WO2008029163A2

WO2008029163A2 - Processing of sweet sorghum for bioethanol production

Info

Publication number: WO2008029163A2
Application number: PCT/GB2007/003395
Authority: WO
Inventors: Arsen Badalov
Original assignee: Nasamax Limited
Priority date: 2006-09-08
Filing date: 2007-09-10
Publication date: 2008-03-13
Also published as: GB2447062A; WO2008029163A3; GB0617762D0

Abstract

A method of processing sweet sorghum cane for sugar extraction is disclosed. The method comprises passing the cane into a first cutter (4) to cut the material coarsely and then passing the material into a second cutter (7) to cut it into fine fibres. The fibrous material is then passed to a press (10) to extract sugar juice for fermentation in a bioethanol production plant (25).

Description

Processing of Sweet Sorghum for Bioethanol Production

The present invention describes a productive and efficient method of processing sweet sorghum (sorghum bicolour) whereby the sweet sorghum cane is cut into very fine fibres so that the sugar juice in the sweet sorghum can easily be extracted from the fibrous material for subsequent fermentation into bioethanol. The lignocellulose material in the residual baggasse from the juice extraction process is also in suitable fibrous state for prehydrolysis with mild acid or alkali to break down the lignocellulose into its lignin, cellulose and hemicellulose constituents for subsequent conversion into fermentable sugars.

Natural ethanol produced from cultivated sugar or starch bearing plants is a clean burning renewable fuel that is being increasingly used as a substitute fuel for road transport applications. The market for bioethanol road fuel is growing so rapidly that demand is starting to exceed supply, and there is an urgent need for alternative plant species that can produce substantial volumes of feedstock for conversion into cost effective bioethanol on a large industrial scale.

In this respect, sweet sorghum is a unique sugar bearing plant in that it has a rapid and prolific growth rate and it can also be grown in different climates. Under the right climatic conditions, sweet sorghum has such rapid growth that it is possible to grow more than one crop of sweet sorghum a year; for example three crops a year are feasible under tropical conditions and between two and three crops a year are possible under subtropical conditions. Sweet sorghum is therefore a very productive energy plant species that can provide large amounts of sugar and lignocellulose material for conversion into bioethanol. For example, the sugar would be fermented by yeast into ethanol, whilst the lignocellulose would be digested with acid or alkali to separate out the lignin, convert the hemicellulose into sugars, and expose the cellulose for conversion into fermentable sugars by enzymatic hydrolysis. Sweet sorghum is not widely used for food production and sweet sorghum is therefore an ideal plant for cultivation as an energy crop. In this respect, a system that combines the cultivation of sweet sorghum with the production of bioethanol has been developed for tropical and subtropical climates. The system allows sweet sorghum to be grown all year round so that there is continual supply of fresh sugar juice and lignocellulose material readily available for the ethanol production plant. Under the combined cultivation and bioethanol production system, there would be enough freshly harvested sweet sorghum available each day to meet the sugar and lignocellulose feedstock requirements of an integrated bioethanol production plant.

The ethanol production plant would be located immediately adjacent to the land dedicated to the cultivation of the sweet sorghum so that the raw material feedstock can easily be shipped to the ethanol plant, which helps to reduce transport costs and environmental pollution. The sugar in the juice of sweet sorghum tends to deteriorate quickly, and a further advantage of the combined system is that freshly harvested sweet sorghum will be delivered each day to the ethanol plant so that the sugar content of the cane will always be near its peak level. Effluent water rich in plant nutrients from the ethanol plant would also be used as fertiliser to promote the growth of the sweet sorghum in the nearby plantations.

For the combined cultivation and ethanol production system to work effectively it is essential that after harvesting the sweet sorghum cane is moved straight from the field to the ethanol plant so that the cane remains in a fresh condition, and that the cane is then processed quickly and efficiently on arrival at the ethanol plant so that high quality sugar and lignocellulose feedstock is readily available for the ethanol conversion processes.

By way of example, a typical large integrated bioethanol plant would produce about 160,000 litres of ethanol a day, which is equivalent to 56 million litres a year. A plant of this size would need 1280 tonnes of fresh sweet sorghum delivered every day to meet the sugar and lignocellulose feedstock requirements of the ethanol conversion processes. It is therefore imperative that the sweet sorghum cane is processed quickly and efficiently so that there is a continual supply of fresh sugar juice and lignocellulose material available for the ethanol conversion processes, and that as much sugar and lignocellulose as possible is extracted from the cane to maximise the yield of bioethanol. Conventional methods of extracting sugar juice from sugarcane usually entail stripping or

Λ cutting the cane into pieces and then mechanically crushing the pieces of cane under high pressure in a roller press to squeeze the juice from the cane. The established methods of juice extraction are energy intensive and they can be inefficient because large amounts of sugar might be left behind in the residual baggasse.

Like sugarcane, the cane from sweet sorghum is a tough material and it has been established by practical trials that conventional methods of juice extraction tend to work poorly with sweet sorghum cane. For example, when sweet sorghum cane was cut into small pieces about 13 mm long and the pieces of cane were then crushed in a roller press, only 70% of the sugar that was available in the original unprocessed cane was retrieved from the cane.

In addition, the baggasse material remaining from conventional cane crushing operations is usually in relatively large size pieces that would be unsuitable for prehydrolysis with acid or alkali. The baggasse would therefore have to be ground, milled or pulverised into very small pieces before the lignocellulose material in the baggasse was in a suitable state for effective digestion with acid or alkali.

Established milling and grinding techniques that are used for sugarcane baggasse and other biomass residues, such as straw and wood, are not particularly effective with sweet sorghum baggasse. The residual baggasse still tends to be relatively coarse and to achieve adequate separation of the lignin, hemicellulose and cellulose constituents from the lignocellulosic matter in the baggasse, the residual material would have to be subjected to strong and prolonged acid or alkali digestion to break down the lignocellulose.

Alternative techniques were therefore considered for the preparation of sweet sorghum cane that would provide efficient juice extraction and at the same time reduce the residual baggasse material into a very fine state that would be suitable for efficient prehydrolysis under mildly acid or alkali conditions.

Surprisingly it has been found that cutting and chopping sweet sorghum by means of rapidly rotating knives or blades is a very effective method of breaking down the cane into fine fibres. Once the sweet sorghum has been cut into a fibrous state, relatively low pressures can then be used to squeeze the juice from the fibrous material. Further, a higher proportion of the sugar ' juice available in the cane can be extracted by just pressing the fibrous material as compared to conventional sugar extraction techniques which usually entail crushing pieces of cut cane under high pressure.

It has been found that industrial food processing equipment may be used to cut and chop sweet sorghum into a fibrous state. For example, equipment conventionally used to emulsify meat into a slurry for the processed food industry may be used to cut sweet sorghum into very fine fibres. This type of food processing equipment is similar to a domestic food blending machine and includes rapidly rotating blades which pass over a perforated plate and gradually cut and slice raw material down to a fine size. The perforations allow cut material to pass through the plate and out of the processing equipment once the material has been cut to a predetermined size. For example, Karl Schnell GmbH of Germany manufacture a typical industrial food processing machine, otherwise known as an emulsifier, which is normally used to emulsify fresh meat for the processed food industry, and this equipment was found to be suitable for cutting sweet sorghum into fine fibres. The Karl Schnell emulsifier, reference KS-F 320, had never been used to process tough fibrous vegetable matter; however, practical trials with sweet sorghum cane showed that the equipment was able to quickly and effectively cut sweet sorghum into fine fibrous state.

A preferred embodiment will now be described, by way of example only, wherein industrial meat emulsifiers are used to cut sweet sorghum into a fibrous state. However, it will be appreciated that the present invention is not limited to the use of such emulsifiers but rather that any cutting equipment may be used providing it is capable of cutting and chopping sweet sorghum cane into fine fibres.

According to the preferred embodiment, the sweet sorghum cane would initially be cut into small pieces approximately 13mm long by the harvesting equipment used to harvest the sweet sorghum in the field. The cut cane would be delivered to the ethanol plant immediately after harvest so that the cane would always be in a fresh condition on arrival at the plant. In addition to the pre-cut cane, other biomass material from harvested sweet sorghum plants, such as leaves and seeds, may be present or mixed with the pre-cut cane before processing at the ethanol production plant. Ripe sweet sorghum typically consists of about 75% cane, 10% leaves, 5% seeds and 10% roots by weight. Processing other biomass as well as the cane ensures that there is as much convertible lignocellulose material available as possible to produce bioethanol.

The cut cane would be processed into fine fibres at the ethanol plant by passing the cane through coarse and fine emulsifiers combined together in series. For example, on arrival at the ethanol production plant, the 13 mm pieces of sweet sorghum cane would be transferred by screw conveyor into a coarse emulsifier, such as a KS-F 320 coarse emulsifier, where the rotating blades would reduce the 13 mm pieces of cane into small slivers/shavings approximately 5mm long. The small slivers of cane would then be transferred from the coarse emulsifier into a fine emulsifier, such as a KS-F 320 fine emulsifier, where the rotating blades in the emulsifier would reduce the cubes into very fine fibres of between lmm and 5mm in length. A major benefit of this method of processing is that the material from the fine emulsifier is in such a fine, fluffy state that a relatively light pressure is sufficient to extract the sugar juice from the fibrous material.

A further important feature is that the residual baggasse material remaining after the extraction of the juice consists of fine fibres of lignocellulosic material which are ideal for prehydrolysis with acid or alkali.

Although cane had never been processed before in the Karl Schnell emulsifiers, the trials with sweet sorghum established that the equipment was able to effectively break down the cane into a very fine fibrous state. The equipment is also compact, simple to operate, and easy to clean and maintain.

It was also established that the emulsifiers worked most effectively with sweet sorghum cane containing a large amount of moisture, presumably because the moisture encourages the cutting blades to slice through the cane and allows the blades to gradually reduce the cane into small fibres. Freshly cut sweet sorghum cane can contain up to 80% moisture and it was confirmed that fresh cane worked particularly well in the emulsifying equipment. Dry cane contains much less moisture and dry cane is therefore appreciably tougher than fresh cane.

Practical trials established that it was much more difficult for the emulsifiers to cut dry cane into a fine fibres and the cutting blades quickly showed an unacceptable degree of wear.

Efficient processing of sweet sorghum is therefore dependent on the cane being in a fresh condition and having a high moisture content. In this respect, the sweet sorghum cane from the combined cultivation and ethanol production system will be ideal because freshly harvested sweet sorghum will be delivered every day to the ethanol production plant.

The cane introduced into the emulsifiers will not only be fresh but also have high moisture and sugar contents. A further advantage of the proposed cane processing technique is that sugar juice is not released during the emulsifying process because the fibrous matter is able to hold a large amount of moisture and the juice is therefore retained inside the cut fibres.

In fact the fibrous material from the fine emulsifier is so saturated with sugar juice that very little pressure is required to squeeze the juice from the fibres; for example it is even possible to squeeze the juice from a ball of fibres by hand pressure only, which would be impossible with either cut pieces of cane or coarsely milled cane.

The juice can therefore be extracted from the fibrous material by relatively light pressure in either a screw or roller press, although laboratory trials indicated that a screw press is probably the preferable method of juice extraction. For example, fibrous sweet sorghum produced by passing pre-cut cane through combined coarse and fine KS-F 320 emulsifiers was crushed very easily and effectively by a small laboratory screw press, reference CP4, manufactured by the Vincent Corporation of the USA.

Vincent screw presses are normally used for relatively lightweight pressing operations such as the extraction of juice from easily crushed fruit and vegetables, such as citrus fruits, soft fruits and tomatoes.

The amount of juice extracted from the processed fibrous sweet sorghum cane by the CP4 screw press was exceptionally high, and a laboratory evaluation indicated that the juice from the press contained over 80% of the sugar that was originally present in the unprocessed cane. From a first aspect therefore fresh sweet sorghum is progressively reduced in size by passing pieces of pre-cut cane 13 mm in size through combined coarse and fine industrial emulsifiers until the cane is in such a fine fibrous state that a relatively light pressure by a screw or roller press is sufficient to extract a substantial amount of the sugar juice originally present in the cane.

The residual compressed cake from the Vincent screw press contained about 40% moisture. A further novel feature of the proposed method of cane processing is that the compressed cake from the screw press is easily reconstituted back into a moist fibrous state, and the moist fibre can then be pressed a second time to extract more sugar.

For example, the pressed cake is easily reconstituted by agitating the cake until it returns to a fluffy fibrous state and moisture is reintroduced back into the fibres by finely spraying the cake with water during the agitation process. Approximately 1 part water to 1 part compressed cake by weight is sufficient to return the cake to an adequately moistened fibrous state. The water reintroduced into the fibrous material picks up sugar remaining in the fibres after the first press operation, and when the damp reconstituted fibre is pressed a second time, the liquor released can contain at least a further 15% of the sugar that was originally present in the fresh cane.

Processing fresh sweet sorghum cane into very fine fibres and then subjecting the fibrous matter to a double press operation is therefore a very effective way of extracting a substantial amount of the sugar that was originally present in the cane. Potentially at least 95% of the sugar present in unprocessed sweet sorghum cane can be retrieved by the proposed technique. The sugar juice from the first and second press operations would be combined together, and after filtration and concentration the concentrated sugar juice would be in a suitable state for fermentation into ethanol. From a second aspect therefore the compressed residual cake from the first screw press operation is reconstituted back into a damp fibrous state by agitating the compressed cake and simultaneously finely spraying the cake with an appropriate amount of water.

The fibrous material can then be pressed a second time to extract more sugar juice and the proposed method of processing could potentially extract at least 95% of the sugar originally available in the fresh sweet sorghum.

As well as being extremely productive, the proposed method of cane processing and juice extraction is energy efficient. By using industrial emulsifiers to reduce the sweet sorghum cane into fine fibres, a relatively light pressure in a screw press is sufficient to extract the sugar juice from the fibrous material. It is estimated that the proposed method of processing and juice extraction will use less than 50% of the energy associated with conventional stripping, milling and high pressure juice extraction techniques.

Furthermore, the lignocellulose in the residual compressed fibre cake from the second press operation is also in an ideal state for prehydrolysis with acid or alkali, which is an essential step in an ethanol enzymatic hydrolysis production process. The cake from the second press is basically a compressed mass of fine lignocellulosic fibres, and when the cake is agitated in the prehydrolysis reactor the fibres easily separate. The fibres are then in an ideal state for effective digestion by acid or alkali to break the lignocellulosic material down into its lignin, hemicellulose and cellulose constituents.

Established prehydrolysis techniques with conventionally milled residual biomass such as, for example, shredded sugarcane baggasse, corn stover or wheat straw, can involve relatively strong solutions of acid or alkali, high temperatures, high pressures and long digestion times.

However, the lignocellulose material from the emulsified sweet sorghum is in the form of very fine fibres and the material appears to be particularly susceptible to digestion with acid or alkali. Consequently it should be possible to use relatively mild reaction conditions in the prehydrolysis reactor.

By way of example, emulsified fibrous sweet sorghum baggasse has been subjected to relatively mild prehydrolysis in the laboratory using potassium hydroxide as the digestion reactant. Prehydrolysis reactions were carried out at normal atmospheric pressure using

0.25%, 0.5% and 1% solutions of potassium hydroxide; reaction temperatures of 40⁰C, 50⁰C and 60⁰C; and reaction times of 30 minutes and 60 minutes.

Reasonable ethanol yields were achieved when the prehydrolysis substrates were subjected to enzymatic hydrolysis and fermentation, which suggests that the relatively mild prehydrolysis conditions had succeeded in satisfactorily breaking down the lignocellulose material into lignin, hemicellulose and cellulose constituents. Obviously a mild acid could have been used instead of potassium hydroxide as the digestion agent.

From a further aspect therefore the fibrous lignocellulose material in the residual compressed cake from the second screw press is in a suitable state for prehydrolysis under mildly acid or alkali conditions to separate the lignin, hydrolyse the hemicellulose into sugars and expose the cellulose for subsequent enzymatic hydrolysis into sugars. The hemicellulose and cellulose sugars would then be jointly fermented with the concentrated sugar juice extracted from the sweet sorghum to produce bioethanol.

The method of cane processing described in the invention produces high yields of sugar juice and lignocellulose, which in turn helps to produce high yields of ethanol. This is illustrated in Table 1, which gives the predicted ethanol yield from fresh sweet sorghum processed by the method described in the invention. It is assumed in Table 1 that the sweet sorghum would have been grown by the combined cultivation and integrated ethanol production system described earlier.

Table 1 Predicted Ethanol Yield

Combining the high yields of sweet sorghum that can be achieved under subtropical growing conditions with the efficient method of processing the fresh sweet sorghum at the ethanol plant will result in very high yields of ethanol. For example, the integrated process could have a potential bioethanol yield equivalent to 50,000 litres/ha/year, whereas the yield of ethanol from the fermentation of just the sugar in sugarcane or sugarbeet is normally only about 6000 litres/ha/year. Even if the baggasse from the sugarcane or the pulp from the sugarbeet were also converted into ethanol by enzymatic hydrolysis, the total yield of bioethanol would probably still be no more than 12,000 litres/ha/year, which is less than a quarter of the potential bioethanol yield that can be obtained from the efficiently processed sweet sorghum described in the invention. The sweet sorghum cane processing method will now be described in detail with reference to the schematic illustration given in Figure 1.

The sweet sorghum cane will have been cut into 13 mm pieces when harvested in the field, and the pieces of cane will be transferred by a conveyor 1 into the feed hopper 2 of a transfer elevator 3.

The elevator transfers the pieces of cane into the in-feed hopper 5 of a coarse industrial food emulsifier 4. Other biomass, such as leaves and seeds, from harvested plants may be added to the pre-cut cane in the transfer elevator 3 to ensure that as much biomass as possible is used to produce bioethanol. The coarse emulsifier 4 is driven by an adjustable motor 6. The sweet sorghum material is reduced into small slivers about 5 mm long by the coarse emulsifier 4. The slivers of material are then fed into the in-feed hopper 8 of a fine emulsifier 7, which is driven by an adjustable motor 9, and the slivers are reduced to fine fibres between 1 mm and 5 mm in length by the fine emulsifier 7.

The fibrous material is transferred to the in- feed hopper 11 of a screw press 10. The press is driven by a motor 12 and the pressure is controlled by gearing 13. The press 10 squeezes the sugar juice from the fibrous material and the juice exits the screw press at outlet 14. At least 80% of the sugar originally present in the sweet sorghum cane should be extracted by the screw press 10.

The compressed cake inside the press 10 collects at outlet 15 and is transferred into a rotary agitator 16 where the cake is reconstituted into a fibrous state and the fibres are moistened with a fine spray of water.

The damp fibrous cane is then fed into the in- feed hopper 17 of a second screw press 18 driven by motor 19 and controlled by gearing 20. The second press 18 squeezes the liquor from the fibrous material and the liquor exits the screw press at outlet 21. A further 15% of the sugar originally present in the sweet sorghum cane should be extracted by press 18, so that over 95% of the sugar originally available in the sweet sorghum should have been extracted by the double press operation. The sugar juice from the first press 10 and the liquor from the second press 18 are combined together for filtration, concentration and then subsequent fermentation by active yeast into bioethanol.

The compressed cake inside press 18 collects at outlet 22 and the cake is transferred to the in- feed hopper 23 of a transfer elevator 24. The elevator 24 transfers the cake into a prehydrolysis reactor 25 where agitation reconstitutes the cake into fine lignocellulosic fibres. Mildly acid or alkali conditions 26 in the reactor are then sufficient to break down the fibrous lignocellulose into lignin, hemicellulose and cellulose constituents.

The invention therefore provides an effective method of processing sweet sorghum biomass material that allows a substantial amount of the sugar available in the sweet sorghum to be efficiently extracted from the sweet sorghum cane. The lignocellulose material in the residual baggasse from the juice extraction process is also in a fine fibrous state that is ideal for prehydrolysis with mild acid or alkali to separate the lignin, hydrolyse the hemicellulose into sugars and expose the cellulose for subsequent enzymatic hydrolysis into sugars. Although the invention is primarily aimed at processing sweet sorghum cane, the principles of the invention could probably be applied to other energy plant species, such as sugarcane, where it is desirable to remove as much sugar juice as possible from the biomass feedstock to maximise the yield of ethanol that can be obtained from sugar fermentation. In an integrated ethanol production process the residual baggasse from the sugarcane would also be in a suitable fibrous state for effective prehydrolysis with a mild acid or alkali. Although the present invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as set forth in the accompanying claims.

Claims

Claims:

1. A method of processing sweet sorghum biomass material for sugar extraction comprising cutting said biomass material into a fibrous state.

2. A method as claimed in claim 1, wherein the biomass material comprises sweet sorghum cane.

3. A method as claimed in claim 1 or 2, wherein the biomass material comprises leaves and/or seeds.

4. A method as claimed in claim 1, 2 or 3, wherein sweet sorghum biomass material is continuously fed into cutting equipment and cut material continuously leaves said cutting equipment.

5. A method as claimed in claim 4, wherein said cutting equipment comprises blades or knives for cutting said biomass material.

6. A method as claimed in claim 4 or 5, wherein said cutting equipment comprises a perforated plate, and wherein the perforations are sized and shaped to allow cut material to leave said equipment once it has been cut to a size below a predetermined size.

7. A method as claimed in any preceding claim, wherein said biomass material is cut into a fibrous state by an industrial food processor.

8. A method as claimed in any preceding claim, comprising passing sweet sorghum biomass material to a first cutter to cut the material coarsely and then passing the biomass material to a second cutter to cut it into said fibrous state.

9. A method as claimed in claim 8, wherein sweet sorghum biomass material is supplied to the first cutter in pre-cut pieces.

10. A method as claimed in claim 9, wherein said pre-cut pieces have a length of about 13 mm.

11. A method as claimed in claim 8, 9 or 10, wherein the first cutter cuts the biomass material down to pieces having a length of about 5 mm.

12. A method as claimed in any preceding claim, wherein the biomass material is cut into a fibrous state having fibres of a length between 1 mm and 5 mm.

13. A method as claimed in any preceding claim, further comprising pressing the biomass material when in said fibrous state to extract sugar juice.

14. A method as claimed in claim 13, wherein the residual baggasse cake from the pressed biomass material is reconstituted back into a damp fibrous state by being agitated and moistened with water, and the damp fibrous material is then pressed a second time to extract more sugar juice.

15. A method as claimed in claim 14, wherein the cake is reconstituted into a damp fibrous state by agitating the cake and finely spraying the cake with approximately 1 part water to 1 part cake during the agitation process.

16. A method as claimed in claim 14 or 15, wherein at least 80% of the sugar available in the original sweet sorghum cane is extracted by the first press and at least a further 15% of sugar is extracted by the second press, so that in total at least 95% of the available sugar is extracted from the sweet sorghum.

17. A method as claimed in any of claims 13 to 16, wherein the first and/or second pressing operation is performed by a screw press.

18. A method as claimed in any of claims 13 to 17, wherein the sugar juice from the first and/or second press operation is filtered, concentrated and fermented to produce bioethanol.

19. A method as claimed in any preceding claim, wherein the biomass material is processed to be suitable for lignocellulosic hydrolysis.

20. A method as claimed in any of claims 13 to 18, wherein at least some of the compressed cake from the first and/or second press is reconstituted back into a fibrous state suitable for prehydrolysis with mild acid or alkali.

21. A method as claimed in claim 20, wherein the cake is reconstituted into the fibrous state by being transferred to a prehydrolysis reactor, wherein it is stirred in a mild solution of acid or alkali.

22. A method as claimed in claim 21, wherein the mildly acid or alkali conditions in the prehydrolysis reactor are sufficient to separate the lignin from the lignocellulose, convert the hemicellulose into sugars and expose the cellulosic material for subsequent enzymatic hydrolysis.

23. A method as claimed in claim 22, wherein the cellulose from the prehydrolysis treatment is subjected to enzymatic hydrolysis to convert the cellulose into sugars.

24. A method as claimed in claim 23, wherein the cellulose sugars, hemicellulose sugars and sugar juice pressed from the biomass material are jointly fermented into ethanol.

25. A method of extracting sugar from sweet sorghum biomass material comprising pressing sugar juice out of material that has been cut into a fibrous state.

26. A method as claimed in claim 25, further comprising reconstituting the pressed biomass material back into a damp fibrous state and then pressing further sugar juice out of said biomass material.

27. A method of processing sweet sorghum comprising subjecting sweet sorghum biomass material that has been cut into a fibrous state to acidic or alkali conditions so as to separate the lignin from the lignocellulose, convert the hemicellulose into sugars and expose the cellulosic material for subsequent enzymatic hydrolysis. 95

28. A method as claimed in claim 27, wherein the cellulose is subjected to enzymatic hydrolysis to produce fermentable sugars.

29. A method as claimed in claim 27 or 28, wherein said fermentable sugars and/or said hemicellulose sugars are fermented to produce ethanol.

30. A method of processing sweet sorghum biomass material wherein material initially chopped into small pieces in the field is progressively cut and sliced in industrial food emulsifying equipment until the material is in such a fine fibrous state such that a relatively light pressure in a press is sufficient to extract a substantial amount of the sugar juice from the material and the residual fibrous baggasse is in an appropriate condition for acid or alkali prehydrolysis and then enzymatic hydrolysis.

31. A method as claimed in any of claims 25 to 30, wherein said biomass material comprises cane.

32. A method of processing biomass material for sugar extraction comprising cutting said material into a fibrous state.

33. A method of extracting sugar from biomass material comprising pressing sugar juice out of said material once it has been cut into a fibrous state.

34. A method of processing biomass material comprising subjecting biomass material that has been cut into a fibrous state to acidic or alkali conditions so as to separate the lignin from the lignocellulose, convert the hemicellulose into sugars and expose the cellulosic material for subsequent enzymatic hydrolysis.

35. A method as claimed in claim 32, 33 or 34, wherein said biomass material comprises sugar bearing cane.

36. A system for processing sweet sorghum biomass material, said system comprising means for cutting said biomass material into a fibrous state and means for pressing the fibrous matter to extract sugar juice.

37. A system as claimed in claim 36, wherein said biomass material comprises sweet sorghum cane.

38. A system as claimed in claim 36 or 37, comprising a first press for pressing sugar juice out of the cane when in said fibrous state.

39. A system as claimed in claim 38, comprising means for reconstituting the residual compressed cake from the press into a damp fibrous state by agitation and spraying with water.

40. A system as claimed in claim 39, comprising a second press for pressing sugar juice out of the damp reconstituted fibrous material.

41. A system as claimed in any of claims 36 to 40, further comprising a prehydrolysis reactor for reconstituting compressed cake into a fibrous state by agitating the cake so that the lignocellulose material in the cake is in a suitable fibrous state to be readily broken down by mildly acid or alkali conditions into lignin, hemicellulose and cellulosic constituents.

42. A system as claimed in claim 41, further comprising means for subjecting said cellulose to enzymatic hydrolysis to produce fermentable sugars.

43. A system as claimed in any of claims 36 to 42, further comprising means to ferment said sugar juice and/or hemicellulose sugars and/or said fermentable sugars to produce ethanol.

44. A system for processing biomass material comprising cutting the biomass material into pieces approximately 13 mm long in the field during harvesting and then passing the biomass material through combined coarse and fine industrial food emulsifiers to progressively reduce the biomass material into very fine fibres approximately lmm to 5mm in length.

45. A system for processing biomass material, said system comprising means for cutting said biomass material into a fibrous state and means for pressing the fibrous matter to extract sugar juice.

46. A system as claimed in claim 45, wherein said biomass material comprises sugar bearing cane.