WO1995018679A1

WO1995018679A1 - Processing facility for disposing of infectious medical wastes and method

Info

Publication number: WO1995018679A1
Application number: PCT/US1995/000430
Authority: WO
Inventors: Robert S. Davis
Original assignee: B & B Joint Venture
Priority date: 1994-01-10
Filing date: 1995-01-10
Publication date: 1995-07-13

Abstract

A method and closed system (10) for disposing of infectious medical waste, the method includes the steps of reducing the size of the waste to small particles and indirectly heating the waste particles by contacting them with a heated surface. The heating is at a temperature and for a period of time sufficient to produce sterilization of the waste particles. The heating step includes transporting the waste particles along an indirect heating conveyor (72). Air is continuously drawn through the system to control the pressure and moisture therein.

Description

PROCESSING FACILITY FOR DISPOSING OF INFECTIOUS MEDICAL WASTES AND
METHOD
Backaround of the Invention
The present invention relates to systems and
processes for the environmentally safe disposal of
infectious medical waste.

The safe disposal of infectious medical waste has
become a major environmental and public safety concern in
recent years. Public safety concerns include the spread
of disease by the indiscriminate disposal of infectious
medical waste in municipal landfills, or by dumping at
sea. A major environmental danger concerns many
substandard medical waste incinerators operated at
hospitals across the United States. Usually concentrated
in populous urban areas, these facilities each year emit
tons of toxins into the atmosphere, including dioxins,
furans, heavy metals, and acid gases. The current state
of medical waste disposal in the United States is
chronicled by Hershkowitz, "Without a Trace: Handling
Medical Waste Safely", MIT Technoloav Review,
August/September 1990, incorporated herein by reference.

Under current U.S. Environmental Protection Agency
(EPA) regulations, medical waste must be both treated to
substantially remove or reduce any biological hazard, and
destroyed so that it is no longer generally recognizable
as medical waste. After the waste has been treated and
destroyed in this way, the EPA does not require it to be
tracked and it may be disposed of in the same manner as
ordinary municipal solid waste.

Summarv of the Invention
In general, in one aspect, this invention features
a method for disposing of infectious medical waste in a
closed system where the steps of the method include
reducing the size of the waste to small particles in the closed system under negative pressure and indirectly heating the waste particles in the closed system by contacting the waste particles with an indirectly heated surface. The indirect heating is to a sufficiently high temperature and for a sufficient period of time to produce a quantitative assurance of sterilization of the waste particles. The indirect heating step includes transporting the waste particles along an indirect heating conveyor. Also, air may be continuously drawn through the closed system to control the pressure and moisture in the closed system.

In general, the method does not require the addition of a substantial amount of any liquid as the waste generally has moisture content from five to fifty percent by weight.

Preferably, the indirect heating conveyor is adapted to rotate and includes hollow portions and outer surfaces for contacting the particles, the hollow portions containing a heat conducting medium which heats the outer surfaces. The particles in contact with the surfaces are heated.

More preferably, the indirect heating step utilizes a pair of hollow screw conveyors which are interleaved or counter-rotatable or utilizes one or more hollow, rotating, pitched blade conveyors.

In a further aspect, the method comprises reducing the size of the waste into particles with no dimension greater than approximately three inches and indirectly heating the waste particles to at least 212 degrees
Fahrenheit.

In a further embodiment, the indirect heating medium comprises heated oil, a heated gas, steam, saturated steam or superheated steam.

In still another embodiment, the method includes the step of filtering the continuously drawn air before it is discharged into the atmosphere. Also, the filtering step includes filtering with either an activated carbon filter to remove volatile organics from the air; or a high efficiency particulate air (HEPA) filter to remove submicron particles and volatile organics, including bacteria, which may be emitted during the size reduction stage, from the air; or both.

Brief Description of the Drawinas
FIGS. 1(a) and l(b) are schematic diagrams of embodiments of a closed system and a process for the environmentally safe disposal of infectious medical waste;
FIG. 2 is a residence time/exposure temperature chart;
FIG. 3 is a plan view of a facility for receiving large amounts of medical waste and for processing the waste by using the closed system of FIGS. 1(a) and l(b); and
FIGS. 4(a) and 4(b) are perspective views of an embodiment of a portion of the closed system of FIGS.

1(a) and l(b).

Description of the Preferred Embodiments
Referring to FIGS. 1(a) and l(b), an embodiment of a closed system 10 for the environmentally safe disposal of infectious medical waste includes an infeed conveyor 12, an infeed chamber 14, a waste size reducing section 16, a rotary air lock 18, an enclosed hopper 20, a disinfection system 22, a hold-up and disengagement chamber 24, another rotary air lock 26, a dual filtration system 28, 30, and a fan 32.

Whether more than one piece of size reducing equipment are used depends on the state in which the system is operating. Certain states require that one not be able to recognize the medical waste. This is often a subjective determination, and may require that the waste particles be as small as less than one-fourth inch. In a state in which regulations are not as stringent, only one piece of size reducing equipment might be necessary.

First and, if necessary, second, stage waste size reducers for "destroying" the waste are contained in infeed chamber 14 and waste size reducing section 16, respectively. Suitable waste size reducers include low speed shear shredders such as those commercially available from Shredding Systems, Inc. (Wilsonville,
Oregon) and Shred Pax Corp. (Wooddale, Illinois).

Disinfection system 22 contains one to four rotatable hollow conveyors. A source of heat (preferably steam or hot oil) is passed through the hollow portion of the conveyors to indirectly heat and thereby "treat" the size-reduced waste passing over the conveyors. Suitable indirect-heat-exchanging hollow conveyors include the (preferred) commercially-available screw type Holo-Flites
Processor from Denver Equipment Co. (Colorado Springs,
CO) and the commercially-available pitched blade type
Porcupine Processor from Bethlehem Corp.

The dual filtration system consists of an activated carbon filter 28 for removing any volatile organics in the air followed by a high efficiency particulate air (HEPA) filter 30 for removing any submicron particles, including bacteria discharged from the waste size reduction area, from the air. One or both of filters 28, 30 can be used. Suitable activated carbon and HEPA filters are available from the Cambridge Filter
Corp. (Syracuse, NY). Air lock 18 prevents water vapor and air from traveling back through the system and out of infeed chamber 14. Similarly, air lock 26 prevents air or water vapor in the system from escaping. Air locks 18, 26 are both gas-solid separating devices that act as pressure seals; the air locks allow waste to pass but they do not allow air or water vapor to pass.

Closed system 10 is capable of processing (i.e., destroying and treating) from 100 to 6,000 pounds of waste per hour. During normal operation, closed system 10 usually will be required to treat and destroy from 2,000 to 2,500 pounds of waste per hour. The actual speed of operation of the closed system is determined, in part, by the composition of the waste. The amount of heat input required in closed system 10 per pound of waste processed ranges from approximately 100 to 400 btu, depending on the moisture content of the waste. Closed system 10 is made from rugged industrial grade equipment and therefore it can operate approximately 8,000 hours per year when properly maintained.

The meaning of "treatment" and "destruction" of medical waste, as used previously and throughout this specification, is taken from Environmental Protection
Agency (EPA), Office of Solid State Waste, Standards for the Tracking and Management of Medical Waste (ref: 40
C.F.R. µ 259). Specifically, "treatment" is defined as a process by which the concentration of microorganisms capable of causing disease in humans is reduced so as to render the waste noninfectious or less infectious (but not necessarily absolutely sterile) and thus, it is safe to handle, transport, and dispose of the waste.

"Destruction" is defined as ruining, tearing apart, or mutilating the waste so that it is no longer recognizable as medical waste.

While it is not necessary to achieve absolute sterility to comply with the EPA standards just mentioned, it is helpful to provide an accepted definition of sterility. Such a definition is provided by Favero and Bond, "Sterilization, Disinfection, and
Antisepsis in the Hospital", Chapter 24, p. 185, Manual of Clinical Microbiolosv: Fifth Edition, American Society for Microbiology, Washington, D.C., incorporated herein by reference. Favero and Bond define sterilization as the state in which the probability of any one of a high number (e.g., 106 to 107) of dried bacterial endospores surviving is 10-6 or lower. This definition goes far beyond what is necessary to provide a quantitative assurance of sterilization.

Still referring to FIGS. 1(a) and l(b), "red bag" waste (i.e., infectious waste from hospitals, medical laboratories, doctors' offices, and other sources) is placed on infeed conveyor 12 and enters infeed chamber 14 of closed system 10. The red bag waste can be either boxed or bagged. Infeed conveyor 12 can be operated continuously to provide a steady stream of waste to infeed chamber 14. Upon entering infeed chamber 14, the waste encounters one or more pieces of size reducing equipment that are in series. The waste size reducing system must be designed so that the majority of the material leaving that system is reduced to a particle size of less than three inches in at least two dimensions.

The small particles of waste then pass through rotary air lock 18 (i.e., a pressure seal) to enclosed hopper 20 which feeds into disinfection system 22. The small particles of waste are transported from an inlet end 82 of disinfection system 22 to an outlet end 84 by the two indirect-heat-exchanging rotatable hollow conveyors. Steam, supplied by a steam generator 86, is circulated within each of the hollow conveyors and the waste particles are thereby indirectly heated as they are transported from end 82 to end 84. That is, the waste particles are not directly heated by the steam itself but by the transfer of heat from the inside of the conveyors to the outside surface that contacts and transports the waste particles. The waste particles do not become "soaked" by the steam within the hollow conveyor because they contact only the outside heated surface of the hollow conveyor.

However, the moisture within the waste is heated to the boiling point, forming a steam blanket which provides an additional means of disinfection and stabilization of temperatures within disinfection system 22.

It has been shown by Rutala et al., "Decontamination of Laboratory Microbiological Waste by
Steam Sterilization", Applied and Environmental
Microbiologv, June 1982, pp. 1311-1316, incorporated herein by reference, that it is more effective to process smaller batches of waste than larger batches. Also, reducing the waste to small particles increases the surface area of the waste and allows maximum transfer of heat to the waste.

The waste particles in disinfection system 22 will typically be heated to a temperature in the range 212 to 300 degrees Fahrenheit, with 250 degrees Fahrenheit being preferred. The heating medium (oil or steam) circulated through the hollow conveyors is typically in the range of 212 to 400 degrees Fahrenheit, with 310 to 390 degrees
Fahrenheit being preferred. The total transit time for the particles to go from end 82 to end 84 of disinfection system 22 (i.e., the residence time of a waste particle in disinfection system 22) can range from only a few minutes to several hours, with the range of ten minutes to one hour being typical, and twenty minutes to one hour being preferred.

The interrelationship between the residence time and temperature is shown in FIG. 2. Referring to FIG. 2, a time/temperature chart indicates the necessary temperatures and associated residence times to achieve sterilization, as defined by Favero and Bond. For instance, a waste particle must remain in disinfection system 22 of FIG. 1(a) for three minutes if the temperature in the disinfection system is 270 degrees
Fahrenheit. At this particular temperature, a residence time of less than three minutes will not result in adequate sterilization as defined by Favero and Bond.

A computer control system (not shown), for controlling all aspects of the operation of closed system 10, controls the residence time and the temperature. The computer control system controls the residence time by causing the size reducing equipment to slow down or speed up their rate of operation. Again, the time/temperature chart of FIG. 2 indicates the required residence times for several selected temperatures.

Referring back to FIG. l(a), air is continuously drawn through the system by fan 32. The continuous action of fan 32 serves to reduce the pressure in closed system 10 (i.e., create negative pressure), direct any airborne contaminants in closed system 10 to filters 28, 30, and prevent any emissions from escaping closed system 10 and entering the facility or room in which closed system 10 is located. The continuously moving air keeps the pressure in closed system 10 at near atmospheric pressure, and therefore disinfection system 22 need not be a pressure vessel. The operational pressure range for disinfection system 22 is approximately 10 to 20 psia.

This relatively low operational pressure range allows a relatively inexpensive disinfection system 22 to be used, and therefore results in a less costly overall closed system 10, as compared to what the cost would be if a pressure vessel were required.

The continuously drawn air also withdraws any vaporized moisture coming off of the waste particles as they are heated and keeps the moisture in closed system 10 below the dew point to prevent condensate from forming in closed system 10. Vaporized moisture is created during the indirect heating of the waste because the waste typically has an inherent moisture content of anywhere from zero to fifty percent. The continuous action of fan 32 draws air over the waste to help remove this vaporized moisture. As shown in FIG. l(a), fan 32 draws air from waste size reducing section 16 (line 88), hold-up and disengagement chamber 24 (line 90), and disinfection system 22 (line 96) into dual filtration system 28, 30. The filtered air exiting fan 32, and therefore closed system 10, is an environmentally clean discharge.

Referring to Fig. l(b), disinfection system 22 can operate as a sealed pressure vessel at 5 to 30 psia, so that no air can leak in. When the temperature of the medical waste reaches 212 degrees Fahrenheit, steam is generated in disinfection system 22. To keep the pressure in disinfection system 22 from getting too high, the steam is condensed by running cooling water through a condensor 100. The pressure maintained in disinfection system 22 depends on the temperature of the cooling water in condensor 100. Inert gas (primarily air) which does not condense in condensor 100 is released through a back pressure control valve 102 and vented to the atmosphere or sent to mix with stream 88. The condensed water, which is environmentally clean, is discharged to a sewer.

If disinfection system 22 is run under negative pressure (below atmospheric pressure), sweep air will leak into disinfection system 22. In this case the pressure is controlled by controlling the temperature of the cooling water in condensor 100 and controlling the amount of sweep air allowed into disinfection system 22.

The advantage of running disinfection system 22 as a pressure vessel is that the system can run at below six to eight percent oxygen, thereby preventing fires and explosions.

The computer control system (not shown) mentioned previously also controls the air flow such that a desired closed system pressure and waste material moisture content are maintained, and such that moisture in closed system 10 is kept below the dew point to prevent condensate from forming in closed system 10. Typically, the computer control system acts to keep the moisture content of the waste material below five percent during processing.

The processed (i.e., destroyed and treated) waste that exits disinfection system 22 at outlet end 84 is dropped into hold-up and disengagement chamber 24. It then passes through air lock 26 and is deposited into a compactor/trailer system 92 for easy hauling to a landfill or a "waste-to-energy" facility.

Compactor/trailer system 92 is capable of compacting the processed waste to reduce its volume.

A system shutdown (for whatever reason) results in steam being injected, by emergency steam injectors 94, directly onto any waste contained in disinfection system 22, infeed chamber 14 and waste size reducing section 16.

In a shutdown, any waste left in closed system 10 has probably not been adequately processed (i.e., destroyed and treated), and therefore it is necessary to somehow disinfect it before any maintenance work is attempted.

Steam generator 86 provides the "emergency steam" necessary to achieve the disinfection. The steam is applied for a sufficient period of time, usually approximately one to two hours, such that the infectious waste left in closed system 10 is properly disinfected.

Also, a pressure sufficient to prevent condensate from forming is maintained in closed system 10 during this period of time. The steam then condenses, is drained off, and discharged into the sewer, possibly along with chemical treatment using chlorine, bleach, or hypochlorite solution to ensure the discharge is disinfected. Closed system 10 may now be safely dismantled and the waste removed. If repairs do not require dismantling of closed system 10, closed system 10 may be simply restarted without removing the enclosed waste. In this latter case, the waste will just continue through closed system 10.

The computer control system (not shown) controls the start-up and shutdown of the entire system as well as the infeed conveyor rate, steam temperature, waste temperature, flow of air, size reduction equipment rate, hollow conveyor rate, pressure in the closed system, etc.

However, manual overrides for all settings are also provided.

An obvious advantage of a closed system as just described is that it satisfies the EPA requirements of treatment and destruction of infectious medical waste.

Other advantages of a closed system include its ability to achieve high levels of disinfection (i.e., its ability to achieve sterilization as defined by Favero and Bond) and its ability to maximize heat transfer to the waste by increasing the surface area of the waste that is exposed to the indirect heat transfer surface (i.e., by reducing the size of the waste into small particles). Still other advantages include the low cost of operation that results from the continuous processing of the waste and the relatively low amount of energy required to process each pound of waste. The relatively high temperatures achievable by the closed system are another advantage.

Also, the closed system does not create the extremely foul odors that normally result in systems that rely solely on the direct application of steam (or a chemical) to the medical waste. Furthermore, little or no potentially environmentally harmful effluent is discharged into either the atmosphere or the public sewer in normal operation.

Referring to FIG. 3, a facility 34, housed in a building 36, that'receives large amounts of medical waste, may use one or more of closed system 10 (FIGS.

1(a) and l(b)) for processing the waste. Infectious or red bag waste is collected and transported to facility 34 via an integrated transportation system built around a standard sealable container 38 (e.g., a box, drum, or barrel.) Each sealed container 38 typically contains between fifteen and thirty pounds of red bag waste and can be easily handled by workers at both ends of the journey. Containers 38 are sealed at the source and transported in trucks 40 used solely for this purpose.

The waste in each container 38 is traced with an automated manifest system so that waste generator facilities will have a continuous record of the safe disposal of each load sent to facility 34.

Receiving systems 42 in the front end of facility 34 are designed for receiving and unloading containers 38. Typically, facility 34 has the capacity to process from twenty-four to 100 tons of medical waste per day (TPD), the equivalent of approximately five to seven delivery trucks 40 containing sealed containers 38 of medical waste. Delivery trucks 40 drive through doors 44 into building 36 where containers 38 are unloaded from trucks 40 and sent to a holding area 46. Even though the red bag waste contained in containers 38 is sealed in bags or boxes designed specifically for medical waste, containers 38 are cleaned after usage, as a precautionary measure, in a container sterilizing area 48.

Cleaned and sterilized containers 38 are reloaded on delivery trucks 40 and returned to the waste generation facilities where they are reloaded with red bag medical waste requiring disposal.

A waste destruction and treatment portion 50 of facility 34 may include one or more of closed systems 52 (similar to closed system 10 of FIGS. 1(a) and l(b).)
Still referring to FIG. 3, sealed containers 38 of medical waste are brought one by one to closed systems 52. Typically, waste destruction and treatment portion 50 of facility 34 operates for a sufficient number of hours each day such that all received red bag medical waste is treated and destroyed within twenty-four hours of being received.

Each container 38 is unsealed, lifted, and emptied onto infeed conveyor 12 of closed system 10 by a lifting mechanism (not shown) which attaches to container 38.

Empty containers 38 are conveyed to container cleaning and sterilizing area 48 and then into inventory, ready to be sent out again.

A particular embodiment of a portion of closed system 10 of FIGS. 1(a) and l(b) is shown in FIGs. 4(a) and 4(b), where FIG. 4(b) shows outer surfaces in phantom. In this embodiment, red bag medical waste 54 enters a hopper 56 and a surge feed hopper door 58, preferably operated by a hydraulic lift. Feed hopper door 58 seals hopper 56 once waste 54 has been fed into it. Hopper 56, which is kept under negative pressure to prevent fugitive emissions by use of an induced draft fan, feeds a size reducing assembly 60 which destroys red bag medical waste 54 by reducing it to granules having a maximum dimension of three inches. A pneumatic or hydraulic ram 62 operates to help force waste 54 through size reducing assembly 60.

A hopper/size reducing assembly and ram of the type described is commercially available as Model No. 1000-E from Shredding Systems,
Inc., the specification of which is incorporated herein by reference. Similar equipment is also commercially available from Shred Pax Corp.

The output stream of size reducing assembly 60 consists of granulated waste which passes into a surge hopper 64 which feeds an input end 66 of a sealed disinfection processor 68, such as that manufactured by
Denver Equipment Company. Disinfection processor 68 includes a sealed trough 70 containing two rotatable hollow conveyors 72 which transport the granulated waste from input end 66 of disinfection processor 68 to output end 74. Oil or steam 98 is circulated within each of hollow conveyors 72 to indirectly heat, and thereby treat, the granulated waste as it travels the length of disinfection trough 70. A hollow screw-type processor is commercially available as Holo-Flites Processor No.

1D2424-6 from Denver Equipment Company, the specification of which is incorporated herein by reference.

Functionally similar pieces of equipment, such as pitched blade conveyors, are also commercially available from
Bethlehem Corp.

As described previously, a system shutdown would result in steam being injected directly into both trough 70 of sealed disinfection processor 68 (i.e., the volume surrounding hollow conveyors 72) and hopper 56, in order to treat any infectious waste left in the system during the shutdown. In the case of a shutdown, the pressure and temperature inside trough 70 are controlled and maintained for a sufficient period of time (approximately one to two hours) such that condensate is prevented from being formed and the infectious waste left in the system is properly disinfected. The steam is then allowed to condense, drained off, and discharged into the sewer, possibly along with chemicals to ensure the discharge is disinfected. If the system needs to be dismantled to be repaired, the waste left in the system can now be removed safely.

Alternatively, if repairs do not require dismantling of the system, the system may be simply restarted after repairs are made.

Disinfection processor 68 discharges the treated and destroyed granulated waste into a discharge surge hopper 76 which directs the waste to a discharge conveyor 78, which then discharges the waste through an outlet 80.

Other embodiments are within the following claims.

For example, hot gas or hot oil may be circulated through hollow conveyors 72 instead of steam. Also, other types of indirect-heat-exchangers in addition to the hollow conveyors could be used.

Adequate destruction of the waste could be achieved by many types of waste size reducing machines, such as shredders, hammer mills, pulverizers, grinders, and other types of equipment. Moreover, any number and combination of these types of equipment could be used.

Infeed conveyor 12 (FIGS. 1(a) and l(b)) can include a continuous weighing system.

An ordinary dumpster or any other collection means can be used instead of compactor/trailer system 92 (FIGS.

1(a) and l(b)). Also, the processed waste exiting from closed system 10 could be input directly into a "wasteto-energy" facility as fuel.

Instead of injecting steam into closed system 10 upon a system shutdown, bleach, chlorine, or hypochlorite solution could be injected to disinfect any waste left in the system.

Closed system 10 may be configured as a selfcontained mobile disinfection unit, or as an integrated unit which is part of a medical facility that produces red bag waste, or a regional collection center that collects red bag waste from various sources.

Claims

1. A method for disposing of infectious medical waste in a closed system, comprising the steps of reducing the size of said waste in said closed system to smaller particles; and indirectly heating said waste particles in said closed system by contacting said waste particles with a heated surface, said indirect heating being to a sufficiently high temperature and for a sufficient period of time to produce a quantitative assurance of sterilization of said waste particles, said indirect heating step comprising transporting said waste particles along an indirect heating conveyor; wherein said indirect heating conveyor is adapted to rotate and comprises hollow portions and outer surfaces for contacting said particles, said hollow portions containing an indirect heating medium which heats said outer surfaces, whereby said particles in contact with said surfaces are heated.

2. The method of claim 1 wherein air is continuously drawn through said closed system to control the pressure and moisture in said closed system.

3. The method of claim 1, wherein said size reducing step comprises the use of one or more shredders, hammer mills, pulverizers or grinders, or any combination thereof.

4. The method of claim 1 wherein said size reducing step comprises reducing said waste into particles with no more than two dimensions greater than approximately three inches.

5. The method of claim 1 wherein said indirect heating step comprises indirectly heating said waste particles to at least 212 degrees Fahrenheit.

6. The method of claim 2 wherein said indirect heating medium comprises heated oil.

7. The method of claim 2 wherein said indirect heating medium comprises a heated gas.

8. The method of claim 2 wherein said indirect heating medium comprises steam.

9. The method of claim 8 wherein said steam is superheated.

10. The method of claim 8 wherein said steam is saturated.

11. The method of claim 1 further comprising the step of filtering said continuously drawn air before it is discharged into the atmosphere.

12. The method of claim 11 wherein said filtering step comprises filtering with either an activated carbon filter to remove volatile organics from the air, or a high efficiency particulate air (HEPA) filter to remove submicron particles and volatile organics, including bacteria, from the air, or both.

13. A closed system for disposing of infectious medical waste, comprising means for reducing the size of said waste in said closed system to smaller particles; and a disinfection unit, connected to said means for reducing the size of said waste via a gas-solid separator mechanism, for disinfecting said size reduced waste by indirectly heating said waste particles, said disinfection unit comprising a heated surface capable of indirectly heating said waste particles contacting said surface to a sufficiently high temperature and for a sufficient period of time to produce a quantitative assurance of sterilization of said waste particles, said disinfection unit further comprising transporting said waste particles along an indirect heating conveyor;

; wherein said indirect heating conveyor is adapted to rotate and comprises hollow portions and outer surfaces for contacting said particles, said hollow portions containing a heat conducting medium which heats said outer surfaces, whereby said particles in contact with said surfaces are heated.

14. The system of claim 13 wherein air is continuously drawn through said closed system to control the pressure and moisture in said closed system.

15. The closed system of claim 13, wherein said means for reducing the size of said waste comprises the use of one or more shredders, hammer mills, pulverizers or grinders, or any combination thereof.

16. The closed system of claim 13 wherein said means for reducing the size of said waste produces particles with no more than two dimensions greater than approximately three inches.

17. The closed system of claim 13 further comprising a filtration unit for filtering said continuously drawn air before it is discharged into the atmosphere.

18. The closed system of claim 17 wherein said filtration unit comprises either an activated carbon filter for removing volatile organics in the air; or a high efficiency particulate air (HEPA) filter for removing submicron particles and volatile organics, including bacteria, in the air; or both.

19. The system of claim 13 wherein said disinfectin unit comprises onr or more hollow, rotating, pitched blade conveyors.