LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PARALLEL SESSION 6C: POULTRY AND PORK PRODUCTION SYSTEMS 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
Figure 2. Sensitivity of climate change potential to field N2O emission rates of different slurry fractions.
3.2.2. NH3 emission rate (field)
Values for the sensitivity analysis for the NH3 emission rate are based on ranges provided in Hansen et
al., (2008). Table 1 provides an overview of the emission rates that were analysed.
Table 2: NH3-N emission rates in main sensitivity models (% of TAN-N).
Main model Low High
Slurry 16 3.1 20
Liquid fraction 12 1.6 10
Solid fraction 39 13 65
Compost 39 13 65
The impact category that is affected most by the changing emission rates is marine eutrophication (Table
3). Lower NH3 emission rates (Table 2) correspond to a higher contribution to marine eutrophication. Marine
eutrophication is mainly caused by NO3 - emissions to water bodies and indirectly by NH3 emissions to the
air. It is assumed that NH3 emissions mainly take place within the first hours to days after land application,
NO3 - emissions take place later in the 10 year period that is tracked. Therefore NO3 - emissions depend on
how much N is removed from the soil system in the form of NH3. More NH3 emitted means a decrease in
NO3 - leaching. The relative ranking of scenarios is not changed by editing the NH3 emission rate.
Contrary to the marine eutrophication potential, total impact on terrestrial acidification decreases if the
NH3 emission rates decrease. NH3 is a main contributor to terrestrial acidification. Therefore, the impact
potential decreases if the NH3 emission decreases. The ammonia stripping scenario decreases less than other
scenarios. In this scenario only a small share of N is applied in the regular way, the rest is converted into
mineral fertiliser. For the sensitivity analysis with high NH3 emission rates (Table 2), mainly rates for the
solid fraction and compost are higher than in the main model. The emission rate of liquid fractions is lower
than in the main model. The relatively low sensitivity of the screw press scenario to high NH3 emission rates
is due to the relatively large amount of liquid fraction in this scenario.
Table 3: Changes in marine eutrophication potential and terrestrial acidification potential after sensitivity
analysis for field NH3 emission rates compared to main model.
Marine eutrophication potential Terrestrial acidification potential
Low High Low High
Reference Scenario 34% -10% -28% 8.4%
Screw Press Scenario 44% -1.5% -27% 2.5%
Screw Press + Composting 46% -3.7% -29% 5.1%
Centrifuge Scenario 45% -4.8% -28% 4.8%
Centrifuge + Am Stripping 13% -13% -10% 10%
3.2.3. P loss rate (field)
Changes in the loss rate of P that is applied to fields only influence freshwater eutrophication. The influence
is large, also with minor changes to the loss rate. As in Nielsen and Wenzel (2007), the sensitivity
570