3.I - Agricultural: Other

In 2021, NH₃ emissions from category 3.I (agriculture other) derived up to 0.7 % from total agricultural emissions, which is equal to ~ 3.2 kt NH₃ . NO_x emissions from category 3.I contribute 0.16 % (~ 0.17 kt) to the total agricultural emissions. All these emissions originate from the storage of digestate from energy crops (for details on anaerobic digestion of energy crops see Rösemann et al. 2023, Chapter 5.1 ¹⁾. The emissions resulting from the application of energy crop digestates as organic fertilizer are dealt with under 3.D.a.2.c.

Time series of activity data have been provided by KTBL (Kuratorium für Technik und Bauwesen in der Landwirtschaft / Association for Technology and Structures in Agriculture). From these data the amount of N in energy crops fed into anaerobic digestion was calculated.

Table 1: N amount in energy crops fed into anaerobic digestion

Table 2: Distribution of gastight storage and storage in open tank of energy crop digestates

The calculation of emissions from storage of digestate from energy crops considers two different types of storage, i.e. gastight storage and open tank. The frequencies of these storage types are also provided by KTBL (see Table 2). There are no emissions of NH₃ and NO from gastight storage of digestate. Hence the total emissions from the storage of digestate are calculated by multiplying the amount of N in the digestate leaving the fermenter with the relative frequency of open tanks and the emission factor for open tank. The amount of N in the digestate leaving the fermenter is identical to the N amount in energy crops fed into anaerobic digestion (see Table 1) because N losses from pre-storage are negligible and there are no N losses from fermenter (see Rösemann et al. 2023, Chapter 5.1).

As no specific emission factor is known for the storage of digestion residues in open tanks, the NH₃ emission factor for storage of cattle slurry with crust in open tanks was adopted (0.045 kg NH₃ -N per kg TAN). This choice of emission factor is based on the fact that energy crops are, in general, co-fermented with animal manures (i. e. mostly slurry) and that a natural crust forms on the liquid digestates due to the relatively high dry matter content of the energy crops. The TAN content after the digestion process is 0.56 kg TAN per kg N. The NO emission factor for storage of digestion residues in open tanks was set to 0.0005 kg NO-N per kg N. Table 3 shows the resulting implied emission factors for NH₃ -N and NO-N. NO_x emissions are related to NO-N emissions by the ratio of 46/14. This relationship also holds for NO-N and NO_x emission factors.

Table 3: IEF for NH₃ -N and NO-N emissions from storage of digested energy crops

NH₃ and NO_x from storage of anaerobically digested energy crops are no key source.

All time series of the emission inventory have completely been recalculated since 1990. Table REC-1 shows the effects of recalculations on NH₃ and NO_x emissions from storage of anaerobically digested energy crops. Differences to last year’s submission occur only in 2020 and are due to the update of activity data (see main page of the agricultural sector, Chapter 5 - NFR 3 - Agriculture (OVERVIEW), recalculation reason No 15). For further details on recalculations see Rösemann et al. (2032), Chapter 1.3.

Table REC-1: Comparison of NH₃ and NO_x emissions of the submissions (SUB) 2022 and 2023

Details are described in chapter 1.7.