METHOD FOR SANITIZING WASTE

Abstract

The present invention relates to a method for sanitizing waste, where waste having specific bacterial counts are subjected to an enzyme composition at a pH between 30 and 6.0 and at a temperature of between 40 C. and 60 C., the liquid is separated and the waste is subjected to the enzyme composition for a period of 10 to 30 hours to obtain at least partial reduction in bacterial count.

Claims

1. Method for sanitizing waste, the method comprising: a) Subjecting waste comprising biodegradable material and non-biodegradable material and having a total bacterial count of at least 2.510.sup.8 CFU/gram waste, a bacterial count of E. coli of at least 1.510.sup.6 CFU/gram waste or a bacterial count of Enterobacteriaceae of at least 1.510.sup.8 CFU/gram waste, to enzymatic and/or microbial treatment in a bioreactor at a pH between 3.0 and 6.0 and at a temperature of between 40 C. and 60 C. for a period of 10 to 30 hours to obtain at least partial reduction in bacterial count.

2. Method according to claim 1 further comprising: b) subjecting the treated waste from step a) to one or more separation step(s), whereby a bioliquid and a solid fraction is provided; c) subjecting said bioliquid and/or solid fraction to downstream processing.

3. Method according to any of the preceding claims, wherein the waste has a dry-matter content in in the range of 50-70% wt.

4. Method according to any of the preceding claims, wherein the waste under step a) is subjected to water to reduce the dry matter content of the waste.

5. Method according to any of the preceding claims, wherein the waste is subjected to enzymatic and/or microbial treatment in a bioreactor for a period of about 20-25 hours, preferably about 18 hours.

6. Method according to any of the preceding claims, wherein the pH in step a) is below 6.0, preferably below 5.0, more preferably below 4.5, even more preferably below 4.4 and most preferably below 4.2.

7. Method according to any of the preceding claims, wherein the temperature in step a) is 55 C. or below, the temperature is 50 C. or below or the temperature is 45 C. or below.

8. Method according to any of the preceding claims, wherein the waste is subjected to enzymatic and/or microbial treatment in a bioreactor in step a) for 24 hours and the pH is 4-6 and the temperature is in the range of 40-60 C.

9. Bioliquid obtainable by the method of claims 1-8.

10. The bioliquid according to claim 9, where the bioliquid has a bacterial count for Enterobacteriaceae below 110 2-110 4 CFU/ml as measured by Assay III, preferably below 110.sup.2 CFU/ml and/or, where the bioliquid has a bacterial count for E. coli below 20-100 CFU/ml as measured by Assay IV, preferably below 20 CFU/ml and more preferably below 10 CFU/ml.

11. The bioliquid according to any of claims 9-10, where the bioliquid has a bacterial count for Lactic Acid Bacteria of at least 110.sup.5 CFU/ml as measured by Assay II, preferably at least 110.sup.6 CFU/ml.

12. Non-biodegradable waste material obtainable from the method of claims 1-8.

13. The non-biodegradable waste material according to claim 12, where the material has a bacterial count for Enterobacteriaceae below 110.sup.2-110.sup.4 CFU/ml as measured by Assay IV, preferably below 110.sup.2 CFU/ml.

14. The non-biodegradable waste material according to any of claims 12-13, where the material has a bacterial count for E. coli below 20-100 CFU/ml as measured by Assay II, preferably below 20 CFU/ml and more preferably below 10 CFU/ml.

15. The non-biodegradable waste material according to any of claims 12-14, where the material has a bacterial count for Lactic Acid Bacteria of at least 110.sup.5 CFU/ml as measured by Assay III, preferably at least 110.sup.6 CFU/ml.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0111] FIG. 1 is a schematic overview of an example of a waste process comprising a bioreactor wherein the self-sanitizing enzymatic and microbial treatment takes place

[0112] FIG. 2 shows bacterial counts on metal from Mechanical Biological Treatment (MBT) (black bars) and from the process of the invention (grey bars).

[0113] FIG. 3 shows bacterial count for Refused Derived Fuel (RDF) from Mechanical Biological Treatment (MBT) (black bars) and from the process of the invention (grey bars).

[0114] FIG. 4 shows a contour plot showing the negative logarithm with base 10 of relative reduction of CFU counts after 24 h (relative to 0 h). The black points show the experimentally tested conditions and a digit next to the points shows the number of replicates performed for a specific combination of pH and temperature. If no digit is shown next to a point, then this combination of pH and temperature was tested only once. Each contour line shows the 10.sup.n (where n is a number in a box crossed by the contour) times reduction of relative CFU counts after 24 h according to a model: (log.sub.10(relative reduction of CFU counts)).sup.0.59=9.26150.9346pH+0.00274T.sup.2

DETAILED DESCRIPTION OF THE INVENTION

[0115] The present invention pertains to a method for sanitizing waste, the method comprising: [0116] a) Subjecting waste comprising biodegradable material and non-biodegradable material and having a total bacterial count of at least 2.510.sup.8 CFU/gram waste, a bacterial count of E. coli of at least 1.510.sup.6 CFU/gram waste or a bacterial count of Enterobacteriaceae of at least 1.510.sup.8 CFU/gram waste, to enzymatic and/or microbial treatment in a bioreactor at a pH between 3.0 and 6.0 and at a temperature of between 40 C. and 60 C. for a period of 10 to 30 hours to obtain at least partial reduction in bacterial count.

[0117] The method may further comprise the pre-step: [0118] a) Removal of large items, shredding and/or pulping.

[0119] The method may further comprise the subsequent steps: [0120] b) subjecting the treated waste from step a) to one or more separation step(s), whereby a bioliquid and a solid fraction is provided; [0121] c) subjecting said bioliquid and/or solid fraction to downstream processing

[0122] Downstream processing could be any process involving the solid or the liquid fraction of the waste obtained from step b) which takes place downstream of the enzymatic and/or microbial treatment in the bioreactor in step a). Examples of downstream processes are washing processes, evaporation processes, collection of bioliquid or part of the bioliquid obtained in step b) and anaerobic digestion. Downstream process also includes processes wherein the solid and/or liquid fraction of the waste obtained from step b) is converted into biogas, which can be combusted to generate electricity and/or heat, and processes wherein the solid and/or liquid fraction of the waste obtained from step b) is converted into renewable natural, biomethane gas and/or transportation fuels.

[0123] The inventors have surprisingly found that when reacting a waste fraction with a specific content of natural occurring bacteria and enzyme at low temperatures (40 C.-60 C.), the resulting bioliquid and non-biodegradable waste material has very low numbers of pathogenic bacteria. As a result, the bioliquid, the waste and the equipment used in waste treatment do not expose the environment, e.g. the workers, to undesired bacteria.

[0124] Low temperatures during reaction with enzymes are advantageous as fuel for heating the waste fraction to high temperatures, e.g. 75 C., is saved. Considerable savings are available when waste fractions are reacted with enzymes for about 10 to 30 hours. A further advantage is that handling a process at low temperature is easier than handling a process performed at high temperatures.

[0125] The inventors have found that even when reacting the waste at low temperatures with enzymes, the resulting bioliquid and non-biodegradable waste material has very low numbers of bacteria, e.g. pathogenic bacteria. The number of bacteria present on the waste may be reduced to a bacterial count of E. coli of less than 20 CFU/gram waste and/or a bacterial count of Enterobacteriaceae of less than 10.sup.2 CFU/gram waste.

[0126] The inventive method for producing a bioliquid comprises under step a) subjecting waste comprising biodegradable and non-biodegradable material to enzymatic and/or microbial treatment. The waste comprises biodegradable material, which is organic material that can be hydrolysed by enzymes and/or microorganisms. The organic material may comprise carbohydrates, proteins, fat and mixtures thereof, which are organic matter that are typical present in household waste. The waste further comprises material that is not biodegradable, such as plastic or metal.

[0127] The waste can be unsorted. In an embodiment of the invention the unsorted waste comprises a mixture of biodegradable and non-biodegradable material in which 15% by weight or greater of the dry weight is non-biodegradable material.

[0128] In an embodiment of the invention, the waste comprises a mixture of biodegradable and non-biodegradable material in which at least 20% w/w is non-biodegradable material, based on the weight of the waste. In one embodiment, at least 25% of the waste is non-biodegradable material, at least 30% of the waste is non-biodegradable material, at least 35% of the waste is non-biodegradable material, at least 40% of the waste is non-biodegradable material, at least 45% of the waste is non-biodegradable material or at least 50% of the waste is non-biodegradable material.

[0129] The waste can be municipal solid waste (MSW), e.g. city waste or waste disposed from domestic household and public facilities. The waste comprises a natural microflora, which has a total bacterial count of at least 2.510.sup.8 CFU/gram waste, a bacterial count of E. coli of at least 1.510.sup.6 CFU/gram waste and/or a bacterial count of Enterobacteriaceae of at least 1.510.sup.8 CFU/gram waste. The natural microflora may comprise lactic acid bacteria, which may proliferate during the time period, where the waste is subjected to the enzyme composition. In a preferred embodiment of the invention the waste comprises a natural microflora, which has a total bacterial count of at least 3.010.sup.8 CFU/gram waste, a bacterial count of E. coli of at least 1.610.sup.6 CFU/gram waste and/or a bacterial count of Enterobacteriaceae of at least 1.910.sup.8 CFU/gram waste.

[0130] It was previously believed that, in order to produce bioliquid from waste, inoculation of bacteria to the waste fraction was necessary. The inventors have found that the bacteria naturally occurring in the waste fraction are enough to control the microflora during the reaction time, where the waste fraction is exposed to the enzyme composition. The Examples show that the numbers of Enterobacteriaceae and E. coli in the bioliquid are very low,

[0131] In one embodiment of the invention, the waste provided contain lactic acid bacteria. The waste may have a ratio between the lactic acid bacteria and the total bacterial count of at least 1:1, such as at least 1:1.5, at least 1:2, at least 1:3, at least 1:4, at least 1:5 or at least 1:10.

[0132] The waste fraction provided in the inventive method may have a dry matter content in the range of 10-90% w/w. The content of dry matter in the waste fraction can be measured by Assay VIII. In one embodiment of the invention, the waste fraction may have a dry matter content in the range of 30-80% w/w, preferably in the range of 50-70% w/w.

[0133] In one embodiment of the invention the waste fraction provided in the inventive method may have a dry matter content about 10% w/w, such as about 15% w/w, about 20% w/w, about 25% w/w, about 30% w/w, about 35% w/w, about 40% w/w, about 45% w/w, about 50% w/w, about 55% w/w, about 60% w/w, about 65% w/w, about 70% w/w, about 75% w/w, about 80% w/w, about 85% w/w or about 90% w/w.

[0134] In one embodiment of the inventive method, the waste treatment in step a) can be subjected to water. The dry matter content of the waste fraction can be measured according to Assay VIII. Depending on the dry matter content, water may be added to the waste fraction. For example, when the waste fraction provided is municipal solid waste (MSW) it may be convenient to subject the waste fraction to water in an amount of about 0.5 to about 3.0 kg water per kg MSW. In one embodiment of the invention, the waste fraction may be subjected to about 0.5 to about 2.5 kg water per kg MSW. In a preferred embodiment of the invention, the water fraction may be subjected to about 0.8 to about 1.8 kg water per kg MSW. As a result of adding water to the waste fraction, the dry matter content of the waste fraction including water is lower than the waster fraction before addition of water.

[0135] In a preferred embodiment of the invention, the waste fraction is subjected to water to obtain a water to waste ratio in the range of about 0.1:1 to 5:1, preferably in the range of 0.5:1 to 3:1, more preferably in the range of 1:1 to 2:1, even more preferably in the range of 1:1 to 1.5:1.

[0136] The method of the present invention comprises subjecting the waste to an enzyme composition in step a). The purpose of the enzyme composition is to treat the biodegradable material present on the waste fraction. The biodegradable material is thereby degraded to smaller fractions, e.g. by enzymes that can hydrolyse carbohydrates to sugar molecules.

[0137] Suitable enzyme compositions are well known in the art and are commercially available. A suitable enzyme composition is for instance a composition comprising a cellulolytic background composition (CBC) combined with one or more enzymes.

[0138] When added to the process the cellulolytic background composition (CBC) may comprise a commercial cellulolytic enzyme preparation. Examples of commercial cellulolytic enzyme preparations suitable for use in the method according to the present invention include but is not limited to, for example, CELLIC CTec (Novozymes A/S), CELLIC CTec2 (Novozymes A/S), CELLIC CTec3 (Novozymes A/S), CELLUCLAST (Novozymes A/S), NOVOZYM 188 (Novozymes A/S), SPEZYME CP (Genencor Int.), ACCELLERASE TRIO (DuPont), FILTRASE NL (DSM); METHAPLUS S/L 100 (DSM), ROHAMENT 7069 W (Rohm GmbH), or ALTERNAFUEL CMAX3 (Dyadic International, Inc.).

[0139] When the enzyme composition comprises further enzymatic activity apart from the activities present in the CBC, such enzyme activity may be added from individual sources or together as part of enzyme blends. Suitable blends include but are not limited to the commercially available enzyme compositions Cellulase PLUS, Xylanase PLUS, BrewZyme LP, FibreZyme G200 and NCE BG PLUS from Dyadic International (Jupiter, FL, USA) or Optimash BG from Genencor (Rochester, NY, USA).

[0140] The CBC may comprise the following enzymatic activities:

[0141] Cellobiohydrolase I:

[0142] Endo-1,4-beta-glucanase

[0143] Beta-glucosidase

[0144] Endo-1,4-beta-xylanase

[0145] Beta-xylosidase

[0146] Beta-L-arabinofuranosidase

[0147] Amyloglocosidase

[0148] Alpha-amylase

[0149] Acetyl xylan esterase

[0150] In a preferred embodiment, the activity of the CBC is in accordance with the activity of ACCELLERASE TRIO (Genencor Int.), Cellic CTec2 (Novozymes A/S) or Cellic CTec3 (Novozymes A/S).

[0151] The enzyme composition may comprise about 40-99% w/w of an enzyme having cellulolytic activity. In one embodiment, the enzyme composition comprises about 50-90% w/w of an enzyme having cellulolytic activity, such as about 60-80% w/w of an enzyme having cellulolytic activity or about 65-75% w/w of an enzyme having cellulolytic activity. The enzyme composition may comprise about 0-20% w/w of a protease, e.g. about 10% w/w of the enzyme composition. The enzyme composition may comprise about 0-30% w/w of a beta-glucanase, e.g. about 15% w/w of the enzyme composition. The enzyme composition may comprise about 0-10% w/w of a pectate-lyase, e.g. 5% w/w of the enzyme composition. The enzyme composition may comprise about 0-10% w/w of a mannanase or an amylase, e.g. about 5% w/w of the enzyme composition.

[0152] The waste may be subjected to the enzyme composition at a concentration of about 10-20 kg enzyme composition per tons of waste, preferably about 12-19 kg enzyme composition per tons of waste, more preferably about 14-17 kg enzyme composition per tons of waste. In a preferred embodiment, the waste may be subjected to the enzyme composition at a concentration of about 16 kg enzyme composition per tons of waste.

[0153] The process of the invention comprises in step a) subjecting the waste fraction to an enzyme composition and reacting at a pH between 3.0 and 6.0 and at a temperature of between 40 C. and 60 C. in order to obtain a bioliquid.

[0154] In one embodiment of the invention, the pH in step a) is below 6.0, preferably below 5.0, more preferably below 4.5, even more preferably below 4.4 and most preferably below 4.2. The pH may be in the range of 3.0-6.0, such as in the range of 3.0-5.8, such as in the range of 3.5, 4.0-5.5, in the range of 4.0-5.0, in the range of 4.0-4.5 or in the range of 4.0-4.4.

[0155] The temperature in step a) of the inventive method is 55 C. or below, the temperature is 50 C. or below or the temperature is 45 C. or below. In one embodiment of the invention, the temperature is in the range of 40-55 C., in the range of 40-50 C. or in the range of 40-45 C.

[0156] In one embodiment of the invention the pH in step a) is in the range of 3.0-6.0 and the temperature is in the range of 40-55 C. In a further embodiment, the pH is in the range of 4.0-5.8 and the temperature is in the range of 40-55 C. More preferably the pH is in the range of 4.0-5.5 and the temperature is in the range of 40-50 C. More preferably the pH is in the range of 4.0-5.0 and the temperature is in the range of 40-45 C.

[0157] In one embodiment of the invention, the waste is subjected to the enzyme composition for a period of 10-30 hours, preferably 20-25 hours and more preferably about 18 hours. [0158] In a preferred embodiment the invention pertains to a method for sanitizing waste, the method comprising: [0159] a) Subjecting waste comprising biodegradable material and non-biodegradable material and having a total bacterial count of at least 2.510.sup.8 CFU/gram waste, a bacterial count of E. coli of at least 1.510.sup.6 CFU/gram waste and/or a bacterial count of Enterobacteriaceae of at least 1.510.sup.8 CFU/gram waste, to enzymatic and/or microbial treatment in a bioreactor at a pH between 4.0 and and at a temperature of between 40 C. and 50 C. for a period of 18 to 25 hours to obtain at least partial reduction in bacterial count. [0160] In another preferred embodiment, the invention pertains to a method for sanitizing waste, the method comprising: [0161] a) Subjecting waste comprising biodegradable material and non-biodegradable material and having a total bacterial count of at least 2.510.sup.8 CFU/gram waste, a bacterial count of E. coli of at least 1.510.sup.6 CFU/gram waste and/or a bacterial count of Enterobacteriaceae of at least 1.510.sup.8 CFU/gram waste, to enzymatic and/or microbial treatment in a bioreactor at a pH between 4.0 and and at a temperature of between 40 C. and 50 C. for a period of 18 to 25 hours to obtain at least partial reduction in bacterial count. [0162] b) subjecting the treated waste from step a) to one or more separation step(s), whereby a bioliquid and a solid fraction is provided; [0163] c) subjecting said bioliquid and/or solid fraction to downstream processing

[0164] Low temperatures during reaction with enzymes are advantageous as fuel for heating the waste fraction to high temperatures, e.g. 75 C., is saved. Considerable savings are available when waste fractions are reacted with enzymes for about 10 to 30 hours. A further advantage is that the workers handling the inventive method are not exposed to high temperatures.

[0165] It was previously believed that waste fractions should be pre-treated at temperatures of 90-95 C. before being used for producing a bioliquid. The effect of the pre-treatment is a sterilization of the waste fraction, whereby undesired microorganism, e.g. pathogenic bacteria, were killed. WO2013/185778 teaches that pre-heating of waste is not necessary. The application shows that by addition of microorganisms (inoculation of EC12B) and enzymes to waste and allowing concurrent enzymatic treatment and microbial fermentation at temperatures of 45-75 C., a safe fermentation can be achieved.

[0166] The inventors of the present invention have surprisingly found that when reacting a waste fraction with a specific content of natural occurring bacteria and enzyme at low temperatures (40-60 C.), the resulting bioliquid and non-biodegradable waste material has very low numbers of bacteria recognized as excellent indicator bacteria: Enterobacteriaceae and E. coll. As a result, the bioliquid, the non-biodegradable material and the equipment used do not expose the environment to undesired bacteria, e.g. pathogens. Thus, a safer environment is achieved, especially for the workers handling the inventive method and workers sorting the waste after the waste is separated from the bioliquid.

[0167] Various foodborne viruses, blood viruses, and faecal-oral transmitted viruses may also be present in the waste, depending on the waste. However, the process conditions described in step a) and/or step c) of the current invention completely inactivates or reduces the viruses such as e.g. Corona viruses, Adenovirus, Herpes viruses, Measles, HIV, and Flu viruses to a non-harmful level during the processing. In one embodiment of the invention sanitization includes reduction or inactivation of virus.

[0168] The process of the invention further comprises a recovery of the bioliquid by separating the bioliquid from the non-biodegradable material. The bioliquid can be separated by one or more separation means such as one or more ballistic separator(s), sieve(s), washing drum(s), presses and/or hydraulic press(es). In one embodiment of the invention, the bioliquid is separated from the waste fraction by use of a ballistic separator.

[0169] The one or more separation means separate the bioliquid from the waste. The waste can comprise several types of non-biodegradable materials such as textiles and foils (2D) and cans and plastic bottles (3D).

[0170] The water used for rinsing the non-biodegradable waste can be recirculated, heated and subjected to the waste fraction under step a) of the inventive method.

[0171] Inert material which is sand, and glass is typically removed e.g. sieved from the bioliquid. Metals are typically removed from all waste fractions. The 2D fraction can further be separated into recyclables and/or residuals such as Solid Recovered Fuel (SRF), Refused Derived Fuel (RDF) and/or inerts. The 3D fraction can also be further separated into recyclables and/or residuals such as metals, 3D plastic and/or RDF.

[0172] In one embodiment of the invention, the bioliquid produced by the inventive method is processed into biofuel, e.g. biogas.

[0173] According to the Health Protection Agency (Guidelines for assessing the microbiological safety of ready-to-eat foods placed on the marked, Health Protection Agency, London, November 2009, https://webarchive.nationalarchives.gov.uk/20140714111812/http://www.hpa.org.uk/webc/HP AwebFile/HPAweb_C/1259151921557) the amount of Enterobacteriaceae in ready-to-eat food should be below 110.sup.2 CFU/ml in order to be satisfactory. An amount of Enterobacteriaceae of more than 110.sup.4 CFU/ml is unsatisfactory in ready-to-eat food, whereas an amount of 110.sup.2-110.sup.4 CFU/ml is borderline.

[0174] The Health Protection Agency recommend the bacterial count of E. coli to be below 20 CFU/ml in order to be satisfactory for ready-to-eat food. A bacterial count of E. coli in the range of 20-110.sup.2 CFU/ml is borderline and bacterial count of E. coli above 110.sup.2 is unsatisfactory in ready-to-eat food.

[0175] In a further aspect, the invention pertains to a bioliquid produced by inventive method. By the inventive method it is possible to produce a bioliquid, which satisfies the microbial requirements to ready-to-eat food products.

[0176] In one embodiment of the invention, the bioliquid produced comprises very low number of pathogenic bacteria, e.g. E. coli.

[0177] In one embodiment of the invention, the bioliquid has a bacterial count for Enterobacteriaceae below 110.sup.2-110.sup.4 CFU/ml as measured by Assay I, preferably below 110.sup.2 CFU/ml.

[0178] In one embodiment of the invention, the bioliquid has a bacterial count for E. coli below 20-100 CFU/ml as measured by Assay II, preferably below 20 CFU/ml and more preferably below 10 CFU/ml.

[0179] In one embodiment of the invention, the bioliquid has a bacterial count for Lactic Acid Bacteria of at least 110.sup.5 CFU/ml as measured by Assay III, preferably at least 110.sup.6 CFU/ml.

[0180] The invention further concerns non-biodegradable waste material obtainable from the inventive method. The non-biodegradable waste material can be 2D or 3D material, which may be cleaned after being separated from the bioliquid. In one embodiment of the invention, the non-biodegradable is 2D waste.

[0181] In one embodiment of the invention, the non-biodegradable waste material has a bacterial count for Enterobacteriaceae below 110.sup.2-110.sup.4 CFU/ml as measured by Assay IV, preferably below 110.sup.2 CFU/ml.

[0182] In one embodiment of the invention, the non-biodegradable waste material has a bacterial count for E. coli below 20-100 CFU/ml as measured by Assay II, preferably below 20 CFU/ml and more preferably below 10 CFU/ml.

[0183] In one embodiment of the invention, the non-biodegradable waste material has a bacterial count for Lactic Acid Bacteria of at least 110.sup.5 CFU/ml as measured by Assay III, preferably at least 110.sup.6 CFU/ml.

[0184] In one embodiment of the invention, the ratio between the bacterial count of lactic acid bacteria (CFU/ml) and the total bacteria count (CFU/ml) is at least 1:2 to 1:1.

[0185] In one aspect, the invention pertains to biogas produced from the bio liquid obtained by the inventive method.

[0186] FIG. 1 is a schematic overview of a waste process and is explained in more details below.

[0187] During this first stage, means to open plastic bags and adequate pulping or shredding of degradable components are typically provided (not shown in FIG. 1), preparing the waste to be a more homogeneous organic phase before addition of enzymes. In some cases, removal of initial fractions such as metal or other material can take place before the waste is placed in the bioreactor. In some cases, reduction of particle size distribution or upfront sorting of the material is performed. Water, enzymes, and/or microorganisms are added. The enzymatic liquefaction and/or saccharification and/or microbial fermentation is performed continuously at the optimal residence time, temperature and pH for enzyme and microbial performance. Through this enzymatic treatment and fermentation, the biogenic part of the MSW is liquefied and/or saccharified into a bioliquid comprising inter alia mono-, di- and/or oligosaccharides.

[0188] The method of the invention may sanitize waste, such as MSW, comprising objects of different size, in one embodiment of the invention the large solid objects are pre-sorted before the waste entrees the bioreactor. The method according to the invention are effective on objects of various particle size. In one embodiment the method according to the invention is applied to objects which have a maximum particle size of 600 mm, such as 500 mm, such as 400 mm, such as 300 mm, such as 200 mm, such as 100 mm, such as 80 mm, such as 70 mm, such as 60 mm or such as 50 mm.

[0189] In the separation step, the bioliquid is separated from the non-degradable fractions. The separation is typically performed by one or more separation means such as one or more ballistic separator(s), sieve(s), washing drum(s), presses and/or hydraulic press(es). The bioliquid can be cleaned and then be further processed into biogas in the biogas plant. The one or more separation means separate the waste, such as MSW, treated with enzyme and/or microbial action, into the bioliquid, a fraction of 2D materials, e.g. non-biodegradable materials, and a fraction of 3D materials, e.g., non-biodegradable materials. The 3D fraction (such as cans and plastic bottles) does not bind large amounts of bioliquid, so a single washing step is often enough to clean the 3D fraction. The 2D fraction (textiles and foils as examples) typically binds a significant amount of bioliquid. Therefore, the 2D fraction is typically pressed using e.g. a screw press, washed and pressed again to optimize the recovery of bioliquid and to obtain a cleaner and drier 2D fraction. Inert material which is sand, and glass is typically removed e.g. sieved from the bioliquid. Metals are typically removed from all mentioned fractions. The water used in one or more of the washing drums can be recirculated, heated and then used for heating of the waste during the first step. The 2D fraction can be further separated into recyclables and/or residuals such as SRF (Solid Recovered Fuel), RDF (Refused Derived Fuel) and/or inerts. The 3D fraction can also be further separated into recyclables and/or residuals such as metals, 3D plastic and/or RDF.

EXAMPLES

[0190] Assays

[0191] Assay I: Total Bacterial Count

[0192] 1 ml from each dilution of bioliquid was plated on petrifilm plates 3M Petrifilm Aerobic Count Plate for total bacterial count. Petrifilm plates were incubated for 48 hours at 30 C., after which colony forming units (CFU) were counted according to the manufacturer's instructions.

[0193] Assay II: Lactic Acid Bacterial Count

[0194] 1 ml from each dilution of bioliquid was plated on petrifilm plates 3M Petrifilm Lactic Acid Bacteria Count Plate for lactic acid bacterial count. Petrifilm plates were incubated for 48 hours at 37 C., after which colony forming units (CFU) were counted according to the manufacturer's instructions.

[0195] Assay III: Enterobacteriaceae Count

[0196] 1 ml from each dilution of bioliquid was plated on petrifilm plates 3M Petrifilm Enterobacteriaceae Count Plate for Enterobacteriaceae count. Petrifilm plates were incubated for 48 hours at 37 C., after which colony forming units (CFU) were counted according to the manufacturer's instructions.

[0197] Assay IV: Escherichia Colt Count

[0198] 1 ml from each dilution of bioliquid was plated on petrifilm plates 3M Petrifilm type E. coli and Coliform Count for Escherichia coli count. Petrifilm plates were incubated for 48 hours at 37 C., after which colony forming units (CFU) were counted according to the manufacturer's instructions.

[0199] Assay V: Aerobic Bacteria Count

[0200] The total amount of aerobic bacteria count was performed using Yeast Extract Agar (YEA). From each dilution of bioliquid, 1 ml of sample was plated onto an empty petri dish (1 petri dish per sample). Then molten YEA, cooled to approx. 47 C., was poured into the petri dish and mixed with the sample so there would be equal distribution of bacterial growth within the agar. Once the agar was set, the plates were then incubated at 30 C. for 72 hours after which CFU were counted.

[0201] Assay VI: Enterobacteriaceae Count

[0202] Enterobacteriaceae count was performed using Violet Red Bile Glucose Agar (VRBGA). From each dilution of bioliquid, 1 ml of sample was plated onto an empty petri dish (1 petri dish per sample). Then molten VRBGA, cooled to approx. 47 C., was poured into the petri dish and mixed with the sample so there would be equal distribution of bacterial growth within the agar. Once the agar was set an overlay of VRBGA was added too and the plates were then incubated at 37 C. for 24 hours after which CFU were counted.

[0203] Assay VII: E. coli Count

[0204] E. coli count was performed using Violet Red Bile Agar (VRBA). From each dilution of bioliquid, 1 ml of sample was plated onto an empty petri dish (1 petri dish per sample). Then molten VRBA, cooled to approx. 47 C., was poured into the petri dish and mixed with the sample so there would be equal distribution of bacterial growth within the agar. Once the agar was set an overlay of VRBA was added too and the plates were then incubated at 44 C. for 24 hours after which CFU were counted. All counted colonies had to undergo a confirmation process using MacConkey agar, YEA agar, an oxidase test, Lactose Peptone Water, and Tryptone Water (with Kovacs reagent).

[0205] Assay VIII: Dry Matter Content

[0206] The dry matter content of a waste can be determined by drying a sample at 60 C. for 48 hours. The weight of the sample before and after drying should be measured and can be used to calculate the dry matter content in percent by the following formula:

[0207] Sample weight after drying100=% dry matter in sample Sample weight before drying

Example 1

[0208] This example investigates the bacterial count of sorted output samples from the method according to the invention and compare this to the bacterial count of output samples from an MBT (Mechanical Biological Treatment) plant. The RDF (Refused Derived Fuel) fraction and the metal from the treatment according to the process of the invention was compared with RDF and metal obtained at an MBT facility in England.

[0209] The waste (MSW) subjected to the method according to the present invention had a dry matter content of 50-70%. The MSW was then transported into a bioreactor. Water was added to the MSW to obtain a slurry of waste and water having water to MSW ratio of 1.5-2 to 1. Cellic CTec3 (Novozymes A/S) in a concentration of 0.9-2.3% w/w (based on the weight of the MSW before addition of water) enzyme composition was added to the MSW slurry, which was then allowed to react for 24 hours at a temperature of between 40 C. and 60 C., a pH between 4.0 and 6.0.

[0210] The waste entering the MBT plant had a dry matter content of 50-70%. The MSW was sorted into RDF, metal and biodegradable material, before the biodegradable material was transported into a bioreactor.

[0211] RDF from both the process of the invention and the MBT facility was sampled and analyzed as follows: 5 individual and separate samples, obtained from various sites within an RDF outputs container were pooled and 1 g mixed with 9 ml sterile 0,9% NaCl. The mixture was vortexed and inverting for 1 minute creating dilution 10-1. The RDF sample was hereafter serial diluted 10.sup.8 times using sterile 0.9% NaCl. 1 ml from each dilution were plated on petrifilm plates according to Assay I, II, Ill and IV described above.

[0212] Metal from the process of the invention and the MBT facility, was sampled and analyzed as follows: [0213] A lid from a standard can (containing e.g. tuna or baked beans) with a size of 77 cm 2 was swabbed with 5 sterile swab sticks, followed by the sticks being placed in 1 ml of appropriate media. The 5 ml were then pooled, and serial diluted using sterile 0.9% NaCl H.sub.2O to 10.sup.8. 1 ml from each dilution was plated on petrifilm plates according to Assay I, II, Ill and IV described above.

[0214] Bacterial counts on a metal can lid obtained from the treatment method according to the invention (test 1) and on a metal can lid obtained from the MBT (test 2), respectively was compared. Test 3 and 4 investigate the bacterial counts on an RDF obtained from the treatment method according to the invention and on an RDF obtained from MBT, respectively. The results are shown in table 1 and discussed below.

TABLE-US-00001 TABLE 1 Total Lactic bacterial acid Temperature count bacteria Enterobacteriaceae E. coli Test C. pH (Assay I) (Assay II) (Assay III) (Assay IV) 1 39-48 4.0- 3.5 10.sup.5 1.78 10.sup.5 5.11 10.sup.2 <10 Invention 4.5 CFU/lid CFU/lid CFU/lid CFU/lid metal 2 39-48 4.0- 2.21 10.sup.7 1.25 10.sup.5 4.1 10.sup.5 2.1 10.sup.4 MBT 4.5 CFU/lid CFU/lid CFU/lid CFU/lid metal 3 39-48 4.0- 2.59 10.sup.7 3.37 10.sup.6 4.88 10.sup.2 0 Invention 4.5 CFU/g CFU/g CFU/g RDF CFU/g RDF RDF RDF RDF 4 39-48 4.0- 7.46 10.sup.7 1.31 10.sup.7 3.48 10.sup.5 2.94 10.sup.4 MBT 4.5 CFU/g CFU/g CFU/g RDF CFU/g RDF RDF RDF RDF

[0215] Test 1

[0216] On average the total amount of bacteria was 3.510.sup.5 CFU/can lid, while the pathogenic indicator bacterial count was: Enterobacteriaceae count 5.1110.sup.2 CFU/can lid comprising about 1/700 of the entire live bacterial population and E. coli count 6.610.sup.0 CFU/can lid comprising about 1/5000 of the entire live bacterial population. Lactic acid bacterial count was 1.7810.sup.5 CFU//can lid and therefore comprised about of the entire live bacterial population in sorted metal samples of the method according to the present invention (FIG. 2). The amount of the indicator bacteria Enterobacteriaceae and E. coli were surprisingly low in the sorted metal treated according to the process of the invention.

[0217] Test 2

[0218] On average the total amount of bacteria was 2.2110.sup.7 CFU/can lid, while the pathogenic indicator bacterial count was: Enterobacteriaceae count 4.1010.sup.5 CFU/can lid comprising about 1/54 of the entire live bacterial population and E. coli count 2.110.sup.4 CFU/can lid comprising about 1/1000 of the entire live bacterial population. Lactic acid bacterial count was 1.2510.sup.5 CFU/can lid and therefore comprised about 1/175 of the entire live bacterial population in MBT sorted metal (FIG. 2). Thus, the amount of the indicator bacteria Enterobacteriaceae is about 4 times higher than lactic acid bacteria in MBT sorted metal.

[0219] Comparison of Test 1 and Test 2

[0220] The number of bacteria were compared between MBT sorted metal (Test 1) and sorted metal treated by the process of the invention (Test 2). In MBT sorted metal the total amount of bacteria was >60 times higher compared to sorted metal derived from the process of the invention (FIG. 2). When compared, the Enterobacteriaceae count of MBT sorted metal was >800 times higher than invention sorted metal and the E. coli count >1800 times higher in MBT sorted metal than in invention sorted metal (FIG. 2). Lastly, the lactic acid bacterial were similar between the MBT sorted metal and the invention sorted metal.

[0221] These findings suggest two things 1) Better growth conditions for bacteria, including pathogenic indicator bacteria (Enterobacteriaceae and E. cob), but excluding lactic acid bacteria in MBT sorted metal compared to invention sorted metal and 2) The conditions in the bioreactor using the method according to the invention creates a unique environment capable of annihilating pathogenic bacteria.

[0222] Test 3

[0223] On average the total amount of bacteria was 2.5910.sup.7 CFU/g RDF, while the pathogenic indicator bacterial count was: Enterobacteriaceae count 4.8810.sup.2 CFU/g RDF and E. coli count 0 CFU/g RDF. Lactic acid bacterial count was 3.3710.sup.6 CFU/g RDF and therefore comprised about 1/7 of the entire live bacterial population in invention sorted RDF (FIG. 3). The amount of pathogenic indicator bacterial group Enterobacteriaceae and E. coli were surprisingly low in the sorted invention RDF.

[0224] Test 4

[0225] On average the total amount of bacteria was 7.4610.sup.7 CFU/g RDF, while the pathogenic indicator bacterial count was: Enterobacteriaceae count 3.4810.sup.5 CFU/g RDF comprising about 1/138 of the entire live bacterial population and E. coli count 2.9410.sup.4 CFU/g RDF comprising about 1/1500 of the entire live bacterial population. Lactic acid bacterial count was 1.3110.sup.7 CFU/g RDF and therefore comprised about 1/7 of the entire live bacterial population in MBT sorted RDF (FIG. 3).

[0226] Comparison of Bacterial Counts in MBT Sorted RDF and RDF Obtained from the Process of the Invention

[0227] The number of bacteria were compared between MBT sorted RDF (test 3) and sorted RDF obtained from a process of the invention (test 4). In MBT sorted RDF total amount of bacteria was >2 times higher compared to sorted RDF obtained from a process of the invention (FIG. 3). When compared, the Enterobacteriaceae count of MBT sorted RDF was >700 times higher than sorted RDF obtained from a process of the invention and the E. coli count >29000 times higher in MBT sorted RDF than in sorted RDF obtained from a process of the invention (FIG. 3). Lastly, the lactic acid bacteria count was >3 times higher in MBT sorted RDF compared to sorted RDF obtained from a process of the invention. These findings suggest two things 1) Better growth conditions for bacteria, including pathogenic indicator bacteria (Enterobacteriaceae and E. coli) in MBT sorted RDF, compared to sorted RDF obtained from a process of the invention and 2) The conditions in the bioreactor using the method according to the invention creates a unique environment capable of annihilating pathogenic bacteria.

Example 2pH and Temperature Tests

[0228] In order to establish specific boundaries (ranges) in regard to pH and temperature in which pathogenic bacteria are exterminated in the method according to the process of the invention, experiments using model waste (model MSW) were carried out.

[0229] Model MSW was utilized to mimic MSW as described below.

[0230] Model MSW can be prepared in order to mimic the composition of real municipal solid waste. The below describes the composition of model MSW consisting of 3 fractions: [0231] 41% vegetable fraction (cf. Table 2) [0232] 13% protein/fat fraction (animal origin) (cf. Table 3) and [0233] 46% cellulosic fraction (cf. Table 4).

TABLE-US-00002 TABLE 2 Vegetable fraction of model MSW Composition of % of vegetable model MSW fraction (weight %) Onions 7.5 Carrots 7.5 Potatoes 6.3 Leeks 4.4 Salad 3.2 Frozen peas 4.4 Tomatoes 3.2 Cucumber 3.2 Red cabbage 3.2 Mushrooms 3.2 Oatmeal 3.2 Cornflakes 4.4 Apples, bananas, oranges, 4.4 lemons, pears Remoulade 3.2 Ketchup 3.2 Rye bread 6.3 White bread 9.5 Cake 3.2 Flowers 1 Coffee grounds 1 Boiled rice 3 Boiled pasta 3 Celery 3 Brussels sprout, kale 3.5 Beans, lentils 1 Broccoli 0.25 Cauliflower 0.25 Green beans 0.25 Pineapple 0.15

TABLE-US-00003 TABLE 3 Protein/fat fraction (animal origin) of model MSW Composition of % of protein/fat fraction model MSW (animal origin) (weight %) Roasted pork 6 Dog/cat food 6 Liver pat 5 Salami 5 Mortadella 5 Liver sausage 5 Ham 5 Rolled sausage 5 Hotwings 10 Spareribs 5.5 Fat of animal origin with spices 10 Cheese 4 Ymer (soured whole milk) 10 Eggs 3 Shrimps 3 Herring 5 Ground beef 1.5 Chicken whole 2 Chicken filet 4

TABLE-US-00004 TABLE 4 Cellulose fraction of model MSW Composition of % of cellulose fraction model MSW (weight %) Milk cartons 30.0 Newspapers 8.0 Magazines 2.8 Advertising materials 9.7 Phone books 0.7 Printing paper 2.2 Gift wrapping 6.2 Cardboard 9.8 Paper towel 22.5 Cotton pads 1.7 Wood 1.2 Textiles (dishtowels) 5.3

[0234] Fermentations were carried out under the conditions set out in Table 5.

TABLE-US-00005 TABLE 5 Experiment pH Temperature 1 6 50 2 4 20 3 4 50 4 6 20 5 5 35 6 5 35 7 5 35 8 6 20 9 4 20 10 4 50 11 6 50 12 6 25 13 5.5 30 14 6 35 15 5 25 16 4.5 25

[0235] Fermentations were performed in Sartorius 1 L equipped with mechanical stirrer, heating mantle, cooling mantle, cooling tower for exhaust gases and pH-meter. The temperature was varied (see table 5) using an electrical heating or cooling mantle and the stirring was 600 rpm. pH was adjusted to appropriate values by addition of 1M HCl or 1M NaOH through the Sartorius automated pumping system. The added components (solids and liquids) were not pre-heated prior to addition into the fermenter.

[0236] Fermentation of model MSW was carried out using 166 g model MSW, 1 L de-ionized water and 4 g Cellic CTec3 (Novozymes A/S). First water and model MSW was heated or cooled to appropriate temperature (see table 5) while stirring (300 rpm). Simultaneously, pH was adjusted to appropriate (see table 5) setting by addition of HCl or NaOH. Upon reaching the desired temperature and pH, Cellic Ctec3 was added (4 g) and the stirring increased to 600 rpm. This was followed by the addition of 1.3 ml Escherichia colt (strain DSM 498) in an approximate concentration of 810.sup.8 CFU/ml.

[0237] E. coli was grown overnight in nutrient broth at 37 C. shaking overnight prior to addition to fermenters. Furthermore, E. coli overnight culture, was centrifuged for 5 min, 5000 rpm and the pellet resuspend in 0,9% NaCl H.sub.2O to an OD.sub.600=1.

[0238] Sample Acquisition and Analysis

[0239] Samples of about 10 mL were withdrawn from the fermenters and the resulting Bioliquid was serial diluted using sterile 0.9% NaCl H.sub.2O to 10.sup.8. 1 ml from each dilution was plated on petrifilm plates. The bacterial count of the indicator bacteria Enterobacteriaceae and E. coli were measured according to Assays III and IV.

[0240] Indicator bacteria are counted in order to validate a specific environment for growth capabilities of pathogenic bacteria. The Enterobacteriaceae group (such as E. cols) are living in the mammal intestine as commensals, with the ability to become pathogenic. E. coli has been recognized as excellent indicator bacteria for decades. If these organisms are found to be present in an environment, this could indicate that pathogenic bacteria in general is capable of growth in that particular environment.

TABLE-US-00006 TABLE 6 Measured E. coli counts for various pH and temperatures Temper- CFU log.sub.10(CFU ature (24 h)/ (24 h)/ pH C. 0 Hours 24 Hours CFU (0 h) CFU (0 h)) 6 50 1.24E+06 8.40E+03 6.03E03 2.220 4 20 1.17E+06 0.00E+00 0 9.908* 4 50 1.57E+06 0.00E+00 0 9.959* 6 20 2.77E+06 1.63E+05 5.31E02 1.275 5 35 1.58E+06 4.60E+02 3.44E04 3.464 5 35 7.30E+05 3.50E+02 6.00E04 3.222 5 35 7.40E+05 1.30E+02 1.67E04 3.778 6 20 5.50E+05 3.40E+03 7.22E03 2.141 4 20 1.40E+06 8.00E+01 6.34E05 4.198 4 50 8.55E+05 0.00E+00 0 9.803* 6 50 1.29E+06 6.00E+02 3.16E04 3.501 6 25 1.38E+06 8.20E+03 5.91E03 2.228 5.5 30 1.60E+06 1.27E+04 7.37E03 2.133 6 35 1.41E+06 9.65E+05 6.53E01 0.185 5 25 1.35E+06 5.00E+03 3.83E03 2.417 4.5 25 1.25E+06 6.00E+01 5.73E05 4.242 *to apply the logarithmic transformation to the relative CFU counts, the values of 0 were replaced with 10.sup.4

[0241] The obtained experimental data was analysed in Design-Expert software, version 11 (Stat-Ease, Inc.). To model the obtained results the following transformations were applied to the data: [0242] 1. The ratio of CFU counts after 24 h and at the beginning of the experiment was calculated [0243] 2. If the ratio from point 1 equals to 0, the ratio was substituted with 10-4 to be able to apply a logarithmic transformation to all the ratios. [0244] 3. The negative logarithm with base 10 of the ratios was calculated. [0245] 4. To make the data more normally distributed, a power transformation with power of 0.59 was applied to the values from point 3. [0246] 5. The final model was built including the pH, temperature (T) and squared temperature (T.sup.2) terms. The model was shown to be significant (p<0.0001), pH (p<0.0001) and T.sup.2 (p=0.0341) terms were significant as well. T term (p=0.0635) was included because of the T.sup.2 term. The lack of fit was not significant (p=0.6876). R.sup.2 for the model is 0.84, predicted R.sup.2 is 0.695.

[0247] The predicted boundaries for non-pathogenic bacterial growth in regard to pH and temperature while running the method according to the invention are depicted in FIG. 4. The lines represent a 10 log relative reduction of E. coli by that temperature and pH. i.e. line 2 equals 10 log 2=100 relative E. coli CFU reduction. line 5 equals 10 log 5=100.000 relative E. coli CFU reduction and so forth. Thus. pathogenic E. coli are reduced by a 10 log 5 on the left side of line 5. Dots represent experiments carried out.

Example 3: Lab Scale Liquefaction of Model Waste without Previous Hygienization

[0248] A series of separate fermentations were carried out using 166 gram model MSW (prepared as described in Example 2), 1 Liter de-ionized water and either 2, 4, 6 or 8 gram of Cellic Ctec3 (purchased from Novozymes A/S) in which a fixed amount of inoculum, derived from Foulum biogas plant in Denmark, from the before-mentioned CSTR digester were added (166 gram). First water, inoculum (166 gram) and model MSW was heated to 50 C. while stirring (300 rpm) in a 5 L Sartorius fermenter. Upon reaching the desired temperature, enzyme (Cellic CTec3) was added (2, 4, 6 or 8 grams) and the stirring increased to 1200 rpm for 5 minutes and thereafter to 900 rpm for 1 hour. After 1 hour of stirring, the stirring was reduced to 600 rpm until the end of the experiment. The concentration of glucose, xylose, lactate, acetate and ethanol was measured at time points 18.25, 25.50, 42.50, 47.50 and 114 h after addition of enzyme by HPLC.

TABLE-US-00007 TABLE 7 Data obtained using 2 gram Cellic Ctec3 (all in g/L) Time (h) Glucose Xylose Lactate Acetate Ethanol pH 18.25 3.5 1.0 0.5 0.5 3.4 5.40 25.50 3.3 0.9 0.8 0.5 4.2 5.24 42.50 4.1 1.4 3.7 0.7 6.3 4.94 47.50 3.3 1.4 5.0 0.7 6.5 4.83 114 3.0 1.7 7.4 0.8 4.4 4.61

TABLE-US-00008 TABLE 8 Data obtained using 4 gram Cellic Ctec3 (all in g/L) Time (h) Glucose Xylose Lactate Acetate Ethanol pH 18.25 7.0 1.8 1.6 0.8 2.4 5.07 25.50 7.3 1.7 1.8 0.7 3.5 4.98 42.50 5.3 1.7 7.7 1.0 3.9 4.39 47.50 5.5 1.6 7.3 0.8 4.5 4.27 114 5.6 1.9 8.9 1.0 3.0 4.15

TABLE-US-00009 TABLE 9 Data obtained using 6 gram Cellic Ctec3 (all in g/L) Time (h) Glucose Xylose Lactate Acetate Ethanol pH 18.25 5.4 1.3 1.0 0.5 1.7 5.03 25.50 6.0 1.4 1.6 0.6 2.7 4.92 42.50 6.2 1.6 6.3 0.9 4.5 4.22 47.50 4.8 1.7 8.3 0.9 3.8 4.13 114 5.7 1.9 8.8 1.1 2.6 4.09

TABLE-US-00010 TABLE 10 Data obtained using 8 gram Cellic Ctec3 (all in g/L) Time (h) Glucose Xylose Lactate Acetate Ethanol pH 18.25 6.8 2.1 3.5 0.7 0.3 4.80 25.50 7.6 2.4 8.4 1.0 0.4 4.28 42.50 7.2 2.1 9.9 0.9 0.4 4.12 47.50 7.2 2.1 9.8 1.0 0.0 4.16 114 8.3 2.2 9.1 1.2 0.3 4.36

[0249] In all four experiments, model MSW was solubilized and glucose was released. The methanogenic bacteria from the inoculum resulted in a significant ethanol production in the experiment with low enzyme loading. Consequently, there was less glucose available for the lactic acid bacteria and the acidification was much slower with pH staying above 5 for about hours. When the enzyme dose was increased there was a gradually faster acidification and with the high enzyme dose (8 g) the pH dropped below 4.5 within 24 hours. This also effectively limits the production of ethanol and acetate to 0.3 and 1.2 g/L, respectively. These experiments show that hygienization of the reject water may be beneficial if the inherent lactic acid producing community in the waste is limited whereas hygienization of the reject water is not necessary if a sufficient large lactic acid community is present in the waste because the lactic acid bacteria is able to outcompete the inherent methanogenic bacteria present in the reject water.