Patent Publication Number: US-2011048086-A1

Title: Method for chemically reducing waste materials

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/341,375 filed Dec. 22, 2008, which is a divisional of U.S. patent application Ser. No. 11/096,330 filed Apr. 2, 2005, which is a continuation of PCT patent application no. PCT/US2003/031184, filed Oct. 1, 2003 which claims priority to U.S. patent application Ser. No. 10/263,043, filed Oct. 2, 2002. This application is also related to U.S. patent application Ser. No. 09/171,447, filed Oct. 20, 1998, titled “Methods for Treatment and Disposal of Regulated Medical Waste,” and U.S. Pat. No. 6,437,211, issued Aug. 20, 2002, both of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     This invention relates to the field of waste disposal and, more particularly, to a system and method for the digestion and sanitary disposal of waste material, such as infectious waste material and other hazardous, biohazardous, or radioactive waste. 
     BACKGROUND 
     Many facilities, such as hospitals, various health-care facilities, research and teaching institutions, food preparation facilities, and the like, produce considerable amounts of infectious, biohazardous, or radioactive waste. Such waste may include surgical and pathological tissues, animal tissues, cadavers, blood and other bodily fluids, disposable matter exposed to blood, and other potentially infectious or dangerous body fluids of patients or animals. Such waste is classified in the United States as “regulated medical waste” (RMW) under state regulations, and must be disposed of in strict compliance with the applicable governmental regulations. 
     Health-related organizations and governmental regulatory agencies have become increasingly concerned with the adequacy of existing cleaning and disposal methods. It has been discovered that some potentially biohazardous agents, such as prokaryotes, or infective proteins (prions) do in fact survive standard autoclaving procedures. Thus, more effective sterilization techniques have been sought for treating solid infectious biomedical waste and aqueous solutions containing such waste. 
     In addition, universities and other research facilities likewise produce significant amounts of such waste. For example, in conducting experiments in cell lines, tissues, or animals, it is common to introduce dyes, toxic chemicals, or infectious agents into the test subject. Moreover, radioactive materials are also commonly used as a tool to enhance chemical, biochemical, pharmaceutical, biomedical, and biological research. It is common to label drugs or chemical compounds with radioisotopes in order to study efficiently and accurately where these compounds are metabolized and incorporated within the body. After completion of the test and analysis, due to the introduction of infectious agents or hazardous or radioactive material into the tissue, the remaining tissue or animal carcass may fall under the classification of “regulated medical waste,” hazardous waste, or low-level radioactive waste (“LLRW”). In addition, animal waste, animal bedding, handling materials, and other matter exposed to any animal body fluids or excretions may also need to be treated as infectious or hazardous waste material, thus requiring disposal in accordance with the applicable governmental regulations. 
     Moreover, it is common today for health care organizations to clean material, instruments or surface areas exposed to infectious agents, including zoonotic agents, with disinfectants such as formaldehyde or glutaraldehyde. Spent cleaning solution is considered hazardous liquid waste and must also be disposed of in compliance with governmental regulations. The cost of disposing of such waste, on an institutional basis, can be quite high. Further, formaldehyde, glutaradehyde, phenols and like materials, are commonly used for embalming tissues and in fixation of infectious biological materials. Thus, these tissues and the fixative agents may also have to be disposed of as “regulated medical waste,” hazardous waste, or mixed waste in compliance with the applicable governmental regulations. 
     Further, animal carcasses containing compounds labeled with .sup.14C or .sup.3H or other radioisotopes are classified as LLRW. Because state and federal guidelines regulate the disposal of LLRW, special precautions must be followed in their disposal. Currently, the two methods commonly used in disposing of this type of waste are incineration and land burial. Presently, federal law allows for incineration only when the animal carcass contains a radioisotope concentration below a certain level. However, even when radioisotope concentrations are below this level, incineration may be further limited by state and local agencies. When the levels of radioactivity in the animal carcasses are below acceptable de minimis levels as defined by federal, state, and local authorities, the disposal thereof is not subject to any additional regulation as a radioactive waste. However, to further complicate matters, the incineration of radioactive animal carcasses at any level is prohibited in certain major metropolitan areas. Nonetheless, the general process of incineration itself, even when no radioactive materials are involved, is subject to additional regulations, such as those requiring licensing from a state or local environmental agency. Additionally, future increases in the requirements for incinerator designs and function under clean air regulations put in doubt the continued availability of incineration as a practical method for disposing of animal carcasses classified as LLRW or for any non-radioactive carcasses or human pathological waste. 
     Presently, the only real alternative to incineration for radioactive animal carcasses is burying the carcasses in a licensed LLRW disposal facility. This method entails the packing of the entire carcasses in lime and adsorbents, repacking them in special drums and shipping the drums to a LLRW site. Currently there are only two such sites in the United States, located at Hanford, Wash., and Barnwell, S.C. Due to the limited number of land burial sites currently operating in the United States, it is extremely costly to dispose of any radioactive waste by this method; it is disproportionately costly for animal carcasses containing low level radioactive waste due to the size and weight of the carcass. Due to the extremely high cost associated with land burial and the limitations on access to current sites, the feasibility of land burial as a method of disposing of animal carcasses classified as LLRW remains in doubt. 
     It is known in the art that low levels of certain radioactive waste may be disposed of to a sanitary sewer under federal regulations with appropriate record keeping and/or monitoring. This includes isotopes in aqueous solution at levels below the maximum permissible concentration (MPC) as defined by 10 C.F.R. 20 and radioisotopes in human waste. Such a procedure has been utilized, for example, in the disposal of radioactive waste generated by many patients undergoing treatments for cancer. Today, a common method of treating cancer is by radiation therapy, which often involves the absorption of radioactive compounds. Many of these radioactive compounds eventually leave the body through fecal and urinary excretions. These excretions will contain small amounts of radioactive material. However, this radioactive material is disposed of through the general sewage system because the level of the radioactive materials discharged by the body into the sewer system is sufficiently diluted such that it no longer poses any hazard to public health and safety. This process is well within the state and federal disposal regulations for LLRW disposal. However, LLRW contained in animal remains are not readily capable of disposal through such means because the animals are naturally solid waste. 
     It is also known in the art that substances containing keratin, such as hair and nails, may be dissolved by means of acid or alkaline hydrolysis, as disclosed in U.S. Pat. No. 1,974,554 issued to Ziegler. It is further known that hydrolysis of proteins containing keratin may be carried out with alkaline solvents. It is even further disclosed in U.S. Pat. No. 5,332,532 to Drs. Kaye and Weber, which patent is commonly owned by the assignee of the present application, that such hydrolysis may be utilized on proteins contaminated with radioactive materials. 
     Of the known methods of disposing of infectious, biohazardous, or low-level radioactive waste, each faces an indeterminable future under the ever-changing breadth of the environmental laws. Furthermore, each is extremely costly, putting an unneeded drain on already strained research and waste management budgets of hospitals, universities and other institutions. Thus, a need persists for means of safely and inexpensively treating and disposing of organic waste matter. The present invention addresses this need. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a system for degrading, digesting or neutralizing undesirable materials by subjecting them to a controlled alkaline hydrolysis cycle. In one form, the system includes an apparatus having means for receiving the undesirable materials, such as a closeable reaction vessel. The apparatus further includes means for controlling the operation of the system. The apparatus also includes means for introducing water within the interior of the vessel in a predetermined amount based on the maximum volume of the vessel and means for introducing an alkali compound within the interior of said vessel in predetermined amount based on the maximum volume of the vessel. Additionally, the apparatus includes means for heating the interior of the vessel to a first predetermined temperature level after the introduction of water and alkali compound into the interior of the vessel for a duration sufficient to produce a safely disposable resultant. 
     The method provided by the invention generally comprises the steps of providing a sealable vessel, filling the vessel with a highly alkaline solvent, immersing the waste matter containing the undesirable elements within the highly alkaline solvent, and heating the highly alkaline solvent. The waste matter is allowed to remain within the highly alkaline solvent until the hydrolyzable matter is degraded or digested (i.e., substantially hydrolyzed), thereby forming a sterile solution and sterile solid waste. The aqueous solution and any resultant solid waste may then be disposed of through conventional means, such as a sanitary sewer, anaerobic fermentor, local landfill facility, or, if appropriate, by land application as fertilizer (either in liquid or solid form) or by mixing with peat, compost, or other cellulosic material. 
     One object of the present invention is to provide an improved system, method and apparatus for disposing of hydrolyzable waste matter. Related objects and advantages of the present invention will be apparent from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of the system provided by a currently preferred embodiment of the invention; 
         FIG. 2  is a flowchart representation of the method provided by a currently preferred embodiment of the invention; 
         FIGS. 3A ,  3 B and  3 C are side, top and bottom elevations, respectively, of a holding container according to a first embodiment of the present invention for receiving and storing the waste matter within the vessel chamber interior during the digestion cycle; 
         FIG. 4A  shows an exploded elevation of a unique vacuum balancer device provided by the invention; 
         FIGS. 4B and 4C  show the vacuum balancer of  FIG. 4A  in its open and closed states, respectively; 
         FIGS. 5A-5D  show various views of agitating injector means provided by this invention; 
         FIGS. 6A-6C  are top, front and side elevations, respectively, of a vessel chamber according to a second embodiment of the present invention for receiving and storing waste matter therewithin during a hydrolytic digestion cycle; 
         FIG. 6D  shows an exploded perspective view of the embodiment of  FIGS. 6A-6C ; 
         FIG. 6E  is a plumbing schematic of the embodiment of  FIGS. 6A-6C ; 
         FIG. 7A-7C  are top, side and end elevations, respectively, of a vessel chamber according to a third embodiment of the present invention. 
         FIG. 7D  is a plumbing/electrical schematic of the embodiment of  FIGS. 7A-7C . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This invention involves a system and method for treating and safely disposing of waste matter containing undesirable agents or elements, such as but not limited to animal carcasses, animal tissue, organic material, organophosphate pesticides and nerve gasses, nitric esters and aromatic nitro-compounds, chemotherapeutic agents and related alkylating agents (such as sulfur mustards, nitrogen mustards, and phosgene), antibiotics, plant, animal, and bacteriological toxins, non-protein toxins (such as aflatoxin and tetrodotoxin), animal venoms (such as snake, spider, scorpion, fish and amphibian venoms), plant catechols, polyphenols, infectious, biohazardous, hazardous, and radioactive materials. The system and method of this invention is designed and intended to comply with all federal, state, and local laws or regulations presently in existence applicable to the disposal of such waste. 
     The method of the invention comprises the steps of providing a sealable vessel, providing a highly alkaline solvent, immersing the waste matter containing the undesirable elements within the solvent within the interior of the vessel, heating the solvent and the waste matter, and allowing the waste matter to remain within the solvent until digested or degraded, thereby forming a sterile aqueous solution and sterile solid waste. The extent of digestion or degradation of the waste matter may be increased by treating the waste under pressures above one atmosphere, by adding catalytic agents to the solvent bath, or both. After cooling, the post-digestion end product may then be directly disposed of through conventional disposal means, such as a sanitary sewer or landfill, or even used as a fertilizing agent in land use applications. If preferred, the post-digestion stage may also include rinsing or flushing of the resultant waste product and the interior of the vessel. The system and method of this invention also substantially reduce the amount of post-digestion solid waste to be disposed of. 
     The inventors herein have determined that completeness of degradation/digestion (time vs. temperature curves) may be determined by measuring the rate of production of amino acids as the digestion process proceeds. When that process reaches an asymptote, digestion is considered complete. 
     In operation, when the operator is ready to dispose of the waste matter, such as animal carcasses or remains, for example, the waste matter is placed within a holding container that is then placed within the interior of the vessel. The lid of the vessel is then secured by way of conventional lid clamps. The load of waste matter placed in the vessel for digestion should be at least 10% of the capacity of the vessel (by weight) but not more than 60% of the total weight of the capacity of the vessel. The digestion cycle is then initiated, ultimately resulting in the waste matter being completely immersed in the highly basic solvent. 
     For the purposes of this application, a “highly alkaline solvent” or “highly basic solvent” may include a 1-2 molar (M) aqueous solution of an alkali metal hydroxide, an alkaline earth metal hydroxide or an alkaline earth metal oxide. Preferably, this solvent should have a pH of at least above 13, preferably in the range of 13 to 14. An aqueous solution of sodium hydroxide (NaOH—also commonly known as caustic soda or sodium hydrate) or potassium hydroxide (KOH—also commonly known as caustic potash or potassium hydrate) is preferred. While an aqueous solution of NaOH or KOH is preferred, solutions containing calcium oxide (CaO—also commonly known as burnt lime, calx or caustic lime), ammonium hydroxide (NH.sub.4OH—also commonly known as aqua ammonia) or magnesium hydroxide are also suitable for some applications. An example of a suitable highly basic solvent may consist of a 0.1 M to 2.5 M solution of NaOH in water, or approximately 0.4%-10% sodium hydroxide (by weight) in water. 
     During digestion, the hydrolyzable material should be immersed in a sufficient amount of solvent such that the material may be degraded or digested. One ratio assuring excess base to carry out the digestion of the waste matter to completion, particularly animal tissue, is a 1:10 ratio of alkali metal hydroxide to wet tissue weight. A further expression of this ratio is 40 kilograms of NaOH dissolved in 900 liters of water added to 100 kilograms dry weight protein or 40 kilograms of NaOH in 500 L H.sub.2O added to 500 kilograms fresh or frozen waste matter by weight. These ratios are given only as instruction as to how to conduct the method and operate the system stated herein and not to limit the nature or scope of the invention; one using the system and method described herein may find ratios more economical and exact as the invention is practiced. In order to assure degradation of all infectious wastes, including prokaryotes, the highly basic solvent should be heated to a temperature of at least about 90.degree. C., and preferably 110.degree. C. to 150.degree. C. 
     It is preferable to allow the reaction to proceed in a closed reaction vessel after the waste matter has been immersed within the solvent. Reducing the amount of CO.sub.2 available to the reaction is beneficial in order to maintain the ideal rate and stoichiometry of the reaction. This may be done by simply removing or limiting any contact that the highly basic solvent has with the environment. 
     In the event the reaction between the waste matter such as an animal carcass and the highly basic solvent were allowed to proceed at its natural rate, it may take an impractical amount of time. Therefore, it is advantageous to increase the reaction rate beyond its natural progression. One way to increase the speed of the reaction process is to heat the solvent, preferably to temperatures of 110.degree. C. to 150.degree. C. Conducting the reaction in a sealed vessel under increased atmospheric pressure also reduces the reaction time needed to digest the animal tissue. A preferred mode includes heating the solvent to a temperature of about 150.degree. C. for a duration of about three (3) hours at a pressure of about 55 PSIG (or about 3.8 atmospheres). It has been found that the basic rule of thermodynamics or the “Q10 Rule” applies to this invention as well in that for every 10 degrees Celsius rise in temperature, the reaction rate for the chemical reaction taking place within the closed vessel increases two-fold, thereby resulting in the digestion time being reduced by approximately 50%. Such phenomenon is based on the Arrhenius equation. 
     Furthermore, detergents to a concentration of up to 1% to the solvent, examples being sodium lauryl sulfate or deoxycholate, may also be added to increase the rate of digestion, if desired. It should also be noted that addition of detergents to the solvent also has the added advantage of dispersing nonsaponifiable lipids, and aiding in the sterilization of biological materials. 
     Ultimately, the reaction rate will depend on specific variables such as: the temperature of the solvent, pressure in the reaction vessel, the nature and volume of the waste matter, i.e., the physical size of the carcasses or waste tissue, and the ratio of waste matter to the volume of the highly basic solvent. As the reaction rate will vary, the time that the waste matter must remain immersed in the solvent will also vary. However, regardless of the reaction rate, the waste matter should remain completely immersed within the solvent until solubilized and hydrolyzed. Allowing the waste matter to remain within the solvent until digestion is achieved will also help produce a more sterile solution. 
     Once the waste matter such as animal tissue has been digested, two types of solid debris often remain. The first type of debris consists of rubber, plastic, or cellulosic materials that a lab animal may have ingested, as well as debris remaining from experimental or surgical procedures, such as surgical clips, sutures, glass, and bits of plastic or paper. Solid items such as these never incorporate the radioactive isotopes. Once sterilized, such solid items are also not considered biomedical waste in most jurisdictions. This type of debris may often be simply disposed of as ordinary sterile solid waste upon being isolated from the solution and washed. 
     The second type of solid debris remaining undissolved includes inorganic portions of an animal&#39;s skeletal structure and teeth. Unless a radioisotope capable of incorporation into the inorganic portion of bones and teeth is used, the inorganic component of the skeletal remains will not contain the radioactive isotope and may be disposed of as solid sterile waste. The skeletal remains, when removed from the solvent and washed, are extremely friable. 
     After the biological waste matter has been digested within the solvent and the solid debris removed, the solution may comprise a diluted concentration of radioactive isotopes that meet the MPC requirements under the federal regulations, as well as an alkaline mixture of alkai metal salts of amino acids and peptides, sugar acids, nucleotides, small peptides, fatty acids from lipids, phosphates from lipid and nucleic acid breakdown, soluble calcium salts, pigments, sugars, sugar alcohols, hydrocarbons, and inorganic acids derived from the electrolytes normally within solution in body fluids. These by-products are identical to those released in vast amounts from cooking leftovers and waste from all commercial and household kitchens. Thus, the solution contains compounds that are non-toxic and are biodegradable by bacteria or fungi found in soil and sewage treatment systems, and possibly a very dilute amount of radioactive solute. 
     Because the solution at the end of the digestion cycle contains only non-toxic biodegradable materials and the water released from the animal tissue, further dilution of the solution may not be required for safe disposal. Further dilution to reduce the alkalinity of the solution will be accomplished, however, by the rinsing of the vessel and the inorganic remains with excess water, by the temperature regulating co-flush for the effluent, and the general daily effluent volume of the site, institution, or company. (Deliberate dilution of soluble radioactive waste is usually not permitted by the applicable local, state, federal and national regulations.) Further, carbon dioxide may be injected into the solution at this stage to adjust its pH down to between about 7.5 and 10. At this stage, however, the concentration of radioisotope in the solution should be well within the level that may be safely released to a sanitary sewer. 
     This sterile, neutral, aqueous solution that contains the breakdown products of cells and tissues, and may contain remnants of radioisotopically labeled solutes may be safely disposed of utilizing methods commonly used to dispose of everyday nontoxic and biodegradable substances. It is entirely safe to dispose of this solution using disposal means such as sanitary sewage systems and other disposal means appropriate for the disposal of these simple biodegradable compounds. 
     Now turning to  FIG. 1 , a preferred system  10  for carrying out the invention is shown schematically, comprising a closed reaction chamber or vessel  12  capable of containing the solvent solution and the waste matter such as the animal tissue or carcass or regulated medical waste. A portion of vessel  12  is defined by a double-walled structure for purposes discussed below. Naturally, the vessel must be constructed from material capable of withstanding the pH levels, temperatures, and pressures employed in this invention. Suitable materials include certain formulations of stainless steel. Vessel  12  must also be capable of being closed in an air tight fashion to provide the necessary environment within the vessel interior  14  for the controlled alkaline hydrolysis cycle to be carried out to completion. Thus, the lid or cover  16  of the vessel  12  must be capable of being closed tightly, pressure and air tight, to withstand the temperatures and pressures of the digestion cycle and prevent the inadvertent introduction of atmosphere (particularly carbon dioxide) into the vessel interior or, more importantly, prevent the escape or inadvertent exhausting of the contents of the vessel interior to atmosphere. Such closure of the vessel may be achieved by conventional lid clamps well known in the industry (not shown). 
     The system and method carried out by this invention are controlled by a conventional programmable logic controller (PLC) means (not shown) defined by a programmable multi-loop machine controller, computerized for automated operation. Such control means preferably includes an information screen, a disk drive for the automation program software, a disk drive or like recording means for recording process parameters and data during operation, and a keyboard for alternative manual input or operation. 
     System  10  further includes a weight transducer  18  (shown schematically) coupled to one or more of the legs of the vessel  12  for determining the weight of the waste matter received within the vessel and for generating an output signal indicating such weight data. The transducer is preset such that the weight of the vessel without contents equals zero weight. The contents weight data is then inputted to the PLC control means for, based on the weight output data, determining the appropriate amounts of water and solvent to introduce into the interior of the vessel, utilizing a water supply  20 , via conduit  20   a , and a spray ball or nozzle  20   e  located within the vessel interior, and solvent supply  22 , via solvent loop conduit  24  and pump  26 . Solvent is injected into the interior of vessel  12  via injector means  28 , which are shown schematically in  FIG. 1  and in more detail in  FIGS. 5A through 5D . Injector means  28  mixes and agitates the contents of the vessel interior  14  and enhances the interaction between the highly basic solvent and the waste matter being digested by directing the jet flow of the solvent solution upwardly at the bottom  62  of the container  60  (see  FIG. 5A ) to keep the vessel contents moving and to prevent waste matter from accumulating at the bottom of container  60  and not mixing thoroughly with the solvent. By doing so, the agitating injector means also shortens the digestion cycle time. 
     It should be appreciated that this invention is not limited to the agitating injector means described and shown herein but contemplates any means that introduces the solvent into the interior of the vessel. The mere introduction of solvent into the vessel will “mix” the alkali-water solution with the waste matter. Introducing heat also induces mixing. Moreover, agitation of the contents may be achieved by various means, including external mechanisms coupled to the vessel, such as a rocking or shaking assembly that physically moves the vessel. All such alternative means of mixing or agitating the vessel contents are contemplated by this invention. 
     As noted above, the preferred process requires that the solvent solution be heated in order to accelerate the digestion process to completely dissolve the animal tissue, carcasses, or medical waste. To that end, further included in system  10  is a heating means preferably defined by a stainless steel steam jacket  30  arranged circumferentially about the vertical sides and base of vessel  12  for heating the interior of the vessel to a first predetermined temperature level after the introduction of water and solvent into the vessel interior  14 . Heated water or steam is circulated between the walls of the double walled vessel  12 . While the steam jacket defines a preferred embodiment, any heating means commonly known and used for heating solutions could be utilized in this invention. Steam is supplied to jacket  30  by a steam supply  32  and conduit  32   a  provided with a cut-off valve  32   b  and a regulating valve  32   c . The system further includes a vent  34 , which is disposed in the open state upon initiation of the cycle and thereafter closed by PLC control means when the temperature within the vessel reaches a predetermined first temperature. The temperature within the vessel  12  is gauged by a vessel thermocouple  36   a , while the pressure within the vessel is gauged by a PSI transducer  38 . The temperature within the solvent loop is gauged by a loop thermocouple  36   b.    
     In the preferred embodiment, an eductor apparatus  40  is utilized for creating a vacuum within the vessel interior  14 . When vent  34  is open and flushing water is admitted to the eductor by the water supply  20  via conduit  20   b,  the action of the eductor draws the air and any odorous gas from within the interior of the vessel through conduit  34   a , whereupon the air and odorous gas is eventually entrapped with the flushing water at eductor  40  to, in turn, be removed from the system via drain conduit  42   a  to sanitary drain  42 . The temperature of the fluid at the drain may be gauged by a thermocouple  44  to monitor the effluent temperature prior to disposal in a sanitary sewer system. The vacuum-creating eductor substantially reduces the odorous gases that may escape from rotting carcasses while the vessel is filling, before the vent valve  34  is closed. 
     In cycle, once the contents of the vessel are drained after the digestion cycle (heating and cooling), the interior of the vessel is rinsed with cold water via sprayball  20   e  with the drain valve  41  open. After a few minutes, the drain valve  41  is closed to allow the vessel to begin to fill with water. Once the vessel is filled to the point where the waste matter is covered, the contents are then agitated by injecting the water solution through injector means  28  for a few minutes to increase the rinsing effect. Drain valve  41  is then re-opened and the liquid contents of the vessel are allowed to drain. Thereafter, if desired or necessary, the drain valve  41  is closed for a second time and the vessel is allowed to again fill with water. Heat may then be applied again to the vessel to heat the liquid within the vessel to approximately 95.degree. C. (203.degree. F.), whereupon an enhanced rinse is initiated. The time and temperature used in this post-digestion heating stage may vary. 
     To balance or control the vacuum being created within the vessel during the post-digestion cooling cycle and to prevent the vacuum from impeding the draining of the vessel, a vacuum balancing device  46  shown and discussed below in relation to  FIGS. 4A-4C  is provided that selectively admits ambient air to the vessel interior when the internal vacuum pressure reaches or exceeds the threshold pressure of the vacuum balancer  46 . While the vacuum balancer shown and discussed herein is of a unique design, any vacuum balancing device that will not leak fluid or collect condensed fluid may be suitable for the effective operation of this invention. 
     Referring now to  FIG. 4A , vacuum balancer  46  is shown in detail comprising a vacuum clamp  47 , a vacuum plug  48 , an annular end cap  49 , a vacuum gasket  50 , an O-ring  51 , a flat washer  52 , a socket head cap screw  53 , an upper ferrule portion  54 , a lower ferrule portion  55 , a spring  56  and a thermometer cap  57 . In its closed state as shown in  FIG. 4C , spring  56  urges the cap screw  53 , washer  52  and the vacuum plug  48  upwardly such that O-ring  51  abuttingly engages the vacuum gasket  50 , thereby preventing any air from passing therethrough. When the internal vacuum pressure within vessel  12  reaches a certain point, it will overcome the force of the spring  56 , thereby allowing the plug  48  to move downwardly causing O-ring  51  to disengage from the gasket  50 , as shown in  FIG. 4B , to admit ambient air into the vessel interior while the eductor  40  draws air out of the vessel interior. 
     The preferred system further includes a permeable container capable of holding the waste tissue or remains or medical waste within the vessel interior  14  during the digestion cycle to completely immerse the waste material within the solvent solution. As shown in  FIGS. 3A-3C , such a container preferably includes a cylindrical article  60  defined by a steel mesh screen  62  having an upper rim portion  64 , a lower rim portion  66 , and a lid  68  to enclose the waste tissue within the container  60 . (While the preferred shape of the container is cylindrical, other non-cylindrical shapes are suitable and should be considered as being within the scope of this invention.) Attached to the lid  68  is preferably a handle  68   a . As shown in  FIGS. 3B and 3C , both the lid  68  and the bottom of the container include the stainless steel mesh  62 , which is preferably constructed from stainless steel screen mesh having about 3 mm to about 6 mm (one-eighth (⅛) to one-quarter (¼) inch) screen mesh. The lid  68  may be releasably secured to the body  61  of the container via conventional means. Handle  68   a  may be equipped with an eyelet-like portion  68   b  to receive attachment means for lowering and raising the container into and out of the vessel interior. When the waste tissue is digested, the permeable container  60  may be hoisted out of the vessel  12 , or removed out of another port arranged in the side of the vessel  12  during a “clean side” removal as discussed below, thereby removing the undigested solid debris remaining within the container  60 . The height “h” ( FIG. 3A ) and diameter “d” ( FIG. 3C ) of the container may be varied to accommodate varying amounts of waste tissue or carcasses of animals of varying sizes, or of medical waste of varying volume or quantity. For the larger containers, it may be necessary to employ a mechanical hoist system to lower the heavier or more voluminous loads of carcasses of larger animals or larger quantities of medical waste into the vessel interior. 
     As noted above, the preferred embodiment includes agitating injector means  28  shown in  FIGS. 5A-5D  to accelerate the reaction rate between the solvent solution and the waste tissue by keeping the solvent in motion while the reaction is occurring. One such means is accomplished by circulating the solvent via loop  24  and pump  26  ( FIG. 1 ) and introducing the solvent into the interior of the vessel by injecting it via multiple jet ports at varying angles generally aimed at the bottom of the holding container  60  (see  FIG. 5A ). Such an arrangement keeps the solvent moving within the vessel interior, as well as keeping waste matter from accumulating on the bottom of the container  60 , which can result in the prolonging or slowing of the digestion process. Agitating injector means  28  preferably comprise a plurality of concentric flow reducers or nozzles  28   a  coupled to respective elbow members  28   b , which in turn are coupled to respective tube members  28   c , which finally are coupled to respective cross members  28   d . Each cross member  28   d  is connected to a screw-coupling member  28   e  for affixing the injector means to the upper end of the inflow conduit  24   a . Nozzles need not be conical as illustrated in  FIGS. 5A-D , but may vary in shape and size to suit particular applications. In a preferred embodiment, the opposing nozzles  29   a  are disposed at an included angle A of about 22.5 degrees ( FIG. 5C ), while opposing nozzles  29   b  are disposed at an included angle B of about 45 degrees ( FIG. 5D ), to enhance the agitation and mixing action of the injectors to facilitate the digestion reaction. Alternately, angles A and B may be varied to suit particular applications. 
     As shown in  FIG. 5A , the inflow conduit  24   a  delivering solvent to injector  28  extends into and, in a coaxial fashion, extends upwardly through the outflow conduit  24   b . Inflow conduit  24   a  is smaller in diameter than outflow conduit  24   b  such that the aqueous interior contents of the vessel  12  may drain downwardly into outflow conduit  24   b  as shown by the reference arrows “a” in  FIG. 5A . Outflow conduit  24   b  carries the solvent back to the solvent loop  24  and pump  26  (see  FIG. 1 ) and when necessary, through drain valve  41  to the sanitary drain  42 . It will be understood by those skilled in the art that the points of connection “b” shown in  FIG. 5A  must be sufficiently tight and withstand the highly basic, high-temperature, and high-pressure environment. It should be further understood the injector means may include separate injector nozzles disposed in fixed arrangements about the interior of the vessel to direct solvent at the waste matter. Such a configuration is useful in larger applications involving large diameter containers and large-volume waste matter. Such separate fixed injections may be utilized in lieu of or in addition to the injector assembly  28  shown and described herein. 
       FIG. 2  presents a flowchart depicting the cycle process of this invention. In operation, the waste matter is weighed and the weight and water and solvent ratios automatically determined by the PLC control means (box a). The appropriate amount of water (box b) and solvent (box c) is then introduced into the interior of the vessel based on the weight calculations made by the PLC control means. Water is typically added at the rate of 60% water to 40% tissue by weight, but may be added in other amounts according to the requirements of particular load amounts and types of waste. The alkali is added at the predetermined concentration based on the tissue weight. This is typically equivalent to a solution of 50% NaOH added by weight at a ratio of 15 to 20% of the total tissue weight. The heating means  30  ( FIG. 1 ) then heats the vessel interior (box d) to the digestion cycle temperature while closing the vent  34  (box e). System  10  then maintains that elevated temperature for a predetermined duration (box f) as calculated by the PLC control means based on the weight of the waste matter placed in the vessel for digestion. The system typically maintains the digestion temperature at about 150.degree. C. (302.degree. F.) for about 3 hours, or if operated at a lower temperature, for an appropriate time for that temperature based on a theoretical full digestion time of 16 hours at 100 degrees Celsius and halving the digestion cycle time for each 10 degrees Celsius increase in temperature, in accordance with the thermodynamics equation discussed above. More preferably, an appropriate safety factor is added to the theoretical digestion time at a given temperature to accommodate differences arising from variations in load size, composition, distribution, and the like. 
     Next, the system goes into the cooling cycle after digestion whereupon cooling water is admitted to the steam jacket interior  30  from water supply  20  ( FIG. 1 ) via conduit  20   c  to lower the temperature of the vessel interior (box g). This continues until the internal pressure within the vessel reaches about atmospheric pressure (101.3 kilopascals/14.7 pounds per square inch (PSI)), shown as a reading of zero on the pressure gauge or transducer, which measures pressure above 1.0 atmosphere. Once the system is cooled sufficiently, the vessel is drained to the sewer (sanitary drain  42 ) by the control means opening the vent  34  (box h) and drain valve  41  (box i) to drain the liquid contents from within the vessel interior down to a predetermined point, at which point drain valve  41  is closed (box j) while flushing water is continued to be introduced to flush the vessel interior (box k) until the interior is preferably about half full. At that point in the cycle, the vessel interior is sprayed with rinsing liquid and the contents are circulated through the injectors  28  for a predetermined time before the drain is again opened to rinse away any residual materials remaining within the interior of the vessel (boxes l and m). The drain is then closed again (box n) and the vessel partially filled again and a final heated rinse cycle is then carried out (boxes o, p, and q). At this stage, the digestion and cooling cycle are complete and the vessel may be opened and the waste holding container removed and emptied. The empty container is then replaced within the vessel interior rendering the system ready for subsequent operation. 
     This invention also presents a method for digesting or neutralizing waste matter comprising organic tissue or infectious, biohazardous, hazardous, or radioactive agents, by subjecting the waste matter to a controlled alkaline hydrolysis cycle and generating a sterile resultant suitable for conventional sanitary disposal. The preferred method compromises the steps of: 
     (a) providing a closed reaction vessel  12  coupled to a heating-cooling means; 
     (b) receiving the waste matter within the closed reaction vessel  12 ; 
     (c) determining the weight of the waste matter received within said vessel and generating weight output data by way of a weight transducer  18  coupled to the vessel  12 ; 
     (d) controlling the operation of the system, including receiving and considering the weight output data generated by the weight determining transducer  18  and determining the appropriate amounts of water and solvent to introduce into the interior of the vessel  12 ; 
     (e) after determining the appropriate amounts of water and solvent to introduce into the interior of the vessel, initiating a vacuum on the vent of the vessel to remove odors while introducing water within the vessel interior in an amount determined by the PLC controller via water supply  20  and conduit  20   a  based on the weight output data, and introducing the highly basic solvent into the interior of the vessel in an amount determined by the PLC controller based on the weight output data; 
     (f) heating the interior of the vessel to a first predetermined temperature level by way of the heating means (steam jacket  30 ) after the introduction of water and alkali solution into the interior of the vessel; 
     (g) mixing or agitating the contents of the vessel to enhance the interaction between the solvent and the tissue by way of agitating injector means  28 ; 
     (h) continuing to vent the interior of the vessel by way of vent  34  upon initiation of the digestion cycle and closing the vent when the temperature within the vessel reaches a first predetermined temperature; 
     (i) heating the vessel interior to the digestion cycle temperature and maintaining that temperature for a predetermined duration; 
     (j) cooling the interior of the vessel after the digestion cycle has run by introducing cooling water from supply  20  to heating means  30 ; 
     (k) operating eductor  40  and opening vent  34 , thereby creating a vacuum, to remove any odorous gases from within the vessel throughout the remainder of the post-digestion process; 
     (l) balancing the vacuum created by eductor  40 , via vacuum balancer  46 , to prevent such vacuum from interfering with the draining of the vessel by selectively admitting ambient air into the vessel interior during the remainder of the post-digestion process; 
     (m) opening drain valve  41  to drain the digested liquid portion of the vessel contents and initiating a spray rinse by opening line  20   a  to remove any remnants of the solvent solution from the solid waste remains within the vessel interior; 
     (n) closing drain valve  41  while maintaining spray line  20   a  open to continue the spray rinse via sprayball  20   e , and opening water line  20   d  to refill the vessel with water to approximately 15 cm (6 in.) above the bottom of the digestion container  60  and restarting the pump  26  to recirculate the rinse solution throughout the solid waste remains via loop  24  for a predetermined time to allow for additional rinsing of the solid waste remains; 
     (o) opening drain valve  41  to drain the rinsing liquid portion of the vessel contents; 
     (p) initiating another spray rinse by opening line  20   a  to further remove any remaining solvent rinse solution from the solid remains; 
     (q) closing drain valve  41  while maintaining spray line  20   a  open and opening water line  20   d  to, again, refill the vessel with water to approximately 15 cm (6 in.) above the bottom of the digestion container  60  and restarting the pump  26  to recirculate a rinse solution throughout the solid waste remains for a second time; 
     (r) heating the second rinse solution to a predetermined temperature and recirculating the second heated rinse solution for a predetermined time to allow the solution to remove any entrained digestion solution from the solid waste remains; 
     (s) opening drain valve  41  to allow the second heated rinsing solution to drain; 
     (t) opening spray line  20   a  for a final rinse of the vessel interior and solid waste remains while maintaining drain valve  41  open; and 
     (u) closing spray line  20   a  to discontinue the rinse and allowing the liquid contents of the vessel to drain; and 
     (v) finally, opening the lid  16  of the vessel and removing the waste remains from the primary opening for disposal in a sanitary landfill or for usage as solid fertilizer material. 
     It should be noted that the fill levels discussed above may be modified as a function of waste material load size, with larger loads requiring higher fill levels. In other words, enough liquid should be added such that the waste material is completely submerged for reduction by the alkaline solution. 
     As mentioned above, an additional feature of the closed vessel is to allow the solid waste remains to be removed from a secondary opening (not shown) arranged on the vertical side of the vessel. This feature allows the vessel to be positioned in such a configuration that the primary opening may be located within a contaminated portion of the facility, while the remaining portions of the system are located within a clean portion of the facility. This would allow contaminated materials to be processed and sterilized, then for the sterile solid waste remains to be removed from the secondary opening as sterile remains into a clean area for final disposal. Thereafter, the secondary opening would be sealed prior to the opening of the primary opening for the loading of waste for another processing cycle. Such a configuration is referred to as “dirty side feed/clean side removal.” Such an embodiment would alter step (u) above to read as follows: 
     (u) finally, opening the vessel and removing the solid waste remains from the secondary opening for disposal in a sanitary landfill or for usage as solid fertilizer material, then closing and re-sealing the secondary opening prior to opening the primary opening for the loading of new waste material for a subsequent cycle, wherein the dirty side door or lid and the clean side door or lid are electrically interlocked to assure compliance with regulations and prevent contamination of the clean side. 
     Finally, set forth below is an example of the system of this invention and its method of operation in use. 
     EXAMPLE ONE 
     Prior to filling the vessel with, for example, animal carcasses containing infectious or hazardous agents, the lid of the vessel is closed in order to “zero” the load scale. The lid is then opened and the vessel filled with waste matter to the desired volume. Preferably, the load should be at least 20% of the vessel&#39;s capacity (by weight) but not more than the weight capacity of the vessel, in which case the system will not operate and the excess weight must be removed. The vessel lid is then closed and secured. The PLC controller is then activated to initiate the digestion process by first determining the weight of the waste matter within the vessel. The digestion cycle is then initiated whereby water is preferably added at the rate of 60% water to 40% tissue by weight, alkali is added at the predetermined concentration based on the tissue weight. Such concentration is normally equivalent to a solution of 50% NaOH added by weight at a ratio of 15 to 20% of the total tissue weight. 
     The heating step is then initiated to raise the temperature of the interior of the vessel to the predetermined first digestive cycle temperature for a predetermined duration to completely digest the carcasses. In a preferred mode, the cycle holds the digestion temperature to at least 110.degree. C., preferably about 130.degree. C., and most preferred about 150.degree. C. At 150.degree. C., the digestion cycle is normally about 3 hours in duration. 
     Once the digestive cycle is complete, the PLC control means initiates the cooling cycle, utilizing cold water flushed through the sleeve jacket  30  of the vessel. Once the vessel has cooled sufficiently, the vessel is drained to the sewer, then partially refilled with cold water and the interior rinsed. The vessel is then drained again, partially refilled again and this second rinse solution heated if desired. After this hot rinse, the vessel is then drained and it contents sprayed with a final spray rinse. The cooling cycle is then complete and the system shuts down while the drain is opened to empty completely the interior of the vessel. 
     If the operator is present at the completion of the cooling cycle, the vessel may at that point be opened and the waste-carrying basket removed and emptied. The basket is then replaced, making the system ready for a new cycle. In the event, however, the operator is not present when the cooling cycle is complete, when the cycle runs at night for example, the operator should initiate the spray rinse cycle for a short duration, preferably about 30 seconds. After the final spray is complete, the vessel may be opened and the waste safely disposed of. 
       FIGS. 6A-6E  illustrate another preferred embodiment of the present invention, a chemical waste reduction system  110  for chemically reducing masses of hydrolyzable waste materials ranging up to about 25 pounds. The system  110  includes a closeable reaction chamber or vessel  112  capable of containing a highly alkaline solvent solution and a volume of waste matter (such as animal tissue or carcasses, regulated medical waste, contamination on surgical instruments, and the like). Alternately, the hydrolyzable waste materials may be organic contamination on medical instruments not specifically limited to surgical instruments. 
     Preferably, a portion of the vessel  112  is defined by a double-walled structure. Also preferably, the vessel interior  114  should be coated with an alkaline resistant material, such as stainless steel or a ceramic material. More preferably, the vessel  112  is constructed from a material capable of withstanding the combination of pH levels, temperatures, and pressures it may be subjected to during a hydrolysis operation. Suitable materials include certain formulations of stainless steel. The vessel  112  is preferably capable of being closed in an air tight fashion to provide the necessary environment within the vessel interior  114  for the controlled alkaline hydrolysis cycle to be carried out to completion, as well as to prevent the highly alkaline solvent and waste materials from escaping into the environment. Thus, the lid or cover  116  of the vessel  112  is preferably capable of being closed tightly and sealed shut to withstand the temperatures and pressures of the digestion cycle and prevent the inadvertent introduction of atmosphere (particularly carbon dioxide) into the vessel  112  interior and, more importantly, prevent the escape or inadvertent exhausting of the contents of the vessel  112  interior to atmosphere. Such closure of the vessel  112  may be achieved by conventional lid clamps well known in the industry (not shown), or by any convenient closure means available to one of ordinary skill in the art. 
     The system  110  further includes an electronic controller  1117 , such as the conventional programmable logic controller (PLC) means described above. Preferably, the system  110  further includes a weight sensor or transducer  118  (shown schematically) operationally coupled to the vessel  112  and electrically coupled to the electronic controller  117  for determining the weight of the waste matter received within the vessel  112  and for generating an output signal to the controller  117  including such weight data. The transducer  118  is normally preset such that the weight of the vessel  112  without contents equals zero weight. The contents weight data may then be inputted to the electronic controller  117  for, based on the weight output data, determining the appropriate amounts of water and solvent to introduce into the interior of the vessel  112 . In the case of smaller vessels  112  (having capacities, for example, to digest from about 2 to about 20 pounds of waste material) a predetermined amount of alkaline solvent (formulated to digest the maximum waste material load of the vessel  112 ) may be preferred for use with any amount of waste material up to the maximum load of the vessel  112 . In this case, the weight data may instead be used to disable the system  110  if the maximum capacity of the vessel  112  is exceeded. 
     The system  110  further includes connecting a water supply  120  operationally connected to the vessel  112 , such as via conduit  120   a . The highly alkaline solvent is produced in the vessel  112  by mixing water and dry alkaline earth, alkali hydroxides, or alkali metal oxides therewith to form a highly alkaline solution. Alternately, a highly alkaline solution may first be prepared and then added into the vessel  112 .  FIG. 6E  illustrates the plumbing of the system in greater detail. Conduit  120   a  connects through valves  124  to water inlet  126  and/or injector means  128  for introducing water into the vessel  112 . 
     As with the previous embodiment, it is preferred that the so-formed solvent solution be heated in order to more efficiently and quickly accomplish the chemical reduction of the hydrolyzable waste material. Therefore, the system  110  preferably includes a heater  130  operationally connected to and positioned in thermal communication with the vessel  112 . More preferably, the heater  130  is an electric hot plate in thermal contact with the base of the vessel  112  capable of heating the interior of the vessel  112  to a first predetermined temperature level after the introduction of water and solvent into the vessel interior  114 . Alternately, any convenient type of heater  130  may be used to heat the vessel  112 , such as the steam jacket described in the previous embodiment or any other heating means known to one of ordinary skill in the art. Electricity is supplied to the heater  130  by a power supply  132  via conduit  132   a . Preferably, a temperature sensor  119  (such as a thermocouple or the like) is positioned in thermal communication with the interior of the vessel  114  such that the temperature of the interior of the vessel  114  may be continuously monitored or queried upon demand. More preferably, the heater  130  and the temperature sensor  119  are both connected in electric communication with electronic controller  117 , such that electronic controller  117  may regulate the output of the heater  130  to maintain the temperature of the interior of the vessel  114  according to a predetermined or desired time/temperature profile. 
     The system  110  also preferably includes a vent  140  (discussed in greater detail below), which is preferably disposed in the open state upon initiation of the cycle and thereafter is preferably closed by the electronic controller  117  when the temperature within the vessel  112  reaches a predetermined first temperature. The temperature within the vessel  112  is gauged by the vessel thermocouple  119 , while the pressure within the vessel  112  may be measured by a pressure sensor (not shown) such as a PSI transducer. 
     The system  110  also preferably includes agitation means  133  for circulating and mixing solvent and partially dissolved waste matter. Agitation means  133  is preferably magnetic, such as a magnetic stirrer  135  positioned such that a magnetic field may be generated within the vessel  112  and used to rotate one or more magnetic stir rods  137  positioned within the vessel  112 . The magnetic stirrer  135  may be functionally combined with the heater  130 , such as in a hot plate/stirrer combination readily known to one of ordinary skill in the art. While a magnetic stirrer  135  is preferred, agitation means  133  may include any convenient stirring means familiar to one of ordinary skill in the art to mix and agitate the contents of the vessel interior  114 . Such agitation enhances the interaction between the highly alkaline solvent and the dissolving waste matter to keep the vessel contents moving and to prevent waste matter from accumulating at the bottom of container  112 . A further benefit of agitation is the reduction of digestion cycle time. Agitation of the contents may be achieved by various means, including external mechanisms coupled to the vessel  112 , such as rocking or shaking assembly that physically moves the vessel  112 . All such alternative means of mixing or agitating the vessel contents are contemplated by this invention. 
     Preferably, the system  110  also includes a ventilation system for relieving excess pressure from the vessel interior  114  when the vessel  112  is closed. A fluid conduit  142  connects the vent  140  to a drain line  144 . Preferably, a check valve  146  is connected between the  140  and the drain line  144  to prevent contamination of the vessel  112 . The drain line  144  is also connected to a water outlet  148  formed in the vessel  112  for drainage of the solvent solution and any dissolved waste matter. 
     The system may also include an eductor  150  connected between the water outlet  148  and the drain line  144 . Flushing water is admitted to the eductor  150  by the water supply  120  via conduit  120   b . The action of the eductor  150  draws the air and any odorous gas from within the interior of the vessel  112  through fluid conduit  142 , whereupon the air and odorous gas is eventually entrapped with the flushing water at eductor  150  to, in turn, be removed from the system via drain conduit  144 . The temperature of the fluid at the drain may be gauged by a thermocouple (not shown) to monitor the effluent temperature prior to disposal in a sanitary sewer system. The vacuum-creating eductor  150  substantially reduces the odorous gases that may escape from rotting carcasses while the vessel  112  is filling, and may also be actuated to draw gasses from the vessel  112  while or after the waste is being hydrolyzed, if desired. 
     In operation, once the contents of the vessel are drained after the digestion cycle (heating and cooling), the interior of the vessel may be rinsed with cold water via water inlet  128  with the water outlet  148  open. After a few minutes, the water outlet  148  is closed to allow the vessel  112  to begin to fill with water. The vessel  112  is now considered ready for another hydrolysis cycle, and may be filled with waste for reduction. Once the vessel  112  is filled with a predetermined amount of water (at least enough such that the waste matter is covered) a predetermined amount the highly alkaline powder is added and combined with the water to form a highly alkaline solvent solution. The contents are then agitated by the magnetic stirrer  135  and stir rod  137 , and the contents are heated to about 98 degrees Celsius for a predetermined period of time to chemically reduce the waste material. The vessel  112  is then allowed to cool, and the water outlet  148  is opened and rinse water is introduced into the vessel  112 . The water outlet may be closed to allow rinse water to accumulate and rinse any remaining solids. The water outlet  148  is then re-opened and the liquid contents of the vessel  112  are allowed to drain. Thereafter, if desired or necessary, the water outlet  148  is closed for a second time and the vessel  112  is allowed to again fill with water. Heat may then be applied again to the vessel  112  to heat the liquid within the vessel to approximately 95.degree. C. (203.degree. F.), whereupon an enhanced rinse/diffusion is initiated. The time and temperature used in this post-digestion heating stage may vary. 
     The preferred system further includes a liquid permeable container  160 , such as a basket, capable of holding the waste material within the vessel interior  114  during the waste reduction operation to completely immerse the waste material within the solvent solution. Referring again to  FIGS. 3A-3C , such a container preferably includes a cylindrical article  60  defined by a steel mesh screen  62  having an upper rim portion  64 , a lower rim portion  66 , and a lid  68  to enclose the waste tissue within the container  60 . (While the preferred shape of the container is cylindrical, other non-cylindrical shapes are suitable and should be considered as being within the scope of this invention.) Attached to the lid  68  is preferably a handle  68   a . The container  60  is sized to fit within the interior of the vessel  114 . As shown in  FIGS. 3B and 3C , both the lid  68  and the bottom of the container include the stainless steel mesh  62 , which is preferably constructed from stainless steel screen mesh having about 3 mm to about 6 mm (one-eighth (⅛) to one-quarter (¼) inch) screen mesh. The lid  68  may be releasably secured to the body  61  of the container via conventional means. Handle  68   a  may be equipped with an eyelet-like portion  68   b  to receive attachment means for lowering and raising the container into and out of the vessel interior. After the waste reduction operation has completed, the container  60  may be hoisted out of the vessel  112 , thereby removing the undigested solid debris remaining within the container  60 . 
     The method of using the system  110  is similar to that of the first embodiment discussed above, and includes the elements of providing a substantially alkaline-resistant vessel, providing a highly alkaline solvent, providing an amount of waste matter having a mass less than or equal to a predetermined maximum mass, immersing the waste matter in the solvent within the interior of the vessel, heating the solvent and the waste matter, and allowing the waste matter to remain within the solvent until digested to form an aqueous solution with residual solid waste matter. Preferably, the waste matter remains in the solvent for a predetermined length of time calculated to substantially completely dissolve a predetermined maximum mass of waste matter at a predetermined operating temperature. Preferably, the predetermined operating temperature is between about 95 and about 98 degrees Celsius. However, for a given solvent pH or concentration, hydrolysis may be achieved at lower temperatures (i.e., 90 degrees Celsius or even lower) by increasing the cycle time according to the Q10 Rule, as discussed above. The extent of digestion or degradation of the waste matter may be increased by lengthening the amount of time the waste matter is immersed in the solvent at the predetermined temperature, increasing the temperature of the solvent and waste matter, adding a catalyst material, or some combination of the above. 
     After cooling, the post-digestion end product may then be directly disposed of through conventional disposal means, such as a sanitary sewer or landfill, used as a fertilizing agent in land use applications, or the like. If preferred, the post-digestion stage may also include rinsing or flushing of the resultant waste product and the interior of the vessel. The system and method of this invention also substantially reduce the amount of post-digestion solid waste to be disposed of. 
       FIGS. 7A-7D  illustrate still another preferred embodiment of the present invention, a chemical waste reduction system  210  for chemically reducing masses of hydrolyzable waste materials ranging up to about 3000 pounds or more. The system  210  includes a closeable reaction chamber or vessel  212  capable of containing a highly alkaline solvent solution and a volume of waste matter (such as animal tissue or carcasses, regulated medical waste, and the like). Preferably, the vessel  212  is defined by a double-walled container structure. Also preferably, the vessel interior  214  should be coated with an alkaline resistant material, such as a suitable stainless steel or a ceramic material. More preferably, the entire vessel  212  is constructed from a material capable of withstanding the combination of pH levels, temperatures, and pressures it may be subjected to during a hydrolysis operation, such as certain formulations of stainless steel. The vessel  212  is preferably capable of being closed in an air tight fashion to provide the necessary environment within the vessel interior  214  for the controlled alkaline hydrolysis cycle to be carried out to completion as well as to prevent the highly alkaline solvent and waste materials from escaping into the environment. Thus, the lid or cover  216  of the vessel  212  is preferably capable of being closed tightly and sealed shut to withstand the temperatures and pressures of the digestion cycle and prevent the inadvertent introduction of atmosphere (particularly carbon dioxide) into the vessel  212  interior and, more importantly, prevent the escape or inadvertent exhausting of the contents of the vessel  212  interior to atmosphere. Such closure of the vessel  212  may be achieved by conventional lid clamps well known in the industry (not shown), or by any convenient closure means available to one of ordinary skill in the art. 
     The system  210  further includes an electronic controller  217 , such as the conventional programmable logic controller (PLC) means described above. Preferably, the system  210  further includes a weight sensor or transducer  218  (shown schematically) operationally coupled to the vessel  212  and electrically coupled to the electronic controller  217  for determining the weight of the waste matter received within the vessel  212  and for generating an output signal to the controller  217  including such weight data. The transducer  218  is normally preset such that the weight of the vessel  212  without contents equals zero weight. The contents weight data may then be inputted to the electronic controller  217  for, based on the weight output data, determining the appropriate amounts of water and solvent to introduce into the interior of the vessel  212 . In the case of smaller vessels  212  (having capacities, for example, to digest from about 200 to about 500 pounds of waste material), or, optionally, in the case of larger vessels, a predetermined amount of alkaline solvent (formulated to digest fixed increments of waste material load) may be preferred for use with any amount of waste material up to the maximum load of the vessel  212 . In this case, the weight data may instead be used to disable the system  210  if the maximum capacity of the vessel  212  is exceeded. 
     The system  210  further includes connecting a water supply  220  to the vessel  212 , such as via conduit  220   a . The highly alkaline solvent is produced in the vessel  212  by mixing water and dry alkaline earth, alkali hydroxides, or alkali metal oxides therewith to form a highly alkaline solvent solution. Conduit  220   a  connects through valves  224  to water inlet  226  and/or injector means  228  for introducing water into the vessel  212 . 
     As with the previous embodiments, it is preferred that the so-formed solvent solution be heated in order to more efficiently and quickly accomplish the chemical reduction of the hydrolyzable waste material. Therefore, the system  210  preferably includes a heater  230  operationally connected to and positioned in thermal communication with the vessel  212  or immersed in the liquid contents of the vessel  212 . More preferably, the heater  230  is a burner (such as a natural gas burner, and oil burner, or the like) extending below the vessel  212  and in thermal communication therewith or inserted into the vessel  212  and in direct thermal communication with the vessel contents. The burner is preferably adapted to generate sufficient thermal energy to heat the interior of the vessel  214  to a first predetermined temperature level after the introduction of water and alkaline solvent thereinto. Alternately, any convenient type of furnace or heater  230  may be used to heat the vessel  212 , such as the steam jacket described in the previous embodiment or any other heating means known to one of ordinary skill in the art. 
     Preferably, a temperature sensor  219  (such as a thermocouple) is positioned in thermal communication with the interior of the vessel  214  such that the temperature of the interior of the vessel  214  may be continuously monitored or queried upon demand. More preferably, the heater  230  and the temperature sensor  219  are both connected in electric communication with electronic controller  217 , such that electronic controller  217  may regulate the output of the heater  230  to maintain the temperature of the interior of the vessel  214  according to a predetermined or desired temperature profile. 
     The system  210  may also optionally include agitation means for circulating and mixing solvent and partially dissolved waste matter. The system  210  may also preferably include a vent  240 , which is preferably disposed in the open state upon initiation of the cycle and thereafter is preferably closed by the electronic controller  217  when the temperature within the vessel  212  reaches a predetermined first temperature. A fluid conduit  242  connects the vent  240  to a fluid drain line or flue  244 . The temperature within the vessel  212  is gauged by the vessel thermocouple  219 , while the pressure within the vessel  212  may be measured by a pressure sensor (not shown) such as a PSI transducer. 
     In cycle, once the contents of the vessel are drained after a previous digestion cycle (heating and cooling), the interior of the vessel may be rinsed with cold water via water inlet  228  with the water outlet  248  open. After a few minutes, the water outlet  248  is closed to allow the vessel  212  to begin to fill with water. The vessel  212  is now considered ready for another hydrolysis cycle, and may be filled with waste for reduction. Once the vessel  212  is filled with a predetermined amount of water (at least enough such that the waste matter is covered) a predetermined amount the highly alkaline powder is added and combined with the water to form a highly alkaline solvent solution. Alternately, a concentrated alkaline solution may be added to the water to yield a highly alkaline solvent solution. The contents are then agitated by a stirring means, such as by pumping the highly alkaline solvent solution through the vessel  212 , and the contents are heated to about 98 degrees Celsius for a predetermined period of time to chemically reduce the waste material. The vessel  212  is then allowed to cool, and the water outlet  248  is opened and rinse water is introduced into the vessel  212 . The water outlet may be closed to allow rinse water to accumulate and rinse any remaining solids. The water outlet  248  is then re-opened and the liquid contents of the vessel  212  are allowed to drain. Thereafter, if desired or necessary, the water outlet  248  is closed for a second time and the vessel  212  is allowed to again fill with water. Heat may then be applied again to the vessel  212  to heat the liquid within the vessel to approximately 95.degree. C. (203.degree. F.), whereupon an enhanced rinse is initiated. The time and temperature used in this post-digestion heating stage may vary. 
     The preferred system further includes a liquid permeable container  260 , such as a basket, capable of holding the waste material within the vessel interior  214  during the waste reduction operation to completely immerse the waste material within the solvent solution. The container  260  is preferably a basket shaped to fit into the vessel  212  and is preferably formed of alkaline-resistant perforated stainless steel. The perforation is preferably defined as a pattern of 6 mm (⅜ inch) holes formed through the steel basket  260 . After the waste reduction operation has completed, the container  260  may be hoisted out of the vessel  212 , thereby removing the undigested solid debris remaining within the container  260 . 
     The method of using the system  210  is similar to that of the embodiments discussed above, and includes the elements of providing a substantially alkaline-resistant vessel, providing a highly alkaline solvent, providing an amount of waste matter having a mass less than or equal to a predetermined maximum mass, immersing the waste matter in the solvent within the interior of the vessel, heating the solvent and the waste matter, and allowing the waste matter to remain within the solvent until digested to form an aqueous solution with residual solid waste matter. Preferably, the waste matter remains in the solvent for a predetermined length of time calculated to substantially dissolve a predetermined maximum mass of waste matter at a predetermined operating temperature. Preferably, the predetermined operating temperature is between about 95 and about 98 degrees Celsius. The extent of digestion or degradation of the waste matter may be increased by lengthening the amount of time the waste matter is immersed in the solvent at the predetermined temperature, increasing the temperature of the solvent and waste matter, adding a catalyst material, or some combination of the above. After cooling, the post-digestion end product may then be directly disposed of through conventional disposal means, such as a sanitary sewer or landfill, used as a fertilizing agent in land use applications, or the like. If preferred, the post-digestion stage may also include rinsing or flushing of the resultant waste product and the interior of the vessel. The system and method of this invention also substantially reduce the amount of post-digestion solid waste to be disposed of. 
     Although the invention has been described with preferred embodiments, those skilled in the art will understand that modifications and variations may be made without departing from the scope of the inventions as set forth in the following claims. Such modifications and variations are considered to be within the purview and scope of the appended claims.