Cross-Reference to Related Applications

[0001] The present application claims priority from Australian Provisional Patent Application No 2021901513, filed on 21 May 2021, the contents of which are incorporated herein by reference in their entirety.

Technical Field

[0002] The disclosure herein relates to an organic waste processing device and method. The device and method have been developed primarily for processing food waste and will be described herein in that context.

Background

[0003] There is a demand for diversion of organic waste, such as food waste, from landfill and the creation of a circular economy.

[0004] Conventional technologies for diverting food waste from landfill have limitations in terms of the amount of food waste they can process per day, as well as in terms of energy and water consumption.

[0005] One such conventional technology is digesters. Microorganisms/microbes in the digester process the food waste prior to the processed food waste being discharged. The processed food waste output from conventional digesters typically requires further processing to comply with environmental standards for discharge to sewer. The amount of waste conventional digesters can process per day is also limited, typically being around 400kg per day.

[0006] Another such conventional technology is dehydrators. Food waste is dehydrated in the dehydrator over a period of around 24 hours to convert the food waste into mulch. A disadvantage of dehydrators is that they consume a lot of electricity and can only process a limited amount of waste per day, typically around 400kg per day.

[0007] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims.

Summary

[0008] Disclosed herein is an organic waste processing device, comprising: a comminutor comprising: a drum for receiving organic waste, the drum having an inlet for receiving organic waste for comminution and an outlet for discharge of comminuted organic waste; one or more blades rotatably mounted within the drum for comminuting the organic waste; and an anaerobic digester comprising: a tank having an inlet in fluid communication with the outlet of the drum for receiving comminuted organic waste therefrom and an outlet for discharge of liquid from the tank; wherein a maximum invert level of the outlet of the tank is lower than a maximum invert level of the inlet of the tank to define a hydrocarbon trap therebetween; and an upstream end of the outlet of the tank is below the maximum invert level of the outlet of the tank.

[0009] A downstream end of the inlet of the tank may be below the maximum invert level of the outlet of the tank. Accordingly, in such embodiments, the downstream end of the inlet is, during operation, submerged in liquid in the tank. [0010] The tank may have a capacity that is at least 10 times greater than the capacity of the drum, or at least 20 times greater than the capacity of the drum or at least 30 times greater than the capacity of the drum. The tank may also have a capacity that is less than 100 times greater than the capacity of the drum or less than 50 times greater than the capacity of the drum.

[0011] The drum may have a capacity of less than 100 litres. In some embodiments, the capacity of the drum may be no more than about 60 litres. For example, the capacity of the drum may be between 50 litres and 60 litres. In such embodiments, the tank may have a capacity of around 2000 litres or 3000 litres.

[0012] The rotational speed of the blade(s) may be at least 1000 RPM.

[0013] The device may comprise a dispensing unit configured to dispense a biological accelerant for acting on the comminuted organic waste. An amount of the biological accelerant dispensed by the dispensing unit may be based on an amount of the organic waste in the drum or an amount of the organic waste being delivered to the tank per unit time. The amount of the biological accelerant dispensed may be approximately 0.05 to 0.5 mL/kg of the organic waste in the drum or of the organic material being delivered to the tank per unit time. In some embodiments, the dispensing unit may dispense the biological accelerant into the drum after comminution of the organic waste. In other embodiments, the dispensing unit may dispense the biological accelerant into the tank or during flow of the comminuted organic waste from the outlet of the drum to the tank.

[0014] The upstream end of the outlet may be located approximately half way between a floor of the tank and the maximum invert level of the outlet of the tank. The downstream end of the inlet and the upstream end of the outlet may be located at opposite ends of the tank. The downstream end of the inlet and the upstream end of the outlet may be spaced apart by at least 1500 mm. [0015] The device may comprise a water supply line for connection to a water supply, the water supply line being connected to at least one outlet that discharges into the drum. The at least one outlet may comprise a spray nozzle. The device may be configured to discharge water from the water supply line into the drum before or during comminution of the organic waste. The device may be configured to discharge additional water from the water supply line into the drum, after comminution of the organic waste, to flush the drum.

[0016] A pump may be provided for pumping the comminuted organic waste from the outlet of the drum to the tank. The pump may be a positive displacement pump, such as a progressive cavity pump.

[0017] The device may comprise a first sensor for measuring an amount of settled material accumulated on a floor of the tank.

[0018] The device may comprise a controller for controlling actuation of the blade(s). In embodiments that comprise the dispensing unit, the controller may also control the dispensing unit. In embodiments that comprise the pump, the controller may control the pump. The controller may be responsive to a second sensor that detects information relating to the amount of organic waste in the drum. In embodiments that comprise the water supply line, the controller may control discharge of water from the water supply line to the drum. An amount of the water discharged into the drum may be based on an amount of the organic waste in the drum. The amount of water discharged into the drum may be approximately 30 to 80 mL/kg of the organic waste in the drum. The controller may be responsive to a third sensor that provides information indicating whether a lid for closing the inlet of the drum is in a closed position and the controller may prevent operation actuation of one or more other components of the device, such as the blade(s) and/or the pump if the information from the third sensor indicates that the lid is not in the closed position. A fourth sensor may be provided to detect information relating to the load required to rotate the blade (s). The controller may be configured to stop actuation of the blade(s) and cause a warning signal to be transmitted if the information from the fourth sensor indicates that the load is above a predetermined value. In embodiments that include the pump, the controller may be configured to stop actuation of the blade (s) and actuate the pump if the information from the fourth sensor indicates that the load is below a predetermined value. In embodiments comprising the water supply line, the controller may be configured to cause the additional water from the water supply line to be discharged into the drum after comminution of the organic waste. The controller may comprise a programmable logic controller (PLC).

[0019] A liquid recycling conduit may hydraulically connect the outlet of the tank to the water supply line, optionally via a filter.

[0020] Also disclosed herein is an organic waste processing method, comprising: providing an organic waste processing device as defined in paragraph [0008] above; filling the tank to an operational level with water; inputting a batch of organic waste into the drum via the inlet of the drum; rotating the blade(s) to comminute the organic waste in the drum; discharging the comminuted organic waste into the tank via the outlet of the drum and the inlet of the tank; dispensing a biological cleaner for acting on the comminuted organic waste, the biological cleaner being dispensed: into the drum after comminution of the organic waste; or into the tank; or into the comminuted organic waste during its passage from the outlet of the drum to the tank; and repeating the steps from the inputting step onwards for one or more further batch of organic waste.

[0021] The method may comprise closing the inlet of the drum before rotating the blade(s). [0022] The method may further comprise any of the additional limitations recited in paragraphs [0009] to [0019] above.

[0023] The method may comprise maintaining liquid in the tank at a pH of around 6.

[0024] Also disclosed herein is one or more further invention comprising any novel combination of steps, features, integers, compositions and/or compounds disclosed or indicated in this patent specification, including in the drawings.

[0025] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Brief Description of Drawings

[0026] One or more embodiment of a device and method embodying principles disclosed herein will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic view of an organic waste processing device embodying principles disclosed herein;

Fig. 2 is a view of the comminutor and pump of the device of Fig. 1, a housing of the comminutor being shown partly cut away; and

Fig. 3 is a schematic vertical cross sectional view through the comminutor of

Fig. 2.

Description of Embodiments

[0027] Referring to the drawings, there is shown an organic waste processing device 100, comprising a comminutor 110 for comminuting organic waste, specifically food waste, and an anaerobic digester 120 for digesting comminuted food waste fed to it from the comminutor. [0028] Comminutor 110 comprises a drum 112 having an inlet 112a for receiving organic waste for comminution and an outlet 112b for discharge of comminuted organic waste. One or more blades 114 are rotatably mounted within the drum 112 for comminuting the organic waste. A lid 116 is coupled to the drum 112, the lid being movable between an open position for opening and the inlet 112a and a closed position for closing the inlet. Drum 112 may, for example, be of plastics material or a suitable grade of stainless steel, such as grade 304 stainless steel.

[0029] Anaerobic digester 120 comprises a tank 122, an inlet 124 for delivering comminuted organic waste from comminutor 110 to tank 122 and an outlet 126 for discharge of liquid from tank 122. Upstream end 124a of inlet 124 is in fluid communication with outlet 112b of drum 112 and downstream end 124b of inlet 124 is located inside tank 122. Upstream end 126a of outlet 126 is located inside tank 122 and downstream end 126b of outlet 126 is located outside tank 122. A maximum invert level or weir 126c of outlet 126 is lower than a maximum invert level 124c of inlet 124 of the tank to define a hydrocarbon trap therebetween. Upstream end 126a of outlet 126 is below maximum invert level 126c, ideally being located around half way between the floor of tank 122 and maximum invert level 126c such that outlet 126 draws liquid from around mid-height. Downstream end 124b of inlet 124 is below maximum invert level 126c such that, during operation, end 124b is submerged in liquid in tank 122. Downstream end 124b of inlet 124 and upstream end 126a of outlet 126 are located on opposite ends of tank 122 and, ideally, are spaced apart by at least 1500 mm. This reduces risk of discharge of comminuted organic waste into tank 122 disturbing fluid near upstream end 126a of outlet 126 and that the comminuted organic waste is resident in tank 122 for long enough for it to be sufficiently anaerobically digested. For similar reasons, one or more baffles may also be provided in tank 122. In operation, discharge of a volume of comminuted organic waste into tank 122 causes an equivalent volume of liquid in tank 122 to be displaced and discharged via outlet 126. In some embodiments, an ACO Passavant “EcoJet” grease separator may be used as digester 120. [0030] The time taken to comminute a batch of organic waste in drum 112 is many times less than the time taken for the comminuted organic waste to be anaerobically digested in tank 122. Accordingly, tank 122 has a capacity that is at least 10 times, and in some embodiments at least 20 or 30 times, greater than the capacity of drum 112. Typically, drum 112 has a capacity of around 40 L to 60 L, so as to be able to contain about 35 kg to 55 kg of organic waste, which is about the maximum safe weight for a person to carry. In the illustrated embodiment, drum 112 has a capacity of 60 L and tank 122 has a capacity of 2000 L or 3000 L. For a tank 122 of this capacity containing around 800 to 1000 kg of the comminuted organic waste, sufficient anaerobic digestion of the comminuted organic waste is achieved within about 48 hours. In other embodiments, a hopper may be provided to receive organic waste for comminution, the hopper having an outlet that discharges into inlet 124 of drum 112. In such embodiments, the hopper may have a larger capacity than drum 112 and waste for comminution may, for example, be emptied into the hopper by a mechanical bin lifter.

[0031] Blades 114 are rotated by a drive shaft 118 of an associated motor 119. During commiution, drive shaft 118, and thereby blades 114, rotate at approximately 1440 RPM.

[0032] A dispensing unit 130 is provided for dispensing a biological accelerant containing microbes for acting on the comminuted organic waste. An amount of the biological accelerant dispensed by dispensing unit 130 is based on an amount of the organic waste in drum 112 or an amount of the organic material being delivered to tank 122 per unit time. In the illustrated embodiment, the biological accelerant is BIO BLITZ™ BIOLOGICAL ACCELERANT 20:1, which is available from Bio Natural Solutions Pty Ltd in Tullamarine, Victoria, Australia. For this particular biological accelerant, the amount dispensed is approximately 0.5 mL/kg of the organic material in the drum or of the organic material being delivered to the tank per unit time. In the illustrated embodiment, dispensing unit 130 dispenses the biological accelerant into drum 112 after comminution of the organic material. However, in other embodiments, dispensing unit 130 dispenses the biological accelerant into tank 122 or during flow of the comminuted organic material from outlet 112b of drum 112 to tank 122. [0033] Device 100 has a water supply line 140 for connection to a water supply, such as mains water. Outlets 142, which in the illustrated embodiment are spray nozzles, are connected to supply line 140 and discharge water from supply line 140 into drum 112. As will be discussed further below, water from supply line 140 is discharged into drum 112 before or during comminution to create a slurry with the comminuted organic waste, and also after comminution to flush drum 112.

[0034] Pump 150 of device 100 is provided for pumping the comminuted organic waste from outlet 112b of drum 112 to tank 122. In the illustrated embodiment, pump 150 is a progressive cavity pump. However, it may alternatively be another type of positive displacement pump or a non-positive displacement pump, such as a centrifugal pump.

[0035] A controller 160, which in the illustrated embodiment is a programmable logic controller (PLC), is provided to control various components of device 100. In the illustrated embodiment, controller 160 controls motor 119 to actuate blades 114, as well as controlling dispensing unit 130, valves of water supply line 140 to control discharge of water therefrom into drum 112, and pump 150. Controller 160 is responsive to a sensor 162 that detects information relating to the amount of organic waste in the drum 112. In the illustrated embodiment, sensor 162 detects the weight of the organic waste based on the volume of organic material in drum 112. The amount of water discharged from water supply line 140 into drum 112 is approximately 30 to 80 mL/kg of organic material in drum 112. Controller 160 is responsive to a sensor 164 that provides information indicating whether lid 116 is in the closed position, and prevents actuation of blades 114 if the information from sensor 164 indicates that lid 116 is not in the closed position. Controller 160 is also responsive to a sensor 166 that detects information relating to the load required to rotate blades 114. In the illustrated embodiment, sensor 166 detects the current draw on motor 119. Controller 160 is configured to stop actuation of blades 114 and cause a warning signal to be transmitted if information from sensor 166 indicates that the current draw is above a predetermined value, being 9 Amps for the 3 kW motor used in the illustrated embodiment. A current draw of above 9 Amps is indicative of blades 114 being jammed, thereby causing motor 119 to work harder than expected. Controller 160 is configured to stop actuation of blades 114 and actuate pump 150 if, during comminution, information from sensor 166 indicates that the current draw is below a predetermined value, being 3 Amps for the 3 kW motor used in the illustrated embodiment. A current draw of below 3 Amps is indicative of the organic waste having been sufficiently comminuted. Sufficient comminution, at which a nominal particle size of the organic waste is no more than around 1 mm, is typically achieved within about 30 seconds. After comminution of the organic waste, controller 160 is configured to cause additional water from water supply line 140 to be discharged to flush drum 112. A sensor 168 is provided for detecting information relating to an amount of settled material accumulated on a floor of tank 122. In the illustrated embodiment, sensor 168 comprises a guided radar level transmitter for detecting a height of the settled material. Controller 160 may cause a signal to be transmitted, for example to trigger removal of the settled material, if sensor 168 indicates a predetermined amount of settled material has accumulated on the tank floor. One or more flow and/or pressure sensor may be provided in a liquid flow conduit between drum outlet 112b and tank inlet 112 to measure to facilitate detection of blockages in the liquid flow path or malfunction of pump 150. Controller 160 may be configured to cause an alarm to issue and/or deactivate device 100 based on feedback from the one or more flow and/or pressure sensors.

[0036] In some embodiments, a liquid recycling conduit hydraulically connects tank outlet 126 to water supply line 140, optionally via a filter. In such embodiments, a pump for pumping the recycled liquid along the liquid recycling conduit may be controlled by controller 160.

[0037] Many steps of a method of operating device 100 will be apparent from the device description presented above. However, some aspects of the operating method will now be further described. Tank 120 is filled with water to the maximum invert level 126c, which defines an operational level of liquid in tank 120. A batch of organic waste is input into drum 112 via inlet 112a. Lid 116 is closed. Comminution is commenced by an operator entering a start command, such as by pressing a start button, or automatically upon closing of lid 116. Controller 160 causes water from supply line 140 to be discharged into drum 112 and actuates motor 119 to rotate blades 114 to comminute the organic waste in the drum 112. Comminution stops when sensor 166 indicates that current draw on motor 119 has fallen below 3 Amps. Controller 160 causes additional water from supply line 140 to be discharged to flush drum 112, and actuates pump 150 to discharge slurry of comminuted organic waste and water from drum 112 into tank 122, the slurry passing via drum outlet 112b and tank inlet 122a. Controller 160 causes dispensing unit 130 to dispense the biological accelerant for acting on the comminuted organic waste, the biological accelerant being dispensed: into drum 112 after comminution of the organic waste; or into tank 122; or into the comminuted organic material during its passage from drum outlet 112b to tank 122.

The steps from input of the organic material into drum 112 onwards are repeated, on an as needs basis, for further batches of organic waste. For optimum efficacy of the biological accelerant, the liquid in tank 122 is maintained at a pH of around 6.

[0038] Output from device 100 described above has been found to comply with the quality requirements set out in the table below.

[0039] It will be appreciated that the exemplary embodiment(s) described above provide numerous advantages, including: output complies with quality standards indicated above, which are indicative of quality requirements required for direct discharge to sewer; capacity to process around one tonne of food waste per day; controller 160 and the sensors to which it is responsive facilitate simplicity of use, operator safety and energy and water efficiency; comminutor 110 is compact, being around the size of a domestic washing machine, thereby facilitating its installation in commercial kitchens; capacity of comminutor drum 112 being limited to no more than around 60 litres facilitates a user manual fdling drum 112 with organic waste from a correspondingly sized container without having to lift more than about 55 kg.

[0040] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.