The new calculation error made by RIVM in the top 100 of ammonia emitters is not due to the use of outdated emission data, but to the incorrect allocation of national emissions to shed locations. For the time being, the institute will no longer be issuing any new advice or publications in this area.
Director of Environment and Safety Charles Wijnker said this in a technical briefing in the House of Representatives. He acknowledges that the errors have caused serious reputational damage and that thorough repairs are required. A month has been set aside to make an impact assessment - in other words: damage inventory. According to Wijnker, the errors are not in the Aerius version that governments are currently working with. He did acknowledge that old data is still being used to some extent, for example from 2018.
Wijnker's explanation is broadly in line with what poultry managers previously indicated. The emission calculation for poultry houses is based on average emission figures without the necessary corrections for the various (and often newer) types of houses available. Wijnker: "The average emission calculations are still correct, but the further you zoom in on individual stables, the greater the deviation."
Because checking and fixing the errors takes time, the new Aerius version that is due to be released later this month may be delayed. It may also affect other 'arithmetic products'. In the meantime, the RIVM is no longer issuing new advice or publications in the field of nitrogen.
In his explanation, Wijnker also apologized to the affected farmers.
To calculate emissions, the RIVM has divided the country into virtual hexagons (hexagons). These have different scale levels. The largest cover an area of 256 hectares. Then there are hexagons with an increasingly smaller area, of 64, 16, 4 and 1 hectare. Something went wrong with the allocation of emissions to this lowest level, especially poultry and sometimes also pigsties. Wrong emission factors have been assigned to these companies. In some cases, emissions have been estimated to be twice as high as actual emissions. To calculate emissions at this level, not only air quality measurements are used, but also May count data and other data.
The House of Representatives stated many critical questions to the RIVM, including what the errors mean for, for example, identifying and purchasing 'peak load generators'.