ETHANOL FROM SUGAR BEET - Sugar Beets - page 10

As far as sugar beet is concerned, D. Ballerini indicated in 2006 on-going progress
to raise x OH from 70 to 80 kg · t − A [2]. With a sucrose content of 18% α OH amounts
to 0.86. This latter value is also reported in the case of ethanol production from sugar
cane [6]. Because of some losses of sugar during the first stages of plant processing (slicing
and extraction with hot water) and the presence of complex sugars, the yield is lower than
yields encountered in the case of cereals.
As a result, from the initial sugar content - 183 kg S · t − 1 A - 158 is converted into
ethanol and CO 2 gas. A small part of the difference, about 4 kg S · t − A , is left in
beet pulp, the first main by-product at the factory generated during the extraction of
sugar (http://www.tereos-coproduits.com/sites/default/files/uploads/FICHE_Pulpe %20bet-
terave%20deshydratee_EN.pdf. The document indicates the average composition of the
product). It corresponds mainly to insoluble residues, which, for most of them, are concen-
trated and dried. Due to its rich content in proteins and digestible fibers it is sold as a feed
for ruminants. Fig. 3 shows that pulp average content in the beet root is about 55 kg DM · t − 1

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on a dry basis.
Another part of the beet sucrose is found in the liquid effluent of the
ethanol distillation, or stillage (http://www.tereos-coproduits.com/sites/default/files /up-
loads/FICHE_Vinasse%20betterave_en.pdf). Parts of its dry constituents - pectin and ash -
make it better suited to organic fertilizer after its concentration. Assuming a beet dry matter
content of 25% and that all remaining sucrose after alcoholic fermentation is recovered in
the stillage, its DM is around 37 kg DM · t − 1

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4.3. Methodology. From the Processes to the Whole System

A process based method is used to assess the energy and other material requirements of
the ethanol industry (chap. 4 of [9]). It offers some flexibility and transparency about the
analysis on industry operations and their consumptions. It permits to gather data beyond
the beet industry, in fact in all industries where the same processes operate. Operation is
understood in the text as the goal, such as concentrating the sugar of raw juice, while the
process is the means, such as a multi-effect evaporator.
On the other hand, the method requires more technical and scientific knowledge, but
permits to better control potential errors or unadapted assumptions. It should make explicit
the technical and physical variables of the industry on which its efficiency depends, such
as sugar and ethanol yields and process specific consumptions, as well as their importance.
These information permit to discuss any improvement or constraints and physical limita-
tions, and to derive a long term perspective.
The energy requirement of the whole industry is reported per unit of its main product
expressed in LHV because of its use as a fuel. This specific requirement is called thereafter
the global rate R of energy consumption in J for 1 J of ethanol or J · J − OH . For convenience
consumption is also reported per tonne of beet as received at the factory (after cleaning). As
its TRS content and sugar conversion into ethanol have reached some limits - see discussion
in the previous Subsection -, the tonne of beet is assumed to always yield 2 . 15 GJ OH · t − 1

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This represents already a limitation.
The system is decomposed according to its main operations (see Fig. 2) and, within
each of them, their operations (see Fig. 4 for the factory). Level of decomposition depends