Agriculture Reference
In-Depth Information
was 1 220 k
·
m
3
[3]. The agro-ethanol amount in 2004 was 225 k
·
m
3
, 60% of which from
beet [2]. Fig. 1 shows the different origins of alcohol and their evolution since 1994. New
production from cereals has been mostly dedicated to agro-ethanol. Hence we assume that
about 500 k
·
m
3
of agro-ethanol was produced from beet in 2012.
4.
Ethanol Production from Sugar Beet. Processes
and Energy Requirements
4.1.
The System: from the Farm Fields to Gasoline Dispenser
Ethanol production is still associated with sugar production, especially in the off-harvest
period. A by-product of the sugar crystallization, égout pauvre or beet molasses, is used
to store sugar extracted from beet during the harvest period.
The by-product produce by
dilution the liquor to be fermented during the rest of the year.
In order to compare with petroleum industry and because of the on-going trend to re-
duce the lower profitable sugar production, we examine here a standalone ethanol industry
operating all year round. This is achieved using existing processes. The main adaptation is
to concentrate part of the raw juice into a syrup to substitute for égout pauvre. The operation
of purification of the raw juice is omitted as it is not necessary in the case of ethanol produc-
tion. Purification and/or rectification after distillation are equally not included as it is only
required to produce alcohol for pharmaceutical or beverage purposes. These simplifications
also correspond to some energy saving.
Figure 2. From field to tank. Main operations and their flows to produce ethanol from beet
in France. Y
A
is the annual average beet yield per unit area.
Also indicated are ethanol,
pulp and stillage yields in dry matter per unit of beet tonnage.
Fig.
2 shows the main operations of this industry and their inputs and outputs.
The
main product is the anhydrous ethanol, which is mixed with gasoline.
We do not deal with the production of ethyl tert-butyl ether, which results from the
reaction of ethanol with a petroleum product, isobutylene (other names are 2-methylpropene
and isobutene), in order to better match gasoline specifications [2]. It is being progressively
discontinued, even in France where it has been mostly promoted [3]. Production of the
ether of alcohol is also more energy consuming due the complexity of the reaction, which
necessitates the distillation and recycling of ethanol. Beside, the whole operation takes
place at few refineries in south of France (close to Lyon and Marseille), subsequently far
from the beet fields.
