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

PARALLEL SESSION 2A: LAND USE 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
berg et al., 2007; Thomassen et al., 2008). Almost half the total GWP in the reference scenario stemmed
from methane in enteric fermentation (43%) and manure storage (10%). Fossil energy use accounted for 22%
of total GWP. Changing to an energy supply system based on renewable sources resulted in reductions of 29-
44% of total GHG emissions from milk production, with Scenario 1 giving the largest emission reduction,
and Scenario 2 the lowest. Avoided fossil fuel use was the largest contributing factor to the reduction in
GHG emissions in the renewable energy scenarios. The second most important parameter is the reduction in
methane emissions when manure was passed through an anaerobic digestion process before storage.
In the arable farm study, The GHG emission saving was 35% in the self-sufficiency scenario based on ley
(A1) and 9% in that based on straw (A2). There was less nitrous oxide from the soil in both self-sufficiency
scenarios compared with the reference scenario, but the impact on the carbon content of the soil differed
significantly, with a larger reduction in soil carbon content when straw was removed from the fields (Figure
2).
Figure 2. Disaggregated relative greenhouse gas emissions in the arable farm system. The bars above 0 are
net increases in GHG emissions compared with the reference, and the bars below 0 are net decreases.
5. Discussion
In both the milk and the arable system, it was found that the biomass resources available as residues on
the farm were sufficient for supply of energy for the production. There was consequently no need to reduce
the production of food products, or increase the land area needed for the total production system.
For the milk study, the functional unit was 1 l of milk. This seemed reasonable since the milk farm has
one major product. For the arable farm, the situation was quite different, with a number of products in a crop
rotation. Therefore a functional unit was selected based on the whole farm, and the functional unit was limited
to the energy supply to the system. In both cases GHG emissions are expressed as emission reduction
compared to a reference scenario, whereby the functional unit is less important.
We chose to include technologies that are technologically available at least at a demonstration level, but
not necessarily commercially available. This seemed most interesting, since there is little evidence of any
small scale biomass CHP technology being commercially available today in Sweden. In other European
countries with higher electricity prices and stronger incentives for small-scale electricity production however,
the situation is quite different. Similarly, for tractor fuel, the systems evaluated are technically possible,
but in most cases not commercially available. Both small-scale and large scale production of biofuels was
investigated, selected based on technical feasibility.
The self-supply principle was been applied as at a farm level on an annual average basis. The energy systems
have normally not been designed for a self-supply independent of existing energy infrastructure. In our
part of the world, there is an electricity grid that reaches vertically all citizens and all farms. It has therefore
been most relevant to investigate systems which are connected to the electricity grid, and where electricity
can be supplied to, and accessed from, the grid. Local electricity production has been designed to cover the
farm´s total electricity demand on an annual basis.
For gas, there is also a grid available in large parts of Europe. However, most of Sweden is not covered by
a gas grid. It is possible to use natural gas infrastructure also for biogas, but that requires cleaning and upgrading
of the gas, so it is not self-evident that available gas grids can be used for biogas. In most of our
research we have not assumed any existing gas infrastructure available for biogas. When we have included
AA1 A1
1
A2
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