Science - September 24, 2015

Model for ammonia policy not properly researched

Albert Sikkema

The review panel which has evaluated Dutch ammonia policy cannot properly assess the calculation model for the programmatic approach to nitrogen (PAS). That did not stop secretary of state Dijksma from describing the panel’s recommendations on this model as positive.

The international review panel led by Briton Mark Sutton is positive about the ammonia model AERIUS, which the government uses to implement its ammonia policy, writes secretary of state Dijksma to the lower house of parliament. Yet the panel could not properly assess that model due to ‘insufficient information’.

The AERIUS model, which is partly based on Wageningen data, calculates ammonia emissions and deposition at the local level in the Netherlands. This data underpins the programmatic approach to nitrogen (PAS) on which the country’s manure legislation is based. The international panel poses the question of whether the AERIUS model is scientifically sound. Its answer is: ‘Yes, as far as the Panel can see, based on the information presented. However, insuffi cient information was provided on the technical basis of the AERIUS model, which should be subjected to ongoing research.’ The secretary of state sent this report to the lower house on 8 September with a covering letter. In this letter Dijksma said she was pleased with the positive evaluation of AERIUS.

The model is ‘world-leading’ thanks to its detailed farm-level information, but a thorough peer review study of the model is a top priority, says the panel. The panel also feels that to make the model more reliable, more data are needed about the local weather conditions and the actual behaviour of livestock farmers. Given this model’s central role in the Dutch manure policy, additional research is called for in the panel’s view. Dijksma and her colleague at the ministry of Infrastructure and Environment are giving thought to which of the panel’s recommendations she will act upon.

It is important that the AERIUS model is properly tested and, if necessary, improved, says Wageningen ammonia researcher Gerard Velthof. ‘You really need a detailed model like that if you want to hold farmers accountable for their ammonia emissions as farm level.’