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Nitrogen oxide emissions result mainly from the combustion of fossil fuels such as natural gas. Nitrous oxide (N2O) contributes to global warming but does not have the acidification impact of NO and NO2. The emissions are expressed as the sum of nitrogen oxide emissions (NO and NO2, expressed as NO2) excluding N2O.

Sulfur oxide emissions (SO2) arise mainly from the combustion of anthracite or coal.

Non-methane volatile organic compounds (NMVOC): volatile organic compounds (VOCs) are compounds that have a standard boiling point inferior or equal to 250°C (EU Solvent Directive 1999/13/EC). NMVOCs are VOCs other than methane. Methane emissions from Solvay's mining activity at Green River (Wyoming, USA) are not included. Their impact is integrated into the greenhouse gas emission indicator.

Nitrogen oxide and sulfur oxide emissions contribute to atmospheric and freshwater acidification. NMVOC emissions contribute to the formation of tropospheric ozone and summer smog. Thus, these categories of substances are material because they directly impact on air quality.


Air quality is managed through the Solvay Care Management System (SCMS) and is aligned with the requirements of the ISO 14001 standard (edition 2004), the OHSAS 18001 standard (edition 2007), and Solvay group HSE requirements.

Solvay is committed to improving air quality at the local and regional levels, in close cooperation with local stakeholders. In the framework of its environmental plan, Solvay focuses on the following pollutants: nitrogen oxides (NOx), sulfur oxides (SOx), and non-methane volatile organic compounds (NMVOC).

Health, safety, environment management, and compliance

Indicators and objectives

Solvay’s objectives:



of nitrogen oxides emissions intensity



of sulfur oxide emissions intensity



of non-methane volatile organic compound emissions intensity

Baseline 2015

Air emissions intensity

In kg per € EBITDA







Scope: Consistent with financial reporting.

Nitrogen oxides – NOx







Sulfur oxides – SOx







Non-methane volatile organic compounds – NMVOC







Solvay's 2017 achievements for the Nitrogen oxides, Sulfur oxides emissions and Non-methane volatile organic compounds intensity are about 5.5% and 9% better than the expected 2017 target, respectively.

Absolute air emissions

In metric tons







Scope: Consistent with financial reporting.

Nitrogen oxides – NOx







Sulfur oxides – SOx







Non-methane volatile organic compounds – NMVOC







There are several reasons for improvements with respect to nitrogen oxides, including:

  • Deconsolidation of the divested GBU Performance Polyamides (- 941 metric tons);
  • Within the GBU Solvay Energy Services, implementation of a water injection system in April 2017 on the gas turbine of Torrelavega in Spain (- 283 metric tons) and of urea injection since March 2017 on the existing DeNOx installation on the power plant of Tavaux (- 185 metric tons), reduced stream factor of the power plants of Brotas in Brazil (- 99 metric tons) and Pont de Claix in France (- 92 metric tons);
  • For the GBU Silica, improved performance of the silicate production furnace in the site of Livorno in Italy (- 123 metric tons).

The evolutions for sulfur oxides emissions result from the following:

  • integration of the SOx emissions (+ 561 metric tons) from the site of Atequiza Jalisc in the United States (GBU Technology Solutions); 
  • thanks to the GBU Solvay Energy Services, full benefit from the DeSOx installation in November 2016 on the coal burner of Tavaux site in France (- 460 metric tons) and of the installation of the CFBB boiler in Devnya in Bulgaria (- 375 metric tons);
  • increased availability of low-sulfur grade coal for the power plants and lime kilns used by the soda-ash plant in Torrelavega (GBU Soda Ash and Derivatives) in Spain (- 300 metric tons);
  • increased use of bio-mass by the power plant of Dombasle (GBU Soda Ash and Derivatives) in France, combined with an improved stream factor of the natural gas fired power plant at the same site (- 136 metric tons).

The status-quo on the Non-methane volatile organic compounds is due to the following causes:

  • integration of the emissions from the GBUs Composite Materials (+ 111 metric tons) and Technology Solutions (+ 74 metric tons), compensated by the divestment of the GBU Performance Polyamides (- 118 metric tons);
  • small increases for the GBUs Specialty Polymers (+ 65 metric tons), compensated by improvements of the GBU Peroxides (- 59 metric tons) and of the GBU Soda Ash and Derivatives (- 45 metric tons).