-finished goods made from metallic copper. This information is given by CN nos. in Appendix C.

Table 2.6
Import, export and production of raw materials and semi-finished goods made from metallic copper (Statistics Denmark, 2001b)

In a mass flow analysis for copper made for the year 1992, the supply of raw materials and semi-finished goods made from metallic copper is given as being in the region of 39,400–40,100 tonnes (Lassen et al., 1996). Compared to the figures for 1998–2000, this is consistent with the information for 1998 and 1999, whereas a very significant deviation can be seen for the year 2000. This deviation concerns the value of production. As a result, the values for 2000 will not be used. This means that the average value is based solely on the values for 1998 and 1999.

Table 2.7 below shows the mass balance for copper in Denmark. The figures are rounded up and constitute an average of 1998 and 1999 values. The mass balance has been established on the basis of an assumption that the copper balance has remained unchanged in 1998–1999 in relation to 1992. Such an assumption entails a certain level of uncertainty, but is deemed to be acceptable as the supply of copper in society in general has remained unchanged. In addition to this, the contribution made by copper to the mass flow of chromium in Denmark is of minor significance compared to other sources of chromium, partly due to the amounts involved, and partly because the chromium involved is metallic-bound chromium which will not appear as hexavalent chromium if it enters the environment.

Table 2.7
Mass balance for copper in Denmark 1998–1999 (Statistics Denmark, 2001b; Lassen et al., 1996)

2.4 Summary

Chromium occurs as an alloy metal and as an impurity in iron, aluminium and copper. Table 2.8 shows the consumption and dissemination of chromium in connection with use of iron and steel, aluminium and copper in Denmark. This calculation is based on a general calculation of the consumption of iron and steel and an update of previous mass flow analyses made for aluminium (Hansen et al., 1999) and for chromium (Lassen et al., 1996).

Table 2.8

Look here!

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