Agriculture Reference
In-Depth Information
TABLE 5: Emergy indices for the case system, M-Low and M-High with and without labor
and service.
With labor and service
Without labor and service
Case
M-Low
M-High
Case
M-Low
M-High
Emergy Yield Ratio
(U/F)
1.01
1.01
1.01
1.15
1.18
1.08
Renewability (R/U)
1%
1%
1%
13%
15%
8%
Solar transformity
(seJ/J)
5.20 × 10 6
8.58 × 10 6
8.52 × 10 6
5.54 × 10 5
7.01 × 10 5
6.40 × 10 5
When disregarding L&S, the case system uses less emergy to produce
the total amount of vegetables sold compared to both model systems (Fig-
ure 4). This is especially due to a reduced emergy need for purchased seed-
lings and seed potato as compared to M-Low and a reduced emergy use
for soil enhancements as compared to M-High. In addition, the case distri-
bution system only use one third of the emergy used by the model supply
chain. However, the case has a substantial higher consumption of on-farm
fuel use and needs more emergy for water for irrigation (Figure 4).
The case-study farm uses signifi cantly more diesel in the cultivation
phase (Table 4). This may partially be explained by the tractors being less
effi cient than those assumed for the model systems. Another factor is that
the diesel use per area is more or less independent of the yields, which
means that high yielding crops tend to use less fuel per unit output. This
is clearly refl ected in the comparison of M-Low and M-High, but does not
explain why M-Low uses less diesel than the case system.
On-farm electricity use (Figure 4) consists of electricity use for on-
farm production of seedlings and offi ces (only for the case-study) as well
as for irrigation (only model farms). Disregarding electricity for irrigation,
the case uses signifi cantly more electricity than the model systems. How-
ever, the electricity consumption of 4350 kWh is still relatively small as it
corresponds to the average UK household (4391 kWh, [57]). The emergy
needed for electricity in the case system (4.5 × 10 15 seJ) is partly com-
pensated by the emergy needed for purchased seedlings in M-Low (3.1 ×
10 15 seJ) and M-High (1.7 × 10 15 seJ) (Table 4). The fact that 30% of the
seed potatoes are farm-saved in the case system results in a considerable
 
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