AU2008200462A1 - A method and apparatus for treating food waste - Google Patents

Description

AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Name of Applicant/s: Hy Pro Pty Ltd Actual Inventor/s: Garry Gordon Jennings and John Camilleri Address for Service is: SHELSTON IP 60 Margaret Street Telephone No: (02) 9777 1111 SYDNEY NSW 2000 Facsimile No. (02) 9241 4666 CCN: 3710000352 Attorney Code: SW Invention Title: A METHOD AND APPARATUS FOR TREATING FOOD WASTE The following statement is a full description of this invention, including the best method of performing it known to me/us: File: 56465AUP00 501437649_1.DOC5844 -2 FIELD OF THE INVENTION [0001] The present invention relates to a method and apparatus for treating food waste. [0002] The invention has been developed primarily for use with packaged food that is used to produce pet food and will be described hereinafter with reference to that application. 5 However, we appreciate that the invention is not limited to that particular field of use and is also applicable to processing unpackaged food waste for other than pets. BACKGROUND TO THE INVENTION [0003] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common 10 general knowledge in the field. [00041 The mechanisation and mass manufacture of food at respective food production sites has led to considerable advantages in consistency of product and lower unit costs of production. It has also led to the localisation of food waste, in that this now accumulates at the site rather than at the individual points of food preparation and consumption. 15 [0005] The typical approach is to have any food waste discarded along with any other waste emanating from the site. While some consideration has been given in the past to recycling the fbod waste, this proves difficult and expensive to achieve. For example, for those food products that are packaged, there is not only the usual health and safety concerns to address, but also the labour cost of removing the food from the packaging. 20 DISCLOSURE OF THE INVENTION [0006] It is an object of the present invention, at least in a preferred embodiment, to overcome or substantially ameliorate one or more of the disadvantages of the prior art or at least to provide a useful alternative. [0007] According to a first aspect of the invention there is provided a method for 25 treating food waste including: ensuring the food waste has a moisture content of less than about 50% by weight; milling the food waste to form a milled product having a first predetermined nominal diameter; drying the milled product to form an intermediate product; -3 milling the intermediate product to provide a treated product having a second predetermined nominal diameter. [00081 Preferably, the step of ensuring the food waste has a moisture content of less than about 50% includes adding dry material to the food waste. More preferably, the dry 5 material is a quantity of one or more of: the treated product; the intermediate product; other food waste; and other dry food. 10 [0009J Preferably also, the first predetermined nominal diameter is in the range of about 0.1 to 1 mm. More preferably, the second predetermined nominal diameter is about 0.1 mm to 1 mm. Even more preferably, the first predetermined nominal diameter is about 0.6 mm and the second predetermined nominal diameter is about 0.8 mm. In other embodiments the second predetermined nominal diameter is about 0.6 mm. 15 [0010] In a preferred form, the intermediate product has a moisture content in the range of about 5% to 10% by weight. More preferably, the moisture content of the intermediate product is about 6% by weight. [0011] Preferably, the step of milling the intermediate product is preceded by the step of grading the milled intermediate product, wherein only a predetermined grade of that milled 20 product provides the final product. More preferably, a plurality of grades of the milled product collectively provides the final product. Even more preferably, the remaining milled intermediate product is again treated by the process of the first aspect. [0012] Preferably also, the food waste includes one or more of: raw whole vegetable matter; 25 processed vegetable matter; processed foods; and any one or more of the above contained within packaging. [0013J Examples of whole raw vegetable matter includes corn, lettuce, beetroot, grass, fruits such as apple, banana, kiwifruit, pears and the like. Examples of processed vegetable 30 matter include hay, corn cobs, husk or kernels, apple cores, seed material from fruits and vegetables, cereal grains such as wheat, barley, Soya beans or oats, dried fruits such as sultanas, apricots, prunes, skin from fruit and vegetables such as beetroot, apple, lettuce, tomatoes, marrow and squash and the like.

-4 [00141 Examples of processed foods include: breakfast cereals; biscuits; bread; and 5 dough or other pre-mixed ingredients that are intended to be converted into any of the above processed foods. [00151 In a preferred form, the food waste is contained within packaging and the method includes: simultaneously shredding the food waste and the packaging; 10 retaining the shredded packaging within the food waste as it is formed into the milled product; and thereafter separating substantially all the shredded packaging from the milled product. [0016 Preferably, the shredded packaging is substantially unaffected by the milling of the food waste into the milled product. More preferably the separation of the shredded 15 packaging from the milled product is affected by a screening device that includes at least one screen that allows and prevents passage there through of the milled product and the shredded packaging respectively. [00171 Preferably also, the step of ensuring the food waste includes a moisture content of less that 50% by weight includes adding dry material to the food waste. More preferably, 20 the dry material includes the treated product. In other embodiments, however, the dry material includes grains - either whole or processed - hay, biscuits, and dry breakfast cereals. [0018] In a preferred form, the food waste and the dry material are mixed and matured. More preferably, the maturation occurs over 2 hours to 48 days. More preferably, the 25 maturation occurs over 4 hours to 24 hours. [0019] Preferably, the treated product is a stock feed. [0020] It will be appreciate that the term "food waste" as used in this specification is intended to include food products or ingredients that are either discarded or which are no longer deemed suitable for human consumption. A discarded food product that falls within 30 the scope of the term "food waste" may, in some circumstances, still be suitable for human consumption. For example, a packaged biscuit product marked with a given "use by" date that has not yet occurred may still be discarded and used to define food waste for the purposes of the preferred embodiments. This occurs in practice if the typical timeframe for -5 transportation to a warehouse, distribution to a retail outlet, display for sale, and storage by the end customer would culminate after the "use by" date. [0021] According to a second aspect of the invention there is provided an apparatus for treating food waste having a moisture content of less than about 50% by weight, the 5 apparatus including: a first milling station for milling the food waste to form a milled product having a first predetermined nominal diameter; a dehydrator for drying the milled product to form an intermediate product; a second milling station for milling the intermediate product to provide a treated 10 product having a second predetermined nominal diameter. [0022] Preferably, the apparatus includes a feed device for progressing the food waste to the first milling station. More preferably, the feed device includes a hopper having an inlet for receiving the food waste and an outlet for allowing the feed waste to exit the hopper at a predetermined rate. Even more preferably, the feed device includes a conveyor for 15 conveying the feed waste exiting the outlet to the first milling station. [0023] In a preferred fbrm, the feed device includes a metal trap for removing metal particles from the food waste. More preferably, the metal trap provides a magnetic field that draws magnetically permeable materials from the food waste. Even more preferably, the metal trap is an electromagnet that is suspended above the conveyor intermediate the hopper 20 and the first milling station. [0024] According to a third aspect of the invention there is provided a method of processing cooked food waste including the steps of; processing the food waste to provide a particulate material having a moisture content of less than about 13% by weight; 25 increasing the moisture content of and then pressing the particulate material to provide a pressed product; and reducing the moisture content of the pressed product to be less than or equal to 13% by weight. [00251 Preferably, the cooked food waste is derived from one or more grains. More 30 preferably, the cooked food waste is derived substantially from one or more grains. Even more preferably, the cooked food waste is derived substantially from one or more grains. In an embodiment, the food waste is derived substantially from one or more or: wheat grains; -6barley grains; oat grains; and other cereal grains. Preferably, the food waste includes one or more of: breads; biscuits; cakes; breakfast cereals; muesli bars; and the like. [0026] According to a fourth aspect of the invention there is provided an apparatus for processing cooked food waste, the apparatus including: 5 a mill for processing the food waste to provide a particulate material having a moisture content of less than about 13% by weight; a pressing station for increasing the moisture content of and then pressing the particulate material to provide a pressed product; and a dryer for reducing the moisture content of the pressed product to be less than or 10 equal to 13% by weight. [0027] According to a fifth aspect of the invention there is provided a method of producing animal food from cooked food waste derived from one or more grains, the method including: processing the food waste to provide a particulate material having a moisture content 15 of less than about 13% by weight; increasing the moisture content of and then pressing the particulate material to provide a pressed product; and reducing the moisture content of the pressed product to produce an animal food having a moisture content of less than about 13% by weight. 20 100281 Preferably, the food waste includes one or more of: breads; biscuits; cakes; breakfast cereals; muesli bars; and the like. [00291 Preferably also, at least some of the food waste is contained within packaging and the method includes the step of removing the food waste from the packaging. [0030] According to a sixth aspect of the invention there is provided an apparatus for 25 producing animal food from cooked food waste derived from one or more grains, the apparatus including: a mill for processing the food waste to provide a particulate material having a moisture content of less than about 13% by weight; a pressing station for increasing the moisture content of and then pressing the 30 particulate material to provide a pressed product; and a dryer for reducing the moisture content of the pressed product to produce an animal food having a moisture content of less than about 13% by weight.

-7 BRIEF DESCRIPTION OF THE DRAWINGS 100311 Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a high level conceptual diagram illustrating the method and apparatus for 5 treating waste food in accordance with the invention; Figure 2 is a more detailed diagram of the method and apparatus of Figure 1; Figure 3 illustrates a pre-processing step for food waste containing, or which is included within, packaging; Figure 4 illustrates a drying process for food waste that contains greater than 50% 10 moisture by weight; Figure 5 is a schematic axial cross-sectional view of the trammel screen of Figure 2; and Figure 6 is a schematic representation of a method of further processing the food waste to provide food for domestic animals. 15 [0032] It will be appreciated by those skilled in the art that all the figures are provided to assist with the understanding of the operation of the embodiments and are schematic only, and not to scale. PREFERRED MODES OF CARRYING OUT THE INVENTION [0033] Referring to Figure 1, there is schematically illustrated a process plant 1 in which 20 is performed a method for treating food waste in accordance with an embodiment of the invention. This method includes the sequential steps of: " Ensuring the food waste has a moisture content of less than about 50% by weight. This occurs through stockpiling and selective mixing with dry material at a station 2. * Milling and/or shredding the food waste, as schematically represented by a mill 3. This 25 forms a milled product having a first predetermined nominal diameter in the order of 1 mm. * Drying the milled product in a dehydrator 4 to form an intermediate product having a moisture content of about 5 to 10% by weight. * Milling the intermediate product, as schematically represented by mill 5, to provide a 30 treated product 6 having a second predetermined nominal diameter in the order of 0.6

MM.

-8 [00341 It will be appreciate that the term "food waste" includes food products or ingredients that are either discarded or which are no longer deemed suitable for human consumption. A discarded food product that falls within the scope of the term "food waste" is, in some circumstances, still be suitable for human consumption. For example, a packaged 5 biscuit product will, depending upon the jurisdiction into which it is sold, usually be marked with a given "use by" date that that is indicative of a period prior to which it should be safe to consume the product. However, in some instances the product will define all or part of the food waste notwithstanding that the use by date has not expired. This occurs, for example, if the typical timeframe for transportation to a warehouse, distribution to a retail 10 outlet, display fbr sale, and storage by the end customer would culminate too close to or after the use by date. [0035] By way of example, food waste that is able to be processed by the method of the preferred embodiment includes one or more of: raw whole vegetable matter; 15 processed vegetable matter; processed foods; and any one or more of the above that is contained within packaging. [0036] Examples of whole raw vegetable matter includes corn, lettuce, beetroot, grass, fruits such as apple, banana, kiwifruit, pears and the like. Examples of processed vegetable 20 matter include bay, corn cobs, husk or kernels, apple cores, seed material from fruits and vegetables, cereal grains such as wheat, barley, Soya beans or oats, dried fruits such as sultanas, apricots, prunes, skin from fruit and vegetables such as beetroot, apple, lettuce, tomatoes, marrow and squash and the like. [0037J Examples of processed foods include: 25 breakfast cereals; biscuits; bread; and dough or other pre-mixed ingredients that are intended to be converted into any of the above processed foods. 30 [00381 Where the food waste is contained within packaging the method of the preferred embodiment includes some pre-processing steps that will be described in more detail below.

-9 [00391 A more detailed description of the embodiment of Figure 1 will be provided with reference to Figure 2 where corresponding features are denoted with corresponding reference numerals. [0040] A plurality of spaced apart food processing plants 11, 12 and 13 are sites for the 5 production of bread products, biscuit products and canned vegetable products respectively. In other embodiments other food products are produced at plants 11. 12 and 13. While these plants are responsible for the production of large volumes of processed foods, there is also considerable food waste generated due to changes in production runs, timing issues, equipment failure, maintenance routines, quality control measures, raw material supply and 10 the like. In any event, this food waste, however generated, is transported in bulk - in this embodiment by a truck 14 - to a warehouse 15 that is part of plant 1. In other embodiments, plant I is located within or adjacent to one of plants 11, 12 or 13. There are also embodiments where plant 1 services only a single one of plants 11, 12 or 13 and is designed with a corresponding processing capacity. In other embodiments the food waste is sources 15 from alternative and/or additional plants to plants 11, 12 and 13. [00411 The bulk food waste is delivered to warehouse 15 in one of a variety of forms. Some typical examples include: biscuit products: contained within individual plastic or paper packets that are stacked on pallets 16; 20 bread products: loaves that are contained within plastic packages 17 but otherwise free; dough: bulk delivery, no packaging (not shown); and vegetable discards: bulk delivery, no packaging (not shown). [0042] The food waste that is packaged or which includes packaging is usually initially progressed through a pre-processing phase. This is particularly so in those embodiments 25 where use is made of both packaged and unpacked food waste. This pre-processing is illustrated in more detail in Figure 3, to which reference is now made and in which corresponding features are denoted by corresponding reference numerals. As shown, warehouse 15 includes a holding area 18 where a plurality of pallets 16 and packages 17 are initially stockpiled and stored. Area 18 typically includes many tonnes of bread and 30 packaging, and many hundreds of pallets. However, the quantities held are dependent upon the quantities and timings of arrival of food waste at warehouse 15 and the rate of subsequent processing of the food waste. Typically, the food waste is provided at infrequent and irregular intervals and the processing of the waste is performed at a substantially -10 constant rate. Accordingly, storage of at least some food waste in warehouse 15 is required to facilitate continuous operation of plant 1. [0043] The biscuit product is removed from pallets 16 - but not from the packaging and feed by conveyor (not shown) or other means to a shredder 20 at about 20 tones per 5 hour. The bread product is simply feed into shredder 20 at about the same rate. In the preferred embodiment different food waste is feed to shredder 20 in batches of like waste. However, a mixture of different food wastes in a single batch is undertaken in other embodiments. [0044] The feed rate for other waste product is typically different than that for the 10 biscuit product as shredder 20 has a different capacity for shredding different products. [0045] The shredder is a rotary device that provides a shredded product 21 having a nominal area of about 5 cm 2 . However, due to the very different shear strengths, brittleness and resiliencies of the materials being processed, there is significant variation in the shape of the pieces contained within product 21. While all the separate components of the material is feed into shredder 20 are substantially planar, the bread and biscuit products offer little resistance to shredding and are preferentially reduced to a generally square or rounded area of less than the nominal area mentioned above. However, the paper, plastics and other packaging, while being simultaneously shredded with the food component to form product ~21, typically includes of far greater area than the nominal area. Moreover, the action of 20 shredder 20 is such that the packaging component of the food waste is preferentially shredded into elongate strips, while the food component of the food waste is preferentially shredded into more regularly shaped pieces. [0046J As product 21 emerges progressively from shredder 20 is it deposited into a storage bin 22 where it is then metered by a bucket elevator 23 into a multi-stage trammel 25 screen 24. This screen retains includes a primary mesh of about 25 mm x 25 mm that allows substantially all of the food portion of the product to pass into a storage bin 25. The larger pieces of packaging and the minimal remaining food product are captured within screen 24 and progressively feed to a discard bin 26 for disposal. [0047] The material in bin 25 is feed next onto a vibrating screen 27 that has a mesh size 30 of about 20 mm x 20 mm to provide a pre-processed product 28. While screen 27 removes further packaging material from the product stream it will be appreciated that product 28 still includes many pieces of shredded packaging. This is particularly so for pieces of cardboard or paper packaging, as these typically are not as elongate the corresponding pieces from -11 shredded plastic packaging. That is, the less elongate pieces are more likely to find their way through screens 24 and 27. [0048] The pieces of packaging removed by screen 27 are directed to bin 26 for disposal, while the pre-processed product 28 that emerges from screen 27 is stockpiled in a 5 bin 29. For dry products such as biscuits and breads the moisture content of product 28 is typically well less than 50% and, as such, is now ready for treatment by the method of Figure 1. It will be appreciated that some bread products may be close to 50% depending upon the type of the bread and the humidity of the atmosphere that that bread has been exposed to prior to treatment with plant 1. 10 [0049] Product 28 is taken from bin 29 and provided to stockpile 2 - as best shown in Figure 2 - for assessment of its moisture content. If that content is above about 50% by weight then a moisture control process is undertaken. This process is shown schematically in Figure 4 where corresponding features are denoted by corresponding reference numerals. Similarly, for food waste that was not packaged - and which therefore has not undergone the 15 pre-processing process of Figure 3 - there is a moisture assessment made. Particularly for food waste such as dough, Soya, other grains, corn and the like, the moisture content is typically much greater than 50%. [0050] For convenience, the product being delivered for processing by the apparatus of Figure 4 will be referred to as product 28. However, it will be appreciated that term is being 20 used in a generic sense to refer to product with a moisture content of greater than 50%, whether has been through pre-processing or not. [0051] In other embodiments the threshold for moisture content is set at a level other than 50% by weight. For example, in those embodiments where it is required that less load be put on the dehydrator 4, the threshold is set at less than 40%. In one embodiment the 25 threshold is set at about 30% moisture content by weight. That is, if the moisture content exceeds that threshold the food waste is initially processed in accordance with the steps of Figure 4. In other embodiments the moisture content threshold is as low as about 20%. [0052] While it is possible to treat material having no moisture content with the preferred embodiment, this is not usually done as such material is subject to combustion. 30 Accordingly, the practical lower limit for moisture content, as used in the preferred embodiments, is about 2% by weight. For materials with a lower moisture content the moisture content is increased prior to further processing. In some embodiments the moisture -12 content is increased by adding water (or other fluid) or by adding a relatively high moisture material to the existing product. [00531 If product 28 has a high moisture content it is transferred from station 2 to an adjacent 4 nr hopper 31, as best shown in Figure 4. This transfer occurs in bulk and is 5 typically performed by a continuous conveyor and/or a front loader excavator (neither shown). 10054] Hopper 31 feeds product 28 progressively into a 5 tonne rotary mixer and blender 32 at predetermined rate that is contingent upon the make-up of the product. Blender 32 is also fed dry material that is either, or a mixture of, treated material 6 and i) another dry material 33 such as straw or hay. The resultant blended product 34 is extracted from blender 32 and transferred by a conveyor or front loader to maturation bins 35. In further embodiments use is made of blendable dry materials other than straw or hay. [0055J The blended product, in this embodiment, has a moisture content of less than 50% by weight, and preferably less than 30% by weight, as it exits blender 32. However, in 15 other embodiments that moisture content is different. [00561 Product 34 is left in maturation bins 35 to allow the moisture content to stabilise and to become more consistent throughout the product. Different blended products require different maturation times, with a typical time being within the range of about 4 and 24 hours. It will be appreciated by those skilled in the art that the maturation time will be 20 dependent upon a number of factors including the nature of the food waste being processed, the moisture content of the food waste, the homogeneity of the food waste, the environment in which the maturation occurs, amongst other things. [0057] Following the maturation period, the dried product 36 is again tested for moisture content. If this is not within the desired range the product is returned to blender 32. 25 However, if the moisture content is suitable, product 36 is returned to station 2 by way of conveyor or front loader. [00581 In other embodiments the drying of the fbod waste prior to substantive treatment is performed by a dehydrator. More preferably, that dehydrator is a continuous feed device that allows progressive processing of a batch of product 28. More preferably, the dehydrator 30 is a rotary device that is gas fired. [00591 In still further embodiments the drying occurs by thinly spreading product 28 into beds that are exposed to an environment conducive to moisture reduction. In some - 13 locations this includes ambient conditions, while in other locations it includes storage within a drying shed or other structure. [0060] In other embodiments the drying involves a combination of two or more of the options described above. 5 [0061] Returning now to Figure 2, the product at station 2 - be that product 28, product 36, or product as originally delivered by truck 14 and being otherwise unprocessed - is loaded into a 40 tonne storage bin 41 that forms a metered feed hopper onto a conveyor 42. The metering is centrally controlled and selected in accordance with the nature and composition of the product being treated. Some examples of different rates of metering 10 include: about 10 tonnes per hour for packaged bread products having a moisture content of about. 35% by weight; about 10 tonnes per hour for packaged breakfast cereals having a moisture content of about 25% by weight; and 15 about 15 to 18 tonnes per hour for packaged biscuits having a moisture content of about 10% by weight. [0062] Conveyor 42 passes through a magnetic trap to magnetically screen the food waste being processed for extracting magnetically permeable materials. The trap includes an electromagnet that is disposed immediately above conveyor 42. In other embodiments the 20 trap includes a housing through which conveyor 42 extends, and at least two magnetic field generators disposed within the housing and being located above and below the conveyor respectively for providing in combination a magnetic field for extracting the magnetically permeable material from the food waste. More preferably, the magnetically permeable material is retained in contact with the generators. Once sufficient material has built up the 25 generators are cleaned either manually or automatically. [0063] Conveyor 42 delivers the food waste into mill 3 where it is continuously and progressively milled to a nominal diameter of about 0.1 mm to 0.6 mm. However, the packaging contained within the food waste remains substantially unaffected by this milling process and is therefore now substantially larger in size than the purely food based 30 component of the waste. Particularly, due to the moisture control referred to above, the purely food component of the waste is generally in the form of a powder or a particulate, while the purely packaging component of the food waste is generally in the form of strips or -14 pieces. These strips or pieces have at least one dimension that is considerably more than 0.6 mm. [0064] For packaged food waste there will remain, given the pre-processing steps of Figure 3, very little if any of the packaging. However, the pre-processing is generally used 5 for packaged food waste that is to be blended with other food waste having very different moisture content. For those embodiments where there is a relative certainty of supply of packaged food waste of a given type, it is possible to omit the pre-processing steps of Figure 3. The moisture content of the food waste is determined by sampling the contents of selected packages. Otherwise, the food waste, together with the packaging, is bulk handled 10 into bin 41, onto conveyor 42 and into mill 3. [00651 The milled product is progressively placed on a conveyor 43 where it is transported for screening and removal of the shredded packaging. For those embodiments where the pre-processing of Figure 3 has occurred, or where the food waste is not packaged, then the screening is omitted. 15 [0066] As best shown in Figure 5, the screening and removal of the packaging occurs in this embodiment through use of a trammel screen 44. This screen includes a generally tubular inclined cylindrical body 45 having an axis 46 and which extends between a feed end 47 and a tailings end 48 that is lower than end 47. That is, axis 46 is inclined with respect to the horizontal. In this embodiment that angle of inclination is about 10", and body 45 is 20 rotated about axis 46 at about 10 rpm. In other embodiments alternative angles of inclination with respect to the horizontal and speeds of rotation are used. [00671 Body 45 includes three consecutive but equal length mesh filters 49, 50 and 51 that are progressively coarser than the preceding filter. In this embodiment, filter 49 includes a mesh size of about 25 mm x 25 mm, filter 50 includes a mesh size of about 30 25 mm x 30 mm, and filter 51 includes a mesh size of about 50 mm x 50 mm. [00681 The milled product, which is designated by reference numeral 52, is carried by conveyor 43 and feed into end 48 where it falls under the influence of gravity into contact with filter 49 which, as described above, is rotating at about 10 rpm. As the food component of the food waste contained within product 52 is substantially a powder and/or particulate, it 30 forms a filtered product 53 that falls relatively freely through filter 48 to an underlying bin (not shown). Any shredded packaging will be substantially retained within body 45 as it will be unable to pass through filter 48. Rather, that shredded packaging progresses toward end 48 under the influence of the rotation of body 45 and gravity. As this occurs, progressively -15 more of the purely food component of the product will fall through filters 50 and 51 to form filtered product 54 and 55. [00691 While a small amount of the shredded packaging will remain in products 53, 54 and 55, the far greater proportion of it is retained within body 45 until it exits end 48 as 5 shredded packaging 56. This packaging is collected in a bin (not shown) and disposed of or otherwise recycled. Typically, the proportion of packaging remaining within product 53, 54 and 55 is respectively less than 1%, 2% and 5% by weight. [0070] Referring back to Figure 2, products 53, 54 and 55 are either separately or collectively feed at a controlled rate from a hopper 61 onto successive buckets of a bucket 10 elevator 62. The bucket elevator passes the product to a constant rate auger 63 such that the product is fed into dehydrator 4 at a predetermined controlled rate. This rate will be contingent upon the products, their moisture content, and the desired moisture content after exiting the dehydrator. [0071] Dehydrator 4 extracts fluids from the product, and this fluid is directed to twin 15 cyclone separators 64 for the removal of any significant contaminants, before being passed through a biological filter 65 and into a holding pond (not shown). [0072] The product exiting dehydrator 4 is directed to a cooling chamber 66 and allowed to return to about room temperature. The moisture content of the product in chamber 66 is less than about 13%, and preferably less than about 10%. In some 20 embodiments the moisture content of the product in chamber 66 is about 5 to 8 %. [00731 Once the temperature of the product in chamber 66 has fallen sufficiently, it is placed upon a further conveyor (not shown) and once again passed through a magnetic trap 67 to draw out from the product any magnetically permeable materials. Following the screening, the product is carried by a bucket elevator 68 to mill 5. As described above, mill 25 5 provides a treated product 6 having a second predetermined nominal diameter in the order of 0.6 mm. [0074] After the treated product emerges from mill 5 it takes the form of a particulate material and is placed on a first deck screen 69 where the smaller particles - which is primarily the treated food waste - falls though the screen while the remainder - which is 30 primarily any residual packaging or other larger food waste particles - are directed to a bin (not shown). In some instances the remainder is placed at station 2 for re-processing, while in other embodiments it is disposed. In further embodiments the remainder is assessed prior to a determination being made as to whether or not re-processing is undertaken.

-16 [00751 That product which falls through screen 69 is conveyed to a second finer deck screen 70 where it is similarly processed. The product falling though screen 70 is then put in a stockpile to form the treated product 6. [0076] It will be appreciated that in some embodiments not all of the steps described 5 above are carried out. For example, in some embodiments the material exiting mill 5 is not passed through screens 69 and 70. In some embodiments, for example, only one of screens 69 and 70 are used. Moreover, in other embodiments, additional steps are used to further refine part of the process. For example, in some embodiments the product exiting chamber 66 is further milled prior to being passed into trap 67 to improve the efficacy of trap 67. 10 [0077] As mentioned above, treated product 6 is stockpiled for subsequent transportation. In some embodiments product 6 is transported in bulk by truck 71 to a feedlot for feeding directly to bovines or other animals. In other embodiments, product 6 is blended with other animal feeds and then transported. It will be appreciated that the moisture content of product remains substantially the same as when it exited dehydrator 4 15 unless there were significant environmental factors such as high humidity, for example - and will be suitable for ingestion by animals, but not so moist as to be prone to high levels of immediate fungal growth and decay. [0078] While the above embodiments have been described with specific reference to the treatment of food waste from a bakery or biscuit plant, it will be appreciated that other food 20 waste is also able to be processed. For example, the preferred embodiment of the invention is also suitable for treating food waste from: restaurants, cafes and other eating establishments; and hotels, motels, hospitals, nursing homes, schools and other facilities where large scale food preparation occurs. 25 [0079] For those embodiments where food waste 2 is primarily cooked food waste derived from grains, product 6 is particularly suitable as a source material for dog food, cat food and other pet food. This arises from the fact that the cooked food waste will have the original starches and other long-chain sugars from the grains broken down into forms significantly more digestible by domesticated animals such as dogs and cats. That is, 30 product 6, while based upon vegetable matter, provides a source material of food for pets that are carnivorous or omnivorous. [0080] The steps of processing product 6 into feed for domestic animals is described below with reference to Figure 6, where corresponding features are denoted with -17 corresponding reference numerals. Particularly, there is illustrated an apparatus 80 for producing animal food from cooked food waste derived from one or more grains. The apparatus includes process plant 1 (which in turn includes mill 5) for processing the food waste to provide a particulate material, in the form of treated product 6, having a moisture 5 content of less than about 13% by weight. A pressing station, in the form of a cold press 81, increases the moisture content of and then presses the product 6 to provide a pressed product 83. A dryer, in the form of a cylindrical gas-fired oven 84, reduces the moisture content of the pressed product to produce an animal food in the form of a domesticated dog food 85 having a moisture content of less than about 13% by weight. 10 [0081] Particulate material 6 exits plant 1 and is placed in a storage silo 86. The silo includes a chute 87 at its base from which the flow of material 6 is regulated from the silo and onto a conveyor 88. Apparatus 80 also includes a plurality of other storage silos 89, 90, 91 and 92 having respective chutes 93, 94, 95 and 96. In this embodiment the other silos store, respectively, meat and bone meal, poultry meal, a high protein meal such as feather 15 meal, and a binding agent such as benonite. The flow of the materials from each of the silos is regulated such that conveyor 88 contains about 80% of product 6, and about 5% each of the material from the other silos. In other embodiments alternative proportions are used. [0082J It will be appreciated that while in this embodiment use is made of a single conveyor 88, in other embodiments more than one conveyor is used or, alternatively, 20 different conveyances are used. [0083] The proportions of the materials from silos 86, 89, 90, 91 and 92 that are placed on conveyor 88 are transported into a mixer 97. This mixer is sized to contain about 3 tonnes of material in total, and includes load cells 98 fbr allowing an automated filling cycle. That is, use is made of a controller (not shown) that receives a signal provided by the load 25 cells for determining when mixer 97 contains about three tones of material. The controller is responsive to the signal for cutting the drive to conveyor 88 and closing chutes 87, 93, 94, 95 and 96. In some embodiments, the controller shuts to chutes prior to stopping the drive to conveyor 88 such that there is substantially no material on conveyor 88 between loads. [00841 Once mixer 97 is determined to be full, the controller actuates an electric motor 30 for driving a mixing element (not shown) within mixer 97 to allow the materials within the mixer to be homogenously distributed. In practice it has been found that a mixing time of about fifteen minutes is suitable.

-18 [00851 Once an homogenous mix is produced, the controller cuts the drive to the mixing element, and actuates a tipping member to tilt mixer 97 such that the homogenously mixed material flows into an adjacent holding bin 99. It will be appreciated that the material is still primarily a particulate - albeit generally slightly ground due to the operation of mixer 97 5 and with a moisture content of less than about 13% by weight. [0086] Bin 99 includes a chute 100 that is used to meter-out the mix into press 81 together with a flow of water 101 (or other fluid) such that the water/mix has a moisture content of about 15% to 25% by weight. In this specific embodiment, where use is made of bread to produce product 6, the moisture content of the material within press 81 is 10 maintained at about 16% to 17%. [00871 The operation of press 81 converts the particulate material into the pressed product 83. In this embodiment, product 83 is in the form of pellets that are extruded from press 81. The pellets have a moisture content of about 16% to 17% and are conveyed to oven 84 to reduce the moisture content to less than 13% by weight. In this embodiment, the 15 moisture content is reduced to about 10% to 12% by weight. [00881 Importantly, there is no need for the pellets entering oven 84 to be cooked in the oven. That is, product 6 is primarily derived from a cooked product and, as such, is an eminently more digestible form for a carnivorous animal than raw vegetable matter. As the function of oven 84 is only to reduce the moisture content, and not to cook the product to 20 make it digestible, the amount of energy required by oven 84 is considerably less than would otherwise be the case. [0089] Moreover, the operation of the oven is only to remove about the same moisture content as was provided by the addition of water 101 or other fluid. The addition of water 101 is to facilitate the operation of press 81. For if the particulate material is too dry it will 25 prematurely wear the press and, in more extreme cases, will not progress through the press. Conversely, if the particulate material is too moist, it will not form pellets. [0090] As the material being processed has a low moisture content - with the exception of the period just prior to being put into press 81 to entering oven 84 - it is quite resistant to the growth of moulds and fungi, and is suitable for storage in an intermediate or final form. 30 [00911 The pellets exiting oven 84 are cooled to ambient temperature and then conveyed to a holding silo 103 having a chute 104. The material in silo 103 is metered-out via chute 104 onto a vibrating mesh screen 105 for separating into smaller particles 106 - typically -19 powder which is directed to silo 86 - and larger particles 107 - typically pellets that are directed to a coating bay 108. [0092] A tank 109 holds about 5000 litres of oil that is fed via a drip feed distribution system 110 to bay 108. System 110 includes a plurality of outlets (three shown) for 5 dispersing the oil widely across the bay. In this embodiment use is made of cooking oil, and preferably used cooking oil. It has been found that the use of used cooking oil is advantageous not only because it allows the re-cycling of oil that would otherwise be disposed of, but because the additional materials and flavours within the oil make food 85 even more attractive to dogs and cats. 10 [0093] Bay 108 includes a mixing auger (not shown) that slowly rotates to progress particles 107 through the bay and to rotate the particles to best ensure they are all coating with the oil dispersed by system 110. [0094] The mixing auger ultimately progresses the material from bay 108 to provide food 85. This food falls into a hopper 1l to be fed into a bagging machine 112. This 15 machine doses food 85 into bags 113 that are sealed. The bags are then stacked on pallets 114 and transported to a warehouse or point of sale. 10095] Examples of the major advantages of the preferred embodiments include: " Being able to utilise waste materials to provide feed for stock and/or pets. * A relatively low energy process for converting waste to a usable product. 20 * Allowing the recovery of the high nutrient content that is contained within some food waste. e Providing a low moisture content stock-feed or pet food that has a relatively long shelf-life. * Ease of processing of packaged food through mechanised removal of the 25 waste material from the packaging. " Providing an easily digestible pet food. " Maintaining the moisture content of the waste to be low during processing to reduce the risk of growth of biological organisms within the waste. * The bulk processing of food waste. 30 [00961 Although the above embodiments of the invention has been described with reference to a specific example it will be appreciated by those skilled in the art that it may be embodied in many other forms.

Claims (8)

1. A method for treating food waste including: ensuring the food waste has a moisture content of less than about 50% by weight; milling the food waste to form a milled product having a first predetermined 5 nominal diameter; drying the milled product to form an intermediate product; milling the intermediate product to provide a treated product having a second predetermined nominal diameter.

2. An apparatus for treating food waste having a moisture content of less than about 10 50% by weight, the apparatus including: a first milling station for milling the food waste to form a milled product having a first predetermined nominal diameter; a dehydrator for drying the milled product to form an intermediate product; a second milling station for milling the intermediate product to provide a treated 15 product having a second predetermined nominal diameter.

3. A method of processing cooked food waste including the steps of: processing the food waste to provide a particulate material having a moisture content of less than about 13% by weight; increasing the moisture content of and then pressing the particulate material to 20 provide a pressed product; and reducing the moisture content of the pressed product to be less than or equal to 13% by weight.

4. An apparatus for processing cooked food waste, the apparatus including: a mill for processing the food waste to provide a particulate material having a 25 moisture content of less than about 13% by weight; a pressing station for increasing the moisture content of and then pressing the particulate material to provide a pressed product; and a dryer for reducing the moisture content of the pressed product to be less than or equal to 13% by weight. 30

5. A method of producing animal food from cooked food waste derived from one or more grains, the method including: -21 processing the food waste to provide a particulate material having a moisture content of less than about 13% by weight; increasing the moisture content of and then pressing the particulate material to provide a pressed product; and 5 reducing the moisture content of the pressed product to produce an animal food having a moisture content of less than about 13% by weight.

6. A method according to claim 5 wherein the food waste includes one or more of: breads; biscuits; cakes; breakfast cereals; muesli bars; and the like.

7. A method according to claim 5 or clam 6 wherein at least some of the food waste 10 is contained within packaging and the method includes the step of removing the food waste from the packaging.

8. An apparatus for producing animal food from cooked food waste derived from one or more grains, the apparatus including: a mill for processing the food waste to provide a particulate material having a 15 moisture content of less than about 13% by weight; a pressing station for increasing the moisture content of and then pressing the particulate material to provide a pressed product; and a dryer for reducing the moisture content of the pressed product to produce an animal food having a moisture content of less than about 13% by weight.