Sustainability Topic: Air Pollution Emissions

305–7  Significant air emissions

Other significant air emissions deriving from Boliden’s operations are nitrogen oxides (NOx), sulphur oxides (SOx), metals, and dust. The most common of the sulphur oxides (SOx/SO₂) is sulphur dioxide, and Boliden generally uses the expression ‘sulphur dioxide’ to describe this emission. The figures for sulphur dioxide and NOx disclosed in the table are the direct measured emissions from sources at Boliden’s smelters. The figures for metals and dust include direct-measured emissions from smelter stacks, but exclude diffuse emissions.

Diffuse emissions are generated at both mines and smelters and the environmental impact is due to dust particles containing metals being dispersed by the wind. All operations are working systematically to reduce particle emissions to air, e.g. by enclosure of dust-generating equipment and by salting and watering roads. The diffuse emissions are monitored, but are difficult to quantify in an aggregated manner.

Emission Reduction Efforts

Boliden’s efforts to reduce emissions are based on an overall analysis of the environmental impact. The impact and risk ­assessments are revised on a regular basis, as are the measures to be taken. The work is controlled and conducted by each individual business unit, as local circumstances may differ. Follow-up at the Group level is conducted on a monthly basis.

Sulphur dioxide emissions to air are mainly attributable to gases generated during the smelting processes at the Harjavalta and Rönnskär copper smelters. The amount of sulphur dioxide emitted during the process depends on factors such as process stability, the efficiency of gas cleaning systems, and the amount of sulphur in raw materials. Thus, one way of reducing emissions is to maintain a stable smelting process and to conduct ongoing, effective maintenance work and process control. The monitoring and control of abatement systems for effective gas cleaning is important work and is carried out ­continuously.

The SO₂ emissions to air decreased in 2019 following investments and improvements of sulfuric acid facilities at Boliden Smelters previous year. Increased metal emissions to air mainly derive from diffusive emissions of zinc in the Kokkola smelters.

Emissions to air are mainly based on periodic monitoring in accordance with applicable national standards. Emissions from fuel are calculated using the fuel properties data provided by the supplier. Accredited laboratories, both internal and external, are used for the analyses of samples taken on site.

Emissions to air (metric tons)

2017 1)

2018 1)











Particulate matter




Metal emissions to air (me-eq)




Metal emissions 1) to air (mass)




1) Updated model for calculation of metal equivalents, based on the framework for Natural Capital Protocol