Agriculture Reference
In-Depth Information
stems from the high added value of these products in a developed economy, whereas final
energy such as electricity and petroleum products must be cheap (see Chap. 3 of [9]). As
a result, share of final energy cost in the price of these equipment represents currently few
percent.
Notes about energy unit and other units Because a unit of energy such as J or toe gives
no indication about the form of the energy, which may be a source of confusion as each
form does not provide the same service, and for the sake of concision, units of energy are
accompanied in the text by a subscript. Thus subscript e stands for electricity from the main
grid, HHV or LHV stands for high or low heat value of a fuel, while subscript tot stands
for the total energy to produce a fuel from natural resource, including its high heat value.
Likewise, subscripts in units of mass and volume allow to distinguish different types of
matters: w stands for water to remove, A for beet root as received, DM for dry matter of
pulp or stillage, S for sugar, OH for ethanol, st for process steam, stillage for stillage and
beer
for beer.
4.4.
The Farm Operations
The beet culture corresponds to intensive and mechanized agriculture. Plant is sown in
April and harvested from October to December when sugar is most concentrated in beet
roots. The culture is rotated on cycles of 4 to 5 years with crops like winter wheat or
oleaginous plants to prevent diseases [10]. Intensive agriculture does not preclude of good
agriculture practices. In addition, beet leaves are left and stillage from ethanol distillation
is returned to soil to replenish soil organic matter and offset part of nutrient losses.
4.4.1.
Mechanical operations and diesel consumption
The diesel consumption of a tractor or an harvester is proportional to the traveled distance
for a type of activity. Hence the local rate r
mech
is expressed in diesel volume (in liter l)
required per hectare and per year. It fluctuates with soil nature and meteorology.
Operations with tractor According to a study in 2002 [11], from soil preparation at the
end of previous culture 15 tractor trips are made, consuming 165 l
·
(ha
·
y)
−
1
. Fertilizers
have to be brought at different times of the culture cycle. It is possible to reduce the number
of tractor trips to 10 with combined operations and tools, but a higher load increases the
consumption per trip. Soil preparation without tillage could better contribute to save fuel.
However, it is not adapted to beet with long roots.
Harvest A recent study by the Institut Technique de la Betterave ITB [12] indicates an
average consumption by harvesters of 50 l
·
(ha
·
y)
−
1
.
In total r
mech
= 215
l
·
(ha
·
y)
−
1
of diesel.
