16 Feb 2023

Guidance for diffuse VOC emission determination following EN 17628:2022

Report no. 1/23: This document addresses the periodic determination of diffuse emissions of non-methane volatile hydrocarbon compounds from refineries by means of remote sensing. A recent European standard, EN 17628:2022, addresses the proper conduct of such a survey and the techniques that might be chosen to be applied.

This document is aimed primarily at oil refinery sites with no prior experience of remote sensing surveys. It covers the planning, preparation for and execution of a measurement campaign and the assessment of results.

Unlike measurements on channelled emission sources, diffuse emission measurement locations change during the day according to wind-direction and survey progress. Timely access to operations data is needed in order to distinguish between on-going, intermittent, maintenance, and possibly unknown emission sources. Questions may be unfamiliar and detailed. Communications channels may have to be prepared to enable this information exchange and not add burden to normal working.

Although preliminary results will be available at the end of the measurement period, full analysis and interpretation of survey results make take some time. It is important to ensure that all necessary complementary data was gathered because it may be difficult/impossible to recover after some weeks have passed. A process of continuous review and information exchange is recommended in order that uncertainties and data dependencies are explained to refinery staff and needed information promptly identified.

The results of a survey apply only to the duration of the survey. Results cannot be extrapolated to give annual emissions. However, a survey that confirms that the refinery inventory of emission sources is complete and that the refinery can explain and quantify the observed emissions will strengthen the refinery position on reporting.

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