Agriculture Reference
In-Depth Information
emergy saving as compared to both model systems. M-Low is particularly
bad in this respect since it needs a larger area (Table 2) and thus more seed
potatoes to produce the required amount of potatoes (Table 4).
M-High has the lowest emergy use for irrigation with M-Low using
50% more and the case using twice as much. The latter is in the fi rst place
a consequence of that the case uses more water (3.6 × 10 9 g groundwater
and 1.4 × 10 9 g tap water) (Table 4). As the annual variation in precipita-
tion is not considered in the model systems, the higher use of water for ir-
rigation in the case system may refl ect that the studied period, 2009-2010,
was relatively dry, and for instance in 2008 the water use was 70% less.
In addition, tap water, which accounts for 28% of total water used, has
an UEV value twice as high as ground water due to the extra work that is
needed for pumping and treatment (Table 4).
Emergy used for soil enhancement is the biggest input to M-High
(Table 4). With 1.7 × 10 16 seJ it is more than four times higher than the
other systems. This refl ects that fertilizer is a valuable resource, and that
reducing the import of fertilizer is a key element in reducing emergy use
in agricultural systems.
The model supply chain needs a total of 805 L diesel (calculated from
Table 3) for HGV-transport. In addition, 932 L of gasoline is used for the
58% of the shopping trips done by car and 12.6 L of diesel for the 8% of
the trips done by bus. The total use of liquid fuels in the model supply
chain (4.5 × 101 0 J) is thus bigger than on-farm use of diesel in the culti-
vation phase in all three systems (Table 4). The total emergy use for the
distribution system is three times higher for the model systems than for
the case system.
M-Low has the largest contribution of local renewable fl ows as these
are calculated directly from the size of the farm (Table 4). Further, the
emergy indices (Table 5) reveal that, disregarding L&S, M-High has the
smallest share of local renewable inputs (8%). The renewable resources
contribute only with 0.08 seJ per seJ invested from society (EYR = 1.08).
M-low is in this respect a bit better than the case. The case on the other
hand provides the vegetables with the highest resource effi ciency (lowest
UEV or transformity) and is as such overall more effi cient than both model
systems (Table 5). This is especially true when also considering L&S in
which case the transformity of the case is 39% lower than for M-High.
 
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