Fit for purpose emissions testing

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 health effects of emissions, that, if successfully enforced, could, according to the European Commission, reduce premature deaths and years of life lost each year in Europe by 13,000 and 125,000, respectively. Applying the polluter pays principle, the IED requires around 50,000 facilities to meet stricter emission limit values (ELVs), achievable by using abatement technologies 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, involving passing stack gases through hydrogen peroxide before analysis for sulfate content, takes days to weeks to produce data. Attaining targeted lower limits would be a favourable outcome for air quality but presents a measurement challenge. Indeed, evidence emerged that raised doubts about the suitability of the SRM at lower levels of SO2 contemplated by the IED.

Alternative portable automated measuring systems were sometimes used not least due to inherent advantages for operators of real-time feedback. However, it was uncertain that these instrumental methods could be developed as a new SRM for showing compliance with the IED as the necessary quality assurance and control procedures had not been developed.

In 2015, CEN recognised that EN 14791 was unlikely to comply with limits scheduled to come into force, and that unexplained causes of errors during stack gas sampling and conditioning hindered the development of quality procedures for instrument-based alternatives. It asked the metrology community to identify causes of errors, devise methods to ensure representative samples can be delivered from stacks to analytical instruments, and for contributions to standardisation.