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Cleaner Technology Projects in Denmark 1997

Analysis of tin consumption and emissions with focus on organotin

The knowledge, which this report is based on, is acquired through information from the Danish National Agency of Statistics and data from private companies and governmental institutions.

The total tin consumption in manufactured goods in Denmark in 1994 is estimated at 740-1,280 tonnes. The turnover of tin in the society was somewhat higher as there also was an import/re-export of tin for packaging, copper-tin alloys, and solders in electronics and auto radiators.

In total, the consumption of metallic tin was 640-1,000 tonnes tin. The most significant fields of consumption were tinplated containers (33% of total consumption), solder used in electronics, plumbing and sheet metal joining, auto radiators, and container seaming (32%), and copper-tin alloys (bronze) used in switches, valves and bearings (10%). Apart from uses of copper-tin alloys it was characteristic that tin was used in consumer products which were disposed of with municipal solid waste and there was hardly no recycling of tin from discarded consumer products.

The total tin consumption with chemical compounds in 1994 was 27-43 tonnes Sn. Organotin compounds constituted the main part. Organotin compounds are defined as compounds that contain one or more organic functional groups attached to the tin atom with a relatively stable tin-carbon bond. The compounds are dependent on the number of tin-carbon bonds divided into four classes: the mono-, di- tri- and tetraorganotins. Tetraorganotins are not used in Denmark.

The major use of mono- and diorganotin compounds was for UV and heat stabilisers in PVC. The main uses of tin-stabilised PVC were transparent rooflight sheets, tarpaulins, bottles and packaging. The consumption of tin stabilisers has had a downward trend due to substitution of PVC packaging with other materials.

Beside this, diorganotin compounds were used in low concentrations as catalysts for silicone, polyurethane foam and for a broad range of glues and paints. The total consumption with these uses is relatively small, but diorganotin compounds are used in a range of semi-manufactured goods for consumer products such as electronics, footwear, vehicles, and furniture.

Triorganotin compounds are used as a biocide in antifouling paint and as fungicides in surface and vacuum preservation of wood. In 1994 only a single organotin pesticide was used in Denmark.

Inorganic tin compounds were used for electroplating tin-lead alloys in the electronic industry and electroplating of tin or tin-nickel on equipment for the food industry, scientific instruments etc. Moreover inorganic compounds were used for glass and ceramic glazes.

There are only a few available measurements of tin emissions in Denmark. Emissions from the different sources are consequently estimated from emissions factors from the literature. The total emission to the air is estimated at O.5-6 tonnes Sn. The main sources were production of iron and steel, glass, cement, ceramics, and castings, burning of coal and oil and incineration of municipal solid waste.

No data on organotin emission to the air was available but a modest emission from solid waste incineration and glass production is expected.

The discharge of tin to the aquatic environment is the result of municipal wastewater, release of organotin from antifouling paints on ships, and emission of organotin from shipyard activities.

The emission of organotin from antifouling paints can either be estimated as the emission from ships built or repaired in Denmark or as the total emission from vessels to the Danish waters. Based on the consumption of antifouling paint in Denmark, the emission is estimated at 2.9-3.8 tonnes Sn/year. Danish vessels are estimated to be responsible for 12-35% of this emission.

Based on preliminary studies of organotin in municipal waste water it is estimated that triorganotin in waste water constituted at most 5% of the total triorganotin discharge to the aquatic environment while at least 95% directly or indirectly was due to the use of antifouling paint.

Discharges of organotin with wastewater from shipyards have been significantly reduced due to effective wastewater treatment. But it is still unclear to what extent organotin is emitted with aerosols from spray painting and dust from sand blasting. The present information indicates that these activities could contribute significantly to the total discharge of organotin compounds to the aquatic environment.

Release of organotin to soil is the result of municipal waste water sludge on agricultural soil (O.1-0.9 tonnes SNP), leaching and spill of wood preservatives (0.4 - l.4 tonnes SNP), use of pesticides (0.02 tonnes SNP) and emissions of dust and aerosols with antifouling paint from ship yards (0.03-0.3 tonnes Sn). The compounds that are released may be degradation products as the organotin compounds are degraded within and at the surface of the products where they are used.

There is hardly any recycling of tin with used products. In 1994, 220-270 tonnes tin was re-cycled with scrap - principally from manufacturing of products. The scrap was exported. Indirectly organotin was re-cycled with transparent PVC sheets, but compared to the total consumption of organotin compounds recycling was rather insignificant.

Author/ institution

Carsten Lassen, Steffan Vaaben og Erik Hansen, COWI 

This report is subsidised by the National Council for Recycling and Cleaner Production 

ISSN no. 0908-9195
ISBN no. 87-7810-735-0

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