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Mass Flow Analyses of Mercury 2001

Summary and conclusions

A detailed account has been prepared of the consumption of mercury in Denmark, distributed by its various uses. The disposal of mercury and its release to the environment have also been quantified. This analysis has predominantly been based on data from 2001.

Mercury balance
Available information on, and estimates of consumption and releases to the environment of mercury in Denmark are illustrated in Fig. 1.

Fig. 1 Mercury balance for Denmark 2001 (all figures represent kg/year)

Click here to see Fig. 1.

As shown in Fig. 1, the consumption of mercury is estimated at between 2,100 and 5,000 kg/yr, while imports of mercury and with mercury-containing products have been between 2,000 and 3,800 kg/yr, and exports with finished goods have been insignificant.

A more detailed presentation of the various areas of use is shown in Table 1, which is a simplification of Table 4.1, in the section entitled "Overall assessment" in this report.

Areas of use
The greatest intentional use of mercury is in the mercury amalgam used in dental fillings. This application corresponds to about 1/3 of the total consumption and 70-80% of the intentional consumption.

Lesser applications include light sources, batteries, thermometers, monitoring equipment, and laboratory chemicals. The total intentional consumption is estimated at about half of the total consumption.

The remainder of the total consumption is due to the unintentional "consumption" of mercury, e.g., as an impurity in coal and other goods and commodities.

Table 1 Consumption of mercury in Denmark

1) "Other products" includes oil, biological fuels, commercial fertilisers, agricultural lime, and other products in which mercury naturally occurs in low concentrations as a trace constituent or contaminant (at the ppb-level). The consumption of mercury in these applications can only be estimated with great uncertainty. See explanation of figures in Table 2.18.

2) Calculated as the average value of the listed consumption figures.

Development trends
The use of mercury is generally diminishing. Total mercury consumption has dropped to roughly 20% of the consumption in 1982-83. Consumption through the intentional uses of mercury has dropped to 10% of the consumption in 1982-83. The consumption has dropped to about 40% of that found in the previous mass flow analysis (i.e., for 1992-93, Maag et al., 1996), whereas the consumption through intentional uses has dropped to 25% of that in 1992-93. An additional drop in intentional uses can be expected in the future.

Despite the drop in most deliberate uses, it is worth noting that uses, in which consumption was previously heavy and which have been strictly regulated at the national and international levels, have logically enough become more marginal. In their place, uses that have not been exposed to the same regulatory pressure, and which have perhaps partly for that reason not developed to quite the same extent during the last decades, are now becoming apparent. For instance, dental fillings, button cell batteries of other types than those containing mercury oxide, and light sources.

It is also worth noting that the mobilisation and release of the mercury occurring as a trace element in coal continues to drop, primarily because Denmark is endeavouring to shift its energy production away from coal, in an effort to reduce emissions of carbon dioxide and a number of other pollutants.

Releases to the environment
Table 2, which is a simplified version of Table 4.4, offers an overview of releases of mercury to the environment.

Table 2 Releases of mercury to the Danish environment in 2001, kg/yr

1) The listed quantities are discharged to wastewater from which, after treatment in a sewage treatment plant, the mercury will pass in part to sludge and in part to the treated water discharged from the plant. These quantities are therefore included in "Municipal wastewater/sludge" and have not been included a second time under "Total."

2) The listed quantities are only included in the summation to the extent that they are not included under other headings.

3) "Other industrial activities" include oil and gas extraction.

4) This is deposited in landfills outside Denmark.

Emissions to the atmosphere
The principal source of emissions to the atmosphere is waste incineration, which is considered to be heavily dependent on the mercury contained in batteries, electrical switches, contacts and relays, and dental fillings. Note however that it is difficult to account for the input to waste incineration with any certainty, as the quantities of mercury involved are on the low side of that recorded for the emissions of the incinerator plants.

The second largest sources of emissions to the atmosphere are coal-fired power stations, which are estimated to contribute an annual 190-310 kg of mercury, whereas cremations contribute an annual 170-190 kg of mercury.

Discharges to water
Discharges to water are dependent on the wastewater discharged by municipal sewage treatment plants, which is primarily impacted by the mercury discharged from dental clinics.

Releases to soil
Releases to soil are heavily dependent on wastewater sludge and cemeteries (dental fillings).

Losses to landfills
By far the greatest part of the mercury sent to landfills consists of the residual products of waste incineration. These products are sent to landfills outside Denmark.

Development trends
Emissions to the atmosphere have dropped to about 1/4 of the emissions in 1982-83. This is particularly due to the drop in emissions from waste incineration resulting from improved flue gas cleaning. In 2001 these emissions amounted to less than 2/3 of the emissions in 1992-93. This drop is related 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 have dropped to about 1/5 of the level in 1982-83, but remain at the level of - or perhaps a little above - the discharges in 1992-93. The latter is due to the fact that discharges to the marine environment from offshore oil and gas extraction are included in the calculations for 2001.

Releases to soil have changed comparatively little since the survey for 1992-93. There has been a significant drop since 1982-83, this change is due to the fact that dressing seed corn with mercury has been phased out.

The increased use of waste incineration, combined with improved flue gas cleaning resulted in an increase in the quantity of mercury sent to landfills.

Collection and disposal/recycling
Considerable quantities of used mercury and mercury-containing waste are collected in Denmark. Thus, an annual 2-4 tonnes of mercury is collected with waste. This waste is exported.

Accumulation in Denmark
As can be seen from Fig. 1, these activities result in a negative annual accumulation of 3,300-5,200 kg of mercury in Denmark. In turn, this illustrates how mercury consumption is falling in Denmark, as well as the fact that the existing stores of mercury in Denmark (e.g., in electrical switches, contacts and relays in old telephones) are diminishing.

Stockpiling in Denmark
The total stock of mercury in Denmark was estimated at 50-250 tonnes for 1992-93. The negative accumulation at the same time was 3,100-7,900 kg of mercury/year. The total depletion of the stockpile during the period up to 2001 is not known with any certainty, but it probably constituted about 40 tonnes, so that the present mercury stockpile is of the order of 10-210 tonnes. The continuing flows of mercury to disposal indicate that the accumulated quantity of mercury in Denmark possibly was underestimated originally, and that the "detoxification" of the country will therefore take longer than anticipated. However, there is insufficient information on which to base a more precise quantification.

More detailed data and comparisons with 1982-83 and 1992-93 can be found in Section 4.

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Version 1.0 June 2004, © Danish Environmental Protection Agency