Introduction to Sugar Technology

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INTRODUCTION TO SUGAR TECHNOLOGY

E. MOURIS

Revised edition 1984

DEPARTMENT OF CHEMICAL ENGINEERING AND CHEMISTRY DElFT UNIVERSITY OF TECHNOlOGY INTRODUCTION

SUGAR TECHNOLOGY

E. Mouris

revised edition 1984

DEPARTMENT OF CHEMICAL ENGINEERING

AND CHEMISTRY

DELFT UNIVERSITY OF TECHNOLOGY I

INTRODUCTION TO SUGAR TECHNOLOGY

1. INTRODUCTION 1.1 What is sugar? 1 1.2 Properties of sugar 2 1.3 The sugar cycZe 5

2. HISTORY OF SUGAR 2.1 Sugar in the oZd 6 and new worZd

3. THE SUGAR PLANTS 3.1 Sugar Cane 9 3.2 Sugar beet 14

4. SOURCES FOR MANUFACTORING 4.1 GeneráZ methods 18 SUGAR 4.2 Sugar cane as a 18 source 4.3 Sugar beet as a 21 source

5. SUGAR PRODUCTION FROM SUGAR 5.1 GeneraZ 23 CANE 5.2 The processing of 23 sugar cane 5.3 By-products of cane 27

6. SUGAR PRODUCTION FROM SUGAR 6.1 The beet sugar 28 BEET factory 6.2 The manufactoring 28 -proces 6.3 By products of beet 50 6.4 Off-campaign 50

7. REFINING OF RAW CANE SUGAR 7.1 Sugar refineries 52 11

8. SUGAR t.fARKETS AND CONSUMPTION 8.1 Sugar distribution 55 8.2 Consumption 56

9. NEW AND OTHER USES FOR 9.1 Sugar as energy 57 SUGAR souraes 9.2 Sugar as alternative 57 souraes for the ahemiaal industries 111

The great sugar house was a wilderness of tubs and tanks and vats and filters, pumps, pipes, and machinery. The process of making sugár is exceedingly interesting. First, you heave your cane into the centrifugals and grind out the juice; then run it through the evaporating-pan to extract the fiber; then through the bone-filter to remove the alcohol; then through the clarifying-tanks to discharge the molasses; then through the granulating pipe to condense it; then through the vacuum-pan to extract the vacuum. It is now ready for market. I have jotted these particulars down from memory. The thing looks simple and easy. Do not deceive yourself.

To make sugar is really one of the most difficult . things in the world. And to make it right is nextto impossible. If you will examine your own supply every now and then for a term of years, and tabulate the result, you will find that not two men in twenty can make sugar without getting sand into it.

Mark Twain

"Life on the Mississippi" 1

1. INTRODUCTION

1 . 1. What is sugal'?

Crystallised sunlight.

Apart from water and the air around us, there is nothing quite as important to human life as sugar, for it forms the basic food for both plant and animal.

Plants manufacture sugar by the process of photosynthesis which is not dissimilar to the principle by which electric batteries in space vehicles are recharged by harnessing solar energy. This process, though much studied, is not yet completely understood, but it is known that plant leaves, by virtue of a green pigment called chlorophyll, use sunlight te create sugar. Recent studies have shown that the reaction takes place in minute plant cells called chloroplasts, which are only visible under an electron micrescope, the chlorophyll acting as a catalyst.

During photosynthesis carbon dioxide (C02 ) from the air and water (H 20) from the plant are combined to form sucrose (CI2H22011) with the release of oxygen (02) into the air. The reaction is simply represented by the chemical equation:

+ catalyst chlorophyll ------..-- C12H22011 solar energy 2

Sucrose, the chemical name for what is usually called sugar, is required by the plant in order to live and grow. lt can be looked on as crystallised sunlight which the plant supplies to man.

1.2. Praperties af sugar

Sucrose, C12H22011 is a disacharide composed of~-D glucose and,&~D-fructose (Fig. 1-1). lts use was at first restricted to the wealthy, owing to its early high price, but ancient Chinese doctors and those of other early people described it as a medicinal.

Today our syrups, elixirs, and pills are still compounded with sugar. Sucrose is said to be the first pure carbo hydrate to separate from the photosynthetic process. As such, it is the progenitor of all plant and animal sub stances and the origin of coal and petroleum, our principal sourees of heat and power.

For the purpose of establishing standards of identity for foods, the u.S. Food and Drug Administration has defined the term "sugar" as "refined sugar (sucrose)".

Refined sugar, whether of cane or beet origin, is the organic substance produced in pure form in the greatest volume, and is one of the purest of all substances pro~ duced in considerable volume. lts analysis is, approxi mately: sucrose, 99.90%: invert sugar, 0.01%: asb (in organic material), 0.03%: moisture, 0.03%: organic mate rial, 0.03%. There is a slight variation in the non- sucrose components between the cane refined an beet re- 3

1 HC -- -(/ --0 CH~OH 1 I, I, HCOH - j! -C--- I 0 I HOCH HOCI·j 1 I HCOH HCUr! I I HC- HC- I I CH~OH

Glucoseteil r rucrosctci I S.lccharosc rI.;, D -G Iucop y ra nosi do-Il D-i ~u ~ to i u r:l nosid (Schreibwcisc n:lch F1SCHER-TOLLENS)

CH,OH

H OH OH H S:lccharosc (Schreibwcisc nam HA WOR TH)

Fig. 1-1 Sacharosse = Sucrose = Sugar 4

refined, but this is relatively insignificant. It is the material of greatest food value economically, in the sence that an acre devoted to the cultivation of sugar, whether beet or cane, is capable of producing more calories than any other food erop. It is the cheapest souree of calories known. However, sugar is all energy (Joules ) and contains no proteins, virtually no mine rals, and no vitamins, which must come from supplementa- ry diet materiaIs. 5

1.3. The s ugar c ycZe.

When man consumes sugar his body needs oxygen to convert his basic fuel, blood sugar, into energy and in the course of this reaction the body liberates carbon dioxide, which is exhaled, whereas the plant inhales carbon dioxide in order to live and grow and exhales oxygen. The process of sugar consumption is thus the reverse of sugar forma tion and is represented by the equation:

11 H 0 + 12 CO C12H22011 + 12°2 ~ 2 2 (Enzyme) + (energy).

An enzyme is a natural organism which enables such changes as digestion to take place. Sugar thus moves in a natural cycle, beginning with its formation in plants and completing its course with its consumption and use for growth, the renewing of celIs, and providing energy for all our activities. Sugar is made by most plants but not usually in sufficient quantities to be harvested commercially. It is obtained from the maple tree in Canada, from sorghum, from certain palm trees and from the carob tree, but the two principal sources are: a) sugar cane b) sugar beets

The biology, history, cultivation and extraction will be described in the following chapters. While these plants provide sugar, their harvesting is not as simple as th at for example of wheat, barley or fruit. The sugar has to be extracted using technology which has been developed over centuries. 6

2. HISTORY OF SUGAR

2.1. Sugar in the oZd and new worZd

Sugar has been defined by chemists as a substance which is soluble in water, has a sweet taste and is capable of fermentation. The culture of sugar started at a very early period, sugar was known in India and the Orient long before the Christian era. The Greeks and Romans knew of the existence of sugar cane and probably of crystallized sugar, but the first positive evidence of sugar in solid form dates from Persia about A.D. 500.

So, in Sanscrit, sugar is called sarKara and the word candy is also derived from the Sanscrit kanda.

The practice of sweetened food also dates from an early period in world history and antedates the knowledge of sugar. In Northern Europe sugar came into use as an article of food during the time of the Crusaders, but does not appear to have been generally known prior to the middle of the thirteenth century. In 1148 the sugar cane, which had been brought from Asia, was exten'sively cultivated in Cyprus. About 1505 it was introduced from

Cyprus to the West Ind~es.

The discovery of America and the introduction of sugar cane in the new areas resulted in the rapid deve10pment 7

of sugar manufacture. About 1600 the production of raw

sugar in the West Indies and tropical America was said

to be the largest industry in the world of that day.

Sugar refining is said to have been invented by a

Venetian, around 1550, who probably got the idea from

China, where the art of refining sugar and making sugar

loaves had been practised for centuries. The first

Englishman who described the method of crystall~zing

and purifying sugar was called Bartholomew, but the methods used were crude until the introduction of vacuum

boiling and decolourization by bone char around 1802.

So, many sugar refineries sprang up in the seaports of

Great Britain and Western Europe.

In 1605 the suggestion to use beets for making sugar was made by Oliver de Serres. He wrote a book on "Art of

agriculture and management of land" in which he stated:

"The beet root when boiled yields a juice similar to

syrup of sugar, beautiful to look at because of its vermillion colour". A German chemist, named Andrea

Marggraf, made sugar from beet roots in 1747, and some

fifty years later one of his pupils, Franz Karl Achard,

established a factory for commercial manufacture of

beet sugar.

It was not, however, until the English blockade against

cane sugar imports and the impetus given by the Emperor

Napoleon the First in 1811 tothe growth of the sugar 8

beet and to the discovery of the best methods to obtain the juice and to extract the sugar from it, that the manufacture of beet sugar became a practical proposition. Starting from 1830 the rise of beet sugar manufacturing was so rapid that within 50 years as much beet sugar as cane sugar was produced in the world. The overall world sugar production was for 1982 estimated at 98,5 million tonnesjyear, divided into: world cane sugar production: 61.9 million tonnesjyear, world beet sugar production: 36,6 million tonnesjyear. Consequently the proportion nowadays is: 37.2 percent beet- and 62.8 percent cane sugar. ("International sugar economie yearbook and directory", Lichts, F.O., enclosure, p. 31, Verlag Dr. Albert Bartens, Berlin (1983)). 9

3. THE SUGAR PLANTS.

3.1. Sugar c a n e .

Sugar Formation in the Cane. Sugar cane is like a huge grass which grows perenially in tropical areas. It reaches a height of 4 to 5 metres. The top of the cane is crowned by an erect tuft of short green leaves where the process of photosynthesis takes place and the sugar is formed in the chloroplasts from carbon dioxide in the air and water in the plant. The stem is divided into sections of 15 to 25 centimetres by 'nodes' or knots from which grow buds, concealed by long, drooping leaves. The outside of the stalk of mature cane is hard and golden yellow in colour, with spots of red and green, and inside it are softer fibres os vascu lar bundIes. In fig. 3-1 is shown the botanical structure of the stem. The vascular bundIes are tubatar channels(Fig. 3-2) within the stem which allow for the passage of plant food, dissolved in water, from the roots to the leaves, and also the movement of the products of photosynthesis from the leaves to the stalk for storage. The bud, situated at the node, shows clearly. If acutting is taken, including the bud, and planted in moist soil at a temperature of 19 to 220 C three major growth processes begin Fig. 3-3. First, the root primordia develop short 'sett' roots, enabling the plant to anchor itself in the ground and to absorb water. Secondly a shoot is iniated in the bud, and thirdly, a permanent root system emerges from the base of the budo This development uses the stored sugar for food and en~rgy until such time as the shoot can form leaves and the process of photosynthesis can begin in the gro wing plant. When the plant is established, the 'sett' roots become defunct and decay. ------

1)111': ! ~~ ! I ~1 JI\ 1\ 111 1 )11, ' , ~! I ,lil 1 ,"'I ~, 'I 1 1 11 1 )11:;1: ;1/;:11

,~\\\llrI' ; I!,f I/~ ,\ I' " , 1 I 1\~. I'" ,I ,.,dl

~~l))\\ll;::~ e \\f \\ 1 ll I, ,111 ' 1 1 1\1)' r'/'/I ,,' 11 1 I'jl' I, 111['I 'I

' I111I~ /1,\ \ . i: : ' 1'1 i: 11 I i11(1\ I ILL: I Ii 1I1 Cane cuttings or portions of the staik. As Two kinds of growth rings. Left, the growth planting material the cuttings are usually selccted ring is bent upward at the bud side of the stalk j from the growing-point reg ion of the cane staik. right, it is more or less horizontal and thus passes Af ter ]. P. MARTJl"J behind the budo After ]ESWIET.

~ o .- ,'- 3· 1 Sligar cane 11

VasculM bundies

Cor cracks

Bud furrc'N

Growth ring

Root band

Leaf scar (node)

Wax ring

Roet primordia

Bud

Corky patch

Growth crack

Fig. 3-1a Sugar cane ANNULAR ELEMENTS LACUN06 I)Q, AIR TUBE.. vESSEL

J I - I ,.' ',-, ,I - 1 1

A cross section of a portion of an H 109 ca ne leaf. After P. MARTIN SCLEREN CHYMA J. Magnification, X 274. PHLDEM {~:~~~D;'NI6~~fll PAQENCHYMA OR STORAGE CELLS INTER CEL LULAQ. SPACES Diagrammatic drawing showing the structllre of the vasclllar bllIldle anel sllrrollIlding storaJ~e cells in three dimcnsiolls. After J. P. MARTIN

.... Fig. 3-2 Structure of sugar cane N ~ w

lKS

.... and

CUnlNG

stoo ,

LK J.

....

fourth

AnACHMENT

STALKS

LEVEl

ter

stalks thc

eane

ORIGINAl

SECONOARY PP,IMAP,Y

GROUND TERTIARY

POINT

...

staIks

ll'

seeondary

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LW devclop.

fff

,~!::""

staIk,

portion

which

orders

'~'!F:...

from

primary

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the

staIks

•

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underground

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, sueceeding

The showing tertiary

anc! MARTIN

stool

cane

shoots

various

develop

primary

Sugar

thc

the

ncw

roots

from

3-3

and

staiks

planted, ..

buds _

develop

Fig.

Later,

MARTIN

lateral

roots

eutting P.

band.

the

shoot

eane

root

from

After

and

the

\Vhen devclop from orders shoot. 14

Cane does not need to be planted each year, for af ter it is cut the roots remain, and from these sprout fresh shoots which flourish and qrow, providinq the text year's crop. This process is called 'ratooning'.

Cane usually contains 10-15% o~ sugar and a canefield will yield anything from 45 to 90 tons of sugar cane/ha wi th is equivalent 4-.5 to 12 tons of sugar per hectare

3.2. Sugar beet. Sugar Formation in the Beet. Sugar beet (fig. 3-4) is a biennial plant which stores sucrose in the root during the first year of growni if allowed to grow for a second year the plant would use some of this sucrose in producing tall seed-bearing foliage. For sugar manufacture, therefore, the root is harvested in the first season. The sucrose is produced by photosynthesis in the green portions of the leaves of the beet. Atmospheric carbon dioxide is absorbed by the stomata (pores in the epidermia of the leaf). The carbon dioxide diffuses to the chloroplasts where, in the presence of adequate light temperature, and water content, the radiant energy of the light is absorbed to convert the carbon dioxide and water, through a complex cycle of intermediate products, into sucrose and other carbohydrates. The sucrose is translocated through the conductive tissues of the vascular system to the root, where it may either be retrained in storage cells or conducted back to other parts of the plant and utilised for growth. The picture of a typical sugar beet, below, shows the small rootlets remaining with the beet as harvested but the very fine tap root and root hairs reach about 2 metres belo~ ground level in suitable soils. Below the normal leaves and sterns, part of the growing beet protrudes above ground level and the presence of residual leaf scars serves to differentiate the crown of the beet from the root proper. 15

Sugar Beet (8ela vulgaris) Centimetres

.,~ 40

Petiole 30

Crown

Leaf scars 20

Root

\ \ \ , 10- Rootlets 'I

\ :. ( '. I \ o

Fig. 3-4 Sugar beet ______Kopf \ ______HaIS

Rübt-nwurulkörpPf

Schwanz

Abb. 1 Sldzzc einer ZuckeITÜbe

(Abb. entnommen: TuilIn. V., Z"ekel' ~ , .J~ 1I~:\1i1 Abh . .'i Vcrtl'itllng des Xylelllgewt·bt's in der RiitJe

Fig. 3-4a SUGAR BEET STRUCTURE. 17

Although the crown portion of the beet does contain some sugar, the juice from this portion is of low quality con taining a relatively high proportion of the reducing sugars, glucose and fructose, which would seriously interfere with the production of high quality crystal line sugar. At harvest, the beet are 'topped'to remove the leaf and crown portion which may be fed to cattie or ploughed in as green fertiliser. The tops from each hec tare of beet have a cattie feed value equivalent to about that of 0.5 hectare of kale. The root portion of the beet, as sent for processing, has an average weight of some 350 g to 800 g depending on growing conditions and soil type and contains some 50 g to 130 g of sugar, as weil as pulp. Each hectare of beet provides some 5 tons of white sugar. 18

4. SOURSES FOR MANUFACTURING SUGARS.

4.1. GeneraZ Methods sugar. In general there are two methods to manufacture sugar In previous chapters the two principle sourees, cane-and sugar beet, are already discussed. outputs In Fig. 4-1, an overall scheme show the in-and for manufacturing sugar from these two sourees.

4.2. Sugar cane as a course. Cane is a Tropical Plant In Sugar cane needs strong sunlight an abundant water. and some tropical areas natural rainfall is insufficient is neces irrigation either by canals or overhead sprays at times sary.Where natural rainfall is sufficient it is required. too heavy and in such areas drainage systems are reduce Tropical hurricans and cyclones can drastically is also the yield, drought can be most damaging and cane subject to insect pests. and sprouts Af ter eropping the root is left in the ground as again for the following year. This practice, known 7 years or longer 'ratoonir~', can be continued for 6 or annual and is one of the economie advantages of cane over crops. growing Planting is carried out with short sections of 11-18 cane Fig. 4-2. Plant cane is usually cut af ter from months. The yield of sugar per hectare varies 4.5 to 12 tons depending on soil and climate. rising Much of the world's cane is still hand cut, but harves costs are causing the introduction of mechanical usually ting. Just before eropping, the lower leaves are as close removed by controlled burning. The cane is cut are remo to the soil as possible. The top leaves, which Once ved in the field, may be used as cattie fodder. and taken cut, the cane is loaded into trucks or trailers direct to the factory. 19

CANE BEET

CATTLE FEED BAGASSE FUEL EXHAUST GASES EXHAUST GASES FACTORY FACTORY WATER WATER WATER I I I I I MOLASSES I I ~ I I RAW SUGAR. RAW SUGAR L ______.J REFINERY

WH I TE/SUGAR WHITE WHITE/SUGAR SUGAR MARKET

CONSUMER

Fig, 4-1 DIFFERENT SUGAR PROCESSES. 20

l' L ;\ :-.; T POP l' LAT ION ST U DIE S

" Can~ s~cd rlac~d 'cnd !O end' in m>rrnal planting at Victmias \Iilling Co" Philirrincs, !'laflling g o("l '1uality sc'cd in this rnanncr \\'ith ade'lu:lt~ suil m"isture or \I'ith \\'ater for irrigati" n rcsults in ade4uar~ stands and in sunstanti:d sa\'ings "f secd,

Fig. 4-2 Planting sugar cane

.", 21

4.3. Sugar beet a s a s ouree Sugar beet as a Temperate Zone Plant Sugar beet is grown throughout Europe, the United States, Canada and the U.S.S.R. For sugar production it is plan ted in the spring and cropped the same autumn. The seed is planted in rows at about 60.000 plants per hectare. Until the early 1960s each seed contained a number of germs and produced several plants which has, af ter sprouting, to be 'singled' down by hand to one, but since 1965 plant breeders have produced a monogerm seed which gives single plants. Other operations such as drilling, weeding and fertilising are carried out mechanically. Beet is subject to attack from a number of insect pests, of which the worst is the aphid, a carrier of a disease called virus yellows, which seriously affects the yield and must be controlled by spraying. The sugar content is also improved by application of fertilizer. It is never planted two years running in the same field but is rotated with cereals and other crops. Before the days of beet, cereals were rotated with mangolds and turnips but this was expensive in labour and the roots could only be used as cattIe feed. In the early days farmers had to be persuaded to change to beets. Whereas cane stores sugar in the staIk, beet stores in the root. Harvesting normally begins in mid-September and continues till the end of the year. Af ter this the beet is liable to swift deterioration if a frost is followed by a thaw, though in European countries the campaign can continue till end of December. Harvesting is performed entirely with machines which left the beet, top it and feed it into trailers. The green tops are used as animal feed. Af ter harvesting, the beet is either sent directly to the factory or stored in clampsunder straw at the roadside until the factory can receive it. 22

From small beginnings 60 years ago, sugar beet has become a major factor in European and U.S.A. farming. It is a welcorne cash crop and because of the nature of its roots, with their long thread-like rootles, it irnproves the quality of the soil. Yields od cereal per hectare have enorrnously increased by the introduction of beet as a rotation erop. 23

5. SUGAR PRODUCTION FROM SUGAR CANE.

5.1. Gene r a Z

Sugar cane deteriorates quickly af ter it has been cut and should be processed as soon as possible. A simple methode (still in use in under-developed countries) to manufacture sugar from cane is shown in Fig. 5-1. Capacity 1-5 tons cane a day. The largest factories can grind as rnuch as 20.000 tons a day. A erop lasts from 5 to 8 rnonths and is of ten called a 'campaign' .

5.2 T h e proce ss&ng o f s ugar can e

At the factory (Fig. 5-2), cane is cleaned of trasts and other unwanted matter and passes first through shredding knives to brak up the hard rind and expose the inner core. It is then crushed between squeezing rollers (see Fig. 5-3) under high pressure and sprayed with hot water. The juice from this station is heated and lime is added. This, af ter filtration in vacuum filters, leaves a clarified juice which is concentrated by evaporation. The thickened juice is boiled in steam-heated pans under vacuum until a mix or 'massecuite' of crystals and mother syrup is produced. The mixture is then spun in centrifugal machines to separate the sugar crystals (raw cane sugar) from the residual syrup (cane molasses). Some cane sugar is consumed locally but a larger proportion is shipped as raw cane sugar (not as cane) to rnetropolitan areas where the main markets exist. 24

Sugar eane

Transport

Size reduction

Pressing

Evaporation open batch

Storage in forms

Bourbon Callt Gur

Fig I 5-1 SIMPLE MANUFACTORING PROCESS I 24 a Bactas$'e Fi ! fr Q I ion Mud .------

f 1 ~cjQrt prep-aratJonHMil! station :J~~ef'Eval2.orar/on C;'ris/a/fizallón Cone Shredder PUf! tca Ion r-- Raw Ju/ce Tnin Jl/iC'e , ' I t ~qQr DÎEF-usion chrisf:at ..,- L----. ...-il Proce s Separa t ion 1'10!Qm?S BQ9'-Q sse

~------lAl I , Wa ter. Water vvQ rer 8!.flD c-al/on I-~----======-----I ------~~~Cono~nSor 1- . t L...- ____ .....J, ' Ref)Jse ~------1-- ... Lime ~ Mi/koLLime t Ca (ollh I cokes:---:---f P{Qné __ CO2 gases __ --.-J

8agasse SmokeExhausf anc! qj Fuef . Power station QSES

Low Pressure sleam

FLDfVSHEET CfJNE SUGAR FflCTORY ' .': 11 Molassts

r--~~s'~~ .~-~---~ l!;J ÇJ i LJ u~1 oe

~------~;~~~:t_-~~~~~_~~~I~~:~-=-~i Multt:llt-elletl haporalor A I /' 1 I1 ~II I n I I nd 1I : : ~I I hrsl Sece I GuÜ ~,ay I 11 1 bO~1 I - 1 I 1 11 : 1 I I t : f ti P j 11til '7 11 ~ 1 1 -, 1 1 1 :.J 1 1 1 1 1 / Vacuum Va~1Jum : Vatuum I I pan / pan pan I ( I I 1 I I I I -1-+ _~_J; _+_ .LJ

Syrup

' 5 I juice, 60?~ Sollds

.~ ~' Scums 112-16%~ SGi'~fl'ir'iff) t· • j 'd11 :< L-----~r' i ---- r .:;

Pre~sjuice I L-----rA~~ Ba&asse la boders

//,r- ----~------__ -_-_-~1\ / /,/ r- !,'~P:'- I I / / / I I C Cenlnlug.l, ti L--.::::...::::!:::-..--:~,.;,;,..,;RS"U::.E'..J'J 'B ë;n~lugall_s~ L C_____ Su,,, m.gm.~----- fOI seed M,ngl"

11 L-J ' . ~'=1Clil :3E1HIV I I Lc 11: raw fT? Mlled JU e < I ___ J I MII11I1gplant L ______J Commef(.Ial suga. Frnalmolasses

Flow diagram of !t Tnw-sugar fadory (J> pre,:illre; Vac VaCIIIIIl1; T (empcratmc). N lJl

Fig. 5-2 Processing of sugar cane FLEDING Ol' MILLS AND CONVEYING Ol' BAGASSE ~--- \\

Conlinuous pressure feeder (Walkers Ltd.).

Fig. 5-3 Cross section sugar cane mill N 0'1 2 7

5.3. By produet s o f Ca n e

Molasses is converted into rum and baker's yeast and into cattIe food. 'Bagasse', the residual fibre of cane, is mainly used as fuel in the factories. Some is converted into paper and building board. Mud from the filters is used as fertilizer in the canefields. 28

6. SUGAR PRODUCTION FROM SUGAR BEET

6.1. The Beet Sugar Factory

and a beet There are resemblances between a cane factory whereas factory. Both extract the sugar from a plant but beet sugar cane is a tough, intractable material, sugar by is relatively soft and its cells could be destroyed cane. crushing. It has to be treated differently from from There are also differences in the raw juices obtained the the two plants although the end product is precisely same. Compare page 24 a and page 30.

6.2. The manufacturing process.

does It should be emphasized that a beet sugar factory not really manufacture sugar; the sucrose is synthesized by process of nature in beet roots and the so-called manufacturing process is essentially one of separating various the sugar, eventually in a pure form, from the roots. materials with which it is associated in the beet Fig.6-1, The process may be described by the block schemes 6-2 and the flow sheet illustrated in Fig. 6-3. complex From this flow sheet one can see that a long and from processing is required for the production of sugar from beets. The actual "season" or "campaign" is short, of mid September until the end of December, a period

about 80 days. Beet sugar factories work continuously and during this period, the processing going on day night.

a boiler Although not shown in the flow sheet, there is

house, power house and its attendant auxiliaries. and Much stearn is used as weIl as plenty of water and large supplies of coal, oil or natural gas, coke

limestone are also necessary. 1. beet reception and storage 2. water treatment f'-'- '-'-'-, --+---'--'-'1 3. juice extraction and - I . purification 8EETS 4. evaporation 5. cristallisation I L .... _ . -'-l 6. sugar house SUGAR I 7. pulp drying .. 8. lirne kiln FUEl FUEl FUEl 9. steamboiler and power station.

WATER

PROCESS CONNECTION ---- DISCONNECTION POSSIBlE POWER _._. - ' - VAPOUR OR CON DENSWATER

Fig. 6-1 - . A bloek seheme of a sugar faetory. IV '"

L--_ _ __ _ Deunp J Brandstof. Dror;1erlj DrCX)? pulp Na/Ie SchUimaarde. pulp Do.rnp -- 1 , 1 Wa'Ssen D if'fuS ie Sap- • kri~tQ.L- Bieten en I-- r--- Yerdamping' ~ - Snijden r-- ,oroce~ Zuivering' r- proces 5njdseL Ruw- I Dun- .n,-k- sap I Sap Sap

~ eentriT' Su/ker Slib Water +- I .Dro9'en !'1efa.5se j

Na./er I ...... , Wa ter- Co,.,densor Na ter - beho.nol. I I I I -SLib Ca.Or~O=ka.lleme!k /(a!ksleen I kalKollen C02 g'as ~ cokes - r----- ~ ------Hele g'a55en r . Sit>OrnkeleL ./' Bron cis 10 + . 1. - een/rede k0 ~ -stoom-

Fig, 6-2 FLOWSHEETBEET SUGAR FACTORY, 31

BEET SUGAR

Beets I ScaJes I Recelving station . I To factory bins, or long· term storage, Stone and trash removers CaO WJ~her or Sli~ers sacchJrate I Pulp flrcss water Water __ Difluser------, ca Ke J Ddf~slon I JUlce IW"~'" ! Screens Presses I First _CO. carbonation . I fvlolasses. I +-conc Steffen Clarifier L---r--~: fdtrate I Driers I I F irst I Standard liquor and second Mo lasses a I I C.Jrbonatlon I I carbonat Ion i dried pulp I Juree : I press cakes Second Storage. CO, --carbonation I use, Filters sale

·To lime or saccharate or milk recaJcine(1 Filters

Evaporators Intermediate and raw Thick jUi~e sugars filter aid Melter Fil:ers Cake, to .first -"7"-.J==~- carbonatlon ~ ~ ____._S_lu,dge ~H~i~gh~~~----~~L~o~w~ Low High green ~ wash green White pans wash ·Intermediate Raw pans I I pans Mixers Mixers I I Mixers Crystai I i zers Centrtfuges· I Centrifuges Centrifuges

Drier I Granulators To melter To melter Storage Condit'ioning 1 To· pressed Scre~ning pulp, Storaq'c bins Stetten ~ process To spec ialty or sale manufJcturing, packJgrng, or bulk sa Je

Fig ~ 6-3 Flow sheet beet sugar factory 32

The power absorbed varies between 140 and 180 kW per 100 tonnes of beet worked per 24 hours. Water use averages from 800 to 1000 tonnes per 100 tonnes of beet and 4 to 4.5 tonnes oil or 6 to 8 tonnes of coal on the same basis. ["Notebook - sugar course 1958", Mouris, E., p.10 to 24, School voor Suikerindustrie, Amsterdam (1958).]

6.2.1. Sugar beet supplies.

Growers deliver their truck loads of beets to beetrecei ving stations located either at the factory or at conve nient rail side locations in the harvesting areas. At the latter, the beets are transferred to railcars or transport trucks for shipment to the factory side. On arrival at works, beets are weighed and tipped into silos or flumes.

6.2.2. Beet preparation for diffusion.

6.2.2.1. Beet pumps pick up the beets and drop the roots into a washer. This washer consists of an open, perforated trough with revolving arms. Earth, small rocks, stones etc. are removed. Af ter washing, beets are lifted by bucket elevators to the top of the building, where they are deposi ted in supply hoppers over the beet-slicing mechnisms.

6.2.2.2. Beet sugar manufacture requires cutting of the beets into slices offering a large surf ace when being in contact with the water during extraction, conventionally known as the diffusion process. Slices of beets are called "cossettes", measuring 0.075 to 0.10 m in length at about 3 mm thickness. 33

Fig. 6-4 Overall vieuw beet sugar factory

Fig. 6-5 Beet washer 6.2.3. Diffusion.

The sliced beet from the beet slicers are, af ter

they have been weighed, immediately run into a

continuous diffuser. The sliced beets are propelled

up into a diffusion tower (system BMA = Braunsch- weigische Maschinenbau Anstalt, or Buckau =

Buckau R. Wolf) or in a long trough with perforated

plates (system DdS = De danske Sukkerfabrikker).

Hot water enters at the top or upper end, flowing

down countercurrently to the direction of the sliced

beet movement and leaving the separator or lower end

of t.he diffuser as diffusion juice or raw juice. The

sugar depleted sliced beet leaving the upper end of

the diffuser is known as pulp. During this process

water and juice are heated by heat exchangers for

better extraction. Fig. 6-6 and Fig. 6-7

6.2.4. Diffusion juice or raw juice.

The raw juice is light grey in colour, slightly

acid, containing about 12 to 15 % dry substance and

about 88 to 90 % sugar per 100 parts solid in the

juice.

6.2.5. Juice purification.

6.2.5.1. Milk of lime to neutralize juice and precipitate

some impuri ties. Jui-ce is stirred for some time

before being passed on to the next process.Fig. 6-8.

6.2.5.2. High tanks containing raw juicé through which CO 2 is pumped.

The CO combines with the lime, CaO, to form 2 Cac0 , which is 1nsoluble. The gas is allowed to 3 Beste Frischwasserverteilung: <;lrnmlinienlörmige Rührarme rotier!!!de .Q.~senberieselung kein r ransport, daher Anpas sung an alle leistungsbereiche Abscheidung von lult ohne Drehzahländerung und Gasen schützt nur durch Niveaueinste"ung 11. -- '! F'.. sc h wasserzu fhu r den Turm vor Korrosio:1 L-- .. - '----"-- . '._--

Schaumzerstörung ~-- --- ohne Schaumöl ~ Zulührung von entgastem PreBwasser (BW-PreBwasser l' entgasung) ------Abgeschiedene interz:"ular~--- , ~ '. ~ Gase verdrängen luft- ~, sauerstoff aus den Schnitzeln " ", -~ ''''-, Beste PreBwasserverteilung durch rotierende Rührarme

.~ Schnitzeleinlührung oh ne Schaumerzeugung "" .. _~ ~ ". G1eichmäBige Gegenstrom ". führung von Schnitzel und Saft. Höchste Schnitzelfü"ung BW-AUSLAUGER erzwingt schne"sten Saltdurchlauf lultabschluB durch hohen Flüssigkeitsstand Für 200 bis 5000 tato Einze"eistung im Schnitzelschacht

" leitflügel von absoluter ---"~- '-" Betriebssicherheit , '",Keine Schnitzelstauungen Abspülung der anhal tenden Erdbakterien

~ ___ _ S_i_e_b.:..p_a_ra_I_lele Schnitzelaulgabe

Rohsaftabgabe Einwandfreie Siebreinigung durch selbsttätig sich einste"ende Siebabstreiler

Entsandung in der Gasarme Schnilzelmaschine - Aulbereitungsanlage ' _ lange lebensdauer (/ ' ------.-- .. _-._-- -- _. ---./' -- I I Verstoplungssichere Regelung l!.u!~~~ftent~~ndungder Pumpenleistung bei konstanter Drehzahl L- --_._._ .. _--_. ---_ .._ .--- W

'è~\

Fig. 6-6 Diffusion process 36

Ul )..1 Q) ~ o +J o~ . ~ Ul :::l 4-1 4-1 .~ Cl 37 '~/'tsleen Coke S . • ~-

~ J;e6ranc/e ia/k - -- Water - la!kme!k I _ :-- r _____~~c~'O~2. ~ ...:... /"Car60na. - -Ia.fle

Ala-fillra~e I

Ontharde" Fig. 6-8 JUICE PURIFICATION. JJunsab 38

bubble through until the lime content of the

juice is reduced to about 0.1 %.uCarbonatation~

thickens the juice and a good deal of scum is

formed by the precipitation of organic irnpurities.

Some authors use the word "carbonation" but on the

European Continent and in the United States of

America the word "carbonatation" is generally used.

Por example Oliver Lyle also used the word

"carbonatation" in his book ["Technology for sugar

refinery workers", Lyle, 0., p. 26, 58, 304,

Chapman & Hall, London (1957) J. Also the "Glossaria interpretum" ["Glossary of

sugar technology", Müller, C.A., p. 20 to 21,

Elsevier Publishing Company, Amsterdam (1970) J

gives the same meaning to this subject.

6.2.5.3. In order to facilitate filtration, carbonated i juice is heated to 950 C and filtered in filter

presses or in vacuum drum filters, which remove

the sludge containing caC0 and non-sugars 3 precipitated during the first carbonatation

process. The juice has a light yellow colour and

still contains a slight surplus of lime in solu-

tion. It is, therefore, subjected to a second

carbonatation process with carbon dioxide and the

precipitated CaC0 is again filtered off in 3 filter presses. 39

6.2.5.4. 8ulfitation.

The resulting juice undergoes a treatment with

gaseous 802 (sulfitation) for additional decolour

ization and is again filtered in filters. The

resulting light-yellow juice (thin juice) contains

approximately 15 % dry substance. This dry matter

consists bf 95 percent of pure sugar and 5 percent

of non-sugar.

6; 2.6. Evaporation station.

Triple or quadruple effect evaporators are used to

remove the excess of water in the thin juice. Fig. 6~9.

They work as follows: The first evaporator is heated

by exhaust steam from the turbo generator, which,

on giving its heat to the thin juice, condenses. The

steam produced from the juice passes over to heat

the second, the process being repeated for the third

and fourth if used. BecausBof the heat given up to

the next, the condensation of this juice steam pro

duces a lower pressure over the juice, thus reducing

the boiling temperature of the juice.

The juice leaving the last evaporator is called

"Thick juice" and has 65 % dry substance. The dry

substance consists of 94 percent sugar and 6 ~ercent

of non-sugar. 40

:\1,1>, -; Scht'lIla t'iner \'ierslufi~l't1 \ 'enlalllpferallla!.!t·: "I \'orwiirJllt'r riir ,'inZlldick,'ndt' Lii"UIH(, bi KOlldl't1sat-I'\lInpt', c) Pumpt' zum Ab7.ieht'1l dl'r ,'ill:(edit-kten Lü,ulll( Di" ~, 'iltlfe II\'} arl>l'itet lInler \ 'aklllllll, \ Entnollllllen: l ' lIlllanll. Etlz. d. tedm, Chl'lll .• \liilld\l'n t1l1d Ikrlill, Bd, 1. Ul.5l, S, ,,) :3S)

condensor

l -, I steaffi I I 1 I 1 I 1 I I I L----r-~ I I I I I I I I I thin juice i I I Ithick juice .-JL -'- ~ L ___ ._-.-J 1... __+ .- -+- -~ t condensate +

Fig. 6-9 Four effect evaporator 41

Fig. 6-10 Juice heaters.

Fig. 6-11 Evaporator in a sugar factory. 42

6.2.7. Crystallization.

The thick juice from the evaporating station and

melted liquor from the intermediate sugar- and low

grade (affination) sugar melters are mixed; filter

aid is added - usually diatomaceous earth - and a

briqht filtration follows. The filtered liquor,

or standard liquor, provides the feeding material

for the vacuum pan boiling of the first or A-product.

Vacuum pans usually are vessels with conical bottoms

containing steam coils. The pans are connected to

acondenser, 50 that boiling is carried out under

vacuum. The content of a vacuum pan is called masse

cuite and consists of a mass of crystals (50 %) and

of mother liquor. The massecuite is discharged into

a mixer tank for temporary storaqe to supply the

centrifuqes. ·' Fier. 6-12

6.2:8. Centrifuges.

Separation of suqar crystals from massecuite is

done in centrifuqe~ which are rotatïnq rapidlv

(about 1000 rpm) ~ n vertical drums with perforated

side walIs. In the centrifuqes the suqar is spun

free of syrup and is then briefly washed with hot

water. This suqar, af ter dryinq and screeninq, is

the final product: white qranulated suqar. 43 ~--~ JJa.mjJ naar CondenSDr

D/~SQ.é ---~ kook.pan

~9~mollen ju/ier of siroop

110.1Q. X eu r ( koel. trog' )

Centrifuge

sIroop

suiker

Fig, 6-12 SIMPLE BOILI~G SCHEME, 44

6.2.9. Intermediate or B-suqar.

The syrup spun off the white or A-suqar centrifuqes

is known as "high- or A-syrup" and provides the

vacuurn-pan feed for the second or intermediate

boiling. The intermediate boiling process and con

tents of the vacuum pans is also known as B-masse

cuite. The centrifuqinq of the intermediate- or

B-massecuite provides B-suqar, one of the two

suqars which, af ter meltinq, is used to make .

standard liquor.Fig. 6-13

6.2.10. Low qrade- or C-suqar.

The syrup from the intermediate centrifuqes pro

vides the feed supply for the third or C-crystal

lization process. The massecuite from the C_vacuum

pans is held from 16 to 50 hours in crystallizers,

where the temperature is qradually lowered, allow

inq time for the slow rates of crystallization in

this low purity material to crvstallize out all

the suqar possible. The C-suqar from the centri

fuqes becomes the other part of the standard

liquor, while all of the syrup spun from the C

massecuite is called molasses. The molasses con

sists of 20 % water, while the dry substance has

60 parts of suqar and 40 parts non-suqar. 45

Thick juice 27 t/60,5

H.A.Syrup 3t/75 Remelted sugar 15,6t/65

vapour to condensor 13,7t..----- Massecuite 31,9t/90

1n1i te sugar 13,1 ti 100 H.B.syrup 3,3t/75 A-syrup 17,7t/75

vapour to condensor 3,5t .----- mixer Hassecuite 17,5t/91

lvater I, 3t --- B-su a r 7 6t 9 5,4 t water r-___~~~B--~s~v~ru~n~~5t/75 6,4t/75 vapour to condensor 1 ,55t'---- - lIassecuite 6,151 3

Molasses 3,8t/84... ~ ____ ~ I----~ C-sugar 3,36t/98

syrup 2,3t/75 Aff.sugar 2,6t/98

Fig. 6-13 A three sugar boiling scherne. 46

6.2.11. Final granulated product.

The granulated white sugar is bagged or stored in

silos for later package or bulk sale. It is also

possible to manufacture liquid sugar and powdered

sugar from the granulated product. Generally there

has been more use of large scale storage of granu

lated sugar recently.

6.2.12. Power and steam.

6.2.12.1. Steam consumption.

Sugar factories nowadays generally are equipped

with water-tube boilers of various types. These

aresimple in comparison with boilers in large

modern steam power stations. They normally will

have superheaters and economisers and will be

fitted with furnaces for burning oil, natural

gas or coal.

Large quantities of steam are used for juice

heating, for concentration of the juice and ' for

boiling of the massecuite. For the main purposes

only low-pressure steam is used, which can be ob

tained as exhaust steam from back pressure tur

bines supplemented by reduced live steam, or as

vapour from the evaporators. Fig. 6-14, and Fig. 6-15.

While in old-fashioned plants of ten 60 tO 80 ton-

nes of steam per 100 tonnes of beets are required,

modern plants nowadays require only 35 to 40 ton- .

nes and even this figure keeps on falling. 47

Simultaneously, there is an increase of power,

requirements in connection with mechanisation,

automatization andwater .purification systems.

6.2.12.2. Power consumption.

It is considered that the power required for pro

cessing 100 tonnes of beet per 24 hours in a

modern sugar factory is: 180 kW in plants proces

sing between 1,500 tonnes and 3,000 tonnes of

beet per 24 hours and 150 kW in plants processing

more than 3,000 tonnes of beet per 24 hours. hj I f-'o ~'EA""UUILlH~<..D: l.Q INT(RN LO !.!> fS I . I t"'"""" 0\ I ..... ';=-

SRuBSEAWA TER TAAN SPQRTATI Q N ~ H 4fL05SES ';ILN 1 ..._r. TllAt~l 0> ___ ~ 0" ~ATlO SS(S C;~V(RSIO' r-' M IUUlIM[ l~ MllK OF lIME CO2 G.~

a [)(HAUS T wET PUlP Ul GAS 'VAPOUR H AT lO S SES ...... , lAANSPQRTATION ""U :u % ~ PAESS WA TEA l () 0 '" '" ~ ~ 0 0 z () Hl z z 0 .. 0 '"z rrl '" " O[NSEA g: :: ~ '" (f) '" 0 ~ ~ .. (f) (!) '" '" := ()E N S AT( .. ~ Hl'" losse!> ffi 'H le K )UIC[ rtPl C) Cl' .... 0 t.J

Hl ~A"OUH r-' ~ C ~ ~ ~ ~ ~ ~ ~ ""U m I r 0 r • n ~ ~ • ~ ~ • - ~ - m ~ 0 C,pNOENSE A Ilif AT IN nOCK lU Ier ~ ! ~~ ; ~~ p : ~ S:~NOf.NSAT( o ~ ~ 0 : ~ 2 D ~ ~ ~AT LOS!.ES (J1 ~ ~; a ~ ~ ~ ~ rrl Hf AT IN SUGAA ~ ~ ~ ~ :u ~ ~ Ul a : ~ ~! ~ (f) '"z .,.z c '"'0 s ; (J ~ ~ .. .. ~ ~ ""o '".. .. -i " " ~ Hl z TRAHSPORT.'ION I - WARM WATER Pl ..'" 0 0 Z .." ~ f-'o (!) ~ Ul ex> *" \.0

I I I I I I : I

I I

l J

-I

.VACUUM

(ë1l

ING

OIFFuSION PANS _

TRAN!)PQHT

BOilERS

TRANSPORT

HOUSE

STATION

----,

TRANSPORT

KlU'\!

DRY

GENERATORS TRANSPORT

JUICE

-1-

J • •

WATER • BOIllP4G PULP SLICING STEAM EVAPQAAtlON SUGAR BEET II

POWER 2 1 7 6

4 11

8 ~

,·-

______

PANS

1 19 1 I I

I I r

r~G

BOILI

5+9

I I

BPl!l

liP

WATER

~C02G

KILN

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BURNEO

LlME

UME

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COKE

STONE

sCJ

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j::-

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RJn

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seheme.

13 I I 1 1

; ~"'''-''-o,:

-,-

PELLETS I OR

heat

TS RJ

~--'--_ the

RJm OJm

~-~J:

PURIFICATION

VAPOUR 1---,.-----,,.--.-- of

EVAPORATOR

OlrFU~ION

PULP BPn

RJn OJn

FCJ

SCJn

-TJn

WATER

WET

ORYING

I I

PULP

division

GENERATION

~lURRY

POWER

STATION

! ~

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houst

STEM"BOILER.

cues

6-15

AIA

rUEl

AIR

FuEl

Fig.

r 19

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I I L I 50

6.3. By-products of beet.

By-Products of Beet The chief by-product is beet pulp, which is dried Fig. 6-16and mixed ' with beet molasses into pulp nuts, which have a wide scale as animal feed. Molasses, another important by-product, is used in many industrial processes. The leaves and crowns of the beet, which are cutt of during harvesting, provide valuable animal feed for many farmers.

6.4. Off-campaign

In order to enable more beet to be processes without additional equipment, some of the tickened juice is stored in huge tanks and the sugar from it crystallised af ter the campaign. White sugar is stored in 10.000 ton silos for marketing between one campaign and the next. During the off-campaign, people who work in the factory undertake repairs of the equipment, which must be able to work continuously day and night without a halt for

3~ to 4 months. 51

Pz.rSen Pe~JvateÎ naa.r dif/L1S'/e t DÎ en

8rano/slof - '20. Q7en ./)rood - .lJa.rnh I LtJcl~t -- frommel

çc~ooicle

~ pull:>

!3raK{es é.ersen •

0É.slaq' ~ q'w-~e pul;., ~ ~

Fig, 6-16 PULP SCHEME, 52

7. REFINING OF RAW CANE SUGAR.

7.1. Sugar Refineries

While sugar factories are located as centrally as possible in growing areas, refineries are invariably sited at deep water ports such as London, Liverpool and

New-York and in the past Amsterdam. This is to facilitate the reception of imported raw sugar ih large quantities

from ocean-going bulk carrying vessels. They also take in raw beet sugar delivered either by bulk trucks or coasters. The material entering the refinery consists of sugar crystals with impurities and a coating of molasses.

The outer layers are softened with warm syrup and the mixture, cal led 'magma', is passed into centrifugal machines, which are high speed rotating perforated drums, and which separate the syrup from the crystals. In the separation some sugar is taken off with the impurities and this must be recovered. In a process known as

'recovery' this syrup undergoes successive boiling under vacuum and centrifugal separation. The recovered sugar is melted and goes on through the refining process,

joining the washed raw crystals.

The final syrup, from which it is no longer economie to recover sugar, is called refinery molasses. AltholJltJh partially clean there are still impurities within the crystals which are now dissolved in water. The solution is treated with lime and carbon dioxide bubbled ih. The 53

resulting chalk precipitate traps impurities present in the 'liquor'. The chalky filter aid and impurities are removed in a filter press and the emerging liquor is now a clear amber colour. Next, the non-sweetening colouring matter and virtually all soluble impurities are removed by passing the liquor over bone charcoal or some other decolourising agent. The liquor is now clear and colour less.

The process of crystallisation and preparation for packing in a refinery is similar to that used in white sugar factories, i.e. boiling under a vacuum in large enclosed pans at low temperatures to avoid colour formation and the destruction of sugar by heat.

The recrystallisation of sugar has until recently been entirely a matter of human skill, the pansman judging the correct degree of supersaturation in the pan, inducing the formation of crystals by introducing a small quantity of 'seed' crystals and then continuing to grow the grain so formed to the requisite size before stopping the evaporation, breaking the vacuum and running off the

'massecuite' of crystals and syrup. Automatic recrystal lisation has now been developed to a degree where it may replace manis skill.

The crystals are, as before, separated from the mother syrup in centrifugal machines and dried in granulators.

While different sizes of crystals are normally produced by variations in boiling technique, there is always some variation in size and it is customary to grade the 54

crystals by screening before packing as granulated, by finest granulated or caster. Icing sugar is made by compres pulverising crystals in a mill and cube sugar sing moist sugar crystals in moulds and then drying. 55

8. SUGAR MARKETS AND CONSUMPTION

8.1. Sugar distribution

Most beet sugar is eaten where it is made, as is much cane sugar (e.g. in India), but there is a traditional trade in cane raws, on which many developing countries depend for external earnings. Markets for this generally lie far from the country of origin, and the sugar is shipped in bulk in large single-deck ships of 12 to

25,000 tons capacity, of ten owned by the sugar refiners.

These come alongside in deep-water ports and are either discharged direct into the refinery or, where such facilities do not exist, taken to it by barge or truck.

One of the reasons for this is economy. Another is that refining as near the market as possible enables control of quantity to be properly exercised for the consumer, and packets, which are easily burst, to be handled better.

Af ter processing the sugar is distributed, either in special bulk lorries to manufacturers or in packets to the grocer. Home-grown white sugar from beet is similarly distributed.

The sugar is sold to sugar dealers, retail organisations, and food manufacturers, a discount being given on quantity. Dealers purchase large tonnages which they sell to thousands of outlets throughout the country. Physical delivery, whether of products or of bulk, is undertaken by the refiners and the Sugar Corporations, storing in 56

depots throughout the country and having large fleets of specialised lorries. Certain manufacturers also purchase liquid sugar in bulk. Some, such as the pharma ceutical and soft drink industries, require specialised delivery.

8.2. Consumption

More than half the sugar eaten in the world is consumed in the form of manufactured foods - biscuits, sweets, jams, soft drinks. 57

9. NEW AND OTHER US ES FOR SUGAR

9.1. Sugar as energy sourees

Although it is natural to think of sugar as a food, and this is its prime use, since 1960 it has been studied as a natural source of many of mankind's modern needs. Such products as detergents, plastics and chemicals and so

forth have until recently been based almost entirely on crude oil, but the rise in price of oil may make it less economically attractive as a source, and in some cases,

for example, that of detergents, the product is under criticism from an environmental point of view.

Petro-chemical detergents are non-biodegradable, meaning that they do not break down af ter use and, when dis charged into a river or into the sea, affect the natural life in the water. A detergent manufactured from sugar or molasses is completely biodegradable and under no such disadvantage. The cost of the raw material is now approaching that of oil.

9.2. Sugar as alternative sourees for the chemical

industries

The plastics industry depends largelyon phenol. Oil prices have made this scarce and costly. Sucrose contains, like phenol, carbon, hydrogen and oxygen, though in different proportions and may provide an alternative. 58

Ethylene oxide, much used in the chemical industry can be made from sucrose, and although the economics of the process are not yet established it remains a future possibility.

In the past decade the chemistry of the sucrose molecule has been the subject of considerable study and many possible uses can be foreseen.

Microbiology has been applied to sucrose and its by

-products and wastes, and a number of new fields are being opened up. In particular the vegetable waste, bagasse, as weIl as molasses, can be converted by certain micro-organisms into a protein-containing cattIe food, which may help to increase edible protein consumption in developing countries which are short of cattIe because they lack the fodder.

Recent (1976) trials in feeding liquid sugar to pigs prior to slaughter have shown considerable improvement in the quality of the meat.

Sugar and molasses are also widely used in fermentations to prod~ce not only alcohol, but also such chemicals as citric acid, lactic acid and sodium glutamate. Itaconic acid, a component of same plastics, is produced by fermentation, while drugs such as penicillin and cephalosporin are the metabolic by-products of micro

-organism growing on sugar solutions. Yet others ''Convert sugar into polysaccharides or sugar polymers. Examples of these gums are dextran, a blood plasma substitute, and alginate which is normally obtained from seaweed and is 59

used in many products.

Several hundred thousand tons of sugar are used every year in fermentations, quite apart from that used in wine production and brewing. Sugar in all its forms is there fore a very versatile and important raw rnaterial.