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3.I - Agricultural: Other
|NFR-Code||Name of Category||Method||AD||EF||State of reporting|
|consisting of / including source categories|
|3.I||Storage of digestate from energy crops||T2 (NH3, NOx)||Q, PS||CS (NH3, NOx)|
|Key Category||SO₂||NOₓ||NH₃||NMVOC||CO||BC||Pb||Hg||Cd||Diox||PAH||HCB||TSP||PM₁₀||PM₂ ₅|
In 2019, NH3 emissions from category 3.I (agriculture other) derived up to 0.6 % from total agricultural emissions, which is equal to ~ 3.2 kt NH3 . NOx emissions from category 3.I contribute 0.15 % (~ 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. 2021, Chapter 10 1). Note that these emissions of NH3 and NOx from storage of anaerobically digested energy crops are excluded from emission accounting by adjustment as they are not considered in the NEC and Gothenburg commitments (see Adjustment DE - D - Nitrogen oxides (3.D.a.2.c Other organic fertilisers applied to soils (including compost)') & Ammonia from Energy Crops). 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
|N amount in energy crops in Gg N|
Table 2: Distribution of gastight storage and storage in open tank of energy crop digestates
|Distribution of gastight storage and non-gastight storage, in %|
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. 2021, Chapter 10.2.1.)
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. NOx emissions are related to NO-N emissions by the ratio of 46/14. This relationship also holds for NO-N and NOx emission factors.
Table 3: IEF for NH3 -N and NO-N emissions from storage of digested energy crops
|IEF in kg NH3-N per kg N in digested energy crops|
|IEF in kg NO-N per kg N in digested energy crops|
Trend discussion for Key Sources
NH3 and NOx 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 NOx emissions from storage of anaerobically digested energy crops. Differences to last year’s submission occur only in 2018 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. (2021), Chapter 3.5.2.
Table REC-1: Comparison of NH3 and NOx emissions of the submissions (SUB) 2020 and 2021
|NH3 / NOx emissions in Gg|
Details will be described in chapter 1.7.