Spatial distribution of emissions to air - the SPREAD model

40
As lined out the agricultural sector covers a number of sources, which
are distributed according to different spatial keys. Emissions from the
agricultural sources are calculated with a bottom-up approach for the
spatial distribution. The bottom-up calculation is carried out on a
100x100 m grid, which is aggregated into a 1x1 km grid in SPREAD.
The emissions estimated by the bottom-up approach are not completely
consistent with the emissions in the national inventory, which are calculated
with a top-down approach as the emission calculation must be consistent
with the national statistics. In order to ensure that the emissions
in SPREAD are equal to the reported emissions for 2008, the reported
emissions are distributed according to the distribution keys set up by the
bottom-up approach.
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CH4 from enteric fermentation is distributed according to data on the
number and categories of animals on farm level. CHR holds data for the
majority of the livestock covering animal-categories related to e.g. breed
and age (e.g. calf, heifer and cow or sow and piglets) and use (e.g. dairy
cattle and beef cattle). The horse breeding register holds addresses of the
owners, and this is the best dataset for spatial distribution of emissions
from horses even though the horses might be located at different sites
than the owners address. As the register for horses does not hold information
on pasture areas, emissions from both stables, storage and grazing
are located at the owners address.
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The distribution of CH4, N2O, NH3, TSP, PM10 and PM2.5 from manure
management is based on the data from GLR and CHR. As for enteric
fermentation the location of the animals, housing systems and manure
systems is important for distribution of emissions from manure management.
Emissions of NH3 from manure management are related to activities at
the farms and are treated as point sources. Calculations are based on the
normative figures on N-excretion per farm corrected for grazing. As for
enteric fermentation data the horse breeding register is included in the
calculation.
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Agricultural soils covers ten sources; crops, application of manure, application
of synthetic fertiliser, N-excretion on pasture range and paddock,
NH3 treated straw, crop residue, N-fixing crops, cultivation of histosols,
leaching and atmospheric deposition. Emissions of NMVOC, N2O
and NH3 are included in one or more of the sources.