A further explanation of the ammonia hole

The Minister of Agriculture has had the Animal Fertilizers Committee (CDM) and the National Institute for Public Health and the Environment (RIVM) conduct research into the ammonia hole. Schouten sent the results to the House of Representatives on Monday, January 14. This shows, among other things, that the explanation for the ammonia hole mainly comes from the RIVM.

Research by the CDM
CDM has looked for explanations for the difference in the calculated emissions and the measured ammonia concentrations between 2005 and 2016. During this period, the calculations and measurements are increasingly out of sync. The NEMA (National Emission Model Agriculture) working group has been looking for reasons why livestock farms emit more ammonia than calculated.

The measurements are shown for the NEMA working group (and the CDM). concentrations not up for discussion in any way. NEMA also ignores the question of whether there may also be causes outside the agricultural sector. On the one hand, this makes sense, because this concerns the CDM; it is obvious that they are concerned with their field of responsibility. On the other hand, a broad context is missing and it seems as if everything outside their field of vision does not exist.

Principles and assumptions
Based on 'expert judgement', the working group has identified 3 principles that have changed in recent years and could influence the calculations. "This advice did not carry out a complete and systematic uncertainty analysis of all relevant assumptions in the NEMA methodology," NEMA reports. In other words: the working group sat down and came up with 3 explanations for the gap. These have not been further substantiated or analyzed.

If we look at the existing controversy, it is incomprehensible that the CDM is proceeding in this way. It is precisely the members of the working group that are part of the current controversy. Their names raise the eyebrows of many ammonia experts; also because they use 'expert judgement'.

The assessment leads to the assumption that the calculated emissions are too low, especially because the stables have higher ammonia emissions than gedacht. The second assumption focuses on fraud with manure sales outside the Dutch agricultural sector. Finally, NEMA addresses the fact that manure application is less emission-free than expected.

Adjustments
The working group also came up with a number of possible causes for the fact that the emissions were estimated too low; for example, the emission factors in the stable are too low, the emission factors for nitrogen loss during manure storage are too low, nitrogen losses occur during manure treatments, the samples do not provide a good picture and the excretion factors for nitrogen and phosphate at national level deviate from the practice. 

Based on the above assumptions, the working group made calculations and this resulted in an increase in emissions from stables with solid poultry manure from 0,7% to 14%. A miscalculation with the factor 20 seems to require an explanation. However, the explanation or explanation for that miscalculation is lacking. It only refers to the fact that air scrubbers emit more than previously calculated. However, there is no answer to the question of what caused this miscalculation.

Agricultural Census
The calculations are partly based on the agricultural census. However, in principle, questions about the stable systems are only asked once every 1 years. The working group is mainly working towards explaining the ammonia gap by looking for reasons for increased emissions. However, the group ignores the fact that if a livestock farmer has a new, low-emission housing system in year 5, this will not be included in the calculations for 2 years.

Various low-emission systems (such as aeration, manure mix bacteria or spreading manure with water) are also not included in the figures. There are therefore also a number of situations where the figures actually calculate too high emissions. This is ignored, as a result of which the reasoning used is flawed.

Eventually each falls ammonia hole can be explained as 'fraud' and the working group seems to be gratefully taking advantage of this to close the gap. The working group suffices with a reference to Minister Schouten's 'Enhanced Enforcement Strategy'.

Research by the RIVM
The RIVM has also looked into the cause of the ammonia hole and has come up with innovative insights. In the report 'Developments in emissions and concentrations of ammonia in the Netherlands between 2005 and 2016', the organization looks beyond the agricultural sector. For example, the RIVM has looked at the composition of the air and how ammonia behaves in it. In short: because the air is becoming cleaner, the proportion of ammonia in it is increasing.

Even if the amount of ammonia emission remains the same, an increase is visible in the concentration. According to the RIVM, approximately 75% of the difference observed between the calculations and the measurements can be explained by atmospheric and chemical processes.

Cleaner air
Because there are fewer sulfur and nitrogen dioxides in the air, the air becomes cleaner. This also means there are fewer gases left that ammonia can form particulate matter. This process explains approximately 40% of the higher concentration. In addition, less ammonia can precipitate because the soil and vegetation are less acidic. This leaves more ammonia in the air. This explains about 20% of the higher concentration. The weather conditions, in combination with some other factors, also explain another 15%.

The report indicates how complicated the processes surrounding ammonia are, and how a reduction in ammonia does not immediately lead to a lower concentration in the air. Moreover, deposition is also determined by deposition of other substances. The RIVM recommends that the findings be incorporated into the reporting of the Compendium for the Living Environment and requests additional research in order to clarify the geographical differences in the measurements and calculations.