A Feasibility Study of the Production of Ethanol From Sugar Cane

8/15/2019 A Feasibility Study of the Production of Ethanol From Sugar Cane

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PREFACE

For a period now spanning more than ten years, the Queensland

Department of Commercial and Industrial Development has sponsored research

and feasibility studies within the Department of Chemical Engineering of

the University of Queensland. A series of reports has been produced,

each concerned with some aspect of Queensland's Development.

The work has been carried under my broad supervision, generally

by research officers. Earlier workers who have produced reports in this

series include Mr. J.G. Job, Dr. P.J. McKeough and Dr. F.K. Mak.

When we accepted the present assignment to write a report on the

feasibility of producing ethanol from sugar cane, we had expected to

follow much the same procedure used in the past. However, at about

this time, Dr. F.H.C. Kelly visited the Department, and the possibility

of a somewhat different approach became clear.

Dr. Kelly is a man with very broad experience in the sugar industry -

experience in Queensland and overseas and in many aspects of the sugar

industry, which would be difficult to match. I invited him to work on

the project for the Department, and the report is attached.

I believe this will be a very useful starting point for consideration

of a massive expansion of the Queensland sugar industry to produce ethanol.

Others may prefer to fit alternative numbers to the various relationships

outlined or even to modify some of the relationships. If we have

provided a useful base from which to consider the alternatives, and if we

have caused others to think about better alternatives, I believe we will

have achieved our goal.

D.J. Nicklin9.11.77


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SUMMARY

1. A comprehensive study has been made of factors related to the production of

ethanol from sugar cane and problems related to its use in internal

combustion engines. All ethanol costs are "ex-distillery" estimates.

2. Cost estimates calculated for 25 sets of conditions range from 27 to 8c/l,

summarised in Table A and illustrated graphically in figure 4 with 12

relevant parameters.

3. Preliminary experiments with juice are deemed necessary at estimated R.6D.

cost of $100,000.

4. Highest costs are for distilleries associated with the present Queensland

sugar industry.

5. It is considered unwise to tamper in any way with the structure of the

present sugar industry for the purpose of obtaining low cost ethanol.

6. Full advantage should be taken of experience in growing sugar cane, control

of pests and diseases and of extracting juice.

7. If the sugar industry should wish to divert cane to ethanol production in the

event of failure of the export market this should be considered only as a

short term palliative.

8. Sugar cane grown in new areas specifically for ethanol would appear to have

good prospects for lower cost development if_ a new social and economic

structure suited to its own needs can be developed.

9. The social changes would include 7 days/week of operation for 39 weeks/year

for which 12 month employment conditions could be negotiated to cover

agricultural as well as processing areas. A suitable agreement with unions

would be a necessary preliminary determination.

10. An Industrial Alcohol Energy Authority should be established to oversee the

development and operation of the new industry with representation from

government and unions as well as producer and consumer groups.

11. Economic changes would include full mechanization of all agricultural

activities with programmed maintenance and 24 hr/day - 7 day/week operation.

This is not compatible with small farm units and the cost advantages of 1600

ha properties or 35,000 ha estates have been examined.


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12. Absolute costs are very difficult to estimate but the relativity of costs

is believed to be satisfactorily indicative. Cost evaluations have been

broken down to 12 main units and numerous sub-units providing a stability

to the cost structure. Thus for the lowest costing route at 8C/1 the

capital cost of the processing plant represents the highest cost component

at 26%. A 50% error in this figure would alter the overall cost by 1c/1.

13. Association with the present sugar industry could enable about 400 Ml/annum

to be produced at around 25.5C/1 with one distillery in each of the four

districts and using also all of the molasses produced from all of the mills.

Any increase beyond this could only result in a higher price for ethanol

produced within the structure of the present sugar industry.

14. Recent experiments in Brazil have indicated that ethanol can develop 18%

more power per litre than petrol but 15 to 20% more volume is used. A

compression ratio of 10:1 is needed to achieve these results. The Fiat

motor company in Brazil is prepared to make appropriate engine changes.

15. Logistic constrictions on the rate of development of a new industry in

Australia would mean initially blends with petrol in areas close to

production progressively extending through Australia. A 7 to 10% limit

is advised in high humidity areas (e.g. Queensland tropical wet season) but

up to 15% would probably be safe in low humidity areas.

16. Australia's present consumption of petrol of around 14Gl/year would require

seven Queensland sugar industry (QSI) units to supply the whole amount as

ethanol if only juice from stalk cane is processed.

17. If cellulose from fibre is hydrolyzed and fermented with 50% recovery and

whole cane (including tops and leaves) is processed only 4QSI units would

be needed.

18. A great deal of information is known about cellulose hydrolysis but not

with respect to sugar cane fibre. A research and development

investment of $2m specifically directed towards this objective is commended.

19. District area units of 35,000 ha or 0.1 QSI units are commended for new

area development, subject to qualifications relevant to item 15 table A.


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20. Capital costs for each new area are estimated to total approximately

$350m or $3,500m/QSI unit.

Carrying present knowledge of cellulose hydrolysis to a viable stage for

$2m could make the difference between a capital investment of $23,500m

or $13,500 m i.e. $10,000m. A R. & D. investment of $20m could well

be justified.

21. The average productivity in Te sugar/ha - season of the present QSI is

the best in the world, but Te cane/ha - season are only about 40% of

local well demonstrated achievable figures. Evolutionary improvement

is at the rate of 1.1 to 1.6% per year.

22. If actual average productivity could be increased to 80% of achievable

limit by wider application of already well known agricultural practices

this would double unit area ethanol production and reduce the number of

QSI units required to 2 or 3.5 depending on whether cellulose is

processed or not.

23. An establishment R.S D. investment of $llm is considered necessary

for such an achievement to be realised.

2*+. Since larger water supplies for irrigation would be required as well

as larger or more numerous processing plants the total capital investment

per QSI unit would be nearer $4,500m. The outcome of the $llm. R.£D.

investment would determine the real need or otherwise of capital

expenditure of $13,500m or $8,700m - again an investment that would

be well justified if it cost 10 times as much.

25. An establishment R.SD. investment of $3m is commended for developing

the requirements for optimum agricultural operations other than those

specifically relating to area productivity. This would have only

marginal influence on capital expenditure but would relate to a

difference in the price of ethanol of 5-8C/1 or $7-11,200m per year.

The initial gross benefit would be very much less but the manner in

which a new area development may be initiated will have long term

price influences.


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26. The possibility of growing cassava as a fallow rotation crop has been

examined. It would seem to have little influence on the estimated

cost of ethanol but would increase area productivity by about 10(±3)%.

27. If cellulose hydrolysis is practised it may be done either with or

without using coal as fuel. The estimated productivity and cost

differences are marginal but more capital is required for the ethanol

plant if coal is not burned. The pro-rate capital investment for the

coal plant and transport is probably about half of that required at the

ethanol plant.

28. If coal is used total consumption would be up to 4.3MTe per 14G1 of

ethanol or 3256 litres of ethanol per tonne of coal. On the other hand

the use of this tonne of coal has enabled only 1333 1 of extra ethanol

to be produced which is still favourable when compared to 300 1 of

petrol possible from the same tonne of coal by hydrogenation.

Producing ethanol from sugar cane by the routes described may represent

a net gain of energy varying between 10% and 64% according to the

constrictions applied.

29. The energy input for full mechanization of farming procedures is

estimated at about 1% of ethanol output.

30. Up to 90% of fertilizer requirements are expected to come from recycled

evaporated distillery slops. When coal is burned about 74% of the

heat from this source is needed for slops evaporation if looked on as a

marginal effort. A very costly fertilizer - but convenient. On

the other hand when processing from stalk cane juice the fuel required

is readily available from surplus bagasse and two disposals are

satisfactorily handled.

31. A R. & D. investment to study the thermal balance of the distillery could

conceivably reduce coal consumption by up to 50% and make the non-coal

route more attractive. The possibility of recycling slops to the

hydrolysis heap needs investigation. An investment of $lm could

ultimately be worth $100m/year but much less initially and not critically

im ortant until erha s 1990


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32. A levy of at least 1% and preferably 2% of the value of the product

is commended for R. & D. as a continuing investment.

33. A system of indexed amortization has been suggested to enable

development capital to be serviced at currently realistic rates

of interest.

34. Employment prospects are envisaged at 10,000 to 20,000 persons/14Gl -

year directly concerned in field and factory, generating supporting

employment 3 times this number. A similar number is envisaged as being

employed during development stages. Each district would have a

community of 6000 located in 3 sub-communities - one of 3000 and two

of 1500. These numbers relate to 1600ha property or 35,000ha estate

development. For 50ha farms an overall community of a million people

is indicated and believed to be too large a proportion of the nation's

manpower resources for a single product investment.

35. The possibility of applying space-age technology through remote control

has been examined and seems feasible with known technology. Complete

control could be effected from the Brisbane area reducing the need

for remote living to 1500 persons per district for maintenance and

operator-assisted duties.


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T A B L E A - S U M M A R Y

ITEM

1.

12'

[ 3.

4.

5.

6.

Dual production with raw sugar, from

stalk cane plus molasses from surrounding

district mills. Restricted to one unitper district. Table VI

Sole product from stalk cane at an

existing mill plus molasses from

district. Restricted to one unit per

district. Table IX

Mew area developed, Stalk juice.

Social change to 7 day-week, 39 week

season3 annual employment on farm as

well as factory. 50ha farms.

Table XVIII.

As for 3 - 1600 ha properties.Table XVIII

As for 3 - 35,000 ha estates

Table XVIII

As for 3 - whole cane processing

including cellulose - 50 ha farms

Table XIX

LAND1

AREA

QSI

UNITS

no

extra

no

extra

6.7

7.2

7.6

3.6

ESTIM.

COST

EtOH

2 7 ± 2 4

2 8 ± 25

24

15.5

14.5

15.6

GROSS

CAPITAL

INVEST.

A $ m .

23,500

25,250

26,500

1 13,000

R. S D.

o.i2

As

2.5

3.0

3,5

0.22

3.0

R.&D. BENEFIT

(a) to process juice

(b) thermal balance

for 1.

concept dev.3save 3C/1. =

$420m/year..

extra capital $1750m. cf.3,save 8.5cyi = $1200m/year

extra capital $3000m. cf.3,

save 9.5c/l = $1330m/year

cellulose hydrolysis. concept

dev. save capital $10,500m. cf.3 !

& 8.4c/1 = $1176m/year


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t

7.

8.

9.

10.

11

12

13.

As for 6 - 1600 ha properties.

Table XIX


Table XIX

As for 3 - plus cassava fallow crop.

50 ha farms. Table XX I

As for 9 - 1600 ha properties

Table XXI


Table XXI

As for 6 - plus cassava fallow crop,

50ha farms. Table XX II


Table XXII

3.9

4.1

5.4

5.8

6.0

3.2

3.4

11.1

10.6

22

15.2

14.1

15.8

11.6

13,500

14,250

19,000

20 3300

21,000

12,000

13,000

0,2

3.5

0.2

4.0

3.0

4.0

4.5

0.2

3.5

0.2

4.0

cellulose hydrolysis. concept

dev. extra capital $500m cf.6.

save 4.54/1 = $630m/year

cellulose hydrolysis,

concept dev. extra capital

$1250m.cf.6. save 54/1 -

$700m/year

concept dev. save capital

$4500m cf. 3. and 24/1 = $280m/

year


$1300m,cf.9. save 6.84/1 =

$950m/year

concept dev, extra capital

$2000m.cf.9. save 7.9c/1 =

$1100m/year

cellulose hydrolysis

concept dev. save capital

$1000m.of.6.extra 0.2c/1 =

$28m/year

cellulose hydrolysis


$500m.cf.7.extra 0.54/1 =

$70m/year


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14.

15.

16.

17.

18.

19.


Table XXII

As for 6 - but with agricultural

productivity doubled. 50 ha farms

Table XXIII


Social advantages over 17.

Save capital of $15,400m, cf. 3,

Save 15.6*/1 = $2180m/year cf.3.

Table XXIII


Table XXIII

As for 12 - but with portion of bagasse

as fuel and no coal. 50 ha farms.

Table XXIV,


Table XXIV

3.6

1.8

1.9

2.0

3.7

3.9

11.1

11.5

8.4

8.0

12.4

9.6

13500

8100

8700

9000

14000

14700

0.2

4.5

! 0.2

11.0

! 0.2[

11.0

0.2

12.0

0.3

5.0

0.3

5.5


concept development.

save capital $750m. cf.8.extra

.5c/l - $70m/year

cellulose hydrolysis, concept

development, save capital

$4900 m. of.6. save 4.1c/1 =

$570m/year

cellulose hydrolysis, concept

development, save capital

$4800 in. cf.7. save 2.7£/l =

: $378m/year

cellulose hydrolysis-

concept development,

save capital $5250m, of.8, save

2.6C/1 = $360m/year

cellulose hydrolysis.

concept development.

extra capital $2000m, cf.12.

save 3.4C/1 = $476m/year I


concept development,

extra capital $1700m. cf. 13.

save 2.0C/1 = $280m/year


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20.

21.

As for 17 but with space-age technology

with remote control.

Table XXV.

ESTIMATED MINIMUM PRICE ACHIEVABLE FOR

ethanol FROM SUGARCANE

2.0 7.5

7

9200 As for 17 plus

5.0 space-age technology development -

extra capital = $200m,cf.17.

save 0.5C/1 = $70m/year. save

remote location of 90,000 persons

1. To produce 14Gl/year of ethanol.

2. Essential for development of entire concept. Initial investment only.

3. 30% of all concept development costs to process studi es, 60 % to agricultural studies.

4. Total production achievable at this price range = 200Ml/year

5. Total production achievable at this price range = 400Ml/year,


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FLOW SHEETS AND GRAPHS

FIGURE

1 Simplified flow sheet for dual production of sugar

and ethanol

2 Simplified flow sheet for producing ethanol from juice

of sugar cane

3 Simplified flow sheet for whole cane processing with cellulose

hydrolysis

4 Relationship between estimated price of ethanol as

related to the size of the farm unit.


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Total steam 603

Figure Is Simplified flow sheet for dual production of sugar and ethanol.


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TABLES Page

A Summary of estimated costs of ethanol production vii

I Net Thermal Values of Selected Fuels 11II Dual product plant without additional molasses - raw 53

material costsIII Dual product plant without additional molasses - total 54

costs

IV Queensland mill size and land productivity criteria 60V Dual product plant with additional molasses. Raw

material costs 62VI Dual product plant with total estimated costs of ethanol 63VII Single product plant to produce ethanol without additional

molasses 67VIII Single product plant to produce ethanol plus additional

molasses (raw material costs) 68IX Single Product Plant with total estimated costs of ethanol

production 69X Summary of estimated costs of ethanol production -

primary options 70

XI Total ethanol potential for an 817,000 Te cane complex 71XII Effect of doubling the size of a sugar mill on ethanol cost 75XIII Estimate of photosynthetic efficiency of sugar cane in

Queensland 97XIV Tabulated indexed capital repayment rates 123-:XV Effect of size of field on cost of tractor usage 126XVI Cost estimates for cane grown on large properties or

estates 129XVII Estimated costs of road transport for sugar cane 137XVIII Estimated cost of processing sugar cane stalk juice

for ethanol 14-1XIX Estimated cost of ethanol from whole cane including

cellulose hydrolysis 161XX Cost estimates for growing cassava for ethanol 166XXI Estimated cost of producing ethanol from sugar cane stalk

juice and cassava 167XXII Estimated cost of producing ethanol from whole sugar cane

plus cassava 168XXIII Estimated costs of producing ethanol from whole cane

but with 80% achievable productivity. Coal as fuel. 171XXIV As for XXIII but no coal as fuel 176


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INTRODUCTION

Producing alcohol by the fermentation of plant sugars is probably

one of man's oldest technologies but until the development of distillation

as a means of concentration its use was restricted to such applications

as were suited to the relatively low concentrations it was possible to

achieve in this way.

Although) a distillation technique was described as early as Aristotle

in the 4th century B.C. it was not until the beginning of the 19th

century that its application to alcohol concentration became significant.

By the end of that century it had been developed to such a degree that

the fermentation and distillation of potatoes in Germany supplied

substantial quantities of alcohol for industrial purposes.

The word alcohol is of generic significance when used in organic

chemistry but in the current context the only alcohol with which we will

be closely concerned is ethanol (C.H OH) although some reference to other

alcohols will be made at appropriate stages.

Ethanol is the major product of alcoholic fermentations but small

quantities of amyl alcohols (d- and/or iso-) as well as some butyl and

propyl may also be produced and are generally referred to as fusel oil.

The amount varies between about 0.1 and 0.7% and may also include trace

amounts of fatty acids, esters, furfural and other substances.

Ethanol is the most important of the many products which can be

produced by fermentation for industrial purposes. The basic raw material

for this is the sugar glucose but this in turn is usually derived from the

breakdown of a higher molecular weight entity such as sucrose, starch or

cellulose. The relative importance of these as raw material will be


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considered. There are a number of reasons for giving primary

consideration to sugar cane which will be given later. Suffice

it for the time being to say that there is already a well established

sugar cane growing community in Australia and the agro-technology is

well understood. Sugar cane is known to be one of the best plants for

efficiently utilizing sunshine in the synthesis of carbohydrate and it

grows well under a wide range of soil and climatic conditions with

appropriate cultural techniques. In fact Australia leads the world in

the annual rate of production of sugar in cane per unit of area under

cultivation.

Ever since the internal combustion engine was invented, the

possibility of using ethanol as a fuel or partial fuel has been considered

and very detailed study went into the subject during the latter part of

the 19th and earlier part of the 20th century. The net conclusions have

been that it can be used successfully under a wide range of conditions

without significant modification being required for the engine as marketed

during the 1970's. There have been periods when certain countries have

made quite significant use of ethanol for internal combustion engines and this

includes Australia during the 1930's and 1940's. Special circumstances

have had their influence and these will be discussed later. Brazil

currently is an important user and is developing this capability rapidly.

Ethanol is a fuel which can be continuously regenerated as long as

there is sufficient land available for cultivation.

For some years the Halthusian predictions of population growth

outstripping available food supplies and apparently abundant mineral supplies

of liquid fuels militated against serious consideration being given to wide

scale growth of plant materials for industrial energy. These are no


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longer the spectre painted in the 1950's. Population growth now

appears to be most closely related to the economic advantages or

disadvantages of a large family. As long as there are economic

advantages, as in a labour intensive agricultural economy, population

growth is for all practical purposes, uncontrollable. With the

development of machine intensive cultivation techniques, the

disadvantages of a large family unit become apparent and slowly the

rate of population growth slows to controllable figures. The supply of

food is also related very strongly to the efficiency of harvesting and

storage techniques as well as to distribution facilities. The net

result is that with the exception of local conditions of drought or

flood the world in fact does have a surplus of food and there are good

reasons for believing that the situation will continue for the

forseeable future.

Ho person likes radical changes in their way of life, and a sudden

change from a petrol based liquid fuel economy to an entirely ethanol

based economy would be fraught with many problems. Fortunately this

should not be necessary in Australia and it could be introduced

progressively to replace imported petroleum fuel as it blends very well

with petrol in proportions which would be adequate to effect this change

with minimum of frustration and provide an extensive and well needed

development of employment in Australia involving a wide range of skills.

Ehhanol is a lesser fire hazard than petrol in storage and transport

situations. On the other hand it does have its own specific problems

such as unsocial results in human consumption and its miscibility with

water. There are ways and means of dealing . with these problems and

they will be discussed.

The environmental impact of large scale development would be expected

to be most prominent in two areas. Firstly the substantial extension of


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cultivated land and new housing development, possibly but not necessarily

at the expense of forest land. Secondly there would be the problems of

waste disposal from the fermentation process. The installations would

need to incorporate equipment and procedures to cope with this. On the

other hand ethanol can effectively displace alkyl-lead additives commonly

employed for increasing the anti-knock rating of petrol and which pollute

the atmosphere by their presence in exhaust gases. Internal combustion

engines operate at lower temperatures and run more quietly when ethanol

is used as a petrol additive. As a complete replacement for petrol

there are more problems including a significantly lower thermal value,

but when used in minor additive proportions there is no noticeable

increase in volumetric consumption, nor are changes required in the

tuning of the engine of significance.

These matters will each be considered in detail at an appropriate

stage.

When considering alternative energy sources it is thought to be

impracticable to attempt to displace all currently used types of mineral

based energy with a single type of energy derived in one way from a solar

source. This study will confine itself to problems involved in the

progressive development of liquid fuel derived from nature's solar cell-

chlorophyll through the intermediate natural synthesis and storage of

carbohydrate in sugar cane.

Reasons for the selection will be elaborated during the course of

this study.

Two questions of major concern become significant - (1) can ethanol

be produced at a satisfactory price and in substantial volume and (2)

can ethanol be used effectively as a major liquid fuel? The two


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questions revolve around each other and both must be answered effectively,

but it is largely a matter of choice as to which is discussed in detail

first. In this study the choice has been made firstly to study production

and secondly consumption, but always being cognisant of interactions and

side effects.


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ALTERNATIVE FUELS AND THEIR SOURCES

The internal combustion (I.C.) engine has become such a widely used

device in present day living that it is almost inconceivable to imagine

alternatives achieving more than marginal significance. These engines

have been developed to employ fuels in either the gas or liquid phase,

endeavours to employ powdered solid phase fuels or mixtures of solid and

liquid phases have not been successful due mainly to problems concerned

with the exhausting of ash constituents of solid fuels.

Only a very small proportion of I.C. engines employ gaseous fuels.

Whilst they do enjoy many advantages including a continuing supply of

fuel in the event of a development of a hydrogen based energy economy,

the major disadvantage is the difficulty experienced in developing

satisfactory storage techniques especially for small mobile units such

as the motor car. From time to time there have been developments in

the use of producer gas units including their attachment to mobile

vehicles. It is not proposed to consider these more than marginally

in the present study.

For our purposes we will consider the development of the I.C. engine

along two main lines to which we will apply simply the terms ::diesel::

and "petrol1 engines and in this context, the terms will be used

essentially to define the method of ignition - the diesel engine relying

on pressure ignition and the petrol engine relying on spark ignition.

There is an interaction of these two mechanisms as the compression ratio

of internal combustion engines is increased and the implications of this

will be shown to be important. The development of the diesel engine

was dependent very largely upon the successful development of fuel

injection to specific cylinders under pressure. On the other hand, the

carburettor system of the petrol engine has become progressively more

complex and there has been a marginal but growing encroachment of direct


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ALTERNATIVE FUELS AND THEIR SOURCES

The internal combustion (I.C.) engine has become such a widely used

device in present day living that it is almost inconceivable to imagine

alternatives achieving more than marginal significance. These engines

have been developed to employ fuels in either the gas or liquid phase,

endeavours to employ powdered solid phase fuels or mixtures of solid and

liquid phases have not been successful due mainly to problems concerned

with the exhausting of ash constituents of solid fuels.

Only a very small proportion of I.C. engines employ gaseous fuels.

Whilst they do enjoy many advantages including a continuing supply of

fuel in the event of a development of a hydrogen based energy economy,

the major disadvantage is the difficulty experienced in developing

satisfactory storage techniques especially for small mobile units such

as the motor car. From time to time there have been developments in

the use of producer gas units including their attachment to mobile

vehicles. It is not proposed to consider these more than marginally

in the present study.

For our purposes we will consider the development of the I.C. engine

along two main lines to which we will apply simply the terms T;diesel::

and !ipetrol: engines and in this context, the terms will be used

essentially to define the method of ignition - the diesel engine relying

on pressure ignition and the petrol engine relying on spark ignition.

There is an interaction of these two mechanisms as the compression ratio

of internal combustion engines is increased and the implications of this

will be shown to be important. The development of the diesel engine

was dependent very largely upon the successful development of fuel

injection to specific cylinders under pressure. On the other hand, the

carburettor system of the petrol engine has become progressively more

complex and there has been a marginal but growing encroachment of direct


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fuel injection into the petrol engine field.

The diesel engine is designed essentially to operate on low

volatility liquid fuels whereas the petrol engine and high volatility

fuels are largely designed for each other. In the competitive area

of society as distinct from controlled economics there is usually a

substantial cost advantage in using low volatility liquid fuel. This

has been largely accentuated by the tax structure which has been

developed with progressively increasing intensity on volatile liquid

fuels.

For the present considerations it is necessary to eliminate as far

as possible the incidence of tax on fuels for a true comparison of their

relative usefulness as energy sources, but at the same time, recognise

that taxation in some form or another is inevitable.

Ethanol can effectively displace either diesel or petrol type fuels,

but initially it will be considered as a partial substitute for petrol

type fuels with cognisance being taken of the likely results of

progressively increasing the proportion in petrol type fuels as well as

of progressive displacement of diesel fuels as well as petrol.

For ethanol to become a commodity generally available to the public

it becomes of major importance for its use to be restricted to that of a

motor fuel or related industrial applications and not be readily converted

to human consumption. There are two reasons for the latter requirement,

one involves the unsocial side effects, the other relates to the loss of

revenue imposed more heavily on alcoholic drinks of all types than on

motor fuels. The measures taken to effect desired control in this area

are known as denaturing of alcohol. While this will be discussed in

some detail later, it is well to point out at this stage that the

selection of a suitable denaturant is one of the most important and at


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Hydrogen gas is rated at 10.8 MJ/m3 at S.T.P. compared with 35.7

for methane. On a weight basis however, this would represent

120 kJ/g as compared with 43.7 for petrol.

Methane (CR4) as the most important constituent of natural gas or

produced by anaerobic fermentation is also difficult to liquefy and

currently of no real practical significance as a possible alternative

to petrol.

Methanol (CH3OH) is one of the most important products of high-

pressure organic syntheses used today, reacting carbon monoxide with

hydrogen produced as synthesis gas by the reforming of natural gas.

As natural gas is currently available in relative abundance in Australia,

the possibility of converting it to methanol as a liquid fuel supply must

be given significant credence.

Methanol can be used as a fuel for I.C. engines but it is not a

particularly good fuel having a nett thermal value (N.T.V.) of 20kJ/g

or 48% of that of petrol with ethanol at 27 or 63% of the value of petrol

on a V/V basis. Methanol is more volatile than ethanol which should

favour easier starting but the lower latent heat of vapourization is less

advantageous from the point of view of thermal efficiency.

Methanol has been important in the marketing of non-potable ethanol

by virtue of its usefulness as a denaturant. The classical denaturing

fluid has been "wood spirit" or "wood naptha" which used to be a product

of the distillation of wood. It is not a chemically pure material but

is considered to be about the nearest approach to a perfect denaturant

for ordinary purposes.


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There may well be merit in blending up to 10% of methanol with

ethanol to be used for motor spirit but this will be discussed in

more detail later.

Diethyl ether [(C2H5)20] can be produced in a relatively straight

forward manner from ethanol by dehydration with sulphuric acid. It is

not a particularly strong competitor for ethanol as a straight motor

spirit although it does have a thermal value about 14% higher on V/V basis.

It is too volatile - boiling point 34.6 - to be useful alone, but when

blended with ethanol it is beneficial in improving starting characteristics.

Up to 40% has been used in Natal (S.A.) blended with 60% ethanol and known

as "Natalite". When converting ethanol to ether there is a loss of

37.5% on a volume basis offset by an associated gain of 20% in thermal

value.

Acetone (CH3.C0.CH3) is intermediate between ether and ethanol

in terms of volatility (B.P.56.5°) and with a N.T.V. of 28.5 kJ/g or 23

MJ/litre is 69% of petrol (V/V).

Ethanol by way of comparison has a B.P. of 78.5 and a N.T.V. of

26.8 kJ/g or 21 MJ/litre.

Although acetone can be produced by chemical synthesis it is also

a product of fermentation using Clostridium genus bacteria.

Unfortunately, acetone is normally produced in association with butanol

by this process, a typical product being 60% butanol, 30% acetone and

10% ethanol. The butanol is of little value as a motor spirit because

of its low volatility (B.P. 117.7).

The net thermal values for a range of gaseous and liquid fuels are

listed in Table I. Whilst the N.T.V. of a fuel is by no means the only

criterion for selection it is an important one in -the screening

10


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Another development in the production of anhydrous ethanol has been

for a process to handle directly a fermentation mash at 6% ethanol making

use of an extractive distillation technique.

The development of these techniques had, however, only a marginal

influence on the employment of ethanol as a motor fuel since 95% aqueous

ethanol can be used quite readily as a mild blend with petrol with no

significant influence from the water. It can also be used directly or

as a methanol-denatured spirit, in fact as much as 50% of water can be

tolerated in a spark ignition I.C. engine provided a more volatile fuel

is employed for starting. The water does of course reduce the thermal

value of the fuel pro rata.

During the 1940's the production of ethanol as a petrochemical began

to become important with a progressive phasing out of the fermentation

product and synthetic ethanol dominated the ethanol market until the

recent substantial use in the price of crude oil.

Synthetic ethanol may be produced either from acetylene originating

from calcium carbide or from ethylene available from processing crude

oil. The acetylene route only enjoyed a relatively short period of

serious interest once the price of natural gas and crude oil fell with

the extensive discovery and development of resources since the second

world war. The conversion of ethylene into ethanol is a relatively

straightforward chemical procedure involving for example firstly

sulphonation with strong sulphuric acid

followed by hydrolysis and reconcentration of the liberated sulphuric

acid. Alternatively, a more straightforward vapour phase hydration

may be effected in the presence of phosphoric acid at a temperature of

300 and pressure of 70 kilopascals.


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14

Certain countries have continued to provide incentives for the

production of fermentation ethanol to encourage home industry and

reduce dependence on overseas energy supplies although generally the

latter effect has been largely marginal.

Since the rapid rise of the international price of crude oil there

has been a resurgence of interest in raw materials suited to fermentation

procedures. Future market situations will be influenced by relative

costs of raw materials, costs involved in processing techniques and the

development of technology related to the use of ethanol or its

competitors. The combination of these factors makes forecasting

hazardous. Venturing into forecasting will be deferred until later

until a more detailed study has been made of factors involved in the

production and use of fermentation ethanol.


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Whilst sucrose occurs in many plant juices it is most strongly

concentrated in the sugar cane or sugar beet.

Alcohol has for many years been produced either in potable form or

for industrial purposes from the molasses resulting from production of

cane or beet sugar. In the case of beet molasses there may be a

significant amount of the trisaccharide-raffinose. Upon hydrolysis

this yields glucose and the disaccharide melebiose which further

hydrolyses to glucose and galactose.

Normally galactose is a difficult sugar to ferment but it may be

effected with a bottom fermenting yeast whereas glucose and fructose

are satisfactorily fermented with either a top or bottom yeast.

Molasses is commonly a relatively low-priced commodity as there is

only limited scope for alternative uses such as fertilizer or animal

food. However the amount available is limited by the amount of

associated crystal sugar which is produced and local fermentation for

industrial purposes is seldom economically viable from the point of view

of actual size of equipment. Transport of molasses adds to the cost

if a central distillery is operated and the time came during the 1950's

when even molasses could not compete with crude oil as a raw material

for industrial ethanol.

Since the steepening of the price of crude oil in the 1970's there has

been a re-awakening of interest in supplies of molasses, especially by

the Japanese.


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21

Another qualification required is the time taken to grow the

crop. In most countries sugar cane is an annual crop with a growth

cycle averaging about 9 months. Hawaii which records by far the best

yield may harvest annually, but the growing cycle extends to 2 years.

Some other areas have a similarly long growing cycle with suitable

local reasons for maintaining production.

Similarly in the sugar beet situation although it is an annual crop,

the related sugar mangold can crop more heavily in weight/hectare

but with a lower concentration of sugar and is commonly a biennial crop.

Trees which are frequently considered as a source of cellulose for

fermentation take a number of years to grow. Alfalfa on the other

hand can be harvested every few weeks for a useful portion of the year.

Certain species of palm trees are sources for the production of a

low quality sugar in village communities throughout areas from India

to Indo-China. When calculated in terms of sugar yield per hectare per

annum they compare quite favourably with sugar cane grown in those

countries. However, sugar cane in those countries is relatively low

yielding and there are substantial harvesting problems with the palms.

In sugar palms, sap must be extracted from the florescent zone which

is 6 to 15 metres above the ground. On the cultivation side the palm

goes on yielding suitable juice for perhaps 50 years with little

cultivation, fertilizing or irrigation and ground level cropping or

grazing may be carried on over the same area. The palm does, however,

take about 7 years before it reaches maturity levels of production.

The cultivation of alfalfa to yield both protein and carbohydrate

has been suggested with annual yields of up to 63 tonnes of carbohydrate

per hectare suggested as achievable, but the value of an associated 25 tonnes

of ve etable Drotein would in itself be a uite si nificant factor in costin


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It is of some importance to know the nature of the carbohydrate

in the plant. If we assume an ethanol recovery in production of

88% of that theoretically obtainable from the carbohydrate, then a

yield could be expected of 600 1/tonne for sucrose whereas starch or

cellulose would yield 634 and glucose or fructose 570.

Whilst the hydrolysis of sucrose can be expected to be stoichiometric,

the efficiency of cellulose hydrolysis is usually very low and often as

low as 50% or even 35% with recalcitrant types. A high degree of

saccharification can be achieved with starch and a yield of 634 1/tonne

is not unusual. This represents a 5.6% benefit over sucrose and 11%

over glucose or fructose.

Cellulose hydrolysis and fermentation processes of a commercially

viable character have been particularly difficult to achieve and there

is still a great deal of investigation going on in this field both in

Australia and overseas.


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There are further difficulties with statistics. Sugar production

is referred to in terms of 94 Net Titre (N.T.) in Australia. This is

a quality criterion of local concern, designed to estimate the actual

amount of refined sugar crystal which can be produced from raw sugar of a

certain quality and involves corrections for the ash and hexose content

of the raw sugar.

Furthermore sugar contents are referred to in terms of "pol"

which is an abbreviation for polarization and refers to the technique

universally employed for analysis. It is well known that this does not

reflect the true sucrose content but is a sufficiently close approximation

for most purposes to allow full advantage to be taken of the rapidity of

the method. We can get an indication of the order of precision of the

pol value if we have an analysis of the final molasses from the same

factory at the same time in terms of both pol and sucrose. If we take

as an example a sample of 100 tons of crystal sugar having the following

analysis which is typical of Australian conditions:

Pol = 98.37 per cent

Reducing sugar = 0.37

Ash = 0.38

Moisture = 0.43

The N.T. value then equals Pol - R.S. - (5xAsh) = 96.10

Tonnes of 94 N.T. sugar = tonnes actual sugar x actual N.T. = 102.23.

94

Experience indicates that the actual sucrose content would probably

be closer to 98.52 than to the pol value of 90.37. Thus if the figure

for tonnes of 94 N.T. sugar be reduced by 3.8% a better representation of

the weight sucrose in crystal raw sugar would be obtained. Actually a

discount of 4% is commonly applied which very closely represents the weight

of pol.


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In actual fact there is no such substance as polr. The term is

an abbreviation for the word "polarization which refers to the technique

commonly employed for analysing sugar house products. It is obtained by

observing the sugar solution with a beam of light which has been optically

polarised. The sugar in the solution proportionately affects the degree

of polarization and the instrument is appropriately calibrated.

Unfortunately sucrose is not the only substance in a cane sugar juice

or raw sugar solution which affects the polarised light in this way.

The two main non-sucrose substances in sugar cane products which act in

this way are the hexose sugars glucose and fructose. The fact that they

have an influence opposing each other and which largely compensates has

enabled the convenience of the method to be extensively applied in the

sugar industry. Under conditions of poor technology, it does not matter

very much but the better the standard of technology the more significant

is the difference between the sucrose and pol values. To perform a true

sucrose analysis is difficult, complex and tedious with the consequence

that experimental analytical error can be of the same magnitude or even

greater than the real difference.

However, it is considered to be valid to take into account the

differences between pol and sucrose for the purpose of the current exercise

and to apply the correction in accordance with the best experience.

Statistics recorded in Queensland literature for yields of sugar per

hectare are in terms of 94 N.T. quality and require appropriate correction.

This however represents only the sugar recovered as crystal. From the

point of view of ethanol production, we are more concerned with the total

sugar content of the juices in the cane since both glucose and fructose

can be fermented to ethanol. Unfortunately these are even more difficult


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27

to estimate because sugar cane in Australia is evaluated in terms of

C.C.S. which letters stand for "Commercial Cane Sugar". The C C S . is

calculated from a formula designed to estimate the actual amount of

"94 N.T." sugar which can be produced from a particular tonne of cane.

The C C S . is calculated as follows:

C.C.S. = Pol in Cane - 1/2 Impurities in Cane

Since Impurities in Cane = Brix in Cane - Pol in Cane

then C.C.S. = 3/2 Pol in Cane - 1/2 Brix in Cane

Like Pol the term Brix does not refer to any substance in particular.

It also refers to the result of a convenient analytical technique and

approximates the total solids dissolved in the juice or syrup. The

measurement involves a determination of the density of the liquid usually

using a type of hydrometer especially calibrated for sugar solutions.

In high purity juices and syrups the readings are usually sufficiently

accurate for most purposes but in low purity juices and molasses there is

a progressive deviation from the true figure as the proportion of non-

sucrose increases. Brix may also be measured by means of a refractometer

the values for which are intermediate between the true total dissolved

solids and the hydrometric value. The measurement of Brix is not

particularly critical at this stage as far as the ethanol proposal is

concerned.

The C.C.S. formula was designed also to evaluate the Pol and Brix

content of the cane itself from the analysis of the juice expressed by the

first roller of the milling tandem. Whilst the technique has distinct

advantages from the point of view of speed and simplicity it does have

limitations from the point of view of precision. Present day techniques

prefer to sample the cane rather than the juice and to perform a direct

analysis on the sample of cane. The added complexities have very largely

been minimised by the development of better technology for sampling, sample

preparation and sample analysis.


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28

In the example which has been quoted the C.C.S. for the corresponding

cane was 13.11 and the density of cane growth was 84.6 tonnes of cane per

hectare. The pol in cane was recorded as 14.41%. If this be corrected to

a sucrose value it would probably have been 14.83 or 2.9% higher than pol.

It is estimated from the analysis of juice resulting from the cane that

the hexose concentration would have been about 3% of the pol or 0.43% on

cane. For the purpose of estimating ethanol production it is convenient

to convert this to "equivalent sucrose" or 0.41%. Some other workers in

this field prefer to convert to "equivalent glucose".

Thus the fermentable sugars "as sucrose" in the cane would be 15.24%

and the production per hectare 12.9 tonnes.

If productivity and quality of cane continue to improve at the rate

of 1.58% per annum then for the 11 year period 1980/90 a mean value of 15.2

tons per hectare would be indicated as compared with the mean of the 11 year

period 1963/73. Predictions for specific years have a lower precision

(St.D. ~ 7.5%) than predictions for a decade (St.D. - 2.5%) owing to variable

seasonal influences. There is some levelling out of these influences by

virtue of the north/south relationship of the Queensland sugar belt in

that a bad season in one area seldom extends through all the other sugar

growing areas and vice versa.

There is a substantial difference between the highest and the lowest

yielding areas with the Burdekin as high as 18.7 tons of 94 N.T. per hectare

in 1973 as compared with 8.84 for the Mackay and Proserpine areas in the

same year.

Traditionally ethanol production in the cane sugar industry has been

very largely restricted to the use of molasses as a raw material. There

is no technical reason however, restricting production from the juice itself.


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This may be seen as very largely related to the pricing policy of

the oil companies with ethanol being invariably priced higher than

refined petrol, although pricing of petroleum products or petroleum

based materials is so extraordinarily complex that it is impossible to

be able to make a real comparison on the basis of specific costs. In a

multi-product industry, real costs are not the only factors involved in

pricing policies.

The present resurgence in interest for agro-ethanol has resulted from

anticipated shortages in available mineral oil supplies and related price

escalations.

Industrial ethanol and potable ethanol have for many years been produced

from sugar cane molasses and about 40% of the Queensland molasses production

is diverted for use in this way in Australia and a similar amount exported

of which an unknown proportion is converted to industrial ethanol.

Molasses production in Queensland amounts to about 216 kg/tonne sugar or

28.7 kg/tonne of cane. As the molasses contains about 54% of total

fermentable sugars (as hexoses) this is equivalent in ethanol to only about

8.8 1/tonne cane.

In other countries the sugar cane juice contains less sucrose and a

higher proportion of hexoses and non-sugars. As a result the molasses

production may be 2 to 3 times as high per tonne of cane with consequently

higher ethanol production potential.

One effect of this is that it was not really economical in Queensland

to establish a distillery for the molasses from only one sugar factory.

The only distillery which has been established in Queensland to process

molasses for industrial ethanol has drawn its supplies from a number of

factories using mostly rail transport. The distillery is currently

located at Sarina and is now rated at a capacity of 50 Ml/per annum.


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The actual amount of molasses required to produce this quantity of ethanol

will vary somewhat according to the amount of fermentable sugars it

contains.

Total sugars in final molasses when converted to glucose amount to

approximately 53% in the Central-Burdekin areas, which on an ethanol

recovery of 88% of stoichiometric would mean 3001/tonne. At this recovery

it would require 1679000 tonnes of molasses.. In the 1975 season the

molasses produced in the central district - Mackay area alone was 177,632

tonnes with an additional 88,654 tonnes in the Burdekin district from which

some supplies are also drawn.

There are two distilleries in Queensland licensed for the production of

potable ethanol which differs in its pricing structure from industrial

ethanol.

If central distilleries for industrial ethanol from molasses were

located in the Northern, Burdekin and Bundaberg areas and used 90% of the

molasses available they would have outputs of the order of 30, 26 and 20M1

(with allowance for current usage for potable ethanol production.

Thus something of the order of 100 Ml might be obtainable from all the

available molasses in Queensland. In actual volume it would be equivalent

to about 2 1/2 days of Australia's total petrol consumption or 5 weeks of

consumption of a 7% blend.

At current prices of Australian crude oil ( A$2.2/bbl) ethanol would be

far from being a commercially viable alternative. However, Australia

has been importing oil to the extent of about one third of her total

requirements and this proportion is expected to more than double within ten

years. Figures concerning this industry get out of date so quickly that

it is difficult to orient thinking correctly at any particular time.


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For a number of years developments in the ethanol fermentation field

have been proceeding at very leisurely pace because of the heavy dominance

of synthesis ethanol. Since the current energy crisis has developed

the fermentation for ethanol has received very much attention and it is

inevitable that important "freezing" decisions will become necessary.

In such a situation there will be endeavours to sell outdated

echnology at a discounted price. This can appear to have many economic

advantages in the short term but for disadvantages to become progressively

more prominent. Decision makers will also have to evaluate the relative

merits of tested techniques with those which have not proceeded beyond the

laboratory stage no matter how hopeful prospects may be.

The same applies to raw material supply - cane breeding, growing,

harvesting and transport.

It is most unlikely that an ethanol processing facility could be

established to operate effectively before the 1980 sugar season even on a

limited scale of dual operation. Nothing earlier than 1983 might be

contemplated for entirely new area development.

Because the sugar cane growing industry is well established in Australia

nd all the mechanisms for progressive development appear to be operating

satisfactorily, it should be safe to use anticipated 1985 field productivity

figures as a basis for estimating the average type of situation which might

e expected for the first 5 years of meaningful operation. This will be

done for the purpose of this report and appropriate modifying factors may be

applied if so desired.


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38

BASIC FUNDAMENTAL INFORMATION

Productivity of cane = 90.0 tonnes/ha. average 1980/1990.

(actual projected figure = 90.49 ± 1.81)

Yield of sugar = 13.92 tonnes of 94 N.T. sugar /ha (±0.1)

C.C.S. = 15.3

Comparable to Central District average 1970 - 15.24 C.C.S. 16.51 pol % cane

or Burdekin 1969 - 15.56 C C S . 16.72 pol % cane

Sugar in cane as equivalent sucrose = 17.0% cane

" " " " " " " glucose = 17.9% cane

Productivity as equivalent glucose = 16.2 tonnes/ha

Stoichiometric ethanol potential = 6481/tonne glucose = 9.72 kl/ha

Juice extraction = 95.5%nett = 84%

Fermentation/distillation efficiency 88%

Nett ethanol production potential = 0.8 kl/ha or 97.4 1/t.c.

The price of cane is qualitatively related to the price of sugar:

Price of cane = Price of Sugar x .009 ( CCS.-4) + 0.382

Price of sugar = $170/tonne 94 N.T.

Equivalent price of cane = $17.67 tonne

Molasses = 2.75% cane - 53% of total sugars as glucose.

Part of the stability of the present sugar industry in Queensland must

be related to the fact that no new complete sugar production plant has been

erected in Australia since the Tully Mill which produced its first sugar in

1925. In fact several of the smaller plants have been closed down including

the sugar beet factory at Maffra in Victoria. Most of the other plants in

Queensland were erected towards the end of last century or early in the

current one, although many changes have been made and present standards of

equipment are generally good by any standards.


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As examples of these conflicts may be cited, firstly capital cost

items.

An attached fermentation/distillery plant should not require additional

team or power generation facilities as already indicated.

A plant to produce ethanol at 42.2 Ml within 70% operational time of

32 week season would be rated as having 100 Ml/annum installed capacity.

One Australian estimate for a plant of this capacity and attached to

sugar factory is $40m. At the other extreme are figures from U.S.A.,

ermany or Japan closer to $4m.

It is well known that Australian costs for capital equipment are high

ompared with overseas costs but not to this extent. Perhaps a factor 1.3 or

ven 1.5 should be more realistic than a factor of 10.

Steam consumptior figures seem to be reasonably consistent with a

igure of 2 kg steam/1 of rectified ethanol being obtained with modern plant

n the distillation and rectification stages. Sterilization of juice and

iscellaneous needs would add another 1 kg and the dehydrating distillation

further 1.5 kg making a total of 4.5 kg steam/1 of absolute ethanol.

The figure of 2 kg for the production of rectified spirits is based on

he processing of molasses diluted to a concentration of 10% of sugars.

uice would have a concentration of 17% of sugars or 24% after mixing with

he A molasses.

Research on fermentation has aimed at processing higher concentration

olutions and since the purity of the juice - A molasses mixture with respect

o total sugars would be close to 84% compared to about 66% for final

olasses there may be good prospects of operating at higher concentrations


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with the purer materials. For the juice - A molasses mixtures, if fully

effective hydrolysis and fermentation can be achieved, this would be

equivalent to 15 to 15.5% of alcohol (w/w) in the product mash or 19% v/v.

These concentrations are probably approaching the limit and a practical

limit of 15% v/v would be more realistic - actually values up to 14% have

been claimed for fermented molasses beers and molasses diluted to sugar

concentrations as high as 18% are reported to be successfully treated in

fermenters.

There are undoubtedly further steam economics which could be effected

in the fermentation/distillation procedures but it would require more

specific experimentation with sugar cane juice itself before these could

be estimated. Fermentation of so-called high-test molasses would be with

a raw material somewhere between final molasses and the juice - A molasses

mixture envisaged here. Whilst there is experience with high-test molasses

overseas this has not been a raw material in Queensland distillery experience,

high-test molasses has always been too valuable for crystallizing sugar.

Labour requirements indicated from reported experience seems to be about

400 1/man-hr but this varies according to the size of the distillery and the

degree of automation and a halving of this cost would not be too difficult

to envisage.

Undoubtedly there are differences in techniques and problems of suitable

selection of equipment and processes are compounded for a 1979+ installation

because of the long time which has elapsed since competitive quotations have

been common in the field of fermentation ethanol. It is difficult also to

know just what charge to make for the use of sugar mill equipment and

management, obviously this cannot all be charged against the 50% usage of

its facilities for sugar production. Here again much secrecy prevails

concerning real operating costs although there are some yardsticks such as

examining financial information provided for shareholders and applying


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44

appropriate factors. The monies received from the sale of raw sugar

are debited with the costs of selling and the balance distributed between

the farmer and miller. The proportion which the farmer gets varies with

both C C S . and price of sugar. As a general statement distributions

are recognised as being aprroximately two-thirds for the farmer and one

third for the miller. At C.C.S. values above a certain figure the farmer

gets more than this proportion and when the price of sugar is above a

certain figure he gets less than this proportion. The following

calculations closely approximate the turning points in this relationship.It can be seen therefore just how difficult it is to translate income

from processing for raw sugar to income for processing for ethanol.

At the 15.3 C.C.S. average figure chosen for this exercise, if the

miller operated at 100 coefficient of work (he might well operate up to

102 in this C.C.S. range) then he would receive 32% of the sugar price

and the farmer 68%. He would have to process his ethanol at 7.78¢/1.

Calculated thus:

Cost of 100 tonnes of cane @ 15.3 C C S . and sugar @ $170/tonne 94 N.T.=$1776

Money which would have been received if 15.3 tonnes of sugar had been

produced = 15.3 x 170 = $2601

Miller's share = 2601 - 1776 = $825


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Value of sugar actually produced = 7.6 x 170 = $1292

Miller's share = 1292 x 825 = $409.80

2601

Income the miller would expect to receive for processing to ethanol=

825 - 409.80 = $415.20

Ethanol expected to be produced from 100 tonnes of cane under these

conditions = 5340 1.

Pro-rata money required = 7.78¢/l ethanol.

We are also now in a better position to cost the farmer's

contributions.

Total money the farmer receives = $1776

Money paid to farmer for the 7.6 tonnes of sugar produced: this would

have come from 7.6 x 100 = 49.67 tonnes of cane

15.3

49.76 x 17.76 = $882.20

Value of cane used for ethanol production = 1776 - 882.20 = $893.80

Pro-rata ethanol cost = 16.74¢/1 (see previous figure of 17.11)

Total cost of ethanol = 24.52 ¢/1.

The costs of chemicals for fermentation are difficult to assess because

of the differences between juice and final molasses. It is necessary to

determine whether the juice for ethanol should be put through the classical

sugar juice purification stages or merely heated for sterilization. The

general appearance of clarified juice would be much better, but the lime

used for neutralizing the natural acidity of the juice would have to be

paid for as well as the cost of sedimentation and mud filtration.

Clarified juice at a pH around 7 would have little natural hydrolysing power

for the sucrose where a pH of 5.5 for raw juice would be quite useful in

this respect especially if temperatures are taken to 100 for sterilizing.

Much of the protein in the raw juice would be coagulated by this

treatment but there would seem to be no point in separating this, rather


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allow it to go forward to the fermentation stage. The juice would need

to be cooled to a primary fermentation temperature around 27°. This is

most easily effected by flash cooling but a vacuum higher than normally

achieved in a sugar factory would be needed viz. 29 inches rather than

26.5 or an absolute pressure of 3.5 kPa instead of 12. Flash cooling

to 50 supplemented by refrigeration cooling would appear to be a

desirable combination to give positive temperature control.

A pure culture yeast should be selected on its ethanol producing

capacity rather than one which might be more suited to also producing

the associated flavours desirable in the manufacture of potable spirits.

Yeast at the rate of l0kg/kl would seem to be the order of magnitude

required if the yeast is separated from the mash by means of centrifugal

separators and recycled as in the Helle process. This is done before

distillation and the separated yeast re-introduced into fresh "mash".

With this process it has been found possible to re-use the yeast

continuously for periods as long as a sugar season and with yields of

91-92% of ethanol.

Three stages of distillation are employed - the first two being with

double effect conservation of energy and 95% ethanol-water is produced as

a constant boiling point mixture. This is dehydrated by azeotropic

distillation to produce absolute echanol.

The total protein in the juice is likely to be about 0.5% on raw

juice solids or about 200 g N/kl of raw juice. The amount of N required

for fermentation is somewhat less than this figure but the extent to which

the yeast might be able to avail itself has yet to be determined. Raw

juice should contain about 500 g of P2O5 /kl which should be adequate for

the yeast. Other mineral constituents of raw juice would include about


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1300g/kl of K2O, 300g/kl of CaO and 400g/kl of MgO. Each of these

should be adequate for the requirements of the fermentation process.

The actual concentrations and proportions of the various mineral

constituents vary according to the composition of the soil and the

nature of the fertilizer programme in the cane field.

The slops or residue from the still would contain 18.5 to 20 kg of

solids at a concentration of 6.3% and disposal as effluent is undesirable

from the environmental point of view. It might be used as irrigation

water as the soluble substances are mainly good plant nutrients. This

would not be entirely without cost and some storage would be needed

because irrigation usage would not necessarily coincide with process

production. Furthermore it would then be necessary to acquire some of

the water required at the mills for lixiviation.

Alternatively the slops could be used partly as maceration fluid for

the lixiviation process. Recycling of weak alkaline juices for this

purpose has never been a satisfactory exercise in sugar mill operation

because excessive slippage tends to develop under these circumstances.

The slops however would tend to be acidic and may be suitable for recycling.

Recycling of slops solids as fertilizer is simplified if they are

concentrated to about 50% total solids. For this purpose a multiple

effect evaporator would be required and a quadruple unit would be adequate

from the point of view of steam economy. If the concentration of solids

in slops were to be doubled by recycling for lixiviation this would have

little effect of significance on the overall steam balance but the size of

the unit could be reduced to less than half.

A possible flow sheet is outlined in Figure 1, together with a balance

of materials and steam requirements.


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A fibre content of 14.4% on cane is assumed for these calculations.

The estimated total steam requirement for the dual process is 748 kg/tonne

cane if quintuple effect evaporation combined with steam bleeding from the

second effect for juice heating is employed for the concentration of juice

and a quadruple effect with pre-heating from the first effect is used for

slops concentration.

If the steam is generated with an efficiency of 82% on N.Th.V. of

bagasse the potential supply would be 876 kg/tonne cane. An efficiency

of this magnitude is quite common for bagasse fired units when it is

needed, in fact such equipment was installed and successfully operated in

Queensland as far back as 1938. In the present day situation fibre values

of cane are significantly higher as a result of variety changes and much

lower steam generation efficiencies are adequate.

For full crystal sugar production the factory would require not more

than about 550 kg of steam/tonne cane in which case the steam would need to

be generated at an efficiency of only 51%. The efficiency would need to

be increased to 70% to operate the distillery and its accessories. In

modern boiler installations there is a certain built-in flexibility to

enable higher efficiencies to be operated for seasonal periods when fibre

in cane is low and incineration conditions when fibre values are high.

Whether the available flexibility is sufficient to cope with an increase

to 70% would depend upon the particular installation concerned. There

would in fact need to be sufficient flexibility to go up to the 82% if

the fibre were to fall as low as 12.3. This is possible for the early

weeks of a season and the probability would have to be estimated from a

study of local data. Values as low as 13.3, however, would probably have

to be allowed for with an equivalent efficiency of 76%.


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In assessing costs it is necessary to take into account the

oss of income experienced by the miller from the sale of molasses which

ould amount to some 22,500 tonnes for cane of the quality treated.

o offset this would be the value of concentrated slops as fertilizer.

he quantity of such product would be 15,000 tonnes of dry solids.

he average price of chemical fertilizer is of the order of $100/tonne

o that a value of perhaps $50/tonne of dry solids might not be an

nreasonable valuation. It will be assumed for the purpose of this

xercise that the value of slops fertilizer compensates for the loss of

molasses.

Furthermore no credit has been transferred to ethanol production

hich would result from the simplifications made possible in the production

f raw sugar whereby only A massecuites are boiled and which are more

easily treated in the centrifugals than the normally succeeding B and C

assecuites. Mo large crystallizers are required for C massecuite

xhaustion.

These benefits are difficult to quantify and are marginal but never

heless real.

Cost estimates for the acual production of ethanol in dual product

perations would need to be closely related to the general pattern of the

ugar industry.

The distillery would require labour for its own operation, the raw

ugar section would also require labour but in smaller numbers for a 50%

roduction rate, but not a pro-rata reduction.

The cost of transporting cane to the mill is part of the miller's

ost structure and the distillery would be expected to pay for 50% of


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this cost, also 50% of the costs of milling and of operating the steam

generating plant.

The labour required to operate the distillery itself would depend

upon the degree of automation incorporated in the process. For a

distillery of the size associated with this project a figure of 800 1 of

ethanol/man-hr is the one which will be used here. This would appear to

compare reasonably with a figure of 400 1/man-hr quoted for some

distilleries overseas with throughput rates of the order of one quarter

of that envisaged here.

Although the distillery under discussion would be expected to produce

44 Ml of ethanol in a season of 150 days it would be rated at closer to

100 Ml if operated continuously on a yearly basis. This is twice the

rated capacity of the present molasses based distillery at Sarina which

is described in the 1977 Australian Sugar Year Book as being "large by

world standards".

At 800 1/man-hr a labour force of 15 men per shift would be required.

On the raw sugar side there might be 8 men per shift reduced to 6, half of

whose costs should be carried by the ethanol plant.

Half of the capital charges of the sugar plant should also be borne

by the ethanol. It is very difficult to assess a figure for this since

no new sugar mills have been built in Queensland for over 50 years

although many items of equipment may be relatively recent installations.

Perhaps an idea of the "book value" may be obtained from observing that a

sugar mill of about half of the size being considered here changed hands

in 1976 for around $4m. which would indicate a figure of the order of $6m

for one twice the size. Two sugar mills of about the size being

considered here also changed hands in 1975, but were included in a package

deal which tended to mask the actual values put on the sugar mills themselves.


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owever a figure of perhaps $8m. each may not be very far out as they

ere rather more efficiently equipped than the smaller $4m. unit.

ndoubtedly all three figures are well below replacement costs, but

ould be within range of the cost strictly to be taken into account for

ssessing the ethanol plant liability.

Since it is easier to assess the capital charges at an overall

igure for the entire sugar milling and factory complex the service charge

or transport of cane relates only to the cost of labour and consumables

uch as fuel for the locomotives.

The cost picture now emerging is ummarized in Table II. Since the

uality of cane varies from one district to another an indication of the

rder of magnitude of this effect is given as well as for the "average"

onditions


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It is evident therefore that the cost of producing ethanol in a dual

product arrangement with a 50-50 split in the manner indicated would result

in the ethanol processing costs exceeding the cost of the equivalent raw

sugar production by about 45% if the miller is to be recouped for his effort

in terms satisfactorily in line with current sugar industry arrangements.

The increase necessary in the price of ethanol is 3.88¢/1.

53

TABLE II

Dual Product Plant to produce ethanol not using molasses from other mills

in the district. Processing costs only


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In Table III is set out the effect of different quality of cane normal

to the four districts. The differences have been proportioned relative to

average C.C.S. ratios for each district taken over the years 1971/75 to the

average C.C.S. for Queensland during the same period and the equivalent

C.C.S. calculated relative to the base average figure of 15.3 which we

have so far been using. The corresponding price of cane has been

calculated relative to a raw sugar price of $170/Te 9*+ N.T.

The corresponding raw material cost has been evaluated in terms of

¢/l of ethanol. The appropriate processing cost has been transferred from

Table II and added to the raw material cost to give an indication of the

total estimated cost of ethanol produced under the conditions specified.

These figures do not include the cost of transport to the nearest port.

TABLE III

Dual Product Plant to produce ethanol not using molasses from other mills

in the district. Raw Material plus Processing Costs


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it would be some time before reasonable equilibrium had been reached

in design details.

Therefore if there is to be an initial selection of certain factories

for preferential development the criteria for selection should first be

identified. The following criteria are listed in the event of the

choice being the first of the two alternatives just listed.

(1) Magnitude of current scale of sugar production - it is only in

this way that any advantages associated with large scale

production of ethanol could be secured. There is no difficulty

in identifying factories meeting this criterion, simply by

reference to the list of assigned sugar production in statistical

records or "mill sugar peaks" as it is known in the industry.

Also see Table IV set out in this report.

(2) Efficiency of operation. This criterion is more difficult to

identify. Firstly there are at least two measures of efficiency -

(a) yield of sugar as crystal relative to sugar in the cane and

(b) labour cost involved in production. Other efficiency

criteria might include (c) management and (d) cost of materials

such as lime and added fuel. Most of this information is of a

confidential character.

Information related to operating efficiency is exchanged between

factories through the co-ordinating services of the Bureau of Sugar

Experiment Stations but it is still confidential within the group.

Financial information is even more confidentially covered and only an

intelligent guess is possible from such company balance sheets as may

be published or from such other stistics such as employment records

which might: be ferreted out of government files if access is possible.


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(3) Locality with respect to a port should be given some weight as a

pipeline of several kilometers could

Documents

A Feasibility Study of the Production of Ethanol From Sugar Cane