4 Results—impact assessment
4.1 Life cycle impact assessment (LCIA)
Figure 3 summarises the LCIA results (calculated in
SimaPro®). Feed production was clearly the dominant
contributor in almost all impact categories. Grow-out
farming was the only other important process that with its
nutrient discharge contributed the most to the impact
categories eutrophication and FWET. The nutrient discharge
from grow-out-farming was high but hardly modified river
water quality compared with that before sector expansion
(only 0.0005% of river water passes through the ponds, but
this leads to a 0.01% increase of nutrients in river water).
The small but visible contribution from grow-out
farming to HT was dominated by zeolite use and, to a
lesser extent, by lime use. Grow-out farming dominated the
total contribution to FWET, but its absolute contribution to
FWET was much smaller than to HT and MAET (Table 7).
However, HT cannot be compared with MAET and FWET
on the basis of absolute contribution, as that would imply
valuing them as equally important.
We analysed the impact data of individual farms by using
hierarchical K-means clustering. This resulted in two