For the ammonia inventory of the German agriculture, a calculation of uncertainties has been carried out according to EMEP (2023), Part A, Chapter 5. This approach is in line with the IPCC approach to calculate the overall uncertainty of GHG inventory, see Chapter 6.10.
Table 1 shows input data, calculation details and the resulting overall uncertainty of the German ammonia emission inventory. (For the content of columns H and M see the footnote in Table 1).
Input data for the calculations were the emissions of the first and of the last year of the time series as well as the uncertainties of the activity data and the emission factors. For the uncertainties see Chapters 6.3 and 6.6.
For the collective categories 'synthetic fertilizer', 'manure spreading, all animals', and 'other organic fertilizers' by analogy to the procedure for the overall uncertainty of the GHG inventory (see Chapter 6.10), the uncertainties of activity data and emission factors of the respective subcategories are aggregated using error propagation calculation (see Chapter 6.2). Only the aggregated uncertainties are included in the calculation of the total uncertainty of the ammonia inventory.
The overall uncertainty is expressed as percentage of the total emissions of the last year of the time series and is listed at the very bottom ot column H. The other values in column H, however, are auxiliary data required for the uncertainty calculations. These values are proportional to the contributions of the various sub-sources to the total variance of the ammonia inventory, cf. footnote in Table 1. The total uncertainty of ammonia emissions from German agriculture is 10.0 % (valid for 2023). The overall uncertainty is largely determined by the uncertainties in the manure management of dairy cows and fattening pigs and, above all, the spreading of animal manures.
The percentage uncertainties of the trends of the overall emissions of ammonia from German agriculture is given at the bottom of column M. (For the meaning of the values in column M see the footnote in Table 1). The uncertainty of the trend 1990 - 2023 is 4.1 %.
Table 1: Uncertainty calculation for the German agricultural ammonia inventory 