RIVM hoofdgebouw

On 1 November 2022, RIVM announced that its list of top-100  ammonia emitters was compiled using incorrect emission factors for some types of livestock housing. RIVM has investigated whether the erroneous data had also been used in other RIVM products. This analysis, conducted with the support of experts at Wageningen University & Research and Statistics Netherlands, found that the impact was limited. Since the impact is now clear, the temporary hold on publications that RIVM had imposed pending the results has also been lifted.

National emissions overview unchanged, slight local differences

RIVM reports reliable national figures. The more closely studies zoom in on regional or local situations, the less reliable such figures become. The impact analysis found that the error did not affect national and regional emissions reported for 2019. At the local level, the incorrect emission data had a minor, yet inconsequential impact on local emission distributions.

Local differences in concentrations and depositions

The emission data had also been used to calculate concentrations and depositions. To ascertain the impact on the concentrations and depositions reported for 2019, RIVM recalculated the topographical distribution of agricultural emissions using the corrected data. This yielded minor local differences for ammonia (NH3) and fine particles. Again, the differences had no impact at the national level. The maps that show the concentrations and depositions of NH3 and fine particles will need to undergo minor adjustments. These maps are published annually. New large-scale concentration and deposition maps (GCN/GDN) of the Netherlands will be published in the spring of 2023. These will be based on 2020 data. Users of the 2019 maps will be informed accordingly. The inaccurate data on fine particles had no impact on other RIVM products.

Most significant impact: new version of AERIUS delayed

The incorrect data on ammonia had been incorporated into the unpublished draft version of AERIUS 2022. No permits were granted on the basis of the incorrect data. Inputting corrections in AERIUS will take more time, delaying the scheduled release of AERIUS 2022 until 26 January 2023.

Inaccuracies in source data

RIVM’s impact analysis also revealed a number of inconsistencies in the data files. Together with its knowledge partners, RIVM will look into how data quality can be improved in these files.

List of top-100 emitters unsuitable as a basis for policymaking

The list of top-100  ammonia emitters was not one of RIVM’s regular reports, but a one-off publication in response to questions from the House of Representatives. The data files that RIVM uses provide a useful national and regional overview of these emissions. However, RIVM calculations based on these files do not lend themselves to reporting on specific emissions at the level of individual farms. RIVM is transparent about this and recommends considering other local data and information alongside these detailed data for use in decision-making.