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Mass Flow Analyses of Mercury 2001

4 Overall assessment

4.1 Applications and consumption in Denmark
4.2 Releases to the environment in Denmark
4.3 Mercury balance for Denmark

4.1 Applications and consumption in Denmark

The available information and estimates of mercury consumption in Denmark, 2001, are summarised in Table 4.1.

Table 4.1 Mercury consumption in Denmark, 2001

1) In the summation, mercury in fly ash was subtracted, as this ash is used in cement production and thus occurs twice in the table.

As is apparent from Tables 4.1 and 4.2, the current consumption of mercury can be estimated as follows:

Thus, intentional uses are responsible for about half of the total consumption, of which dental fillings alone account for 1/3. For the sake of comparison, Table 4.2 also shows the consumption in 1992-93 and 1982-83.

Development trends, consumption

Table 4.2 Mercury consumption in Denmark for 1982-83, 1992-93 and 2001

There has been a sharp drop in the consumption of mercury over the past 20 years, see Table 4.3.

Table 4.3 Trend in average mercury consumption in Denmark since 1982/83

Despite the drop in consumption in most of the intentional uses, it is worth noting that, logically enough, applications in which consumption was high in earlier years, and which are strictly regulated at the national and international levels, have become more peripheral. Instead, applications are now gaining prominence that have not been exposed to the same regulatory pressure, and perhaps for this reason have not been developed to the same extent in recent decades. This still applies, for instance, to dental fillings, to button cells of types other than mercuric oxide and to light sources.

It is also worth noting that the mobilisation and release of mercury as a trace element in coal is still falling, primarily because of the endeavour to shift energy production away from coal in Denmark in order to reduce the emission of carbon dioxide and a number of other pollutants.

Mercury as an impurity in “All other goods” was assessed as being low in 1982-83. This is because a different assessment method was used at that time and it is therefore not an expression of a trend. There is no basis for expecting any real difference between 1982-83 and the other years. The large interval reflects the fact that, in all cases, this type of consumption can only be estimated with considerable uncertainty.

4.2 Releases to the environment in Denmark

The available information and assessments of releases of mercury to the environment in Denmark are summarised in Table 4.4. As can be seen from the table, total releases in 2001 can be estimated at:

In addition, about 2,700-4,400 kg/year is deposited, e.g., in roads, dams, and other structures in which residual products of waste incineration and coal combustion are used.

Emissions to air
The main causes of emissions to air are:

The remaining emissions are chiefly due to cement production, other forms of waste management and cremations. It should be noted that industrial processes only appear to be responsible for about 9% of all emissions in Denmark.

In addition, it should be noted that the mercury content of combustible waste must primarily be attributed to mercury as an impurity (about 30%), batteries (about 22%) and switches, contacts and relays (about 18%), cf. Table 3.4. The contribution from batteries, switches, contacts and relays must to a considerable extent be assumed to depend on earlier consumption, which is only slowly disposed of before it finally ends in waste.

Emissions of mercury to air have dropped to about 1/4 of the level of 1982-83. This is particularly due to a drop in the emissions from waste incineration, which again is due to improved flue gas cleaning. Emissions in 2001 amounted to less than 2/3 of those in 1992-93. This drop is linked to a drop in emissions from the production of iron and steel, from coal combustion and from the disposal of light sources.

Discharges to water
Discharges to water are primarily dependent on the mercury in wastewater, which chiefly consists of mercury from dental clinics (more than 60%), but also, e.g., from thermometers and monitoring equipment, cf. Table 3.8.

Discharges to water have fallen to about 18% of the 1982-83 level, but remain at the 1992-93 level - or perhaps a little higher. The latter conceals the fact that discharges to the marine environment from offshore oil and gas extraction are included in the account for 2001.

Releases to soil
Releases of mercury to soil mainly depend on:

Releases to soil remain at the level of the previous mass flow analysis, but are significantly lower than losses to soil in 1982-83; this change is due to the fact that the practice of dressing seed corn has been discontinued.

Releases to deposition
The greater part (80%) of the mercury deposited comes from the residual products of waste incineration.

The deposition in landfills of mercury has increased since the earlier accounts. This is related to the efficiency of flue gas cleaning, which to some extent removes mercury from smoke, so that emissions to air are reduced, although the mercury is still to be found in the residual products of waste incineration; at the same time, the quantity of waste that is incinerated has increased. By far the greater part of the residual products of waste incineration is deposited outside Denmark (in Norway and Germany).

Total release
Thus, the total release of mercury only shows a small drop since the previous mass flow analysis. The uncertainty interval has however increased, especially because of the uncertainty concerning mercury in residual products, which constitutes the greatest loss of mercury to the environment.

Uncertainty
This account of the disposal and losses of mercury is to some extent based on estimates with inherent uncertainties, which will always be open to discussion.

The quantities estimated to have been sent to waste incinerator plants appear to be too low in relation to the recorded quantities. This could be related to the fact that the mercury content of products is falling sharply. This makes estimation of the disposal and loss quantities extremely sensitive to the life-cycles and "box-room" effect applied in calculations involving mercury-containing products. The box-room effect is an expression of the fact that, when products are worn out they are stored by consumers for some period before they are disposed of. On the basis of the available information, it is not possible to determine whether the input sources have in fact been underestimated or whether it is a question of general uncertainty in the calculations.

Bearing this reservation in mind, the accuracy of the estimated disposal and loss quantities can in summary be characterised by the fact that the orders of magnitude of the stated quantities can be considered reliable.

Table 4.4 Releases of mercury to the environment in Denmark, 2001

1) The stated quantities are discharged to wastewater where, after treatment in sewage treatment plants, the mercury will end in the sludge and water discharged by the plant. These quantities are therefore included under "Discharged from municipal sewage treatment plants" and "Wastewater sludge," and are not included again under "Total."

2) Deposited abroad.

3) Included in "Deposition (excl. residual products of incineration)."

4) See Table 3.4.

Releases to deposition and air from waste incinerator plants are primarily due to dental amalgam, batteries, light sources and switches, contacts and relays.

Table 4.5 Releases of mercury to the environment in Denmark, 1992-93

1) The stated quantities are already included under "Discharged from municipal sewage treatment plants" and "Wastewater sludge."

2) The stated quantities are only summated in the event that they are not included under other headings.

3) The stated quantities are already included under "Deposition (excl. residual products)" and are therefore not included under "Deposition, total".

Table 4.6 Releases of mercury to the environment in Denmark, 1982-83

1) The stated quantities are included under municipal wastewater.

2) Partly counted under municipal wastewater.

4.3 Mercury balance for Denmark

The available information and estimates of the consumption and losses of mercury to the environment in Denmark are illustrated in Fig. 4.1. Concerning the figure, the following should be born in mind:

The net importation of mercury is not known precisely, but is estimated on the basis of the available calculation of the consumption of mercury in Denmark.

In contrast to the previous mass flow analysis, no significant exports of mercury-containing products have been found. Exports during 1992-93 included 600-700 kg of mercury, which included batteries, thermometers, and flashing lights for controlling rail traffic. Danish battery manufacturers only produce alkaline batteries that are not button cells. The mercury content of such batteries amounts to a maximum of 15 kg (see Section 2.3.1). Mercury-containing thermometers are no longer manufactured in Denmark. Danish consumption of mercury in flashing lights has dropped, from about 10 kg in 1992-93, to about 0.2 kg in 2001. A corresponding drop probably also applies to exports of these, which in 1992-93 amounted to 90 kg of mercury. In summary, the export of mercury in products and semi-manufactured goods is estimated at less than 50 kg/year.

Part of the consumption of mercury as an impurity is due to the recycling of products, and a lesser part, to the consumption of Danish agricultural lime and biological fuels. Net imports of mercury are calculated as the total consumption of mercury as an impurity minus the part of this consumption that results from the recycling of products and from Danish agricultural lime and biological fuels.

Recycling covers the recirculation of mercury as an impurity in recycled material.

Overall, the above imports and recirculation correspond to the stated consumption of 2,100-5,000 kg of mercury/year.

The corresponding figure in the previous mass flow analysis featured a special box for Kommunekemi. Today, Kommunekemi is just one actor of several who handle mercury-containing waste. These actors send all of their mercury-containing waste abroad - possibly after sorting. The only mercury-containing waste that is treated in Denmark consists of amalgam filters, which are cleaned for reuse, and straight fluorescent tubes, the powder of which (containing mercury) is separated and exported. The loss of mercury to the environment due to these activities is small and is included under "Miscellaneous to air" in Fig. 4.1.

There is no longer any true collection of metallic mercury as there was in 1992-93. Metallic mercury is collected with other mercury-containing waste and exported. The figure shows metallic mercury under "Scrap and waste products."

By far the greatest part of mercury emitted to air by industry is due to cement production. There is also a minor contribution from offshore oil and gas extraction. Mercury from cremations constitutes 170-190 kg of "Miscellaneous to air."

The estimate given for the precipitation from air has been taken from Kjølholt et al., 1998, and represents the background precipitation, i.e., the atmospheric precipitation at points remote from the point sources. Mercury evaporates from agricultural soil and from water surfaces. No attempt has been made to estimate the magnitude of these transports.

Fig. 4.1 Mercury balance for Denmark, 2001 (all figures in kg/year)

Click here to see Fig. 4.1

*Of this, 1,900-2,900 kg of mercury is exported for deposition abroad.

Accumulation in Denmark
As can be seen from the figure, it is possible to calculate a negative accumulation of mercury of between 3,300 and 5,200 kg in Denmark. This illustrates the drop in mercury consumption, as well as the fact that existing stocks of mercury in Denmark are becoming depleted.

The total stock of mercury in Denmark in 1992-93 was estimated at 50-250 tonnes. In 1992-93, the negative accumulation amounted to between -(3,100 and 7,900) kg. The total depletion of the stock in the period up to 2001 is not known with any certainty, but it probably amounted to about 40 tonnes.

Airborne imports/exports
As can be seen from the figure, the air in Denmark must be expected to receive an annual 820-2,000 kg of mercury, whereas the background precipitation on Danish agricultural soil and in Danish coastal waters constitutes an annual total of 390 kg of mercury. In addition, there is the evaporation from agricultural soil and from inner Danish coastal waters. With reservation for the uncertainty introduced by the fact that there is no data for the expected, increased, precipitation in urban areas and close to the point sources of mercury emissions, Denmark must be expected to be a net exporter of atmospheric mercury. This was also the case in 1992-93 (Maag et al., 1996), even though the release and precipitation values have fallen since then.

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Version 1.0 June 2004, © Danish Environmental Protection Agency