System and process for treatment of and sterilization of waste including medical waste

Abstract

The present invention provides a process and system for waste treatment that provides the benefits of both bio-digestion and plasma sterilization. The process and system of the present invention ensures effective breakdown of organic material and thorough elimination of pathogens, resulting in safe and efficient waste management of waste streams comprising a compostable bio-degradable breathable Personal Protective Equipment (PPE) article comprising a compostable plant-based material wherein the compostable plant-based material comprises a compostable starch-based polymer and wherein the compostable bio-degradable breathable PPE meets the requirements of a Class 1 medical device as classified according to the Medical Device Regulation (EU) 2017 / 745 (MDR).

Description

System and Process for treatment of and Sterilization of waste including Medical WasteFIELD OF THE INVENTION

[0001] The present invention relates to a waste treatment system comprising a process for treatment of and sterilization of waste including medical waste and other waste from an environment producing mixed waste streams for instance, from a healthcare setting which would typically produce waste in the form of medical waste as well as food waste and other waste forms or waste streams. In particular, the present invention discloses a waste treatment system and process for treatment of compostable, bio-degradable breathable Personal Protective Equipment (PPE), used in a healthcare environment for example, a hospital, or nursing care / nursing home settings. Furthermore, the present invention provides a waste treatment system and process for treatment of compostable, bio-degradable breathable Personal Protective Equipment (PPE), as a first feed stream and food waste and / or other waste as a second feed stream from a healthcare setting, in a single treatment system and process in accordance with the present invention, and provides a process for converting the first feed stream and the second feed stream into soil-friendly compost. Thus, in summary, the present invention provides a process and system of converting such waste from a healthcare setting into compost in a and in effect, provides a novel system and process of “medical waste composting” which is also be referred to by the inventors as “medical composting”.BACKGROUND

[0002] Waste management is a critical environmental and public health issue. Biodigestion is an effective method for breaking down organic waste using bacteria. However, there is a need for an effective waste management system for multiple waste streams including food waste for instance together with traditional medical waste including Personal Protection Equipment (PPE) and in particular, including compostable Personal Protection Equipment (PPE) such as disclosed in the Applicant’s co-pending UK Patent application No. UK Patent Application No. 2313033.9.

[0003] Herein, we refer to a biodigester or biodigester apparatus which terms are to be understood as being interchangeable. Biodigester are known and typically, comprise a sealable container where microorganisms break down organic material into biogas and fertilizer through a natural process. This anaerobic digestion process is possible because the environment in the biodigester provides an oxygen-free environment where bacteria can consume the waste and grow.

[0004] However, known bio-digesters do not effectively eliminate all pathogens present in the waste streams and in particular, in medical waste streams which typically, comprise ESKAPE pathogens comprising representatives of several, clinically relevant, multi-drug resistant bacterial species such as the following: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp. . In particular, there is no known system for treatment of compostable medical waste and in particular, no known system for treatment of a mixed waste stream comprising compostable medical waste and other waste such as food waste.

[0005] The present invention seeks to alleviate the disadvantages of known waste management systems and processes.BRIEF SUMMARY OF THE INVENTION

[0006] Features of the present invention are set out in the appended Claims.

[0007] Accordingly, the present invention relates to a system and process in which a combination of physical, thermal, enzymatic and bacterial processes are carried out to produce compostable medical waste. Furthermore, in a preferred embodiment, means for sterilization of waste stream comprising the compostable medical waste is provided. The means for sterilization preferably comprises a plasma device adapted and configured for the delivery of plasma to sterilize the medical waste. In particular, the present invention provides on-site treatment of multiple waste feedstock streams including compostable medical waste stream comprising compostable Personal Protection Equipment (PPE) and the conversion thereof to bio-digestate.

[0008] In a first aspect, the present invention provides a process for producing compostable medical waste, wherein the medical waste stream comprises compostable Personal Protection Equipment (PPE); the process being characterised by the following steps: subjecting a medical waste stream to a combination of physical, thermal, enzymatic, and bacterial processes to convert the medical waste into compostable material; further comprising a step of sterilizing the compostable medical waste stream using a plasma device, the plasma device being adapted and configured to deliver plasma for sterilization of the medical waste; and wherein the process provides on-site treatment of multiple waste feedstock streams, including the compostable medical waste stream, and converts the compostable medical waste into bio-digestate. Advantageously, the compostable bio-degradablebreathable PPE meets the requirements of a Class 1 medical device as classified according to the Medical Device Regulation (Ell) 2017 / 745 (MDR).

[0009] The present invention accordingly provides a process and system for treatment of waste comprising compostable Personal Protective Equipment (PPE) comprising a compostable plant-based material; and the compostable PPE also meets the requirements of a Class 1 medical device as classified according to the Medical Device Regulation (Ell) 2017 / 745 and therefore, can be referred to as “medical grade Personal Protective Equipment (PPE).”

[0010] The process and system of the present invention has the advantage that it provides a process for converting waste comprising compostable bio-degradable breathable Personal Protective Equipment (PPE) articles comprising a compostable plantbased material wherein the compostable plant-based material comprises a compostable starch-based polymer and wherein the compostable bio-degradable breathable PPE meets the requirements of a Class 1 medical device as classified according to the Medical Device Regulation (EU) 2017 / 745 (MDR).

[0011] Furthermore, the PPE that is referred to in the present application is compostable according to the definition of “compostable” as set out in EU standard EN 13432 and ASTM 6400, that is, that the biologically based material e.g. starch-based material meets the following characteristics: Degradation of the material by at least 90% in 6 months when subjected to an environment rich in carbon dioxide. Thus, the compostable PPE of the present invention meets the requirements of EU standard EN 13432 and ASTM 6400.

[0012] It is also notable that the compost produced by the process and system of the present invention has the advantage of being “soil-safe”. Recently, in the context of soil quality, the terms, ‘soil health’ or “soil safe” have been used as these terms emphasise the capacity of the soil to deliver multiple functions including the re-cycling of nutrients, sequestration of carbon and regulation of the climate, purification and storage of water as well as providing a habitat for biodiversity. Thus, the term, “soil health” and “ soil safe” are defined as the continued capacity of soil to function as a living ecosystem that sustains plants, animals and humans. Hence, the compostable PPE of the present invention can be composted and returned to the soil as it is ’’soil safe” and will not impact on the continued capacity of the soil to function as a vital living ecosystem.

[0013] Preferably, the process comprises the step of delivering non-thermal plasma for the sterilization of the compostable medical waste.

[0014] Optionally, the process comprises pre-treatment steps including shredding or grinding of the medical waste stream before thermal, enzymatic, and bacterial treatment step. Ideally, the thermal, enzymatic and bacterial treatment steps are carried out in a biodigester apparatus in accordance with the present invention.

[0015] Preferably, the thermal process is carried out at temperatures between 50°C and 90°C to facilitate enzymatic and bacterial breakdown of the medical waste.

[0016] Preferably, the enzymatic process involves the use of specific enzymes to break down organic components of the compostable PPE.

[0017] Ideally, the bacterial process involves the use of anaerobic bacteria to convert the medical waste into bio-digestate.

[0018] Advantageously, the bio-digestate provides a soil-friendly compostable product.

[0019] In a further aspect of the present invention, there is provided an apparatus for treating waste wherein the apparatus comprises a sealable housing including at least one inlet for introducing at least one feedstock stream; and at least one outlet for exiting of the output from the apparatus; wherein the apparatus also comprises means for treating the feedstock comprising physical, thermal, enzymatic and bacterial processing in the apparatus.

[0020] Preferably, the apparatus comprises a sealable bio-digester and more preferably, comprises a sealable biodigester comprising a sterilising device for sterilization of the treated waste before the treated waste is released via the output from the apparatus.

[0021] Advantageously, the apparatus of the present invention is adapted to support a combination of physical, thermal, enzymatic and bacterial processes to be carried out and to produce bio-digestate, preferably, bio-digestate that is soil friendly. Furthermore, in a preferred embodiment, means for sterilization of waste stream comprising the compostable medical waste is provided. The means for sterilization preferably comprises a plasma device adapted and configured for the delivery of plasma to sterilize the medical waste.

[0022] In particular, the system and apparatus of the present invention has the advantage of providing on-site treatment of multiple waste feedstock streams including compostable medical waste stream comprising compostable Personal Protection Equipment (PPE) and the conversion thereof to bio-digestate.

[0023] Preferably, the apparatus of the present invention is adapted to enhance the efficiency of waste treatment by combining the organic breakdown capabilities of biodigestion with the pathogen elimination capabilities of plasma sterilization. This system comprises several features, including pre-biodigester treatment, Bio-digestor parameterand at least one plasma generation means and means for directing the plasma for delivery in a pre-determined location to the contents of the bio-digester apparatus.

[0024] The present invention has the advantage that it provides an improved process for waste treatment of waste comprising multiple feedstock waste streams inputs into the biodigester apparatus of the present invention.

[0025] The present apparatus is adapted for treating medical waste and for producing a compostable bio-digestate which is soil-safe and can be used as a soil enhancer.Optional step: Pre- treatment of the waste before input into the bio-digester apparatus

[0026] Shredding of the waste to increase surface area of waste material to optimise subsequent processes.

[0027] The shredder of the present application is an industrial fine-tooth mini shredder with shearing action; a fully sealed body housing with 2-3 / 4" hardened hex shafting, mechanical seals and direct inline. In a preferred embodiment, the shredding device further comprises:• High Torque Gear Drive; and optionally,• Mechanical Shaft Seals; and optionally,• Precision Ground Gears; and optionally,• Hardened and Ground Cutters; and optionally,• High Strength Housing.Bio-digestion process and bio-digestion parameters

[0028] The specific conditions that support the growth and activity of thermophilic bacteria in the bio-digestor of the present invention include the following: Enzymes, temperature range, pH range, oxygen levels and optionally, sterilisation process preferably, sterilisation by exposure of the bio-digestate to plasma after the bio-digestion process and most preferably, before exit of the bio-digestate from the bio-digester.

[0029] Each of these features will now be described in more detail below:

[0030] A multi-enzyme blend to break-down proteins, carbohydrates and celluloses. This blend consists of amylase, proteases and cellulases.

[0031] During hydrolysis, complex polymers like carbohydrates, proteins and fats are being degraded into sugars, amino acids and long chain fatty acids respectively. This breaking down process occurs primarily through the activity of extracellular enzymes (lipases, proteases, cellulases and amylases) secreted by hydrolytic bacteria.

[0032] Thermophilic bacteria grow optimally at temperatures between 45°C (113°F) and 80°C (176°F) and preferably under 72°C. pH Levels

[0033] The optimal pH for thermophilic bacteria varies depending on the species but generally ranges from neutral (pH 7) to slightly acidic or alkaline (pH 6 to 8).Oxyaen Levels

[0034] Thermophilic bacteria require a certain level of water activity to maintain cellular functions. They generally prefer environments with high humidity or moisture content.Sterilisation step, preferably using Plasma

[0035] Plasma technology is rapidly becoming an established green technology in both the medical and food sectors in surface disinfection applications for the inactivation of vegetative cells, spores, oocysts, enzymes and toxins.

[0036] Plasma is comprised of ionized, partially ionized and neutral particles referred to as reactive species, which interact disruptively with cellular structures and / or extracellular bioproducts (e.g. enzymes, toxins).

[0037] Plasma can be generated under high temperature and pressures (thermal plasma) or under atmospheric pressure and ambient temperature (cold plasma) using applied electric fields and spatial charge. In this evaluation, a cold plasma prototype device was employed where atmospheric air was exposed to high voltage current discharge in a confined chamber to create plasma

[0038] Plasma processing time is a critical parameter in the present application, influencing the efficiency and effectiveness of the treatment process. It refers to the duration for which materials or substrates are exposed to plasma. The optimal plasma processing time varies depending on the specific application and desired outcomes. The balance between adequate exposure and avoiding over-processing is crucial.

[0039] Plasma processing times vary according to the requirements of the feedstock and depend on the following parameters:1. Thickness and fineness of the digestate material exposed;2. Rate of movement of digestate through plasma chamber;3. Number of plasma rods; and4. Air flow through the bio-digester.

[0040] In another aspect of the present invention, a process for the treatment of medical waste is provided. The process of the present invention comprises the steps of shredding food and medical waste, transferring the waste to an aerobic biodigester and exposing the resulting waste products to plasma to generate non-hazardous compost. A set of experiments was performed to determine whether this process was sufficient to eliminate any harmful conditions from the waste.

[0041] It is also important to note that given the nature of the medical setting, plasma treatment for sterilisation is preferred so as to ensure that other types of site-specific organisms such as spore-based bacteria e.g. Giardia, cryptosporidia and ESKAPE pathogens are eliminated. The ESKAPE pathogen panel is comprised of representatives of several, clinically relevant, multi-drug resistant bacterial species, for instance, Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp. These spore-based hospital pathogens are more resistant to heat, however with the application of plasma, as the final step, ensures that the bio digestate is sterilised completely and therefore de-risked on-site to a pathogen safe bio digestate.

[0042] In addition, plasma has been shown to increase nitrogen composition of biodigestate and therefore increases the nutrient value of the end product. This gives added benefit to the end product.Specifications of cold plasma used in the present invention include:1. Temperature: <50°C2. Plasma discharge type: Cold atmospheric plasma, non-thermal plasma, or low- temperature plasma3. Forming gas: Atmospheric Air4. Voltage: 3-18 kV5. Frequency: 20-50 kHz6. Treatment time: 1 min,7. Distance between plasma and bio specimen: 15 mm

[0043] Viable ESKAPE pathogens were artificially seeded onto 2 cm2compostable PPE samples (compostable PPE in accordance with the Applicant’s medical grade compostable PPE) wherein the compostable bio-degradable breathable PPE meets the requirements of a Class 1 medical device as classified according to the Medical Device Regulation (Ell) 2017 / 745 (MDR). The ESKAPE-seeded compostable PPE samples were added into a compost and defined food waste mixture. Seeding of the compostable PPE samples was achieved by immersion in respective pathogen liquid cultures adjusted to a standardised loading of 106colony forming units / ml. Recovery of microbes from the composter was performed via serial dilution and plating of 10'1dilutions onto respective selective agar for enteric bacteria, Pseudomonas and Staphylococcus, respectively. Potential for fungi and yeast presence / survival was also evaluation on appropriate solid media.

[0044] Optimisation of the plasma process to eliminate the tested pathogens was achieved as follows:

[0045] 1mm depth of digestate material that was created by initial physical, enzymatic and thermophilic (72 °C) application was followed by 1 minute of cold plasma air exposure.

[0046] The plasma flow was achieved by two 12 cm rods placed in grid-like stainless steel protective casing.

[0047] The depth thickness was achieved by the addition of an adjustable lever that flattened the material to the optimal depth at the entrance of the final chamber where the plasma rods were positioned.Advantages of the present invention

[0048] Enhanced Waste Treatment: Combining bio-digestion and plasma sterilization ensures both effective breakdown of organic material and thorough pathogen elimination.

[0049] Safety: The system produces waste that is safe for disposal or reuse, reducing environmental and health risks.

[0050] Efficiency: The integration of bio-digestion and plasma sterilization maximizes the efficiency of waste treatment processes without compromising the efficiency of the bacterial breakdown of food waste and biofilms introduced earlier in the process.

[0051] Input waste material is reduced by 100%, mass by 70% with average fertiliser / soil enhancer yield of 30%.BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present invention will now be described with reference to the accompanying drawings in which are shown, by way of example only, a number of embodiments of the present invention.Figure 1 is a summary overview of the test methodology for evaluation of single compost cycle (24hr) impact on viability / recovery of ESKAPE pathogens;Figure 2 is a Heterotrophic (non-selective) microbial cultivation of compost samples to evaluate background load in the presence and absence of food waste;Figure 3 shows the outcome of selective media incorporation;Figure 4 shows the cold plasma prototype system; (Inset: close-up of agar culture plate in proximity to discharge tube);Figure 5 shows an overview of the Cold plasma ESKAPE inhibition test methods A and B;Figure 6 shows the impact of plasma exposure on the survival of ESKAPE pathogens on growth media;Figure 7 shows the variable Log reduction of ESKAPE pathogens seeded into sterile compost after 30 minutes exposure to cold plasma;Figure 8A shows E. faecium recovery on selective media from compost samples at TO, T10 and T20 of cold plasma exposure; the bottom set of plates reflect isolations from a compost sample that was inverted at after T10 to allow the lower layer to be exposed;Figure 8B shows respective counts (cfu / ml) of recoverable E. faecium on selective agar from non-inverted and inverted compost samples;Figure 9 is a schematic flow diagram showing an overview of the process steps of the process of the present invention; andFigure 10 is a schematic diagram showing an overview of the bio-digester apparatus in accordance with the present invention.DETAILED DESCRIPTION

[0053] Figure 1 shows an overview of the methodology used for evaluation of a single composting cycle (24hr) impact on the viability and recovery of ESKAPE pathogens. The parameters affecting the performance of the waste treatment process and system combining bio-digestion and plasma sterilization in accordance the present application, were evaluated using this test methodology. Heterotrophic background growth was evaluated in the compost and compost and food waste samples to gauge overall loads and profiles at both 37 °C and 55 °C.

[0054] As shown in Figure 2, extensive growth was observed under the conditions tested with a phenotypic profile typical of Bacillus species (common in composting systems). The addition of food waste did contribute a modest increase in the overall recoverable community load but did not significantly alter the observed phenotypic profile of isolates.

[0055] The outcome of selective media incorporation is presented in Figure 3. This figure shows the results of isolation with selective media in the presence / absence of ESKAPE pathogen contaminated PPE. Respective selective media are listed on the left-hand side of Figure 3, while corresponding target organisms are identified in coloured boxes on the right hand side. ‘C’ = compost alone, ‘+FW = compost & food waste, ‘+ESKAPE+FW+PPE’ = compost & food waste with ESKAPE seeded PPE samples. TO and T24 refer to time of sampling of the composter cycle. In summary, Figure 3 shows that representative enteric bacteria were unable to be recovered following 24-hour exposure to composting conditions, despite strong recovery of same at TO following addition of contaminated PPE samples. Similar findings were observed in relation to Pseudomonas contaminated PPE, with no recovery of viable cells after 24 hours. Yeast and mould selective media did not identify the presence of any representative species in any of the controls or test samples. An increase in isolate recovery on the Barid Parker agar was noted when TO and T24 samples with ESKAPE pathogens were compared. However, the Staphylococcus selective media yielded isolates on all control and test samples, with increased recovery associated with food waste incorporation in the controls without ESKAPE seeded PPE. This may reflect an abundance of other, non-pathogenic Staphylococci associated with both the compost and food waste (e.g. Staphylococcus saprophyticus). This is supported by the phenotype of the majority of isolates, (grey, opaque) which is not indicative of S. aureus (black, distinct), the latter being the experimentally seeded pathogenic representative. Thus, clinically relevant S. aureus strain survival may be inhibited, while other more robust environmental species are being recovered on the selective media.

[0056] Figure 4 provides a visual overview of the plasma chamber prototype. As previously discussed, plasma technology is rapidly becoming an established green technology in both the medical and food sectors in surface disinfection applications for the inactivation of vegetative cells, spores, oocysts, enzymes and toxins. Plasma is comprised of ionized, partially ionized and neutral particles referred to as reactive species, which interact disruptively with cellular structures and / or extracellular bio-products (e.g. enzymes, toxins). Plasma can be generated under high temperature and pressures (thermal plasma) or under atmospheric pressure and ambient temperature (cold plasma) using applied electric fields and spatial charge. In this evaluation, a cold plasma prototype device was employed where atmospheric air was exposed to high voltage current discharge in a confined chamber tocreate plasma. ESKAPE microbial cultures on agar plates were enclosed within the plasma chamber for varying periods of time to evaluate the log reduction / inactivation capacity of the system for each pathogen.

[0057] Turning now to Figure 5, an overview of the Cold plasma ESKAPE inhibition test methods A and B is shown and the method A and method B procedures for testing will be described further hereinbelow:Method A

[0058] ESKAPE cultures were grown overnight, diluted to 106cfu / ml suspensions and 0.1ml spread plated onto respective agars. Cultures were exposed to cold plasma for varying timed increments (TO - T30), incubated overnight at 37 °C and enumerated to evaluate respective log reductions.Method B

[0059] Commercially available compost was sterilized, homogenized in a blender to ensure particulate consistency and seeded with ESKAPE pathogens before being added to petri dish container (no media). Seeded compost was exposed to cold plasma for varying increments and 1 gm samples taken, re-suspended in buffer and plated onto respective, selective agars. Incubation and enumeration were conducted in accordance with the above described procedure of method A.

[0060] Figure 6 shows that plasma exposure of >15 minutes was sufficient to achieve nonviability for all representative ESKAPE pathogens tested (A-D). Reduction of the exposure time to 5 minutes retained the total bactericidal impacts on S. aureus (A) and E. faecium (B). Single viable colonies were recovered for P. aeruginosa and K. pneumoniae, indicating a 1.4 log reduction. It is known that both K. pneumoniae and P. aeruginosa can produce polymeric, extracellular matrices with protective capacities, such that >5min plasm exposure times were required for fully bactericidal impacts. In addition, it is noted that the experimental bacterial load trialled, (20 ul x 106cfu / ml), was intentionally high and far in excess of any anticipated cross contamination of hospital food waste likely to be encountered in the proposed application setting. The effect of intermixing ESKAPE pathogens with compost was also examined. As it was previously established that the compost harboured a native Staphylococcal source, all compost samples used for testing in the Examples were sterilized via autoclaving prior to ESKAPE seeding. Exposure was conducted by filling petri dishes with ESKAPE - seeded compost and exposing to cold plasma as previously described. The upper and lower layers of the samples were sequentially exposed to plasma in order to gauge the penetrative scope of the cold plasma when applied to compost. It was also previously established that >15 min plasma exposure was sufficient to achieve completeinactivation of the ESKAPE pathogens with an average 9.36 log reduction under the conditions tested.

[0061] Figure 7 shows the significant reduction in log reduction observed for each pathogen even after 30 minute exposures. The Results indicate that microbial exposure to plasma is mitigated by physicochemical aspects of the compost medium. To demonstrate that agitation of the compost improves penetration of cold plasma and enhances the bactericidal impact of exposure to the sterilisation process by plasma, seeded compost samples were inverted after 10 minutes of exposure to plasma, of the upper surface layer surface of the compost so as to facilitate exposure of the lower surface layer of the compost to plasma for an added 10 minutes. Control plates were exposed to sterilisation by plasma for a similar overall time (20 minutes) but were not inverted, and culture recovery compared for both conditions.

[0062] Figure 8 (A) shows an example of the observed variance in recoverable colonies in the inverted and non-inverted test samples, conducted with E. faecium seeded compost. It is evident from the T20 plates that simple inversion improved the bactericidal impact.

[0063] Figure 8 (B) provides comparative counts of recovered colonies on selective agar and indicates that inversion contributed to a 48% overall reduction in recoverable culture (cfu / ml) compared to only 26.3% reduction in the non-inverted sample, while that inversion resulted in further reduction of viable cells in the compost mix. The non-inverted control had a log reduction of 0.132 while the inverted sample had a 3-fold higher log reduction of 0.304. This increase in log reduction following inversion is indicative of a lack of penetration of the cold plasma through the surface of the compost.

[0064] Figure 9 is a schematic diagram of the process steps of the present invention;

[0065] Figure 10 is a schematic diagram of a biodigester apparatus comprising plasma rods for delivery of plasma in accordance with the present invention; ;

[0066] With respect to the evaluation of composting, it was clear that a significant, selective pressure was applied to pathogenic bacteria, which resulted in non-recovery / viability of the majority of the ESKAPE pathogens tested. The case for Staphylococcus aureus inhibition remains inconclusive as the likely isolation of native Staphylococci obfuscated the selective agar results. However, composting conditions in accordance with the process of the present invention, within the system and biodigester apparatus have demonstrated an excellent capacity to mitigate against the risk of viable clinical pathogen surviving the treatment process of the present invention.

[0067] Cold plasma application, under the conditions and equipment tested, was also found to be highly impactful with respect to bactericidal impacts on clinically relevant isolates of the ESKAPE pathogen panel.

[0068] Exposure times of >5 mins were found to be highly effective and achieved excellent microbial culture reductions under high culture density loadings when applied to pure cultures growing on solid media surfaces. Thus, the capacity of cold plasma to cause inactivation of clinically relevant microbes was clearly established. However, compost soil was found to impart some protective barrier effect against the bactericidal effects of cold plasma when delivered to static samples seeded with pathogen representatives. Similar findings have previously been reported in relation to cold plasma application in the disinfection of consumer foods, which can be affected by the structural nature of the target food, impeding penetration by plasma radicals. Inversion of the compost, to mimic the most basic agitation of compost and increased surface exposure was found to mitigate against some of this protective effect and to dramatically increase the bactericidal impact of cold plasma. Thus, the process preferably, comprises the step of agitating by mechanical agitation means, such as by an auger for instance, or by paddles or by providing baffles in the apparatus, in conjunction with the step of sterilisation by exposure to cold plasma.

[0069] Finally, the inventors point out that the tests carried out in the Examples employ high microbial loadings that would not be typically expected to arise in hospital food waste in practice. As such, the reductions achieved in recoverable pathogenic bacteria by treatment in the biodigestion process of the present invention and creating soil-friendly compost using the process of the present invention demonstrate a high-performance capacity system and process for the mitigation of pathogen transmission risks and enabling the safe, sustainable management of food hospital waste.

[0070] The system for waste treatment system combining bio-digestion and plasma sterilization comprises the following components:Bio-Digester apparatus:

[0071] A chamber or series of chambers where organic waste is broken down by bacteria under closed vessel, aerobic conditions. The bio-digester produces, water condensate and a digestate as by-products of the bacterial breakdown of organic material. This bio-digester does not release carbon into the atmosphere as no methane is produced during the closed vessel, aerobic digestion process. Carbon is stored in the digestate which is then returned to the ground through the product. The bio-digester consists of a sealed tank designed to maintain a closed vessel but with an air inlet to maintain aerobicconditions. Waste is introduced into the bio-digester through the inbuilt shredder inlet, and water condensate is collected from an outlet at the bottom of the tank. Digestate is periodically removed from the bottom of the tank for further processing or disposal.Bacteria

[0072] Bacteria capable of degrading various organic wastes. These bacteria metabolize the organic material, producing a nutrient rich-digestate while any carbon dioxide is captured in a carbon filter. This means that the process is performed without the side effect of carbon dioxide, ammonia, or methane emissions, and thus resulting in an innovative, carbon negative, organic waste remediation technology. The bacterial consortium is selected based on its ability to efficiently degrade the specific types of organic waste and compostable PPE bio-films being processed. The bacteria are maintained in optimal conditions within the bio-digester to maximize the rate of organic matter breakdown.Plasma Device

[0073] A plasma generation unit that produces plasma using a high-voltage electrical discharge. The plasma device is configured to deliver plasma to the waste material, effectively sterilizing it by destroying pathogens. The plasma device includes electrodes and a power supply to generate high-voltage electrical discharges but with low amp power consumption. Plasma is directed onto the digestate at the end of the process and outside the main chamber so the ‘helpful’ enzymes and bacteria at the early stage of the degradation process are not disrupted from functioning. The end chamber tunnel is designed to maximize the exposure of the waste to the plasma, ensuring thorough sterilization.System Integration

[0074] The system integrates the bio-digester and plasma device in a sequential or parallel configuration. Waste is initially introduced into the bio-digester, where it undergoes closed vessel, aerobic digestion by the bacterial consortium. Any carbon dioxide produced during digestion is collected using an inbuilt filter. Digestate exiting the bio-digester is transferred to the plasma treatment tunnel. The plasma device generates plasma that sterilizes the digestate, eliminating remaining pathogens and rendering the digestate safe for removal and use as fertilizer or as a pre-processed feedstock for biogas.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0075] The invention will now be more particularly described with reference to the following Examples which are provided by way of example only.

[0076] Referring to Figures 9 and 10, in a preferred embodiment, the waste treatment system is indicated generally by reference numeral 200 and comprises a biodigester adapted for enabling bio-digestion process to proceed in the biodigester and adapted to deliver sterilization by sterilisation means, preferably comprising plasma, and most preferably, delivered by plasma rods indicated generally by reference numerals 210, 212. The biodigester, also comprise at least one inlet 201 and at least one outlet. In alternative embodiments, there may be provided, a plurality of inlets and outlets for respective feed streams into and out of the biodigester apparatus.

[0077] As shown in Figure 9, the feed stream F1 comprises food waste and the feed stream F2 comprises compostable PPE from a healthcare setting such as a hospital or nursing home. The feed stream F1 and the feed stream F2 are preferably weighted at respective weighing stations W1 and W2 so as to determine the relative proportions of incoming feed stream F1 and Feed stream F2.

[0078] A pre-treatment step S1 is indicated generally in Figure 9. The pre-treatment step preferably comprises cutting or shredding of the incoming waste streams using a shredder apparatus (not shown) so as to prepare the waste for optimisation of the bio-digestion process step S2 in the biodigester. The shredder is preferably, positioned so that the shredding of the feed stream of waste is carried out prior to the introduction of the waste stream or streams into the biodigester. The shredder of the present application may be an industrial fine-tooth mini shredder with shearing action, and may also comprise a fully sealed body housing with 2-3 / 4" hardened hex shafting, mechanical seals and direct inline. The shredder may further comprise a high torque gear drive, mechanical shaft seals, precision ground gears, hardened and ground cutters and high strength housing.

[0079] The biodigester comprises one or more chambers or series of chambers where organic waste is broken down by bacteria under closed vessel, aerobic conditions. In some embodiments, the bio-digester comprises a sealed tank designed to maintain a closed vessel but with an air inlet to maintain aerobic conditions. Air is drawn in from outside the chamber through a one-way valve system. Waste is introduced into the bio-digester through an inbuilt shredder inlet, and water condensate is collected from an outlet at the bottom of the tank. Digestate is periodically removed from the bottom of the tank for further processing or disposal.

[0080] The bacteria are capable of degrading various organic wastes. The bacteria preferably, comprise saprotrophic organisms such as soil dwelling fungi, moulds and bacteria, otherwise known as saprotrophs, a type of decomposer which feeds exclusively on decaying matter. These bacteria metabolize the organic material, producing a nutrient richdigestate while any carbon dioxide is captured in a carbon filter. The bacterial consortium isselected based on its ability to efficiently degrade the specific types of organic waste and compostable PPE bio-films being processed. The bacteria are maintained in optimal conditions within the bio-digester to maximize the rate of organic matter breakdown. The specific conditions that support the growth and activity of thermophilic bacteria in the bio- digestor of the present invention include A multi-enzyme blend to break-down proteins, carbohydrates and celluloses. This blend consists of amylase, proteases and cellulases.

[0081] During hydrolysis, complex polymers like carbohydrates, proteins and fats are degraded into sugars, amino acids and long chain fatty acids respectively. This breaking down process occurs primarily through the activity of extracellular enzymes (lipases, proteases, cellulases and amylases) secreted by hydrolytic bacteria.

[0082] The temperature in the biodigester is kept between 45°C (113°F) and 80°C (176°F) and preferably under 72°C. The pH levels within the biodigester range from neutral (pH 7) to slightly acidic or alkaline (pH 6 to 8). The environment within the biodigester is preferably of high humidity or moisture content.

[0083] The system integrates the bio-digester and plasma device in a sequential or parallel configuration. Waste is first treated in the bio-digester, where bacteria break down the organic material. The partially treated waste is exposed to plasma from the plasma device, ensuring the destruction of any remaining pathogens.

[0084] The plasma device includes electrodes and a power supply to generate high- voltage electrical discharges but with low amp power consumption. Plasma can be generated under high temperature and pressures (thermal plasma) or under atmospheric pressure and ambient temperature (cold plasma) using applied electric fields and spatial charge. In this evaluation, a cold plasma prototype device was employed where atmospheric air was exposed to high voltage current discharge in a confined chamber to create plasma.

[0085] The temperature of the plasma was kept to below 50°C, and the plasma discharge type was cold atmospheric plasma, non-thermal plasma, or low-temperature plasma. The plasma was formed from atmospheric air with a voltage between 3-18 kV and a frequency of between 20-50 kHz.

[0086] In some embodiments, 1 mm thick film of digestate material which was created by initial physical, enzymatic and thermophilic (72 °C) application was followed by 1 minute of cold plasma air exposure with the distance between the plasma and bio specimens being 15 mm. Plasma flow was achieved by two 12 cm rods placed in grid-like stainless steel protective casing. The depth thickness of the digestate was achieved by the addition of an adjustable lever that flattened the material to the optimal depth at the entrance of the final chamber where the plasma rods were positioned.

[0087] Below in Table 1 are shown further example parameters tested for plasma treatment, with varying depth thickness for digestate material, temperature and plasma exposure time. The data shows that the bacterial load following the plasma treatments were all zero, indicating the ability of plasma treatment to neutralise harmful pathogens.Table 1 : Example parameters tested for bacterial load after waste treatment process including sterilisation using plasma

[0088] Further Example and discussion on process and system operation at Hospital site

[0089] A successful Proof-of-Concept (PoC) deployment of the process and system in accordance with the present invention was carried out at a functioning hospital. This deployment at a hospital site allowed for integrating compostable medical consumables together with food waste from the hospital an on-site CX3 biodigester, enabling real-time monitoring of waste diversion, carbon savings, and cost performance. The hospital produces an estimated 7.7 kg of waste per in-patient bed day, with food waste and single-use plastics forming a substantial proportion. As discussed above, traditional disposal methods — including landfill and incineration — are both costly and environmentally damaging, and the present invention has demonstrated an advantageous technical solution to these problems.

[0090] Methodology & Setup

[0091] The Proof-of-Concept (PoC) at the hospital enabled the evaluation of the process and system of the present invention in a functioning hospital environment. Themethodology combined technical system deployment, structured training, and systematic data collection over a three-month pilot period (April-June 2025).

[0092] System Description

[0093] Bio-digester Unit: A CX3 thermophilic biodigester with 3,000 L weekly processing capacity was installed on-site. The unit operated at >70°C, ensuring rapid decomposition of food waste and certified compostable PPE into a stable, pathogen-free output suitable for use as fertiliser.

[0094] Ancillary Equipment: The installation also included a hopper, shredder, and bin lift to enable safe handling of 140 L food waste bins and to minimise manual handling risks.

[0095] In this example, the biodigester was integrated with a cloud-based monitoring system via 4G SIM or CAT-5 Ethernet connection, providing real-time tracking of waste input, output, CO2offset, and operational parameters.

[0096] Summary results

[0097] The Proof-of-Concept (PoC) consistently met or exceeded all KPI targets, demonstrating the effectiveness and scalability of the process and system of the present invention.

[0098] Operational performance exceeded expectations, with throughput consistently surpassing baseline waste volumes and uptime above 95%.

[0099] Environmental outcomes were particularly strong, with over 11.8 tonnes of CO2avoided annually (exceeding the 10-tonne target) and food waste diversion increasing by -90% compared to the baseline, well above the 30% target.

[0100] Staff engagement results were highly positive, with >96% user satisfaction reported (vs. 80% target), full training completion, and no safety incidents.

[0101] User Satisfaction: Staff reported high satisfaction with the system, exceeding the KPI target (>96% positive).

[0102] Bin Lift directly to the biodigester: Eliminated manual lifting and reduced spillage of food waste;

[0103] Odour and Hygiene: Staff noted the absence of smell, no vermin presence, and improved hygiene around waste handling. Ease of handling of waste was also a notable advantage;

[0104] Improved Segregation: Catering staff increased accuracy in food waste segregation after receiving feedback on fertiliser quality, supported by improved communication between catering and facilities teams;

[0105] Waste Stream Optimisation: Better segregation has knock-on benefits beyond food waste. By reducing contamination, the system helps lower volumes of expensive high-risk or clinical waste and increases the proportion of recyclable material correctly diverted to low-cost streams; and

[0106] Excellent quality of output fertilizer from the process and system of the present invention.

[0107] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0108] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1. A process for producing compostable medical waste, wherein the medical waste stream comprises compostable Personal Protection Equipment (PPE); characterized by the process comprising the following steps: subjecting a medical waste stream to a combination of physical, thermal, enzymatic, and bacterial processes to convert the medical waste into compostable material; further comprising a step of sterilizing the compostable medical waste stream using a plasma device, the plasma device being adapted and configured to deliver plasma for sterilization of the medical waste; and whereby the process provides treatment of multiple waste feedstock streams, including the compostable medical waste stream, and converts the compostable medical waste into bio-digestate; and preferably, wherein the compostable biodegradable breathable PPE meets the requirements of a Class 1 medical device as classified according to the Medical Device Regulation (EU) 2017 / 745 (MDR).

2. A process as claimed in claim 1 wherein the PPE is compostable according to the definition set out in EU standard EN 13432 and ASTM 6400, that is, that the biologically based material (plant based material e.g. starch-based material) meets the following characteristics: Degradation of the material by at least 90% in 6 months when subjected to an environment rich in carbon dioxide.

3. The process of claim 1 , wherein the plasma device delivers non-thermal plasma for the sterilization of the compostable medical waste.

4. The process of claim 1 , wherein the physical process includes shredding or grinding of the medical waste stream before thermal, enzymatic, and bacterial treatment.

5. The process of claim 1 , wherein the thermal process is carried out at temperatures between 50°C and 90°C to facilitate enzymatic and bacterial breakdown of the medical waste.

6. The process of claim 1 , wherein the enzymatic process involves the use of specific enzymes to break down organic components of the compostable PPE.

7. The process of claim 1 , wherein the bacterial process involves the use of anaerobic bacteria to convert the medical waste into bio-digestate.

8. The process of claim 1 , wherein the bio-digestate provides a soil-friendly compostable product.

9. The process of any of claims 1-7 wherein the temperature is maintained at a temperature between 45°C (113°F) and 80°C (176°F).

10. The process of claim 8 wherein the temperature is maintained under 72°C.

11. The process of any of the preceding claims wherein the pH is maintained in the range from neutral (pH 7) to slightly acidic or alkaline (pH 6 to 8).

12. The process according to any preceding claim wherein the environment within the biodigester is preferably of high humidity or high moisture content.

13. A system for treating waste using the process as claimed in claim 1, comprising: a bio-digester containing bacteria for breaking down organic waste; a plasma device for delivering plasma to sterilize the waste; and means for integrating the bio-digester and plasma device to sequentially or simultaneously treat the waste.

14. The system of claim 13, wherein the bio-digester is configured to maintain closed but still aerobic conditions for bacterial digestion.

15. The system of claim 13, wherein the plasma device includes a plasma generation unit with electrodes and a power supply.

16. The system of claim 13, further comprising a treatment chamber for exposing waste to plasma generated by the plasma device.

17. The system of claim 13, wherein the bacteria in the bio-digester are selected for their ability to degrade specific types of organic waste.

18. The system of claim 13 wherein the bacteria comprise saprotrophic organisms such as soil dwelling fungi, moulds and bacteria, otherwise known as saprotrophs, a type of decomposer which feeds exclusively on decaying matter.

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