Innovative Technology and Sustainable Development of Organic - 1.

Eutrophication, however, implies direct leaching of e.g. nitrate to the subsoil and water reserves, or
run-off of phosphate to surface water, and, therefore, is a local problem. For environmental problems
with a local aspect, environmental impact should be quantified per kg of product and per ha (Halberg et
al., 2005). In our case we concentrated on N, as in organic production the phosphorous balance
generally is close to zero (Hvid, 2008). The N-surplus per ha was 117 kg ha -1 in BAU, 116 kg ha -1 in
ANW and 80 kg ha -1 in ENV. The difference in N-surplus could be explained by differences in
stocking density among scenarios (see table 6, LSU per ha), as no manure was imported to or exported
from the farm. In addition, Olesen et al. (2006) showed that a high N-surplus per ha was associated
with a high GHG emissions per ha. In our study, we expressed emission of GHG emission per kg of
ECM, and we found no correlation between N-surplus per ha and emission of GHG per kg ECM
In this scenario analysis we assumed no import or export of manure. In Denmark, the maximum N
application from animal manure is 140 kg N per ha. Berntsen et al. (2004) showed that organic dairy
farms in Denmark, on average, import 24 kg N ha -1 and export 14 kg N ha -1 in the form of animal
manure. It will always be a possibility for intensive organic dairy farms to further intensify their
enterprise by extending herd size and exporting manure from the farm, in order to produce more milk.
However, they have to comply to the standards of grazing. To facilitate grazing, a Danish farm needs at
least 0.2 ha of pasture per MPU. The different levels of excreted N per MPU, as result of varying
production, complicate the estimation of allowable stocking density and calculations of obligatory
manure export.
Optimizing longevity of dairy cows can reduce GHG emissions per kg milk produced by 13%
compared to an average culling rates of 35% (Weiske et al., 2006). Culling rate assumed in ANW and
ENV was lower than in the BAU scenario. The expected positive effect of an extended longevity on
GHG emission per kg ECM in ANW was not achieved due to the lower annual milk production per
cow, and the fact that bull calves are kept on the farm for three months and storage of manure in a deep
pit.
A fixed feed conversion rate was used to estimate feed requirements for a certain milk yield per
cow. Feed conversion, however, depends on the level of feed intake. For each additional1000 SFU a
cow eats per lactation, the feed conversion efficiency drops by 6.5% (Kristensen and Kjærgaard, 2004).
This effect was not included in our computations, consequently production efficiency in BAU and
ANW were overestimated in by 6% and 2%, respectively.
The total amount of fossil energy used was clearly highest in BAU where energy use is expressed
per kg ECM, it was lowest in BAU and highest in ANW. Unlike high energy requirements for AMS
use in BAU (Rasmussen and Pedersen, 2004), energy use per kg ECM was low because feed
production on farm is low, whereas import of concentrates was high (BAU: 421 ton y -1 , ANW: 213.5
ton y -1 ). Energy use for storage, drying and processing of purchased feed was not included in the
analysis, resulting in an underestimation of energy use in ANW and especially in BAU. Energy use per
kg ECM in ANW was high due to the low annual milk yield per cow. The relatively high use of fossil
energy in ENV resulted mainly from the relatively high use of on-farm diesel to cultivate arable crops,
and to cut and carry grass, instead of grazing (BAU; 1492 MJ ha -1 , ANW; 1195 MJ ha -1 , and ENV;
1485 MJ ha -1 ).
Compared to other estimations of energy use per kg ECM (Cederberg and Flysjö, 2004; Thomassen
et al., 2008) the values calculated in this study were low. One explanation is that direct and indirect
energy used to process feed ingredients were not included in our analysis. Another reason could be that
in practice only very few farms use “raw” components as concentrates, whereas most buy standard
mixtures containing components such as soy beans and palm oil which have to be transported from far
away.
Thesis Frank W. Oudshoorn 101