Agriculture Reference
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In the other hand, Macedo et al. report only 50 kg N · (ha · y) 1 , in the case of no burn-
ing practice and residue restoration, or 0.70 kg N · t A [8, 25]. In absence of more infor-
mation to explain this discrepancy (is sugar cane a N fixing plant?), N input is assumed
to offset losses of N in bagasse and minor ones at the field. Other data of Macedo et
al. are used, 0 . 50 ± 0 . 10 kg K 2 O · t A for potash by taking into account all residues, or
35 ± 10 kg K 2 O · (ha · y) 1 , and 2.0 kg ai · (ha · y) 1 of agrochemicals.
Farm energy requirements per unit of total area dedicated to cane culture are
slightly lower than those for beet culture. However, as ethanol yield from cane is
117 GJ LHV · (ha · y) 1 and 1.65 GJ LHV · t A , the farm contribution is equivalent to 11%
of ethanol LHV and, consequently, larger than in the case of beet. It results from the lower
yield of ethanol from cane, itself due to smaller sugar content (Table 3).
Transportation and distribution consumptions are dependent on distances and modes
but little on differences of characteristics between both plants [14]. The recent construc-
tion of a pipe network and hubs to collect and store ethanol from distilleries [36] will per-
mit substantial gains of efficiency for distribution by comparison with carrying ethanol
by tanker trucks. Currently, it can transport ethanol from mainland distilleries to a refin-
ery of Petrobras petroleum Company in Paulínia, at about 100 km from the city of São
Paulo and 150 km from the cost. This last leg of the pipe is also planned. Average to-
tal distance from a distillery to coastal port is assumed to be about 650 km [36]. From
pipe specification flow velocity ranges from v = 0 . 90 to 2.0 m · s 1 , i.e. expected values
for pipe transportation [14]. Assuming diesel - or ethanol - fueled compressors with an
overall yield of 25%, fuel specific consumption to offset flow friction in pipes is around
r pipe = 0 . 050 v 2 MJ LHV · (t OH · km) 1 . Hence, r pipe = 0 . 12 v 2 % of ethanol LHV. The
last leg to a refueling station is probably achieved thanks to a truck. Consequently, even
with v = 2 m · s 1 , consumption contribution from distribution represents less than 0.75%
of ethanol LHV.
The major and crucial differences with sugar beet industry occur at the factory, although
operations are identical.
The processes in a typical Brazilian distillery in 2006 were not as efficient as those in
French beet factories.
However, this situation is independent of the crop and it is in fact
improving [31, 32, 35].
On the other hand, because cane is cultivated in a humid tropical climate, its harvest is
spread over at least nine months [6]. It permits thus to reduce the conversion of raw juice
into syrup. Currently ethanol production is limited to the harvest period and syrup is just
needed to concentrate sugar in juice.
Furthermore, tropical climate permits higher crop yields. We have noted that cane
presents a lower sugar content per area and mass harvested (see Table 3); but its total dry
matter is much larger. Cane processing produces raw juice like for beet and about 150
kg DM · t A of a by-product, bagasse, made mostly of fibers. Because of its potential as fuel
(49% moisture, low ash content and LHV = 7.8 MJ · kg 1
DM ), it is burnt in a co-generation
system to supply at least all energy requirements of factory processes. Furthermore, with
modern co-generator (operating with superheated steam at 90 bars and 520 C such as pro-
posed by the Brazilian company DEDINI S/A) and efficient processes, factories can save
part of bagasse to generate in power mode alone electricity for the grid, up to 32% of ethanol
LHV.
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