Technology Field

[001] The present system and method relates to field of composting of organic waste, where composting is the process of breakdown of organic waste into compost or humus.

Background

[002] Compost is organic matter that has been decomposed and recycled as a fertilizer for agricultural uses. Compost is a key ingredient in organic farming and soil treatments. In one example, composting is achieved by making a heap of wetted organic matter, such as leaves, and food waste and waiting for the materials to break down into humus. This process occurs over a period of weeks or months. State of art systems achieve composting in much shorter periods by employing a closely monitored process with measured inputs of water, air, and carbon-rich and nitrogen- rich materials. The composting process is further aided by adding shredded plant matter, adding water and by ensuring proper aeration by regularly agitating the mixture.

[003] Example of base materials for composting are; domestic organic waste (food waste); animal waste (manure); sludge (municipal or industrial); and animal carcasses. Sludge is solid organic matter created as part of the wastewater treatment in wastewater treatment plants (WWTP). It originates from solids and biomass that sediment in the bio-reactors and sedimentation tanks. The transformation of sludge into compost is especially interesting as a means of reducing waste products.

[004] Excess sludge volume, to be disposed from the WWTP comprises 1 -2% of the wastewater volume and is usually treated within the WWTP to class B sludge. Class B sludge (bio solids) is obtained via aerobic or anaerobic digestion of organic waste by microbes and bacteria, and can be transformed to class A sludge (as defined in EPA act 503) permitted for agricultural use, by composting processes. Class A sludge is defined by the EPA as having no more than 1000 Mean Potential Number over gram of Dry Matter (MPN/gr DM) of fecal Coliform bacteria and no more than 3/4 MPN/gr DM of salmonella bacteria. Composting is acknowledged as an environmentally friendly and economical method of transforming sludge into viable material. In EPA act 503, in-Vessel composting is defined as a viable method of transforming class B sludge to class A sludge. The sludge must be retained at the composting reactor at over 55 degrees Celsius for at least a period of 72 hours.

[005] Conventional composting through open piles (windrows) requires significant land area. An alternative method is an in-vessel apparatus, such as rotary drum. In one example the rotary drum is arranged about a horizontal or slightly inclined axis and has an inlet and outlet ports. The drum and rotation are designed to enable oxygen to reach all the particles of the sludge or material to be composted

[006] State of art composting systems designed to operate with a base material of sludge suffer from several shortcomings:

[007] Introduction of material into the composting drum is difficult due to the high water content of the sludge. Manual material introduction is labor-intensive, while the use of machinery is challenging due to high water content and concerns over spillage;

[008] The premixing of sludge and plant matter is done by large mechanical devices such as tractors. State of art mixing results in large aggregates of material which are unsuitable for composting;

[009] State of art solutions have no process control over the base material and minimal control and monitoring during the composting process. Control and

monitoring is critical to meet strict environmental standard and ensure harmful bacteria has been eliminated.

[0010] The system and method described in this disclosure overcome the problem and deficiencies of state of art composting systems. Description of Figures

[001 1 ] FIG. 1 is an example of a state of art system for composting of organic waste;

[0012] FIG. 2 is an example an enhanced system for composting of organic waste;

[0013] FIG. 3A is an example of a side view of the feeding unit of the bulk agent material;

[0014] FIG 3B is an example of a top view of the feeding unit of the bulk agent

material;

[0015] FIG. 4 is an example of the mixing unit;

[0016] FIG. 5 is an example of a side view of the enhanced system for composting of organic waste;

[0017] FIG 6. is an example of a view of cut AA of the enhanced system for

composting of organic waste showing details of sensor locations;

[0018] FIG. 7 is an example of a side view of the enhanced system for composting of organic waste showing details of the outlet port; and

[0019] FIG. 8 is an example of control flow for operating the enhanced system for composting of organic waste

Description

[0020] This document describes a system and method for reducing organic waste to compost and which overcomes the shortcomings and problems of state of art solutions. FIG. 1 is an example of a prior art composting system. Organic waste is transported via an organic waste feeder (101 ) to a holding area (103), where bulking material is added and mixed with the organic waste. The bulking material is added and mixed by mechanical machinery such as tractors. After mixing, the tractor would deposit the mixed product in the rotating drum (105). The rotating drum (105) continuously pushes the mixed product towards the exit port and the exit conveyer (107). As the mixed material traverses the rotating drum (105) it is transformed into compost through heat and digestion processes. 21 ] FIG. 2 is an example of an enhanced system for composting of organic waste. In one example the system includes at least two material feeding mechanisms

(101 and 201 ). In one example the first feeding mechanism (101 ) is used for organic waste, and the second material feeding system (201 ) is used for bulking material. In another example additional feeding systems may be present. In another example a third feeding system is used for introducing waste paper pulp. In one example the linear speed of the material in the feeding system is one meter per second. In another example the linear speed of the material in the feeding system is between 0.5 and 1.5 meters per second. The bulking material feeding system (201 ) is connected to the mixer unit (203). In one example. The bulking material includes branches or branch parts. In one example the mixer unit (203) combines and mixes the feed materials into a homogenous mixture. In one example, the heater heats only the organic waste. The mixer unit (203) is located at the inlet port of the composter drum (205) and the mixed material is continuously fed into the composter drum (205). In another example a solar heater (21 1 ) is located adjacent to the mixer unit (203). The solar heater (21 1 ) heats the mixed material to reduce the water content as well to preheat the mixed material to enhance the process of transforming the mixed material into compost in the composting drum (205). In another example only the organic waste material is heated. In one example the composter drum (205) is rotating. The rotation of the composter drum (205) provides two functions; replacement of air around the composting mixture and forward movement of the material. Examples of rotation speed include; 12 revolutions per hour; or less than 12 revolutions per hour for example 6 revolutions per hour. The composter drum (205) includes fixtures in the inside of the composter drum (205) configure to push the composting material forwards towards the outlet port. Due to the continuous feeding mechanism and the internal fixtures, the composter drum (205) diameter (D) to length (L) ratio can be increased compared to state of art systems. In one example the diameter (D) to length (L) ratio can be larger than 1/4. In another example the diameter (D) to length (L) ratio can be 1/5 and 1/6 respectively. In one example, the composter drum (205) outlet port is connected to an outlet conveyer system (207) which loads the composted material into holding tanks. In one example the material resides in the composter drum (205) for at least three days. In one example, a bulking material holding tank (213) is used to hold bulking material prior to transport to the mixer unit (203).

[0022] FIG. 3A and B are an example of side view and top view of a feeding unit (201 ) of the bulking material. An example of a bulking material includes branches or other plant debris. The bulking material is stored in a holding tank (213 in FIG. 2). In one example the feeding unit is composed of four ratchets (31 1 , 313, 315, 317 in FIG 3B) and 2 axles (321 , 323 in FIG 3B). In another example only two ratchets are used. The number of ratchets (31 1 , 313, 315, 317 in FIG 3B) is chosen in order to reduce the static load of the bulking agent and allow larger volumes of bulking material in the vessel. In one example a motor (301 , 307 in FIG 3A) is connected to the axle and rotates the axle causing the movement of the ratchets (31 1 , 313, 315, 317 in FIG 3B) and the bulk material. In another example the feeding unit is positioned on pedestals (303, 305 in FIG 3A). In another example the pedestals (303, 305 in FIG 3A) include wheels which enable movement of the feeding unit (201 ). In one example the motor (301 in FIG 3A) is controlled by a frequency convertor. In one example the feeding unit enables the continuous operation of the system. Continuous operation supports the synchronization of the composting system operation with external sources of organic waste material, improves the conventional method of storing the materials to be composted, and reduces odors, dust and bacteria growth as well as reduce the composting time. In another example the material feeding system comprises in addition to the above a screw type conveyer which is located in the center between the ratchets.

[0023] FIG. 4 is an example of a mixer unit (203). In one example the mixer unit is includes organic waste material feeder (101 ); bulking material feeder (201 ); mixing paddles or rods (410, 412, 414, 416, 418, 420, 422, 424, 426, 428, 430, 432, 434); spoon axle (450); and mixed material feeder (440). In one example the angle of each spoon (410-434) can be adjusted to optimize the operation. The mixing paddles or rods are located on axles (450) supporting rotation in two axis. In another example the mixing paddles or rods are adjustable. The mixed material feeder (440) is connected to the entry port of the composter drum (205 in FIG. 2). In one example the mixer unit (203) produces a mixed material of sludge and bulking material, having a particle size distribution (PSD) in which the D90 (D90 is the diameter of at least 90% of the particles) is at most 31.5 mm, or at most 37.5 mm. In a further example the D95 is at most 31.5 mm, or the D98 is at most 31.5 mm. In another example the D90 is at most 37.5 mm, or at most 45 mm. In one example the lag time between completion of the premixing and introduction of the mixed material into the drum is at most 10 minutes. In another example it is at most 5 minutes. In a further example it is at most 2 minutes. In another example it is at most 1 minute or at most 30 seconds or less. The pre-mixing and short lag time prevent the excess bulking of the mixing material. Maintaining the mixed material bulk free supports enhanced aeration and introduction of oxygen to the mixture.

24] FIG. 5 is an example of a side view of an enhanced system for composting of organic waste. The system includes: organic waste material feeder (101 ); bulking material feeder (201 ); mixer unit (203); mixed material feeder (440); composter drum (205); outlet conveyer system (207); drum rotation support structures (501 , 503, 505); different sensors such as of temperature sensors (51 1 , 513, 515); level sensors (521 , 525); humidity sensor (535); motion sensor (537); and fan unit (541 ) . The organic waste material feeder (101 ) feeds organic waste materials into the mixer unit (203). Examples of organic materials include: sludge; carcasses; trash composed of fruit or vegetables refuse. The bulking material feeder (201 ) feeds bulking material into the mixer unit (203). Examples of bulking material include branches and cut wood. The mixer unit (203) combines the bulking material and organic waste material into a mixed material as described previously. The mixed material feeder (440) feeds the mixed material into the composter drum (205). In one example the composter drum (205) is rotating as described previously. The composter drum (205) rotation is supported enabled by the drum rotation support structures (501 , 503, 505). In one example the drum rotation support structures (501 , 503, 505) are wheels designed to rotate alongside with the composter drum (205). The composter drum (205) includes fixtures in the inside of the composter drum (205) which push the composting material forwards towards the outlet port. In one example, the composter drum (205) outlet port is connected to an outlet conveyer system (207) which loads the composted material into holding tanks. The temperature sensors are assembled in the composter drum (205). In one example the temperature sensors (51 1 , 513, 515) are equally spaced. In another example a first temperature sensors (51 1 ) is located at most 2 meters from one side of the composting drum (205); a second temperature sensor (513) is located +/- 1 meter of the center of the composting drum (205) and a third temperature sensor (515) is located at most 2 meters from the second side of the composting drum (205). The temperature sensors (51 1 , 513, 515) transmit the temperature in the composter drum (205) to a control unit. In one example the temperature sensors (51 1 , 513, 515) contain a wireless transmit unit which transmits the temperature measured by the temperature sensors (51 1 , 513, 515) to a control unit. In one example additional temperature sensors (51 1 , 513, 515) are located peripherally on the composter drum (205). In one example at least two motion sensors (537) are configured to measure the rotation angle of the composter drum (205). In a further example the motion sensor (537) includes a transmitter which transmits the composting drum (205) angle to the control unit. In one example the motion sensor (537) can provide a feedback for controlling the composting drum (205) rotation. In another example the composter drum (205) angle is used to determine which of the peripheral temperature sensors (51 1 , 513, 515) is in contact with the composting material. In one example only the temperature obtained from a

temperature sensor (51 1 , 513, 515) in contact with the composting material is used by the control unit. The level sensors (521 , 525) provide a measurement of the composting material height in the composting drum (205). In one example the control unit will vary the mixed material feed rate as well as the organic material feed rate and the bulking material feed rate to achieve a target composting material level. In another example the humidity sensor (535) provides the controller unit with a measurement of the humidity in the composting drum (205). In one example the controller unit will operate a fan unit (541 ) or change the composting drum (205) rotation speed according to the measurements from the various sensors.

[0025] To sum, one example of a system for composting of organic waste comprising of: a bulking material feeder (201 ); an organic waste material feeder (101 ); a mixer unit (203); wherein the bulking material feeder (201 ) and the organic waste material feeder (201 ) are connected to the mixer unit (203); a composting drum (205); an outlet conveyer system (207); and wherein the mixer unit (203) and outlet conveyer system (207) are connected to the composting drum (205). In an additional example the bulk material feeder is includes agriculture or industrial waste or combinations of agriculture and industrial waste. In an additional example the mixer unit (203) includes two or more mixing paddles or rods (410, 412, 414, 416, 418, 420, 422, 424, 426, 428, 430, 432, 434 in FIG. 4) and the mixing paddles or rods (410, 412, 414, 416, 418, 420, 422, 424, 426, 428, 430, 432, 434 in FIG. 4) are configured to rotate along two axis or more. In an additional example mixer unit includes a solar heating unit (21 1 in FIG. 2). In a further example the composting drum (205) has a diameter to length ratio greater than 4.

[0026] In another example the system for composting of organic waste comprising of; a bulking material feeder (201 ); an organic waste material feeder(201 ); a mixer unit (203); wherein the bulking material feeder (201 ) and the organic waste material feeder (101 ) are connected to the mixer unit (203); a composting drum (205); an outlet conveyer system (207); wherein the mixer unit (203) and outlet conveyer system (207) are connected to the composting drum (205); a control unit; wherein the composting drum (205) contains; two or more sensors (51 1 , 513, 515, 521 , 525, 535, 537); a fan unit (541 ); and wherein the control unit receives data from the sensors (51 1 , 513, 515, 521 , 525, 535, 537) and controls at least one of the following; the composting drum (205) rotation speed; operation of the fan unit (541 ); operation speed of bulking material feeder (201 ); operation speed of mixer unit (203); and operation speed of organic waste material feeder (101 ); In an additional example the two or more sensors (51 1 , 513, 515, 521 , 525, 535, 537) are any or combinations of; temperature sensor; motion sensor; level sensor; and humidity sensor. In an additional example the two or more sensors include a wireless transmitter for sending data to the control unit. In additional example the control unit includes at least one wireless receiver.

[0027] FIG 6. is an example of a cut away view ( AA in FIG. 5) of the enhanced system for composting of organic waste showing details of sensor locations. In one example one or more of the temperature sensors (513, 603, 613) are peripherally attached to the composting drum (205). Motion sensor (537) provides the information about the rotation angle of the composting drum (205).

[0028] FIG. 7 is an example of a back view of the enhanced system for composting of organic waste showing details of the outlet port. In one example end wall includes a rectangular opening which is covered with a sliding door (701 ). Granulator (707) is constructed of extruding elements which granulate and break up the compost. In one example the extruding elements have a length of at least 4 cm, a width of at most 1 cm. The extruding elements can be constructed of metal rods or pipes. In one example the sliding door (701 ) is contained between two rails (703, 705). The composted material is released by moving the sliding door (701 ) up.

[0029] FIG. 8 is an example of control flow for operating the enhanced system for composting of organic waste. In one example the control flow is initiated with block (901 ) in which the various system parameters are initialized and the system may run self tests to verify the operation of the various system elements. The main loop is initiated with block (903). In one example block (903) comprises of measuring the sensor groups described in figure (5). Block (905) utilizes the measured parameters to calculate various composting process variables. Examples of variables include; temperature (T), Volume (V), Humidity (H). Block (915) checks if the volume is less than a predefined minimum (Vmin) and if it is starts block (907) which is used to operate the feeding unit (201 FIG 3). Block (917) checks if the volume is more than a predefined maximum (Vmax) and if it is starts block (909) which is used to stop the feeding unit (201 FIG 3). Block (919) checks if the Temperature is below a predefined minimum (Tmin) and if it is it operates block (91 1 ) which operates an alarm. In one example the alarm is activated only after a predefined time the temperature is below Tmin. Block (921 ) checks if the temperature is above a predefined maximum (Tmax) or the humidity is above a predefined maximum (Hmax) and if either of these checks is positive it operates block (913) which operates the fan unit (541 in FIG. 5). After block (921 ) the flow returns to block (903).

[0030] In one example the base materials includes dewatered sewage sludge. In another example the base materials can include any organic material comprising of at least 15% organic material with said organic material comprising at least 13% solids, and no more than 50% solids. Further base material includes a bulking agent, which is mainly biological fiber or vegetable waste. Additional examples of feeding materials include paper mill sludge, domestic organic materials, vegetable waste, animal carcasses, food and beverage sludge and other materials characterized in organic content exceeding 15% by weight.

[0031 ] In one example, the sensors (51 1 , 513, 515, 521 , 525, 535, 537) provide

monitoring information which is used by the system to control the volumetric ratio between the bulking agent and the biomass sludge according to predetermined values. In another example the values of the bulking agent and the biomass sludge are determined by the operational parameters of the feeding systems. Examples of values include; volumetric ratios of less than 2:1 , less than 1.75:1 , less than 1.6: 1 , or less than 1.5: 1 ; while maintain a minimum value of more than 0.5: 1 , more than 1 : 1 , more than 1.2:1 , more than 1.3:1 , or more than 1.4:1.

[0032] Examples of measuring the particle size distribution (PSD) of the bulked

mixture are: a sieve system such as a vibrating sieve system is used to characterize the PSD. For example, the top sieve may have a standard sieve designation of 75 mm according to ASTM specifications, E1 1 -04. A second sieve may have a standard ASTM sieve designation of 50 mm, and a third sieve may have a standard ASTM sieve designation of 31.5 mm. Standard sieves of 45 mm or 37.5 mm may be used.

[0033] In another example the volume of bulking agent is dynamically controlled in accordance with the temperature and moisture measurements.

[0034] In another example oxygen is introduced by fans pushing air into the

composting drum in accordance with temperature and moisture measurements. [0035] In one example the material temperature sensors verify that the material has been processed for 3 day at more than 55°C as required by the standards.

[0036] It is clear that in the implementation of the apparatus and method, many

modifications could be made to the system and method. It should be considered that all modifications and alterations of the system and method are falling within the scope of this document.