THE MOST CERTAIN THING ABOUT THE NEW INDUSTRIAL EMISSIONS PACKAGE IS THAT WE HAVE AN ISSUE WITH UNCERTAINTY
The role of measurement uncertainty in ensuring an effective transition to lower emissions from European industry
Under the umbrella of the Industrial Emissions Directive (IED) and its Best Available Techniques (BAT) principle, the concept of measurement uncertainty is especially relevant for two different objectives: on the one hand, instruments and measuring methods have to achieve a maximum permissible uncertainty in order to be used to monitor emissions in IED installations; on the other hand, for reporting and compliance purposes, a measured value should be checked against the related emission limit value after subtraction of the uncertainty in order to ensure legal certainty. In this article we will focus on the second application of the uncertainty concept in the implementation of IED and BAT Conclusions.
While the IED specifi es basic requirements to achieve stated confi dence intervals for the main pollutants in Annexes V and VI, certain authorities may specify a performance criterion for the uncertainty. For example, they may specify that the uncertainty cannot be more than 10% of a prescribed Emission Limit Value (ELV). Such a specifi cation would prevent users of methods with large uncertainties gaining any benefi t due to the subtraction of the uncertainty from measured values as described above. Otherwise, theoretically if a laboratory/method had an uncertainty of 50 % of the ELV, it would be easier for the plant to be compliant, compared to a method with a lower uncertainty. This could encourage a preference for poor performing laboratories/ methods over good performing laboratories/methods. N.B., this is clearly more of an issue if the uncertainty assigned to the measurement results is an overly conservative estimate.
IED and relevant BAT Conclusions are the legislative reference IET NOVEMBER / DECEMBER 2022
in the EU to environmental permits for industrial installations that are covered under IED, Annex I. Environmental permits are drafted by competent authorities that will consider how a specifi c installation can implement Best Available Techniques (where technique is meant as both the technology used and the way in which the installation is designed, built, maintained, operated and decommissioned). When setting ELVs in a permit there are three key elements that should be properly assessed:
• the ELVs must be capable of being monitored in practice
• monitoring requirements and data quality requirements must be specifi ed together with the ELVs
• compliance assessment procedures must also be specifi ed together with the ELVs so that they can be readily understood.
Lower ELVs provide a clear refl ection of the ambition to reduce pollutant emissions, and refl ect the potential for BAT. However, an ELV should be set so that the monitoring required in order to determine compliance is within the capability of available measurement methods, until technological progress allows for better performances. For example, in order to obtain detectable quantities of dioxins from stack emissions it is usually necessary to sample over several hours. In this case the averaging time should correspond to this practical sampling duration. The limit setting process must therefore take into account the technical limitations of the relevant monitoring methods which will include consideration of detection limits, response times, sampling times, possible interferences, general availability of the methods and possible use of surrogates.
Clarity about the relationship between ELVs and the monitoring framework is essential to make sure that these limit values have meaning. Good practice recommends that monitoring requirements to be included with Emission Limit Values in permits should cover – directly or indirectly:
- legal and enforceable status of the monitoring requirement - averaging period of ELV and reported measured data - pollutant or parameter being limited - data quality requirements - requirements on location for sampling and measurements
- timing requirements of sampling and measurements (continuous/periodic)
- reference conditions and requirements on measurement of peripheral data
- feasibility of limits with regard to available measurement methods
- general approach to the monitoring available for relevant needs
- reference to technical details of particular measurement methods
- self-monitoring arrangements
- operational conditions under which the monitoring is to be performed
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