Robust sulfur dioxide emissions monitoring

Challenge

Air pollution remains the main environmental factor in human ill-health, with about 400,000 premature deaths attributed to ambient air pollution annually in the EU.

Industrial processes account for a sizeable share of polluting emissions, including sulfur dioxide (SO₂ ), produced by burning fuels containing sulfur compounds and waste incineration. This toxic gas contributes to the formation of particulate aerosols that, along with other oxide compounds, can be responsible for respiratory illnesses, especially in children and the elderly.

The 2010 Industrial Emissions Directive (IED) commits member states to control and reduce the effects of emissions, that according to the European Commission, if successfully enforced, could reduce premature deaths and years of life lost each year in Europe by 13,000 and 125,000, respectively.

Around 50,000 industrial facilities will be expected to comply with reduced emission limit values (ELVs) through the use of abatement technologies, the performance of which overseen by continual emission monitoring systems, in turn periodically tested according to approved Standard Reference Methods (SRMs).

The European Commission mandated Comité Européen de Normalisation (CEN) to develop SRMs to support previous legislation, assigning special status to these standards. For SO₂ emissions, the SRM became specified by EN 14791, but this manual ‘wet chemistry’ method takes days to weeks to provide feedback, depending on the time needed to perform analysis. Attaining lower limits would be a favourable outcome for air quality but evidence emerged raising doubts about the suitability of the SRM for measuring at levels of SO₂ targeted by the IED.

Portable automated measuring systems (P-AMS) were sometimes used instead, not least due to inherent advantages for operators of real-time feedback. However, it was uncertain if these instrumental methods could be developed as an SRM for showing compliance with the IED, since necessary quality assurance and control procedures had not been formulated.

In 2015, CEN requested that a potential alternative method be investigated as it anticipated that EN 14791 was unlikely to comply with limits scheduled to come into force.

The Environment Agency (EA), the body responsible for environmental protection in England, permitted the use of P-AMS for measuring SO₂ but wanted specifications to be published by CEN to build confidence in the approach.