METHOD FOR THE PRODUCTION OF BIO-ETHANOL

The present invention relates to a method for the production of bio-ethanol and in particular to a method for the production of bio-ethanol from sugar beet. According to the present invention there is provided a method for the production of bio- ethanol comprising the steps of: (i) hydroponically growing a crop; (ii) extracting sugar from the biomass of the crop; (iii) fermenting and distilling the extracted sugar to produce bio-ethanol; and (iv) using carbon dioxide and/or water from step (iii) in step (i).

During fermentation, sugars are converted to ethanol through the action of yeast. For every 1 Kg of ethanol produced close to 1 Kg of carbon dioxide is released. By combining the steps of (i) hydroponically growing a crop; (ii) extracting sugar from the biomass of the crop; (iii) fermenting and distilling the extracted sugar to produce bio-ethanol, the method of the present invention advantageously enables carbon dioxide released during fermentation to be captured and re-used during step (i) to increase the rate of growth of the crop. Carbon dioxide released in step (iii) may be introduced into air surrounding the crop in step (i) in order to increase the rate of photosynthesis of the crop. For example, carbon dioxide released during step (iii) may be vented into a polytunnel, greenhouse or other building or structure in which a crop is hydroponically grown in step (i). Alternatively or in addition, carbon dioxide released during step (iii) may be bubbled through or otherwise introduced into feed water used to hydroponically grow a crop in step (i). Carbon dioxide produced during fermentation of the extracted sugar in step (iii) may also be captured and compressed for subsequent use in, for example, the production carbonated beverages.

By combining the steps of (i) hydroponically growing a crop; (ii) extracting sugar from the biomass of the crop; (iii) fermenting and distilling the extracted sugar to produce bio-ethanol, the method of the present invention also advantageously enables water in the 'spent wash' remaining after distillation to be captured and re-used during step (i), thereby reducing the overall water requirements of the method.

The use of one or more by-products from step (iii) in step (i) advantageously improves the overall efficiency of the method of the present invention. Preferably, the method comprises using both carbon dioxide and water from step (iii) in step (i). To facilitate step (iv) and to eliminate or reduce the need for transportation and storage of carbon dioxide and/or water from step (iii) prior to use in step (i), steps (i), (ii) and (iii) of the method of the present invention are preferably carried out in close proximity.

The crop may be any crop comprising fermentable sugars and/or starches or cellulose that may be readily converted into fermentable sugars. Preferably, the crop has a high sugar content. Preferably, the crop is a root crop. More preferably, the crop is sugar beet. Most preferably, the crop is a summer variety of sugar beet such as, for example, Yvetta, Bandit and Opta. Summer varieties of sugar beet and seasonal varieties of other crops may advantageously be hydroponically

grown out of season in step (i) of the method of the present invention. Summer varieties of sugar beet advantageously have a higher sugar content than other varieties of sugar beet and, as described further below, may be hydroponically grown all year round.

By hydroponically growing a crop in step (i), the method for the production of bio-ethanol of the present invention provides several advantages over known methods for the production of bio- ethanol from crops grown in soil using conventional arable farming techniques.

Hydroponically growing a crop allows the crop to be harvested more frequently. For example, using conventional arable farming techniques sugar beet typically grows over a period of seven to eight months, and so an arable orgeoponic sugar beet crop can only be harvested once a year. In contrast, it has been found that sugar beet can be grown hydroponically in less than four months, and so a hydroponic sugar beet crop can be harvested three or more times a year. By hydroponically growing a crop in step (i), the method of the present invention thereby enables increased quantities and rates of bio-ethanol production to be achieved compared to known methods for the production of bio-ethanol from geoponic crops. Furthermore, where the crop is sugar beet or another root crop, hydroponically growing the root crop in step (i) of the method of the present invention advantageously allows better utilisation of land area than growing the root crop using conventional arable farming techniques, where land usage is limited by the requirement for crop rotation. By hydroponically growing a crop in step (i), the method of the present invention also enables the amount of bio-ethanol that can be produced from a given area of land to be dramatically increased compared to known methods of producing bio-ethanol from geoponic crops.

In addition, hydroponically growing a crop utilises less water than growing a crop in soil using conventional arable farming techniques. Typically, hydroponically growing a crop requires only about 10% of the water that is required to grow the same crop using conventional arable farming techniques. Step (i) of the method of the present invention may, therefore, be carried out in arid areas that are unsuitable for the growth of crops using conventional arable farming techniques.

A crop grown in soil using conventional arable farming techniques must also be cleaned with water prior to extracting sugar from the biomass of the crop. By hydroponically growing a crop in step (i), the method of the present invention reduces or substantially eliminates the need to clean the crop with water between step (i) and step (ii) thereby advantageously reducing the overall water requirements of the method. Furthermore, hydroponically growing a crop advantageously results in the whole of the crop, including the roots, being available for processing. The roots of crops grown using conventional arable farming techniques, which are buried in soil, are destroyed during harvesting. A crop is hydroponically grown in step (i) of the method of the present invention using a nutrient solution. The blend of nutrients and nutrient strength may be advantageously optimised in order to maximise the amount of sugar extractable from the biomass of the crop in step (ii), and thus

the yield of bio-ethanol in step (iii). For example, the blend of nutrients and nutrient strength can be optimised in order to maximise the sugar content of a hydroponically grown root crop, such as sugar beet. To ensure that optimum growing conditions are maintained through the different growth phases of the crop, the blend of nutrients in the nutrient solution used in step (i) of the method of the present invention may be varied over time.

Through optimisation of the blend of nutrients and nutrient strength in step (i) of the method of the present invention it has been found that a hydroponically grown crop may be harvested continuously. The method of the present invention thereby advantageously allows bio-ethanol to be produced continuously. In preferred embodiments of the method of the present invention in which steps (i), (ii) and (iii) are carried out in close proximity, continuous harvesting of a crop hydroponically grown in step (i) also advantageously eliminates the need for storage of the crop.

Preferably, step (i) comprises hydroponically growing a crop using continuous flow solution culture. More preferably, step (i) comprises hydroponically growing a crop using a nutrient film technique (NFT). Step (i) may, however, comprise hydroponically growing a crop using other techniques such as, for example, flood and drain (ebb and flow) techniques or aeroponics.

The method may further comprise: (v) decomposing biomass from the crop to produce methane; (vi) generating heat and/or power from methane produced in step (v); and (vii) using heat and/or power generated in step (vi) in step (i) and/or step (iii).

The method of the present invention is preferably used for the production of bio-ethanol for use as a biofuel. The method of the present invention may, however, also be used for the production of bio-ethanol for other purposes such as, for example, the manufacture of alcoholic beverages.

According to the present invention there is also provided a method of hydroponically growing sugar beet comprising use of a nutrient solution having a conductivity factor (CF) of between about 25 and about 50.

Preferably, the nutrient solution has a conductivity factor (CF) of between about 25 and about 45, more preferably of between about 35 and about 45, most preferably of about 45.

It has surprisingly been found that sugar beet may be advantageously grown hydroponically using nutrient solutions having higher nutrient concentrations than expected based on the maximum nutrient concentrations of nutrient solutions that may be used when hydroponically growing other crops. Silverbeet and potatoes are, for example, typically hydroponically grown using nutrient solutions having conductivity factors of 18 to 23 and 20 to 25, respectively.

The growth rate of sugar beet hydroponically grown using higher strength nutrient solutions (i.e. nutrient solutions having high conductivity factors) is advantageously increased in every area (leaf, root and tuber) compared to the growth rate of sugar beet hydroponically grown using lower strength nutrient solutions (i.e. nutrient solutions having lower conductivity factors).

In addition, the average final size of sugar beet hydroponically grown using higher strength

- A - nutrient solutions is advantageously significantly increased compared to the average final size of sugar beet hydroponically grown using lower strength nutrient solutions. For example, the average final size of sugar beet hydroponically grown by NFT using a nutrient solution having a CF of 45 has been found to be 82% larger than the average final size of sugar beet hydroponically grown in the same manner using a nutrient solution having a CF of 25.

The sugar content of sugar beet hydroponically grown using higher strength nutrient solutions is also advantageously slightly increased compared to the average final size of sugar beet hydroponically grown using lower strength nutrient solutions. For example, the sugar content of sugar beet hydroponically grown by NFT using a nutrient solution having a CF of 45 has been found to be 9% higher than the sugar content of sugar beet hydroponically grown in the same manner using a nutrient solution having a CF of 25.

Preferably, the method comprises hydroponically growing sugar beet using continuous flow solution culture. More preferably, the method comprises hydroponically growing sugar beet by a nutrient film technique (NFT). The method may, however, comprise hydroponically growing sugar beet by other techniques such as, for example, flood and drain (ebb and flow) techniques or aeroponics.

Preferably, the method comprises hydroponically growing a summer variety of sugar beet such as, for example, Yvetta, Bandit and Opta.

Preferably, the method comprises hydroponically growing sugar beet in containers. Preferably the method further comprises using perlite to support the hydroponically growing sugar beet.

Preferably, the method further comprises cropping the sugar beet after between about 3 months and about 4 months.

According to the present invention there is further provided a method of hydroponically growing sugar beet comprising germinating non-encapsulated seed of a summer variety of sugar beet.

Sugar beet grown in soil using conventional arable farming techniques is normally grown from encapsulated or pelletised seed having a protective coating of insecticide and pesticide. When hydroponically growing sugar beet in accordance with the methods of the present invention, it has been found that the protective coating of insecticide and pesticide of encapsulated seed disadvantageously delays germination.

The germination time for sugar beet hydroponically grown from non-encapsulated seed in accordance with the method of the present invention is advantageously up to three times shorter than the germination time for sugar beet hydroponically grown from encapsulated seed. For example, the germination time for non-encapsulated seed of a summer variety of sugar beet in rockwool has been found to be between about 3 and about 7 days, while the germination time for encapsulated seed of a summer variety of sugar beet in rockwool has been found to be between

about 9 and about 21 days.

The non-encapsulated seed may be germinated in any suitable hydroponic growing medium such as, for example, rockwool, perlite or coir. Preferably, the method comprises germinating the non-encapsulated seed in rockwool, more preferably in rockwool cubes, most preferably in about 1.25 cm (about 0.5 inch) rockwool cubes.

The use of rockwool cubes advantageously facilitates transportation of the germinated seed from, for example, a germination tray to a pot or other container, as well as placement of the germinated seed at a specific level in a pot or other container to promote tuber development.

By germinating non-encapsulated seed of a summer variety of sugar beet in rockwool, embodiments of the method of the present invention advantageously enable a 100% germination rate to be achieved.

The methods of the present invention will be further described with reference to the following specific example:

Non-encapsulated summer variety sugar beet seed is initially germinated in about 1.25 cm (about 0.5 inch) rock wool cubes on germination trays. After 3 to 7 days, the rock wool cubes and germinated seed are transferred from the germination trays to pots.

The sugar beet plants are hydroponically grown in the pots in polytunnels by a nutrient flow technique with a nutrient solution having a conductivity factor of 45. The plants are supported while growing in the pots by perlite. The sugar beet plants reach full maturity and are cropped after three to four months. The sugar beet plants are clean so when cropped no cleaning of the plants is required.

The cropped sugar beet plants are sliced into cossettes from which sugar is extracted in water at about 70 ⁰ C. The raw juice obtained is purfied by treatment with milk of lime and carbon dioxide and then filtered to produce thin juice. The thin juice is evaporated to produce thick juice, which is diluted and then fermented and distilled to produce bio-ethanol in a conventional manner. It will also be appreciated that in alternative embodiments of the method of the present invention, bio- ethanol may be produced by fermenting raw or thin juices obbtained by extracting sugar from the biomass of the crop.

Carbon dioxide produced during fermentation of the diluted thick juice is captured and vented into the polytunnels in which the sugar beet plants are housed during the main growth phase in order to increase the rate of photosynthesis of the hydroponically growing sugar beet plants.

While the methods of the present invention have been exemplified above with reference to hydroponically growing crops using a nutrient film technique, it will be appreciated that the methods may also comprise hydroponically growing crops using other techniques such as, for example, flood and drain (ebb and flow) techniques or aeroponics.

Furthermore, while the method for the production of bio-ethanol of the present invention has been exemplified above with reference to the production of bio-ethanol from hydroponically grown

sugar beet, it will be appreciated that the method may also be used to produce bio-ethanol from other crops.