WO2020153845A1

WO2020153845A1 - Method for producing a slurry suitable for fermenting, a system there for and a slurry suitable for fermenting

Info

Publication number: WO2020153845A1
Application number: PCT/NL2020/050036
Authority: WO
Inventors: Johannes Wouterus Van Groenestijn; Johan Pieter Marinus Sanders
Original assignee: Stichting Wageningen Research
Priority date: 2019-01-25
Filing date: 2020-01-24
Publication date: 2020-07-30
Also published as: NL2022452B1; EP3914687A1

Abstract

The present invention relates to a method for producing a slurry suitable for fermenting, a system therefore, and such slurry. The slurry is preferably suitable for storage. The method of the invention comprises the steps of: - providing a slurry of fermentable sugars from an at least one carbohydrate containing agricultural crop and/or residue; - concentrating the slurry of fermentable sugars; - substantially sterilising the concentrated slurry of fermentable sugars; and - providing the sterilised slurry of fermentable sugars to a fermenter, wherein the concentrated and substantially sterilised slurry comprises at least 20 wt% fermentable sugars.

Description

METHOD FOR PRODUCING A SLURRY SUITABLE FOR FERMENTING, A SYSTEM THEREFOR AND A SLURRY SUITABLE FOR FERMENTING

The present invention relates to a method for producing a slurry, with the slurry preferably suitable for fermenting, a system therefor and a slurry composition obtainable by the method according to the invention.

Commodity chemicals are widely used as resources. These chemicals have a major impact on the environment as these chemicals are often derived from oil. This present

production/harvesting of resources provides several (severe) disadvantages, such as the increase of waste, pollution and the relatively high emission of carbon dioxide over the lifetime.

Even if these chemicals are biodegradable, they are not biobased and their production often produces more greenhouse gases that may end up in the environment. Instead of ending up in the environment as pollution, such chemicals can be burned or recycled. However, burning leads to emission of carbon dioxide, whereas recycling is labour intensive. Also, many conventional manufacturing processes are well established and it is hard to compete in price with alternative processes, for example alternative processes that are based on a biobased economy, wherein resources are produced/harvested sustainably.

An objective of the present invention is to provide a method for producing a slurry, preferably suitable for fermenting, that obviates or reduces the aforementioned problems and provides a slurry that is suitable for fermenting in a cost effective manner.

This objective is achieved with the method according to the invention for producing a slurry, and more specifically a method comprising the steps of:

providing a slurry of fermentable sugars from at least one carbohydrate containing agricultural crop and/or residue;

concentrating the slurry of fermentable sugars;

substantially sterilising the concentrated slurry of fermentable sugars; and providing the sterilised slurry of fermentable sugars to a fermenter,

wherein the concentrated and substantially sterilised slurry comprises at least 20 wt% fermentable sugars.

According to the invention a carbohydrate containing agricultural crop and/or residue is provided as a slurry. This slurry is a (viscous) mixture of a pulverized/mashed solid and a liquid. The carbohydrate containing agricultural crop and/or residue is also referred to as carbohydrate- rich feedstock or feedstock. The slurry of fermentable sugars comprises mainly monosaccharides and/or oligosaccharides and/or polysaccharides. Preferably, the slurry of fermentable sugars comprises monosaccharides and/or oligosaccharides, such as disaccharides. This slurry is preferably suitable for fermenting. Examples of carbohydrate containing agricultural crop and/or residue of which the monosaccharides and/or oligosaccharides and/or polysaccharides can be obtained are beet, corn, wheat, grass, rapeseed meal, sunflower meal, potato, grass whey, products which passed the best before date such as bread, cookies, bakery products, candy residues, wheat B starch, wheat C starch. Furthermore, the monosaccharides and/or oligosaccharides and/or polysaccharides can be obtained from vegetable waste or residue.

An advantage of the method according to the present invention is that the fermentable sugars from such carbohydrate containing agricultural crop and/or residue may contain impurities, while still providing an efficient fermentation process. As a result, no severe purification of the fermentable sugars needs to be performed, thereby reducing costs. More specifically, the micro- organism(s) in the fermentation process select and use the sugar components that are relevant for them. The remaining material can optionally be used for energy production, for example. This may involve a secondary fermentation process. Conventional chemical catalysis requires a supply of fluids and/or components and/or reactants that are more pure, and therefore less available and more costly.

The slurry is treated in order to concentrate and sterilise the slurry. This will result in a concentrated slurry which is easy to store. Storage enables providing a manufacturing process with a substantially constant feed over a prolonged period of time. This renders the manufacturing process more economically feasible. The concentrated and sterilised slurry comprises at least 20 wt% fermentable sugars, and optionally ethanol as conserving/preserving substance. This enables efficient treatment. Ethanol (and/or lactic acid) will improve the conservation in the storage process. The role and advantages in relation to ethanol (and/or lactic acid) will be discussed in more detail later in this text.

Sterilising the slurry of fermentable sugars renders the slurry of fermentable sugars suitable for a subsequent fermentation process. Sterilisation in the context of the present invention relates to raising the temperature to inactivate micro-organisms. Due to the sterilisation, the slurry of fermentable sugars will not degrade over time due to (other) micro-organisms. Although direct further treatment is presently preferred, this also improves storage possibilities. In the fermentation process, preferably only one micro-organism is active, for example. The micro-organism can be chosen from a group of appropriate micro-organism, such as yeasts, Clostridium, Escherichia coli, Lactobacillus. Such micro-organisms can produce metabolites under anaerobic conditions.

Furthermore, aerobic organisms can also be used, such aerobic organisms are for example Trichoderma, Aspergillus, Streptomyces, and Bacillus.

Storage and sterilisation makes the slurry of fermentable sugars available all year round at a more or less constant price, or at least during an extended time period. As a result, factories have reduced down times and/or can have a reduced capacity. The yearly required amount of fermentable sugars will be equal, but the effect of seasonal campaigns/fluctuations is reduced.

In a preferred embodiment of the invention the method comprises the step of mixing a stored slurry having a relatively high carbohydrate/fermentable sugar concentration with a slurry having a relatively low' carbohydrate/fermentable sugar concentration. For example, since the evaporator/sterilizer is preferably in operation during the whole year, preferably at full capacity, a buffer of carbohydrates at high concentrations can be built up during the year. Using this buffer will enable to deliver a carbohydrate concentration, preferably as high as 30wt%, to the main fermenter, also when fresh incoming carbohydrates enter the storage system at low' concentrations. Such low concentrations occur especially early in the beet campaign or when using other residues with low carbohydrate concentrations at specific periods of the year. This year round fermentation results in a year round production of fermentation residues and therefore a constant biogas production throughout the year from this fermentation residue. This improves overall process efficiency and/or reduces investment cost. In addition, this reduction in investment cost makes it feasible to provide relatively small-scale facilities, for example for fermentation and/or down stream processing facilities, close to the harvesting location(s) of the carbohydrate containing agricultural crop, for example. To prevent contamination, the sterilised slurry is preferably supplied directly, or within a limited period of time, to the fermenter for the fermentation step.

In one of the presently preferred embodiments of the invention, concentrating and sterilising are carried out in the same device, for example an evaporator. This will result in a reduction of the operation costs and thus the production is even more efficient. This further improves possibilities for the aforementioned relatively small-scale facilities. In a presently preferred embodiment distilling is performed to enable recycling of ethanol, for example. It will be understood that the different steps presented in the method according to the invention can also be unit operations that can optionally be performed separately and/or in different operation units.

In one of the presently preferred embodiments the slurry is stored relatively close to the harvesting location(s). Amongst other things, this significantly reduces the need and costs for transport of feedstock and the residues of the fermentations.

Thereafter, according to the method of the invention, the slurry can be provided to a fermenter. Fermentation, and in particular anaerobic fermentation, of this slurry enables a cost effective production of a wide range of (bulk) chemicals. In a preferred embodiment of the invention, the fermentation takes place in one or more relatively small-scale fermentation factories which can be realised close to where the carbohydrate containing agricultural crop and/or residue are harvested and treated to the appropriate slurry for fermenting. Such factories annually produce 40,000 ton (chemical) end-product, for example. It will be understood that this contributes to a cost effective manufacturing of the desired commodity chemicals, such as ethanol or lactic acid, wherein lactic acid is also referred to as building block. Alternative chemicals that can be produced as commodity chemicals and/or building blocks include, mono ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1 ,4-butanediol, 2,3-butanediol, other diols, fumaric acid, succinic acid, terephthalic acid, furandicarboxylic acid, other di-acids, diaminobutane, diaminobenzene, diamino pentane, other diamino compounds, aniline, isoprene, ethyl acetate, and other esters, citric acid, itaconic acid, amino acids for example. It will be understood that building blocks are chemical building blocks.

Furthermore, the residue from the fermentation process can be used to produce biogas, which is converted into electricity and heat, and a digestate with minerals and/or fermentation resistant organic matter. The digestate can be returned to agricultural land as fertilizer without the need to concentrate. Therefore, the use of this slurry of fermentable sugars is more environmental efficient. In fact, the slurry of fermentable sugars results in less pollution such as emission of carbon dioxide.

Surprisingly it was found that a concentrated and sterilised slurry with 20 wt% of fermentable sugars can effectively be used in the fermentation process.

In a presently preferred embodiment of the invention the method additionally comprises the step of storing the slurry prior to the concentrating step.

An advantage of storing the slurry prior to concentrating is that the slurry in practice may comprise an amount of ethanol of less than 30 wt%. In such case, the initial amount of the slurry that is stored has an (initial) ethanol amount of less than 30 wt%. For example, a 10 wt% ethanol content may also be used especially in a situation with high sugar and/or salt content in combination with a low' pFl of about 4.5. This further conditions the slurry for the further treatment steps in the manufacturing process, thereby rendering this process more efficient. Preferably, the ethanol content is chosen dependent on the material and storage period, in order to stop the growth of micro-organisms. Furthermore, low temperatures of the slurry are preferred. This results in further conditioning of the slurry for the further treatment steps in the manufacturing process, thereby rendering this process more efficient.

In a presently preferred embodiment of the invention, storing of the slurry comprises the step of providing one or more additives/preservatives to the storage process.

The use of additives may improve or preserve the quality of the slurry in the storage process. Preferably, storing of the slurry comprises the step of providing ethanol and/or lactic acid prior to and/or in the storage process, wherein providing ethanol and/or lactic acid comprises external addition of the aforementioned compound and/or internal in-situ formation using micro- organisms. Ethanol and/or lactic acid will improve the conservation in the storage process.

As a further advantage, ethanol and/or lactic acid are readily available and are

biodegradable under normal circumstances. Therefore, the use of these components renders the provision of the slurry of fermentable sugars even more environmental efficient, and further reduces pollution such as emission of carbon dioxide and. Additives/preservatives are for example ethanol, other alcohols, organic acids (lactic acid) and esters thereof, salts and combinations thereof.

A further advantage of the use of ethanol as additive in the storage process is the possibility to evaporate the ethanol in the sterilisation process and collecting the ethanol, for example by distillation. This enables the provision of a recycle-loop for ethanol in the process. It will be understood that such ethanol recycle-loop would render the process cost effective and will improve its sustainability as no, or less, external additives would be required.

A further advantage of the use of ethanol or lactic acid as additive and/or preservative in the storage process is that the ethanol and/or lactic acid that is not recycled and/or that is not used as nutrient in the main fermentation will be converted into biogas.

Alternatively, or in addition thereto, the step of storing the slurry comprises the additional step of enzymatic hydrolysis of the slurry involving the step of adding enzymes and/or in-situ formation of enzymes using micro-organisms. This will result in an efficient and environmental friendly hydrolysis of the slurry. An advantage of the in-situ hydrolysis of the slurry of fermentable sugars with enzymes is that the added amount of additives can be reduced. This can be achieved by increasing the concentration of monosaccharides and, therefore, the osmotic pressure, which has a preservative effect. As a further advantage, the slurry of fermentable sugars is preserved by the in- situ produced ethanol.

Enzymes produced by micro-organisms suitable for hydrolysing the (poly)saccharides are for example pectinase(s), cellulase(s), hemicellulase(s), amylase(s), glucoamylase(s) and combinations thereof. Preferably the hydrolysis is performed at a temperature of 10 °C - 70 °C and a pH of 3.5 - 8.0, more preferably a pH of 4.5 - 6.0. In a preferred embodiment at least a part of the enzymes are produced internally, for example by a Lactobacillus that produces pectinases. In another preferred embodiment, the Lactobacillus produces the enzymes as well as the lactic acid.

In a further embodiment of the invention, concentrating the slurry of fermentable sugars comprises evaporation of solvent, and the method further comprises the step of removing ethanol from the slurry involving distillation. Evaporation and distillation are preferably integrated in one step.

According to the invention, the slurry of fermentable sugars can be distilled in order to remove additives and/or solvents. The additives and/or solvents are soluble in water, wherein the water can also act as solvent. An example of such an additive and/or solvent is ethanol.

An advantage of removing ethanol from the slurry of fermentable sugars is that the ethanol can be recycled. As a result the costs of producing a slurry suitable for fermenting are reduced. A further advantage is that the ethanol can be sold separately as a commodity chemical. It is well known that ethanol is a widely used commodity chemical. For example, ethanol is widely used as green solvent or biofuel.

Preferably, the concentration of the slurry is operative during more than 6000 hours per year, preferably more than 7000 hours, and more preferably more than 8000 hours per year. It is noted that the method according to the invention can be operated (semi)-continuous over the entire year.

In a further preferred embodiment of the invention, the content of fermentable sugars is preferably at least 25 wt%, more preferably at least 27 wt%, most preferably at least 30 wt%.

An advantage of fermentable sugars with at least 25 wt%, more preferably at least 27 wt%, most preferably at least 30 wt% is that the slurry of fermentable sugars comprises a low percentage of fermentable sugars and can still be used for anaerobic fermentation, compared to the percentages required for aerobic fermentation.

A further advantage of fermentable sugars of at least 25 wt%, more preferably at least 27 wt%, most preferably at least 30 wt% is that the main fermentation product is present at least at a concentration of 150 gram per litre.

In a further preferred embodiment of the invention, the method further comprises the step of fermenting the slurry of fermentable sugars.

According to the invention the slurry of fermentable sugars can be used in a fermentation process. Fermenting the sugars will result in valuable products, for example commodity chemicals and/or biogas.

Preferably, the fermentation process is an anaerobic fermentation. This will allow a fermentation process in the absence of free oxygen. It was shown that such anaerobic fermentation of the slurry is both effective and efficient.

In a further preferred embodiment of the invention, the method further comprises the step of producing building blocks and/or commodity chemicals, such as lactic acid and/or ethanol and/or one or more of the earlier mentioned alternative building blocks and/or commodity chemicals. Such components result from the fermenting process.

In a further preferred embodiment of the invention the fermentation is performed under anaerobic conditions in order to obtain high conversion of the carbohydrates into commodity chemicals and/or building blocks. This will result in lower capital investments compared to aerobic fermentation since less equipment is required in the fermentation process, such as for stirring, cooling, and compression of air.

In a further preferred embodiment of the invention the method further comprises the step of generating energy and/or heat with produced biogas in a secondary fermentation process. An advantage of fermenting the slurry of fermentable sugars is that biogas is obtained from sugars and other organic components that are not fermented in the main fermentor and are fermented in a secondary fermentor. The biogas can be used to produce electricity and/or heat. Preferably, in embodiments of the invention that benefit from the production of biogas in the process, sodium and potassium salts are avoided in the use as preservatives due to the fact these elements decrease the biogas formation.

In a further preferred embodiment of the invention, the method further comprises the step of re-using minerals and/or resistant organic material and/or preservatives, such as ethanol for example.

An advantage of the step of re-using minerals and/or resistant organic material and/or preservatives is that valuable resources can be re-used, for example by re-distributing the slurry with the valuable components, such as minerals, over the farmland without the need to concentrate in order to bring it back to the agricultural fields as is the case for large scale fermentation factories of baker’s yeast, antibiotics, organic acids, amino acids and enzymes, ethanol. This is furthermore enabled by the combination of the storage facility with the anaerobic fermentation, resulting in a higher efficiency of the production of chemical products from carbohydrates. This is especially advantageous in case of the use of relatively small-scale facilities that are located close to the harvesting locations. More specifically, in a further preferred embodiment according to the invention the residues of the slurry and/or fermentation process can be used as fertiliser for farmland. This contributes to the objective of having a more bio-based production or circular process, as part of a circular economy.

The invention also relates to a system for treating fermentable sugars, the system comprising:

an inlet configured for receiving a slurry of fermentable sugars;

an evaporator system having a gas phase outlet and a slurry phase outlet; a sterilization system operatively connected to a concentrated slurry phase outlet of the evaporator and configured for sterilization of the concentrated slurry; and an outlet configured for providing sterilized and concentrated slurry for further treatment.

Such system provides similar effects and advantages as described in relation to the method. The system is suitable for performing the method in at least one of the embodiments of the invention.

In one of the presently preferred embodiments, the system comprises a distillation system operatively connected to a gas phase outlet of the evaporator system and configured for producing ethanol by concentrating and isolating, using a heating operation. This provides an effective means to obtain an amount of ethanol in the manufacturing process. Optionally, the ethanol is re-used in the storage process for conservation purposes. In one of the presently preferred embodiments, the evaporation (for concentrating the sugars) and distillation (to recover ethanol) is performed in a single operation unit, optionally also involving sterilization wherein temperature is raised to inactivate micro-organisms. This provides an effective system.

In one of the preferred embodiments, the system comprises a distillation system, more specifically a distillation system wherein a condenser is operatively coupled with a gas phase outlet of the evaporator. Thus, the distillation can be integrated with the evaporation, wherein the condenser is operatively coupled to the gas phase outlet of the evaporator.

It will be understood that distillation techniques known in the art may be used, wherein the technique can be used at normal or reduced pressure, for example using column or multiple column distillation.

Furthermore, in a preferred embodiment according to the invention, sterilisation of the slurry is performed whilst heating the slurry for the evaporation process.

Preferably, the system further comprises a fermenter configured for fermenting the sterilized and concentrated slurry of fermentable sugars.

The invention further also relates to a slurry composition comprising a sterile slurry of fermentable sugars suitable for storage.

Such slurry provides similar effects and advantages as described in relation to the method and/or system. This slurry of sugars is relatively stable and enables a relatively long storage period. This is specifically an advantage for small-scale facilities that are located close to the farmlands.

Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

Figure 1 schematically shows a process according to an embodiment of the invention.

Manufacturing process 2 (Figure 1 ) starts with harvesting operation 4, for example beet, com, wheat, grass, rapeseed, potato, or other carbohydrate rich feedstock. It will be understood that other suitable varieties can also be used. Harvested products 6 are provided to pulping/hammering step 8, for example in a hammer-mill. Solid parts 10 are mixed in mixing step 12 with liquid 14, such as (grass or milk) whey. Mixing 12 results in slurry 16 that contains the sugars for fermentation.

Optionally, slurry 16a is stored in storage process 18 in containers, bins or other suitable storage facility. Also optionally, additives 20 such as ethanol or lactic acid are added to storage process 18 resulting in stored slurry 16b. In the illustrated embodiment ethanol is preferred as additive 20.

In a next step, slurry 16a and/or stored slurry 16b is provided to evaporation process 22 and sterilization process 24. In the illustrated embodiment, evaporation and sterilization processes 22, 24 are performed in combined system 26, optionally in a combined process step. Optionally, evaporation process 22 also comprises distillation 23 of ethanol. This ethanol may be re-used in storage process 18.

In the illustrated embodiment, concentrated and sterilized slurry 28a is used directly in a further process (such as fermentation process 34). In an alternative embodiment, the concentrated and sterilized slurry 28 is stored in storage process 30 in a suitable storage facility. In such alternative embodiment, also optionally, additives 32 such as ethanol or lactic acid are added to storage process 30 to maintain the ethanol concentration resulting in stored slurry 28b.

In a next step, slurry 28a (and/or stored slurry 28b in case of the alternative embodiment) is treated in fermentation process 34, such as an anaerobic fermentation process, to produce desired (chemical) compounds 36, such as the building blocks that were mentioned earlier. Biogas 41 that is produced in fermenter 39 from the remaining biomass 38 from fermentation process 34 is optionally provided to heat and power plant 40 for handling biogas 41 to produce electricity 42a, and/or heat 42b and digestale with minerals 42c. Electricity 42a and/or heat 42b can be used for other processes and/or for one or more of the steps in manufacturing process 2, for example evaporation 22. Digestate 42c is preferably re-distributed over the farmlands to enable a bio-based or circular process. More specifically, digestate 42c may act as fertilizer and contribute to the next harvest 4.

In one of the presently preferred embodiments, beets or potatoes are harvested and optionally hammered. Next, a slurry is produced by liquefying the feedstock, preferably preventing addition of (too much) water, and optionally adding enzymes (although addition of enzymes is desired, it is presently preferably added after sterilization). This results in the slurry preferably comprising a sugar concentration of about 16 wt%, 18 wt%, or 20 wt%. The slurry is provided to system 26 where the slurry is concentrated in an evaporator and sterilized to kill all micro- organisms. Thus, before evaporation a sugar concentration of about 16 wt%, 18 wt%, or 20 wt% is achieved, after evaporation the sugar concentration is about 20 wt%, 25 wt%, or 30 wt%.

In this presently preferred embodiment, the slurry is stored close to the harvesting location. For example, lactic acid and/or other suitable additives are added to the storage process and/or are produced in the storage process itself by providing suitable storage conditions therefor. The slurry for fermentation 28 a,b is treated in (anaerobic) fermentation process 34 to produce one or more of the commodity chemicals and/or building blocks 36 that were mentioned earlier. Biogas 41 is produced in fermenter 39 to produce electricity 42a, and/or heat 42b and fertilizer 42c. In this embodiment, the treatment and fermentation processes are also performed close to the harvesting location. This not only reduces transport costs, it also enables easy returning of the fertilizer 42c to the land in a bio-based or circular process, without the need of (extensive) concentrating the digestate (to enable transport). Experiments have shown that especially the xylose, arabinose, glucose and fructose can effectively be converted in ethanol and lactic acid and used in production of the alternative building blocks that were mentioned earlier.

In another one of the preferred embodiments, feedstocks are being used in combination over time, optionally as a mixture. For example, a slurry may comprise a mixture of mashed beet and potato pulp and optionally grass whey concentrate.

Alternative additives 20, 32 may include ammonium carbonate that is being decomposed at suitable temperatures enabling re-using the ammonium after cooling and reformation. Other additives 20, 32 may include less preferred potassium salts and/or alternative alcohols and/or organic acids.

Examples:

In an experiment according to the invention, 500 kg of fresh beets were shredded in a refiner equipped with a 20 kW engine (Heidro, Panningen, The Netherlands). The beets were cut into pieces of about 5 by 5 by 5 centimeters before they were fed to the refiner. The capacity of the equipment was higher than 300 kg per hour. The energy required to mash 1 ton of beets was about 30 kWh. 20 kg of mashed beets were loaded into five different plastic jars.

To each jar, 3 litre of 96% ethanol was added and mixed with the mashed beets to a concentration of 12.5% v/v (10.6 wt%). Subsequently, 0,1% sulphite was added to the mixture, and this addition of sulphite was repeated after one week of storage. Different conditions were applied in the different jars.

Jar A: no addition; Jar B: no addition; Jar C: pH 8 (NaOH) and 20 gram laundry Washing Powder; Jar D pH 5 (HC1); and Jar E. pH 8 (NaOH).

For a period of nine months, each month a 20 ml sample was taken from jar B, D and E by a tube connected with a 50 ml syringe and frozen. The concentrations of sucrose, glucose and fructose were analysed by standard HPLC technology after 2000 fold dilution and calculated back to the original concentration in gram/ litre stored mashed beet:

The sucrose concentration lowers gradually in the four months of storage, because of inversion to glucose and fructose. The overall sugar content is stable over the six month period tested.

In a further experiment according to the invention, samples were stored for over two years. The content of each of the five jars was inspected after two years of storage at room temperature. The ambient temperature fluctuated over the two years between - 10 °C and 35 °C. The structure of the mash was similar as the initial structure. It was found that the pH of jar D was 4.5 and the Brix was 21.5 degrees.

In an even further example according to the invention, the enzyme incubation of

Viscozyme was analysed. 200 ml of jar D was stored for one week and incubated with 1 ml of Viscozyme L for 18 hours at 25 °C. After this incubation the beetpulp was not viscous anymore. Viscozyme L Batch KTN 02254 Novozymes > 100 FBGU/ gram was used in the experiment. Since the beets had a dry matter content of about 25% of which about 20% is pectine, the dose that was used is calculated to be 10 - 12 FBGU/ gram of pectine.

In an even further example according to the invention, ethanol fermentation was analysed.

To perform this experiment 100 ml of mashed beets front jar D were stored for two years and incubated with 0.5 ml Viscozym for one week. The mashed beet hydrolysate was incubated at 90 °C for two hours in order to pasteurise and to evaporate the ethanol. The Brix was measured to be 18 degrees. Half a gram of dried baker’s yeast was mixed in the flask containing the mashed beet juice and incubated at 30 °C. A water slot was mounted on top of the flask and after half an hour gas bubbles were observed to be formed during the next 15 hours.

The present invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.

Claims

1. Method for producing a slurry, the method comprising the steps of:

providing a slurry of fermentable sugars from an, at least one, carbohydrate containing agricultural crop and/or residue;

concentrating the slurry of fermentable sugars;

2. Method according to claim 1 , further comprising the step of storing the slurry prior to the concentrating step.

3. Method according to claim 2, wherein the storing of the slurry comprises the step of providing one or more additives/preservatives prior to the storage process.

4. Method according to claim 2 or 3, wherein the storing of the slurry comprises the step of providing ethanol and/or lactic acid prior and/or at the storage process, w herein providing ethanol and/or lactic acid comprises external addition of the aforementioned compounds and/or internal in-situ formation using micro-organisms.

5. Method according to claim 2, 3 or 4, wherein the step of storing the slurry comprises the additional step of enzymatic hydrolysis of the carbohydrates in the slurry by adding enzymes and/or in-situ formation of enzymes using micro-organisms.

6. Method according to claim 2, 3, 4 or 5, further comprising the step of mixing a stored slurry having a relatively high carbohydrate/fermentable sugar concentration with a slurry having a relatively low carbohydrate/fermentable sugar concentration.

7. Method according to any one of the preceding claims, wherein concentrating the slurry of fermentable sugars comprises evaporation of solvent, and further comprises the step of removing ethanol from the slurry involving distillation.

8. Method according to any one of the preceding claims, wherein the content of fermentable sugars preferably is at least 25 wt%, more preferably at least 27 wt%, most preferably at least 30 wt%.

9. Method according to any one of the preceding claims, wherein the agricultural crop

comprises one or more of beet, corn, wheat, grass, rapeseed meal, sunflower meal, potato.

10. Method according to any one of the preceding claims, further comprising the step of

fermenting the slurry of fermentable sugars.

11. Method according to claim 10, wherein the fermenting comprises anaerobic fermentation.

12. Method according to claim 10 or 11 , further comprising the step of production of chemical building blocks and/or commodity chemicals.

13. Method according to claim 10, 11 or 12, further comprising the step of generating energy and/or heat with biogas resulting from a secondary fermentation.

14. Method according to any one of the claims 10 - 13, further comprising the step of re-using minerals and/or resistant organic material and/or additives/preservatives.

15. System for treating fermentable sugars, comprising:

an inlet configured for receiving a slurry of fermentable sugars;

an evaporator system having a gas phase outlet and a concentrated slurry phase outlet; a sterilization system operatively connected to the concentrated slurry phase outlet of the evaporator and configured for sterilization of the concentrated slurry; and an outlet configured for providing sterilized and concentrated slurry for further treatment.

16. System according to claim 15, wherein the system further comprises a distillation system operatively connected to a gas phase outlet of the evaporator system and configured for producing ethanol by concentrating and isolating.

17. System according to claim 15 or 16, further comprising a fermenter configured for

fermenting the sterilized and concentrated slurry of fermentable sugars.

18. Slurry composition comprising a sterile slurry of fermentable sugars suitable for storage.

19. Slurry composition obtainable by the method according to any one of the claimsl - 14.